Where did I go wrong?

[Failtedwk]

Hi everyone.

New to this and joined today after looking at some fabulous photography posted.

Wondererd if anyone could comment on this pic?

Had the fortune to be in the Ritz Carlton near Tucson in December and tried to take a few night shots with a Nikon D80 with my 10mm fish eye.

I didn't have my remote so my hand was on the shutter for just over 4 minutes and explains the shake but if I (especially on the 3MB original)I zoom in, the picture is full of coloured dots. Maybe its a basic photography question but any help much appreciated.

Now going to look at the forum to see what kind of telecscope I should buy!

With kind regards

David

[andrewluck]

Welcome to low light photography, and the world of hot pixels .

In a word, noise. The trick here is to take an equal length exposure (same ISO setting as well) with the lens cap on and subtract it from your image. You should find that it'll clean up considerably.

Cheers

Andrew

[zakkhogan]

Hot pixels is the correct answer, its small defects on the camera's sensor,

you can read up on it here:

http://en.wikipedia.org/wiki/Defective_pixel

But as andrewluck says, its smothing that can be dealt with

[andrewluck]

Hi David

I hope you don't mind if we keep this on the forum. Other people might find the discussion useful.

The first part is easy. Your original picture was 4 minutes, so, with a light-proof lens cap on, take an equal length exposure. This will have pretty much the same pattern of coloured spots on it that you have on your image.

Now you have a picture of your subject with the hot pixels superimposed and an image of just the hot pixels. So, if you subtract the second from the first you should be left with just the subject. For this you need some software that's capable of pixel math. If you have a copy of Photoshop that'll do the job; as will Maxim DL or PixInsight. All three will cost you money if you don't already haveone of them. A free alternative is Deep Sky Stacker, but I have no experience of this program. I'm sure someone else will be able to jump in and help.

Cheers

Andrew

[Failtedwk]

Thank you both so much for all your advice.

I need to go play and importantly now I know about hot pixels and how to improve my images.

Many thanks & kind regards

David