Better ($) to go to a 20, 28, or 35mm lens instead

Disclaimer: I teach astronomy and physics, although I've barely dabbled in astrophotography. Having said that...

Keep in mind that astrophotography doesn't always call for a wide lens. Depending on what you're looking for, you might want a telephoto lens over a wide zoom. Or you might not even need an ultra-wide. A wide kit lens might serve you fine.

You're also looking at a dark sky with stars that are moving slowly over time. The longer you leave open the shutter, the more you'll start to notice star trails. This is great if you want star trails, but less so if you're trying to photograph a nebula, where a moving subject will just blur over time.

The best solution, of course, it to attach your camera to a telescope with a tracking mount that slowly moves with the stars, to avoid star trails.

You might also benefit significantly from having a FAST lens,since astrophotographs can take a long time to capture. A 5 minute exposure becomes a 10 minute exposure w/ a 1-stop difference. A 5 minute exposure at F1.4 would take around 40 minutes at f4. That's a 3 stop difference, and the fastest that some of those ultra-wide zooms can shoot at.

So, unless you're trying to capture star trails, you might want to use a fast lens, preferably one that is fairly sharp when it's wide open. Again, I've never tried this, but I have to imagine that a fast 50 1.4 or 35 1.4 might work pretty well if you're OK with capturing a smaller section of the night sky.

If you still want an ultra-wide zoom, you might strongly consider the Tokina 11-16mm, which can shoot at f2.8. It'll still collect light a lot more slowly than a f1.4, but a lot faster than at f4. It's not quite as wide as some of the other lenses, but it's still pretty wide and highly regarded on Dyxum. And you can still capture star trails with it.

The wide angle primes also tend to be faster than the zooms. Look through the dyxum database. There's a sigma 20 1.8, a Rokinon 24 1.4, and several others I see, plus a number of wider f2.8 lenses.

Or, better yet, start with your kit lens. Take some pictures. See what you like, and what kind of pictures you can capture. If your kit lens isn't wide enough, then you need to go ultra wide.
Or maybe you'll be convinced to drop $13,000 on the "new" Sony 500mm f4 (it's actually a re-make of an older, equally expensive Minolta lens, I believe)

There are also some good (and some terrible) mirror lenses, which act a lot like modern telescopes. You can find some mirror lenses starting at around $100. They're probably not great, but might be OK for what you need if you decide to go telephoto instead of ultra-wide. You don't need to worry about circular bokeh because everything will be in focus at infinity. I'm not sure if poor contrast would affect your star images too much. They're fairly light, also, but fairly slow. Usually a constant aperture of F6.3-f8. (Although the mirrors are fairly big, they capture a much smaller section of the sky, so collect light more slowly).

This is probably more than you asked for. I hope it helps. I'd love to do more astrophotography, but it's too much effort, and often too cold, for me to go find dark place from which to photograph.

Best,
Ian

Oh wow, that looks fun,

http://www.youtube.com/watch?v=ErkaM9IvZ7U

I'd love to be able to do this. I have a Sony A55, intervolometer, UPS, and I live in UTAH where most of these were filmed. Anyone want to suggest any budget lenses?


Edited by stiuskr - 23 February 2012 at 12:02