Jump to content

  •  

CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.

Photo

PHD2 Calibration Failure, RA star did not move enough

astrophotography equipment imaging
  • Please log in to reply
10 replies to this topic

#1 lrlinnell

lrlinnell

    Explorer 1

  • -----
  • topic starter
  • Posts: 72
  • Joined: 15 Jan 2017
  • Loc: Denver, CO, USA

Posted 22 October 2018 - 03:26 PM

I do not have a fixed observatory so I have to transport my gear to a dark location and sometimes my guide camera gets moved and I have to re-calibrate PHD2. Last night when I tried to calibrate, I kept getting the error "calibration failure RA star did not move enough". 

 

  • I was pointing at Altair so the declination was about 8 degrees (PHD2 wants the calibration done with 5-20 degrees declination)
  • the star in the cross hairs on the right side of the PHD2 screen (PHD2 auto selected the star) moves about 2/3 of the total available scale by about 55-60 steps
  • I played with the settings at the bottom of the screen for min step size, etc but still get the error.
  • as far as I can tell, nothing has changed in my setup - other than adding Polemaster a few weeks ago - the PHD2 stars are nice and tight with a good pointed light distribution
  • at about 60 steps West the error pops up even though the star looks like it is moving plenty far enough

 

Any ideas where I should start for troubleshooting this issue?



#2 rgsalinger

rgsalinger

    Cosmos

  • *****
  • Moderators
  • Posts: 9,476
  • Joined: 19 Feb 2007
  • Loc: Carlsbad Ca

Posted 22 October 2018 - 03:58 PM

Post the log. One possibility is that as your star moves a brighter star comes into view and PHD thinks that is the calibration star. I've seen this happen with other guiding software. That's where a log would probably be useful. I assume that you are getting the message ONLY at the end of the calibration run. 



#3 StarmanDan

StarmanDan

    Aurora

  • *****
  • Posts: 4,875
  • Joined: 27 Aug 2007
  • Loc: Where the stars at night are big and bright...

Posted 22 October 2018 - 03:59 PM

I had a similar issue.  After some investigating, I discovered that my mount had acquired some bad backlash.  After adjusting the worm, I was able to get calibrations in less than 30 steps.



#4 happylimpet

happylimpet

    Fly Me to the Moon

  • *****
  • Posts: 5,963
  • Joined: 29 Sep 2013
  • Loc: Southampton, UK

Posted 22 October 2018 - 04:25 PM

Provided you can put the camera back on within a few degrees rotation, I wouldnt bother recalibrating. I never do.


  • xiando likes this

#5 lrlinnell

lrlinnell

    Explorer 1

  • -----
  • topic starter
  • Posts: 72
  • Joined: 15 Jan 2017
  • Loc: Denver, CO, USA

Posted 22 October 2018 - 04:30 PM

I have attached a log file from last night. I'm not sure how to read it.

 

The calibration process starts with West steps and I get the error at about 60 steps West. The calibration program never gets past the West steps.

 

There are no other stars close to the guide star.



#6 KenS

KenS

    Apollo

  • *****
  • Posts: 1,091
  • Joined: 10 Jan 2015
  • Loc: Melbourne, Australia

Posted 22 October 2018 - 05:12 PM

Looks like the guide log failed to attach....

Note that PHD2 stops calibrating after about 50 steps if the star has not moved the specified number of pixels (default is 25 pixels).

So many things can cause that to happen so the guide log would be helpful.



#7 lrlinnell

lrlinnell

    Explorer 1

  • -----
  • topic starter
  • Posts: 72
  • Joined: 15 Jan 2017
  • Loc: Denver, CO, USA

Posted 22 October 2018 - 05:16 PM

I am resending



#8 lrlinnell

lrlinnell

    Explorer 1

  • -----
  • topic starter
  • Posts: 72
  • Joined: 15 Jan 2017
  • Loc: Denver, CO, USA

Posted 22 October 2018 - 05:31 PM

Attached is a PHD2 logfile from last night

Attached Files



#9 homerdt

homerdt

    Ranger 4

  • *****
  • Posts: 312
  • Joined: 07 Sep 2008
  • Loc: Astoria, Oregon

Posted 22 October 2018 - 05:39 PM

I had this same problem last week, after about 1 1/2 hrs I gave up, uninstalled and reinstalled. Tried it and has been working for several nights now. Just a glitch I guess...



#10 KenS

KenS

    Apollo

  • *****
  • Posts: 1,091
  • Joined: 10 Jan 2015
  • Loc: Melbourne, Australia

Posted 22 October 2018 - 06:32 PM

It looks like your calibration steps are too small. At 750ms they moved the mount 16 pixels west after 60 steps.

Try using the calculator to calculate the step size.

I suspect your focal length of 50mm entered into PHD2 is also incorrect. That sounds like the aperture of a finder guider. The typical focal length of these scopes is 162mm.

Also check the guide speed setting in EQMOD and set it to between 0.5x and 0.9x. Make sure the right value shows up in the calculator.

 

With values of 162mm focal length, 5.2um pixel size and 0.9x sidereal  I get a value of 1050 ms calibration step size. That should move the mount 25 pixels in 12 steps.

Capture.PNG

 


  • happylimpet likes this

#11 lrlinnell

lrlinnell

    Explorer 1

  • -----
  • topic starter
  • Posts: 72
  • Joined: 15 Jan 2017
  • Loc: Denver, CO, USA

Posted 22 October 2018 - 06:41 PM

awesome! thanks. I'll look into all of that. My guide scope/guide camera came as a set from Orion and it is 50mm guide scope. I will run the calculations you suggest and give that a try. Thanks so much for you insights.

 

Lloydsmile.gif




CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.


Recent Topics





Also tagged with one or more of these keywords: astrophotography, equipment, imaging



Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics