15th Jan. 2012 ::
Another Attempt at Andromeda (M31)
Beautiful night, it was clear, still, cold and moonless. Somewhat typically however I struggled with alignment, so I only managed maximum 105 second exposures. Even then there was a little star trailing, so I definitely didn't make the most of the great conditions. Shame. Alignment really does seem to be the limiting factor at the moment - I need to find a setup routine that works for me. Still, given that I'm fairly happy with this result.
About 1hr 25mn of exposure data. Plus a limited amount of darks, flats and bias.
Image Field of View
vonevilstein
Another amazing pic fella. Whats' the deal with alignment?
#1 – 17 January, 2012 at 9:53 am
James
Well, such a good question! I could write a book on the trials and tribulations of accurate alignment. I know a lot more about that than I do about actually taking the images themselves.
The basic issue is that accuracy is key, and there are a lot of steps involved, so a mistake or a moment of laziness in any one step will destroy the alignment.
Problems are:
1) Setting up in the cold and dark.
2) Heavy cumbersome equipment.
3) Locating Polaris through the Polarscope - it's easy enough by eye, not so much in the polarscope as there are some stars of similar brightness close by, and it's easy to lose orientation and exactly which star is Polaris.
4) Locating alignment stars (This is easier with a red dot finder instead of a finder scope because - as with the polarscope - it's easy to lose orientation; however, my red dot finder only fits one of my scopes, so I need to make an adapter for the other scope).
5) Alignment stars obscured by trees, or other obstructions. (Sometimes - as with this image of Andromeda - I end up using alignment stars all on one side of the Meridian, I'm not sure exactly what affect this has, but I'd guess that using both sides - hence a wider variation in alignment star location - may be beneficial.)
6) Centering alignment stars (I have started a process of using progressively more powerful eyepieces for this to increase accuracy. I have tried using an illuminated reticle eyepiece but that introduces it's own problems).
7) Readjustments to the polar alignment then require repetition of previous steps.
8) Mistakes, wrong buttons or accidently moving the telescope can result in resetting, returning the entire setup to the "home" position, turning the mount on and off, and starting the whole process again.
And finally, what I find to be the big overall issue:
9) Understanding, and keeping a mental picture in your head of how adjustments in Altitude and Azimuth will affect the progress of the telescope that is moving through various degrees and combinations of Right Ascension and Declination.
It's just one of those things that takes practice and patience. After every session I end up with a plan of what to do differently next time. One day I'll reach a plan that works consistently well. When I discover that process I'll write all about it, so hopefully others can learn from my traumas... :)
#2 – 17 January, 2012 at 12:39 pm