|
Peter
Well, the whole drift alignment / polar alignment question was going to be another thread. I thought I had it pretty well worked out with my trusty EQ5. But now... I am not so sure.
I have been doing the long exposure drift test. Normally, I set the tripod and balance. Then aim at a convenient star, using Fomalhaut at the moment. Then I set the EOS to bulb, drift for 1 minute to the west (RA numbers decreasing), then come back to the east for 50 seconds. I compare the resulting lines and done.
Then what I like to do, once alignment is complete and tracking underway, is centre on a star and take a shot. I then leave everything sit for a period of time (typically 30 minutes or 1 hour depending on what I am going to do) then take another shot. I overlay the two exposures and see how much drift there has been during the period. With my EQ5 I could get pretty close. Well, close enough for me anyway.
Rather than use a lot of words, have a look at the attached. It is three shots combine in RGB. All three shots were taken using Fomalhaut.
The Blue line is my two minute drift exposure. Lines up okay.
The Green star represents the first shot in the series. The Red star is the second shot taken 30minutes later.
There is a bit of Dec drift, but I can fix that. If I am reading all this right, the "bad" drift is in RA. This is what has me perplexed.
The weather looks like it is going to be good here tonight, so I am going to have another play with it and see how I go.
Any comments, suggestions would be appreciated.
Thanks
Darrell
|