OAG / PHD2 problem

[rubecula]

First attempt last night at guiding.  I was using the EdgeHD with an OVL OAG and Altair Astro mono GPCAM. I was able to focus a Canon 7D through the OAG assembly (Blue fireball SCT to T Male / M48-T2 expanding ring / OAG / 14mm spacer / Canon T Mount - which amazingly comes to the required 105mm).  The GPCAM was mounted in the OAG turret with a focusing eyepiece holder.

I had a USB cable from the GPCAM to the laptop and a USB / Serial cable from the laptop to the hand controller.  PHD2 mount was set to "Celestron - ASCOM".

I was completely unable to focus the GPCAM.  I tried with the turret fully in the holder and moving it out to various positions.  I also moved the GPCAM from fully engaged in its holder to as far out as I could without it falling out of the holder.

The best image I got in PHD2 was a grainy grey with a paler grey arch running through it.  The as I moved the GPCAM out the pale grey arch dissapperared and the grainy grey became almost white.  I tried various exposure times from 2 to 20 seconds.

Has anyone got experience of the GPCAM or other suggestions as to what I am doing wrong.

[rubecula]

I've made a bit of progress, I managed to point the GPCAM through a Canon camera lens and produced an image on the laptop.  Phew....so I know the GPCAM is functioning.  

It looks as though my problem is just a focusing issue and a matter of playing with the distance from the OAG prism to the GPCam and possibly the point where the prism intercepts the light path from telescope to imaging camera.

[michael8554]

Hi Robin

Try focusing the Edge onto the GPCAM in it's OAG position instead - daytime on a distant object, if you can reduce the GPCAM gain enough for daytime images.

Roughly measure from the centre of the OAG mirror to the GPCAM sensor, and that is the distance the 7D needs to be behind the OAG mirror.

Then hopefully replace your 14mm spacer with a value that gets the 7D in focus.

Or play with the GPCAM spacing if removing the 14mm spacer completely doesn't shorten the 7D light path enough.

Michael

[D4N]

Easiest way is in the day, focus on something with the imaging camera and note the focuser position, focus again with the guide cam and note the difference. Adjust the spacing by the difference and try again. I normally use a rooftop to do this.

Once you get it so both cameras can focus at the same time you are ready to try at night.

It is possible to do it at night but you will need to use something bright (the moon would be good).

/Dan

Sent from my iPad using Tapatalk

[rubecula]

Thanks Michael & Dan.  I'll try that, but not now, it's absolutely bucketing it down at present --- AGAIN!!

[si_]

Hi Robin - did you get this sorted? I'm using a c9.25 with OAG and GPCAM mono and have found that the gain and exposure have to be very high - gain 90% and exposure 2s+ generally. The grey out is PHD2 stretching what it is seeing (nothing) and this will change to black when you get on a star. Try using a cluster to find your focus - I used Pleiades for mine. I could focus the imaging camera on a star and find another in the OAG easily to work with the GPCAM. Hope this helps.

By the way, what driver are you using with PHD2? I'm having no luck with the Altair drivers at all and there does seem to be a problem with lots of beta files flying around.

cheers

[rubecula]

Hi Si, yes I did get this sorted.  I was too coarse in trying to focus the GPCAM.  It took me ages just moving the focus a tiny bit at a time, but I finally got there.  I'm using PHDs v 2.6 and the Celestron ASCOM drivers.  I've also loaded the Altair drivers as well.  I've not taken any images yet.  I've spent the last couple of clear nights using PHD2 to polar align the mount.  The alignment is much better than it was, I'm hoping that if it's clear on Tuesday night I might be able to get it bang on.