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Equipment Discussions >> Refractors

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timps
sage


Reged: 02/24/13

Achro Vs Apo
      #5749040 - 03/22/13 04:14 AM

I was wondering if a large aperture long focus achro would give just as detailed planetary images as a smaller aperture apo. I had my first look through an apo the other night (tak TOA130). Yes the image was sharp, CA free and brighter than my 120mm Chinese achro, but the view didn't "blow me away" as I was expecting. The Tak obviously showed a little more detail and didn't require as much affort to see it but is that worth the $5,500 extra?
Could I match the detail shown in the TOA130 with a 152mm f12 - f15 Achro or maybe an 8" achro like Istar produce?


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orion69
scholastic sledgehammer


Reged: 05/09/10

Loc: Croatia
Re: Achro Vs Apo new [Re: timps]
      #5749044 - 03/22/13 04:29 AM

I'm only guessing here, but I would say that 8" Istar f12-f15 would visually blow away TOA130 for planetary (or any other 130mm APO).

Edited by orion69 (03/22/13 04:30 AM)


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Jon Isaacs
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Reged: 06/16/04

Loc: San Diego and Boulevard, CA
Re: Achro Vs Apo new [Re: orion69]
      #5749062 - 03/22/13 04:48 AM

Quote:

I'm only guessing here, but I would say that 8" Istar f12-f15 would visually blow away TOA130 for planetary (or any other 130mm APO).




What would "blow you away" is the scope that was somewhere between 8 and 10 feet long, the mount required to handle the scope and the wide range of eyepieces heights, and it would still only be an 8 inch scope.

Jon


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bherv
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Reged: 03/10/06

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Re: Achro Vs Apo new [Re: timps]
      #5749078 - 03/22/13 05:28 AM

A 12" f/5 Dob will show you more than any of those scopes and at a lower price.
Barry


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beanerds
sage


Reged: 07/15/08

Loc: Darwin Australia
Re: Achro Vs Apo new [Re: bherv]
      #5749153 - 03/22/13 07:40 AM

Good 'Q' Timps , all I can say is , is my 63mm f11.4 Zeiss telementor has worse CA than my 60mm f5.9 Takahashi FS60C .
so thats f11.4 vrs f5.9 .

840mm Zeiss achromat and 355mm Takahashi Fluorite .
Apo Vrs. ACHRO .

Personally I like the more natural colours of the moon and planets thru the Zeiss , more CA for sure .

The Tak FS60C APO is better , brighter views , smaller Aeire discs , easier to use , bla ,,,
But ...
The TakahashiFS60C is so good on everything , but she starts looking ,,, clinical ? where the Achro of the Zeiss is more natural , it aint just me seeing this .

Long throw Achromats for luna, planetary views are better .

Not an easy call , Achro's are more natural .
Brian.


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Jon Isaacs
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Reged: 06/16/04

Loc: San Diego and Boulevard, CA
Re: Achro Vs Apo new [Re: beanerds]
      #5749160 - 03/22/13 07:51 AM

Quote:

Not an easy call , Achro's are more natural .




In terms of rendering the spectrum of colors "naturally", accurately, Newtonians are the standard. In my admittedly limited experience, apo's are closer than achromats to the natural, accurate rendering of the Newtonian. If you like a little tint, there are a number of filters available.

Jon


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Jim Curry
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Reged: 10/29/07

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Re: Achro Vs Apo new [Re: timps]
      #5749200 - 03/22/13 08:32 AM

A 6" f/12 or f/15 Istar may not "blow away" the 130 but it will provide a far more satisfactory view which can only be appreciated after an evenings use. There is always the bogeyman of secondary color as an argument against the achro but do not be afraid. And no, I haven't looked through a 130. Aperture and a smooth polish to the achro will result in higher resolution. An 8" f/12 will be a complete hawg wrastle for portability.

The detractors of these long f ratio achros have short memories. Achros participated in pushing back the frontiers of astronomical science up to and including the present times. What have apo's contributed?

Jim


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orion69
scholastic sledgehammer


Reged: 05/09/10

Loc: Croatia
Re: Achro Vs Apo new [Re: beanerds]
      #5749215 - 03/22/13 08:46 AM

Quote:


Not an easy call , Achro's are more natural .





You are kidding, right?


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t.r.
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Reged: 02/14/08

Loc: Upstate NY
Re: Achro Vs Apo new [Re: Jim Curry]
      #5749225 - 03/22/13 08:54 AM

Here is what I was told by Barry Greiner of D&G Optical (a top US achromat manufacturer)which I think is a good rule of thumb and latter confirmed by my own field experiences...an achromat that is one inch larger than an apochromat will show as much planetary detail as the smaller BUT with chromatic aberration (CA,the purple blur) that may be bothersome to some people. This applies up to about 8 inches of aperture, where finally the CA becomes problematic in reasonable focal lengths. Filters reduce this CA to a level some can live with. Barry told me before the advent of the special "minus violet" filters, the filter choice was a simple color filter No.8 Light Yellow. I have one of these for my 80mm F/5 and it does indeed improve the view for high power planetary viewing adding another 50x that I can use productively.

What folks really get for their money when getting an apo is a very short, portable and fully corrected optic that can be used for better imaging and wonderful visual. A visual only user may indeed be completely happy with an achromat of short or long focus, simply depending on how much the chromatic aberration bothers them on a personal level that really can only be determined through experience! All the charts, reports and testimonials aren't going to be able to tell you if an achromat will work for you...ONLY YOUR EYES will determine that. If you weren't "blown away" by the TOA130 view compared to the chinese 120...it should tell you something! However, don't expect the same response from someone else looking through the same two scope you did!


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SteveSMS
super member


Reged: 03/29/08

Loc: Jersey Shore USA
Re: Achro Vs Apo new [Re: timps]
      #5749239 - 03/22/13 09:02 AM

I don't mean this to be offensive, but have you considered the size, weight, and cost of a mount capable of supporting a long focus 6" or 8" refractor? You owe it to yourself to find someone with a 8" or larger dob that is thermally managed and collimated that is willing to point it at Jupiter for you. My guess is that you will be "blown away."

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Mark Costello
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Re: Achro Vs Apo new [Re: Jon Isaacs]
      #5749255 - 03/22/13 09:17 AM

Quote:

Quote:

I'm only guessing here, but I would say that 8" Istar f12-f15 would visually blow away TOA130 for planetary (or any other 130mm APO).




What would "blow you away" is the scope that was somewhere between 8 and 10 feet long, the mount required to handle the scope and the wide range of eyepieces heights, and it would still only be an 8 inch scope.

Jon





I believe myself to be a refracto-fanatic but lookiing at these larger refractors like an 8" make me feel like . My 5" achro sets up easily enough but is about as large as I'd want a refractor to be. Any larger scope I get will work mostly or completely with mirrors.


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Jim Curry
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Reged: 10/29/07

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Re: Achro Vs Apo new [Re: SteveSMS]
      #5749259 - 03/22/13 09:19 AM

I use my 6" f/12 on a G11 with extension. It's fine for visual but I consider it at its limit. Adding another 18" to that OTA? I dunno...

Jim


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hottr6
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Reged: 06/28/09

Loc: 7,500', Magdalena Mtns, NM
Re: Achro Vs Apo new [Re: SteveSMS]
      #5749319 - 03/22/13 09:50 AM

Quote:

...have you considered the size, weight, and cost of a mount capable of supporting a long focus 6" or 8" refractor?



Anyone who has the funding to consider a TOA130 or an 8" achro will most likely have the funds for an appropriate mount, and if space is available, a small observatory. I don't see anyone that deep into the hobby who would consider an OTA as the only component of a system.

Otherwise, the question is purely rhetorical.


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dan_h
Carpal Tunnel


Reged: 12/10/07

Re: Achro Vs Apo new [Re: Jim Curry]
      #5749343 - 03/22/13 10:01 AM

Quote:

The detractors of these long f ratio achros have short memories. Achros participated in pushing back the frontiers of astronomical science up to and including the present times. What have apo's contributed?

Jim




Perhaps a good question to ponder but not a valid argument to assert the value of an achro over an apo.

Look what Columbus did with a small sailing ship. And almost all of the great railroads of the world were opened under steam locomotives. The heyday of radio came with the invention of the vacuum tube and televison was founded on old monochrome CRTs. There are many, many, many technolgies that have had their day and have now been relegated to the museums. The fact that these technologies were once the greatest tools available, doesn't make them the best today.

dan


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SteveSMS
super member


Reged: 03/29/08

Loc: Jersey Shore USA
Re: Achro Vs Apo new [Re: hottr6]
      #5749357 - 03/22/13 10:10 AM

Astronomy is not the only hobby that people don't have the "FULL" funding to enjoy. I don't doubt for one minute that there are OTAs out there that can't be used due to the owner not being able to afford a proper mount. It's the same as hobbies like boats or cars where folks bite off way more than they can actually chew and things just sit around unused or get sold for a loss.

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orion69
scholastic sledgehammer


Reged: 05/09/10

Loc: Croatia
Re: Achro Vs Apo new [Re: SteveSMS]
      #5749440 - 03/22/13 10:49 AM

OP question was not how heavy or large 8" achro refractor is, or what mount should one buy to support it.

Btw, I own 152mm achro and it's too big and too heavy for me and that's one reason I used it only few times (other is CA).

Edited by orion69 (03/22/13 10:51 AM)


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watcher
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Reged: 11/21/07

Loc: St. Louis, MO
Re: Achro Vs Apo new [Re: SteveSMS]
      #5749449 - 03/22/13 10:54 AM

Why is it that any time someone mouths the words "long focus refractor", the conversation degrades to the size and mount requirements, and why Dobs are a better choice,because their far less expensive, and why APO's are so superior because they're so much more expensive? I am just as happy with a long achro's views. There might be a minor discrepancy that allows a bit more to be seen with an APO of slightly smaller aperture, but well figured optics always delight. Whether it's a 60 or 100mm Carton, or a 6 or 8" D&G, Most will be happy with what a long achro can do in comparison to the similar aperture of ANY other type of scope. Want to talk about mounting issues or bang for the buck of aperture, let's do a thread about that if someone is asking about a decision to purchase, not for a discussion about performance.

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ValeryD
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Reged: 11/26/05

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Re: Achro Vs Apo new [Re: t.r.]
      #5749526 - 03/22/13 11:54 AM

Quote:

Here is what I was told by Barry Greiner of D&G Optical (a top US achromat manufacturer)which I think is a good rule of thumb and latter confirmed by my own field experiences...an achromat that is one inch larger than an apochromat will show as much planetary detail as the smaller BUT with chromatic aberration (CA,the purple blur) that may be bothersome to some people.




This may be true for 2" apo v 3" achro, for 3" and 4". But sure not for 6" and 7" and more so not for 7" vs 8".

My 5" excellent APO consistently showed more delicate details on Jupiter than 150mm F/10 achromat (ideally made, collimator from the test bench).


Valery.


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Jim Curry
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Reged: 10/29/07

Loc: STL
Re: Achro Vs Apo new [Re: dan_h]
      #5749527 - 03/22/13 11:54 AM Attachment (31 downloads)

Ahh Dan,

You didn't address my question. I never suggested an achro is THE cutting edge of anything only that they still contribute to science and my question suggests that apo's don't. Correct me if I'm wrong, but apo's are instruments solely in the hands of amatuer astronomers for visual and photo hobby (play)endevours. It was just a few years ago, 1980ish, that an antique 9" f/13 achro (deep in the allegedly no-no wasteland of purple haze ) was used to DISCOVER the rotation of Uranus wihin a percent or two as well as DISCOVER the phenomena of spokes in Saturns rings. To roughly quote O'Meara, "there was always a lot of blue around the images, but the resolution was incredibly sharp and contrast was very good." It only took a several billion dollar program to visit the scenes and confirm.

Clear skies,
Jim
(all in good fun)


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JKoelman
professor emeritus


Reged: 05/16/11

Loc: Bangalore, India
Re: Achro Vs Apo new [Re: Jim Curry]
      #5749655 - 03/22/13 01:04 PM

Quote:

I never suggested an achro is THE cutting edge of anything only that they still contribute to science and my question suggests that apo's don't.




Exoplanet hunter KELT-North sports a 71mm f/2.8 APO.


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Eddgie
Postmaster
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Reged: 02/01/06

Re: Achro Vs Apo new [Re: timps]
      #5749681 - 03/22/13 01:16 PM

Quote:

Could I match the detail shown in the TOA130 with a 152mm f12 - f15 Achro or maybe an 8" achro like Istar produce?




You were not blown away by a 5" APO? Then a 6" achromat is not going to blow you away either.

In fact, it is unlikely that even a 6" APO will "blow you away." The step up is subtle, even if it is to a 6" APO.

While not a Tak, I have owned 4", 5", and 6" APOs.

None of them would be my first choice for serious planetary observing.

Consider a 10" f/6 reflector with premium mirrors, Even this might not blow you away, but it will give a very meaningful improvement over where you are now.

Until refractors get rather large (8") it is hard to match the view you can get from a 10" or 12" reflector with high quality mirrors.

If better planetary views are what you seek and want to see a meaningful improvement, you won't get it with 6" f/15 achromat.

