Astrophotography

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Welcome to !astrophotography!

We are Lemmy's dedicated astrophotography community!

If you want to see or post pictures of space taken by amateurs using amateur level equipment, this is the place for you!

If you want to learn more about taking astro photos, check out our wiki or our discord!

Please read the rules before you post! It is your responsibility to be aware of current rules. Failure to be aware of current rules may result in your post being removed without warning at moderator discretion.

Rules

I | Real space images only.

Astrophotography refers to images of astronomical objects or phenomena exclusively.
~~Images that show objects or people below the Kármán Line (100km) will be removed.~~ We won't be enforcing this rule for now, but as the community grows eventually we will split and have a separate space for just landscape astro.
Images must be an accurate representation of a real astronomical object.
See this page for more details

II | Original and Amateur Content Only

Image posts can only be images that you have captured and processed yourself, or discussion about capturing and/or processing your own images.
Images acquired from public sources, professional observatories, or other professional services are not allowed.
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III | Post Types

Image posts are to link directly to the image, not to landing pages, personal galleries, blogs, or professional sites. Link to these in the comments. (AstroBin and Imgur, are allowed)
Questions are welcome here for the time being.
Links to blogs, articles or external websites should be interesting and promote discussion about amateur astrophotography.

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All image posts should just include include the name of the object being photographed. Extra info such as equipment, it being your first image, or other information should go in a comment along with your acquisition info. Please see this page for more details.

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V | Acquisition and Processing Information

All submitted images must include acquisition and processing details as a top-level comment. All posts without this information may be given a warning, and if not updated will be removed.
This includes the telescope, mount, camera, accessories, and any other pieces of equipment you used to capture the image.
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lefty7283@lemmy.world

Stuck pixels, only at high ISO? (youtu.be)

submitted 6 days ago by CameronDev@programming.dev to c/astrophotography@lemmy.world

6 comments fedilink hide all child comments

Hi All, I have a Sony A9, which I have been using for Aurora photography. The last time I went out, I shot at 6400iso, 2s exposures, and nearly all of the photos I got have a ton of "stuck" pixels. See the video, skip halfway in, and look at the rocks in the bottom right.

I have had a play with the the camera with the lens cap on, and at low isos, there are no stuck pixels, it's only once I go past 640 (the second iso range) that the issue appears. Has anyone seen this kind of thing before? Is it repairable? I'm guessing most of you shoot at iso100, but for aurora it was nice to get the shorter shutter speeds.

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[–] lefty7283@lemmy.world 3 points 6 days ago (1 children)

Hot pixels! Best way to deal with them is taking dark frames: a bunch of exposures with the exact same settings as your light/main frames, but with the lens cap on so it just captures the noise. Also important that your camera is roughly the same temperature as when you took the light frames, since this type of noise is very temperature dependent. Once you have your dark frames, you can stack them to make a master dark, and use this to subtract the hot pixels from your lights using a deep sky stacking program of your choice.

Side note: for most consumer cameras, using a higher ISO will actually lower noise, at the cost of dynamic range

[–] CameronDev@programming.dev 1 points 6 days ago (1 children)

It's a crazy amount of hot pixels though, doesn't seem normal? Pixel remapping doesn't get rid of them either.

[–] lefty7283@lemmy.world 3 points 6 days ago (1 children)

That seems like a fairly typical amount to me (certainly a lot less than my old canon 600d)

[–] CameronDev@programming.dev 2 points 6 days ago (1 children)

Okay, I'll take your word for it, but compared to my a5100 at the same settings, it's an insane amount.

I do have a dark frame from later that evening, so I guess I'll have to try the subtraction. Do you know of any software that can do the dark frame subtraction in batches? I have a few thousand shots I'd like to clean up :(

[–] lefty7283@lemmy.world 1 points 6 days ago (1 children)

Siril should be able to. I'll admit I've never used it myself (I use pixinsight for all my processing), but I know it's a fairly popular free processing option. Also you'll definitely want to try and take more dark frames than just one. Generally you'll stack the darks together, and then subtract that from your lights (this should remove most of the noise thats not the fixed hot pixels)

[–] CameronDev@programming.dev 2 points 6 days ago

For the future, I'll try the additional dark frames, but the hot pixels are so high SNR that hopefully 1 will do.

I didn't even know I was getting these hot pixels on the night, last time I went out I didn't have this issue at all, which is part of my concern, it's like my camera has gone from 0 obvious hot pixels to thousands overnight.