Quote:
Originally Posted by pluto
Thanks Greg,
It was many, I took about 10 and they all look similar.
Actually I've just gone through them and it does look like there is some quite noticeable tracking errors on most of them but they all have roughly triangle shaped stars.
When I was doing 1 second focus exposures the stars looked perfectly round... maybe it is just bad guiding...?  |
There you go. If you had pinched optics you should be able to see this effect visually and it would appear on every image.
If its a guiding issue it looks like there must be a large periodic error spike at some point in the worm cycle.
Have you sat and watched a whole exposure's worth of 1 exposure with these stars? Was there a sudden spike in errors at one point?
A triangular shape like that is unusual in my experience with tracking. Normally if I get a bad spike it looks like double stars everywhere or a bad elongation in one direction but a triangle.
It does look a bit like coma as well. Are you using a corrector/reducer? Perhaps its at the wrong spacing. Usually Tak is either 87mm or 120 odd mm. There is a list of metal back distances for Tak scopes at Anacortes.
Greg.