Unistellar eVscope 2 - First Experiences (After Repair - Part 1)

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On this and a further page, I describe my experiences with my electronic 4,5" Newton telescope Unistellar eVscope 2* after it had returned from repair. On this page, called "Part 1", I will only discuss the most obvious things that I noticed. On page "Part 2" I will present a number of "before/after" examples.
*) I ordered the eVscope 2 in October 2021; it arrived at the beginning of December, 2021; repaired by Unistellar; returned to be exchanged with a new one in March 2022 (the second one).

Note: See page Overview of the Unistellar Pages for just that!

Note: I did not prepare this page in order to critisize Unistellar (in the case of problems Unistellar and eVscope users have to cooperate closely!), but in order to help other eVscope users identify potential issues with their eVscopes.

Note: Since I was not satisfied with the results of my new eVscope 2, Unistellar offered to check and possibly repair my eVscope 2. So, I sent it to Unistellar on February 14, 2022 and received information on February 18 that my eVscope 2 had been repaired and will be returned to me. When asked, I was told that there was a problem with the primary mirror, which was slightly under tension and therefore produced blurry images. As proof of the repair, I received a photo of Alnilam. It looks much better than my similar photo of Alnitak (near the Flame Nebula), but at closer look still exhibits triangular stars).

Meanwhile, I was able to test my repaired eVscope 2 and report on my results on pages First Experiences (After Repair - Part 1) (this page) and First Experiences (After Repair - Part 2). According to this, the repair resulted in an improvement, but did not completely eliminate the mirror tension. Unistellar therefore offered me to return my eVscope 2 (end of March 2022) and exchange it for a new one. This arrived on April 8, 2022. So I close the pages for my first eVscope 2 sample!

So please note that my eVscope 2 photos on this page do not reflect the true performance of the eVscope 2!

Introduction

Photos: My eVscope 2 (December 3, 2021)

Since I was not satisfied with the results of my new eVscope 2, Unistellar offered to check and possibly repair my eVscope 2. So, I sent it to Unistellar on February 14, 2022 and received information on February 18 that my eVscope 2 had been repaired and will be returned to me. When asked, I was told that there was a problem with the primary mirror, which was slightly under tension and therefore produced blurry images. As proof of the repair, I received a photo of Alnilam, which looked much better than my similar photo of Alnitak (near the Flame Nebula NGC 2024) (for the phoos see further down).

In the meantime, I got my eVscope 2 back and was able on March 19 and 20, 2022 to take first test photos after the repair. On this page, I present the "basic" results of my testing of the eVscope 2 after the repair, particularly based on photos of Alnilam and Alnitak. More results are shown on page First Experiences (After Repair - Part 2).

Please note that my eVscope 2 photos on this page reflect a state "before and after a repair" and (hopefully) not the true performance of the eVscope 2!

Basic Test Results after the Repair

On Saturday and Sunday (March 19-20, 2022), I was finally able to perform some tests of my repaired eVscope 2. Basically, I took the photo of Alnilam that Unistellar had sent me as "proof" of the repair, investigated it more closely and also compared it to a photo of Alnilam that I took on March 20, 2022, both in sqaure and rectangular format. I soon realized that the seemingly perfect photo that Unistellar was not as perfect as I had initially assumed. This was supported by the two photos of Alnilam that I took myself. Particularly, on the rectangular version of the photo, I recognized triangular stars in the left third or quarter of the field of view. Tringular stars indicate tension on the mirror, which had, according to Unistellar, been removed. Actually, it had been removed to a certain degree, but not completely (see below for comparison photos).

At a closer inspection, particulary when making the image brighter, I found already that the Unistellar photo exhibits triangular stars - and this although the image has a square format and thus crops the left and right edges and also adds an overlay and a vignette which cover the stars in the periphery. All in all, this means to me that the Unistellar photo of Alnilam is not a valid test photo for checking the presence of mirror tension (that is, the presence of triangular stars). In addition, my square version of the photo of Alnilam shows more or less the same result as the one taken by Unistellar. And the rectangular version of the photo (which shows the field of view that is shown on the smartphone screen in the app, clearly exhibts triangular star shapes in the left and lower regions of the field of view.

