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Astronomy Science Data, POSS-II
M31, Andromeda Galaxy

POSS-II: M31, Andromeda Galaxy
Coordinates/Direction : RA: 00h42m, DEC: +41o16'
Object size : 192' x 60' (whole image 120' x 120')
Object magnitude : 3.4
Object : Messier 31
Date : 1985 to 2000
Lens/telescope : Samuel Oschin Telescope
Film/CCD : POSS-II, credits: STScI
Exp. time : IR 75 minutes, Red 60 minutes, Blue 60 minutes
Image process tool : AstroImageJ, Fitswork, Irfanview
Processing : Green channel from average of red and blue
Site : Mount Palomar, USA
Comment : Compare what you get from your own telescope, the core of galaxy oversaturated.
More to know : Wikipedia: wiki/ Andromeda Galaxy

Zoom in details:

POSS-II: M31, Andromeda Galaxy
Zoom in details : 1:1 pixel scale
Comment : As you can see if you compare to the earlier POSS-I data this one has higher resolution. The scanner resolution is the same in the blue plates.

Use of the IR spectra as the green output channel:

POSS-II: M31, Andromeda Galaxy
Image process tool : AstroImageJ, Fitswork, Irfanview
Processing : In this image the IR spectra has been used to the green output channel
Comment : It looks that something is wrong or maybe heavy light pollution in the IR spectra. You can get rid of it by doing a background flatten. But anyway the galaxy don't look to have any strong IR sources.

One star (the arrow) looks to be strong in the IR spectra (green). If I identified it correct it's HD4174, it have the spectral class M3, a red subgiant.
More to know : Spectral classes: wiki/ Stellar classification
Star HD 4174:
Spectrum of HD 4174: article/ 10.1086/ 126211/ pdf
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