What DP wants from a PA prog

[Demonperformer]

I have been thinking a lot about polar alignment recently, particularly what (IMO) is good and what is not so good about the PA procedures of Alignmaster & Astrotortilla, and the fact that any errors in PA will be constant for every star in the sky for a given setup. It seems to me that there are good bits to each and that a hybrid prog that combined these good ideas might be stronger than either.

I am therefore attaching a pdf "discussion" document, listing my thoughts. Any (constructive!) opinions on the content (good or bad) from anyone would be welcomed.

This document contains none of the math or programming that would be required, just the basic concept and workflow. I will worry about acquiring (or "buying in") those skills, depending on the feedback.

Thanks for looking.

discussion_doc.pdf

[michaelmorris]

Sounds great.  One idea for an even easier to use approach.

Add a one-off calibration step for a given mount/telescope/camera combination.

1. Input data on scope/camera into software.
2. Centre on a star
3. Plate solve this.
4. Move Alt adjustment a set number of turn clockwise
5. plate solve resulting star field
6. Move Az adjustment knob set number of turns clockwise
7. plate solve resulting star field
8. Software calculates offsets and saves data for later use in all polar alignment sessions using this set up.

Now software can recommend number of turns (and direction) on each axis to get polar aligned

I think this would work!

[Demonperformer]

Thanks for the response, Michael.

I see where you are coming from, and I guess it would certainly be possible to include something like that. I must admit I am unsure, however, as to how beneficial it would be in practice.

My only experience is with the NEQ6 and a scope with a telrad, so I may be missing some benefits here. I think these recommendations would only be of use for getting it to the point where it appears on the screen ready for the final precise repositioning. But would such recommendations be adequate to do that? 2' in azimuth is about 1/70 of a turn (~5^o) [see http://stargazerslounge.com/topic/197563-is-my-maths-right/], so that much precision would be necessary to get the star onto the screen. The computer could surely give that much precision, but having the manual dexterity to achieve it ... I'm not so sure. And if I'm going to have to use the telrad anyway, is this really adding anything?

The other alternative, of course, would be to increase the angular size of the image to maybe 5' or 10' - this would give lower precision, but would possibly be a more practical figure. Afterall, my reticle eyepiece has a radius of about 9' and using the telrad I tend to get a star about 50% of the way to the centre, which is a massive (compared to a 2'*2' field) 4.5'.

[Thalestris24]

Sounds great.  One idea for an even easier to use approach.

Add a one-off calibration step for a given mount/telescope/camera combination.

1. Input data on scope/camera into software.
2. Centre on a star
3. Plate solve this.
4. Move Alt adjustment a set number of turn clockwise
5. plate solve resulting star field
6. Move Az adjustment knob set number of turns clockwise
7. plate solve resulting star field
8. Software calculates offsets and saves data for later use in all polar alignment sessions using this set up.

Now software can recommend number of turns (and direction) on each axis to get polar aligned

I think this would work!

Hi

I suspect #4 and #6 would be neither precise enough nor reproducible... I imagine that's why Astrotortilla slews a fixed distance and leaves it up to the user to twiddle the knobs. From experience, drift aligning without platesolving seems more reliable .

Louise