Need lot of help for image processing

[Kudogoku]

Hello everyone.

I need lots of help for the image processing technique as I'm new to astrophotography and image processing.
I never use Photoshop and other applications for image processing before (Only some easy image editing like contrast and maybe some drawing) and when I look up about post-processing after stacking the photos I'm very confused... 
I know that my exposure time is not very long because I only have 20 best images for stacking out of 40...but is it because of the lacking of exposure time that the details is not showing or I didn't get the stretching process right. 
I have attached link of my post-stacking/editing image in this post.
https://ibb.co/Js462YZ
Also, It seems there is a circle of noise at the center after stacking. I mean like all of the image I stacked.
Is it because of my lens and my camera? or it's normal?

Ps. Photo taken by SonyA6500 in the light polluted area (From the balcony of my room)

 

Thank you and best regards

[david_taurus83]

Hi. It might help if you can tell us more about what gear you've used to capture, exposure times, ISO etc

[wimvb]

It seems to me that you didn't use calibration frames. So called flat frames will remove the vignetting (bright circle) on your image.

There is a lot to learn in astrophotography, and this is the best place to start:

https://www.firstlightoptics.com/books/making-every-photon-count-steve-richards.html

Edited May 13, 2019 by wimvb

[Kudogoku]

Just now, wimvb said:

It seems to me that you didn't use calibration frames. Do called flat frames will remove the vignetting (bright circle) on your image.

There is a lot to learn in astrophotography, and this is the best place to start:

https://www.firstlightoptics.com/books/making-every-photon-count-steve-richards.html

Hi! wimvb.

Indeed I didn't use in this picture but even after I used there is some vignetting...I'm not sure why...
So now I cropped the picture but I would love to know why it still there and how to get rid of it completely.
Thank you for the recommended book as well, I will look into it.
 

19 minutes ago, david_taurus83 said:

Hi. It might help if you can tell us more about what gear you've used to capture, exposure times, ISO etc

Hi! david_taurus83.

Sorry for the lack of information.
My camera is Sony A6500 with lens SEL18135
Exposure time for this set is 8secs (Highest I can get without star trailing) with ISO800 f/5.6

 

I did stacked the pictures again with dark frames and flat frames and try to use Photoshop again.
This is the best I can get...
Can it be better than this? How can I get rid of the noise?

 

Thank you and best regards

[wimvb]

I assume that your camera image files are raw format and not jpeg.

Further, to reduce noise, stack ALL your subs, except those that have very obvious faults (cloud cover, huge airplane trails).

The flat frames themselves need also be calibrated, but deep sky stacker and other stacking programs, take care of this.

In post processing, don't stretch too much, and keep your black point such that no pixels are clipped. At the very end of the process, you darken the sky a little more with curves, or bring in the black point slightly.

[Kudogoku]

2 hours ago, wimvb said:

I assume that your camera image files are raw format and not jpeg.

Further, to reduce noise, stack ALL your subs, except those that have very obvious faults (cloud cover, huge airplane trails).

The flat frames themselves need also be calibrated, but deep sky stacker and other stacking programs, take care of this.

In post processing, don't stretch too much, and keep your black point such that no pixels are clipped. At the very end of the process, you darken the sky a little more with curves, or bring in the black point slightly.

Thank you for your tips wimvb.

I will try editing again. By the way, could you please explain how to keep the black point. I'm not yet very understand about it.
It seems that if I try to keep the background all black, the detail doesn't come out...
I mean after I stacked my pictures in DSS, the outcome picture came out super dark without any details. Is this because my exposure is not long enough?

[wimvb]

The image, straight from DSS, should be dark with only the brightest stars showing. Stretching will reveal the nebula/galaxy. If you post the autosave.tif file here, I can have a look at it.

As for the blackpoint, just make sure that the histogram does not cling to the left edge, but is just but well separated from it.

[Kudogoku]

Autosave002.tifAutosave001.tif

1 hour ago, wimvb said:

The image, straight from DSS, should be dark with only the brightest stars showing. Stretching will reveal the nebula/galaxy. If you post the autosave.tif file here, I can have a look at it.

As for the blackpoint, just make sure that the histogram does not cling to the left edge, but is just but well separated from it.

Thank you so much wimvb. I will tried modified the picture again and I also tried to attached the tiff file in here but it kept failing after the bar is full...
I will try to take the photo again some other time and tried to upload the tiff file as well.

Edited May 13, 2019 by Kudogoku
Picture Upload fail

[Kudogoku]

It seems I can't attach files in here. It kept failed when the upload bar is finished, the pop up window said nothing just -200.
PNG type is fine though. Maybe the tif file is too big (like 187MB)

I have try editing like wimvb suggested, not making the histogram clinging to the left edge and this is what I got, not sure if it a bit yellow because of the milky way or I didn't do it right.

And another picture is from the old picture I take it aimlessly a while ago. After stacked and try to editing it I found that there is a ring at the center of the picture. Is that a fault with my lens? 

