Setting circles on EQ mounts

[kosh]

Hi All,
A quick question about ther setting circles on GEQ mounts.

1. Are the setting circles supposed to be able to move independently of
the physical RA/DEC axis, and if so, doesn't that throw the co-ords off
when trying to locate an object?

2. What exactly is the "Start position" physically before Polar alignment and
what should the numbers on the setting circles display? ie. 0hra, 0deg dec?

The reason I ask is because a number of the 'Value' scopes that i have
seen in stores are on EQ's who's setting circles are not really fixed and this
seems to not make sense (to me, a newb).

The second question is because I have no one to physically teach me about
using a scope properly so I want to know how to start correctly otherwise
all those RA/DEC co-ords that find in mags etc wont mean a thing.

Thanks.

[[1ponders] (Paul)]

Hi Kosh.
Your Dec circles should be fixed so that when you point at the celestial equator it reads zero and at the south celestial pole it reads 90 (-90 actually). The RA circles do rotate.

To use them you need to center on a known star, find out by looking in a book or on the internet its RA coordinates, then rotate your RA circle so that the marker on your RA axis is pointing to those RA coordinates. The RA then rotate as you move your scope. The hardest part it trying to work out whether the inner numbers or the outer numbers on your RA circle represent the southern hemisphere. I can never remember, so I find out the RA for two known stars, center one then set the RA coordinates to that star (inner or outer it doesn't matter, but for this exercise let say inner ones). Then swing to the second star. If the new RA coordinates match the RA of your second star then you've selected the right ring of numbers. If it doesn't then use the other ring (outer this time). Set to your second star and then swing back to the first and its RA should match with the ring. I don't use the scope setting circles very often so I don't bother remembering which is the right ring of RA. If your going to do it regularly then place a mark on the correct ring of numbers.

[atalas]

Hi Kosh

The setting circles will be set after you polar align ,basically you go to a bright star of known RA and Dec set the circles and off you go ! once you set the RA of the star in your once time setup ,you lock the RA screw. IF you look closer you will see that there is two sets of numbers on the circles ,we use the top set in the South If memory serves me.
I believe that If your motor drives are turned off ,you need to do the setup again.
Just another reason to learn how to polar align perfectly !

Louie

[[1ponders] (Paul)]

Your "home" position for polar aligning is 90 deg Dec and with the counterweight shaft vertical. The hardest part is identifying sigma octanis near the pole. That takes a bit of practice. IF you're able to once you've completed your first polar alignment and your happy with it, mark the ground where your tripod legs are. Plus mark your tripod legs for the height they are at. That way if you fold it up and bing it out again one day you have some reference marks to set up to again that will probably be close enough to polar aligned for visual work.

[kosh]

ok cool. My old EQ mount had setting circles which moved at a different rate than
the physical axis wich totally threw my co-ords off. That's why i'm confused.