Brushstrokes in HA after batch-processing

[ericm]

Hello,
I'm a totally newbie and just beginning to understand how to begin with processing. After a lot of trial and error I was able to shoot my first pictures with narrowband. Processing was the next step. I used batch processing and put all the files in the right place. After several minutes everything was processed en the masters photos visible. OIII en SII each 9 photos 300 seconds 139 gain ZWO 1600mm pro cool looking good for only 9 photos. But the HA master Astrodon 3nm 35 photos 300 seconds 139 gain is different, it looks like someone takes a fine brush and make brushstrokes from the righthand bottom corner to the lefthand top corner. The stars look sharp.  Has anyone an idea what I'm doing wrong.

Excuses for my English.
Thanks,
Eric

[mcgillca]

Dear Eric,

Hi - I have no idea what is wrong, but can offer you some thoughts on how to investigate further.

Start by examining your raw Ha files - do they show these features? If so, then look for something that has happened to your equipment - is there e.g. condensation on the filters (I know the Pro model is supposed to be immune from this, and indeed its much better, but I still have had the occasional problem)?

If not, try looking at the calibrated files - if so, then there is a problem with your master dark, bias or flat frames (most likely flats since the darks and master should be the same as your OIII image).

If the calibrated files are also OK, then it must be something odd in the integration step.

Good luck - its frustrating since otherwise the image does look good.

Colin

[pfile]

looks like residual hot pixels after calibration and undithered subs leading to 'walking noise'.

if your images really are undithered then you might try using CosmeticCorrection to clean up the hot pixels before registration and integration.

rob

[ericm]

Thanks for the replies. I think I found the problem. In batch processing I put all the files I have, also the dark flat frames. When I removed this dark flat frames the problem was over. But now is my question what's the use of shooting dark flat frames and how do I process them when it is not possible to put them in the same file as de normal flat frames?

[pfile]

the BPP script has to look at all the darks you've put in and try to make a decision about when to use which one. it's possible that based on the duration of the darks it just could not tell which belonged to which, and it applied the wrong darks to the lights.

the way BPP works is that it creates a fully calibrated master flat. so what you can do is load one dummy light, all your flats, and your dark flats and then run BPP. it should create a master flat. you can delete the calibrated light that it makes during this run.

then you load your lights, darks, bias and master flat into BPP and run again. BPP expects the master flat to be calibrated so it won't try to calibrate it again using your darks or biases. but it will create master bias/dark, and calibrate the lights with the resulting masters plus the master flat you loaded. there's a checkbox in the interface that says "use master flat" to let BPP know that you aren't loading any flat subs on purpose.

rob

[ericm]

Thanks for the reply. I will try that tomorrow and let you know the result.
Eric

[ericm]

I finally have a good result with this workflow in BPP. First I Put in the Bias frames, Dark Flat Frames in the dark section, Flat frames in the Flat section and the Light frames HA SII OII in the light frames section. "Optimize darks" unchecked. After that I run it all.

I reset the BPP and start again. Bias frames in Bias, dark frames in dark, master flat frames HA SII OII in flat and light frames HA SII OII in lights,"Optimize darks" unchecked and use master flat enabled. Run again.

The master lights were much better, no amp glow and less noise. For me these are the first light frames I have ever seen so its difficult to judge the quality.

But I think this is what you ment Rob. If it's not tell me please.

[pfile]

yes that is what i was describing, but in the first phase you don't need to load all your lights, just one of each filter. the goal is only to create the master flats and calibrating a bunch of lights during that pass is wasted work.

rob

[ericm]

I did that in the first place but Pixinsight refused that for some reason. Next time i will try that again, it's a time saver.

Thanks again for your help.
Eric

[pfile]

well it might be the case that you need 3 images of each filter because ImageIntegration requires a minumum of 3 images to run. so you might try either loading 3 images, or disabling the ImageIntegration portion of BPP by unticking "Apply" in the main interface.

rob