Polar Alignment (split from CDC Sky Chart Error Message)

Robert Hoskin <r_hoskin@...>


Re: polar alignment...

During the brief time I tried Explorestars, I tried to use its alignment, and ran into the same issue that I had both years ago, with my old Autostar, and the (several) alignment methods I tried in my PMC-8 era before getting things sorted out.  

These methods all seem to want to want to use stars that are lower in the sky, and are easily obstructed by houses and trees in an urban back yard.  I was unable to use them, and picking alternate stars didn't help, as they were often blocked, as well.

Fortunately, I CAN see Polaris.  Sharpcap can use that, and it works like a champ.  It does the same sort of rotated image plate solving that I believe Polemaster does, and it works with an ordinary guidescope and camera.

Where this leads, is that a method that suits one observing site may not suit another. 

- Bob

From: "hubbell_jerry@... [ESPMC-Eight]"
To: ESPMC-Eight@...
Sent: Thursday, March 29, 2018 10:49 PM
Subject: [ESPMC-Eight] Re: CDC Sky Chart Error Message

Hi Jim,

I don't see any attachment or any other indication of the error in you message. You may have to manually upload the screenshot file (I assume that's what it was) and then provide a link to it in your message. I will have to see the message to comment any further.

I am glad you have it working. If you don't know, the ExploreStars polar alignment routines are a virtual alignment that creates a model within the ExploreStars application for pointing the scope. It does not work when using the ASCOM driver, CdC and ASCOMPAD. The ASCOM Standard platform assumes you have a good physical alignment. Most people are using the QHYCCD Polemaster system to do their physical alignments. 

I have been thinking of ways to incorporate an alignment tool into the PMC-Eight ASCOM driver, but to tell you the truth, it would be on the back burner for a while with all the other stuff I am working on. The source code is available for our driver so a customer with good programming skills could create the code to do this and present it to me for incorporation. I have already included the code for the alignment routine in the project but have done nothing with it.

I would use that code and create an interface to acquire the 2 or 3 star data for the alignment and then add a new transform to calculate the Altitude and Azimuth offsets. I would present those offsets as instructions to the user to  move the Altitude and Azimuth a certain amount in a certain direction that should refine the physical alignment.  This would be like the Polemaster except not as fancy nor as fast perhaps.

The other way would be to do the 2 or 3 star alignment and then calculate the pointing coordinates on the fly like we do in ExploreStars based on the pointing model generated.

Anyway, it would take a bit of work which unfortunately I don't have time for right now, perhaps later on this year in the fall. 

Jerry Hubbell
Director Electrical Engineering
Explore Scientific, LLC.


Hi Bob,

Yes, It is hard to develop and create a system that is all things to all people, or will do what is needed based on the local conditions. We don't have a mount AI that will see where you planted your tripod and figure out the local horizon and then align itself (yet!). So we have to learn enough to realize we setup the correct configuration for our observing session and go on from there. Sometimes the ExploreStars virtual alignment will work fine, other's we may need to do a good physical alignment. There are a lot of factors involved.


Jerry Hubbell
Director Electrical Engineering
Explore Scientific, LLC.