MartinFransson

Just received my Astrodon 3nm O3-filter (my wallet might never recover...) so I had to try it out. Weather not cooperating, though. Here is a quick widefield of IC1396 and friends. Only 18*5 minutes of O3 and 19*5 minutes of Ha. I had to stretch the O3 WAY harder than I wanted but the Ha swamped it otherwise. Still turned out pretty well I think. ZWO ASI1600MM-Cool + Canon EF 300/4L IS lens.

Thanks guys!

I finally finished my mosaic of NGC7000 + IC5067. This is a narrowband SHO-combination with the stars replaced with LRGB ones. A pain in the famous... to process! This was imaged with the ZWO ASI1600MM-Cool and my Sigma 500/4.5 EX DG lens. Total exposure is over 16 hours. So happy with this one! My new wallpaper and I´ll probably print it too ? Panel 1: Ha 24*5 min O3 26*5 min S2 21*5 min L 16*1 min, R 21*1 min, G 17*1 min, B 18*1 min Panel 2: Ha 32*5 min O3 28*5 min S2 34*5 min L 17*1 min, R 20*1 min, G 18*1 min, B 18*1 min

Looks great! I have problems with halos myself. Not in the Ha-data but in O3. Haven´t tried S2 yet.

Thanks for the advice! The "problem" is that the Astrodon is the one that works best The problem is worse with the ZWO filters. And it does not go away at f/2.8 or even f/4. Also, one of the corners indicate too close and the other too far away. Can´t be a distancing problem only. Anyway, I´ve been in contact with ZWO and my retailer and they will bring the camera in for sensor tilt adjustment. I´ll keep you posted on the results, however it will probably have to wait until September since astro darkness is away for the season when I get the camera back

No, there is no room. And if there is something wrong with the camera, I´d prefer to have it fixed instead of adding extra components. How does CCD Inspector work? I´m not familiar with that software.

I´m not sure what this cosign error is, but I´ve used the same telescope with other cameras (with larger sensors) without this problem. The problem stays the same (bottom left corner vs top right corner) when rotating the camera in the focuser.

Here are a few test shots: https://www.dropbox.com/sh/scdggkuzkz9lkfl/AAAb-XKj2w6D_pROG92anSvNa?dl=0 The single image is with the Samyang 135 mm lens, the ones in the folders are with my Skywatcher 150-PDS newtonian and Baader mkIII MPCC. In the "Refocused" folder I have two different focus settings, to try to make the bottom left and the top right corners good. Can´t get them both in proper focus at the same time. In the "Rotated" folder I have left the focus alone but rotated the camera in the focuser, to rule out that the effect is from focuser sag or similar. In all of my tests, it is always the bottom left versus the top right corner. Regardless of optics. Doesn´t that suggest problem being the sensor?

So, now I've done some more testing and the problem remains. Maybe not as pronounced, but still. I tested: - With and without filters. - Adjusting the tilt of the lens. - Using my Newtonian instead of a lens. - Rotating the camera in the focuser. None of the above helped. The problem is slightly less pronounced with the Newtonian but it's still there. Always in the same opposite corners even when rotating the camera 90 degrees in the focuser. So, should I send the camera back to check it for sensor tilt? I can post new images here for analysis in a while.

After taking everything apart I´m beginning to suspect you´re right! There seems to be room for some play between the lens and EOS adapter. I thought I had that eliminated by securing the lens with a scope ring. See attached photo. However, when tightening the screws on the scope ring, I´m able to "point" the lens to different directions and something has to flex to do that. I took everything apart, put the lens on the camera and placed it vertically with the camera down. That way there should be no flexing of the adapter. Then I gently tightened each of the screws until they barely touched the lens. Once they were all in contact I made a final tightening. Now I hope everything is without tilt. I also removed one of the filters to be able to do some tests without filter. The third test will be with the camera on my newtonian instead of with the lens. Now all I need is some clear skies to be able to test it all...

I might be a bit thick but if the results are better with the Astrodon than with the ZWO filter... then I should take away 1mm? Unfortunately that´s not possible... there is nothing to remove.

That´s it. And the lens of course. Samyang 135/2.0, Canon EF mount. The filters in the wheel are all ZWO filters except for the Astrodon 3nm (which works the best)

Yes, I have the one for use with a filter wheel and cameras with 6,5mm back focus (like the ASI1600). This is the one I have: https://astronomy-imaging-camera.com/products/accessories/eos-lens-adapter-efw-asi1600/ It´s not adjustable, is it?

The short one, specific for use with the filter wheel. No adjustment possible. Starting to suspect the sensor has a tilt...

