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Equipment Discussions >> Refractors

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saemark30
Pooh-Bah


Reged: 02/21/12

Re: Apochromatic or Achromatic does it really matter? new [Re: PJ Anway]
      #5269793 - 06/13/12 03:34 PM

What do you call a diffraction assisted lens code-named H-Bomb?

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ken hubal
Pooh-Bah
*****

Reged: 05/01/07

Re: Apochromatic or Achromatic does it really matter? new [Re: saemark30]
      #5269901 - 06/13/12 04:47 PM

I have yet to view through ANY apo that did anything better than my well corrected long focus achro! The continued market hype behind apos is nothing more than excellent comedy!

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Alan French
Night Owl
*****

Reged: 01/28/05

Loc: Upstate NY
Re: Apochromatic or Achromatic does it really matter? new [Re: ken hubal]
      #5270038 - 06/13/12 06:25 PM

Quote:

I have yet to view through ANY apo that did anything better than my well corrected long focus achro! The continued market hype behind apos is nothing more than excellent comedy!




You know, it's funny, Ken. It wasn't marketing hype that started folks buying scopes made by those folks in Rockford, Illinois - it was people seeing and using them under the night sky at various star parties and conventions.

Clear skies, Alan


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jmiele
Patron Saint?
*****

Reged: 12/04/10

Re: Apochromatic or Achromatic does it really matter? new [Re: Alan French]
      #5270105 - 06/13/12 07:18 PM

While I agree with your logic Alan, I think the photographic benefits afforded us by Apo's was also a big contributed to their rise in popularity. There are many good long FL achromatic instruments out there as well. In the visible wavelengths anyway.

All that said, all my Apo's look best to me

Best, Joe


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ken svp120
Carpal Tunnel


Reged: 12/19/04

Loc: Ohio
Re: Apochromatic or Achromatic does it really matter? new [Re: jmiele]
      #5270317 - 06/13/12 09:51 PM

I'm going to add my two cents by saying that a long achro might well be corrected as well as an apo but that the nice compact package of a modern apo makes such scope truly portable...you can take it to whatever dark skies you wish with very little transport worries and get phenomenal optical performance. Or, if permanently mounted, you can put it in a smaller facility. Yes, an apchromat definitely matters for more than one reason. Can you attain the same performance from an achromat...probably...but with the same functionality? I don't think so.

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watcher
Carpal Tunnel
*****

Reged: 11/21/07

Loc: St. Louis, MO
Re: Apochromatic or Achromatic does it really matter? new [Re: ken svp120]
      #5270338 - 06/13/12 10:03 PM

Portability and imaging have both led to the popularity of APOs. IMO if it were just the view that counted, they would never have amounted to more than the niche market that they have forced the long achro into. But the asteroid did hit, and the dinosaurs no longer rule the earth.

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Astropin
super member


Reged: 08/30/07

Loc: Michigan
Re: Apochromatic or Achromatic does it really matter? new [Re: watcher]
      #5270365 - 06/13/12 10:20 PM

I decided to split the difference and bought an ED doublet (most would call it a "semi-apo").

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Alan French
Night Owl
*****

Reged: 01/28/05

Loc: Upstate NY
Re: Apochromatic or Achromatic does it really matter? new [Re: Astropin]
      #5270372 - 06/13/12 10:26 PM

As far as long achromats go, the asteroid hit before the days of the apochromat. I think it would be fair to say that apochromats brought refractors back to life.

Clear skies, Alan

Edited by Alan French (06/13/12 10:33 PM)


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watcher
Carpal Tunnel
*****

Reged: 11/21/07

Loc: St. Louis, MO
Re: Apochromatic or Achromatic does it really matter? new [Re: Alan French]
      #5270401 - 06/13/12 10:45 PM

Oh yeah, I keep forgetting about those mirrored things taking over way back when. I tend to hang out here where the refractors still rule, and see my corner of the universe as "all there is".

