153 replies to this topic

[AstroApe]

Glad you did. My AT102EDL was last seen somewhere in TX, and FedEx current has no ETA on the arrival. This way I get to enjoy it vicariously a little before it arrives.

 

I saw your thread on the AZ75. Unfortunately it looks like your username is a dead ringer since you're having to show a great deal of patience just getting your gear... Hopefully your scope will arrive in great shape. If it eases your mind any, Astronomics does a fantastic job packing equipment for shipment.

Edited by AstroApe, 27 June 2023 - 09:27 PM.

[rexowner]

...

But here's what it looks like
...

 

IMG_3204.jpeg

Great review.  Thanks!

 

It also has a very ergonomic handle on the other side.  As an AT102EDL owner, this is one of my favorite features.

[PatientObserver]

I saw your thread on the AZ75. Unfortunately it looks like your username is a dead ringer since you're having to show a great deal of patience just getting your gear... Hopefully your scope will arrive in great shape. If it eases your mind any, Astronomics does a fantastic job packing equipment for shipment.

I should not have to wait long. I just received an update from FedEx that the scope should arrive today. If it arrives as scheduled, that will be two scopes in two days.

[Scott in NC]

Great review.  Thanks!

 

It also has a very ergonomic handle on the other side.  As an AT102EDL owner, this is one of my favorite features.

That’s the handle that you’re looking at in the picture.  There’s a Vixen-style rail on the other side.

[Phillip Creed]

First of all, notice how the lines are pretty nice and straight, especially in red and green, and blue is not too far off either.  This indicates that the optics have very good spherical correction, with only a hint of over-correction in all three colors. Ideally you want to see green as the best corrected color spherically, which is the case here. To my eyes, red really looks just about as good as green here. Blue is typically the farthest off, even in a very well corrected lens.  In this case, blue is so good from the standpoint of spherical aberration, that even if green looked the way that blue did here, it would still be a very well corrected lens.

Next, look at the white light images.  You don't see a lot of false color here, which is what I'd expect for a doublet made from FCD100 and lanthanum, like this is.  I see only the faintest hint of purple in the intra-focal images, and the faintest hint of purple/green in the extra-focal images.  The "at focus" image looks very smooth.

Last of all, look at the edges of the bands.  You'll see some slight curvature here, most likely indicating a very slight turning down of the very edge.  I don't think this is a significant problem, and when it's this minimal it's often hard for me to say for sure whether this represents a true edge aberration or is merely a diffraction artifact not related to the optics at all.

So, the bottom line is that this is a very nice scope, and I have no doubt at all that it meets (and probably significantly exceeds) Astro-Tech's minimum Strehl guarantee of >= 0.95.  This would be a scope that I'd be very happy to own.  I have a Tak FS-102 that I've owned for many years and don't plan to ever sell.  It's given me amazing views of the sky, yet IMO it doesn't look quite as good as this Astro-Tech does on DPAC testing.

 

I told the scope's owner that he should consider this one to be a keeper.  It's amazing what nice optics one can buy with $999 nowadays!

I'd gladly use a scope like this for imaging.  I don't buy the, "you MUST have a triplet to image," adage when it comes to FCD100+Lanthanum doublets.

Clear Skies,
Phil

[Maciek_Cz]

Hi Scott,

Great job and very good results.
Let me present the results I got in the latest version of AOS. The telescope is top notch!
In the future, I have a request that you take one more picture. It's about the position of the Ronchi screen at focus.

Your at focus photo was taken about 0.5 millimeters inside of focus.

And this is very good, but a second photo taken on the opposite side, i.e. about 0.5 millimeters outside of focus, would be useful.

Take a look at the last picture I've posted below.

Thanks to such two photos, I will be able to better verify the selected parameters of the simulation.

 

Coming back to the results, the Strehl is large, there is also a small turned edge that is 5 percent of the radius of the lens.

I'd like to see a star test and if possible an interferometer certificate.

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Edited by Maciek_Cz, 28 June 2023 - 07:42 AM.

[Maciek_Cz]

Green

 

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[Maciek_Cz]

Blue

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[Maciek_Cz]

At focus - white

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[Bill Barlow]

Thanks for the test results on the AT 102 EDL.  I see in the Ronchi images you posted that there is a blurriness along the edges of each the lines and colors.  But in the images Maciek posted the left pictures show very sharp lines for each color.  Why is this?

 

Bill 

[Scott in NC]

Thanks for the test results on the AT 102 EDL.  I see in the Ronchi images you posted that there is a blurriness along the edges of each the lines and colors.  But in the images Maciek posted the left pictures show very sharp lines for each color.  Why is this?

 

Bill 

The images that I posted (the ones on the right on Maciek’s screenshots) are actual images taken with a camera looking through the Ronchi eyepiece.  The images on the left in Maciek’s screenshots are simulated (i.e., computer generated) Ronchigrams.  With his AOS program, one manually adjusts the simulated Ronchigrams until they match the actual Ronchigrams as closely as possible.

[Scott in NC]

Hi Scott,

Great job and very good results.
Let me present the results I got in the latest version of AOS. The telescope is top notch!
In the future, I have a request that you take one more picture. It's about the position of the Ronchi screen at focus.

Your at focus photo was taken about 0.5 millimeters inside of focus.

And this is very good, but a second photo taken on the opposite side, i.e. about 0.5 millimeters outside of focus, would be useful.

Take a look at the last picture I've posted below.

Thanks to such two photos, I will be able to better verify the selected parameters of the simulation.

 

Coming back to the results, the Strehl is large, there is also a small turned edge that is 5 percent of the radius of the lens.

I'd like to see a star test and if possible an interferometer certificate.