Oh and another question, some of my stacked picture came out very light (almost white but I can see the brightest star and some are very yellowish) instead of black like you said but I not sure why. Is that because of the white balance or something else? or do I need to fix something in DSS before stacking?
 

Thank you and best regards

[wimvb]

3 hours ago, Kudogoku said:

It seems I can't attach files in here. It kept failed when the upload bar is finished, the pop up window said nothing just -200.
PNG type is fine though. Maybe the tif file is too big (like 187MB)

If you have dropbox, you can share it that way.

Depending on what sky conditions you have (light pollution, full moon, or dark desert sky), your stacked images will be lighter or very dark. With a full moon, expect thebackground to be blue. With light pollution, red and brown/orange will dominate.

If you stack in dss, don't apply any stretching to the image before you save it. Keep the image "linear", and do the stretching in your image processing software (ps, gimp, etc)

[Kudogoku]

12 hours ago, wimvb said:

If you have dropbox, you can share it that way.

Depending on what sky conditions you have (light pollution, full moon, or dark desert sky), your stacked images will be lighter or very dark. With a full moon, expect thebackground to be blue. With light pollution, red and brown/orange will dominate.

If you stack in dss, don't apply any stretching to the image before you save it. Keep the image "linear", and do the stretching in your image processing software (ps, gimp, etc)

 

Thank you wimvb, I will try to upload them via dropbox tonight. 

In the case of light pollution (my picture after stacking is very yellowish). How can I extract the yellow part out? 

 

Thank you and best regards 

[Kudogoku]

I'm back! Finally able to upload one file to dropbox.
Here is the link
https://www.dropbox.com/s/fa2xrnppm8bnsxp/Autosave002.zip?dl=0

Here is another one
https://www.dropbox.com/s/eef1pj2k3hwhl0t/Autosave.tif?dl=0

 

If anyone want to try bring some details out of these tif I would be glad to see them.

Edited May 15, 2019 by Kudogoku
Adding link

[wimvb]

I had a look at your image. I think that the exposure time was too short to show anything. If you can't increase the exposure time you need to:

• increase the ISO number
• take a lot more exposures (hundreds rather than tens)

To get rid of the vignetting that your image suffers from, you need to take flats. This will improve your images. Use a flat screen, with even illumination. Take up to 100 exposures at a setting that put the histogram in the middle. Also take bias frames (at least 100). Use these together in your stacking software.

If you have the funds, invest in a tracking mount (german equatorial mount), or a smaller tracking mount, such as a Skywatcher Star Adventurer. This will allow you to take longer exposures. To handle the light pollution, you need a light pollution filter, such as an IDAS filter. You also need to take a lot of exposures to bring the noise down.

Hope this helps

[Kudogoku]

4 hours ago, wimvb said:

I had a look at your image. I think that the exposure time was too short to show anything. If you can't increase the exposure time you need to:

• increase the ISO number
• take a lot more exposures (hundreds rather than tens)

To get rid of the vignetting that your image suffers from, you need to take flats. This will improve your images. Use a flat screen, with even illumination. Take up to 100 exposures at a setting that put the histogram in the middle. Also take bias frames (at least 100). Use these together in your stacking software.

If you have the funds, invest in a tracking mount (german equatorial mount), or a smaller tracking mount, such as a Skywatcher Star Adventurer. This will allow you to take longer exposures. To handle the light pollution, you need a light pollution filter, such as an IDAS filter. You also need to take a lot of exposures to bring the noise down.

Hope this helps

I see, so the exposure time is too short that's why.

Could you please tell me what is the minimum exposure time? Or it's depend on sky and location condition? 

Tonight I will try again as the forecast said the weather is good today but no excellent like last time. 

For the mount, I did have Vixen polarie, is it alright? but I still try to figure out how to polar alignment and do other set up because it's not tracking correctly (star still trailing). I did try to follow the tutorial on the internet but it's not working. Do you have any suggestion for this matter? (I'm in southern hemisphere though with the clear view of SE and S view (the balcony of my apartment) 

By the way, with longer exposure times and higher ISO, my raw images will be very bright right? 

I will also try to prepare flat and bias frames as you suggested as well. 

Thank you so much wimvb. 

Best regards 

[wimvb]

4 hours ago, Kudogoku said:

Could you please tell me what is the minimum exposure time? Or it's depend on sky and location condition? 

The longer the time, the better. But you do need some sort of light pollution filter. If the histogram on your camera screen is close to 50%, you are close to over exposing. That's where a lp filter can help.

I'm not familiar with the Vixen Polarie. You can ask about it here on the forum, as well as how to polar align in the southern hemisphere.

Good luck

[ollypenrice]

On the processing side you could try Steve Richards' other book: https://www.firstlightoptics.com/books/dark-art-or-magic-bullet-steve-richards.html

It's very well thought-out and is mostly Photoshop-based.

Olly

[happy-kat]

When imaging using a static mount or light weight tracking mount this book might provide information for your imaging. Though it might be northern hemisphere bias. Astrophotography on the go.

Link here

The other books mentioned are very good to though taking shipping into account might change things. 

Edited May 17, 2019 by happy-kat