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Maurice
member


Reged: 04/19/07

Loc: Netherlands
Re: Apochromatic or Achromatic does it really matter? new [Re: Jon Isaacs]
      #6076361 - 09/12/13 05:06 AM

Hi all, I know this is an old thread but maybe you can help me out.
Currently I have an WO 80 ED scope. I'm really satisfied with it, but after using it a couple of years now I'm in the "need" for a larger refractor to be able to distinqush one nabula from the other in light poluted skies.

I don't do AP, so an ED looks perfect for my needs. I also want a refractor, I love the views they provide.
This one is on my wish list: http://www.teleskop-express.de/shop/product_info.php/language/de/info/p4688_T...

But recently I came across a 6" achromat: http://www.teleskop-express.de/shop/product_info.php?products_id=2229#ebericht

I know this scope will give me some CA, but looking at the picture made with this scope (see user reports) I'm really impressed with the quality.

What do you think that suits my needs best (again, only visual observing), a 120 ED for 1700 euro or a 152 achromat for "only" 800 euro?


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Niklo
professor emeritus


Reged: 03/29/13

Loc: Bavaria
Re: Apochromatic or Achromatic does it really matter? new [Re: Maurice]
      #6076384 - 09/12/13 06:13 AM

Quote:

Hi all, I know this is an old thread but maybe you can help me out.
Currently I have an WO 80 ED scope. I'm really satisfied with it, but after using it a couple of years now I'm in the "need" for a larger refractor to be able to distinqush one nabula from the other in light poluted skies.

I don't do AP, so an ED looks perfect for my needs. I also want a refractor, I love the views they provide.
This one is on my wish list: http://www.teleskop-express.de/shop/product_info.php/language/de/info/p4688_T...

But recently I came across a 6" achromat: http://www.teleskop-express.de/shop/product_info.php?products_id=2229#ebericht

I know this scope will give me some CA, but looking at the picture made with this scope (see user reports) I'm really impressed with the quality.

What do you think that suits my needs best (again, only visual observing), a 120 ED for 1700 euro or a 152 achromat for "only" 800 euro?



Hi Maurice,
the 6" achromat shows much details on the moon but it's probably taken with a green filter. In the green light the 6" is probably better than a 5" ED in green light but without filter you'll see color fringe in the 6" and then the 5" ED should be *better*.
The 6" achromat is probably mainly for deep sky with lower magnification, or for watching the moon or sun with filters, and not a ideal *planet refractor*. Probably it'll work with filters on planets, too, but I don't know if it's good enough for you (I have to say, that I never watched through this 6").
Clear skies,
Roland


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Sasa
professor emeritus


Reged: 11/03/10

Loc: Ricany, Czech Republic
Re: Apochromatic or Achromatic does it really matter? new [Re: Maurice]
      #6076415 - 09/12/13 06:52 AM

Hi Maurice,

I had the two telescopes in hand (not exactly TS 120ED but Skywatcher ED120/900, my guess is that it houses the same optics). It is very hard to recommend one, it really depends on you preference.

The 120mm ED scope is very universal, it is capable of nice low power views but it is also very good on planets and observing at high magnifications.

But if your main target are just nebulae, as you write, TS 152/950mm Individiual is also very good choice. A friend of mine has it and we observed together one night. No planets or Moon, just DSO. I was however surprised by good quality of the optics. You could tell on globular clusters at power of about 180x that the stars were not that crisp as in my 100mm ED refractor, but the view was still very good - and how knows how much of this was just due to possibly worse seeing. The 150mm lens was also showing much more stars than my 100mm lens of course. This is in contrast with Skywatcher 120/600mm achromat that I was playing with couple of years ago. This one was not pleasing to my eyes on globulars already at power of about 80-100x. The Skywatcher was just a telescope for low power views. TS Individual is doing much better in this respect and works on DSO very well even at quite high powers.

So I would say, hard choice. If I were in your place I would probably choose ED120. Especially from light polluted sites, you can enjoy the planets and Moon as well in this scope even without filters.

