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Small achro/semi apo recommendation?

refractor equipment imaging
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#1 Bowlerhat

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Posted 11 July 2019 - 11:35 PM

I've narrowed down my list to either:

1. Skywatcher evostar 72ED

2. Svbony/aquila/yuzhong 90mm f5.5 achro refractor

 

My reasoning is as follows:

1. Light and compact as grab and go

2. 70mm is the minimum and the 90mm is the max for the aperture. I'd have a scope that bigger than 90mm as a stationary scope.

3. 500AUD budget. the 500USD scopes such as Televue pronto, WO Zenithstar, Vixen, TS optics or Explore scientifics fall beyond my budget, especially after the new 10% import tax.

4. better build than usual achromats

5. double crayford focuser as standard feature

 

I'm using it as a starter setup for photography and visual. CA wise I'm not that bothered since I'm not using it for high power, but as a wide field sweeper-as it's also possible to remove fringing with post processing. I'm aware that 90mm is achro, but seems it has good reviews for it's price with less CA. I have 80mm short tube, so I hope the optics of the 72ED can compensate the aperture loss. As I'm starting I don't want to spend thousands for triplet or a large ED.

 

Which one would be the better option?

 



#2 db2005

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Posted 12 July 2019 - 02:02 AM

Unless your main observing targets are specifically faint objects, I'd take the 72ED in a heartbeat, but maybe that's just me.

 

Here's my line of reasoning: It's smaller, lighter, easier to mount, acclimatizes faster and fits the description of a grab-and-go scope perfectly. And, in my experience, sharp ED optics make up for some of their aperture deficiency on account of providing sharper and very high-contrast views. I'm also guessing QC is likely to be better and more consistent with the Skywatcher. And since (according to your signature) you already own 70 mm and 80 mm f/5 achromats it would make little sense to get yet another fast achromat; IMO you should take the plunge and get a taste of how well a good ED scope performs; it's more than likely to outperform your 50, 70 and 80 mm achromats.

 

Just my 2 cents.


Edited by db2005, 12 July 2019 - 02:02 AM.

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#3 Cirus

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Posted 12 July 2019 - 02:24 AM

I have heard that the 72ED can have inward focusing issues for visual use, I'm not sure how it can be overcome.

#4 sg6

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Posted 12 July 2019 - 02:26 AM

As you say:

"I'm using it as a starter setup for photography and visual."

Then it has to be the 72ED, You may not be overly bothered by CA but the camera will be.

 

Would have said the 72ED anyway as it will produce the better views, that alone will counter to an extent the loss in aperture - the eye operates on contrast as well as simple brightness.

 

Problem it seems with Aus is the limitation on available astro equipment.


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#5 Cirus

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Posted 12 July 2019 - 02:32 AM

Ozscopes have a Saxon 80/600ED for $800aud

I have not heard any reviews of this scope but it sounds like it could also be a decent option.

Most Saxon products are made my Synta, same manufacturer as Skywatcher.

#6 Bowlerhat

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Posted 12 July 2019 - 03:02 AM

Is it going to be really different between 72ED or 80ED? I was considering that option as well, but I had a chance to actually inspect the 72ED. I really like the size and the weight, considering it's smaller than my st80. With the 800AUD price I feel I rather put a bit more to around 1000AUD at that point. With current price difference, I'll save it to buy accessories, perhaps a good diagonal with it.

 

I never heard of infocus issue. However I think with ED I'd prefer to use it for photography because it has the edge on sharpness. I'd still have my achromat for visual use anyway.

 

I think it's maybe rather weird to get a small achromat, but if I do I think that'll replace my 80mm. I just like the idea of having a heavier, solid build. But may not worth it at all considering the optics and too small aperture difference..



#7 Jon Isaacs

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Posted 12 July 2019 - 03:10 AM

I think it's maybe rather weird to get a small achromat, but if I do I think that'll replace my 80mm. I just like the idea of having a heavier, solid build. But may not worth it at all considering the optics and too small aperture difference..

 

Just put a 2 inch focuser on the ST-80... 

 

With astro-photography on the menu, I see no reason to spend money on an achromat..  

 

Jon



#8 Bowlerhat

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Posted 12 July 2019 - 03:57 AM

Jon, to be honest you read my mind. I think so too before, would be more reasonable than just buying a 90mm because of the tube.

