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Explore Scientific AR102 OR Astro-Tech AT102ED

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#1 KTAZ

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Posted 18 May 2020 - 05:52 PM

Looking into my first refractor purchase. Will be dual use for both visual and my introduction to AP.

 

Any thoughts on how these 2 compare would be appreciated.

 

 


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#2 MalVeauX

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Posted 18 May 2020 - 05:56 PM

Heya,

 

Absolutely zero reason to get the E.S. AR102 as an achromatic doublet that is too fast for color correction if you want to image.

 

The AT102ED is a much, much, much, much, much better scope visually and for imaging in every way, literally. By far.

 

Before you buy anything, I highly suggest you take several steps back and become very well acquainted with telescope optical designs and what everything means before you even think about buying gear for AP. Not trying to be rude or cheeky, so sorry if this sounded harsh. But the comparison is not even a comparison, one is significantly inferior completely in all ways possible (The AR102) due to it's design (fast achromatic doublet).

 

Very best,


Edited by MalVeauX, 18 May 2020 - 06:03 PM.

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#3 Toddeo

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Posted 18 May 2020 - 05:58 PM

The ES AR102 is not an "ED" scope. The color will drive you nuts!  The AT102ED is just that- A 102ED scope. Everything is better on the AT102ED.


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#4 KTAZ

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Posted 18 May 2020 - 06:35 PM

Heya,

 

Absolutely zero reason to get the E.S. AR102 as an achromatic doublet that is too fast for color correction if you want to image.

 

The AT102ED is a much, much, much, much, much better scope visually and for imaging in every way, literally. By far.

 

Before you buy anything, I highly suggest you take several steps back and become very well acquainted with telescope optical designs and what everything means before you even think about buying gear for AP. Not trying to be rude or cheeky, so sorry if this sounded harsh. But the comparison is not even a comparison, one is significantly inferior completely in all ways possible (The AR102) due to it's design (fast achromatic doublet).

 

Very best,

Not cheeky at all...I understand the construction difference between the two. The knowledge that I lack is from a practical use perspective; I have no idea what the real world difference between those two optical designs, as well as their glass composition, actually translate into both from an imaging and AP standpoint. Better to ask folks that have experienced them.

 

Tough to look through a few when every star party until the fall is pretty much cancelled...

 

I appreciate your feedback!


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#5 Dereksc

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Posted 18 May 2020 - 06:53 PM

I have an AR127 that I purchased about 5 years ago - it was on sale for the same price that the AR102 is on sale now. I have been pleased with the visual performance of the telescope and have used it for some narrow band  AP. Chromatic aberration is apparent on LRGB images so I don't use it for that. One other issue with the AR127 is the crayford focuser which can slip when holding heavy AP equipment with the scope pointed towards the zenith. 

 

I'm not saying you should buy the AR102, I am just relating my experience with it's big brother. 

 

Here is an SHO image using the AR127 (click on the Astrobin thumbnail for higher resolution image and capture details):

 

get.jpg?insecure

 

Regards

 

Derek


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#6 MalVeauX

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Posted 18 May 2020 - 07:35 PM

Not cheeky at all...I understand the construction difference between the two. The knowledge that I lack is from a practical use perspective; I have no idea what the real world difference between those two optical designs, as well as their glass composition, actually translate into both from an imaging and AP standpoint. Better to ask folks that have experienced them.

 

Tough to look through a few when every star party until the fall is pretty much cancelled...

 

I appreciate your feedback!

All good!

 

So the AR102 as an achromatic doublet that is fast (F6.5) will have a lot of chromatic abberation (CA) which will rob you of contrast and mask stars and other bright objects of their detail by putting a purple halo around them. This is significant when it comes to AP and quite visible visually too, but it's really pronounced in AP especially if you image in color and push saturation (which literally everyone does). Narrowband can largely eliminate most of this problem because it filters each wavelength series and blocks the rest and focuses at different points in each wavelength, but that setup is significantly more expensive to go with mono & narrowband HaS2O3 or similar, or even RGB frankly. Note the following chart, the 102mm at F6.5 is pretty significant with CA and would take a focal-ratio of F11 or F12 to be similar to the F7 ED version. The ED glass makes that big of a difference.

