A7R5: 15 mp vs 61 mp for star tracker astro shots?

[rcreamer]

I was wondering, does anyone knows if the 4x additional memory/processing burden for 61 mp vs 15 mp for high-iso star tracker tracked images is worth it? [A7R5]

Especially since:

• The 15 mp doesn't need Bayer interpolation vs the 61 mp which does

• The inherently lower pixel data value accuracy for low-brightness high-iso images

• The cumulative minor sub-pixel alignment (registration) errors when stacking dozens of noisy images with lens abberations, imperfect polar alignment, etc

• The additional SDXC card, hard drive, memory footprint + the additional CPU burden through all the post processing steps

I'm just getting started with a Star Adventurer GTi and knowing that 15 mp data is essentially as good as 61 mp data would greatly reduce the memory and processing time.

Thanks in advance.

PS: I'm new here so any suggestions on how to improve this posting such as Tags are welcome.

 

[rcreamer]

Update:

About 10 minutes ago I entered a tweaked version of my original post/question below into [Perplexity] [dot] [ai].

Its answer is: go with 15 mp for astro.

I decided not to withdraw my question/post here because it may very well be of interest to other astrophotographers here. Also, I'd enjoy any discussion of this topic here

I recommend pasting the below into Perplexity as I certainly learned a thing or two

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Question text entered into Perplexity:

I was wondering, is the 4x additional memory/processing burden for 61 mp vs 15 mp for high-iso star tracker tracked images is worth it? [A7R5]

Note: this question is not about capturing 61 mp and then downsizing that to 15 mp. It is about capturing 15 mp images natively in-camera using the Sony a7r5's 15 mp lossless compression raw capture mode.

Especially since:

• The 15 mp doesn't need Bayer interpolation vs the 61 mp which does

• The inherently lower pixel data value accuracy for low-brightness high-iso images

• The cumulative minor sub-pixel alignment (registration) errors when stacking dozens of noisy images with lens abberations, imperfect polar alignment, etc

• The additional SDXC card, hard drive, memory footprint + the additional CPU burden through all the post processing steps

I'm just getting started with a Star Adventurer GTi and knowing that 15 mp data is essentially as good as 61 mp data would greatly reduce the memory and processing time.

 

[jacobomerced]

I must admint, i dont know anything about astrophotography.

 

[rcreamer]

In a nutshell, astrophotography is difficult because:

• Stars are very dim.
• Digital sensors' pixel values are very inaccurate for dim pixel values --> noisy images. Plus, high ISO adds more noise.
• It is impractical to "expose to the right" to fix the noise.
• So astrophotographers take many shots and average the pixel values (stack) to reduce the noise.
• Stars make star trails because of the Earth's rotation.
• Telescopes and star trackers can rotate at one revolution per day to counteract the apparent star motion. This enables the capture of many longer-exposure (say 2 minutes) images to stack but you have to aim the mount's polar axis at the north celestial pole very accurately.