Trying some new processing software

[Bobby1970]

I captured this image of the pac man nebula last year. I tried to process it using Startools which i have persevered with for several years despite not really achieving satisfactory results.

 

 

Recently i decided to try Affinity photo, and had a crack at re-processing this image using the original file which DSS spat out converted to TIFF.

Now, i realise its still not amazing, but i do feel its better than my effort with Startools. I need more star reduction really but havent figured out how to reduce any further than the live layer filter i used.

 

 

Hopefully with some better data using less  gain etc on my ZWO 178MC i should be able to achieve some better results.

 

 

[AstronomyUkraine]

47 minutes ago, Bobby1970 said:

Hopefully with some better data using less  gain etc on my ZWO 178MC i should be able to achieve some better results.

Have you tried Starnet to remove the stars, then reintroduce the stars after working on the nebula, without fear of causing damage to the stars?

[Bobby1970]

18 minutes ago, AstronomyUkraine said:

Have you tried Starnet to remove the stars, then reintroduce the stars after working on the nebula, without fear of causing damage to the stars?

I cannot, for the life of me get it to work. 

 

Extract the zip file to a directory, done

Drag the Tiff onto the executable starnet file. A window opens and lots of scrolling of words with something along the lines of "Adobe deflate, blah blah blah". No starless output file is created. 

 

Do I need an Intel CPU? I have AMD Ryzen. Wondered if that was an issue. 

 

 

[TerryMcK]

There are a few batch files in the directory where StarNet is installed. I have one called run_rgb_starnet.bat

this contains the following:

rgb_starnet++.exe bubblestars.tif bubblestarsnostars.tif 64
pause
 

Essentially if you have a tif file called bubbelstars.tif then put it into the same directory as StarNet, you double click on the batch file it will run and produce a file called bubblestarsnostars.tif in the Starnet directory without any stars.

 

The 64 in my example is the stride value and that can be changed from 16 to 128 in values of 16, 32, 64, 128. I believe you can input other values as well but 64 is a good place to start.

What you find is bigger stars leave artefacts behind and when you lower the stride number they are less noticeable. You do have to run it on 64bit versions of Windows though.

 

PixInsight now has it built in and it runs on many operating systems. It also creates star masks, which are essentially the original image with the starless image subtracted so not really masks in the strict sense, so you can add the stars back in after you have processed the nebula etc. I don't know of a way to produce the starmasks with the standalone version though as I use PixInsight.

 

You might be able to use Affinity Photo to subtract the starless image on a separate layer from the original image on the background layer to leave a star layer. I haven't tried it despite having AP and Photoshop. 

 

[TerryMcK]

Here's what I got when I ran it through PixInsights StarNet for you. Obviously you would extract the stars a lot earlier in the process and wouldn't get blue rings around them.

[Bobby1970]

So, i think i had the TIFF file in the wrong TIFF format, loaded into Gimp and saved as a non compressed TIF and Starnet worked.

 

Had a mess around in in Affinity and ended up with this:

 

 

I do think this is an improvement, but there are artifacts around the stars and i haven't figured out how to sort the really bright ones in the centre out yet :-(.

 

I do think it is progress of sorts though. lol

 

When is the optimal time to run the image through starnet? If done immediately after stacking it would surely miss a lot of stars??

 

 

[TerryMcK]

do it after stretching.

[Bobby1970]

13 hours ago, TerryMcK said:

do it after stretching.

So, when I initially stretch the image, i need to do so to a point where the stars are not bloated and overexposed, then remove them?

 

Is that essentially correct?

Edited March 13, 2021 by Bobby1970

[TerryMcK]

I would tend to stop short of even approaching overexposing anything. You can always bring up nebulosity with no stars which is preferable. In Photoshop or AP just bring the levels up in small increments or use curves to do the same. Once you have something near to looking ok, if you are using layers, merge the layers together or create a new layer with all the changes merged in. In Photoshop you select all layers then press ctrl, alt, shift and E all at the same time and it will do it for you. Then save the newly created layer into a 16bit TIFF and do the StarNet. 

 

In PixInsight there is a tool called Screen Transfer Function which essentially is an autostretcher so you can view the stretch prior to making it. You can play around with it until it looks ok and then do what is called a histogram transform which converts the picture from linear to non linear - or stretched. At that point there are other things to do but soon afterwards I do a StarNet to remove the stars.

[TerryMcK]

I've just tried ctrl-alt-shift-E in Affinity Photo and that key combination works in that too

[Bobby1970]

On 3/13/2021 at 10:47 AM, TerryMcK said:

I would tend to stop short of even approaching overexposing anything. You can always bring up nebulosity with no stars which is preferable. In Photoshop or AP just bring the levels up in small increments or use curves to do the same. Once you have something near to looking ok, if you are using layers, merge the layers together or create a new layer with all the changes merged in. In Photoshop you select all layers then press ctrl, alt, shift and E all at the same time and it will do it for you. Then save the newly created layer into a 16bit TIFF and do the StarNet. 

 

In PixInsight there is a tool called Screen Transfer Function which essentially is an autostretcher so you can view the stretch prior to making it. You can play around with it until it looks ok and then do what is called a histogram transform which converts the picture from linear to non linear - or stretched. At that point there are other things to do but soon afterwards I do a StarNet to remove the stars.

Been meaning to reply to this but it slipped my mind. 

 

I tried doing a small, very small stretch then removing the stars with Starnet. 

However, I still had lots of blue fringes and artifacts left behind. 

I think this must be because my original image is over exposed maybe? So no matter what I do, the stars are always going to be bloated and show the fringing and artifacts after running Starnet.