Questions

[ithurtssobadly]

Hello. I just started astrophotography like 1 year ago and I still can't figure out how to counter this (zoom sometimes reset for my camera)
I do smartphone astrophotography and i use Deepskycamera app to take pictures 
Everytime I observe, there's this black background around the circle fov which i really can't get rid of...
Example is the image attached below

This same black background ends up white after stacking all my light dark flat bias frames...
Is there any way i can get rid of it?

Thanks.

Lights_0005_20231031_232140198000000.dng

Edited November 16, 2023 by ithurtssobadly

[Cornelius Varley]

The black area around the central image is caused by the eyepiece.

Please upload a jpeg or PNG version of the image so that it can be viewed in the browser.

[Louis D]

If you are indeed performing afocal astrophotography and the black area outside the eyepiece's apparent field of view is bothering you, buy an eyepiece with an angular apparent field of view wider than the angular diagonal field of view of your camera.

[ithurtssobadly]

14 hours ago, Louis D said:

If you are indeed performing afocal astrophotography and the black area outside the eyepiece's apparent field of view is bothering you, buy an eyepiece with an angular apparent field of view wider than the angular diagonal field of view of your camera.

My phone camera is around 120 degree fov maybe.. (using samsung s23 ultra) I can't find anything higher than that

Also is there a way to fix this color noise in my image?

Edited November 17, 2023 by ithurtssobadly
my fov might be wrong

[ithurtssobadly]

13 hours ago, Cornelius Varley said:

The black area around the central image is caused by the eyepiece.

Please upload a jpeg or PNG version of the image so that it can be viewed in the browser.

Ok, here

[Louis D]

Don't use an ultrawide angle camera lens with an eyepiece during afocal projection photography.  As you've discovered, it results in a massive mismatch in fields of view if you do.

Try using the wide angle and then the telephoto cameras to see if you get a better field of view match.  For night photography, you'll definitely want to do pixel binning with those high resolution imagers behind those camera lenses.

You could try taking ultrawide angle images of the night sky using that ultrawide camera.  Just mount the camera to a tripod and take some images of different exposure lengths to see what you get.

[ithurtssobadly]

1 hour ago, Louis D said:

Don't use an ultrawide angle camera lens with an eyepiece during afocal projection photography.  As you've discovered, it results in a massive mismatch in fields of view if you do.

Try using the wide angle and then the telephoto cameras to see if you get a better field of view match.  For night photography, you'll definitely want to do pixel binning with those high resolution imagers behind those camera lenses.

You could try taking ultrawide angle images of the night sky using that ultrawide camera.  Just mount the camera to a tripod and take some images of different exposure lengths to see what you get.

I see. Will try!

[ithurtssobadly]

23 hours ago, Louis D said:

Don't use an ultrawide angle camera lens with an eyepiece during afocal projection photography.  As you've discovered, it results in a massive mismatch in fields of view if you do.

Try using the wide angle and then the telephoto cameras to see if you get a better field of view match.  For night photography, you'll definitely want to do pixel binning with those high resolution imagers behind those camera lenses.

You could try taking ultrawide angle images of the night sky using that ultrawide camera.  Just mount the camera to a tripod and take some images of different exposure lengths to see what you get.

but how do i do pixel binning

[Louis D]

I was reading up on your phone's cameras, and near as I can tell, simply choose lower resolutions.  It will result in lower resolution images, but, for instance, 2x2 binning at 1/2 the linear resolution (1/4 total pixels) results in 4x as much light gathered per pixel.  Give it a try at various resolution levels to see which produces the best compromise between resolution and image brightness.  Lower resolution results in a shorter exposure time to get to the same image brightness (density) as at higher resolution.  If your mount doesn't track, keeping exposures shorter will reduce image blurring as the Earth rotates under the sky.

[ithurtssobadly]

1 hour ago, Louis D said:

I was reading up on your phone's cameras, and near as I can tell, simply choose lower resolutions.  It will result in lower resolution images, but, for instance, 2x2 binning at 1/2 the linear resolution (1/4 total pixels) results in 4x as much light gathered per pixel.  Give it a try at various resolution levels to see which produces the best compromise between resolution and image brightness.  Lower resolution results in a shorter exposure time to get to the same image brightness (density) as at higher resolution.  If your mount doesn't track, keeping exposures shorter will reduce image blurring as the Earth rotates under the sky.

and should i also use an uhc filter which (possibly) can reduce light pollution?

[Louis D]

The UHC filter would probably help to reduce skyglow so you would get better contrast of nebula against the background skyglow.  For star fields or open clusters, you probably want to avoid using a UHC filter because it throws off the star colors and would probably cause star bloat.  You can always increase contrast on star fields in post processing by adjusting levels/curves.

Edited November 19, 2023 by Louis D