Go a lot bigger, or go home.

Edited by Eddgie (03/22/13 01:50 PM)


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TG
Pooh-Bah


Reged: 11/02/06

Loc: Latitude 47
Re: Achro Vs Apo new [Re: Eddgie]
      #5749819 - 03/22/13 02:12 PM

One thing that almost never gets mentioned for planetary observing is a tracking mount. Being able to relax and take in the details is essential to capturing those "blown away" moments. I've used a very smooth dob but tracking is a chore and limits you to about 250x. Now some people claim to track manually at powers far higher than that but not being most people I sometimes wish I could put my 6" Mak-Newt back on an EQ mount.

For this reason, I'd rather go with a large SCT (say a C9.25/C11/C14) which my mount can handle rather than a large newt which it can't and which would need a dedicated and probably pricey tracking platform.

Tanveer.


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Jim Curry
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Reged: 10/29/07

Loc: STL
Re: Achro Vs Apo new [Re: JKoelman]
      #5749920 - 03/22/13 03:07 PM

Bingo! I'm not surprised someone would correct me.

Thanks, Johannes


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Levine
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Reged: 03/24/06

Loc: 40° 47' 52" N / 85° 49' 14" ...
Re: Achro Vs Apo new [Re: timps]
      #5750020 - 03/22/13 03:55 PM

Hmmm...

One of my favorite instruments is my Cotosky 210mm f/6 Fraunhofer doublet.
It is "only" 48" long, but light enough to readily transport and mount. Better for deep-sky scanning, but when coupled with a minus-violet filter for the four objects in the known universe that will throw up some serious CA, the planetary images are not awful.
The FS-128 may be sharper overall, but the additional 3" of aperture offered by the Achro, in addition to the resulting brighter, larger image, provides some decent detail, too.


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Tank
Carpal Tunnel
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Reged: 07/27/09

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Re: Achro Vs Apo new [Re: Levine]
      #5750097 - 03/22/13 04:25 PM

I would take a smaller APO anyday over a larger Achro.
CA becomes intrusive and degrades the image in great seeing.
One reason that the 130 TOA didnt blow you away was most likely seeing conditions!!!
Actually to tell you the truth if the seeing conditions were bad the larger scope would even make the view more unpleasant and washed out!
Seeing conditions are most misunderstood you can have a AP178 and a 80APO in really poor seeing the smaller scope the image will be more pleasing!
Bottom line APOs are great instuments and i honestly say you cant compare a APO to a ACHRO!


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De Lorme
professor emeritus
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Reged: 12/30/08

Re: Achro Vs Apo new [Re: Tank]
      #5750325 - 03/22/13 06:11 PM

Levine, How well can you bring in gobular clusters with your
fast F/6 210mm? Thanks De Lorme


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Levine
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Reged: 03/24/06

Loc: 40° 47' 52" N / 85° 49' 14" ...
Re: Achro Vs Apo new [Re: De Lorme]
      #5750788 - 03/22/13 10:12 PM

Quote:

Levine, How well can you bring in gobular clusters with your
fast F/6 210mm? Thanks De Lorme




Just fine! Deep sky is where this instrument shines, and the views with an Ethos are, well, out of this world.


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azure1961p
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Reged: 01/17/09

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Re: Achro Vs Apo new [Re: orion69]
      #5750934 - 03/22/13 11:25 PM

Quote:

Quote:


Not an easy call , Achro's are more natural .





You are kidding, right?




I don't think so. What's interesting is that he attests it not his opinion alone with the apo showing a clinical view and the achromatic a more natural view. I'm curious to know what this natural impression consisted of. It's an interesting take. CA had to be seen but despite that a natural quality over the color free image was appreciated. I'd like to hear the details - if he's only respond. The notion is interesting and at no swipe to the apo.

Pete


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Lane
Post Laureate


Reged: 11/19/07

Loc: Frisco, Texas
Re: Achro Vs Apo new [Re: azure1961p]
      #5750969 - 03/22/13 11:54 PM

I don't know that a lot of detail is lost on a planet because of some CA being present. If the optics are of equal quality I would think that two scopes of the same diameter would perform almost the same. The problem is that not many manufacturers put as much effort into their Achro's as they do their APO's. They tend to not only correct the CA but correct other aberrations as well.

The telescopes that discovered most of the stuff we look at were well made Achro's.


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Scott BeithAdministrator
SRF
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Reged: 11/26/03

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Re: Achro Vs Apo new [Re: Lane]
      #5750973 - 03/22/13 11:59 PM

Quote:

I don't know that a lot of detail is lost on a planet because of some CA being present. If the optics are of equal quality I would think that two scopes of the same diameter would perform almost the same. The problem is that not many manufacturers put as much effort into their Achro's as they do their APO's. They tend to not only correct the CA but correct other aberrations as well.

The telescopes that discovered most of the stuff we look at were well made Achro's.




I thought the same thing before I did this review:

http://www.cloudynights.com/item.php?item_id=1804

It changed my opinion on achro vs. apo...


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Joe Bergeron
Vendor - Space Art


Reged: 11/10/03

Loc: Upstate NY
Re: Achro Vs Apo new [Re: Lane]
      #5751028 - 03/23/13 12:39 AM

Quote:


The telescopes that discovered most of the stuff we look at were well made Achro's.




That remark would be more meaningful if apochromats had existed when the low-hanging fruits of the universe were available to be discovered by eyeballs looking through refractors. It was hardly a competition between them.

I also point out that many of the really basic discoveries…moon craters, sunspots, rings of Saturn, moons of Jupiter, stars of the Milky Way, nebulae…were made with single-element refractors, long before those fancy-pants achromats came along. Shall we expect them to make a comeback?

It would be interesting to travel back in time and offer apochromats to Galileo, Cassini, Burnham, Admiral Smyth, and whoever, and see if they turn their noses up at them.


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DJCalma
member


Reged: 01/17/13

Loc: Northern California
Re: Achro Vs Apo new [Re: Joe Bergeron]
      #5751072 - 03/23/13 01:23 AM

Purple and black together are among the most beautiful color combinations there are. I prefer achromats and actually love the "false color." Maybe I should add an achromat to my signature to make this sound a bit more believable.

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JKoelman
professor emeritus


Reged: 05/16/11

Loc: Bangalore, India
Re: Achro Vs Apo new [Re: Lane]
      #5751075 - 03/23/13 01:28 AM

Quote:

If the optics are of equal quality I would think that two scopes of the same diameter would perform almost the same.



Indeed. The laws of physics dictate that provided the optics is diffraction-limited and sufficiently slow, it doesn't matter if you buy an apo, an achro or even a single element refractor: the same aperture renders the same detail. But the qualifier "sufficiently slow" is key. For an apo f/7 might be "sufficiently slow", for an achro you might need to go beyond f/30 and for a single element objective f/200 might be insufficient. And the practical consequences of ultra high focal ratios in terms of lacking wide field capabilities, highly demanding mounting requirements, and absence of decent ergonomics are obvious.


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De Lorme
professor emeritus
*****

Reged: 12/30/08

Re: Achro Vs Apo new [Re: JKoelman]
      #5751096 - 03/23/13 01:57 AM

Levine, I ran a search but I could not find anything on
Cotosky 210mm Fraunhofer lenes. Could you point me in the right direction. Thanks De Lorme


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Levine
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Reged: 03/24/06

Loc: 40° 47' 52" N / 85° 49' 14" ...
Re: Achro Vs Apo new [Re: De Lorme]
      #5751149 - 03/23/13 02:56 AM

CotoSky specialised in making large aperture achromats, but it looks like they are no longer in business. They were around as recently as 2009.
The unit I have was their prototype. Judging from it's performance, they must have carefully chosen the cell they put into it.


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orion69
scholastic sledgehammer


Reged: 05/09/10

Loc: Croatia
Re: Achro Vs Apo new [Re: azure1961p]
      #5751180 - 03/23/13 04:01 AM

Quote:

Quote:

Quote:


Not an easy call , Achro's are more natural .





You are kidding, right?




I don't think so. What's interesting is that he attests it not his opinion alone with the apo showing a clinical view and the achromatic a more natural view. I'm curious to know what this natural impression consisted of. It's an interesting take. CA had to be seen but despite that a natural quality over the color free image was appreciated. I'd like to hear the details - if he's only respond. The notion is interesting and at no swipe to the apo.

Pete



Quote:

Purple and black together are among the most beautiful color combinations there are. I prefer achromats and actually love the "false color." Maybe I should add an achromat to my signature to make this sound a bit more believable.




I guess it's personal preference. Actually not so strange because we all see (and feel) color differently. It's similar situation like two persons watching TV and one prefer picture with more saturated colors.
I must say people who like CA have advantage because they can have more aperture for less money.


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timps
sage


Reged: 02/24/13

Re: Achro Vs Apo new [Re: SteveSMS]
      #5751192 - 03/23/13 04:28 AM

But would't a Newtonian configured for planetary also have a long focal length? (F9 for ex.)

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Jim Curry
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Reged: 10/29/07

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Re: Achro Vs Apo new [Re: timps]
      #5751318 - 03/23/13 08:18 AM

tmb,
"The Tak obviously showed a little more detail and didn't require as much affort to see it but is that worth the $5,500 extra?"

Only you can answer that. Have you the cash laying around to chase that extra resolution? Go for it. Otherwise, prepare for a little compromise on the CA issue. And to repeat what was said, there is only a handfull of objects out of 10's of thousands that this is even an issue. If your concentration is on those objects then put your money into that chase.

Jim

Jim


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mblack
Throw me a bone here
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Reged: 10/31/05

Loc: Florida, USA.
Re: Achro Vs Apo new [Re: Jim Curry]
      #5751371 - 03/23/13 09:02 AM

Quote:

... Have you the cash laying around to chase that extra resolution? Go for it. Otherwise, prepare for a little compromise on the CA issue. And to repeat what was said, there is only a handfull of objects out of 10's of thousands that this is even an issue. If your concentration is on those objects then put your money into that chase.

Jim




Exactly. If you have the means to acquire and mount a large APO, go for it. For a visual setup, that's a big investment.


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CounterWeight
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Re: Achro Vs Apo new [Re: mblack]
      #5751509 - 03/23/13 10:35 AM

Have to agree, the refractor apo/achro 'bang per buck' quickly difts away from optics into finance and disposable income. Value is something negotiable on a market, optics is just optics. The apeture resolution and fl stuff pretty cut and dried. Planetary requirements also IMO pretty much the same. It's simple in ways.

My large (for me $ wise) 'apo' is only 160mm and I do remember some time ago someone here 'with acutual ep time' commenting he felt that at 7" on planetary refractors come into their own. Coming to refractors from larger mirrors I might agree. Even 160mm can leave you wanting if you have used larger mirrors under proper conditions.

But here introducing mirrors and 'folded optics' along with larger refractors more caveats come into play? Your typical LP, typical sky conditions and temp swings, comfort with collimating, and still mounting and tracking.

If you depart from the planetary requirement and 'ready kilowatt' aspect of these smaller refractors, and consider in broad brush the apeture advantage that 'for the price' larger mirrors bring to the table - especially the newer conicals and thinner composite, cooling/acclimation fan assist, that they can be bought or equipped to goto and or track - IMO the discussion is more "why a refractor at all". I know sometimes the contrast transfer functions and etc are cited (along with the crisp views) for the differing optics, but you need the resolution to begin with for it to matter - and that is what apeture brings to the table. A good reason for more than one scope?


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stanislas-jean
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Re: Achro Vs Apo new [Re: Jim Curry]
      #5751522 - 03/23/13 10:43 AM

Interested to have seen a picture of the clark refractor helping Mr O'Meara rotation of Uranus measure.
What I would say, the right refractor is the model which can help you to capture the banding system on Uranus.
We know lot of apos having not this ability with 6" size.
I had the 6" refractor, achro also, that make me with the possibility to.
They are reasons for this result. CA, except if very present, is not a concern on this subject, but the ability to keep images stable at the eyepiece with 375-400x and acurate is recgnised into a refractor design.
One way of the light in the tube is also very important with regards the air currents influence, the elevation of the objective is important for reducing the local seeing (coming from the ground). The design contributes to keep acurate and stable the images at the eyepiece.
The achros are not dead still.
Stanislas-Jean


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Re: Achro Vs Apo new [Re: Lane]
      #5751631 - 03/23/13 11:28 AM

Quote:

I don't know that a lot of detail is lost on a planet because of some CA being present.




Let me assure you that CA can be very damaging. For example, in large, fast acromats, CA can do more damage than a big central obstruction in an SCT.

Now the question becomes on what a "Lot" of detail would be. I one considers the loss of detail from a scope with a 33% obstrutction to be a "Lot", then one would have to say that for the fast achromat, a "lot" of detail is also being lost.

Now I personallly think the loss of detail from obstructions is quite a bit less than most people make it out to be, but it is what it is, and a 6" f/8 achromat is no better than a 6" SCT in this regard.


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Re: Achro Vs Apo new [Re: timps]
      #5751690 - 03/23/13 11:51 AM

I am laughing about the irony that is CN.

