[Matty P (Matt)]

Originally Posted by gregbradley

Nice shot. Can I ask why you chose ISO400? It seems a bit slow.

I always used the maxium ISO like 1600 or 3200. 400 is taking too long, its like stopping down a F2.0 lens to F5.4.

I have hear dsome say ISO800 gives better depth. Perhaps that is true and but if oyu have darks and flats and bias to subtract then I say go the max and hit it at ISO1600 or 3200.

Just be careful with DSLRs as they often show the stars as all white whereas there should be a variation in colour. I think that is because the star overexpose first so you can go too long. I have heard expose to 1/3rd of a histogram meaning that the hstogram is 1/3rd the screen or expose to the limit of your light pollution as that will hit a ceiling before the object will.

So at a dark site you go longer and higher ISO especially in summer and at a light polluted area you go shorter and more of them and use a light pollution filter.

That's where the 40D comes into its own with the 14 bit converter, stars are more likely to have colour.

Greg.

Hi Greg,

I was hoping to go very deep with the expsoures so I dropped the ISO down. I found that a 5 minute expsoure at ISO 800 looked overexposured.

Originally Posted by Ric

Very nice Matty, that cloud was a bugger last night for sure, it cut things short for me as well.

your guiding on this image looks very good. The stars are nice and round and the nebulosity is showing up quite nicely as well.

A fine effort

Thanks Ric,

It was disappointing having to pack up in the middle of an imaging session but I was just happy that I was able to capture 35 minutes worth of data before the clouds rolled in.

I thought I was going to have problems with guiding with a long focal length but I am very happy with the results.