Thread: Polar alignment
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Old 06-01-2014, 06:46 PM
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mithrandir (Andrew)
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Join Date: Jan 2009
Location: Glenhaven
Posts: 4,161
There are several things you need to have right, or at least almost right, with an equatorial mount. A GPS either built in or attached simplifies much of it.
  1. If you are using a tripod one leg must be pointed towards the pole and the counterweight shaft will be above it.
  2. Do not trust any levels built in to the mount, at least not without testing them with a real spirit level. It doesn't have to be perfectly level but close helps.
  3. You need to know your latitude and longitude. You can get it off many smartphones if you don't have a GPS. Make sure you get the signs right for both lat and long.
  4. You need to know the time. Again your phone will do if you don't have a GPS (exact time is critical for mobile phones to work). When entering the time make sure you get the UTC offset correct for your location. Don't forget DST. I set my mounts to UTC and ignore local time.
  5. The polar axis has to be running north/south. You can get close with a compass and the correct magnetic variation but this can be completely bollixed by any iron objects nearby. The Solar Noon method is more reliable. I found that the pavers around the pool run almost exactly N/S and E/W so the joins get me close enough.
  6. The polar axis has to point at the pole. The scale engraved on the mount should get you close. I have a digital level that I sit on the dovetail.
Once you've got that down pat the scope's alignment routines should get you up and running reasonable quickly.
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