Help needed using EQ5

[Redshift (Phil)]

On my recently purchased EQ5 mount there are two scales, one for declination and one for ascension.
Can someone please advise me how to correctly set up these scales and how to use them to find objects.
Thanks

[bojan]

Before we start, is your EQ5 motorised? If yes, can it be connected to a computer?
If no, the scales (those are actually called "setting circles") will be important.

If yes, they are not because you will be finding whatever you like with the help of the computer, and we will certainly help you here.

[Redshift (Phil)]

I've just taken up this hobby so I'm not yet into motorised/computerised gadgets. So, its the setting circles I would like to learn how to use first up.

[bojan]

OK.. this is a good start, because you will have to learn some spherical astronomy first, which is good for undestanding things..

Fistly, in order for the setting circles to properly function, the mount needs to be rectified - or aligned.
That means, the RA shaft (or, more precisely, hour shaft) has to be paralel to Earth's rotational axis. Or, it has to point to SCP (South Celestial Pole), a point around which all the stars appear to be circling in 23h 56'.
This can be accomplished by using the polar scope that your mount has (you have to remove the covers to expose it first).

You can find some basics about spherical astronomy here:
http://www.physics.csbsju.edu/astro/CS/CSintro.html
The website is a bit northcentric, but you just have to substitute North with South and the rotation of the celestial sphere will be of course in oposite direction.

Also, you can try here:
http://en.wikipedia.org/wiki/Spherical_astronomy

[bojan]

The circles on your mount are for Hour angle (this one is on the shaft that is at the angle) and Declination (the shaft perpendiculat to the first one).

Declination is easy: you just have to set the Dec angle of the object, found in the catalogue.
Rectascension is trickier: you will find this number in catalogue, however what you will be setting on the circle is Hour angle - and this number must be calculated from Rectascension and Local Sideral time.
Formla is:
Hour angle = Sideral Time - RA

Local sideral time can be calculated from your geographical position and local time.
In the past this time was kept by means of accurate clock.

[bojan]

Before you start looking for objects, the setting circles have to be adjusted as well.
This can be done by pointing the telescope (on the already aligned mount) to a object with known coordinates. Then you adjust the circles by rotating them such that they show the same coordinates.
After that you are ready for a hunt :-)

[Redshift (Phil)]

Thanks for that advice. It sounds a bit tricky but I think your instructions will help a lot. Its all part of the fun of it!

[bojan]

No worries.. and clear skies :-)

[bojan]

Phil,
Here you can calculate your local sideral time:
http://tycho.usno.navy.mil/sidereal.html

[Redshift (Phil)]

Thanks again. I found a Widget for a sideral clock for Mac computers. It seems to work OK and constantly updates the time. No internet connection required. You can find it at:
http://mac.softpedia.com/downloadTag/sidereal+time