Quote:
Originally Posted by DavidTrap
Ok,
Finally found the time to play with the photometry feature of Maxim.
Using some reference star magnitudes from SkyX, I measured the magnitude of the object at 16.4.
Any suggestions as to why my measured value is over a magnitude lower than what you have measured??
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David,
Well first of all, what kind of magnitude is it that you were measuring......
B ? (approximates a blue-sensitive photographic plate)
V ?? (approximately yellow-green light)
R ??
I ?? (about 800nm)
These above are Johnson-Morgan-Cousins magnitudes that are in common use, and often plotted in star atlas databases.
Each type of magnitude corresponds to a specific bandpass (filter) with a specific transmission curve.
Other magnitude systems are also possible, for instance the Sloan Digital Sky Survey magnitudes
( u , g , r , i , z)
It is possible to interconvert one type of magnitude to another, and I used to have a crib sheet at home that allowed me to do this with the greatest of ease......though I am "away from home at present," so I would have to look up the conversion elsewhere.
The conversion can also depend on the colour of the object, for instance a Very Red object has B-V = 1 to 1.3 while a Very Blue object has B-V of 0.5 or less.
Oh, and one more thing (added in edit):
Sky transparency and the altitude of the object can also make a big difference to its measured magnitude.