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DPAC Test - Astro-Tech AT152EDT, F8 Triplet

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#1 Jeff B

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Posted 18 October 2020 - 01:47 PM

An astro buddy of mine Allen, along with his wife Cindy, took a day trip to my house to pick up his APM 152ED doublet he sent to me for testing a few months back.  He brought along his new Astro-Tech AT152EDT, F8 triplet for DPAC testing.

 

And we were so busy, I forgot to take pictures of it but it looks just like it does in the ad pictures.  This is a very robust scope with a nice smooth focuser, and a removable section for imaging which also makes it "bino-friendly".  Checking the focuser collimation with a 152mm mask on the objective showed the laser going right through the center hole, even when the focuser was racked in and out.  Allen said the view through his Cheshire shows all of the reflections from the aft faces of the three elements lined up on top of each other.  It's a bit of a beast, but well made.  My TEC 160ED weighs perhaps 2-3 pounds less.

 

So, how did it do?

 

Quite well in DPAC.  Keeping a single Ronchi line centered as we swept though focus showed not clocking of the lines at all indicating, at least on the bench, no visible astigmatism.

 

First, full aperture color montages, with the inside of focus images on top, the outside of focus images on the bottom. 

 

Jeff

Attached Thumbnails

  • AT152ED, Full Aperture, Inside, Montage.jpg
  • AT152ED, Full Aperture, Outside, Montage.jpg

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#2 peleuba

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Posted 18 October 2020 - 02:03 PM

An astro buddy of mine Allen, along with his wife Cindy, took a day trip to my house to pick up his APM 152ED doublet he sent to me for testing a few months back.  He brought along his new Astro-Tech AT152EDT, F8 triplet for DPAC testing.

 

 

 

I like.   Just a hint of overcorrection in green and white, more so in blue, but I am visual so who cares!  The edge has an artifact that is probably not visible in single-pass normal usage.  Nothing like my APM152.  This is a much better scope then that.

 

I have always wondered about these...  I have, from time-to-time, thought about keeping one setup outside.

 

Thanks for posting.


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#3 Jeff B

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Posted 18 October 2020 - 02:05 PM

This is excellent spherical performance, with as expected, a little spherochromatism between the red and blue images, specifically, blue is a bit over-corrected while red is a bit under-corrected, with green being quite neutral.  There is a subtle center zone and just a tad of a very narrow turned edge (which might well be invisible visually).  I've a feeling that just a layer of felt lining, maybe 3mm thick  placed around the front of the objective would hide that edge completely, if you really think it should be masked out. 

 

However, to check out the edge, here are the same montages but at 5.5" aperture, as well as a null shot, also at 5.5" aperture (where you can see the subtle center zone)..  

Attached Thumbnails

  • AT152ED, Montage, 5.5 Aperture, Inside.jpg
  • AT152ED, Montage, 5.5 Aperture, Outside.jpg
  • AT152ED, White, 5.5 Aperture, Null.jpg

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#4 Jeff B

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Posted 18 October 2020 - 02:12 PM

This is really very good spherical performance.

 

With the ED element being similar to FPL-51, here are some color montage comparisons between the AT152 and my older TEC 160ED.

 

First, inside of focus.

 

Attached Thumbnails

  • AT152ED, Full Aperture, Inside, Montage.jpg
  • TEC 160ED, Inside, Montage.jpg

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#5 Jeff B

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Posted 18 October 2020 - 02:16 PM

Now the outside of focus comparison between the AT152EDT and TEC 160ED.  IMO, the AT152EDT is right up there with the TEC, and a real bargain.

 

Jeff

 

 

Attached Thumbnails

  • AT152ED, Full Aperture, Outside, Montage.jpg
  • TEC 160ED, Outside, Montage.jpg

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#6 Jeff B

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Posted 18 October 2020 - 02:20 PM

Just for fun, a null of the AT152EDT (at 5.5" aperture) and a null of the TEC 160ED, both in green of course.  The AT152EDT is quite smooth.

 

Jeff

Attached Thumbnails

  • AT152ED, Green, 5.5 Aperture, Null.jpg
  • 160ED Green Null Redo.jpg

Edited by Jeff B, 18 October 2020 - 02:21 PM.

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