I have a ZWO camera mount for the camera and a scope ring for the lens, so they should both be supported. You mean, removing and shooting without any filter at all? By the way, the lens is stopped down to f/4 but the problem is still there.

Thanks for the analysis! Two questions then, considering the problem is two fold: 1. Why would the distance be anything but spot on since I am using the recommended gear for this. The ZWO lens adapter is specifically adjusted to get the right distance. 2. What could cause the tilt? Sensor not mounted properly? Everything else is just put together and the lens itself has a flat plane.

I could add that the problem is somewhat reduced when using an Astrodon 3nm Ha instead of the original filters... Could it be that the sensor in the camera is not mounted completely flat? Is there any way to investigate that?

*New tests performed March 26, 2018. See post further down* I hope someone can help me. I have a new ZWO ASI 1600MM-Cool with an 8 pos. filter wheel and ZWO original filters. I use it with a Samyang 135/2.0 lens. My problem is that I can´t get an even focus plane even if I stop the lens down to f/4. If I get the stars pin sharp in the middle, I get odd stars in opposing cornes of the image. If I adjust it to be good in two corners + the middle, I get elongated (radially) stars in the other two corners. See attached image, autostretched in Pixinsight. What could be causing this? It shouldn´t be a spacing problem since I use the camera + filter wheel + ZWO EOS adapter for Canon EF-mount lenses. Added up, that should work. I have tested the lens itself using the Lonely Speck aberration test chart and it is pin sharp to the edges even at f/2 on a full frame camera. Any ideas? I´m pulling my hair here...

Thanks! I will go for the 31mm version.

I'm considering a package deal with filters included. There is about a 80 GBP price difference between 1.25" and 31 mm when buying all 7 filters (LRGB + narrowband). Not that much but I'm on a very tight budget.

No, 31 mm The 31 mm ones are unmounted, if that makes a difference. This is the info on their webpage: " LIMITING FOCAL RATIO Please note that the sensor diagonal size is very close to the internal clear aperture of a 1.25" filter, therefore with very fast telescopes or if you will use the camera with a fast photographic lens, telephoto lens etc. there might be vignetting. (lens with small f-ratio: photographers call it a fast lens because it takes less time to achieve the same brightness of the image) The limiting focal ratio with the ZWO manual filter wheel depends on the thickness of the filter glass and its clear aperture. The latter is usually 24 or 26mm for 1.25" filters. The cheaper ZWO LRGB filters that were developed for planetary imaging have 24mm clear aperture, but fortunately, the new LRGB filter that were developed for the ASI1600MM and ASI1600MM-COOLED cameras have 26mm clear aperture... Earlier calculations were approximate figures as those were based on assumptions rather that precise measurements as at that time we did not yet have the new filters and electronic filter wheels in stock. We have now took some measurements and recalculated the limiting f-ratio and to our surprise the results are much better, there will be much less vignetting... limiting focal ratio= (filter to sensor distance + thickness of filter) / (filter clear aperture - sensor diagonal size) Calculation for a 1.25" filter with 2mm glass (EFWMini or EFW 8*1.25"/31mm) (8.4mm + 6.5mm + 2mm + maybe 2mm more due to the cell) / (26mm - 21.9mm) = f/4.6 (f/4.85 with 3mm glass and f/5.1 with 4mm glass) good for a fast newtonian at f/5 or SCT at f/6.3 Calculation for a 31mm filter with 2mm glass (EFWMini or EFW 8*1.25"/31mm): (8.4mm + 6.5mm + 2mm) / (28mm - 21.9mm) = f/2.8 (f/2.94 with 3mm glass and f/3.1 with 4mm glass) this would be good for a fast Newtonian or APO at f/4 or even faster...or to be used with a telephoto lens at f/2.8 or slower "

I´ve decided to get a ZWO ASI 1600mm with a 8-slot filter wheel. There is a choice between 1.25" and 31 mm filters to be done. ZWO claim that the 1.25" filter are good for f/5 scopes and slower, whereas the 31 mm filter will work down to f/2.8. Since I will be imaging with both f/4 and possibly f/2.8 Canon lenses I guess I should get the 31 mm? What could be the effect of 1.25" and a fast lens? Vignetting?

Wow! How the heck did you get IC1805 that good without the stars over powering the image? I have tried with 600s exposures too but the stars are so many and bright! Sent from my phone using Tapatalk

A lot better! Wow, can't wait to get my 150PDS up and running. Sent from my phone using Tapatalk

Thanks for the processing tip!! Is J-P M:s tone mapping technique described in total somewhere? Would love to try it. Sent from my phone using Tapatalk