Thanks!  Next time I can certainly try to get a few more “at focus” images. I’ve found those to be quite difficult to photograph, but will keep trying. I didn’t have the opportunity to do a star test on this scope, but I can certainly try that in the future.  Regarding the interferometer certificate, the Astro-Tech EDL refractors aren’t sold with those.  I believe that the manufacturer provides one, but as a general rule Astronomics doesn’t typically release these, as they are supplied mainly for quality control so that Astronomics can ensure that the scopes meet their specifications.

[zakry3323]

I didn't know that Astrotech had a minimum .95 strehl guarantee. Very nice!

[Doug Culbertson]

I didn't know that Astrotech had a minimum .95 strehl guarantee. Very nice!

Only on the EDL series, to the best of my knowledge. 

[PatientObserver]

I didn't know that Astrotech had a minimum .95 strehl guarantee. Very nice!

They do for the EDL line of scopes; not the other lines to my knowledge.

[Maciek_Cz]

Only on the EDL series, to the best of my knowledge.

For what wavelength?

[Scott in NC]

For what wavelength?

We don’t know, although I believe that the similar line of scopes that KUO produces for TS Optics are tested in green.  So the inference is that the scopes that KUO produces for Astro-Tech are also tested in green, but I’ve never been able to find documentation of that.

[Cpk133]

For what wavelength?

As written, there’s a lot of wiggle room, could be infrared. I think I remember the regular 102ed with the fixed dewshield having a .92 minimum guarantee but again no wavelength was specified.  It might very well be in green, but they should specify to avoid being perceived like another company that has a history of obfuscation.

[peleuba]

For what wavelength?

 

I would bet my next paycheck that its Red...

 

A general rule of thumb is this:  If the wavelength is not mentioned, its usually red.  If its different then red, the interferograms will say so and list the wavelength. 

 

AT92's are red.

 

The rebrander/importer can specify which wavelength to test.   This may be why TS Optics are reportedly (I've no first hand knowledge of this) tested in green.   Either that, or TS Optics may have a local third party metrology () shop independently test the scope in green.   Germany, where TS Optics does business, seems to have several small companies willing to test optics via interferometers for these rebranders and importers.

Edited by peleuba, 29 June 2023 - 09:20 AM.

[Scott in NC]

I asked Michael Bieler about this a few months ago, and at that point he told me that he didn’t know and had never asked KUO.  That was right about the time that the infamous SVX180 was tested, and until then many of us (myself included) didn’t realize the importance of the tested wavelength.  I don’t know if anything has changed since then, but maybe he’ll see this and chime in.  I’m not going to bother him by asking again right now though.

[PhotogTom]

I asked Michael Bieler about this a few months ago, and at that point he told me that he didn’t know and had never asked KUO.  That was right about the time that the infamous SVX180 was tested, and until then many of us (myself included) didn’t realize the importance of the tested wavelength.  I don’t know if anything has changed since then, but maybe he’ll see this and chime in.  I’m not going to bother him by asking again right now though.

Judging from your test, it's pretty good across the visual spectrum, but Maciek's interpretation seems to favor red. Still, a pretty wide, flat curve ought to be apparent if plotted as a graph.

[bobhen]

I asked Michael Bieler about this a few months ago, and at that point he told me that he didn’t know and had never asked KUO.  That was right about the time that the infamous SVX180 was tested, and until then many of us (myself included) didn’t realize the importance of the tested wavelength.  I don’t know if anything has changed since then, but maybe he’ll see this and chime in.  I’m not going to bother him by asking again right now though.

When I purchased my 102 F7 EDL, I also asked Astronomics and was told that they did not know. And that was in the summer of 2022, long before the SV 180 test.

 

I would agree with pelueba that if I had to guess, they are probably nulled and tested in the red, as most likely all Chinese refractors are unless otherwise stated.

 

As pelueba says, if the test doesn't say, that can be an indication. Just like when a manufacture does not state a glass type, you can bet your bottom dollar that you are not getting Fluorite.

 

Bob

[Maciek_Cz]

Judging from your test, it's pretty good across the visual spectrum, but Maciek's interpretation seems to favor red. Still, a pretty wide, flat curve ought to be apparent if plotted as a graph.

Remember that AOS in the current version is based on an algorithm that checks how many of the rays hit the Airy disk. This is a very rough estimate of the Strehl coefficient value.

Edited by Maciek_Cz, 29 June 2023 - 12:38 PM.

[PhotogTom]

Remember that AOS in the current version is based on an algorithm that checks how many of the rays hit the Airy disk. This is a very rough estimate of the Strehl coefficient value.

Would it be fair to say that despite some lack of absolute precision, the relative performance from one color to the next can be assumed to be correct? That is, although all colors perform well, can we ascertain that red is the best performing of the 3 used?

 

Regardless, the results of this testing goes along with the very excellent views I get with my copy of the 102EDL.

[Maciek_Cz]

Would it be fair to say that despite some lack of absolute precision, the relative performance from one color to the next can be assumed to be correct? That is, although all colors perform well, can we ascertain that red is the best performing of the 3 used?

 

Regardless, the results of this testing goes along with the very excellent views I get with my copy of the 102EDL.

It is exactly as you wrote. The best correction is for red. Even at first glance, this can be seen from the shape of the ronchigram bands. Blue has the worst correction and green is in the middle. In the photo taken at focus you can't see any astigmatism or coma, so they are rather negligible. Therefore, it can be assumed that the estimate obtained in the AOS is close to reality. Scott took very good photos, which greatly facilitated the selection of parameters. It would be useful to have this one more photo to be sure (the one I wrote about earlier), but it is not necessary. With such clear ronchigrams, I got the job done very quickly.