In this question an image is shown (repeated below) which gives an idea of the "true" angular extent of the Andromeda galaxy in our sky.

When I see Andromeda it is usually a bit of a smudge perhaps the size of the full moon, presumably because I cannot see much beyond the bright nucleus and bulge of the galaxy.

Being a stellar astronomer, I have never thought much about the practicalities of seeing extended objects in the night sky.

My question is: what kind of observing conditions would allow me to see Andromeda with an angular size of $\sim 5$ degrees? Would it be sufficient to get to a really dark site with the naked eye, or would I also need to be looking for it with binoculars or a telescope? Or is it something where you must take a picture and do some processing to eliminate the general sky background?

EDIT: To be clear, I don't want my question reading back to me - as in "you can only see a smudge with the naked eye"; what I want to know is the observational conditions/instrument I need to able to see a several degree diameter Andromeda galaxy; preferably with the evidence?

Andromeda vs the Moon


2 Answers 2


Would it be sufficient to get to a really dark site with the naked eye

In my personal experience, I have seen Andromeda Galaxy as a quite bright dot, in a hill station 2133 meters (6998 feet) above sea level with almost no light pollution, although the town is said to have light pollution of Class 2 in Bortle Scale. But it is not possible to see the disk of the galaxy with an unaided eye, the light gathering capacity of eye is very limited, like @PM2Ring states, the "Refresh rate" of our eye is around 1/10 of a second. Typically in an excellent dark sky, A binoculars would help to see some details of the galaxy. Or else a camera with a good zoom lens or with an Amateur telescope for an exposure of just 1 minute - 5 minutes can fetch enough details of the galaxy. Here's how it would look like. (It may look slightly better than the image below)

enter image description here

Suppose if you want to see Andromeda galaxy as something like this:

Image from Space.com

Then a Series of long exposure images have to be stacked or Curve stretch by some editing.

  • 1
    $\begingroup$ Can you put an angular scale on the picture? $\endgroup$
    – ProfRob
    May 20, 2022 at 8:10
  • $\begingroup$ @ProfRob You mean a scale to measure its apparent angular size in the picture ? $\endgroup$ May 20, 2022 at 10:53
  • 1
    $\begingroup$ Without angular scales on the image and details of how the image was obtained, your pictures are meaningless. I suppose I could try and work it out from the foreground stars but I'm not going to. $\endgroup$
    – ProfRob
    May 20, 2022 at 19:19
  • $\begingroup$ @ProfRob I have obtained some informarion and will soon add it in the picture $\endgroup$ May 21, 2022 at 4:04

You'd need new eyes able to collect vastly more photons. Barring an alien eye transplant, a large telescope mirror with a low power objective lens gives a reasonable view of the Andromeda galaxy in real time, but it will always be "smudgy". Alternatively, a long exposure with a 35 mm digital camera on a moonless night will also do the trick, collecting more photons over time. Alas, human eyes need help from technology!

  • 2
    $\begingroup$ As it’s currently written, your answer is unclear. Please edit to add additional details that will help others understand how this addresses the question asked. You can find more information on how to write good answers in the help center. $\endgroup$
    – Community Bot
    May 19, 2022 at 17:54

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