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Polar alignment southern hemisphere


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#1 lukepower

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Posted 11 May 2019 - 10:10 AM

Hi guys,

 

I have an interesting observation I made when trying to polar align my DDM60 mount in Namibia (southern hemisphere): Following the usual approach (Sequence take some points, then solve, and do the "Move star Now" to center the selected star with the mechanical dials of the mount) I noticed that I was somewhat moving the star in the exact wrong direction. It was like when recentering the star and doing a new pointing run the Polar Alignment error was doubled as compared to before. Am I doing something wrong?

 

Maybe other users from the southern hemisphere can comment? Also, I seem to have issues getting the AutoPoint function to work properly within Sequence.

 

Best regards

Lukas


Lukas Demetz
------------
www.skygemsobservatories.com
Astro Dolomites Observatory, Skygems Network
Santa Cristina Valgardena, Italy
20" Cassegrain-Newton on ASA DDM85XL


#2 MarkS

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Posted 12 May 2019 - 05:45 AM

Hi Lukas,

 

I'm not sure I understand what is happening here, so I'll just outline my approach when first setting up my mounts:

 

I used the GPS to tell Autoslew the mount location, and set Sequence to get coordinates from Autoslew. As the mount comes set for the Northern Hemisphere, I got a message from Autoslew saying that it has detected it is in the Southern Hemisphere and asks if you wish to change the RA motor direction. After confirming, the system does what it should: PA and Autopoint work correctly.

 

I assume your DDM60 has relative encoders. The initial set-up must be done with the counterweight pointing west - but I'm sure you know that!

 

Hope this helps.

 

Mark



#3 lukepower

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Posted 12 May 2019 - 06:40 AM

Hi Mark,

 

thank you for your kind answer. My issue is that, following the procedure (as you outline) I get a given error in Alt and Az. Then I center a star, hit "Move Now" so that Autoslew moves to the position the star should be, and do the adjustments with the baseplate. Once I have the star centered, and do a new clean pointing run for the polar alignment, my error in Alt and Az grows instead of becoming smaller :) Basically I am confused on whetever I am doing something wrong here :)


Lukas Demetz
------------
www.skygemsobservatories.com
Astro Dolomites Observatory, Skygems Network
Santa Cristina Valgardena, Italy
20" Cassegrain-Newton on ASA DDM85XL


#4 MarkS

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Posted 13 May 2019 - 01:12 AM

That is weird!

Does the error increase in the same direction as the initial error, or is it an 'over-correction'?

Does the mount go in the right direction when you slew to a star? (It should, regardless of PA errors)

It may be worthwhile to remove your ini files for Sequence and Autoslew to a stick, then do a complete initialisation of both programs from scratch.....

 

Perhaps someone else has a better idea :wub:

 

Mark



#5 lukepower

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Posted 13 May 2019 - 07:52 AM

It is basically a correction in the wrong direction. I have to try it again once I am there (it is a remote system), but it is weird...

I am gonna try to do a comparison run with TPoint/TheSkyX as that might at least give me a pointer whenever it is an ASA issue or my own fault :)


Lukas Demetz
------------
www.skygemsobservatories.com
Astro Dolomites Observatory, Skygems Network
Santa Cristina Valgardena, Italy
20" Cassegrain-Newton on ASA DDM85XL





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