Posts Made By: Bill Bynum

Newbie to webcam astrophotography, looking for focusing advice on the following optical train (listed in order):

Celestron 9.25 SCT
JMI 2" SCT focuser with Motor (and 1.25" adapter)
Televue 2.5x Powermate
1" Tele-extender
Phillips ToUcam Pro II 840 Webcam

If I remove the Powermate, the cam comes to focus with no problems.

With the PM in, nothing - the power meter (K3CCDTOOLS) shows 0, no fuzzy blobs, nada on the screen.

If my thinking is right, adding the PM should increase the size of the image as well as making it much dimmer, but leaving the overall "power" nearly the same. I still should be getting something through the camera though.

So, what gives? Does adding a Powermate radically change the focal point? Or is there something else I need to know?

We had a similar view for the Venus transit also. Darn it.

I'm pretty new at this stuff, but here is what came out of last Sunday's early morning shoot.

ToUCam Pro 840/C9.25 @ F/25/GM8.
Seeing 3/5.
04:00 CST more or less
Aligned and stacked with Registax 2.
About 250 images out of 1800 (80% quality)
Saturation greatly increased and fairly aggressive wavelet processing.

Is anybody aware of a commercial builder doing 10" or larger airline-transportable dobs yet?

I am currently using a C9.25 on a Losmandy GM8 (non-Gemini goto drive) for planetary webcam imaging.

My GM8 has a G-11 Saddle Plate, a polar scope and the standard tripod. The tripod is more stable at minimum height, but it makes using the polar scope a real, literal, pain in the neck. The current focuser is a JMI NGF-S so focus bounce is not a problem.

I have done some half-decent images with this setup, though nothing to compare to your stuff. Here's about the best I've done:
http://www.mnastro.org/forums/album_page.php?pic_id=123

All that being said, I feel that this setup is undermounted and hopefully will be upgrading to a G-11 Gemini soon.

That first article makes a pretty strong argument, and I see the second article mentions uncertainties, but does not quantify them.

Can anyone point me to articles quantifying the uncertainites in the current GCMs?