Gearing up for astrophotography

All the positive feedback Ive received for my recent attempts at lunar photography have made me more enthusiastic than ever about getting into astrophotography. Ive already got a few books on the subject; truth be told, theres a bit of a learning curve. Its going to take me a while to get good at this. And thats not a bad thing, because astrophotography can be awfully expensive: its going to take me a while to assemble all the equipment required for a basic astrophotography rig that can do more than just photograph the Moon. Ive already got two main pieces of equipment. I have a telescope geared towards astrophotographers: an 80mm Sky-Watcher Equinox apochromatic refractor, with really good colour correction (as far as I can tell) and a short (500mm, f/6.25) focal length. I also have a digital SLR sufficient to the task: a Nikon D90. (Most astrophotographers use Canon, whose noise reduction algorithms are better for stars, but a Nikon is hardly unacceptable.) In addition, I have a number of accessories for the D90 that will help: an external battery pack (to aid with multiple long exposures in the cold), a corded remote (to reduce camera shake when pressing the shutter), and a right-angle finder (to aid in focusing and allow me to see through the camera when its attached to a refractor or catadioptric telescope). I also have T-ring adapters to connect my camera to a telescope: one for a two-inch focuser (like my refractor), and one for Schmidt-Cassegrain telescopes. So, what else do I need? The first piece of equipment Im likely to get is a Televue Powermate. You may have heard of a Barlow lens, which increases the magnification of an eyepiece; Powermates add another doublet lens to this design to correct diverging light rays. Increasing the magnification of my refractor would really help my lunar photography. A 500mm refractor doesnt magnify the Moon very much: it presents a very small image on my cameras sensor. Doubling the focal length with a 2× Powermate would put the Moon on more pixels, making for a better image. (Alternatively, I could use my 125mm Schmidt-Cassegrain instead  it has a focal length of 1,250 mm  but its not as sharp and contrasty as an apochromatic refractor.) What clinches it for me is that Powermates have T-ring adapters (sold separately), which simplifies things: I can just stick the camera and T-ring into the Powermate, rather than sticking the camera and T-ring into a separate T-ring adapter that then slides into the Powermate. Total cost: A 2× Powermate for two-inch focusers lists for around $350-400 at Canadian stores; the T-ring adapter runs around US$50. If I want to take pictures of anything other than the Moon or the planets, Ill need an equatorial mount that will track the sky. The mount Ive settled on is the HEQ5 Pro from Sky-Watcher, which Orion sells as the Sirius EQ-G. It costs around $1,200 and has a capacity of around 30 pounds (13-14 kg): more than enough for my three-kilogram refractor. But Im thinking ahead a bit: this mount would also be able to handle Newtonian, Schmidt-Cassegrain and Ritchey-Chrétien telescopes with an aperture of eight inches (200mm) or less, or Maksutovs of six inches (150mm) or less  more than enough for a good long while. Its also light enough  about 20 kilograms  to be reasonably portable, which is a factor when you dont plan on setting up a permanent observatory any time soon. The HEQ5 Pro has a go-to computer and an autoguider port (more on which anon), as well as periodic (but not permanent) error correction (a way to train the computer to compensate for regular tracking errors in the gears; permanent PEC would have been better). An autoguider corrects tracking errors brought on by imperfections in polar alignment and gears: it connects a small digital camera to the mount and a computer: when the camera catches a guide star moving in a way it shouldnt, the computer pulses the mounts motors to correct it. This is essential in long-exposure photography. How essential it will be for me is another question: an f/6.25 refractor is pretty wide-field (and presumably more forgiving of tracking errors), and a D90s sensor will overheat if it runs for too long  and heat is a definite no-no for astrophotography (it adds noise). But if it turns out that five-minute exposures (for example) require autoguiding, then I think Ive figured out which one to get. The one generating the most buzz is Orions inexpensive $280 (U.S.) autoguider, which plugs into a computer for power and control and into the mounts autoguider port. It also requires a separate guide scope (or, presumably, an off-axis guider, which is less preferred nowadays), which would be problematic with my refractor, which has a built-in dovetail rather than using rings. On the other hand, KW Telescope in Kitchener, Ontario, has assembled an autoguider package that uses a 50mm finder scope and connects via the main telescopes finder bracket  which my refractor has. Costs $350. I was worried that 50 mm would not be enough aperture to provide the camera with a guide star to lock onto, but Alan Dyers review in the March-April 2009 issue of SkyNews assuaged those fears. (Youre on the hook now, Alan.) This will not only save me from having to buy a guidescope-and-rings combination (Orion sells packages from $325 to $380), it will also take a few pounds off the mounts, er, shoulders. Finally, if Im getting an autoguider, Im going to have to have a laptop computer to operate it  unless I opt for Orions new standalone autoguider, which doesnt require a computer but which does require a power source, to say nothing of $600 (U.S.)! And, I hate to admit it, but that computer is going to have to run Windows (gakk!): all the autoguiders under discussion here use PHD Guiding for software, and while PHD Guiding is Mac-compatible, the drivers required to connect to these autoguiders arent. (Mac-compatible cameras are more expensive; what are you gonna do?) Besides, Im not sure Id want to subject a precious MacBook to the elements. My criteria for an astronomy laptop are that it (a) be inexpensive (so as not to cause grief if I break it) and (b) have crazy-stupid battery life. I just so happen to have a candidate in mind that appears to fit these criteria: the Asus Eee PC 1000HE, a Windows netbook with a 10-inch screen, a 1.6-GHz Atom processor, a 160-gigabyte hard drive  and a battery life claimed to be as high as nine and a half hours. (See posts about this computer at Engadget and Gizmodo.) Staples has it in stock, and sells it for $450. By the time I actually get around to buying one, however, it will almost certainly be supplanted by a newer model, but its good to know that what Im looking for is more than theoretically possible. By this point, of course, I will have spent something like $2,600 including tax. This is a shopping list for the long term  in the next year or two, not the next month or two. Ill have to save my pennies and work a couple more lucrative government contracts first. Then, once this is all bought and paid for, Ill probably start thinking about a dedicated astronomical camera. But thats something best left for another post &