Alexander


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Mark Costello
Post Laureate
*****

Reged: 03/08/05

Loc: Matthews, NC, USA
Re: Apochromatic or Achromatic does it really matter? new [Re: Maurice]
      #6076579 - 09/12/13 09:14 AM

Hi there Maurice. Since your experience is with an ED refractor and you're considering a larger ED or even larger achromatic refractor (achro), let me suggest that you look at a couple of your favorite heavenly objects with an achro before making your choice. I have and regularly use a 5"F6.5 achro (it's my only scope) on the moon, a few planets, and a lot of deep sky objects (DSOs). I "tune out" the chromatic aberration but if I look for it, I can see it on the moon (only at the edge), the planets, and brighter stars. It doesn't bother me, but many people don't like it and you might not want to put up with it.

All the best in making your choice.


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Jeff B
Carpal Tunnel
*****

Reged: 12/30/06

Re: Apochromatic or Achromatic does it really matter? new [Re: Maurice]
      #6076675 - 09/12/13 10:10 AM

Maurice:

If you have a mounting that can handle it, I can recommend a 6" f10 achromat as a great compromise between size, CA, spherochromatism, light grasp and large field of view.

They display low visible levels of CA at low to medium powers and the F10 stop is very "eyepiece friendly". You can also stop them down to 4 or 5 inches for high power work with greatly reduced CA.

I've had one in some form or another for decades. Just a wonderful and easy to use scope.

Istar makes a good one or you can try to snag a used Jaegers.

Jeff


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beanerds
sage


Reged: 07/15/08

Loc: Darwin Australia
Re: Apochromatic or Achromatic does it really matter? new [Re: Jeff B]
      #6077740 - 09/12/13 09:14 PM

Great discussions going on here , I am enjoying it .
Here is my 5c worth, it is this , a good achromat will show all that an APO will but with a bit of CA on the brighter objects , that's life .

I had a NG 127mm triplet last year and it was very good ( but heavy ) and I sold it to buy my Tak M210 , I missed the 127 so much that I grabbed an Istar 127mm f8 achromat and built a scope around that objective , ( see my 'viewing sessions with 127mm Istar achromat' thread here ) and it performs 98% as good as the 127mm triplet I take off 2% because of the small amount of CA , that's all , I do like its views .

Now , last Saturday night I took my Istar f8 along to our dark sky night for the first time and a big ( 20 inch ) dob owner came over for a look at Venus thru my achro and his first words was 'Is this thing a triplet ?' , 'No' I said only an achro doublet , woaw !! he said , 'will you bring this along next time and I will bring my 127mm TV APO along so we can do a side by side' .
I cant wait for that , it will be interesting and I will keep you all posted as to how it turns out .
That's very high praise , indeed for my lowely old 127mm Istar f8 achromat .

If you cant afford 3-6k for a 100-150mm APO , a well made achro will satisfy nicely if used within its limits .

ps. I do like that TS 150mm f950mm achro , nice clooking scope that would perform very well , I think .

Brian.


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Maurice
member


Reged: 04/19/07

Loc: Netherlands
Re: Apochromatic or Achromatic does it really matter? new [Re: beanerds]
      #6078207 - 09/13/13 04:20 AM

Thanks for all the good advise, really appreciated. But I'm a bit more confused now
Although the 152 achro seems a very good deal to me, I'm concerned about how good it will be as an allround scope, especially in light poluted skies and how easy or hard it is to handle.

Furthermore, the achromat is way havier than the 120 ED, so part of the money I'll save on the achromat needs to be spend on a heavier mount. I was considering an iOptron MiniTower (II or pro? That will be the next discussion) but I asume that's out of the question for the 152 achromat.

Hmmmmm.... Tough decision, luckely I have some time to think it over since I have to take care of my bank account first

Likely I will settle for the 120 ED, for now it seems to me the most practical and user-friendly scope of the two and coming from a 80mm I believe it will still be an noticeable step up. At least that is what I hope to achieve...

Boy o boy, I don't know anymore. Our hobby is all about making tough decisions

Btw, unfortunately I am unable to look through any of these scopes prior to purchase because they are not present on the star parties I visit and the shop that sells them is too far away from where I live to visit them.

