Re: [APML] ST-4 question

["Mike Connors" <micon@starband.net>]

Alan,

My frost symptoms are generally obvious:
Lower brightness than expected; star moves around a few
pixels; doesn't return within +/-1 pixel after calibration; and
most of all: jumps around during exposure, eventually gets lost.
Usually the jumps are rapid and violent like "seeing from Hell".
Perhaps you have other problems than frosting, but it won't hurt
to change out your dessicant ring.  Cheap insurance it is.

As to preventing frost, all I can think of is to make sure your
O-ring seal is in good shape and/or modify the ST-4 head with
ports to accept either filtered dry air or some other filtered gas.
Perhaps it is good practice to place the ST-4 head in a 
bag or other container with desiccant when bringing it indoors
after imaging on a cool/humid night. Me, I just change rings regularly :)

hope this helps,

Mike Connors


----- Original Message ----- 
From: "Alan Voetsch" <alanv12952@yahoo.com>
To: "Discussion of Film Astrophotography" <astro-photo@seds.org>
Sent: Sunday, September 05, 2004 10:30 PM
Subject: Re: [APML] ST-4 question


> Hey Mike,
> 
> --- Mike Connors <micon@starband.net> wrote:
> > I get these symptoms when there is frost on the chip.
> 
> When these symptoms started, I had just decided to run the guider and
> mount off the same battery. I just lost another guidestar (20 minutes
> ago). So, I wired up the mount to run off household current again, but
> I still had the same problem when calibrating. 
> 
> I will change the desiccant ring tomorrow, and bake the old one for a
> spare. Is there anything else I need to do to relieve the frosting
> problem?
> 
> Thanks Mike,
> Alan
> 
> 
> 
> 
> 
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