Imaging Changes

[DirtyRod]

Robin,

Has there been any changes to the way the focusing works? I’ve been running the same -90 to 100 range step 20 sequence for a while with both ZWO and Celestron Focusers and it has pretty much always looked the same while it creates the curve. The score increases initially then decreases down to BEST, increases, and then SC moves to best focus position.

Usually the max number of stars was at the BEST score but in my last few sessions, I’ve watched the number of stars increase and then decrease significantly at the BEST score. Last night, it counted up to 100+ stars and then dropped to 20-30 at best and then rose back to 100 before trailing off.

Another thing I noticed was that the subs right after a refocus scored lower in DSS. Last nights subs would be around 800 but would drop to about 600 after a refocus and would then start climbing back up. Generally they score the highest after a refocus or stay about the same if the temp has stabilized. This looks different with the new version.

I don’t know if it was just the targets in Cygnus that maybe have stars at different distances but I have seen references to making focusing adjustments to mimic Nina and wanted to ask.

[admin]

Hi,

no real recent changes, although it rather depends on how old the SharpCap version was that you upgraded from as to what has changed 'recently' from your point of view.

It sounds as though something is stopping the stars being detected correctly at best focus - the first thing that comes to mind is that perhaps the code that stops hot pixels being detected as stars could be doing this, particularly if you are using a large pixel camera which would mean that in-focus stars would be quite small in terms of pixels.

I would suggest getting to best focus and then tinkering with the star detection settings in the focus tool to see if any changes bring the star count back up to the level you would expect. Hopefully that will resolve the issue.

cheers,

Robin

[DirtyRod]

I will tinker and see what I get. The version I was using was 4.0.8XXX from maybe 2-3 months ago and the camera this week is an ASI533MC Pro so 3.76 isn’t particularly big. Haven’t intentionally made any changes I can remember so next time I will open that settings tab and see what testing I can do.

Thanks

[DirtyRod]

Did some tinkering and also upgraded to the latest version of SC today. Same behavior tonight - starts the sequence, star count drops from 70s to 8, counts back up to the 90s, drops to the 20s at peak, counts back up at end end and then settles on the 70s. DSS scoring dips right after focus and then improves.

Is there a specific SC setting I should be looking at?

This is a ZWO EAF behind a RedCat. Have not tried it with my Celestron gear.

[admin]

Hi,

the settings that will affect star detection most are

* exposure and gain in the camera controls
* Sensitivity, max brightness and noise reduction in the star detection settings

For star detection, I would suggest the following starting point

* Sensitivity, max brightness both at 90
* Suppress hot pixels on
* Use display stretch off
* Noise reduction 0.5

I think we may end up having to capture a few frames at different focus points so that I can investigate fully though.

cheers,

Robin

[DirtyRod]

Well I’ve spent a few sessions trying different settings, including the recommendations listed, as well as trying different gain and exposure settings it the results were the same. It shows the most stars about 30 steps before and after best focus. Last night, it dropped from mid 70s to mid 30s and then went back up after best focus. I did try turning off Use Display Stretch but that only resulted in 4-10 stars and it failed to find focus at all but I’ve never been able to get that to work since I started unless I do really long exposures. Right now I do 3 seconds at 300 gain.

Tonight I’m going to bring out my C8 with the Celestron motor and see how that works. For the last the last 6 months, it’s pretty much worked like the ZWO on my refractor so I will see if that behavior has changed. If it is doing the same, do you want me to capture some images at best focus and slightly before?

[admin]

Hi,

yes, please capture a few images showing the point where the most stars are detected and the point where the focus is really the best at least.

With those images I can hopefully start to work out what is going on.

thanks

Robin

[DirtyRod]

Sorry it's taken a while to get back but I have some test images. I have test files from when it's focused, 30 and 60 steps before focus, and 30/60 steps after focus. They are in TIFF that I cannot upload so do you want me to stretch and convert to JPG or something else?

[admin]

Hi,

best to look at the raw files, since that is what the focusing code will be doing. Could you share them using Google Drive/DropBox/OneDrive and then put the sharing link here on the forums?

cheers,

Robin

[DirtyRod]

Sorry for the delay. I after upgrading to the latest version the behavior seemed to stop so but it started again so here are the files.

I have six files uploaded; 2 where things are in focus and SC sees about 18 stars. Then moved the focuser in and out 30 and 60 steps and SC then sees 20 up to 40 stars. Again, not sure if this is actually a problem because DSS sees thousands of stars when I stack so I'm suspecting the only important number on that screen is the star value.

Here is the OneDrive link. Sometimes it does strange things so I also created a Google Drive link as well.
https://1drv.ms/u/s!AsF0dc6mRhwpgUEM-fH ... k?e=LUQfqq

This is a Google drive link. Company policy won't let me just open it up to anyone so when you click on the link it will allow you to request access and then I can give you rights to the drive.
https://drive.google.com/drive/folders/ ... sp=sharing

Let me know if you have any issues accessing.

Rod