 

ChromaticAbberation_Chart.jpg

 

The AT102ED will have minimal CA visually, to none on most subjects, and for imaging will have only trace amounts on the brightest of objects. It's significantly better in all ways, especially when it comes to chromatic abberation via color correction from the superior ED glass it uses along with the longer focal-ratio.

 

Even better would be a SkyWatcher 102mm F9 ED that uses FPL53, it would have literally no CA visually nor imaging. Or a slightly smaller 80mm or 72mm F6 with FPL53 for imaging, would also have virtually no CA and be superior to the AR102 for this purpose, especially for imaging.

 

Very best,


Edited by MalVeauX, 18 May 2020 - 07:38 PM.

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#7 Jaimo!

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Posted 18 May 2020 - 09:19 PM

I have had both.  I upgraded to the AT102ED and it was well worth the effort (selling the AR102 to raise the cash), for all of the reasons given above.  I have not regretted getting rid of that scope once I had the AT102ED.


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#8 CollinofAlabama

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Posted 19 May 2020 - 01:32 AM

I’ve done some comparison testing on my C102GT (100mm F/10 doublet achromat) versus my AT80ED after Sarkikos (Mike) said the 80mm ED was much better.  Still haven’t purchased the Baader semi-APO filter for it, yet, but I can say, definitively, that on crescent Venus, and I bet on Jupiter, Saturn and Mars later this year, that the chromatic aberration is significantly more destructive, visually (and almost certainly for AP — something I don’t do), than the view thru the AT80ED (and SkyWatcher 72ED, and 102 Mak).  The AT102ED uses FK-61 (Chinese clone of the Japanese FPL-51 glass), which will have a bit of residual red on a target like Venus, but honestly, it’s still a WHOLE lot better than what my F/10 achromat can display, at least on Venus, and I suspect the brighter planets.   Not so noticeable on double stars, and the extra aperture of the C102GT is definitely better for DSOs and tight doubles compared to the AT80ED, but compared to the AT102ED would have no real advantage.  And all this is just visual, mind you.  If a crescent Venus or Jupiter-Saturn-Mars opposition AP is on your agenda, there is no choice.  The AT102ED would have it all over even an F/10 achromat, but an F/6.5?  Easy choice.  Get the ED glass.  It’s a BIG step up.


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#9 russell23

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Posted 19 May 2020 - 07:52 AM

With a 4" f/6.5 achromat you will lose a lot of sharpness and contrast.  That is also the case for deep sky objects.  Fainter stars near the limits of detection are blurred out of visibility in an achromat.  I have the AT102ED and there is very little visible CA.  On the Moon you will see a little and a tiny amount on Jupiter.  It is an extremely sharp scope.

 

In terms of the OTA build, the AT is excellent.  Very rugged and smooth focuser and a real nice finish on the OTA.  I have not owned an ES scope before, but have read on these forums about more issues with the focusers, in particular, on the ES refractors.

 

I'd go with the AT102.


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#10 Jaimo!

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Posted 19 May 2020 - 08:18 AM

Also the dew shield on the ES AR102 looks a little goofy...

 

The AR102 has a couple of nice features, the rings with the handle on top, comes with a finderscope (useless) and diagonal (nice), and the focuser is not better or worse than the AT102ED.

 

While the package cost of the AR102 is similar to the AT102ED, which you will have to supply your own diagonal and finder, the AT102ED is a class above.


