Jump to content


Photo

Question about my declination graph...

  • Please log in to reply
9 replies to this topic

#1 broca

broca

    Surveyor 1

  • *****
  • Posts: 1586
  • Joined: 26 Mar 2010
  • Loc: Ocala, FL

Posted 19 January 2011 - 04:58 PM

I have a CG-5 that was recently HyperTuned. I'm trying to guide with a AT6RC
and an 80mm short tube guide scope. I used ASPA and did a drift alignment using
PHD software. Everything is balanced so the mount was East heavy in RA and scope
heavy in Dec. My Declination graph show the Declination line steadily climbs.
The RA looks good. Is this a result of polar alignment that is off? I'm hoping this is a basic problem that I am overlooking...Any
comments or suggestions is appreciated.
Steve

#2 ChadGray

ChadGray

    Ranger 4

  • -----
  • Posts: 399
  • Joined: 09 Apr 2010
  • Loc: North East Ohio

Posted 19 January 2011 - 05:30 PM

Does it ever come back?

Sounds like PHD cant throw enough correction at the mount to bring it back in.

Did you turn DEC guiding back on after PHD drift aligning?

#3 broca

broca

    Surveyor 1

  • *****
  • Posts: 1586
  • Joined: 26 Mar 2010
  • Loc: Ocala, FL

Posted 19 January 2011 - 05:43 PM

I turned the Dec guide back on. I have a feeling that even though I did the PHD assisted drift, I may not have done it correctly. I was doing this while dodging clouds. The graph just keeps climbing after 5 min I started my trouble shoot again. I'm sorry I do not have a pic of my graph, I'm using a different computer at the time. I'm back at again tonight... :bangbangbang:

#4 ChadGray

ChadGray

    Ranger 4

  • -----
  • Posts: 399
  • Joined: 09 Apr 2010
  • Loc: North East Ohio

Posted 19 January 2011 - 05:57 PM

5 minutes and it did not return? Even with really bad polar alignment my graph would return over a shorter period of time than that.

I would PHD polar align first. I dont know how ASPA works, but if it involves moving the physical azimuth or altitude knobs on the mount, skip it. Even it if does not i would try skipping it for your next experiment tonight.

Once you know your mound it physically polar aligned. Reboot the mount and do you normal 2/3 star alignment to find things in the sky.

It takes time and patience... hang in there!

#5 broca

broca

    Surveyor 1

  • *****
  • Posts: 1586
  • Joined: 26 Mar 2010
  • Loc: Ocala, FL

Posted 19 January 2011 - 08:42 PM

This web site RULES!! Thanks for your advise on using PHD to polar align and in searching out this thread , I now have a flat declination graph and good guiding with the AT6RC and CG-5!!
I set the autoguide rate on the hand control to RA 50 and DEC 99. I then redid the calibration and BAM!! No more climbing DEC graph. These full moon nights are good for something :D.
Steve

#6 ChadGray

ChadGray

    Ranger 4

  • -----
  • Posts: 399
  • Joined: 09 Apr 2010
  • Loc: North East Ohio

Posted 19 January 2011 - 09:55 PM

COOL! I have not tried playing with the autoguide rate. Of course i am not touching my mount unless it starts acting funny. I just checked and my autoguide rates are 50/50.

I am guiding via ASCOM drivers and using a USB to serial cable to plug into the hand controller.

I am just glad you found a flat line for DEC! Very Cool!

Can you describe the exact process you used?

#7 broca

broca

    Surveyor 1

  • *****
  • Posts: 1586
  • Joined: 26 Mar 2010
  • Loc: Ocala, FL

Posted 20 January 2011 - 06:46 AM

I did a rough polar alignment using a star near the meridian using the ASPA on the hand controller. I then calibrated the star with PHD and did the PHD assisted polar alignment as you've described. Once I was satisfied with the polar alignment I set the Autoguide rate on the Hand Controller to RA 50 and DEC 99. I then recalibrated the star with PHD. This is what gave me a nice line in the center of the graph in declination :jump:.

#8 ChadGray

ChadGray

    Ranger 4

  • -----
  • Posts: 399
  • Joined: 09 Apr 2010
  • Loc: North East Ohio

Posted 20 January 2011 - 11:12 AM

If i am reading this right the Autoguide Rate is a percentage of the full sidereal rate.
Celestron Web Site

The way i understand sidereal rate is if it is 1 (full sidereal) then the mount should track the stars perfect.

So if your DEC is a little off you can increase the aggressiveness of PHD's correction pulse by putting the Autoguiding Rate for DEC to a higher percentage of sidereal.

Is this correct? Am i understanding Sidereal and Autoguide Rate correctly?

Next question:
Will you need to tweak the Autoguiding Rate according to how well your mount is polar aligned? Or is this setting making up for the flaws in the mount gears/lube etc?

Hopefully it is the flaws in the scope and you never have to change it again.

Chad

#9 broca

broca

    Surveyor 1

  • *****
  • Posts: 1586
  • Joined: 26 Mar 2010
  • Loc: Ocala, FL

Posted 20 January 2011 - 02:29 PM

The way I understood this was changing the autoguide rates changes how fast the gears move when using autoguiding. So if my gears are moving slow in DEC then increasing the rate the gears move faster to keep the DEC where it should be. I'm sure someone out there is more versed in this than me and can give a better explanation. I learned this from this thread.
I'm a simple man and I'm just glad I got this working. Now time to figure out the why.
Steve

#10 ChadGray

ChadGray

    Ranger 4

  • -----
  • Posts: 399
  • Joined: 09 Apr 2010
  • Loc: North East Ohio

Posted 20 January 2011 - 02:39 PM

That is basically what i said. The default settings are 50% of sidereal speed. If you set it to 99% you get the full sidereal speed when PHD sends a correction pulse. So each correction pulse that PHD sends is more aggressive because the gears are turning faster for each.

Hopefully someone will confirm our understanding.






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics