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Equipment Discussions >> Refractors

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jrbarnett
Eyepiece Hooligan
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Reged: 02/28/06

Loc: Petaluma, CA
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
*****

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
Postmaster
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Reged: 06/16/04

Loc: San Diego and Boulevard, CA
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
Carpal Tunnel
*****

Reged: 09/06/10

Loc: always cloudy, washington
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
Carpal Tunnel


Reged: 07/22/03

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
Carpal Tunnel
*****

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
Carpal Tunnel
*****

Reged: 01/06/04

Loc: Toronto, ON, Canada
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
*****

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.
Post Laureate
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Reged: 02/14/08

Loc: Upstate NY
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
Postmaster
*****

Reged: 02/01/06

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
Carpal Tunnel
*****

Reged: 09/06/10

Loc: always cloudy, washington
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
*****

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
Carpal Tunnel
*****

Reged: 01/06/04

Loc: Toronto, ON, Canada
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
Vendor (Aries)
*****

Reged: 11/26/05

Loc: Kherson, Ukraine.
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
*****

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
*****

Reged: 02/01/06

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
*****

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.
Post Laureate
*****

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
*****

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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