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		Contents: Equipment Needed Planning Shots Setting Up Shooting the Photos Film Processing Analyzing Your Results		This is intended to be a "quick start" intro to wide field astrophotography. Specifically, this is a guide to getting started taking your first photographic shots using a 35mm camera on a tracking mount. Rather than be generic and offer a lot of possibly confusing choices, my intention here is to focus on specifics based on the equipment and procedures I use. Use the embedded links or sidebar links to explore other equipment options. For a more general introduction to the subject, check out the references listed at the end of this writeup, and talk to other astrophotographers to get more equipment recommendations.

EQUIPMENT NEEDED Tracking Mount / Tripod Ball Head Adapter Camera

Cable Release Countdown timer with alarm Film

Kenko Skymemo Manual Kenko Skymemo Polar Finder Instructions Byers Cam Trak Unofficial Manual

Tracking Mount To take long-exposure astrophotographs, a polar-aligned star tracking mount is required. The tracking mount I use for wide field astrophotography is the Kenko Skymemo R. This is a tracking mount specifically designed to carry one or more cameras. with accurate enough tracking to go for the manufacturer recommended limit of 30 minutes with a 50mm lens. I have opted to get just the basic tracker body and use it with my Bogen 3036 heavy duty photo tripod. The Skymemo mount comes with built-in sophisticated polar alignment scope which allows quick and accurate alignment using Polaris. Any similar tracking mount can be used. Alternatively, the camera can be mounted on a telescope you might already own in "piggyback" configuration, but the mount must be capable of being polar aligned. For the common SCT scopes out there, that means you must use a wedge. An alt-az mounted scope/camera will not allow for long exposure photos to be taken even if the scope can track the stars.   Ball Head Adapter An option which will make pointing the camera at the target a bit easier is a ball-head adapter. Be sure to use one that can handle the weight of your camera without gradually slipping.

Camera Although there are numerous suitable camera options the 35mm camera body I recommend is a Nikon family manual body such as the Nikon F. I recommend the Nikon family because there are numerous body and lens options available on the used market. See the references at the end of this document for alternatives. The Nikon camera reference listed is particularly useful as it serves well to replace the often missing manuals for older Nikon camera bodies. The requirements for the camera body are that it have a "B" (bulb) setting to hold the shutter open, and a cable release connection. Best are older generation cameras which are entirely mechanically operated (i.e. no batteries required for operation). A working light meter is not necessary. Generally the body will come with a fixed focal length 50mm lens which is the perfect starting point for astrophotos. If your camera came with a zoom lens, that is less desirable (more lens elements inside), but still usable. Start with a setting of 50mm, taping the zoom ring in position if necessary to avoid the possibility of the lens shifting on you during the evening.

Cable Release The cable release needs to be a locking cable release that can hold the camera shutter open indefinitely when the camera is in the "B" (bulb) setting. Generally these take the form of a 12" to 18" cable with a trigger plunger and a locking collar. The collar can be twisted into a position such that the plunger stays down (shutter open) when pressed, and releases when the collar is pressed. Choose a heavy duty one if possible. Putting excessive pressure on a light-duty one can cause it to come apart. Having a spare on hand is also a good idea as cable releases are notorious for failing at inconvenient moments! Note that the Nikon F camera body requires an adapter for use with standard cable releases.

Countdown Timer Another small item to remember is a countdown timer with an audible alarm. High accuracy is not required so even a mechanical kitchen timer would probably do.

		Film Films seem to change at the whim of the manufacturers, but as of this writing (4/2003), my preferred film is Kodak Ektachrome 200 (E200) which is also sold in as Elite Chrome 200. I recommend using slide film because no printing is necessary to see your results -- what you shoot is what you get back. Using negative film causes problems because the prints are made by a machine which assumes you are shooting "normal" daylight scenes, or by humans who don't know what an astrophoto ought to look like. To start, skip the problems and use slide film. I recommend E200 specifically because it yields a pleasing color balance on long exposures, with some emphasis of red components which are common in the sky.

		PLANNING SHOTS To make the best use of your time out in the field, plan your shots ahead of time. By using an appropriately scaled star chart and overlays representing the field of view of your camera lens, you can frame your shots and plan the order that works best as the earth turns under the sky. Plan for more shots in various parts of the sky than you will be able to actually shoot. This will give you some options if a part of the sky turns out to be cloudy. My preferred star charts for planning widefield shots is the Bright Star Atlas by Wil Tirion. But note that the distortions in these charts make it necessary to have different overlays for portrait and landscape compositions. To make it easier on yourself, settle on compositions that do not completely fill your frame. Remember that you will be shooting wide expanses of the sky. Most of the small objects you see in a telescope will be too small to discern on a 35mm photo with a 50mm lens. Even the moon is small on a 50mm shot. So go for broad expanses of the Milky Way, or bright constellations such as Orion or Scorpius.

