PHD Q-Guider Dec Calibration failing - Help

[netwolf]

Hi All,

I have posted a enquiry on the stark labs group and have some feedback from Craig Starks on the issue. But I wanted some information from the local users here.

On Saturday night Kal (Andrew) and I setup at Apoman's (Peter) place to test out guiding on his setup, as we had some issues at the SPSP. We are noting that DEC Calibration keeps failing for us. Our AE errors at one time were reported as A13 and E15 and on a second cold start (post battery fail) the were A~30 E~56 (not sure why the discrepency possibly because we did not use a reticle eyepiece to align stars).
Though these A E errors may seem high we are pretty sure our barlowed drift was almost nill. PHD is set to default values and we were using 1 and 2 sec exposures for the guide camera. Even though DEC cal fails the RA guiding continues and DEC guiding is disabled.

Craig advises this is normal for objects near the pole as we were trying to image Centauras A, Omega Centauri and ETA Carina.

Further to this the second and perhaps the main problem is that PHD seems to lose the guide star and flashes red. The coincidence here is that it seems to occur while were making a 60 sec exposure toward the end of the exposure. PHD will beep and flash red to indicate star is out of the green alignment box. When we did 30sec exposures guiding seem to be ok, but we were still getting star trails. On review of our exposures Peter advised that a unguidied 30sec exposure showed no stair trails.

We will be gathering again around the next new moon to continue our fine tuning of the process. Also Kal and I will test the Guider on our own setups (but we do not have Gemini only the Digital Drive). Next time i think i will take some more accurate notes of what transpired.

Any help or suggestions would be appreciated.

Regards
Fahim

[Dennis]

Hi Fahim

Sorry to hear of your problems – I know how frustrating these can be!

I use PHD, an (old model) Orion Star Shooter Deep Sky CCD and a WO 66mm F6 for side-by-side auto guiding with the GPUSB interface.

When PHD goes through the calibration routine, in indicates that it is clearing DEC backlash before making the DEC cal movements. I have done this for Eta Carina, Omega Centauri and other objects near the SCP and PHD has always completed the cal successfully and auto guided successfully for fl’s up to 1000mm with my rig.

Cheers

Dennis

[netwolf]

Dennis,

Hmm the DEC backlash cleared ok on our setup but then when it did N and S calibration it fails after the timer hits 60-61steps for each N and S. This is because our DEC default setting is Auto to check both N and S and calibrate the direction it detects movement in.

The setup we used was:
The imaging setup was a AstroPhsics 130 F6 with DSLR 350D camera.
The Guide setup was a Borg 77ED F6.5 with Q-Guider (QHY5) guide camera.
Mount G-11 with Gemini.
Laptop using PHD and Nebulosity. Using Serial port to controll shutter
on camera, and USB for Q-guider and DSLR Camera image download.

So our Guiding FL was 500mm and the Imaging FL was 780mm. I am guessing perhaps this is not ideal now looking at these figures. I am guessing that the guiding FL should be longer or do we need to reduce the claibration step size to match our FL.

Regards
Fahim

[Geoff45]

I had this problem trying to do the Leo Triplet and only on the leo Triplet. However I tweaked the position of the guide star slightly and then it seemed to work.:shrug:. Re losing the GS, did you try setting the noise reduction to a 3 x 3 box. It seems to help.

[pvelez]

I had a similar problem. I suspect it is the timing of your guide pulses during calibration - I pushed mine right out to about 750ms and it now works a treat.

I found that because my polar alignment was ordinary, I was getting a lot of dec drift and the fact that PHD was guiding in RA only meant that I was quickly in the red zone. Increasing the guide pulse sorted all this out.

Hope that helps

Pete

[pvelez]

Here is the link that outlines my efforts

http://www.iceinspace.com.au/forum/showthread.php?t=28897&highlight=phd+pete

Hope this helps

Pete

[netwolf]

Thanks Pete I am glad we are not alone and thanks for your help. I will review your thread closely. Our calibration setting was at 1000 i believe which was the default.

Regards
Fahim