From: Milton Aupperle <milton@outcastsoft.com>

Date: September 18, 2010 12:38:26 PM MDT

To: Astro_IIDC@yahoogroups.com

Subject: Re: [Astro_IIDC] hot pixels..

Mark;

On 18-Sep-10, at 11:48 AM, Mark Gaffney wrote:

Milton,

I worked out a possible cause of my guiding problems..

I doubt that this is the primary cause. Your mount has 2+ arc minutes of slop / binding on the RA axis and I have no ides how much on the Dec. That's why you get such weird calibrations and your GOTO doesn't work.

I`ve just opened the camera window inside the house here for the  

Scorpion, with the camera attached to the Kwiq guidescope but with the  

lens cap on..

The same faint artefacts that I thought were stars are there now, so  

I`m guessing these are in fact hot pixels?

Why "guess".  See page 73 of the Astro IIDC 4.05 manual. That is a real example of hot pixels.

Put the lens cap on (doesn't even need to be the scope attached), look at the image on screen. Are there "star"s there or not?

This is one of those cases where an image as a jpeg of what your seeing would be useful.

If I was guiding on hot pixels wouldn`t this cause these strange  

callibration problems..?

Possible, but your mount still has horrific slop. That's very evident because your GOTO doesn't work reliably and has nothing to do with "hot pixels".

Only if the hot pixels were really excessive and your guide star is very faint. Search for the phrase "Hot Pixel" in the Astro IIDC manual which describes how to use dark frames to eliminate this.

Milton J. Aupperle