From: "Tim" <tjp314@pacbell.net>

Date: January 12, 2007 10:01:13 AM MST

To: Astro_IIDC@yahoogroups.com

Subject: Re: connections for long exposures with Pt Greys

--- In Astro_IIDC@yahoogroups.com, Milton Aupperle <milton@...> wrote:

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.

I'll try that when I can!  Great suggestion.

OT:  I STILL haven't seen that comet yet!

You won't believe this, but it's clear as a bell right now, and blue

as can be all the way down to the horizon - even over the skyscrapers

downtown, which are only 7 miles from my tower window.

But the "hilarious" part is that the Clear Sky Clock for Griffith

Observatory (4 miles in a straight line from my house) shows cloud

cover between 3 and 5, and no transparency between 4 and 6!!!

Clear as a bell before and after that!  

If it really goes down like that this evening, I just might jump OUT

the tower window!!  :oD

-Tim.