Edited by Maurice (09/13/13 04:35 AM)


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Kunama
professor emeritus


Reged: 10/22/12

Re: Apochromatic or Achromatic does it really matter? new [Re: Maurice]
      #6078233 - 09/13/13 05:29 AM

If you're considering AP in the future I would suggest you get a 120mm ED scope rather than the 150 achromat. The biggest difference you will see will be on bright targets like Saturn, Jupiter, Luna, etc. You will also have a slightly wider view for clusters etc. The mount requirement for the 120 will be EQ5 equivalent or bigger, the 150mm will need EQ6 or bigger.

The 120ED will be fine on the iOptron MiniTower Pro but your AP options will be limited to short exposures due to field rotation when using an AltAz mount.

I am currently doing visual only and use a 120mm F7.5 (900mm fl) on a manual T-Rex mount and find that to be a fantastic setup for me.
My previous scope was a 150mm F10 Istar which is an excellent scope but does require an EQ6 mount as a minimum. The smaller diameter of my 120 is more than compensated for by the reduced extraneous colour of the better optical design (mine is a Tak TSA120 Super Apochromat)

Good luck with your choice.


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beanerds
sage


Reged: 07/15/08

Loc: Darwin Australia
Re: Apochromatic or Achromatic does it really matter? new [Re: Maurice]
      #6078234 - 09/13/13 05:31 AM

Yes Maurice , its a tough decision , I know but mate its your money .

Just to put into some sort of perspective down here is Australia , our 'Ice in Space' classifieds , our local astro web site and it has 2 x 120mm refractors currently for sale ,

#1 is an Orion 120mm f8.3 achro , ( great scope ! ) for $100 aud .

#2 is a no brand ( probably a North Group and another great scope ) 127mm f7.5 triplet for $1800 aud .

Take your pick ? , if I was just starting out the $100 achro would be awesome , that's what you originally asked ? $200 vrs $2000 ? , stick it on an Astro Tech Voyager alt/az for another $279 aud ( Brand new ) and you are away with a great scope .

The triplet will fit on the AT voyager ,,, just ! but it will be a pain to use because the triplet's are 2x the weight of the achro's and it will wobble horribly . ( I have owned both , see above ), so you would need a HEQ5 ? type mount or HD alt/az mount for an already $1800 scope ??? ,,, its your money mate , but for starting out I would personally ( If I needed another 127mm achro ) grab the $100 scope and AT mount for a total of $379 , and be very happy with that set up too.

Look 2nd hand , there are some awesome bargains out there , like these two I have just mentioned .

Brian.


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Niklo
professor emeritus


Reged: 03/29/13

Loc: Bavaria
Re: Apochromatic or Achromatic does it really matter? new [Re: Kunama]
      #6078269 - 09/13/13 06:23 AM

Hi Maurice,
the 6" 900 mm is very short so I think that the EQ6 is not a must. An Celestron ADM mount could be sufficient (haven't tested it) the EQ5 maybe a little bit too weak.
A 6" f/10 has a much longer lever arm and will require a more powerful mount than a 6" 900 achromat.

For the EDs there are cheaper versions of Skywatcher Equinox or Evostar ED 120/900. That could be an alternative that works well even for very high magnifications with an EQ5.

Cheers,
Roland


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Jon_Doh
scholastic sledgehammer


Reged: 09/16/11

Loc: On a receiver's back
Re: Apochromatic or Achromatic does it really matter? new [Re: Niklo]
      #6078429 - 09/13/13 09:41 AM

Maurice, I have a 152 achro and it does very well for nebulae. The CA is not bad at all on the moon. I see a very thin yellow line that disappears when I shift my eyes. The detail on the craters is excellent and free of CA. CA is worse on Jupiter but it can mostly be removed with a Baader Fringe Killer filter. This filter also helps focus the stars tighter and improves contrast on the planets. You should get one and screw it onto your diagonal.

The downside to the achro is that they are huge, not so heavy as bulky. Because of their length when viewing something like M57 which is right at zenith now you have to sit on the ground. The 120 may be somewhat better in terms of viewing angles, but basically that's the cost of a refractor over a dob or sct.


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