Quote:
Originally Posted by -George-
Hi, If I may ask...
The moon is 1/2 degree in diameter looking at it with your eyes. That means mars through the telescope at 1 degree should look like 2 moon sizes by eye - no scope.
A moon generally looks big at night... if mars is 2x the size of that (1 degree vs 1/2) then Mars should look absolute huge. I am confused on this degree business.
And when is the moon 1/2 degree because some nights it looks as big as the sun. So what is all this degree based on and why isn't mars double the size of a big moon since its 1 degree not half?
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OK the Moon is 1/2 degree in diameter or 30 minutes of arc. One degree = 1/360 of a circle. (360 degrees in a circle).
Note:
1 degree =60 minutes of arc
1 minute = 60 seconds of arc
1 degree = 3600 seconds of arc
MARS WITH THE UNAIDED EYE WILL NOT LOOK TWICE AS BIG OR EVEN AS BIG AS THE MOON WITH THE UNAIDED EYE. This is important as there is a hoax that goes around every Mars opposition claiming so.
Lets just forget about Mars for the moment and look at the Full Moon without any telescope or binoculars, i.e. unaided eye. It fills 1/2 degree of sky. How much detail can you see? You should be able to see the dark and light markings easily but no craters. If the Moon was twice as big OR twice as close OR you magnified by 2 you would get a 1 degree Moon and you may be able to make out the larger craters.
Now back to Mars. With the unaided eye it is 15 arc seconds in diameter. This is 15/3600 = 0.0042 degrees in diameter. Very small and for all intentional purposes a point of light.
Magnify Mars by 120x i.e. 0.0042 x 120 = 0.50 degrees. Mars will appear THROUGH THE TELESCOPE the same diameter as the MOON when the Moon is viewed unaided.
Magnify Mars by 240x i.e. 0.0042 x 240 = 1 degree. Mars will appear THROUGH THE TELESCOPE the twice as big as the MOON when the Moon is viewed unaided.
This is easily observed when Mars and the Moon are in the same part of the sky. Look at Mars through the telescope with one eye at say 120X and look at the Moon unaided with the other eye. They will look the same diameter. (This is easier if the telescope is a refractor or SCT with no diagonal, i.e. straight through mode.
Therefore you should be able to detect detail even at 120x on Mars although the more magnification the better provided seeing is good and the image is not too dim.
I hope this clears things up.