Quote:
Originally Posted by dpastern
Bojan - I'm not sure what you mean by aligning with the built in polar finder during the day. How can I do that when the stars won't be visible to align against, or am I completely misunderstanding you?
Dave
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The problem is, polar scope is usually not aligned at the factory (that was my case as well).
What I did was, I pointed the polar shaft of my EQ6 mount to a distant roof (20-30 metres away) , so that the top was near the centre of the FOV of the polar scope.
Then, by rotating the shaft by 90 degrees back and forth, and adjusting it left-right and up-down, I directed the axis exactly on the top point of that roof.
The next step was to adjust the cross of the reticle to coincide with that point of the roof.
If you are doing this you have to be careful with reticle, it is easily damaged if the grab screws are tightened too much. Also, there are three screws - not very convenient for adjustment (it would have been much better if there were 4) but it is possible to do, and it has to be done only once.
Then you can use polar scope when you are away from home, it is pretty accurate - I do not have problem at all with 1 minute exposures. The bigger problem will be periodic error in the main worm gear.
For the compass, I mounted it on the 0.5m long Al rod, which can be screwed onto and removed easily from the mount RA shaft . For Melbourne, the difference between true South (North) direction and what needle is showing is 11 degrees to the west, so this has to be taken into account. Once adjusted, you leave compass alone on that rod for the next session
And of course, you should make use of the build-in bubble level (it comes with newer mounts, if yours does not have one, you should definitely place it on the RA shaft, and it should be adjustable. you should null it when you have RA shaft pointed exactly (or near enough) at SCP.
This way, you have to align your mount only once. Next time only bubble level and compass are enough, even if you go somewhere out of the city.
However, if you go couple of hundred kilometres to the South or North from your home, you should check the elevation or RA shaft, the difference in elevation will abe significant and quite visible in the polar finder (and on your photographs as well)