Tracking Graph Diagnosos


M Hambrick
 

I ran an unguided tracking graph on my 1100GTO (non-AE) mount for about 12 minutes last night to see how much drift I am getting. I am assuming that the drift in each axis is due to the polar alignment being off, but is this amount of drift considered to be too much ? The scale is + 20 arc sec, so I estimate about 1 arc second per minute drift in both RA and Dec.

Note that I have a portable setup and use only the RAPAS to polar align. If this amount of drift is too high, then I probably need to check my RAPAS to make sure it is still aligned.

Mike


 

>>> is this amount of drift considered to be too much ? The scale is + 20 arc sec, so I estimate about 1 arc second per minute drift in both RA and Dec.

if you image for 10 minute subs, that would be 10 arcsec drift, or 10 pixels if you had an example image scale of 1"/pix

so your stars would smear by 10 pixels. I would say that's far too much

Doing unguided with just visual polar alignment would be really tough. Using APPM and a sky model would help considerably for tracking improvements that compensated for polar misalignment

Brian

On Fri, May 7, 2021 at 9:02 AM M Hambrick <mhambrick563@...> wrote:
I ran an unguided tracking graph on my 1100GTO (non-AE) mount for about 12 minutes last night to see how much drift I am getting. I am assuming that the drift in each axis is due to the polar alignment being off, but is this amount of drift considered to be too much ? The scale is + 20 arc sec, so I estimate about 1 arc second per minute drift in both RA and Dec.

Note that I have a portable setup and use only the RAPAS to polar align. If this amount of drift is too high, then I probably need to check my RAPAS to make sure it is still aligned.

Mike



--
Brian 



Brian Valente


Roland Christen
 

It depends on where you are measuring the drift. Is it at the meridian, at celestial equator or at the zenith?

Roland

-----Original Message-----
From: M Hambrick <mhambrick563@...>
To: main@ap-gto.groups.io
Sent: Fri, May 7, 2021 11:02 am
Subject: [ap-gto] Tracking Graph Diagnosos

I ran an unguided tracking graph on my 1100GTO (non-AE) mount for about 12 minutes last night to see how much drift I am getting. I am assuming that the drift in each axis is due to the polar alignment being off, but is this amount of drift considered to be too much ? The scale is + 20 arc sec, so I estimate about 1 arc second per minute drift in both RA and Dec.

Note that I have a portable setup and use only the RAPAS to polar align. If this amount of drift is too high, then I probably need to check my RAPAS to make sure it is still aligned.

Mike


--
Roland Christen
Astro-Physics


Roland Christen
 

You could easily have that much drift if you were 3 hours away from the zenith, looking either east or West, just due to normal atmospheric refraction. At the zenith i would be looking for drift of around 1 arc sec per 5 minutes. However, having 1 arc sec per minute is not a deal breaker if you do guided imaging. Guiding can easily handle that.

Rolando

-----Original Message-----
From: Brian Valente <bvalente@...>
To: main@ap-gto.groups.io
Sent: Fri, May 7, 2021 11:08 am
Subject: Re: [ap-gto] Tracking Graph Diagnosos

>>> is this amount of drift considered to be too much ? The scale is + 20 arc sec, so I estimate about 1 arc second per minute drift in both RA and Dec.

if you image for 10 minute subs, that would be 10 arcsec drift, or 10 pixels if you had an example image scale of 1"/pix

so your stars would smear by 10 pixels. I would say that's far too much

Doing unguided with just visual polar alignment would be really tough. Using APPM and a sky model would help considerably for tracking improvements that compensated for polar misalignment

Brian

On Fri, May 7, 2021 at 9:02 AM M Hambrick <mhambrick563@...> wrote:
I ran an unguided tracking graph on my 1100GTO (non-AE) mount for about 12 minutes last night to see how much drift I am getting. I am assuming that the drift in each axis is due to the polar alignment being off, but is this amount of drift considered to be too much ? The scale is + 20 arc sec, so I estimate about 1 arc second per minute drift in both RA and Dec.

Note that I have a portable setup and use only the RAPAS to polar align. If this amount of drift is too high, then I probably need to check my RAPAS to make sure it is still aligned.

Mike



--
Brian 



Brian Valente

--
Roland Christen
Astro-Physics


 

>>>  Guiding can easily handle that.

absolutely. I didn't mean to suggest it was a problem in general, only if you are doing unguided. it also depends on your image scale in addition to what Roland asked about re: where in the sky was this measured

On Fri, May 7, 2021 at 9:24 AM Roland Christen via groups.io <chris1011=aol.com@groups.io> wrote:
You could easily have that much drift if you were 3 hours away from the zenith, looking either east or West, just due to normal atmospheric refraction. At the zenith i would be looking for drift of around 1 arc sec per 5 minutes. However, having 1 arc sec per minute is not a deal breaker if you do guided imaging. Guiding can easily handle that.

Rolando

-----Original Message-----
From: Brian Valente <bvalente@...>
To: main@ap-gto.groups.io
Sent: Fri, May 7, 2021 11:08 am
Subject: Re: [ap-gto] Tracking Graph Diagnosos

>>> is this amount of drift considered to be too much ? The scale is + 20 arc sec, so I estimate about 1 arc second per minute drift in both RA and Dec.

if you image for 10 minute subs, that would be 10 arcsec drift, or 10 pixels if you had an example image scale of 1"/pix

so your stars would smear by 10 pixels. I would say that's far too much

Doing unguided with just visual polar alignment would be really tough. Using APPM and a sky model would help considerably for tracking improvements that compensated for polar misalignment

Brian

On Fri, May 7, 2021 at 9:02 AM M Hambrick <mhambrick563@...> wrote:
I ran an unguided tracking graph on my 1100GTO (non-AE) mount for about 12 minutes last night to see how much drift I am getting. I am assuming that the drift in each axis is due to the polar alignment being off, but is this amount of drift considered to be too much ? The scale is + 20 arc sec, so I estimate about 1 arc second per minute drift in both RA and Dec.

Note that I have a portable setup and use only the RAPAS to polar align. If this amount of drift is too high, then I probably need to check my RAPAS to make sure it is still aligned.

Mike



--
Brian 



Brian Valente

--
Roland Christen
Astro-Physics



--
Brian 



Brian Valente


M Hambrick
 

I was imaging NGC 4565 which was almost directly overhead when I made this graph. I am at 30 Deg latitude, so it was also pretty close to the Zenith.

Is a 1 arc sec per minute drift high enough that I should check out my RAPAS ?

I am always guiding when I take my images. In this case 10 minute subs. With guiding turned on, the guide star will typically stay within + 1 arc second.  

Mike


Roland Christen
 

If you can do a drift alignment and get drift in both axes down to 1 arc sec per 5 minutes, then you can calibrate the Rapas to that polar alignment. You should then be able to achieve similar drift each time you go out.

Roland

-----Original Message-----
From: M Hambrick <mhambrick563@...>
To: main@ap-gto.groups.io
Sent: Fri, May 7, 2021 11:42 am
Subject: Re: [ap-gto] Tracking Graph Diagnosos

I was imaging NGC 4565 which was almost directly overhead when I made this graph. I am at 30 Deg latitude, so it was also pretty close to the Zenith.

Is a 1 arc sec per minute drift high enough that I should check out my RAPAS ?

I am always guiding when I take my images. In this case 10 minute subs. With guiding turned on, the guide star will typically stay within + 1 arc second.  

Mike

--
Roland Christen
Astro-Physics