 

I've decided. I think I'd try the 72ED, but solely because of refined glass for better color correction. I'll give it more time to consider the 80ED. Thank you for your recommendations.


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#9 db2005

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Posted 12 July 2019 - 04:22 AM

I my own personal experience, any good 80 mm ED like the SW ED80 f/7.5 will outperform all of your scopes in your current signature (including your 114mm Newt.), with the possible exception of the C5. And I'm pretty sure the ED will give even the C5 pretty fierce competition on many targets under typical seeing conditions due to its better contrast and sharpness.

 

An 80mm f/7.5-f/8 ED/APO is a very nice place to be for grab-and-go observing.


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#10 Bowlerhat

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Posted 12 July 2019 - 05:25 AM

I rarely used my 114 newt since it sits in old man's home. I feel rather uncomfortable spending that amount however because it doesn't come with a double speed crayford, so I'd need an upgrade. Adding that the amount is around a thousand bucks, and on that limit I'd be looking at other scopes than only that one, and it's already double the amount I was intending to spend.



#11 Ed D

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Posted 12 July 2019 - 07:19 AM

I have owned an AT72ED since they first came out and have done a lot of observing, as well as AP in the past few years.  I have taken the 72mm ED to Everglades National Park at the tip of the Florida peninsula where I can see down to -62*.  Some of my most memorable views are The Wishing Well Cluster, Eta Carinae, Omega Cent, etc.  I have also used the 72mm ED in the past few years to image from my back yard in Miami (Bortle 9 severe LP) and have gotten incredibly good results.  I have also used achros in various sizes that I used to own and have done side by side comparisons both visually and imaging.  Especially imaging, the results between achros and EDs are leagues apart.  The ED can image fainter stars compared to achros with larger aperture, which BTW had what is reputed to be good glass.

 

I believe you will find the 72mm ED to be very handy and easy to use.  You will also find it to be very friendly to mount, especially for imaging.  With the AZ GTi you will get field rotation, but you can certainly start imaging with it.  If you consider upgrading to a GEM for AP the 72mm ED can be used on something like a CG-5 with good results and not break the bank, and will be light enough that you will use it often.

 

I believe the 72mm ED will meet the criteria you stated in your post #1 very well.

 

Ed D


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#12 Ed D

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Posted 12 July 2019 - 07:47 AM

I also have the ATR8 field flattener / .8x focal reducer for my AT72ED, which should work equally well with the Skywatcher 72mm ED.  The ATR8 changes the focal length of the AT72ED from 430mm to 344mm, giving wider fields for imaging.

 

I am attaching a couple of images taken through the AT72ED, as well as one taken through a 102mm f/6.5 achromat, so you can judge for yourself.

 

M13 Hercules Cluster 2017 07-14.jpg

M13 Hercules Cluster.  Taken through the AT72ED with ATR8, using an ASI290MC camera.

 

Orion Nebula 2018 12-18 JPEG.jpg

Orion Nebula.  Taken through the AT72ED with ATR8 using an unmodified Canon T3i DSLR.  BTW, I like B&W photography.

 

Orion Nebula 2018 01-31.jpg

Orion Nebula.  This one was taken through a 102mm f/6.5 achromat.  I include it so you can judge for yourself what an achro can and cannot do.

 

Ed D


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#13 peleuba

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Posted 12 July 2019 - 08:14 AM

I've narrowed down my list to either:

1. Skywatcher evostar 72ED

2. Svbony/aquila/yuzhong 90mm f5.5 achro refractor

 

 

 

Not on your list, I know, but perhaps consider the Synta ED80.   You can get one for less then $500.

 

I have tested several of these, and a long time observing friend has thoroughly tested another and they have all been fantastic lenses.  


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#14 oldstargazer

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Posted 12 July 2019 - 10:13 AM

Is it going to be really different between 72ED or 80ED? I was considering that option as well, but I had a chance to actually inspect the 72ED. I really like the size and the weight, considering it's smaller than my st80. With the 800AUD price I feel I rather put a bit more to around 1000AUD at that point. With current price difference, I'll save it to buy accessories, perhaps a good diagonal with it.

 

I never heard of infocus issue. However I think with ED I'd prefer to use it for photography because it has the edge on sharpness. I'd still have my achromat for visual use anyway.