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#11 SeattleScott

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Posted 19 May 2020 - 08:36 AM

I have owned the AR102 and a couple 4” EDs. The reason to get the AR102 is because it goes on sale for $300 instead of $600 plus diagonal and finder. The AR102 is a good low/medium power visual DSO scope, capable of 4 degree FOV. However it struggles on brighter stars and planets, and even DSO get soft above about 100x. Personally I thought the finder was rather good, still have it, but it really is a poor match for that particular scope.

I did try doing some EAA with the AR102. This is sort of like AP with extremely short exposures, like 10 seconds. While the images were usable I preferred the Apo instead due to better CA correction.

Scott
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#12 Jon Isaacs

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Posted 19 May 2020 - 06:40 PM

I owned the Original AT-102ED for about 2 years. I also purchased the AR-102 when it was special for $300 even though I had a premium 4 inch APO.. Blame the CN Refractors for that, I had to know what all the hullabaloo was about.  :)

 

For $300 with a diagonal, it was a good 4 inch achromat. Good optics, nice Focuser but the chromatic aberration was significant, to be expected.

 

The AT-102ED is a much better scope. It is very well made with a nice two speed rack and pinion Focuser. Optically it shows some chromatic aberration but only on bright objects, it's about 1/4 that of the AR-102.

 

Jon


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#13 KTAZ

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Posted 20 May 2020 - 10:27 AM

So I am clearly close to pulling the trigger on the AT102ED, but now am wondering about the Sky-Watcher Evostar PRO 100. The package comes with a 2” diagonal, 2 eyepieces, and a case, which puts it right in line cost-wise with the AT.

 

The question is which would be preferred from an AP perspective. The SW is a 900mm f/9 versus the 714mm f/7 of the AT.

 

Thoughts?



#14 russell23

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Posted 20 May 2020 - 11:15 AM

So I am clearly close to pulling the trigger on the AT102ED, but now am wondering about the Sky-Watcher Evostar PRO 100. The package comes with a 2” diagonal, 2 eyepieces, and a case, which puts it right in line cost-wise with the AT.

 

The question is which would be preferred from an AP perspective. The SW is a 900mm f/9 versus the 714mm f/7 of the AT.

 

Thoughts?

My experience with a SW120ED and the AT102ED is that the color correction is better in the SW and the OTA build is better in the AT.  If you are doing astrophotography you would probably want to upgrade the SW100 focuser.  That is a very significant cost to upgrade to a Moonlite or Feathertouch focuser suitable for AP.  With the AT you should not need a focuser upgrade.  
 

In addition, the diagonal provided with the SW is very pedestrian and the eyepieces are good, but nothing special.  The only real upgrade the SW100 provides is in the lower dispersion ED glass.  
 

I am not bashing the SW here.  I love my SW120ED.  It has a perfect star test and has been a great scope.  But a focuser upgrade was necessary and it was very obvious the stock diagonal had more scattered light than my AP and Vernonscope Star diagonals.  


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#15 Auburn80

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Posted 20 May 2020 - 11:19 AM

For a given camera, the SW will have a more narrow fov (larger image on the sensor) and be more dim with the same exposure time. That means exposures will need to be longer and/or more subs stacked. The image scale will also be more demanding of your mount in tracking and stability. Not saying it can't be used, just that it will require more effort on your part. Also, CA will be less visible in the SW images due to its glass selection. APers in general choose faster f ratios, even compressing f7 scopes down to f5.8 or less. One could reduce the SW too but the final f ratio would still be higher; something like f6.3 to f7.2 with a .7 - .8 reducer.

Edited by Auburn80, 20 May 2020 - 11:23 AM.

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#16 SeattleScott

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Posted 20 May 2020 - 05:51 PM

Really neither are really that good for AP. The SW is too slow and could use a focuser upgrade for heavy AP gear. The AT has more CA than you would want for long exposure AP. Do people use them for AP? Sure, either can work. But if the plan really is AP then a smaller 80mm triplet or FPL53 doublet would seem preferable,

Scott
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#17 stevew

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Posted 20 May 2020 - 07:53 PM

Also the dew shield on the ES AR102 looks a little goofy...

