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AT72ED with AT2FF or AT65EDQ?

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#1 nine44

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Posted 26 March 2013 - 09:06 AM

Anyone have an opinion of how the Astro Tech 72ED with a Field Flattener (~$529) compares to the 65EDQ quadruplet (~$599) for AP? Which would you get?

#2 rflinn68

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Posted 26 March 2013 - 09:32 AM

No-brainer...AT65EDQ wins easily. 65 comes with some nice rings and a dovetail as well. AT65 also has the premium FPL-53 optics. To me they were basically the same money (once you got the rings, dovetail, flattener for the 72ED) and just the 7mm difference. Big thing for me was the FPL-53 optics. Absolutely love the AT65EDQ for AP!

#3 Jeff2011

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Posted 26 March 2013 - 11:44 AM

I went with the AT72ED, only because I was also going to use the field flattener on an AT6RC that I am planning on buying. Rflinn68 makes a good point though.

#4 rflinn68

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Posted 26 March 2013 - 11:56 AM

I went with the AT72ED, only because I was also going to use the field flattener on an AT6RC that I am planning on buying. Rflinn68 makes a good point though.


If I had already had rings, dovetail, and a field flattener, I would have bought the 72ED. I was starting from scratch and the AT65EDQ was just a much better deal overall. I've seen a lot of nice images from the 72ED.

#5 Jeff2011

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Posted 26 March 2013 - 01:04 PM

My VX mount and field flattener is on the way from Astronomics. After some orientation time with the mount, I look forward to getting some pics with it. In the mean time, I have been using a loaner mount from a friend to learn how to use an EQ mount. The 72ED is a lot heavier than I thought. I knew is was 5 lbs when I ordered it, but it seems heavier in person. It is a beautiful scope.

I had it out last night and was comparing the views through it against my 8 inch Dob. Of course the Dob out performed it, but I was impressed what that little scope could do. What was neat was that I had enough of a selection of eyepieces were I could get close on the magnification and field of view between the two scopes. When I pointed it at polaris which is farily light polluted for me, the Star resolution was about the same with the Dob view being brighter. The Dob really out performed the little scope when I viewed the Orion nebula which was in a darker part of my sky. But the view through the 72ED was still very good. Eventually I plan to piggyback it on an AT6RC and use it for both guiding and imaging.

#6 guyroch

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Posted 26 March 2013 - 01:15 PM

No contest, get the AT65EDQ!

I bought 2 for side-by-side imaging!

Guylain

#7 nine44

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Posted 26 March 2013 - 08:16 PM

Thanks folks--sounds like both are good, but at least two folks here seem to LOVE the AT65EDQ.

#8 zerro1

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Posted 26 March 2013 - 09:04 PM

I own an AT66ED and an AT65EDQ. The 66 is "what came before" the 72. The AT65 will give you better stars and better quality accross the field than the AT72 can even with a flattener. The AT65 is a true APO triplet with a fourth flattener element inside the tube. The ED's are doublets and refered to as "Semi-APO's". I still use the AT66ED because it has it's uses with a reducer/flattener but the 65 is much easier to do mosaics with since the field is so darn perfect.
example http://img23.imagesh...slrregistar.jpg

#9 james7ca

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Posted 27 March 2013 - 06:01 AM

You can now get an Astro-Tech 0.8X reducer for the AT72ED. That means you can convert the 430mm f/6 to a 344mm f/4.8. In fact, the reducer (which is supposed to also work as a flattener) is even less expensive than the simple AT2FF ($150 versus $120 for the new reducer).

Plus, going from the f/6.5 AT65EQ to the reduced f/4.8 AT72ED gives you almost one stop more "speed" but I suspect that the usable field on both would still be about the same (since the edges on the AT72ED aren't going to be that good, even with the reducer/corrector). Thus, on price they now compare as:

AT72ED with 0.8X Reducer: $500
AT65EQ: $599

Finally, while the AT65EQ comes with a set of rings, the AT72ED comes with a fairly nice aluminum-frame case.

It's a tough call, the AT72ED might be a little more versatile with the 0.8X reducer, but the AT65EQ will probably give you slightly better wide-field photos (but requiring a modest increase in exposure times).

Here are two sample of images of M101, one taken with an AT65EQ (listed first) and the other with the AT72ED with 0.8X reducer:

http://www.flickr.co...157632685509505

http://www.flickr.co...157628489113033

#10 guyroch

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Posted 27 March 2013 - 06:22 AM

The cost difference is not that much once you factor in the flatner for the AT72ED. So get the better scope... get the AT65EDQ and never look back.

Guylain

#11 nine44

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Posted 27 March 2013 - 07:07 AM

Thank you everyone! I think I'm going to go for the AT65EDQ. Speaking of flexibility, though (using a scope of one focal length and a reducer),--is there a resource that will help identify which objects require which FL for good imaging?

