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Comment by bhouston | Hacker News Reader

417 megapixels image is really nice but it also something people on earth can at least approach. I did a 28 megapixel Andromeda galaxy shot myself without even resorting to mosaics:

https://www.astrobin.com/hqrhe0/

With a few changes I could have easily got somewhere around 100 megapixels if I did a 2x2 mosaic without my reducer on the scope.

There are better cameras and scopes (planewave scopes for example) that getting to 400 megapixel is totally achievable for a high end mature astrophotographer.

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Astronomical seeing severely limits the efficacy of even multi-million dollar telescopes. The size of the pixels in this image is ~0.2 arcseconds, which is far below typical seeing limits even in excellent conditions.

Excellent seeing on earth is typically 0.4 arcseconds, so close. https://en.wikipedia.org/wiki/Astronomical_seeing

My setup gives me around 1.92 arc seconds for a point diameter.

And you can do tricks such as lucky imaging or active optics (depending on your budget) to further improve the resulting resolution. Lucky imaging is tricky on something as dim as Andromeda, but has been shown to be just about possible.

I haven't seen lucky imaging used on dim objects by anyone I know. I personally do not have a large enough aperture to collect enough light for that. But I've used it on bright planets before via AutoStakkert[1]: https://www.astrobin.com/full/06dzki/0/

[1] https://www.autostakkert.com

Lucky imaging was always a tool for use on planets and the moon. Anything bright.

It's hard to do dim objects because there's less for the software to inspect in each frame to determine the luckiness and distortion, but you can maybe use fortuitous bright stars in the frame to index off. You also need to collect a huge number of images to get any sort of signal to noise ratio. This video is an example of the technique actually used on a dim object, though the results were fairly modest because of murky British skies.

https://www.youtube.com/watch?v=5s9xbZ5G-wk

That 'excellent seeing' is for sites that are chosen for telescopes. Typical seeing from sea level is much worse:

- https://www.ing.iac.es/astronomy/development/hap/dimm.html

- https://www.researchgate.net/figure/Fig-C1-Seeing-distributi...

- https://www.mdpi.com/2072-4292/15/9/2225

Around 1-2 arcseconds is 'good' seeing in your backyard. There is a good reason for telescopes to be on some of the tallest mountains on Earth.

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