Re: Help!! Part 2!


Stuart Heggie <stuart.j.heggie@...>
 

Tom, you're pier base sounds solid enough. 5' should be deep enough especially with that 3'x3' base. That said, as others have said, you should probably recheck your polar alignment to be sure. The FSQ on any camera has a big FOV so field rotation will show up easily.

Now, with that out of the way, based on your description of the stars, I'm betting your camera is not seated securely on the FSQ. Are you using threaded connections or a nosepiece / thumbscrew setup? If the latter, I'd bet the camera is loose and tilting and turning in the the 2" adapter. Even if the connections are threaded, if they're not tight, i.e. the camera can rotate, that would explain a lot of the symptoms.

Stuart

On Mon, Dec 5, 2016 at 12:04 AM, tom_b@... [ap-gto] <ap-gto@...> wrote:
 

In part 1 I did manage to get tracking working but when I looked at my images  they were pretty well useless so I gave up.

The first image which was just a 2 minute unguided shot to see if everything looked OK showed clear field rotation if you looked at the stars at the bottom of the photo.  They were long in shape and were clearly rotating about some point in the photo.  So they looked like small arcs.

The next images with autoguiding for 30 minutes were strange.  The star images at the bottom left were tilted towards the center of the photo and the stars images at the bottom right were tilted towards the center top of the photo as well.

Something like this:


       Center top

        Center

/           |           \


I would think that if my polar alignment was off, they would be little arcs, no?

Here is some background:

The scope is on a 10" diameter pier, attached to a 16"x16" 5' deep concrete pillar that has a base that is 3' x 3' down at 5 feet.

I did this myself, and probably didn't compact the earth around it enough but it's been 1 year since it's been in place.

I did a PemPro polar alignment about 6 weeks ago, and I got the alignment with everything locked down to about 1 minute of arc from the pole.  The last session I did a month ago, had 8 30 Minute subs that were as perfect as could be.  SInce that time, the scope was just parked and today I imaged the same object in the same part of the sky as last time.

So, what could cause the slanted stars?  Is my polar alignment off?  Does the polar alignment of a permanently installed scope change with time and temperature?  It has gotten much colder lately and it has been raining really hard for about a week, with some days seeing 20mm of rain.

Should I just scrape the whole setup and take up knitting?

ARGhhhhhh. 






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