#12 terry59

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Posted 27 March 2013 - 07:16 AM

Thank you everyone! I think I'm going to go for the AT65EDQ. Speaking of flexibility, though (using a scope of one focal length and a reducer),--is there a resource that will help identify which objects require which FL for good imaging?


Get Ron Wodaski's CCD Calculator.

#13 hoa101

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Posted 27 March 2013 - 07:36 AM

You can now get an Astro-Tech 0.8X reducer for the AT72ED. That means you can convert the 430mm f/6 to a 344mm f/4.8. In fact, the reducer (which is supposed to also work as a flattener) is even less expensive than the simple AT2FF ($150 versus $120 for the new reducer).

Plus, going from the f/6.5 AT65EQ to the reduced f/4.8 AT72ED gives you almost one stop more "speed" but I suspect that the usable field on both would still be about the same (since the edges on the AT72ED aren't going to be that good, even with the reducer/corrector). Thus, on price they now compare as:

AT72ED with 0.8X Reducer: $500
AT65EQ: $599

Finally, while the AT65EQ comes with a set of rings, the AT72ED comes with a fairly nice aluminum-frame case.

It's a tough call, the AT72ED might be a little more versatile with the 0.8X reducer, but the AT65EQ will probably give you slightly better wide-field photos (but requiring a modest increase in exposure times).

Here are two sample of images of M101, one taken with an AT65EQ (listed first) and the other with the AT72ED with 0.8X reducer:

http://www.flickr.co...N03/8486379320/

http://www.flickr.co...157628489113033


With respect, you're asking him to compare to an AT65EDQ image that Dan knows had some issues with the mount and/or imaging train. I would compare to photos in which there were no such issues.

The AT65EDQ is better corrected in terms of color and the field is completely flat. The AT72ED with reducer is faster. Those are the points I would consider.

In my opinion though, you could buy a camera lens that is faster than either of them if you want fast optics.

#14 rflinn68

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Posted 27 March 2013 - 11:24 AM

The cost difference is not that much once you factor in the flatner for the AT72ED. So get the better scope... get the AT65EDQ and never look back.

Guylain


X10!! Dont even think about the case with a 72ED. Think about premium FPL-53 optics compared to the 72ED. The AT65EDQ comes with some really nice foam and I built a really nice case for mine in about 15 minutes using the shipping foam and some hinges and latches from the hardware store. The AT65EDQ is MUCH nicer IMO.

#15 nemo129

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Posted 27 March 2013 - 06:33 PM

My vote would be for the AT65EDQ as well. Better glass! :grin:

#16 Erskin71

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Posted 27 March 2013 - 07:31 PM

If it's not to late. I vote for the AT65. Bought one and never looked back.

#17 james7ca

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Posted 27 March 2013 - 11:57 PM

...It's a tough call, the AT72ED might be a little more versatile with the 0.8X reducer, but the AT65EQ will probably give you slightly better wide-field photos (but requiring a modest increase in exposure times).

Here are two sample of images of M101, one taken with an AT65EQ (listed first) and the other with the AT72ED with 0.8X reducer:

http://www.flickr.co...157632685509505

http://www.flickr.co...157628489113033


With respect, you're asking him to compare to an AT65EDQ image that Dan knows had some issues with the mount and/or imaging train. I would compare to photos in which there were no such issues.

The AT65EDQ is better corrected in terms of color and the field is completely flat. The AT72ED with reducer is faster. Those are the points I would consider.

In my opinion though, you could buy a camera lens that is faster than either of them if you want fast optics.

If you look at more of Dan's images you will see that his AT65EDQ is showing a consistent pattern of misshaped stars. So, I don't think it is the case of a transitory problem with his mount or something that went wrong on that particular night. He probably has a problem with his sample of the AT65EDQ, but it isn't apparent that he even recognized it as such until I mentioned it in a comment about his image of M101. I'd agree that his image probably does not represent the best that the AT65EDQ can do, but the same can be said of my image done with the AT72ED and the 0.8X reducer. But, if you can provide any samples or links I'd be very interested in seeing more comparisons (full frame or close, high resolution sensor and file, same subject, near same exposure and image scale, etc.).

However, I'm pretty happy with my initial results with the 0.8X reducer. In fact, if the star images near to the edges of the field were as good as the center half of the image then I think the balance (of favor) would probably have to go to the 0.8X reduced AT72ED (as a wide-field astrograph). But, the edges are not really that good so if edge-to-edge image quality with a very wide field at high sensor resolutions is your goal then the AT65EDQ should serve you better.

