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Old 22-11-2014, 02:01 PM
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HenryNZ is offline
Join Date: Nov 2014
Location: Auckland, New Zealand
Posts: 57
How good is polar alignment with a polar scope for imaging in Southern Hemisphere?

Hi first post here. I have been visiting this forum for a while but have been mostly posting on cloudynights. However, I would like to get some more local comments on this particular topic, as I found the Americans have a hard time understanding the nature of the problem...

When I bought my mount (ioptron ZEQ25) the dealer says it does not come with a polar scope because there is no point having one in Southern hemisphere. I have since been using alignmaster and PHD drift alignment to get polar alignment for imaging. While alignmaster is quick and dirty, I find that it is limited by the goto accuracy and the backlash of the mount (poor in the case of ZEQ25), and never get perfect alignment with it for this reason. PHD drift alignment is a pain and slow, but with better and usable accuracy. However even with multiple iterations (taking up to 45-60 minutes), I can get at best within 5 arc min. Typically PHD2 will report sub arcmin alignment on the Az and Alt axis individually but when actually imaging there is still drift. I suspect it may be cone error or perhaps the mount is not level / squared or something - I am not sure why.

My question now is, is there any point actually spending money on a polar scope? I have never been able to see sigma octantis with my naked eye but can you see it thru a polar scope? The North Americans seem to be able to get workable polar alignment within couple of arc min using polaris (i.e. better than what I can get with PHD2 drift in 45-60 minutes) - can the same be achieved using a polar scope with sig oct in Southern hemisphere? If so, I may as well use a polar scope and save myself 45-60 min of precious imaging time.

Or is there a better way to get better alignment for imaging (with a portable setup).

Many thanks

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