Using R.A and Dec

[Celestron_130EQ]

I have had a bit of a Eureka moment regarding my equatorial mount and setting circles. As you may be aware from my previous posts that i had trouble using my setting circles and using "celestial co-ordinates".

So anyway i decided to look on the primer section and found a post about setting up an EQ mount. The link posted Setting Up an Equatorial Mount - McWiki really helped me get a better understanding of the mount. The last section titled "Finding and Tracking Objects" is where I was stuck. I also noticed that he didn't mention using setting circles at all but find objects by moving the telescope about its R.A and Dec and don't pay attention to what it reads.

It finally dawned on me that as long as you polar align your scope you generally don't need to use the setting circles, just move the scope using R.A and Dec axis and if the eyepiece is in an odd position then just rotate the scope to accommodate this. This is actually a good way of using the scope because once the objects insight you can track them using on the fine adjustment levers.

Because of this i can now sleep easier tonight knowing that setting circles are generally un-accurate therefore i should just move the scope along its R.A and Dec axis.

BTW If any of this is wrong please inform me because I would really like to know.

Thanks.

Celestron_130EQ

[Astro Adj]

This is the technique I use on objects that I know the location of and can actually see. Jupiter, the stars that form the Summer Triangle, Polaris and Arcturus are pretty much all of them for now!

However, I think the setting circles will be useful when you want to locate an object that the naked eye cannot detect. I still have a tremendous amount to learn, but I hope that by using the setting circles correctly I'll be able to find objects like the Ring Nebula and Great Cluster in Hercules a little more easily!

Thanks for the link - I found the section on polar alignment very useful indeed!

Cheers,

Adrian

[davo]

Yep polar align. Then set the circles to a star you can see like Vega (cordinates 18h 36m and +38d 47') and from there move your scope to a new target like M57 (using M57's coordinates of 18h 35m and 33d 01')

Setting circles are really great!

[DaveS]

Dec circle is easy, the RA is the tricky one. You really need a siderial clock. Anyone know where to get one ? At short of Pro Laboratory / obsy prices ?

I'm 'scope-less at the moment, but what I used to do was cheat by setting the dec, then sweeping in RA until I picked the target up in the Finder or LP eyepiece. No GOTO in those days, unless you were programing in BASIC (Ugh!).

Dave

[Astro Adj]

Thanks for the tip!

Quick question on RA coordinates - are they absolute or do they change gradually over time? I seem to recall reading that most listed RA coordinates are from the year 2000, and I noticed Stellarium lists two sets of figures. Should I be concentrating on the RA/Dec 'of date' figures?