[APML] ST-4 question-UPDATE WITH NO RESOLUTION

[Alan Voetsch <alanv12952@yahoo.com>]

Hey all,

In an effort to end this thread before next year I thought I'd post an
update after replacing the desiccant ring. There was no improvement.
I've giver it 3 nights to see if there was any change and there isn't.
My symptoms were, and are; 

1. Guider not returning the star to the same position when calibration
was finished. It always has before.

2. Lower than normal brightness readings. I am having to use longer
exposures and higher 'boost' settings than before. I'd estimate that
the readings are about 50% lower than what they used to be. Over the
years I have gotten pretty good at guessing what parameters to use to
get a star to a certain brightness.

3. Completely losing the guidestar a couple times. Never did that
before.

4. Before starting one exposure, it was reading about '15' for
brightness. When ended, the brightness had gone up to about'40'. That
was about 2 hours later and the temperature had dropped about 10
degrees.

5. Upon power up, where the brightness reading used to drop to '10'
after a minute, it now only gets to '12'.

6. Guiding has remained OK, although I have not had any film developed
this week. A check of guidestar location before and after a 3 hour
exposure last night showed that the star was in the same location.
Focus had shifted due to falling temps, but still guidestar brightness
increased almost 50% during the exposure. This indicates to me that
improper cooling is possibly responsible for the problems during the
early evening hours.

It's possible that number #1 is mount-related as Chris Schur suggested.
My focus is still optimal.  As a precaution, I ran a piece of yarn
through and around the cooling fins as I had noticed some dust
build-up. No change. I suspect either a chip that is getting too old,
or a problem in the cooling system. I have few mechanical or electronic
skills, so I'm only guessing. I can't see how a faulty relay could be
responsible for the all of the above symptoms so I do not suspect that.
I don't know what else might cause the problems I'm seeing. 

I'm going to send an enquiry to SBIG, maybe they still do repairs, or
have some advice I can use.

Thnaks for all the suggestions,
Alan




		
__________________________________
Do you Yahoo!?
Yahoo! Mail - 50x more storage than other providers!
http://promotions.yahoo.com/new_mail
_______________________________________________
Astro-Photo mailing list
Astro-Photo@seds.org
http://seds.org/mailman/listinfo/astro-photo