From: Mark Gaffney <markgaffney@mac.com>

Date: July 30, 2008 8:01:23 PM MDT

To: Astro_IIDC@yahoogroups.com

Subject: Re: [Astro_IIDC] Re: Iterative Polar Alignment

Hi Perry, Sounds like you`re all set up then! I had another go at IPA night before last & arrived at a 1 degree error again after re-adjusting the mount controls. I`d left the star I found nearest to the pole (hopefully Sigma Octans) a little out in Declination as they instructed me to on initial alignment but adjusted it quite a bit in RA (to the east I think). When slewing to Jupiter last night it was still a bit out but not as much as before. (I`d put it a good way off unfortunately, on the previous alignment, 3 nights ago, both in Dec and RA) & the correction on the second run-through was 4.9 degrees from the initial Sync when doing it again 2 night`s ago. I figure I can begin again where I left off when I need a more precise alignment. Solar System Alignment which I`m using for Jupiter isn`t as rigorous! Mark.

On 31/07/2008, at 11:18 AM, hpholcomb wrote:

Hey Mark,

The Starbook-S system allows you up to 18 separate (and/or repetitive) star/planet

selections to properly align the GPD2 for tracking at a single viewing session.

This IPA system uses selection 1 to position on Polaris, then selection 2 for another,

appropriate star, then selection 3 for back to Polaris, then position 4 for the chosen star, 5

back to Polaris, etc., etc., etc., readjusting each time with the Starbook-S's controls &

screen (this can be "zoomed" for more precise adjustment) to obtain proper centering on

the target.  When Polaris finally is centered w/o any adjustment, your mount is PAed.

"Polaris" here either means the star, or the true N offset, which can be seen in the view

through the GPD2's polar alignment scope.  That's a nice touch and should be used as the

centering point for the odd numbered selections for best PA.

At least that's the way it was described to me.  It is a good example of the classic iterative

method to arrive at a set goal or target or whatever.

Perry

--- In Astro_IIDC@yahoogroups.com, Mark Gaffney <markgaffney@...> wrote:

It just occurred to me your mount needs the ability to sync to perform

the process. I don`t know what your Vixen set-up is capable of

exactly! Mark.

On 28/07/2008, at 10:59 AM, hpholcomb wrote:

Can't iterative polar alignment with a GOTO mount be done with Polaris

and another star that is sufficiently separated from P using just the

mount's GOTO program (like Vixen's Starbook-S on my GPD2, for

example)??

Perry

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