While this thread goes on, there is another thread about masking down a 6" f/8 achromat to 80mm. There seems to be some belief that the view might be prettier or better when using this scope as an 80mm achromat than when using it as a 6" f/8.

That makes me laugh so hard in the context of your post. Here we are on CN debating whether it is preferable to mask a 6" f/8 achromat to 3.25" for planets on one page, and on another page, someone wondering if a 6" f/10 scope would be better than their 5.25" APO! Ha. Funny to me! (maybe not to anyone else though).

That should answer your question about 6" f/10 becauase at f/10 you really haven't reduced CA enough that the green weighted poly-strehl is much more than diffraction limited (if that).

Even at f/15, the poly-strehl of an f/15 achromat is no better than you would get from a 6" reflector with a 20% obstruction, which is only going to have the contrast transfer of the aperture that you already have.

Why do people think large achrmats are so great? They talk about obstructions like they are the devil's work, but somehow think CA is a trivial abberation? Even at f/15, you are already falling behind a 6" f/8 20% obstructed reflector.

I don't get it. 6" achrmats are simply not great scopes from an absolute performance standpoint unless you make them f/18 or longer. An MN66 will be equal to it even at f/18.

At 6", and f/10, you would do almost as well with a C6.

Anyway, it is just funny to me. On one page the forum is talking about the benefits of masking down a 6" f/8 achromat to 80mm to improve planetary performacne (or at least make the view "more pleasing") and on another page, we are talking about trading the other way by going up an inch in aperture and accepting contrast lowering CA and some people thinking that it may be worth it!

Is it really just me?

Sorry. Sometimes we get so deafend by the clashes of tiny swords on CN that it is comical.

Dude, I have no interest in what you buy, and I hope you find happiness.

My own key to being a happy planetary observier only came wtih patience and lots of aperture.

But for others, it maybe it can be had using a 6" f/8 achomate masked down to 3.25 inches.

Don't look for us to guide you.

We are all going in to many different directions.


Edited by Eddgie (03/23/13 12:23 PM)


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mark8888
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Re: Achro Vs Apo new [Re: Eddgie]
      #5751748 - 03/23/13 12:12 PM

I love it, "deafened by the clashes of tiny swords". That's a great line.

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stanislas-jean
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Re: Achro Vs Apo new [Re: Eddgie]
      #5751782 - 03/23/13 12:28 PM

The poly strehl of a F15 6" achromat would involve a L/3 around aberration level. But this is concerning contrast levels matter not typically an optical acuracy.
Even with this kind of level I doubt that the 6" sct will be on a similar overall status and will show more.
The use of color filter will improve this average result for a significant gain.
What is researched is the detail access with regards to an aperture and observing in colour channels is not a bad idea.
Unless the esthetic images are only researched therefore for our money bag a simple reflector would be enough with its parallel inconveniences (air currents, acuracy need 2 times better, sensitivity to ground seeing).
What is highlighted is contrast level through posts but there is also resolution ability to accomplish.
If the resolution ability is present with a contrast level still enough to our own eyes we have the scope OK.
Stanislas-Jean


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Re: Achro Vs Apo new [Re: Eddgie]
      #5751907 - 03/23/13 01:30 PM

Quote:

I am laughing about the irony that is CN................Is it really just me?

Sorry. Sometimes we get so deafend by the clashes of tiny swords on CN that it is comical.

Dude, I have no interest in what you buy, and I hope you find happiness...............

We are all going in to many different directions.







Finally a post that makes sense!

dan


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Re: Achro Vs Apo new [Re: stanislas-jean]
      #5751920 - 03/23/13 01:35 PM

Quote:

The poly strehl of a F15 6" achromat would involve a L/3 around aberration level. But this is concerning contrast levels matter not typically an optical acuracy.
Even with this kind of level I doubt that the 6" sct will be on a similar overall status and will show more.




You may have misread what I said or didn't say. Nowhere did I say a 6" SCT would be the equal of a 6" f/15 achromat.

Here is what I said:

Quote:

At 6", and f/10, you would do almost as well with a C6.





I said a 6" 20% obstructed reflector would be about the equal to a 6" f/15 achromat, and I said that an MN66 would be about the equal of an f/18 6" achromat.

And I am the one on the other forum thread that said that reduceing a 6" f/8 scope to 3.25" by a mask would likely not really improve the absolute deatil ability, but that may not be the goal. The goal in that case could have been to get a more pleasing view.

I think though that the goal of the OP is to see more absolute detail and he is willing to do this even if there is some CA.

You can correct me if I am wrong of course, but in the case of even a 6" f/15 achromat, the poly-strel would likely limit it to about the same as his current 5.25" super APO.

And that means that my contention that the 6" f/15 achromat would not really blow him away would be correct because it would not even result in any improvement over where is at right now.

Certainly not enough to blow him away.

Edited by Eddgie (03/23/13 01:38 PM)


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stanislas-jean
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Re: Achro Vs Apo new [Re: Eddgie]
      #5752068 - 03/23/13 02:59 PM

We are on a certain relativity of facts.
Frankly the 6" sct will not blow the 6" achromat regarding the ability to capture very fine low contrasted details.
It's always matter of numbers characterised on the concerned optics.
The 6" sct will blow the refractor in blue channel
not in green and red channels especially with the use of coloured filter even wide,
the contrast level will be better in the 6" sct for coarse feature and the gain will go to be loosed for fine details.
For being more acurate.
Now apo will blow the achromat and the sct on coarse detail by the contrast level greater but for very fine details we will have to search the gain, sometimes not present.
This is well illustrated here on the sky for each design by visual mean.
The relative superiority of the long achromat stays on the fact that mostly the optic is located 2.5meters above ground.
This makes over a year observation period some gain on the seeing level at the eyepice, usually one step of danjon scale until 2 steps some nights and not so exceptionnal.
A step represents statiscally 20% gain or lost (the difference noted on FTM curves respectively). All of these for visual.
Stanislas-Jean


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Re: Achro Vs Apo new [Re: orion69]
      #5752368 - 03/23/13 05:49 PM

My Zeiss gives a more natural hue to oblects compared withg my Takahashi , I seen the same thing when using my ( now sold ) 127mm f7.5 NG triplet and my now owned 127mm f8 Istar achro .
True there is CA but in my eyes the very well corrected Achromats ( Zeiss and Istar ) give a more natural view especially Luna and Jupiter .
Might be my eyes aint what they used to be ? but I am not kidding .
Brian.
Quote:

Quote:


Not an easy call , Achro's are more natural .





You are kidding, right?




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beanerds
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Re: Achro Vs Apo new [Re: azure1961p]
      #5752437 - 03/23/13 06:24 PM

Hi Peter , its a very hard thing to get across in words but I have had both my Zeiss and Takahashi out side by side many times for comparo's using my Zeiss orthos in both to get the same ( well close ) magnifications .
But every time the Zeiss gives a better view , perhaps more natural is the wrong term but it just looks nicer in the achro and you have to realise that the CA in the Zeiss is almost invisable under normal use .
I am not the only one to see this in my 2 scopes many friends see it as well , but without the ambigious side by side comparo , it will not be seen I think .
Sure the Tak is smaller , lighter and way easier to set up but to me the views are more like a laboratory experiment , so clean and sterile it looks unreal ? very hard to describe .

See my last answer here and I mention the same thing was seen using my now sold 127mm NG Apo and my 127mm Istar achromat , the apo was better for sure but not as the price differance dictates , hence I sold the apo and am now very happy with my Istar achromat .
CA does not bother me and I beileve every one's different in their tollerance , you just got to find yours .

I also have a gineric 150mm f8 Saxon ( Synta ) achro in NZ that my Nephew is using while I am here in Australia working ,with a correctly fitted 'Aries Chromocor' and that scope is as good visually up to 300x ( after that the AP struts its stuff with ease ! ) as a friends 152mm f8 AP apo , is the AP worth 10x as much as my Synta ? we regularly did side by side comparos but thats another story .

Diffiuclt to explain , and we wont mention that not everyone has multy $1000's to spend on their hobby .
Brian..
Quote:

Quote:

Quote:


Not an easy call , Achro's are more natural .





You are kidding, right?




I don't think so. What's interesting is that he attests it not his opinion alone with the apo showing a clinical view and the achromatic a more natural view. I'm curious to know what this natural impression consisted of. It's an interesting take. CA had to be seen but despite that a natural quality over the color free image was appreciated. I'd like to hear the details - if he's only respond. The notion is interesting and at no swipe to the apo.

Pete




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Re: Achro Vs Apo new [Re: stanislas-jean]
      #5752499 - 03/23/13 07:10 PM

I have a size limit on refractors of 4". There ARE one or two scopes I would violate this limit for but, they are both apos. Maybe the vixen NA140. Anyway, sidetracked again. Long achros are not for me. The well made ones cost more than a newt two to 3 times their size, in some cases and the newt will blind you with so much brightness and detail on planets. By the time you mount that long achro, you could have a nice Zambuto powered dob giving you fine beautiful planetary detail. The dob would be easier to set up and therefore would be used more often.
I love these threads. They show how people love their telescopes. The long achro lovers defend theirs, apos lovers do the same. Newt guys add their two cents and everyone brings up the flaws of the others. People get mad thread gets locked. Then one month later, it starts again.

I read them every time. The right answer is... Try them all at star parties. Then buy the one you like. You may not see CA as easily as someone else or you may not care. It may drive you nuts like it does to me. Don't forget to try a dob. My z8 did really well on planets. My Z12 is better but, you need to use a filter or you will lose your night vision.


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Re: Achro Vs Apo new [Re: timps]
      #5752523 - 03/23/13 07:22 PM

Hi Timps,

I have an 8" f7 Newt with truly exceptional optics and it is stunning on planetary. The real keys, imho, are collimation and thermal management. I use the fan set up that Alan Dyer wrote about in S&T years ago and it is killer. It constantly scrubs the boundary layer in front of the primary. I love refractors too, I own 5 from 80mm to 150mm but the 8 " Newt and this new EdgeHD 8 are far superior to 120ED when it comes to planets. I do believe that an 8" APO would be mind blowing but I cannot even dream about something that expensive. Even an 8" achro with a Chromacorr would be way too much for me as I have no way to set it up permanently. Huge mounts are just too much of a hassle for my observing style.

Clear Skies,

Steve


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Re: Achro Vs Apo new [Re: Joe Bergeron]
      #5752539 - 03/23/13 07:35 PM

Yeah, who needs automobiles and airplanes? The whole world was explored with sailing ships, from horseback, on foot and by canoe!



Regards,

Jim


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Jon Isaacs
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Re: Achro Vs Apo new [Re: timps]
      #5752676 - 03/23/13 08:48 PM

Quote:

But would't a Newtonian configured for planetary also have a long focal length? (F9 for ex.)




Why?

Aperture and optical quality are the important factors. With a fast Newtonian using a driven mount, coma is not an issue, without a driven mount coma correctors do the job. Essentially perfect mirrors are available at focal ratios under f/4.

When comparing apos and achros, it comes down to all around performance and practical issues. It is possible to build an achromat that offers planetary views that are similar to an apo. It's is also possible to build and achromat that is as compact and offers the same wide true field of view as the same apo. But those two achromarts are very different scopes.

If one likes purple, go with a singlet...

Jon


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Re: Achro Vs Apo new [Re: beanerds]
      #5752716 - 03/23/13 09:04 PM

Quote:

My Zeiss gives a more natural hue to oblects compared withg my Takahashi




I asked this once, I will ask it one more time. How does the achromat compare to a Newtonian in terms of "naturalness" of color?

If you are using the achromat to filter/tint the colors, I guess that is fine I don't see that as being more natural if natural means an accurate representation of the actual image.

I am like the other poster who believes refractors are best 4 inches and under. Refractors get better as they get smaller, reflectors get better as their aperture increases. Color correction in a 30 mm f/5 is pretty good... There's not much anyone can do to correct the color in 10 inch f/5 refractor..

Jon

I am like


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beanerds
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Re: Achro Vs Apo new [Re: Jon Isaacs]
      #5752937 - 03/23/13 11:05 PM Attachment (39 downloads)

Its all in the eyes of the beholder Jon .
If you want a planet buster its gotta be a long throw Refractor or Newt or MAK or CAT or.....
The quality of the optics , columination etc mean everything when trying to glean the smallest planetry details , as I guess you already know this ?

When it comes to a planet buster my home made ( by me ) 10 inch f10 newt in this photo is the cat's whiskers .
Its the alloy tube with the oblong cut outs and in 2 pieces is very hard to beat . It has 3 large clips to join it togrther .
These optics have been thru many incarnations over the years from a 500lb concrete EQ monster on wheels to its much more user friendly Dob mount of today .
Its out in only 3 trips and acclimitizes fast with the open tube .
Its secondary is 22mm in dia so its almost an unobstructed 10 inch f10 , and it shows jupiter as good as any scope I have ever looked thru .

I think I am qualified enough to claim that my little 63mm Zeiss f11.4 gives a more natural Luna/planetary view .

Note my 150mm 'Chromocored' Saxon ( Synta ) in this photo and the Gold truss tube EQ mounted Newt ( 125mm f17 ) another great scope I made , she has a 3/4 inch secondary , tiny .

One more thing look at my signiture and see I also have a Takahashi M210 , SKY90 and Istar 127mm f8 Achro .So yes I say the Zeiss achro gives a more natural hue to my eyes .

As you can see I like telescopes , but all I am trying to get across is that a very well made Achromat will perform very , very well and my Zeiss is just that . One of the best ever made .

ps.the 10 and 5 inch newts and the 150mm refractor and ED80 in this photo are at my sister's in NZ and get use by my Nephew there , the rest are here with me in Australia.
Enjoy .
Brian.


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Re: Achro Vs Apo new [Re: beanerds]
      #5753136 - 03/24/13 01:45 AM

Quote:

Its all in the eyes of the beholder Jon . If you want a planetbusteritsgottabea long throw Refractor or Newt or MAK or CAT or..... The quality of the optics , columinationetcmeaneverything when trying to glean the smallest planetry details , as I guess you already know this ?





What I do know is that the most important factor in getting the good planetary views is the seeing... Great optics are not much use unless the atmosphere is stable enough to let the optics do their stuff.

Regarding the "naturalness of the color". As I see it, in this context, natural means the most like nature. Jupiter is part of the natural world. So, since a Newtonian has the most perfect color transfer, then it seems with q Newtonian to compare the Zeiss and Tak to, you would be in the position to make that call.

In my experience, apos more closely render colors than long focus achromats. I do like the views through my 60mm x800 Asahi-Pentax but truthfully, at the small exit pupils I use for viewing the planets with that scope, colors are dimished in comparison to a Newtonian, the eye sees more color in brighter images.

Jon


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buddyjesus
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Re: Achro Vs Apo new [Re: Jon Isaacs]
      #5753181 - 03/24/13 02:21 AM

try each kind at a star party along with filters if anyone has them lying about. I recommend a #8 light yellow to reduce chromatic aberration. We are all crazy, just crazy in different ways.

My uncle was an aperture rules guy and recommended I get a big reflector. I used a small reflector(all budget would allow) for a few years and didn't like it for optical reasons. I traded up in aperture and quality by getting a medium length 4" achromat.

Why not the other kinds? Can't afford an apo, don't like the image shift when focusing cassagrains, and can't observe standing up if I got a large dob. I also have a soft spot for GEM mounts. At the end of the day, I knew I would be happier with an achromat and that guided my purchase. I love the looks of the long achromats.

So ask yourself, what would make you happiest? Can always change your mind later, but til then live YOUR current dream.


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Re: Achro Vs Apo new [Re: timps]
      #5753389 - 03/24/13 08:37 AM

Quote:

The Tak obviously showed a little more detail and didn't require as much affort to see it but is that worth the $5,500 extra?





Basically, very basically, if you can afford it and want it, it IS worth the extra money.

If you can't, you make a statement about how big of a dob you can get for less money.


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stanislas-jean
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Re: Achro Vs Apo new [Re: Sean Puett]
      #5753851 - 03/24/13 12:30 PM

Frankly it is not matter to be lover in apo achro reflector.
Just do tests and compare them on situations, obviously actual.
Reason why I found the long achro interresting in use with more.
I have also a 305 which is used deeply only 2 or 3 nights a year. Never more sothat a 6" stays always very profitable when the seeing (tube and local) is minimised.
Think global not on paper only, with a money bag for getting usually the more details we can.
Stanislas-Jean


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Re: Achro Vs Apo new [Re: stanislas-jean]
      #5754507 - 03/24/13 05:18 PM

Quote:

Just do tests and compare them on situations, obviously actual.
Reason why I found the long achro interresting in use with more.




There is on thing about a long achro... it is long, that is one thing I have discovered in comparing achromats to apos. An 80mm F/15 achromat might provide similar planetary views to a 80mm F/7 apochromat but one is handy and easy to use, the other is by comparison, unwieldy.

Jon


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Eddgie
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Re: Achro Vs Apo new [Re: stanislas-jean]
      #5754748 - 03/24/13 07:02 PM

Once again, I did not say that that a 6" SCT would blow away a 6" achromat in any way shape or form..

Why do you insist on putting words in my mouth?

I said that by the time you factor in the damage done by CA in a 6" f/10 achromat, you won't be doing that much better than you would with a C6. This is soooooo much diffent than what you are implying that I said.

Quote:

At 6", and f/10, you would do almost as well with a C6.





That sir, is a very far stretch from saying that I said a 6" SCT would "Blow away" a 6" f/10 achromat.

Never thought it, never said it, and won't defend something I did not say. I can only defend what I do say and I said that you would not be all that much better off with a 6" f/10 achroamt than with a 6" SCT.


Please please please address things I said and not debate things I didn't say.

I can't defend myself if you change what I said. My tiny sword would be getting needlessly all chipped up.

Edited by Eddgie (03/24/13 07:10 PM)


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Re: Achro Vs Apo new [Re: stanislas-jean]
      #5754787 - 03/24/13 07:28 PM

Quote:

Frankly it is not matter to be lover in apo achro reflector.
Just do tests and compare them on situations, obviously actual.
Reason why I found the long achro interresting in use with more.
I have also a 305 which is used deeply only 2 or 3 nights a year. Never more sothat a 6" stays always very profitable when the seeing (tube and local) is minimised.
Think global not on paper only, with a money bag for getting usually the more details we can.
Stanislas-Jean



That was the point of saying to try all the different types of scopes and then choosing what YOU like. It really makes no difference to a long achro lover that I think a short apo is better or a large newt is best. My opinion affects what I buy only. We all explain our reasons for choosing certain designs over others but, the only thing that ultimately matters is YOUR opinion when you decide what to buy.
To me talking about long big achros without mentioning the mount requirements is setting someone up for disappointment. Just like talking about dobs without mentioning mirror care and collimation and sometimes paracorr requirements is not acceptable to me. I also mention the need for higher priced eyepieces in fast dobs because that is another potentially bad surprise.
Try before you buy.


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buddyjesus
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Re: Achro Vs Apo new [Re: Sean Puett]
      #5755027 - 03/24/13 09:37 PM

has anyone said aperture rules yet and to get a dob instead? haha

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KWB
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Re: Achro Vs Apo new [Re: buddyjesus]
      #5755162 - 03/24/13 10:58 PM

Quote:

has anyone said aperture rules yet and to get a dob instead? haha



I've got a good idea,let's don't,and then say we did.

Let's just stay on topic and please,let us all keep the personalities out of this excellent thread. Difference of opinion makes the world go round when done in a respectful manner.


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Jeff B
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Re: Achro Vs Apo new [Re: buddyjesus]
      #5755252 - 03/24/13 11:54 PM

Quote:

has anyone said aperture rules yet and to get a dob instead? haha




Yup, third post after the OP's first. Never fails.


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De Lorme
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Re: Achro Vs Apo new [Re: KWB]
      #5755256 - 03/24/13 11:57 PM

That's right Sean. They all have weakness. But which of them have fewer? When I look in the classifieds I see a lot of big dobs a few small apo's and a fewer still large{8"}achros.Why is this? Because over a period of time,as we grow older,body starts to give way, CONVIENCE really becomes reality. A 8" achro will allow you to sit,take you as far as a 14" dob,with no collimation issues and no waiting time for it to cool down. This why D&G,Istar are still in buisness.
There are good scopes below 14"dobs &8"refractors but they
can only take you to 10-12 Mag. This is Part of the learning curve. By the time people can afford
what ever they want people know the convience factor.
They buy large refractors and put them in a rool off roof.
This is my goal to. Right now I have a CR6" on a CGEM in a rool off roof. Hoping to put a 8"f/9 on a CGEM-DX but
mabey a 8"f/6 the CGEM. De Lorme


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jrbarnett
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Re: Achro Vs Apo new [Re: hottr6]
      #5755270 - 03/25/13 12:07 AM

That's just it. I have an inkling that one thing that keeps truly large refractors (whether labeled "achromat" or "apochromat") from being more popular is the mounting requirement. Even if you could get a truly large refractor for a low price (i.e., a 7" for $2500), you won't be putting such a scope on a $1500 mount. Mounts capable of carrying such a payload are in the $5000 range to start.

Regards,

Jim


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jrbarnett
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Re: Achro Vs Apo new [Re: orion69]
      #5755273 - 03/25/13 12:09 AM

I'd say that it largely depends of the figure quality of the Istar. A 1/3 wave 10" refractor wouldn't be blowing away a top quality 4-incher much less a TOA on planets.

- Jim


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galaxyman
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Re: Achro Vs Apo new [Re: Eddgie]
      #5755334 - 03/25/13 12:52 AM

Quote:



Why do people think large achrmats are so great?







Well maybe because they have actually had great views with them? Unless you think they are all full of it?

I don't mask any of my achros (don't need to with my observing). Have you actually seen through say a 6", 7" or even a 8" achro of high quality in the DSO realm?

I've seen many DSO views side by side of equal or close to equal aperture of various types of scopes, including a 6" quality achro and 6" APO. The views were very close in the APO's favor as it should.

I've seen a 7.1" high quality achro next to a 6" f/9 APO, and the achro was most definitely the superior DSO scope.

What I have seen in many of of these larger achros is no doubt variable optical quality of fair to quite good, but also the collimation way off, and in some cases really bad.

Don't get me wrong I'll take your 6" APO over my 6" achro in a heart beat (not the 8" though ), but I've seen these 6" achros go very deep per it's aperture in DSO observing.


Karl
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Chesmont Astronomical Society - www.chesmontastro.org
Galaxy Log - http://www.youtube.com/user/GalaxyLog4565?feature=mhee
Galaxy Log Blog - http://galaxylog.blogspot.com/
HASB - http://www.haveastellarbirthday.com
Telekit (Swayze optics) 22" F/4.5 Dob
Homemade (Parks Optics) 12.5" F/4.8 Dob
TMB/APM 8" f/9 Refractor”The Beast”. One great DEEP SKY achro
ES 6" f/6.5 achro. Good one
Celestron Omni XLT 102 refractor.
Celestron 10x60mm Binos


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Sean Puett
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Re: Achro Vs Apo new [Re: De Lorme]
      #5755340 - 03/25/13 01:00 AM

Quote:

That's right Sean. They all have weakness. But which of them have fewer? When I look in the classifieds I see a lot of big dobs a few small apo's and a fewer still large{8"}achros.Why is this? Because over a period of time,as we grow older,body starts to give way, CONVIENCE really becomes reality. A 8" achro will allow you to sit,take you as far as a 14" dob,with no collimation issues and no waiting time for it to cool down. This why D&G,Istar are still in buisness.
There are good scopes below 14"dobs &8"refractors but they
can only take you to 10-12 Mag. This is Part of the learning curve. By the time people can afford
what ever they want people know the convience factor.
They buy large refractors and put them in a rool off roof.
This is my goal to. Right now I have a CR6" on a CGEM in a rool off roof. Hoping to put a 8"f/9 on a CGEM-DX but
mabey a 8"f/6 the CGEM. De Lorme



See what you just posted proves my point. I have no desire to have a stationary observatory. You do. That is great. It is opinion and nothing more. I would rather have an np127 than an 8" f6 achro. Is that good or bad? No it just is. I would still enjoy looking through your scope but, I would prefer something else. It shouldn't matter that I prefer a smaller apo, right? My refractor doesn't have perfect color correction but, it is good enough for me. I can coax out false color by using high mag on Jupiter and especially Venus. Someone at a star party actually said he could see false color at 19x mag on dim stars. I just let him make his statement laughed to myself later and went on. Maybe he has super eyes, it doesn't mean my scope is any less to me.

There are normally 3x as many refractors on the used market as newts. This site may be different since the ads never expire but, if you check Astromart at nearly any time there will be 55-70 refractors for sale and 20-30 newts.
Jim is spot on with the mount requirements being an issue for large achro sales. If you have to spend 5000 on a mount, why not buy an apo? You could get a used FS152 flourite doublet for that amount or a bit more. Or a TEC 140.


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timps
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Re: Achro Vs Apo new [Re: Sean Puett]
      #5755366 - 03/25/13 01:20 AM

Maybe I should go down the Newtonian reflector path?
Long FL with high quality optics and it would be on par with a large aperture Apo for a fraction of the cost.


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De Lorme
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Re: Achro Vs Apo new [Re: Sean Puett]
      #5755385 - 03/25/13 01:39 AM

Sean, in theory I agree with you it does not matter. But
Convience is not a theory. When you have rool off roof
it's just so much easier. No wasted time. No limitations
on which scope to buy or set up. I've seen mabey 2 large refractors {8"}and 1 8" lens up for sale in the last 5 years. I look every day.D&G and Istar are still in buisness.
Karl, I'm thinking a 8"F/6 would ride fine on my CGEM.
1.Tub weights 10.75lbs. ,2. lens 10.25klbs. 4.rings weight aprox. 10lbs 4. lenght is no longer than a AT 10" reflector{which rode well on top of my CGEM} and smaller in diameter.
I"ve never looked through a 8" so being an fast f/6 would I be able to use enough power to bring in and thus resolve
gobular clusters? What do you think? De Lorme


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stanislas-jean
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Re: Achro Vs Apo new [Re: Sean Puett]
      #5755461 - 03/25/13 02:57 AM

After a comparison on long term placed on a site, mine, I found the long achro getting the best efficiency over a year.
Not matter of love, an OTA is just a tool.
Stanislas-Jean


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mark8888
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Re: Achro Vs Apo new [Re: stanislas-jean]
      #5755482 - 03/25/13 03:58 AM

Quote:

Maybe I should go down the Newtonian reflector path?
Long FL with high quality optics and it would be on par with a large aperture Apo for a fraction of the cost.




Not to derail this thread at all, but responding to the following quote above: "on par with a large aperture Apo". I am wondering the same thing, as I read this thread and the other recent interesting thread concerned with large refractors... speaking about visual only, in moderate to very good seeing, is there any advantage in getting a large APO as opposed to a reflector (of any size)? A large APO, say 7 inches and above, costs in the neighborhood of 20K+ , plus the sizable mount as has been remarked above in the thread. High quality reflectors of greater/much greater aperture cost significantly less. Yet many people buy the large APOs and profess to be visual only. Why? It has often been said that if you get a high quality reflector of a couple of inches or more greater than the size of an APO refractor, all the visual advantages of the refractor disappear vs. the reflector, and thus there is no point in getting the large refractor for visual (besides the wider field). In people's experience here, is that true, or is there something else special about the view through a 175mm + refractor that makes it unique? Why might one prefer the view through the large high quality APO refractor as opposed to a larger, much cheaper high quality reflector?


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beanerds
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Re: Achro Vs Apo new [Re: Jon Isaacs]
      #5755498 - 03/25/13 04:37 AM

Yep Jon I did mention that a few posts back , ' The Takahashi is way easier to drag out in one hand , tripod and all , plonk down and observe .
Nothing better , or easier , and in that respect it does get used the most out of all my scopes . .
Shes a little sweety .
Brian.
Quote:

Quote:

Just do tests and compare them on situations, obviously actual.
Reason why I found the long achro interresting in use with more.




There is on thing about a long achro... it is long, that is one thing I have discovered in comparing achromats to apos. An 80mm F/15 achromat might provide similar planetary views to a 80mm F/7 apochromat but one is handy and easy to use, the other is by comparison, unwieldy.

Jon




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De Lorme
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Re: Achro Vs Apo new [Re: mark8888]
      #5755507 - 03/25/13 04:50 AM

Because it's not primarily about just the view. Comfort and
ease of use are equally as important. A 8" F/8.8 achro refractor lens from Istar is about $1700. I would say a 16"
reflector mirror would be about a 1/3 more. The aproximate
total weight on putting a 8"F/6 on my CGEM is around 32lbs
with a length of 48" for about $2500. How much does a goto
trackimg system for a large reflector cost. About the same
or a little more than a CGEM-DX. But which one is more difficult to use. The reflector.
Reflectors you have to collimate accurately.
You have to install fans to get them to ambeint tempertures
You have to wait until cooled.
You have to stand on a stool or ladder to view.
Have to buy a coma corrector
Eyepieces cost considerably more
Large refractors take a lot more time to set up
Refractors have none of these problems.
One thing I will say though with Orion making large goto dobs cheaper than a large refractor that might make a differance initially. But I believe in the long run the extra cost to be able to sit and not have the other issues
will be worth it. People really do not consider convience
until they experience not having it. De Lorme


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beanerds
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Re: Achro Vs Apo new [Re: timps]
      #5755517 - 03/25/13 05:03 AM

Yes you can Timps , and it's has has been said here a reflector is the bast 'Bang for Buck' out there . True words .

But you have to realise that any Newtonion no matter how good it is requires constant maintance to keep it at its best ,thats been mentioned here as well .
But here is the crux !!! ,,
At midnight would you rather be at least 1.5 meter's off the groung on a ladder or stool looking at say , Jupiter with an awsome 8-10 inch f9-10 newt ? they need to be at least this long (f9-10) to keep the secondary as small as possible to keep the 'Contrast of the view' at its best , or ,,,,,
Comfortably seated on an observing chair looking at jupiter in even a lowely 6-8 inch f8-10 Achromat refractor ?

My aswome 10 inch f10 has a 2500mm focal length and when observing the zenith ( where the best seeing is ) I am nearly 2 metre's up to see thru the eyepiece .
Some people are uncomfortable with that at night .

Just a reminder that , that it can be a problem showing , say your Mum or other person jupiter at 10 pm ?.
Brian.
Quote:

Maybe I should go down the Newtonian reflector path?
Long FL with high quality optics and it would be on par with a large aperture Apo for a fraction of the cost.




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timps
sage


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Re: Achro Vs Apo new [Re: beanerds]
      #5755535 - 03/25/13 05:50 AM

Deffinately food for thought.

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t.r.
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Re: Achro Vs Apo new [Re: timps]
      #5755649 - 03/25/13 08:19 AM

Quote:

In people's experience here, is that true, or is there something else special about the view through a 175mm + refractor that makes it unique? Why might one prefer the view through the large high quality APO refractor as opposed to a larger, much cheaper high quality reflector?



CONTRAST for its given aperture.


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Sean Puett
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Re: Achro Vs Apo new [Re: timps]
      #5755659 - 03/25/13 08:28 AM

Quote:

Maybe I should go down the Newtonian reflector path?
Long FL with high quality optics and it would be on par with a large aperture Apo for a fraction of the cost.




I am not trying to convince you to buy a newtonian. That is where my big aperture money goes. What I think you should do is go to a star party or astronomy club and try them all before deciding. I get great planetary views with my dob. One of the local CNers has a Webster d14 and Jupiter is amazing through that scope. The d series scopes have Zambuto mirrors.
Try as many scopes as possible so you don't judge a poorly collimated scope of the type you may prefer. I like having the ability to collimate my own scopes so that may be something to ask about when you are trying these out. This "what type of telescope should I buy?" type thread are really only so helpful because you may have far different ideas of what a "great view" or "planetary detail" means. How many times have you read something like, "my new 4-5" apo blew away a 12"+ newtonian." my mass produced newtonian shows the bands on Jupiter as very dark and detailed, when I have good skies. My 4" refractor (which is admittedly not a planetary scope) shows that Jupiter is round and shows the two large belts but not as detailed.
The point of this is just for you to be careful how much stock you put in the opinions expressed here and on other websites. If you can't try the different scopes before you buy, try buying used. Then if it doesn't live up to expectations, you may only be out the shipping costs. Although it is very possible to find deals where you pay far less than a scope is worth. You have time to do research and get the right scope so take your time and you will end up much happier with the results.


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buddyjesus
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Re: Achro Vs Apo new [Re: t.r.]
      #5755671 - 03/25/13 08:40 AM

cooling times is the big difference besides resolution. Refractors and reflectors both complement each other nicely.

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galaxyman
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Re: Achro Vs Apo new [Re: De Lorme]
      #5755725 - 03/25/13 09:37 AM

Quote:

Sean, in theory I agree with you it does not matter. But
Convience is not a theory. When you have rool off roof
it's just so much easier. No wasted time. No limitations
on which scope to buy or set up. I've seen mabey 2 large refractors {8"}and 1 8" lens up for sale in the last 5 years. I look every day.D&G and Istar are still in buisness.
Karl, I'm thinking a 8"F/6 would ride fine on my CGEM.
1.Tub weights 10.75lbs. ,2. lens 10.25klbs. 4.rings weight aprox. 10lbs 4. lenght is no longer than a AT 10" reflector{which rode well on top of my CGEM} and smaller in diameter.
I"ve never looked through a 8" so being an fast f/6 would I be able to use enough power to bring in and thus resolve
gobular clusters? What do you think? De Lorme




Yes, for the 7.1" achro is an f/6, and I've seen through the scope numerous times. The owner ( a highly respected DSO observer and owner of a multitude of scopes large and small) has pushed the scope well over 300x with great results on globs, smaller galaxies and planetary nebula. It actually gave a nice view of Saturn with using some high-end orthos.

The owner has seen galaxies down to at least 14th mag, so the scope does quite well in the DSO realm, and the wide-field views using the Ethos eyepieces are terrific. My larger 8" goes even deeper. You can see and hear in the Galaxy Log series plus the blog, for many of my mid-size scope galaxy observations are with the 6" and 8" refractors.



Karl
E.O.H.


Chesmont Astronomical Society - www.chesmontastro.org
Galaxy Log - http://www.youtube.com/user/GalaxyLog4565?feature=mhee
Galaxy Log Blog - http://galaxylog.blogspot.com/
HASB - http://www.haveastellarbirthday.com
Telekit (Swayze optics) 22" F/4.5 Dob
Homemade (Parks Optics) 12.5" F/4.8 Dob
TMB/APM 8" f/9 Refractor”The Beast”. One great DEEP SKY achro
ES 6" f/6.5 achro. Good one
Celestron Omni XLT 102 refractor.
Celestron 10x60mm Binos


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Gord
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Re: Achro Vs Apo new [Re: De Lorme]
      #5755797 - 03/25/13 10:14 AM

Quote:

Because it's not primarily about just the view. Comfort and
ease of use are equally as important. A 8" F/8.8 achro refractor lens from Istar is about $1700. I would say a 16"
reflector mirror would be about a 1/3 more. The aproximate
total weight on putting a 8"F/6 on my CGEM is around 32lbs
with a length of 48" for about $2500. How much does a goto
trackimg system for a large reflector cost. About the same
or a little more than a CGEM-DX. But which one is more difficult to use. The reflector.
Reflectors you have to collimate accurately.
You have to install fans to get them to ambeint tempertures
You have to wait until cooled.
You have to stand on a stool or ladder to view.
Have to buy a coma corrector
Eyepieces cost considerably more
Large refractors take a lot more time to set up
Refractors have none of these problems.
One thing I will say though with Orion making large goto dobs cheaper than a large refractor that might make a differance initially. But I believe in the long run the extra cost to be able to sit and not have the other issues
will be worth it. People really do not consider convience
until they experience not having it. De Lorme




De Lorme,

Different people will find different things comfortable, but for myself, I'm with you on the seated observing position being the best. One below/behind the OTA ideally as you can get a comfortable seated position with a dob (smaller sizes) as well. With the tracking capabilities that they have now (dobs), it's really almost as good as the refractor/CAT's except for having to watch for thermals.

However, I think it's worth pointing out some issues with your statements around a large achro refractor being the only/best way to go. They have most of the issues you point to in the reflectors and other scopes:

-thermals, refractors are affected by these as well, especially so in larger sizes. At 6", the effect is there already (although still the best of all the designs) and from what I understand, by 10" they are becoming as bothersome as in other designs

-EP's & correctors, this is really dependent on the f-ratio. An F6 refractor is going to have as many issues as an F6 reflector. Aberrations are there in most designs and it's more about picking your poison and having the ability to work around it. In this regard, the refractors are likely worst (ie. CA). The ARIES Chromacor is an incredible tool for fixing this, but not as available as say a coma corrector for a newt and doesn't ultimately give you as perfect of overall result either (Chromacor corrects only the on-axis field). If you look at something like the Edge HD's from Celestron, they are already corrected and essentially perfect out of the box

-Setup/teardown of a large refractor --- NO! No advantage for the refractor, in fact quite the opposite! They are the worst of the bunch! Speaking from personal experience, I can say that the 6" refractor and the C14 are essentially equal in terms of effort. I'll call the OTA's a draw since the C14 is heavier and more compact, and the refractor is lighter, but longer. At 8", the refractor is a BEAST!

-The 8" F6 refractor you mention --- This is still a large scope (worse than the two I mention just above), but there's a real kicker to it: only good as a low power sweeper at 50x max magnification (per IStar's recommendations). I'm sure it would work ok at 100x, but this is in no way comparable to any other reflector out there. Every one of them will slaughter this thing in every way except for what it was purpose built to do (very low power sweeping of star fields). 100x is just getting going in most scopes of this size, and higher powers are really needed to get to the most details.

I can give you some personal experience with a bunch of different designs and how they compare. The 6" refractor can almost show as much as the C8 SCT on some objects (DSO's) and does better in a few cases (widest possible FOV and the contrast shown in that case). As soon as the FOV get's down to 1-deg or so, I find the C8 has the edge. For planetary, it's all C8. I got a chance to test a Chromacor and that is giving indications that it may level the field for planetary, but I need to get the two side-by-side.

The 10" newt is ahead of both the refractor and C8 on everything except widest FOV possible. The C14 is ahead of everything else (by a good bit...) except widest FOV.

To give you an idea of how far ahead the C14 is, the best view of a globular in the 6" refractor (M13) is what many of the less showcase globular's in the sky look like in the C14. Color in all objects is much more distinct. I have observed some of the globular clusters *in* M31 with the C14 from my backyard in the city. I've tried this with the 10" newt from the same conditions and came up short.

While I'm sure the 8" refractor (the longer ones) are going to do more than the 6" refractor, it comes at a cost (in various forms...) and will at best match up to a good 10" newt in some ways, but won't match bigger reflectors.

Clear skies,


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galaxyman
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Re: Achro Vs Apo new [Re: Gord]
      #5755841 - 03/25/13 10:32 AM

Hmm? Interesting that a scope of the same f/6, and only 0.9" larger would have such issues going much beyond 12x per inch of aperture, whereas the scope I describe above has no problem with over 40x per inch of aperture on the objects mentioned.

Karl
E.O.H.


Chesmont Astronomical Society - www.chesmontastro.org
Galaxy Log - http://www.youtube.com/user/GalaxyLog4565?feature=mhee
Galaxy Log Blog - http://galaxylog.blogspot.com/
HASB - http://www.haveastellarbirthday.com
Telekit (Swayze optics) 22" F/4.5 Dob
Homemade (Parks Optics) 12.5" F/4.8 Dob
TMB/APM 8" f/9 Refractor”The Beast”. One great DEEP SKY achro
ES 6" f/6.5 achro. Good one
Celestron Omni XLT 102 refractor.
Celestron 10x60mm Binos


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Gord
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Re: Achro Vs Apo new [Re: galaxyman]
      #5755868 - 03/25/13 10:45 AM

Hi Karl,

I know what you mean, but I expect there are a few things at play:

1. they are playing it extremely safe, although I know when you get into the design edge cases like these a slight variation in quality can have a big (negative) effect. Which leads to #2...

2. the bigger objectives are harder to make (good) and they don't have a lot of control over this since things are outsourced and built to a price point. The APM's like yours and the one you mention are made in China as well, but Markus has gotten out of this business due to the problems with trying to keep the quality high enough. His prices are higher just because he has to deal with the rejects to get a decent product.

So if you take a quality version of these like what Markus was offering, I think you get more and can go higher.

Clear skies,


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galaxyman
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Re: Achro Vs Apo new [Re: Gord]
      #5755896 - 03/25/13 10:59 AM

Hi Gord

Possible, and I think he still sells the 8" f/9

I though would love to see through one of the Istar's 8" scopes, and see what it can do under a good dark sky.

I've read some good things about their scopes so far, and I see you have a 6".

Karl
E.O.H.


Chesmont Astronomical Society - www.chesmontastro.org
Galaxy Log - http://www.youtube.com/user/GalaxyLog4565?feature=mhee
Galaxy Log Blog - http://galaxylog.blogspot.com/
HASB - http://www.haveastellarbirthday.com
Telekit (Swayze optics) 22" F/4.5 Dob
Homemade (Parks Optics) 12.5" F/4.8 Dob
TMB/APM 8" f/9 Refractor”The Beast”. One great DEEP SKY achro
ES 6" f/6.5 achro. Good one
Celestron Omni XLT 102 refractor.
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jrbarnett
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Re: Achro Vs Apo new [Re: timps]
      #5755908 - 03/25/13 11:03 AM

Problem with Newtonians is that the eyepiece is at the wrong end of the telescope.

- Jim


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Ed Holland
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Reged: 06/16/10

Loc: San Jose, CA and Oxford, UK
Re: Achro Vs Apo new [Re: jrbarnett]
      #5756109 - 03/25/13 12:38 PM


The importance of Achro Vs. Apo also depends on ones's experience level and enthusiasm for the hobby. Get a decent achro, and a beginner or budget minded person* can enjoy an awful lot of viewing and learning. For visual, I frequently find that the weakest link in the optical path is our atmosphere, and that my slightly aberrated (is that a word?) 5" Achro rarely gets a chance to reach maximum performance, and is perfectly adequate to my needs.

Would I like an Apo? of course, but can't justify it for the type of viewing I do, or the amount of time I have available.

*or a grumpy tightwad, like me


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Eddgie
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Re: Achro Vs Apo new [Re: galaxyman]
      #5756138 - 03/25/13 12:49 PM

Quote:

Well maybe because they have actually had great views with them? Unless you think they are all full of it?




In fact, I had a premium 6" f/8 acromat custom made for me about 10 years ago.

While the optical quality was superb, the scope was not partitularly satisfying as a planetary scope.

Long focal lenghts do improve, but do not eliminate the damage done by the CA.

And if you can get the same contrast performacne out of an MN66, why would you want a 6" f/15 achromat?

To reduce the CA to the level that the contrast transfer is better than an MN66, the focal lenght would be better at f/18 for the 6" refractor.

And even the 6" APO does not "blow my socks off" for planets. I routinely see much more in my C14.

I have had better planetary observing out of a number of larger reflectors.

The best planetary views I have ever had were when viewing though someone elses premium mirror 12" f/5 reflector with boundry layer fans (see, you don't have to wait more than 30 seconds to get perfect views, so cool down is not an issue unless you allow it to be) and premium (Zambuto) mirrors.

I have never seen a view with any scope bigger, smaller, obstructed, unobstruted, or polka dotts as I have seen in that scope.

But the premium 6" f/8 achromat was not the answer for me. My C14 is easily far better than that scope was for planets, and it was carfully designed to give as good aplaneatry performance as possible at f/8.

I sold it. No magic there for me.

In fact, the Meade 152ED f/9 I owned was better by a long strecth.


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Gord
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Re: Achro Vs Apo new [Re: galaxyman]
      #5756145 - 03/25/13 12:52 PM

Quote:

Hi Gord

Possible, and I think he still sells the 8" f/9

I though would love to see through one of the Istar's 8" scopes, and see what it can do under a good dark sky.

I've read some good things about their scopes so far, and I see you have a 6".

Karl
E.O.H.





Hi Karl,

Markus has the 8" F9 still listed, but I don't know if he is offering them any more. He said he wasn't when I contacted him about them and the reason gave was what I mentioned above (in terms of quality variation). He only want's to attach his name to quality optics so isn't willing to send out sub-par samples (which is good to hear!). He said some would be really great, and others terrible.

Unfortunately, I haven't been able to see what my current lineup are like under really dark skies. Life at the moment has me tied to my backyard so all of my comparisons are done from there.

The 6" classic IStar achro I have is a nice lens. I have got into testing optics more lately and I can now see it isn't perfect, but at the same time it appears to be in line with what they were originally spec'd at for these ones (about 1/5 wave). These were really good value, but I'd say they are now just good value as the prices have gone up. I don't think the R-series are so good in value since they cost significantly more than the classics and they aren't any better in terms of spec. Their OTA's are extremely well built with the only downside being the weight.

Clear skies,


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Eddgie
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Re: Achro Vs Apo new [Re: mark8888]
      #5756165 - 03/25/13 01:02 PM

Quote:

is there any advantage in getting a large APO as opposed to a reflector (of any size)? A large APO,




A quick story. About 8 years ago, I got in a very public debate with Roland Christen because I was very critical of the long wait list for a 155mm refractor. (Actually my grip was more to do with the black hole that is the AP notification process. For the full five years I was on the list, I never heard a peep from AP, which to me indicated blatent disregard for the potential customer).

During the course of this dialog, I had mentioned that I wanted the best planetary scope I could find.

He was quick and to the point in his response, and that response was essentially this (I am paraphrasing):

"Oh, well, if that is all you want, get a really good 10" f/6 reflector. That will be a better planetary scope than the 155EDF. These scopes are really best as astrographs."

Mr Christen I belive prefers his 10" MCT as a planetary scope over his own APOs.

But then again, Mr Christen used to use a C8 from time to time, so maybe he was not sure what he was talking about because OMG, who would want a C8?


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galaxyman
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Re: Achro Vs Apo new [Re: Eddgie]
      #5756203 - 03/25/13 01:41 PM

Quote:

Quote:

Well maybe because they have actually had great views with them? Unless you think they are all full of it?




In fact, I had a premium 6" f/8 acromat custom made for me about 10 years ago.

While the optical quality was superb, the scope was not partitularly satisfying as a planetary scope.

Long focal lenghts do improve, but do not eliminate the damage done by the CA.

And if you can get the same contrast performacne out of an MN66, why would you want a 6" f/15 achromat?

To reduce the CA to the level that the contrast transfer is better than an MN66, the focal lenght would be better at f/18 for the 6" refractor.

And even the 6" APO does not "blow my socks off" for planets. I routinely see much more in my C14.

I have had better planetary observing out of a number of larger reflectors.

The best planetary views I have ever had were when viewing though someone elses premium mirror 12" f/5 reflector with boundry layer fans (see, you don't have to wait more than 30 seconds to get perfect views, so cool down is not an issue unless you allow it to be) and premium (Zambuto) mirrors.

I have never seen a view with any scope bigger, smaller, obstructed, unobstruted, or polka dotts as I have seen in that scope.

But the premium 6" f/8 achromat was not the answer for me. My C14 is easily far better than that scope was for planets, and it was carfully designed to give as good aplaneatry performance as possible at f/8.

I sold it. No magic there for me.

In fact, the Meade 152ED f/9 I owned was better by a long strecth.




Hi Ed

I agree, and though I don't observe planets, I've seen how well a great 12.5" reflector does on planets (say like Saturn) for I have one.

I'm a DSO observer, and yes here the larger dob like my 22" is my deep deep scope. The large quality refractors give me a different perspective here, and give the most aesthetic views. In fact in some way these views make up for lack of aperture to the larger dob. I know, for I had both the 8" refractor and the 22" dob (wonderful Swayze optics and Spectrum Max R coatings) side by side on a terrific night at our darkest local (within 2 hour drive) site.

Using very similar magnifications, the big 8" refractor was certainly holding its own for its aperture (wife did some drawings), and even showing a 15th mag galaxy.

Inch for inch I'll take the refractor here, though yes the larger scope of high quality is hard to beat.


Karl
E.O.H.


Chesmont Astronomical Society - www.chesmontastro.org
Galaxy Log - http://www.youtube.com/user/GalaxyLog4565?feature=mhee
Galaxy Log Blog - http://galaxylog.blogspot.com/
HASB - http://www.haveastellarbirthday.com
Telekit (Swayze optics) 22" F/4.5 Dob
Homemade (Parks Optics) 12.5" F/4.8 Dob
TMB/APM 8" f/9 Refractor”The Beast”. One great DEEP SKY achro
ES 6" f/6.5 achro. Good one
Celestron Omni XLT 102 refractor.
Celestron 10x60mm Binos


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galaxyman
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Reged: 04/04/05

Loc: Limerick, Pa
Re: Achro Vs Apo new [Re: Gord]
      #5756224 - 03/25/13 01:54 PM

Quote:

Quote:

Hi Gord

Possible, and I think he still sells the 8" f/9

I though would love to see through one of the Istar's 8" scopes, and see what it can do under a good dark sky.

I've read some good things about their scopes so far, and I see you have a 6".

Karl
E.O.H.





Hi Karl,

Markus has the 8" F9 still listed, but I don't know if he is offering them any more. He said he wasn't when I contacted him about them and the reason gave was what I mentioned above (in terms of quality variation). He only want's to attach his name to quality optics so isn't willing to send out sub-par samples (which is good to hear!). He said some would be really great, and others terrible.

Unfortunately, I haven't been able to see what my current lineup are like under really dark skies. Life at the moment has me tied to my backyard so all of my comparisons are done from there.

The 6" classic IStar achro I have is a nice lens. I have got into testing optics more lately and I can now see it isn't perfect, but at the same time it appears to be in line with what they were originally spec'd at for these ones (about 1/5 wave). These were really good value, but I'd say they are now just good value as the prices have gone up. I don't think the R-series are so good in value since they cost significantly more than the classics and they aren't any better in terms of spec. Their OTA's are extremely well built with the only downside being the weight.

Clear skies,




Hi Gord

Interesting and glad I got a great one

Well I hope you can get back out to darker sites, for a good 6" refractor can be lots of fun under clear dark skies.

I see ISTAR is going to be at NEAF, so I'll definitely check them out.


Karl
E.O.H.


Chesmont Astronomical Society - www.chesmontastro.org
Galaxy Log - http://www.youtube.com/user/GalaxyLog4565?feature=mhee
Galaxy Log Blog - http://galaxylog.blogspot.com/
HASB - http://www.haveastellarbirthday.com
Telekit (Swayze optics) 22" F/4.5 Dob
Homemade (Parks Optics) 12.5" F/4.8 Dob
TMB/APM 8" f/9 Refractor”The Beast”. One great DEEP SKY achro
ES 6" f/6.5 achro. Good one
Celestron Omni XLT 102 refractor.
Celestron 10x60mm Binos


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De Lorme
professor emeritus
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Reged: 12/30/08

Re: Achro Vs Apo new [Re: galaxyman]
      #5756295 - 03/25/13 02:30 PM

As I said before It's not only about the view.
My AT 10" reflector was good. But I had to continulaly rotate the tube to see. Collimate, allow to cool,buy a coma corrector and STAND all the time.
I keep seeing big dobs up for sale here on CN. Why?
Because after a while the body says Not gonna do this no more!LOL I have no doubts that a BIG dob gives great views.
But the convience factor slowly takes over. I have read many
times, the best scope is the one that you use. It is so true. If it Just sits there because of the sheer {bulk}hassle to deal with you end up selling it and getting a refracter. My first telescope was a Meade 10" cat. I could
not sit and look with it either. So good buy Cat.
Please don't take this like your dobs or cats are junk. Thier not.
People don't think about comfort and convience until they
do not have it. Would you rather go to work in a Dodge Ram
in the middle of the winter with no heat or go to work in Dodge Dart with heat? Keep Looking up, De Lorme


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t.r.
Post Laureate
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Reged: 02/14/08

Loc: Upstate NY
Re: Achro Vs Apo new [Re: De Lorme]
      #5756391 - 03/25/13 03:13 PM

Quote:

Mr Christen I belive prefers his 10" MCT as a planetary scope over his own APOs.