In any case, here is what the ad copy on the Astro-Tech 0.8X reducer says about its field correction (Astro-Tech ATR8 0.8X reducer/field flattener):

In addition to reducing the focal length of the telescope and thereby increasing the photographic speed, the ATR8 flattens the normal field curvature inherent in all refractors to provide images that are sharply focused out to the very corners of a large format DSLR chip. Stars look sharp and point-like all the way across the field in your images. You don't have to worry about photos that are sharp in the center and blurry at the edges.


That might be true if you were using a low-resolution CCD camera, but on my 16 megapixel APS-C camera the stars certainly aren't "point-like all the way across the field."

Two more things (even now that the OP has made his choice). Does anyone know whether the AT65EDQ will come to focus with a 2" star diagonal? I suspect that it might not, given that the product description specifically mentioned that you can use a 1.25" diagonal for visual use and that kind of suggests that the inward focus travel on the AT65EDQ is a little limited (i.e. a 2" diagonal may not work). Of course, that's not a problem with the AT72ED, since its primary reason for being is for visual use (whereas the AT65EDQ is designed as an astrograph).

Lastly, I don't think you could put rings on the AT72ED since the shape of the tube with its attached Vixen dovetail seems to preclude any reasonable arrangement of a set of tube rings. So, that's a potential problem if you really need to mount a large accessory (guidescope?) to the AT72ED. However, at the focal length that both of these scopes run at you might not even need to guide the exposures (as long as they are relatively short, I suspect that you could go up to a few minutes with any reasonably well adjusted equatorial mount).

So, in my final analysis which is better, the AT72ED or the AT65EDQ? It's kind of a toss-up, but if you are primarily interested in wide-field astrophotography then the AT65EDQ wins. However, if you want a bit more versatility, are doing a goodly amount of visual work, and can trade off a little bit of field coverage for an additional one stop in speed then the AT72ED with the ATR8 reducer might be the better combination (IMO).

P.S. if anyone has links to more wide-field, high-resolution comparisons between these two scopes then please add them to this discussion. What we need is something beyond the typical one megapixel (or smaller) images that you typically find on the internet.

#18 terry59

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Posted 28 March 2013 - 06:46 AM

That might be true if you were using a low-resolution CCD camera, but on my 16 megapixel APS-C camera the stars certainly aren't "point-like all the way across the field."

Lastly, I don't think you could put rings on the AT72ED since the shape of the tube with its attached Vixen dovetail seems to preclude any reasonable arrangement of a set of tube rings. So, that's a potential problem if you really need to mount a large accessory (guidescope?) to the AT72ED. However, at the focal length that both of these scopes run at you might not even need to guide the exposures (as long as they are relatively short, I suspect that you could go up to a few minutes with any reasonably well adjusted equatorial mount).



P.S. if anyone has links to more wide-field, high-resolution comparisons between these two scopes then please add them to this discussion. What we need is something beyond the typical one megapixel (or smaller) images that you typically find on the internet.


I've ben watching this thread but haven't joined because I have mixed feelings about my AT72ED. I have a number of images taken with it at my link below, some with a DSLR and the latest with my Atik 314L+. I have both the Orion field flattener and Orion 0.8x reducer. Unfortunately my skies haven't been great this winter or I'd have a lot more data.

I have gotten a few images with the DSLR where stars look great but not all of them are that way. I think the focuser is the problem area but until I am comfortable with that assessment it is hard for me to spend up for a Moonlite to validate it.

The imaging circle for my Atik is smaller and may be a good solution but I still need to work with the spacing and clear skies are rare so the two Rosette shots are all I have for now. I am encouraged so far.

I have a number of shots with the ED80 and flattener from both DSLR and CCD now so am comfortable that the flattener is not a problem. The recent horsehead is the only shot I have with the ED80 and 0.8x with the DSLR.

As it is now galaxy season I don't expect to do more with the AT72ED for a couple of months. If I can get it to work right, the AT72ED and 314L+ will see a lot of action later.

I took the foot off a long time ago. I use a pair of Orion 80mm tube rings. One fits fine and for the other I got a roll of nylon strapping at Wally World. A piece on the bottom and another on top make it fit snugly.

I have an ADM SBS setup for camera lens work with a ST80 on one side to see where I'm pointing. I just put the AT72ED on in place of the lens.

As always in this hobby, YMMV.

#19 rflinn68

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Posted 28 March 2013 - 01:34 PM

James7ca....I am not able to reach focus with a 2" diagonal with my AT65EDQ but it isnt designed for visual anyway. It is designed as an astrograph and marketed as such. Besides, is a 2" eyepiece even needed with that scope? Even with my 52degree afov Orion 25mm plossl eyepiece I still get a FOV of 3.095 degrees (17X) and 2.73 degrees with my ES82 14mm (30X). If one wanted a wider fov than that binoculars would seem the way to go. I just tried it when I first got the scope just to see if it would work, but I rarely ever look through the scope anyway so its not an issue. It really is a nice widefield astrograph and I get a 2 degree X 3 degree image scale with my Canon 1100D.

