Camera iso settings

Hi' which is the best iso settings on the camera while piggyback on a telescope.When i use primefocus the camera is set at 800 iso Thanks.Mark

I too have been wondering about this. I am by no means an expert, but I think it depends on what you are taking shots of and whether you have a tracking mount or not.

If you haven't got a tracking mount then, depending on the focal length of the lens you are using, you will have to use relatively short exposures to prevent trails showing. If you are taking shots of faint objects then you will have to use high ISO numbers to gather as much available light as possible.

If, for example, you are taking shots of the moon, then a single exposure with a fairly high shutter speed and low ISO may well give you a correct exposure. Some other, fainter, body like Jupiter, may require several short exposures at high ISO and then stacking of the images. Star fields, galaxies, nebulae etc may require several hundred images at high ISO.

On all digital cameras, high ISO number means more noise in the image. Some cameras are better than others, but this is unavoidable.

The use of dark frames in your stacking software can nullify the effect of this.

If you HAVE got a tracking mount, then you can increase the exposure times and use a lower ISO number. However, longer exposure lengths also mean more noise in the image. Again dark frames can help.

I am just starting out in astrophotography but, when I finally get a tracking mount, I am going to try to use the lowest ISO and longest exposure I can get away with since, I think, long exposure noise is more predictable (and therefore more likely to be nulled out by dark frames) than high ISO noise.

In my mind they are different types of noise, but I am sure that someone here knows far more than me about these things and I hope they can correct me if I'm wrong.

Hi Martyn' Thanks for your reply on the subject.I will do that next time i'll go out one night.Mark