In the Florida Keys, at the winter star party yes...at home in the typical seeing conditions in the northern part of the country, no. And he has said as much. That is the only point you forget to address Eddgie...not everyone has your SouthWest seeing conditions and climate. In many parts of the country a puny 5" refractor will surpass that 14 SCT on planetary aesthetics. Fact. My 5" apo beat a Cave 16" newt and got a star parties "Best view on the field award" looking at Jupiter. It can and does happen, albeit usually only North of the Mason-Dixon line!


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mark8888
Carpal Tunnel


Reged: 09/24/10

Re: Achro Vs Apo new [Re: t.r.]
      #5756439 - 03/25/13 03:32 PM

Quote:

Quote:

Mr Christen I belive prefers his 10" MCT as a planetary scope over his own APOs.




In the Florida Keys, at the winter star party yes...at home in the typical seeing conditions in the northern part of the country, no. And he has said as much. That is the only point you forget to address Eddgie...not everyone has your SouthWest seeing conditions and climate. In many parts of the country a pultry 5" refractor will surpass that 14 SCT on planetary aesthetics. Fact. My 5" apo beat a Cave 16" newt and got a star parties "Best view on the field award" looking at Jupiter. It can and does happen, usually only North of the Mason-Dixon line!




If you google image search: Cave 16" newt

you get a funny mix of images. I'm not sure if any of them are a Cave 16" newt though.

In any event, I'm wondering... OK, so if you use a C14, a big dob, Cave 16" newt, in a place with poor seeing in the north for example... what exactly do you see most of the time? Basically a jumbled up mess that only very occasionally clears up and shows a lot of detail, and then goes back to the mess?

A scope with how many inches of aperture used at a place with poor seeing creates an almost-always unstable image? In other words, how many inches is the maximum at which one can expect a decent image a lot of the time at a place with generally not very good seeing?



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t.r.
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Reged: 02/14/08

Loc: Upstate NY
Re: Achro Vs Apo new [Re: mark8888]
      #5756472 - 03/25/13 03:48 PM

This may give you an idea...in NY, in a large aperture scope (+10")this would be considered a fairly descent/average view. However, look closely, there is no N or S hemisphere detail(spots,belts,mottling,gradation), no detail within the belts, no clearly defined edges to belts, zones, etc. This really isn't that a great a view, but all the macro detail is there. What is lacking is the micro details which really make for a fine view. The image is also not stable, shimmering, jumping around and soft. But for many, this is indeed a "good" view!

http://www.youtube.com/watch?v=5p_Wx-0HYNs



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dan_h
Carpal Tunnel


Reged: 12/10/07

Re: Achro Vs Apo new [Re: mark8888]
      #5756508 - 03/25/13 04:13 PM

<< What exactly do you see most of the time? Basically a jumbled up mess that only very occasionally clears up and shows a lot of detail, and then goes back to the mess? >>

No. It never clears up. At least not around here in the winter time.

I think part of the reason there is such a gap between the points of view expressed on these forums is because many folks don't appreciate the vast differences in viewing conditions that prevail in different areas. I have been to WSP and seen some marvelous views. I have been in the mountains outside Tuscon where you can see forever. I have also lived most of my life in the area north and east of the Great Lakes where seeing is typically bad to horrible (and that's when the jet stream isn't messing things up.)

dan


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Lane
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Re: Achro Vs Apo new [Re: jrbarnett]
      #5756628 - 03/25/13 05:15 PM

Quote:

Problem with Newtonians is that the eyepiece is at the wrong end of the telescope.

- Jim




But you buy one of those special newts like they use in the Little Ceasar's commercial, they seem to have solved that problem.


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jrbarnett
Eyepiece Hooligan
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Re: Achro Vs Apo new [Re: Lane]
      #5756652 - 03/25/13 05:30 PM

"It's pizza time!"



- Jim


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timps
sage


Reged: 02/24/13

Re: Achro Vs Apo new [Re: jrbarnett]
      #5756983 - 03/25/13 08:47 PM

Hope it's a large diameter pizza!

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De Lorme
professor emeritus
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Reged: 12/30/08

Re: Achro Vs Apo new [Re: timps]
      #5757345 - 03/26/13 01:11 AM

Only if it is delivered!

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Jon Isaacs
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Re: Achro Vs Apo new [Re: De Lorme]
      #5757737 - 03/26/13 09:09 AM

Quote:

Because it's not primarily about just the view. Comfort and
ease of use are equally as important. A 8" F/8.8 achro refractor lens from Istar is about $1700. I would say a 16"
reflector mirror would be about a 1/3 more. The aproximate
total weight on putting a 8"F/6 on my CGEM is around 32lbs
with a length of 48" for about $2500. How much does a goto
trackimg system for a large reflector cost. About the same
or a little more than a CGEM-DX. But which one is more difficult to use. The reflector.




You are comparing an 8 inch achromatic refractor to an 16 inch Newtonian, it's far bigger and far more capable but that comes with a price. Even so, I have to say, I am quite sure I can setup my 16 inch Dob faster than you can setup your 8 inch refractor and I can fit it in a smaller space in my vehicle. Comfort, I'll take the Dob, I am never down in the dirt trying to view an object near the zenith. No need for a ladder...

The appropriate comparison would be between a high quality 8 inch or 10 inch Newtonian and the 8 inch achromat. The eyepiece issues you mention, that only because the refractor is so slow, it can't be fast because the color correction would even be worse than it is. Were the Newtonian F/8.8, the same eyepieces would work in both.. Cool down... even my 80mm F/7 needs to cool down, big refractors take longer...

Jon


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Sean Puett
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Reged: 09/06/10

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Re: Achro Vs Apo new [Re: t.r.]
      #5757762 - 03/26/13 09:32 AM

Deleted inaccurate assumption

Edited by Sean Puett (03/26/13 12:29 PM)


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moynihan
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Loc: Lake Michigan Watershed
Re: Achro Vs Apo new [Re: dan_h]
      #5757864 - 03/26/13 10:18 AM

Quote:

...I think part of the reason there is such a gap between the points of view expressed on these forums is because many folks don't appreciate the vast differences in viewing conditions that prevail in different areas.




I agree. This is a huge factor.


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Sean Puett
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Reged: 09/06/10

Loc: always cloudy, washington
Re: Achro Vs Apo new [Re: Sean Puett]
      #5757961 - 03/26/13 11:07 AM

This again is just opinion but with a $1700 price tag on an achro, I would put that money on a TAK fs102 instead. A nice flourite doublet any day over purple haze running through my brain.

I don't know where the idea that newts are harder to use came from but, that is incorrect. My first telescope was a newt. The first time I uncollimated it, it took me 10 minutes. That is with a screwdriver. Later, I spent $20 on Bob's knobs and cut the time to about 2 minutes. My average time with a screwdriver was less than five minutes. My 12" dob is set up and going in less than 5 minutes at home including collimation. My 4" refractor that I bought to make quick views "easier and quicker" takes two to 3 times that. My dob is in the garage so thermal issues are not an issue. Using the fan keeps it from becoming an issue as the night rolls on and the temp continues to drop.
Big newts can even show that the Galiean moons are more than just points of light. You can see disks if the scope is big enough and the atmosphere allows.

Edited by Sean Puett (03/26/13 12:30 PM)


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Gord
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Re: Achro Vs Apo new [Re: Sean Puett]
      #5757983 - 03/26/13 11:19 AM

I believe that video posted above was taken through a 10" APO.

It's representative of the way things appear in some seeing conditions, but I often see far larger swings of mush to sharp. I would also say that the details shown are pretty ordinary. I've seen more in the C8 and far more in the C14.

Clear skies,


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Sean Puett
Carpal Tunnel
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Reged: 09/06/10

Loc: always cloudy, washington
Re: Achro Vs Apo new [Re: Gord]
      #5758047 - 03/26/13 11:59 AM

Sorry everyone. I put it on full screen without reading. I assumed it was a negative newt. Video. I have seen many horrible newt videos on youtube. Even some where they were trying to convince you that there was a mothership with smaller ufo crafts taking off and landing. It was an object over magnified with huge tube currents and it was out of focus.

Btw. At my dark site my dob get far better views of Jupiter than that video. I bet a 12" newt on a GEM would be awesome.


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t.r.
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Re: Achro Vs Apo new [Re: Sean Puett]
      #5758050 - 03/26/13 12:00 PM

For light reading...

http://www.brayebrookobservatory.org/BrayObsWebSite/HOMEPAGE/forum/Apo_vs_Ach...


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Eddgie
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Re: Achro Vs Apo new [Re: Gord]
      #5758055 - 03/26/13 12:01 PM

Quote:

more in the C14.




Yes, me too.

The view in the video though is "typical" of my view with my own C14. And even to see that level of detail, seeing needs to be pretty decent.


Here is the ultimate reality regarding this thread though.

None of us (perhaps including the OP) really knows what it will take to "Blow his socks off."

The view in my C14 rarely blows my socks off because seeing usually prevents that "OMG" experience of seeing Jupiter the way it appears in a CCD image.

Usually it takes a lot of patience and practice to see the level of detail the scope is capable of it when conditions are not excellent (Binoviewers help!)

But back to the OPs question, and if it has not been answered yet, then it will never be answered, but my personal feeling is that a 6" refractor, APO or Achromat" is not going to "blow his socks off" either.

And we may not know what level of detail he will need to do that.

My own experience based on ownership of maybe 40 telescopes has been that the more decent quality clear aperture you bring to the party, the more you see.

But I cannot for the life of me know how tight the OPS socks are on, and the consequent amount of pressure required to pop them off. I just don't think a 6" achromat is going to do it though.


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Sean Puett
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Re: Achro Vs Apo new [Re: Eddgie]
      #5758098 - 03/26/13 12:22 PM

At home my views are rarely that good. I live barely above sea level in the astronomy purgatory of western Washington. I have had nice views of Jupiter at home but, the seeing is normally worse than the video.

The places I travel to are higher in elevation with much dryer air and unless the eastern half of the state is on fire, like last summer, the seeing is wonderfully steady. The views through the muck are better than the average "clear" night at home.

This is how I found out that small aperture does not "beat the seeing". Low mag can reduce its effect but, small refractors will still have bad looking stars here. I thought my refractor was not collimated when I first got it because stars looked so bad. Anyway, that 10" apo hopefully can travel to higher elevation and thinner atmosphere and it would be a completely different video.


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De Lorme
professor emeritus
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Reged: 12/30/08

Re: Achro Vs Apo new [Re: Eddgie]
      #5758192 - 03/26/13 12:58 PM

Yes, you are right Eddgie I need more APERTURE. I can get the weight down to around 32lbs for a 8"F/6. Yes there will be some color but the planets are not my first priority.
The real problem to me is the atmosphere. The way a Apo
handles the light verses a larger acho. Would the 6"apo resolve gobulor clusters? Or would the 8" achro be what's needed.That was my primary reason for posting APO VS.ACHRO.
There are only a few planets but there is a whole universe
to see. When I look at the Moon or Jupitor{assuming the weather is good}I only see color on the rim, not across the body.So it doesn't bother me.I've come to realize that the convience factor is equally as important as the view through the telescope. When I had my AT 10" reflector I spent about a 1/3 of the time rotating the rings and
fine tuning the collimation. Plus I could never just sit,
relax and just look. Remember the saying, the best telescope
is the one you ACCTUALLY use. So please do not take this personaly, reflectors require more effort. So when I see large dobs{like right now}up for sale I understand why.
Have you ever considered building a rool off roof. Would
not have to set up that big dob anymore. It's so nice to be out of the wind,have a cup of coffee ,listen to the radio,
and don't have to tear it all down at the end.
So which one the 6" apo or the 8" achro. Priority are
gobulor clustors,galaxies,planets. If you think I should look to the apo which brand? Clear Skies, De Lorme


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Gord
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Re: Achro Vs Apo new [Re: De Lorme]
      #5758288 - 03/26/13 01:46 PM

Quote:


So which one the 6" apo or the 8" achro. Priority are
gobulor clustors,galaxies,planets.




De Lorme,

In my opinion, neither. You don't like newts for usability reasons (I can understand that), but you do want to see DSO's primarily it seems. You want to resolve globulars.

SCT or MCT. Same viewing position as the refractor, easier to mount, and enough light grasp to make out something on those DSO's. The view between the 6" refractor and even the 10" newt on globulars is significant in terms of resolution. What is hinted at in 6" is obvious at 10". And it keeps going as you go bigger I find.

If you are looking around the 30lbs range, go for a C11HD and it will better either of these for all your use cases.

Clear skies,


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ValeryD
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Reged: 11/26/05

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Re: Achro Vs Apo new [Re: Gord]
      #5758309 - 03/26/13 02:05 PM

Quote:

Quote:


So which one the 6" apo or the 8" achro. Priority are
gobulor clustors,galaxies,planets.