		SETTING UP Setup for a widefield astrophotography setup is relatively simple, compared to a full telescope. Place Tripod Align Mount Setup Camera The tripod should be placed on a firm surface which won't be subject to vibrations from people or vehicles passing by. In soft dirt, you may need to provide foot pads for the tripod legs. Be sure these pads are positioned so that they don't get stepped on and shift the mount. Generally for small tracking mounts, alignment is done with a polar scope or other pointing device. In this case, exactly leveling the tripod/mount doesn't matter, but take care that the load is as balanced as possible, no matter where the camera is pointing. Instructions for using the polar scope vary depending on the tracker and should be provided with the tracker (e.g. see the Kenko Skymemo Polar Finder Instructions). If you're using a mount aligned only by using an elevation scale set to your latitude, then the tripod must be leveled. Camera setup consists of loading your film and setting the camera up for long exposures. Double-check these points to avoid common mistakes: Is the film advancing when you cock the camera? Is the shutter on the "B" (bulb) setting? Is the focus set for infinity? If your camera lens focuser has a tendency to slip on its own, consider temporarily taping the focus ring in place.

		SHOOTING THE PHOTOS Now it's finally time to take those photos, so position the camera to your first target and frame it the way you planned. As long as you haven't made it hard on yourself by trying to completely fill the frame, you should be able to get away with just roughly pointing the camera without looking through the viewfinder at all. This is important because generally it's very difficult to see anything at all. Make things easiest on yourself so you can simply set your focus for infinity and point your camera roughly. For a "middle"starting point, using E200, expose for 20 minutes at a setting of f/4. This is a recommended starting point for shooting relatively high in the sky for a location like the OCA's Anza site. For darker sites located far from urban areas, you should be able to shoot exposures twice as long. Plan for a sequence of photos at f/4 - 10,20,30 minutes. Then change to f/2.8 and do the same sequence while staying on the same subject. If your lens can open wider, by all means, try those settings too. And if you have another lens that fits your camera body, run it through the exposure bracketing sequences listed above too. You have lots of frames and for future shots, this test sequence will be valuable as your personal reference. For the rest of the shots, use the recommended 20 minutes at f/4 and shoot the rest of the targets you planned on. Some extra tips: Keep a log of your shots - duration, aperture setting, film type, target description, etc. Recheck polar alignment before starting each new shot. Double-check focus is at infinity, aperture setting, and exposure is at "B" before each shot. To minimize the possibility of moving the camera When starting an exposure, place a piece of dark cardboard or your hat in front of the lens, but not touching the camera or mount, then trip the shutter. Wait a second or two after touching the setup to uncover the lens. Cover the lens with your hat or cardboard and then close the shutter. If a plane is about to ruin your shot by flying through the camera's field of view, place the cardboard or hat in front of the camera lens (but not touching it) until the plane has passed by.

		FILM PROCESSING Once you've taken your shots for the night, plan to have your film processed the next day or as soon as practical. Film and processing is relatively inexpensive, and it's important to get feedback from your first roll. For processing, I recommend taking the film to a film lab that caters to serious amateurs or professionals, not a mall 1-hour processing lab. For all common slide films, the developing process is "E6" ("C41" for negative films). For E200, I normally also request a "+2 push" on the processing which effectively makes the film faster. This also makes the film slightly grainier and costs a few dollars more for processing, so you may wish to end up standardizing on a +1 push or standard processing once you find your own preferences. Also request that the film be processed and returned to you uncut (i.e. not mounted in slide holders). This will insure that the lab does not accidentally decide to cut the frames in the middle of the frames! Check the frames with a magnifier - 8x or so to see the whole frame and 20x or so to check frames critically and to do some cruising through the pieces of sky you've captured! Store your film in letter-size film holder pages available from the photo supply stores. Not only do they serve as a good way to organize your results, but they insure that the film is pressed flat over time. The worst thing to do is to keepy your film rolled up and stuffed back into the film can! If you also have access to a film scanner, there are a whole range of digital enhancement possibilities, too numerous to go into here. If you have a decent scanner, it may also serve as a good alternative to using a high-power magnifier to analyze your images. However, note that scanners typically have a hard time scanning dense frames (underexposed frames or night scenes). You may find that slides which look pleasingly exposed for magnifier viewing are too underexposed for the scanner.

		ANALYZING YOUR FIRST RESULTS Your first roll of images can tell you a number of things to help you to speed your way on towards success with subsequent rolls. Note which exposure settings work best for your observing location. Note which objects are picked up easily with the film used. Check the star images in the corners of the frames carefully. If they are distorted, you may have to stop down your lens and compensate by lengthening the exposure. Check the overall brightness of the sky background on your frames. If there is vignetting (darker in the corners than the center of the frame), you may need to stop the lens down and correspondingly lengthen the exposure. Check for trailing of the stars. If you see some trailing you may have to improve your polar alignment, tighten your camera mounting to prevent sagging, or just shorten your exposures.

FOR FURTHER READING Astrophotography for the Amateur Michael Covington, Cambridge University Press, 1999 Wide-Field Astrophotography Robert Reeves, Willmann-Bell, 2000 The Backyard Astronomer's Guide Terence Dickinson and Alan Dyer, Firefly Books, 2002 Nikon Classic Cameras, Vol. 1 Paul Comon, Silver Pixel Press, 1996

D. Kodama © 2003-2008