DSLR Basics - what exposure, aperture, ISO etc

one thing I've never seen on the boards is a long exposure of the polar area showing rotation around polaris, this types of pictures are very striking.

Here's one from my holidays in July near Marbella in Spain. Exposure is 858 seconds, 90-300mm lens @ 110mm F5.0, I used ISO100 because of the long exposure time to get the trails. The only processing was a levels adjustment to darken the sky, as the long exposure meant it was very bright. Lots of Vignetting.
The interesting thing about this for me was to show how much the polestar moves over the 14+ minutes exposure.



Canon Digital Rebel XT, 90-300mm EF Lens @110mm.

That's a great shot John - it shows just how far off the pole Polaris really is!

Nice shots lads, with a black sky it makes for a really nice target.

Seanie,

A couple of tips for the 350D that I've picked up are:

1. One thing you can take advantage of with the 350D is the ability to run automatic dark subtractions after each 'long' exposure shot (anything longer than 30 secs). This is done by setting the Custom Function Setting #2 Long Exposure Noise Reduction. This will help reduce any later processing.

2. Also Set the Parameters to Set 2.

3. Get yourself a remote switch - This is really essential. I picked one up on E-bay for around €6. this will make all the difference to reduce camera shake.

4. If your really paranoid about camera shake you could also use the mirror lockup setting. The mirror goes up, but the shutter isn't opened until you depress the button a second time, this does away with the jolt from the mirror rising.

5. White Balance. I usually use Daylight setting, instead of the default Auto.

6. Don't be afraid to play around with different ISO settings depending on what your subject and conditions are, as you can see above I used ISO 100 on the pole shot because I new I was going to do a very long exposure, a higher ISO setting here would have way overexposed the shot. Lower ISO also has a finer grain - less noise - more detail. I always use ISO 100 on the moon. ISO 800 is usually best for DSOs.

Also, here are the slides of a talk I gave on the subject last year...

www.pevans.me.uk/html/don_t_be_afraid_of__m_.html

Thanks Paul, I'l have a look at that. Last night I tried some Andromeda shots witht he 28 to 80mm lens, 5 second exposures. They turned out fine with regards to trailing when seen on a small scale, but at 10 seconds, trailing was evident even on a small size image.

Seanie.

The fogging you saw is probabily just local high haze conditions,although look out for dew on the camera lens.
As you probabily know, a lower F stop will yield you brighter stars as will a higher ISO rating, BTW, what camera are you using?

Canon 350D. I was just trying s staright forward minimum F number (3.5) that the lens would allow. I'll be looking into the science of these things as I go along. I'm just a little impatient that I just apply trusted settings I have seen from you guys before, and want to see what results it could yield!