Author Topic: PHD2 Guiding  (Read 216 times)

0 Members and 1 Guest are viewing this topic.

Apophis

  • O. A. S.
  • Star Class
  • *
  • Posts: 478
  • Skywatcher
PHD2 Guiding
« on: Jun 21, 2017, 11:30:23 »
Guiding a bit variable!
I wondered anyone who was using PHD2 , what their guiding rate iwas as mine is set at .50 but when you pulse guide with EQASCOM then its set at .10.
Roger
Look and ye shall find

NoelC

  • O. A. S.
  • Nebula Class
  • *
  • Posts: 40
Re: PHD2 Guiding
« Reply #1 on: Jun 21, 2017, 12:02:07 »
Roger
I'm using it; but not a good source of info as my guiding performance at present is shocking (RMS over 1.5")!
When you say Guide Rate; are you referring to the 'Ascom Pulse Guide Settings' RA Rate and Dec Rate in the EQMOD dialogue?
If so; the default is 0.5, but I have mine set quite high at 0.7 or 0.8 due to problems with the mount (backlash) and the general inability to track stars (leading to lost stars).

See http://openphdguiding.org/PHD2_BestPractices.pdf
and
http://openphdguiding.org/Analyzing_PHD2_Guide_Logs.pdf
for more info.
Synta mount, a bunch of telescopes and a shed (on wheels).

The Thing

  • Mr October
  • O. A. S.
  • Galaxy Class
  • *
  • Posts: 2381
  • The OAS International Branch
Re: PHD2 Guiding
« Reply #2 on: Jun 21, 2017, 16:27:12 »
Hi Guys,

If using EQMOD 0.5 is the recommended guide rate, PHD2 does not change it. Make sure EQMOD is not doing any backlash compensation while your checking that :). In PHD2 use the guiding assistant to give you a good set of settings and measure the DEC backlash and set the compensation in PHD2 which will then modify the value based on real guiding performance. If you re getting 1.5arcsec guiding using a stock un-tweaked SW EQ mount you are doing well. On my HEQ5 I manage 0.5" but that's had new bearings and a belt drive, as has my NEQ6. Bear in mind the seeing is rarely better than 2" and your guide scope may not have much resolution either (Dawes limit). Looking for 0.5" improvements in guiding accuracy can be a mugs game. Look for flexure in the guiding rig first as that's usually more likely a problem.

HTH

Duncan ... just back from lunch at the beach (again)
Life is like a box of chocolates, scoff it while it's in front of you.

Apophis

  • O. A. S.
  • Star Class
  • *
  • Posts: 478
  • Skywatcher
Re: PHD2 Guiding
« Reply #3 on: Jun 21, 2017, 22:07:58 »
Thanks guys some helpful stuff there.
Roger
Look and ye shall find

NoelC

  • O. A. S.
  • Nebula Class
  • *
  • Posts: 40
Re: PHD2 Guiding
« Reply #4 on: Jun 22, 2017, 09:12:14 »
Thanks for the tips Duncan.
I'm guiding at 1.5"RMS (that's about 3" p-p), which at f8 is 6 or 7 pixels on my setup.  I'm using an HEQ5 Pro under ASCOM (EQMOD).  I rebuilt the mount last year to check for any disasters; none found.  But made the mistake of swapping the less good bits onto the Dec side; on the basis that a smoother RA would give better results.  The consequence has been large un-adjustable backlash on the Dec side mostly due to one of the spur gears.  Even with PHD compensating for it (with corrections in excess of 0.5S) it is struggling to calibrate the mount, more than half the cals' are non-orthogonal (and unusable).

I ordered a belt drive kit from Rowan Astro yesterday....
Synta mount, a bunch of telescopes and a shed (on wheels).