Originally posted by jawats Do you always use primes, or do you use zooms as well?
For the most part I have used primes exclusively. In general they are faster, sharper, and have less CA than zooms. Although doing astro you sometimes find out that a lens that is otherwise great is really awful for astro shots. This is more true with older 3rd party glass. My very first astro attempt was with a K2000 and 18-55 DA, no tracking and and I had no idea what I was doing. A couple weeks later the kid broke that lens so I never did more astro with it.
Originally posted by jawats I suppose speed isn't as important, as I will have an EQ tracking mount - not sure about whether it's what you mean - here's what I ordered: SkyGuider<sup>TM</sup> Pro Camera Mount Full Package
That is an equatorial which is great choice. It doesn't look like it has goto functionality, get everything aligned and then it can automatically point your camera at things for you instead of you finding them, but looks to be a good place to start from. An Alt-Az mount is a different type of tracking mount where it will do x and y movements of the camera but not rotation. They are typically easier to setup and align but because of the lack of rotation errors crop up. The built in astrotracer functionality in newer Pentax cameras (either with built in GPS or through the O-GPS1 addon) act like an Alt-Az mount but in camera and more limited time wise. I hope this helps clear things up some.
Originally posted by jawats So, if I want to try wider shots of, say, the milky way, or large portions of the sky, I would want to go to wider than 24mm?
Probably. For the milky way you probably want a HFOV greater than 90 degrees if not over 100 maybe evenapproaching the 180 some fisheyes can get to. That will allow you the ability to get huge expansive landscapes with the milky way arching overhead or in a portrait layout have a long milky way comming down from way up in the sky to the foreground. Here is
a thread over in the astro group showing a wide astro shot as well as a narrow one. The first one is 3 images from a Samyang 16 mm F2 stitched together (I would assume they were landscape images stitched into a portrait image). If doing shots of things like the milky way you can always do a composite where you shoot the sky tracked and then turn off tracking and shoot the foreground. This gets you the best of both worlds.
Enjoy your new gear and have fun with it.