Re: An easier Pasillx N & S Polar Alignment method


Joe Zeglinski
 

Thanks Hank,

Actually, I tried using my green laser pointer (GLP) as a test, by firing it into my Questar-7 Maksutov, thinking it would work the same as one of the US observatories did, hitting the "Laser Ranging Array" retro reflector package left on the moon. However, either my 5 mw laser beam was too weak, or was bouncing directly back from the secondary spot on the corrector, but in any case the ad hoc test failed. I couldn't see the beam pointed at Polaris. I thought perhaps I needed to disperse the laser in a wider beam with a pellicle lens, or some such. I must say, your approach with the PAS seems like a good one.

But I don't see why you shoot through the PAS itself - isn't it just as easy to simply rig up a holder for the GLP to fit into the mount in place of the PAS? You would need the jig in either case, and I don't think the PAS optics add anything to the laser beam, other than slight attenuation. It would be nice if it would project the PAS reticle on the sky, like a BATMAN Signal. Just kidding <g>.

As for the comfort in using a lawn chair for the task of lining up Polaris in the PAS, I agree that would be easy but only in regions of lower latitude, ideally at the equator. Further north/south, when the PAS is set at 45 degrees or higher elevation, there is not enough room for a chair next to the pier, while the risk of craning the neck at such an S-bend is liable to cause not only back ache, but also potential neck injury - I tried that.

I am eager to try out my idea of using the RGH guide camera with the PAS, just as soon as my recent back injury lets me out of the house, hopefully before winter. So far, I am getting a better view of the floor, than the sky :-)

As an alternative, I did consider getting a Meade "Electronic Eyepiece" with an NTSC video output to a small monitor, avoiding use of a laptop and CCD imager. However, at 320x240 resolution, I suspect that the dim stars will be barely visible, or they will pop in and out of view. Besides, I suspect most owners of an AP mount are likely to be imaging, and the ubiquitous laptop and guide camera are going to be readily available. In fact, SBIG has a free downloadable "Seeing Program" for use with their SBIG-402 (or other imagers) on Polaris - I thought that could be a bonus at the start of a night, since the guider is already set on the PAS.

Finally, if used for just visual observing, polar alignment is not that critical, and it might suffice to use the old "boy scout trick" - stick a wet finger in the air and test which way the solar wind is blowing? :-)

Cheers Hank,

Joe

----- Original Message -----
From: "Hank Sielski" <hsielski@...>
To: <ap-gto@...>
Sent: Wednesday, September 17, 2008 6:28 PM
Subject: Re: [ap-gto] An easier Pasillx N & S Polar Alignment method


Joseph,

Joking aside, a taller pier or using an astrochair to sit lower might help.


If you move around in latitude a bit like I do (between northern and
southern California), or find that your altitude (or azimuth) is way off for
some reason, I find that shooting a green laser up through the PAS helps to
get Polaris close to the center of the FOV of the PAS without
kneeling/bending. After that, then you still need to look through the PAS
to get Polaris moved to the offset area and align the other two stars.

Even if you can't do this later part (bright skies, or whatever) , you still
might be able to use the meridan delay or two star method (documented in the
manual) to get even closer.

After that, you can do a drift alignment, if you need to, but this isn't
necessary if you're only going visual.

Beyond that, I think you'll have to resort to something with software on a
PC and a camera to zero in your polar alignment (Pulseguide, Pole-Align_Max,
etc. lots of choices here).

The idea to use to hook up a guide camera to use as a video finder or
something seems interesting...let us know if you get something working.

Hank

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