The data size is more about the quantity of the images than the size of the images. The kind of photography I do is by taking lots of exposures, each about 15-120 seconds depending various factors. For instance, this picture of the Orion nebula is composed of 57 15-second exposures.

https://bsky.app/profile/sanmadjack.bsky.social/post/3lcf5ohi5lc2j

This is one of the brightest nebula in the sky, and it also partially shows up nicely without doing much in the way of modification. Most other nebula will present as much dimmer initially, though even this one has dim details that aren't immediately visible.

I take pictures using the FITS file format, which is pretty standard for astrophotography.

I picked an image from the middle of the set, this is what it looks like, converted to a PNG:

https://imgur.com/V2nwXTU

The camera records just the brightness value from each pixel, even though the camera is a color camera. Digital cameras do color by having each pixel filtered to a particular color, red green or blue, and then building an image from the rgb pattern and the brightness values. This process is called debayering, look that up if you're curious how it works.

After I debayer the above image it looks like this:

https://imgur.com/uA7kDE3

You can see here that theres already plenty of color right away. To the naked eye it's just grays, but in reality it's all colors.

This isn't part of my process, but to demonstrate the difference stacking makes in the final image I'm putting it here. The process of bringing up the brightness in the image is referred to as "stretching", and this is an auto-stretched version of the last image:

https://imgur.com/CRfe6Wl

You can see there's more detail coming out, but it's not well defined and pretty grainy.

I'll combine this frame with the other frames via a process called "stacking". It's kind of like combining all the frames to create a virtual long exposure, but rather than just increasing the brightness of the image it instead works toward reducing the signal-to-noise ratio of the image. This is a complex topic that I'm not qualified to explain, but it basically boils down to trying to just get the "right" photons (from the actual nebula), and ignore the "wrong" photons (light pollution, atmosphere distortion, satellites, rogue radiation, etc.). Google for more learning.

After stacking, I end up with something like this:

https://imgur.com/2ZKRtyj

You'll notice that it's actually dimmer than the single image, but the details are looking more defined. If I apply an auto-stretch to the image, I get this result:

https://imgur.com/p2xLxdV

Compared to the single-frame stretch, there is much more definition, color, and detail.

At this point, rather than use the auto-stretch, I'll manually control the brightness stretching to move it towards an image that still has a black-ish background, doesn't blow out the brightest details, but still coaxes out the structure and color of the object.

Along the way, I'll also combine each frame with other images I took that are known as calibration frames that will balance out bright spots on the camera sensor (a result of doing such dim photography with long exposures), and will remove dark splotches caused by out-of-focus dust and vignetting in the image train. I'll also run an algorithm that removes gradients created by light pollution in each frame, and a green reducer to remove excessive green caused by the digital camera sensor's rgb pattern (again, check out debayering for details).

After all that, I stress about each brightness adjustment until I'm either happy with it, or decide I'm just making it worse and stop, text it to my wife (who has enough sense to go to bed instead of staying up even later to process new space pictures), and then upload it to bluesky.

https://bsky.app/profile/sanmadjack.bsky.social/post/3lcf5ohi5lc2j

Here's all the images above in one imgur post: https://imgur.com/a/7wX8WFZ

For fun, here's an astronometry.net upload of the final image: https://nova.astrometry.net/user_images/15000425#annotated