6 replies to this topic

[minhlead]

Now it seems I lost the ability to edit my previous post so I just go and create a new topic since I believe this deseves a new topic of it's own. Link to first part of the review https://www.cloudyni...eview-on-going/

So the Sun decided to come out after 2 straight months of cloudy sky. I take this chance to take the Acuter 40 to the test.

Transparency was bad with some high cloud (6/10). Seeing was relatively good.

The first peek through the EP and it was good. The image seems uniform without apparent sweet spot, the contrast was good with well defined surface details as well as prominence. I was pleased with the visual performance, the resolution is a bit low but that's to be expected. I noticed the image is noticably darker than my PST but the contrast and uniformity was better.

I decided to take an image and see if the camera and post process can bring out the uniformity that my Eyes couldn't pick up, I didn't use the flat intentionally, I want to test how uniform the scope was. I have always been very unlucky in the etalon lottery so finger crossed.

I pop the Touptek 678M on and the image fits nicely inside the sensor. A first look at the image and my heart immediately sank. There was some very apparent bright-dark patches that immediately noticable without any adjustment. Is it the etalon tuner? I tried to tune the etalon and immediately see the moving "sweet spot" going across the disk as the etalon tuner rotates. It seems the unlucky streak continues.

The most contrast came with this positioning. 

 

After recording about 4000 frames

After putting the image into the stacker and start processing with simple curve tool in IMPPG the non-uniformity is clear.

Point taken, the image was quite heavily contrasted but the sweet spot effect was very visible.

So I whip out my faux-flat technique and try to correct for the sweet spot using pixinsight and here's the result

Better? Maybe. Perfect? Far from it. Perhaps a proper flat at capturing would help? But still, aside from the unhomogenity in brightness, the FWHM widening/CWL shifting was also very apparent. I am afraid I have lost the ability to appreciate the uniformity/contrast of an etalon filter. Although this scope is not half-bad, it got decent contrast, way better than my PST. It still pales in uniformity/contrast in comparison with SHG images.

Just for reference purpose, here's single scan from an SHG 700 with a 100mm telescope (not fair, I know) taken 2 hours later.

 

Conclusion? It's a good scope visually but for imaging it's not winning any medal (at least mine won't). You might have better luck than I do. I was looking for a visual scope so I am happy.

Edited by minhlead, 20 March 2025 - 10:52 AM.

[astroflak88]

Have you tried using the Acuter for visual? Is it safe?

[spicerack0]

are the optics clean? the image should not be that blurry-   It appears there is something wrong with the scope-   My guess is it needs to be cleaned, or the objective lens is defective-

[minhlead]

Have you tried using the Acuter for visual? Is it safe?

I did. And have not go blind just yet.

 

are the optics clean? the image should not be that blurry-   It appears there is something wrong with the scope-   My guess is it needs to be cleaned, or the objective lens is defective-

The optics came out with oily smudge out of factory (see first post). But I cleaned every surface. I chalk up some of the halo to the thin high cloud. Will do more test.

[astroflak88]

I did. And have not go blind just yet.

You are brave.

[spicerack0]

try taking the blocking filter out, and image the moon with it-

 

If you cant get a clean perfectly tack sharp image of the moon-  there is possibly more oil in the system somewhere, perhaps on the mirror diagonal .   (or the objective is defective)

 

And yes you should be able to record the moon just fine through the etalon (cant do that with the blocking filter attached however)

Edited by spicerack0, 20 March 2025 - 07:32 PM.

[minhlead]

try taking the blocking filter out, and image the moon with it-

 

If you cant get a clean perfectly tack sharp image of the moon-  there is possibly more oil in the system somewhere, perhaps on the mirror diagonal .   (or the objective is defective)

 

And yes you should be able to record the moon just fine through the etalon (cant do that with the blocking filter attached however)

I think I'm quite well versed with optics cleaning by now and I can tell with 100% certainty that the optics are as clean as they can and the resolution is not improving. That's kinda to be expected though since it was the same kind of resolution that I get on my PST 40. A test today with better transparency still show the same sharpness. Images coming soon.