#20 james7ca

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Posted 28 March 2013 - 05:05 PM

I wouldn't see a NEED for a 2" eyepiece for the AT65EDQ but I mentioned it in case someone already had some 2" visual accessories that they wanted to use.

As for the field coverage you get on the AT65EDQ (3 degrees by 2 degrees), with the 0.8X reducer on my AT72ED I get 3.9 degrees by 2.6 degrees edge-to-edge with my Sony NEX-5N, but the stars beyond the central 2.6 degrees square aren't really that good. So, the diagonal coverage over a "good" field comes out to be 3.6 degrees with your AT65EDQ versus 3.7 degrees with the AT72ED (or if you can tolerate some misshaped stars a very wide 4.7 degrees on the full diagonal).

I'm surprised there is that much difference, but the Sony camera has a slightly larger sensor than your Canon so there is a bit of a "cheat" in my calculations for the AT72ED. Given the above, I'd say they are about equal on field coverage. However, the AT65EDQ would have a larger image scale (better) while the AT72ED would be almost one stop faster (better for some).

Here is a link that shows the performance of the AT72ED with the 0.8X reducer over a 2.6 degree x 2.6 degree square field of view.

http://www.flickr.co...age/8484453841/

I think it looks pretty good, even considering the blue halo around Polaris (which would be a fairly bright star to appear near to a DSO and this image also had a significant color saturation boost to make the stars "pretty"). When I photograph bright red stars with this combination I get red halos so I think some of this color is just light scatter and flare, not plain chromatic aberration. Yes, I'm splitting hairs and making excuses but frankly I think the AT72ED is still a pretty nice telescope for the money.

#21 james7ca

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Posted 28 March 2013 - 05:26 PM

...I took the foot off a long time ago. I use a pair of Orion 80mm tube rings. One fits fine and for the other I got a roll of nylon strapping at Wally World. A piece on the bottom and another on top make it fit snugly....

Does that mean you have one ring around the front of the optical tube (i.e. the largest point of the diameter) and one ring around the smaller diameter rotatable focus collar? That would work but it would mean that you couldn't easily rotate the focuser and you'd be attaching the rear ring to a part of the tube that isn't solidly attached to the objective (if would be tight, I'm sure, but it mighty also cause a tilt in the focal plane -- not at all likely, but still something of a possibility particularly if the collar was at all loose).

As I mentioned earlier, putting rings on the AT72ED isn't a straightforward task and thus probably counts as a negative.

In any case, thanks for the information on the AT72ED, but it seems that I'm the only one in this thread that likes the chances with that scope.

#22 james7ca

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Posted 29 March 2013 - 03:52 PM

Here are some more threads discussing AT72ED and the AT65EDQ.

Discussion about using a 2" star diagonal with the AT65EDQ (comes to focus with some 2" eyepieces, but you may need to use a special, short focus type prism diagonal to work with most):

http://www.cloudynig...5496817/Main...

Review on the AT66ED (early relative to the current AT72ED):

http://www.cloudynig...hp?item_id=2056

#23 Jeff2011

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Posted 29 March 2013 - 11:35 PM

In any case, thanks for the information on the AT72ED, but it seems that I'm the only one in this thread that likes the chances with that scope.



No, you are not the only one. Thanks for posting a link to your pics. It will gives me an idea of what to expect. I just got my mount in so I am still a ways from actually getting some pics. I have been looking for scope rings and I see what you mean about it being difficult. The tube OD is an odd size.

#24 james7ca

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Posted 30 March 2013 - 03:36 PM

In any case, thanks for the information on the AT72ED, but it seems that I'm the only one in this thread that likes the chances with that scope.



No, you are not the only one. Thanks for posting a link to your pics. It will gives me an idea of what to expect. I just got my mount in so I am still a ways from actually getting some pics. I have been looking for scope rings and I see what you mean about it being difficult. The tube OD is an odd size.

The problem with using mounting rings is that the tube has three different sections with three different diameters as you move from the front to the back. Ideally, you'd need two different sized rings unless you want to use the type that has the adjustable tensioning screws. Moreover, the rear section is the rotatable collar and I'm not certain that you'd want to mount rings on that part of the tube.

#25 Jeff2011

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Posted 30 March 2013 - 08:49 PM

Yes there are three parts. The dew shield, the main tube and rear rotating section. I would think that I would only want to mount the rings on the main tube which is 87mm OD. I think Agena Astro has some that are close. 3.5 inch rings they say fits 88 to 90mm. Astronomics has astro tech rings with the adjustable screws, but I would be concerned that they might put marks or dents on the tube. If I went with the Agena astro ones, I would probably have to line them to get a tight fit.






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