OAG camera alignment query

[RayD]

I'm just venturing in to the world of off axis guiding on one of my imaging OTA's, and have a query about the OAG camera alignment.  When I use my piggy backed guider on another OTA I align the camera to the horizontal axis (as close as I can), but for no specific reason other than it's easy to do and I assumed the correct thing to do.  With the OAG do I need to align the camera perpendicular to the OTA, or does the alignment really make no difference as it is the direction of the star movement that is monitored, not it's position on the sensor?

Your thoughts and help as always would be welcomed.

[michael8554]

Hi Ray

If you're lucky enough to always find a guide star then orientation isn't a problem, at least with PHD.

So maybe orientate for least cable strain?

Michael

[RayD]

3 hours ago, michael8554 said:

Hi Ray

If you're lucky enough to always find a guide star then orientation isn't a problem, at least with PHD.

So maybe orientate for least cable strain?

Michael

Thanks Michael that's great.  

[sloz1664]

As Michael as stated. Orientation is not an issue unless you cannot find a suitable guide star, which has never happened to me. Also orientate it into a position which eliminates any pier or mount clashes.

Steve 

[ollypenrice]

I would orientate the prism to approach one of the long sides of the chip so that it can go further in without shadowing the image. After that you can surely orientate the guide chip along RA and Dec, if you want to, simply by turning it in its holder (when seen from above.)

Olly

[steppenwolf]

As Olly says, aim to align the prism with the long side of the main imaging sensor - it is amazing how the light cone is interrupted by its intrusion especially on a large sensor. Actual alignment with RA is not at all critical as the guide software can compensate for any angle but I tend to align mine with the long edge of the guide camera sensor with the RA axis but if you need to rotate the the guide camera to locate a suitable guide star, this really isn't a problem.

[RayD]

Thanks all for your help, much appreciated.