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Equatorial mounts

Started by vikeljay, 12/09/2010 12:33PM
Posted 12/09/2010 12:33PM Opening Post
I just purchased a goto scope with an equatorial mount. I have read the instructions but haven't a clue how to do a polar align. Can someone give me DETAILED instructions on how to do a polar align. I was dismayed that when I pressed the "up" arrow, the scope slewed sideways and when I pressed one of the side arrows, the scope up!
Posted 12/09/2010 03:45PM #1
Depending on what you want to do with it, it can be simple to very complex.

For a fun evening of visual observing:

Set the tripod up so it is as level as possible (not mandatory, but it does make the rest easier.

The polar axis (the bearing around which the Right ascension motor turns) needs to point north. Use a compass or the north star to make it do so.

That axis needs to point high enough in the sky. Again, the north star will work. If you cannot see the north star, make the pointer on the altitude circle point to your latitude. (IN SOuthern California, for instance, it would point to 34 degrees.)

That is enough for a nice evening with the scope.

For astroimaging, however, it can get a whole lot more involved.

Just remember--point the polar axis on the scope to the north star. That is not exactly right, but it will do.

If you have a polar scope, you can get it a lot tighter.

Alex
Posted 12/10/2010 04:25AM #2
If I get Polaris centered in the eyepiece, can I use Polaris as my first alignment star?
Posted 12/10/2010 08:56AM | Edited 12/10/2010 08:57AM #3
James: You made it clear at the outset that yours is an equatorial, not an alt-az mount. But it might help obtain the specific directions you asked for if you identified the make and model of your mount.
For example, I have a German Equatorial Mount for which one can obtain an optional accessory that makes an adjustment for the fact that Polaris is very slightly away from the celestial north pole (about 42 arcminutes) when using Polaris for polar alignment.
For greater precision in polar alignment, it may also be desirable to make sure your telescope's optical tube is mounted to sit absolutely parallel to the mount's right ascension axis, as nearly as possible, and some manufacturers have instructions about steps you can take to achieve that.

NexStar 8i SCT, Orion 80ED APO refractor, Orion 120 mm EQ refractor, 3.5-inch Questar