 

I think it's maybe rather weird to get a small achromat, but if I do I think that'll replace my 80mm. I just like the idea of having a heavier, solid build. But may not worth it at all considering the optics and too small aperture difference..

Doing AP you will love the 72ED because the camera will capture the photons over time that a larger lens will give your eye instantly. So visual you can use some of the larger stuff you already have and for AP the 72ED will give you what you are currently missing, wide angle capture ability for the big objects without the bad artifacts.

 

I have large glass short tubes but are not ED and tried to get some pictures of the objects that they let me see but the camera just captured too much of the bad stuff the lens created. Finally got an 80ED for a good price and while visually it was pretty poor compared to the larger glass, when the camera is mounted on it there is no comparison. The small scope makes it so much easier to get setup and ready to go. Less weight means you need less counter weight and so now I can carry the mount out with weight already attached, nice to be able to save a trip back inside the house for equipment.


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#15 kmparsons

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Posted 12 July 2019 - 02:19 PM

I do not own the AT72ED, but I do have the AT60ED and the AT92 f/5.5, both of which are so good that I would not hesitate to endorse the AT72ED for visual (I do not do AP). It should be compact enough to keep set up in a corner as your grab 'n' go. If you travel, it should fit easily in carry-on luggage. 



#16 Bowlerhat

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Posted 12 July 2019 - 07:02 PM

Yeah, the reason why I consider 72ED is because I went to the store and they actually let me inspect it. Picking it up I can feel it's really light and I'm sold with the built. They also showed me the 102mm APO esprit - it seems to be really heavy.

 

On the star party two days ago, they mounted up a 127ED, side by side by a 127mm mak, and 6" dob too. The ED is sharp as mak, no fringing at all, I was impressed.

 

But I don't want to jump ship yet so I'm thinking the smaller ED. 80ED cost with double crayford is double the price of 72ED with the same focuser. Also, the guy on the store told me that technically you can mount the focuser to the 80mm achro as well, so with that price, it's more than enough for a win-win for me.



#17 MortonH

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Posted 13 July 2019 - 06:28 AM

If you haven't already joined, sign up to the Australian forum Ice in Space and place a wanted ad for a used 80ED and save some money.

 

www.iceinspace.com.au/forum


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#18 Jeff B

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Posted 13 July 2019 - 10:48 AM

Not on your list, I know, but perhaps consider the Synta ED80.   You can get one for less then $500.

 

I have tested several of these, and a long time observing friend has thoroughly tested another and they have all been fantastic lenses.  

I can certainly second that.  Mine is an optical jewel and there are plenty of aftermarket focusers to choose from if you want to upgrade.

 

Shoot, I even made my Orion 80ED "bino-friendly".

 

And please, no wise cracks about the peeling paint.

 

Jeff

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#19 Brollen

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Posted 13 July 2019 - 11:07 AM

+1 on SW72ED

 

I have had one for almost 1 year now and love it. One of the best corrected fast scopes I have looked through with sharp contrasty views. It has a nice focuser and I haven’t had any issues with focuser travel using both 2” and 1.25” diagonals. 


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#20 barbie

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Posted 13 July 2019 - 05:17 PM

I briefly had a Skywatcher 72ED shortly after they first came out and I will also add my endorsement for this fine scope. The only reason I sold mine was because I got a classic Takahashi FC76. The 72 ED

is very nicely made and corrected well.


Edited by barbie, 13 July 2019 - 05:18 PM.


#21 pdxmoon

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Posted 13 July 2019 - 09:27 PM

If you want true portability and great glass, have a look at the AT60. It is superb, and it weighs something like 3.5 pounds. I haven't done any astrophotography with it, so others can speak to that, but it rides on a tripod if you wish, and for visual for me it has been a magnificent scope.

 

The new AT72II is an upgrade of the AT72. I have the original ED and have loved that scope.


Edited by pdxmoon, 13 July 2019 - 09:28 PM.

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#22 aa6ww

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Posted 16 July 2019 - 01:43 AM

What 2" diagonal are you using and what 2" eyepieces have you used with that diagonal?

 

.. thanks

 

...Ralph

 

+1 on SW72ED

 

I have had one for almost 1 year now and love it. One of the best corrected fast scopes I have looked through with sharp contrasty views. It has a nice focuser and I haven’t had any issues with focuser travel using both 2” and 1.25” diagonals. 




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