Alignmaster and precession

Galah (Patrick) · #1 07-02-2014, 07:09 AM

If I am correct, coordinates in the stern.txt file appear as J2000. CPC1100 requires that coordinates sent be JNow.

In attempting to solve some other problems, just to be certain, can I assume that these Alignmaster coordinates are converted to JNow prior to transmission to a telescope?

Regards,

Patrick.

BlackWidow (Mardy) · #2 07-02-2014, 09:04 AM

Hi Patrick.

I am not really sure if the program makes any adjustment for the current star positions in terms of Epoch, it may very well do so. However thier are very smack changes over time to make any great effect. You could go to the Alignmaster website with your question.

Alignmaster with the expanded star list is using Epoch J2000 and most of us have been using that for some time without any problems. In the last couple of days I posted an updated list still using the original J2000 epoch. However I changed about 13 of the star names to more common names.

I often use my Ipad ans starwalk to find the alignment stars and had troubles finding the names Alignmaster used in Starwalk. So I spent a few hours changing the sterne file with star names that could be found in starwalk. This makes it a lot faster to find you alignment stars.

If you can't find my post and want the file I can post it again

Regadds
Mardy

Galah (Patrick) · #3 07-02-2014, 05:59 PM

Hello Mardy,

Thanks for that. I have emailed Mathias.

You are probably correct about the small changes. However, using C2A (which calculates for precession) as a reference I find the following differences for (e.g.) Hadar

Alignmaster (J2000) C2A (eq of date)

RA: Alignmaster 14 03 41.4 C2A 14 04 50
DEC: Alignmaster 60 22 23 C2A 60 26 25

Regards,

Patrick.

Galah (Patrick) · #4 08-02-2014, 07:32 AM

Regarding the epoch usage within Alignmaster, I queried Mathias as follows:

"Coordinates in the sterne.txt file appear to be as J2000. Are these coordinates precessed to Jnow prior to being transmitted to a telescope."

His reply: "Yes you are right, the coordinates are J2000 and will be converted to Jnow."

Patrick.

BlackWidow (Mardy) · #5 08-02-2014, 09:15 AM

That's useful info.. I thought that might be the case but could not be sure.. I did know you could not mix Epocs in the sterne file and this clearly is the reason.

When I made my new list I stuck to the J2000 epoc but thought it could also be due to so little change over this short time... Seems that's not the case as it adjusts it to now...

Thanks Patrick