Struggling with APP + GIMP

[vlaiv]

2 minutes ago, Anthonyexmouth said:

As a flat field generator is out of the question at the moment, motorised focuser is next on the shopping list. Would a flat field app on my tablet be a better way to take uniform flats? am i right in thinking i can lower the light to take slightly longer flats and then take the flat darks right after with the same settings?

what would be a good number of frames to take?

I have not worked with tablet/laptop screen so I can't comment on that. I think some people are using it successfully.

You can keep short exposure times you have now. I have rather strong flat box and my flat exposures are also very short - just a few ms. I only once had a problem with flats and that was because of faulty power supply connector on my flat panel. Flat panel was flickering rapidly, probably due to sparking on less than perfect power connection, but it was not something that you could see with naked eye - light appeared uniform. Frequency of flickering was probably way too high for eye to see, but at such short exposure it was noticeable as banding in flats. Once I figured it out, it was easy fix with a bit of soldering.

Best way to go about flats in your case is to set flat exposure manually (don't leave it on auto or whatever) so that all three histogram peaks get on right part of histogram if possible, just avoid clipping bright areas. Take as many flats as you can and then leave all settings as they are and do another run but with scope cover on. Simple as that. I advocate large number of all calibration subs - I tend to use 256 of each (have this thing about binary numbers - and that is 2^8 ).

If you dither your subs, then you can use less calibration subs, you are already using pretty decent number - 50 of each.

Btw, I'm just about to stack your subs using ImageJ to see what sort of result I will get in that workflow. Will post results.

[vlaiv]

@Anthonyexmouth

No wonder you have trouble stacking and processing your image. Data is rather poor. A lot of subs is just high altitude clouds and LP reflection of them.

Here is a little gif that I made - it's red channel binned to small size and linearly stretched to show frame to frame difference. Some of the frames contain nothing more than LP glow and only brightest stars.

Stacking such data will produce poor results - both in terms of SNR and with significant strange gradients.

I will try to get the best out of this data using my own "sophisticated" algorithm designed to handle such cases where there is significant SNR difference between subs, but I don't expect much from this data. I will need to remove at least couple of frames that are very poor.

[Anthonyexmouth]

58 minutes ago, vlaiv said:

@Anthonyexmouth

No wonder you have trouble stacking and processing your image. Data is rather poor. A lot of subs is just high altitude clouds and LP reflection of them.

Here is a little gif that I made - it's red channel binned to small size and linearly stretched to show frame to frame difference. Some of the frames contain nothing more than LP glow and only brightest stars.

Stacking such data will produce poor results - both in terms of SNR and with significant strange gradients.

I will try to get the best out of this data using my own "sophisticated" algorithm designed to handle such cases where there is significant SNR difference between subs, but I don't expect much from this data. I will need to remove at least couple of frames that are very poor.

I thought i checked them. This is why i miss pixinsight, the blink module makes weeding out bad frames. 

[Guest]

You have very nice Data, with APP I was able to get this..

Cheers

 

Martin

[vlaiv]

Well, my best effort in handling this data (for now red channel only) involves binning x2 in software to increase SNR - then we get good outline of nebulosity:

My "sophisticated" stacking algorithm does not yet support sigma clip - so some satellite trails are visible. Final image will be quite small in size - this is due to fact that I debayer by splitting channels rather than interpolating, and then after I did bin x2 which brings image size down x4 compared to original sub size - above screen shot is 1:1 (or 100% zoom).

Will try processing other channels as well and combining data to get resulting color image ...

[vlaiv]

This one was not easy at all

After all of my trickery, this is what I was able to get out of that data:

I think I rejected something like total of 8 frames, and another 4 green fields - they simply refused to be registered with ImageJ registration plugin so had to be removed.

[wornish]

After learning how to handle OSC camera data!  ( must pay more attention)  I downloaded the OP raw files.

 

Here is my go using APP followed by a bit of PS.

 

 

 

I then thought I would try the new Starnet software to remove all the stars then add the larger ones back.

Its very interesting to see how much of the nebula info is captured in the background.

 

 

 

 

Edited August 7, 2019 by wornish

[vlaiv]

2 minutes ago, wornish said:

I then thought I would try the new Starnet software to remove all the stars then add them back.

Its very interesting to see how much of the nebula info is captured in the background.

That is excellent idea, must try it on my version!

[vlaiv]

Result is rather interesting ...