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Old 17-06-2015, 03:34 AM
skysurfer's Avatar
skysurfer
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Best polar alignment star ?

For astrophotography I use a polar scope of the Vixen Super Polaris mount of 25 years old. There is a template in it showing northern Polaris plus the trapezoid consisting the south pole star sigma Octantis, but calibrated for epoch 1990.

But due to the precession the template is outdated but the arc minute scale and the center cross (which should match the celestial pole) are still usable.

So in the northern hemisphere I put the cross to 40' from Polaris at the right RA.

In the south I use BQ Octantis, much closer to the pole (only 14' now, 10' in 2027) which is +6.9 and easily visible in the polar scope. No such star visible in the polar scope exists closer to the North pole than Polaris.

And, when using BQ set to 14' off-pole at the proper RA, the mount is very well polar aligned.

Does somebody use this star as polar alignment ?
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  #2  
Old 17-06-2015, 06:04 AM
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troypiggo (Troy)
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FWIW I've never used my polar scope. Drift align every time. I would have thought that 1990 positions would get you close enough, then tweak with a drift align using your guiding software.
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Old 17-06-2015, 05:41 PM
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Atmos (Colin)
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25 years of stellar drift is almost negligible when it comes to polar alignment. This is in part due to general inaccuracy that you'll find in your polar scope and just matching stars.
A polar scope, whether brand new or 25 years old is likely to get you very close but not as close as a drift alignment will.

From where I live (Melbourne Northern Suburbs), I cannot see any of those stars without a telescope anyway! Too much light pollution.
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