Quote:
Originally Posted by j.skett
David
Appreciate the effort you put into your post, and I have read through it several times, however it goes over my head like a F18 Hornet, especially the continued mention of Declination.
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Ah ha. Now we're getting somewhere. You need to start by understanding the basics of positional astronomy. That will stand you in good stead, not just for this question but for many other uses (finding objects, working out when they are visible etc). Years ago I wrote the 'Sky this Month' for my local club. It was pre-computer and so everything was done manually - tables of siderial time from Nortons Star Atlas, semi-diurnal arcs from the ASNSW Yearbook (itself produced manually by the great Ed Lumley) and poring over the Skalnate-Pleso Star Atlas. That really banged the concepts into my boney skull.
Quote:
Originally Posted by SkyWatch
Hi Jim,
Substitute "latitude" for "declination", and "longitude" for "RA (right ascension)". Not exactly the same thing, but gives you the idea. Alternatively "up and down (North/South)" for "declination", and "sideways (East/West)" for RA...
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Yes, RA and Dec are analogous to longitude and latitude (respectively) but they are not the same. One applies to the surface of the Earth and the other to the celestial sphere. If you don't separate the two you will soon confuse yourself. If you want to know whether an object of a given declination is visible from your latitude it will confuse the hell out of you if you start thinking 'what latitude is visible from my latitude?'
I suppose you understand this but, for the purposes of positional astronomy, we are on a sphere inside a sphere. A lot of this discussion revolves around what part of the outer (celestial) sphere is visible from our position on the inner sphere (the Earth). And, if the lines of RA and Dec were painted across he sky how would they appear and how does that change as we move to a different latitude.
Don't give up, if I could eventually understand it, so will you!