Guys....
50mm FL is 50mm, ALWAYS.
Also, F-number is always the same, as it is the ratio between lens FL and lens diameter.
Both those numbers are the property of the lens ONLY.
Please forget about that crop factor nonsense.. which is creeping into our discussions every now and then. Very confusing and misused term, it may have some relevance in everyday photography (and among people who do not have proper understanding of geometrical optics), but in astrophotography it should never be mentioned.
The size of the sensor (in combination with FL of the said objective lens) will determine the field of view for that particular camera-lens combination (and this can be calculated by using simple trigonometric relations), and it will be expressed in degrees (for frame diagonal, or frame hight, or frame width).
The sensor resolution for the same camera-lens combination , on the other hand, will be determined by pixel size and lens FL (again the same trigonometric relations will apply), and this will be expressed in arcsec/pixel or pixel/arrcsec. This of course should not be mixed with optical lens resolution (which depends on lens quality)
The excel file which does some field size calculations (and pixel resolution or scale0 could be found in the following thread:
http://www.iceinspace.com.au/forum/s...ht=crop+factor