Reference directions for finding objects?

[Barry W]

Hi all,

I'm looking for some confirmation. Many references say "2deg south" or "just east" of xxx (for example) when giving directions for finding objects. I'm pretty sure this refers to the Celestial grid (ie celestial equator) rather than our terrestrial coordinates. I'm using a Dob and everything is manual in alt az. Is my thinking right or am I off the mark?

Thanks

Barry

[adamsp123]

I would think if using coords in the "heavens" it is always based on the celestial coordinate system (RA+AZ) but if it is from an existing object then it is relative from that original object.

[proflight2000]

Hi Barry, on some star sotware you have the ability to draw a line from one star to the next which gives the angular seperation, im not sure if thats the idea you want. I also tend to use the clenched fist approach of one fist being roughly ten degrees of sky. So I will have the horizon as 0 and place my fist at arms length to the horizon, that is = to 10 degrees, use it to measure polaris for instance, my location places polaris at 51 degrees, that works out the same with the clenched fist.

[Talitha]

Hi Barry, you're right.. the directions refer to the celestial coordinate grid.

Alt-Az directions are constantly changing, because that system uses your location and time, whereas the celestial RA/Dec system is universal and is the same for everyone, everywhere.

[Barry W]

Thanks,It looks like I had it correct in my thinking. For example, Orion's Belt is on the Celestial equator and the he's facing west, with Auriga to the north. Converting this to alt az is not too bad. It's just that I've tried looking for some things based on books or some web directions and things didn't quite make sense. I was looking at one of the uploaded sketches in the observation zone, comparing it to one of the Orion Nebula I just tried. The west pointer confused me a bit and I thought I was orienting myself wrong (I'm at 48 N and should see roughly the same sky as the UK majority on this forum).As long as you say the norm is to use celestial grid, I'll keep going with that and plodding happily along.

Cheers,Barry

[Talitha]

No, your not orienting things wrong, Barry. Stef's eyepiece view is mirror-imaged, which is why West is on the left in his sketch. Amateur 'mental gymnastics' is a kick, isn't it?

[Barry W]

AAHHH! Cool. Looking forward to scanning some of my own projects into the computer now.

Thanks