PA with a vengence.

[Guest peepshow]

I have been doing photo drift alignment.  Taking a 15 minute exposure due east without tracking, then after 7 minutes switching the tracking on at double speed.  Double speed gives a reverse track on the image back to where the  exposure started.

If East/West PA  is out the image shows as a image looking like a pair of thin tweezers.  The short arm being the non tracking trail and the other arm the longer return tracking trail. 

 

The join of the tweezers, as it were, is where the non track finished and the double speed track began.  Only when the tweezer arms are both together, (after PA axis adjustments), is the east drift alignment OK.  Repeated for South then.

 

The longer the exposure times the more easily it is to see errors.   SO, using a wider angle lens...........

 

......to avoid overexposure I am now going to take a 40 minute exposure, but cover up the lens after 30 seconds.........., No tracking.

 

Then start tracking at double speed again after 20 minutes and uncover the lens for 30 secs,

 

Just before the 40 minutes is up I uncover the lens for the last 30 sec exposure.   The resultant  Image will show 3 short star trials, the first and last will be superimposed on each other if PA is spot on.

 

My system is for a fixed mount and not for a PA nightly strip down lark.

 

Honestly, it's much easier to do than to explain it.

 

 

Edited July 22, 2014 by peepshow

[Guest Tweedledum]

Ohh myyyy,, thank god I am visual only

[+Bino-viewer]

......and me !