Re: Precise polar alignment of the azimuth axis

Roland Christen

The Daytime alignment is not precise enough to use for aligning the RAPAS. Drift alignment is the best way. It takes a bit of time but once it is done, you don't have to do it ever again after aligning your RAPAS.


-----Original Message-----
From: John <obee11@...>
Sent: Mon, Dec 21, 2020 3:40 pm
Subject: Re: [ap-gto] Precise polar alignment of the azimuth axis

Aloha All,

  Well, I was able to get the new Mach 2 out for the first time over the weekend.  So far so good!  Still re-learning the ropes.

  I need to make a slight adjustment to the RAPAS, plus I wanted to check my current polar alignment using "Roland's GTO Quick Star Drift Method" (which can also be found in the  Mach 2 User Guide, Appendix C, pg 41 [dated Aug 2020]).  I used Sharpcap's polar align routine on my C8 Edge at F/7 with an ASI 1600 camera which puts the image scale at 0.55 arc/sec per pixel.  Last night (and Sat night) as a test, I was actually able to get 8 min unguided images without any oblong stars!  Sharpcap says I'm within 0.5 arcsecs of the pole, but I don't trust it too much due to possible orthogonality issues (or cone error) with the C8 edge.  Not sure if that's the same thing.

  Anyway tonight, I was hoping to check my current polar alignment with the Quick Star Drift Method, but I'm a little confused as to which calibration star to pick (for the AZ adjust part).  I was planning on using Alpheratz for the first star near the Zenith, when it is on the West side of the Meridian.  But when I push the scope South, towards the second 'calibration star,' I'm having trouble visualizing which star to pick.  Do I pick a star that has the same RA coordinates as Alpheratz?  Also, when moving the scope to the second star in the South, does it matter if I manually push the scope there or can the keypad be used to slew it there? 

  Once I get this done, I might try the other "drift alignment - ra correction method" that's mentioned on page 40.  All I'm trying to do now, is get the RAPAS really dialed in. So in the future, I'm hoping I can get polar aligned with just the RAPAS and then jump right into the modeling!  Thanks any sorry for the long email!


Roland Christen

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