Read also my comment that I sent to Unistellar:

When Unistellar sent a "proof" photo of Alnilam that was taken after the repair, I was enthusiastic and hoped that the problems with my eVscope 2 were gone. But now I have learned that already this same photo exhibits triangular stars and that the technical support did not thoroughly check the photo:

The photo was taken in quadratic format with an overlay. So an overlay was added as well as a vignette, covering the left and right parts of the photo that you see in the rectangular format (and on the smartphone screen as well) and also cropping the rectangular format that I usually use (and used the the original eVscope without problems).
The photo is unprocessed; if you make it brighter, the (already on this photo existing) triangular stars are easier to see! This is a simple technique that your technicians should have used.
Recently, I made this photo brighter, so that even on this "cropped" version (compared with the rectangular format), triangular stars can be recognized.

Photos after the Repair (by Unistellar and by Me)

In the following, I present some "proof photos" (reduced to 1280 x 960 pixels; PNG changed to JPG for space reasons) taken by Unistellar and by me after the repair:


Photo of Alnilam after repair (taken by Unistellar), unprocessed - I marked some triangular stars (some may be debatable...), Feb 17, 2022		Photo of Alnilam after repair (taken by Unistellar), processed = brightened up by me - I marked some triangular stars (some may be debatable...), Feb 17, 2022

Photo of Alnilam after repair (taken by me, square format with overlay), unprocessed - I marked some triangular stars, Mar 20, 2022

Photo of Alnilam after repair (taken by me, rectangular format), unprocessed - I marked some triangular stars, Mar 20, 2022		Photo of Alnilam after repair (taken by me, rectangular format), processed (made brighter) - I marked some triangular stars, Mar 20, 2022

So the first main result of my tests is that the triangular star shapes are still there - and in my opinion are unacceptable. I never had this phenomenon with my original eVscope!

Comparison Photos (before/after)

The next question was, whether the Unistellar repair did change matters, even though it was not completely successfully. To answer this question, I compared photos of Alnitak/Flame Nebula NGC 2024 that I took before and after the repair:


Photo of NGC 2024 and Alnitak, Feb 5, 2022, before repair, processed => compare the triangular stars with the photo right! The photo "after repair" looks much better, but still not OK... (original size)		Photo of NGC 2024 and Alnitak, Mar 20, 2022, after repair, processed => compare the triangular stars with the photo left! The photo "after repair" looks much better, but still not OK... (original size)

If you take a look at the images with 1280 pixels or in original size, the image taken after the repair looks clearly better than the image that was taken before the repair. Nevertheless, the image after the repair still exhibits triangular star shapes (which can be seen more easily, when the photo is brightened up; I therefore present processed versions).

Further Issues...

I had written Unistellar on the occasion of the repair that the focuser is difficult to move when turning to the right (approximately behind the focus point). This has not changed to this day, while the focuser worked smoothly on my original eVscope (which I have since sold). Somehow I have a feeling that this problem is related to the "mirror tension problem"....

Below I show the collimation pattern after the repair (Mar 20, 2022) , when moving the focus wheel to the left and right stops (to the right the resistance becomes higher from about the focus point). Interestingly, the collimation pattern becomes asymmtrical at the right stop (although the photos look well collimated):


Focus wheel moved to the left edge (anti-clockwise) - more or less symmetric pattern		Focus wheel moved to the right edge (clockwise) - asymmetric pattern

Focus wheel still at the right edge - asymmetric pattern		Focus wheel moved once more to the left edge (anti-clockwise) - more or less symmetric pattern

Focus wheel moved to the focus point using a Bahtinov mask

Summary

To make a long story short: The repair was only a partial success. I do not think that the current results are acceptable, since the left third (or quarter) of the photos still shows triangular stars (which as far as I learned, are the result of tensions in the primary mirror). When I compare photos that were taken before the repair and similar ones taken afterwards, the tension in the mirror has indeed been reduced, and the photos look better overall. But I do not think that triangular star shapes are acceptable for such a costly telescope.

All in all, I am rather disappointed, not only of the still existing issue and the lack of care by the Unistellar technicians, but also of the prospect of having to send my eVscope 2 to Unistellar for a second time. I am willing to do some adjustment work myself in order to avoid having to send the eVscope 2 to France for a second time. But I am not sure, whether I will indeed be able to remove the mirror tension and thus, the problem...

