From: Milton Aupperle <milton@outcastsoft.com>

Date: January 12, 2007 9:23:53 AM MST

To: Astro_IIDC@yahoogroups.com

Subject: Re: [Astro_IIDC] Re: connections for long exposures with Pt Greys

Hi Tim;

On 11-Jan-07, at 10:24 PM, Tim wrote:

One odd thing i discovered with guiding was that the Guide Scope does

not need to be a very long focal length at all. Over X-mas I was

shooting with the C8 at 1000 mm focal length and using 80 mm

aperture / 400 mm focal length scope for guiding. The stars were

nice and round and tracking worked really well, right up until the RA

gear started sticking and making a "ca chunk" sound. I was using

either a 0.1 or a 0.3 pixel tracking accuracy with a Mag 6 star and

133 ms exposures with the Flea 2 in 4x4 binned mode.

I was going.. HUH?... until I got to the 4x4 binning part. I was

using the flea, not the 2 for guiding, but I think my stars were all

fainter than that. And unbinned and .513ms on the Megrez 80.

My binning method uses something I created called "forward binning", so it doesn't reduce the image size and your guiding at actual image size.

My Guide scope is on rings, so I can move it +/- 3 degrees to find a good enough star to guide with.

I can't try again until these bloody clouds go away (and probably that

comet, too!), but I hope that's my problem. It seemed to wander back

and forth in RA, worse than if I didn't guide at all, and after a few

minutes it'd go wild in dec until I shut it off. Sometimes I got good

round stars for 2 minutes, because a video of M42 with 2minute frames

has about 4 good frames that I was able to coadd in Photoshop.

That may be because of what your backlash compensation settings are. I had a similar problem for Dec with the HEQ5 mount. Once I dropped the backlash to <0.5 arc seconds (which is 10 units in the hand controller electronics) it tracked great, but until I figured that out, I had the exact same problem. For RA it was less an issue, but I also adjusted that down too.

HTH..

Milton J. Aupperle

President

ASC - Aupperle Services and Contracting

Mac Software (Drivers, Components and Application) Specialist

#1005 - 815 14th Avenue. S.W.

Calgary Alberta Canada T2R0N5

1-(403)-229-9456

milton@outcastsoft.com