daneb star test for comments ( uk )

[little col]

12 x 30 secs iso800 st80/300d prime focus :)
first time i have imaged anything in raw and i am quite suprised at the extra data i have caught , seems to the left of daneb there are some squiggly lines , dont know what these are:shrug:

[mill]

It is full of those lines.
I also dont know what they are and how the stars become elongated in the edges :(
Very weird.

[Ric]

Hi Col, I have limited knowledge in these things but I think they may be hot pixels. The trick is to use dark frames to eliminate them.

It is still a great looking image though.

Cheers

[Terry B]

The lines are hot pixels. You have added the images together after aligning on the star and the hot pixels dont stack one on top of each other resulting in the little streaks. You need to use a dark frame to remove them from each raw image before stacking to get rid of them.

[Dr Nick]

Looks like hot pixels to me ;)

[little col]

thanks for your verification of the hot pixel issue , does this mean i have to take exactly the same amount of dark frames as i take light frames ?

[Terry B]

Yes and no.
You need to take dark frames of the same exposure time as your light exposures. It is usual to take a number of dark exposures and average them is some way. I usually take 6 frames and median combine them. I then use the same dark frame on all of my sub frames. If this is all double dutch take a look at http://www.astrosurf.com/buil/iris/tutorial2/doc91_us.htm
for a tute on image processing. There are many other tutorials also available.
Good luck