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Two questions I can't find an answer for.

Started by brian11333, 02/16/2003 01:19PM
Posted 02/16/2003 01:19PM Opening Post
Question 1. I know why Polaris doesn't seem to move much during the course of an evening but it also doesn't seem to move during the course of a year either. I would think that its position in the sky would be signifintly different in December than it is in June but to me it just doesnt seem to move at all.
Question 2. My LX200GPS is mounted on a wedge and it does a great job on centering objects in the FOV. One night I tried to locate an object manualy using the setting circles and I realized that something else is needed besides the RA and Dec because no matter what time it is it points to the same area of the sky. I know I'm missing something but I just can't figure it out.
Posted 02/16/2003 03:08PM #1
Hey Brian, well:

1) Our axis of tilt on Earth is around 23*, and we happen to point almost directly at the North star (for now, it'll change in like 50,000 years). So that causes it to appear to not move during the night.

Because we are SOOOOO far away from Polaris and because our little orbit around our own star is pretty insignificant compared to that distance, Polaris appears to not move anywhere throughout our entire orbit.

If you were to take a string with a ball on the end of it and hold it straight down and make little circles about 3" around with the ball, it appears to move a lot... now stand up really high with say a 300 foot long string and make the same 3" circles... it won't appear to be making very large circles from that far away.

http://www.onr.navy.mil/focus/spacesciences/observingsky/constellations4.htm
http://ms.essortment.com/northstarastro_rmdz.htm

2) You need to "set" your setting circles for them to work correctly. If you have them in a start position of 0 hrs and 0 Dec, then you'll always point to the same position in the sky! What you need to do, is use a star that you know and point your telescope at it. Then use a star atlas and adjust your setting circles so that the readout matches the RA/DEC on the map. That way you have got your setting circles matching the exact orientation to the sky. Now you should be able to just match up some new coordinates, move your scope and away you go!
http://www.astroleague.org/al/astrnote/astnot13.html

I hope I explained them clear enough... if not just keep asking!