De Lorme,

In my opinion, neither. You don't like newts for usability reasons (I can understand that), but you do want to see DSO's primarily it seems. You want to resolve globulars.

SCT or MCT. Same viewing position as the refractor, easier to mount, and enough light grasp to make out something on those DSO's. The view between the 6" refractor and even the 10" newt on globulars is significant in terms of resolution. What is hinted at in 6" is obvious at 10". And it keeps going as you go bigger I find.

If you are looking around the 30lbs range, go for a C11HD and it will better either of these for all your use cases.

Clear skies,




+100


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galaxyman
Vendor - Have a Stellar Birthday
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Reged: 04/04/05

Loc: Limerick, Pa
Re: Achro Vs Apo new [Re: De Lorme]
      #5758333 - 03/26/13 02:17 PM

Well if the refractor is your choice then the larger 8" achro (of very good quality) is a much better DSO scope over it's smaller 6" cousin.

Globs like M-3, M-5, M-13, M-22 as examples in my 8" refractor take on a almost 3D look, even a smaller glob like M-56 has numerous stars seen in the eyepiece.

Spiral galaxies like M-33 or M-51 show the spiral arms, and edge-ons like M-104, Ngc 4565, Ngc 3628, Ngc 891 easily show their dark lanes. One of the neatest views is M-82 at over 400x showing amazing detail.

The best "overall" view I've seen of the Orion nebula was through the 8" refractor from a top Dolly Sods mountain in WV. The detail with pastel colors is still fixed in my mind.

A good large refractor can (is) a very good DSO scope.

I do agree with Gord that a large SCT can be a very good alternative, though I still like a good refractor views a bit more.


Karl
E.O.H.


Chesmont Astronomical Society - www.chesmontastro.org
Galaxy Log - http://www.youtube.com/user/GalaxyLog4565?feature=mhee
Galaxy Log Blog - http://galaxylog.blogspot.com/
HASB - http://www.haveastellarbirthday.com
Telekit (Swayze optics) 22" F/4.5 Dob
Homemade (Parks Optics) 12.5" F/4.8 Dob
TMB/APM 8" f/9 Refractor”The Beast”. One great DEEP SKY achro
ES 6" f/6.5 achro. Good one
Celestron Omni XLT 102 refractor.
Celestron 10x60mm Binos


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Eddgie
Postmaster
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Re: Achro Vs Apo new [Re: De Lorme]
      #5758398 - 03/26/13 02:59 PM

Only one Glubular Cluster will not fit into the field of my C14, and that is the Omega cluster.

My EdgeHD 8" resolves all globulars better than my 6" APO.

Probably as well as an 8" achromat does unless you make it f/20. Otherwise, a lot of energy is taken out of the Airy Disk, which will lower limiting magnitude.

And if you think setting up your current scope is hard, or that it is hard to use, you ain't seen nothing yet. An 8" achrmat will be far more challenging.

I would also recommend the EdgeHD 11". It is a lot of apeture for the money, and the outstading off-axis performance is on par with the best large aperture reflectors I have ever used.

This though. As the aperture gets larger, the Airy Disk gets smaller (for given magnificaiton) and the affects of seeing start to affect the image almost just as much as for obstructed scopes.

Once the Airy Disk diamter gets smaller than about 1.5 arc seconds, it is very difficult to get a clean point on brighter stars.


It matters little is the scope is an achomat, APO, or reflector once the aperture gets 8" and larger.

Dim stars in Globular Clusters will still look like pinpoints even in a C14 if you use lower powers.

But I routinely use 325x on Globulars in the C14, and since most of the stars are very faint, the view still looks excellent.

By far and away, the C14 is the best scope I have ever used on Globulars.

But any similarly large apeture scope will do as well on Globulars.

Which is to say considerable better than a 6" or 8" apeture.

Good luck with your quest. I fear that you will not find a solution using refractors that you can get with an EdgeHD 11 for a fraction of the price though.

And remsmber this. I have cataloged perhaps 1000 different targets using my C14.

All by about 50 even fit into the field.

If they don't fit into the field of the C14, I use the EdgeHD 8"

If they don't fit into the field of the EdgeHD 8", I use the 6" APO.

If they don't fit into the field of the 6" APO, I use binoculars.

Pick the apture for the target. If Globulars are what you most badlly want to see, pick a big aperture, because with Globular Clusters, bigger is always better.


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De Lorme
professor emeritus
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Reged: 12/30/08

Re: Achro Vs Apo new [Re: galaxyman]
      #5758411 - 03/26/13 03:05 PM

Karl, I keep saying to everybody that caring is sharing
so would you share{LOL} your big 8" to a deprived dso viewer? I contacted Alex at Istar about making a 8"F/6 lens for us who have a Atlas or CGEM mount and do not care about a color on the rim of planets. I'm hoping he will listen.
Do you know any body in the affordable randge(under $2000}
that makes 8"f/6 lens? Your review spurs me on. Thanks a
bunch Karl. Clear Skies! De Lorme


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t.r.
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Reged: 02/14/08

Loc: Upstate NY
Re: Achro Vs Apo new [Re: De Lorme]
      #5758425 - 03/26/13 03:13 PM

Just found this for a comparison to the TMB 10"...

http://www.youtube.com/watch?v=5lmAIsPg9sE


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Gord
Carpal Tunnel
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Reged: 01/06/04

Loc: Toronto, ON, Canada
Re: Achro Vs Apo new [Re: De Lorme]
      #5758470 - 03/26/13 03:33 PM

De Lorme,

IStar has already produced the 8" F6, so they should have no trouble doing one for you again. It's still a very heavy scope and quite a load for that class of mount, but if you are tolerant, it could work.

The big limitation is it's not intended to use at much power. We discussed this earlier in the thread, 50x is what they recommend.

If you are set on a refractor, then I agree with Karl's comments that an 8" achro is the better way to go, but it must be of high quality and longer (like his) is better. The ARIES Chromacor would also be the way to go with it as well for really getting something out of it on the planets. But be aware of the size of scope it is. Search for comments from Karl, or James Ling who has an IStar variant of that size. BIG scope!

I even see myself having something like this at some point (because you can never have enough scopes!), but I would not pick one of these before something like a C14 given that it's more effort for less return.

Clear skies,


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galaxyman
Vendor - Have a Stellar Birthday
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Reged: 04/04/05

Loc: Limerick, Pa
Re: Achro Vs Apo new [Re: De Lorme]
      #5758481 - 03/26/13 03:39 PM

First Ed this big 8" refractor does go deeper than a 8" SCT, owned a good one (8" SCT) as well as a two very good 8" newts of f/4.5 and f/5, and the refractor most definitely goes deeper (14 to 15 mag galaxies for instance). Check my DSO write-ups here in CN (including the review) or Galaxy Log for more.

De Lorme I share the views with any of my scopes, as does all in the CAS. We are DSO fanatics.

Not sure about getting a good 8" lens for the price you wish. Any well made lens of quality glass, coatings, and lens cell will cost more.

I do realize you want a large refractor, though I do here agree with Ed that I would not pass on a good 11" SCT, particularly if a GOOD 8" refractor of your choice cannot be had.


Karl
E.O.H.


Chesmont Astronomical Society - www.chesmontastro.org
Galaxy Log - http://www.youtube.com/user/GalaxyLog4565?feature=mhee
Galaxy Log Blog - http://galaxylog.blogspot.com/
HASB - http://www.haveastellarbirthday.com
Telekit (Swayze optics) 22" F/4.5 Dob
Homemade (Parks Optics) 12.5" F/4.8 Dob
TMB/APM 8" f/9 Refractor”The Beast”. One great DEEP SKY achro
ES 6" f/6.5 achro. Good one
Celestron Omni XLT 102 refractor.
Celestron 10x60mm Binos


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Paul C-I
super member


Reged: 03/23/08

Loc: United Kingdom
Re: Achro Vs Apo new [Re: galaxyman]
      #5758538 - 03/26/13 04:04 PM

I will chip in at this stage and mention that I have one of Istar's 8" F12 R35 slim lens being made for me at this time. This was for a self build but may go for Ale's TCR arrangement. Had a Vixen ED 6" and currently Intes MN86 & 78 so am looking forward to comparing the views that the different optical systems will throw up.
(hoping the G11 will suffice for visual on the Istar!)
Paul


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De Lorme
professor emeritus
*****

Reged: 12/30/08

Re: Achro Vs Apo new [Re: Paul C-I]
      #5758812 - 03/26/13 06:28 PM

Hi Gord, Yes I saw that to but the with the tube it goes over the the weight Limit. I guess I could buy the scope and put it in another tube? I looked on Istar site and there was no 8" F/6 lens to be found.
Karl,Istar sales their 8"f8.8 achro. for around $1,700.
I would think they could make a 8"f/6 for the same amount.
I'm convinced that I will be able to bring in the GC with a
8"F6. The planets will be the trade off. Color can be handled,so no big deal. But I have to wait and see what Alex says. One thing for sure the DOB idea is dead.
If I go to the C14" I would have to just start over with a
CGEM-DX. Which does not fit at all into my money tree.

Clear Skies, De Lorme


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Joe Bergeron
Vendor - Space Art


Reged: 11/10/03

Loc: Upstate NY
Re: Achro Vs Apo new [Re: Paul C-I]
      #5759074 - 03/26/13 08:21 PM

Quote:

I will chip in at this stage and mention that I have one of Istar's 8" F12 R35 slim lens being made for me at this time. This was for a self build but may go for Ale's TCR arrangement. Had a Vixen ED 6" and currently Intes MN86 & 78 so am looking forward to comparing the views that the different optical systems will throw up.
(hoping the G11 will suffice for visual on the Istar!)
Paul




I think you'll find that 8" f/12 greatly outmatches the G11. I've seen a 6" f/12 on one, and it's not very steady. I consider my 6" f/9 the limit for that mount. You will find that the slightest breeze induces major wobbles.


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timps
sage


Reged: 02/24/13

Re: Achro Vs Apo new [Re: Eddgie]
      #5759113 - 03/26/13 08:33 PM

I have to admit that now, after posting this thread and doing some soul searching, I believe that the best "allround" telescope (if there is such a thing), would be a SCT and for me that would be a 12".
They are good for deep space, good for planetary and one can still get decent images with them.
SCT's are pobably the best value when one considers: ease of use, versatility and aperture.
They have no purple haze like acros and the cost difference to an apo of half the aperture......well we all know that.
For the price of a Tak TOA130 (tube only & ready to go) one can have the latest 12" Meade + a G11 or even the new EQ8 mount! Or stick with the fork mount and use the extra $$ for imaging equipment. More will be seen with a 12" SCT than with any 130mm apo or achro.


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Gord
Carpal Tunnel
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Reged: 01/06/04

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Re: Achro Vs Apo new [Re: timps]
      #5759183 - 03/26/13 09:05 PM

timps,

A good decision I think. The other thing to consider is that you don't *have* to limit yourself to just one telescope. You also don't have to stay married to it forever. Compliment the CAT with a refractor. An ES127 triplet will give you a lot of what a TOA130 can do and is very affordable. Or go a little smaller and piggy-back it on the cat. Lots of options.

Clear skies!


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buddyjesus
Carpal Tunnel
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Reged: 07/07/10

Loc: Davison, Michigan
Re: Achro Vs Apo new [Re: Gord]
      #5759221 - 03/26/13 09:27 PM

good call gord. A smaller scope for use when the big gun is cooling would be a perfect complement.

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azure1961p
Postmaster
*****

Reged: 01/17/09

Loc: USA
Re: Achro Vs Apo new [Re: Sean Puett]
      #5759273 - 03/26/13 10:07 PM

Quote:

This again is just opinion but with a $1700 price tag on an achro, I would put that money on a TAK fs102 instead. A nice flourite doublet any day over purple haze running through my brain.

s.




I think Jimi said: " all in my brain". Jus sayin;)

Pete


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beanerds
sage


Reged: 07/15/08

Loc: Darwin Australia
Re: Achro Vs Apo new [Re: azure1961p]
      #5759582 - 03/27/13 04:59 AM

Good choice Timps , glad we could help .
The idea here to get an ES 127mm triplet to compliment your up and comming 12 inch Meade is a very good one .
I use my SKY90 or Istar 127mm f8 achro in the same roll while I am waiting for my M210 to cool .
Good luck mate .
Brian.


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HCR32
sage


Reged: 08/27/10

Loc: Australia
Re: Achro Vs Apo new [Re: timps]
      #5759605 - 03/27/13 05:50 AM

You are about to take your first step on a long journey of scope ownerships, but the M12 is a good choice. My Meade RCX400 was with me for four years and believed it was a turn around point for optics produced by Meade. If they are still manufacturing the same type of quality then you will be pretty happy with it. I still remember a lot of the views in it even though I've look through some scopes that people would consider better. That says a lot and I'm a refractor fan. I hope you get the same satisfaction as I did with my Meade.

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timps
sage


Reged: 02/24/13

Re: Achro Vs Apo new [Re: HCR32]
      #5759680 - 03/27/13 07:46 AM

Thanks all.

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