Note

>>I took more photos of other DSO (before and after the repair) and also enlarged screenshots that prove the existence of the triangular stars. I present them on page First Experiences (After Repair - Part 2).

Appendix: Letter to Unistellar about Basic Test Results (March 19 and 20, 2022) after the Repair

On March 21, 2022, I sent the following letter (as part of a support request) to Unistellar:

On Saturday and Sunday (March 19-20, 2022), I was finally able to perform some tests of my repaired eVscope 2. To make a long story short: The repair was only a partial success. I do not think that the current results are acceptable, since the left third of the photos still shows triangular stars (which as far as I learned, are the result of tensions in the main mirror). As far as I can see, when I compare photos that were taken before the repair and similar ones taken afterwards, the tension in the mirror has indeed been reduced, and the photos look overall better. But I do not think that triangular star shapes are acceptable for such a costly telescope.

In order to keep my report short, I report only on the basic findings. I will prepare two new Web pages, where I will present before/after examples and further examples that demonstrate the existence and amount of the triangular stars. I will send you the links as soon as the the pages are ready (which will take a couple of days...).

When you sent a "proof" photo of Alnilam that was taken after the repair, I was enthusiastic and hoped that the problems with my eVscope 2 were gone. But now I have learned that already this same photo exhibits triangular stars and that the technical support did not thoroughly check the photo:

The photo was taken in quadratic format with an ovelay. So an overlay was added as well as a vignette, covering the left and right parts of the photo that you see in the rectangular format (and on the smartphone screen as well) and also cropping the rectangular format that I usually use (and used the the original eVscope without problems).
The photo is unprocessed; if you make it brighter, the (already on this photo existing) triangular stars are easier to see! This is a simple technique that your technicians should have used.
Recently, I made this photo brighter, so that even on this "cropped" version (compared with the rectangular format), triangular stars can be recognized (see below).

On March 20, I took a new photo of Alnilam, and there you can easily see the triangular stars ion the left third of the image even if you do not brighten up the photo (I also brightened the rectangular version up for comparison).

>>I took many more photos of other DSO and also enlarged screenshots that prove the existence of the triangular stars. I present them on page First Experiences (After Repair - Part 2) (in preparation...).

All in all, I am rather disappointed, not only of the still existing issue and the lack of care by the technicians, but also of the prospect of sending my eVscope 2 to Unistellar for a second time. I am willing to do some adjustment work myself in order to avoid having to send the eVscope 2 to you for a second time. But I am not sure, whether I will be able to remove the mirror tension and thus, the problem...

By the way, I wrote you that the focuser gets hard to turn when turning it to the right end (about after the point of focus). This still has not changed, whereas focusing went smoothly on my original eVscope (which I sold last week -- the new owner will contact you...). I somehow have the feeling that this issue is connected to the "mirror tension issue"...

_________________________________________________________________________________

"Proof" Images (reduced to 1280 x 960 pixels; PNG changed to JPG for space reasons):

Unprocessed		Processed (Made Brighter)

Photo of Alnilam after repair (taken by Unistellar), unprocessed - I marked some triangular stars (some may be debatable...), Feb 17, 2022		Photo of Alnilam after repair (taken by Unistellar), processed = brightened up by me - I marked some triangular stars (some may be debatable...), Feb 17, 2022

Photo of Alnilam after repair (taken by me, square format with overlay), unprocessed - I marked some triangular stars, Mar 20, 2022

Photo of Alnilam after repair (taken by me, rectangular format), unprocessed - I marked some triangular stars, Mar 20, 2022		Photo of Alnilam after repair (taken by me, rectangular format), processed (made brighter) - I marked some triangular stars, Mar 20, 2022

For comparison purposes:

Before Repair		After Repair

Photo of NGC 2044 and Alnitak, Feb 5, 2022, before repair, processed => compare the triangular stars with the photo to the right! The photo "after repair" looks much better, but still not OK...		Photo of NGC 2044 and Alnitak, Mar 20, 2022, after repair, processed => compare the triangular stars with the photo to the left! The photo "after repair" looks much better, but still not OK...