 

That's an understatement..

I can't believe someone intentionally designed it to look like that.


Edited by stevew, 21 May 2020 - 12:04 AM.

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#18 SeattleScott

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Posted 21 May 2020 - 12:23 AM

I think the idea is you can store it vertically and not worry about it falling over even if you live on the San Andreas Fault.
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#19 KTAZ

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Posted 21 May 2020 - 08:25 AM

Really neither are really that good for AP. The SW is too slow and could use a focuser upgrade for heavy AP gear. The AT has more CA than you would want for long exposure AP. Do people use them for AP? Sure, either can work. But if the plan really is AP then a smaller 80mm triplet or FPL53 doublet would seem preferable,

Scott

I understand that these may not be excellent choices; $600 versus $1600 buys a lot of quality difference. But I have to start somewhere!

 

I'm curious why an 80mm would be preferable to a 100mm. Are you referring to the ability to get a better build quality at a similar price point? Or are there other tangible reasons for using the smaller OTA for AP? Maybe a bit faster with less need for correction?



#20 SeattleScott

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Posted 21 May 2020 - 12:28 PM

I was just thinking an 80mm with better glass would be similar in price to the 4” with lower grade glass.
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#21 Chesterguy1

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Posted 21 May 2020 - 01:29 PM

Like russel23, I upgraded my SW120 focuser--a weak link. Otherwise a great scope for the money. Both the SW100 and the AT 12 show up regularly on CN Classifieds and AM.

 

Chesterguy



#22 airbleeder

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Posted 21 May 2020 - 06:07 PM

Looking into my first refractor purchase. Will be dual use for both visual and my introduction to AP.

 

Any thoughts on how these 2 compare would be appreciated.

  I have the AR102 and am pleased with it considering it's an achromat. I also have an ES ED102-01 triplet and am very pleased with it. No false color. Pinpoint stars and the rack&pinion focuser is super smooth and easily handles an ES 34mm 68* eyepiece. You might want to consider it.



#23 Jethro7

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Posted 21 May 2020 - 06:32 PM

Looking into my first refractor purchase. Will be dual use for both visual and my introduction to AP.

 

Any thoughts on how these 2 compare would be appreciated.

Hello Katz, 

Everyone has given you sound advice. I just bought a used like new AT 102 ED. I will get it next week sometime. Do I think it will perform like my ES100 Esprit,  NO but all the reviews on the AT102ED have been very complimentary and owners of this telescope are fond of them.

I will be able, weather permitting, to do a star test soon. I have been iching to get a grab and go telescope and a light mount like a ES twillite 1 to haul around with me and this little scope seemed just the ticket. There are plenty of times I've been out and about and wished I had a telescope rig at hand. And now I will.

 

"HAPPY SKIES AND KEEP LOOKING" UP Jethro


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#24 Jethro7

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Posted 21 May 2020 - 06:42 PM

That's an understatement..

I can't believe someone intentionally designed it to look like that.

The Explore Scientific dew shields make their telescopes look like a old time bug sprayer.The designers did not have a eye for aesthetics


Edited by Jethro7, 21 May 2020 - 06:45 PM.

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#25 KTAZ

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Posted 22 May 2020 - 08:39 AM

Hello Katz, 

Everyone has given you sound advice. I just bought a used like new AT 102 ED. I will get it next week sometime. Do I think it will perform like my ES100 Esprit,  NO but all the reviews on the AT102ED have been very complimentary and owners of this telescope are fond of them.

I will be able, weather permitting, to do a star test soon. I have been iching to get a grab and go telescope and a light mount like a ES twillite 1 to haul around with me and this little scope seemed just the ticket. There are plenty of times I've been out and about and wished I had a telescope rig at hand. And now I will.

 

"HAPPY SKIES AND KEEP LOOKING" UP Jethro

I look forward to hearing your first light results, Jethro!

 

For me, first impressions often reveal more than several years of use.


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