Last night, I managed to take my first successful picture of a nebula--the Orion Nebula (see picture below). I'm incredibly ecstatic, as before I had been limited to taking images of the moon.

enter image description here

I used a 25 mm eyepiece with my AWB 130 Newtonian telescope (650mm focal length and a 130mm aperture). I mounted my Samsung Galaxy S10 to my telescope and took pictures using pro mode. Unfortunately, I only discovered the picture above in my gallery after I had wrapped up with my stargazing; I can't remember whether I took the picture with my phone's basic camera app or one of the two photography apps I downloaded off of Google Play last night in order to photograph the Orion Nebula.

I fiddled with the various settings on my camera app and the two other apps, DeepSkyCamera and ProCam X, for some time before I (unbeknownst to myself) miraculously took the image posted above. I had no knowledge whatsoever how any of the settings (ISO, shutter speed, white balance, AF) would change the picture, so it is indeed a miracle that I even managed to get the shape, much less the hues of the nebula.

Today, after reading various articles, I now understand what most of these settings mean. ISO makes images brighter but at the expense of more noise. The articles I read usually suggested 800 or 1600 for astrophotography. Generally, articles suggesting higher ISO settings assumed that I would be stacking my images, which I'm not sure I can do. In regards to aperture, Lower f-stop numbers allow for a larger aperture, which means that more light enters the aperture and I can use a lower ISO to reduce noise. White balance changes the tone of the image.
I also read about the shutter speed and the 500 rule--shutter speed=500/(Crop Factor)(Focal Length)--but I'm not sure if the Focal Length is just the eyepiece's focal length or the camera's and the eyepiece's focal length combined. If the latter is the case, would I have to find my Galaxy S10's focal length? Would the 500 rule apply?
What ISO setting, shutter speed, and focus setting would you recommend?

  • $\begingroup$ It looks like you're on the right track! Here's an improved "500 rule" calculator: scantips.com/lights/stars.html . For stacking try DeepSkyStacker: deepskystacker.free.fr . And this website has lots of tips: clarkvision.com/articles/astrophotography.image.processing . $\endgroup$
    – Aaron F
    Apr 13, 2022 at 11:18
  • $\begingroup$ Thank you! So am I correct that the focal length isn't just the telescope's focal length, but also the camera's focal length added together? $\endgroup$ Apr 13, 2022 at 16:00
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    $\begingroup$ I think it's just the telescope's focal length that's important. The camera's FL will be very short (a few millimetres) and won't make any difference. $\endgroup$
    – Aaron F
    Apr 13, 2022 at 16:47
  • $\begingroup$ That really helps! Also, would you suggest lower ISO with longer shutter speed or vice versa? $\endgroup$ Apr 13, 2022 at 19:51
  • $\begingroup$ Usually the longer the better. Use the shutter speed from the calculator as a maximum. And the lowest ISO the better. The Orion Nebula's quite bright so you might not even need to go up to the shutter speed that the calculator gives you. Stacking and post-processing can bring up a lot of faint detail. Experiment by taking and stacking only ten images, and cover the lens and take ten more. Use them as 'lights' and 'darks' in DSS and stack them. Open the result in an image editor and use the levels tool to boost the faint areas. $\endgroup$
    – Aaron F
    Apr 13, 2022 at 20:37


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