Q. Halley's Comet is coming and I want to make some pictures of it. I don't have a telescope and I'm not sure when it will be visible. Can you supply any information?
A. Yes. Let me share the results of a conversation with Robert Burnham, senior editor of Astronomy magazine.
First of all, if you've never photographed the night sky, you're in for a treat. The results can be dramatic and make you want to do more.
As far as Halley's Comet is concerned, the most effective pictures will be of the comet streaking across star trails. The time to start preparing is now. You have to make some star trail pictures in order to know how to record the comet's travels.
A "trail" picture is a time exposure of moving stars. The streaks they make on the film show their paths and direction. The patterns are great, and will be even better when intersected by the comet.
You really can't effectively use a disk or Instamatic camera to photograph the comet. Further, you shouldn't try to use one of the super automatics or a point-and-shoot camera.
You need to use a camera that has a time exposure mode or at least a bulb setting ("T" or "B"). If there's any doubt, read your owner's manual very carefully or check with the store that sold your camera to you.
You're going to need a tripod. In fact you'll need a good, steady tripod. Since you'll be dealing with long exposures, vibration in your tripod will hurt. If necessary, add a sandbag (or even a sock filled with gravel or rocks) to the center of the tripod, just below the camera. This will give added mass and steadiness.
The comet will be visible in the evening sky during December and January. It will also be visible in the morning sky during March and April. I'm pointing toward the spring for the best photography, but now is the time to get started with some test shooting.
Since the viewing dates are during cold weather, certain precautions have to be taken. In some of the programmable cameras, the shutter works off a battery. Be sure that your batteries are super fresh and will hold the shutter open for at least two minutes.
Then, there's the problem of moisture. Frequently you will find that dew will coat your lens. The best answer is to be near electricity and use a hair dryer to gently blow warm air over the lens. If you can't be near an outlet, there are devices that work from the cigarette lighter of your car.
What you want to do is set up as far from the city lights as possible. Try to keep the eastern horizon as low and as dark as possible. If you can gain some altitude, such as a hill, so much the better.
After you've made your tripod as stable as you can, lock your camera to it. Use a normal or slightly wide- angle (35 mm) lens. You need a fast lens and fast film. An f3.5 lens would probably work, but you'll be better off with something f2.8 or faster. Be sure that you focus at infinity and open the lens to its maximum. Try to avoid zooms, since they are generally not as fast.
Use a fast film. Don't worry too much about grain. The Kodak VR- 1000, the 3M 1000, or the Fuji 1600 should work very well. If you want slides, use the fastest ASA film you can, probably ASA 400.
Next, be sure to remove any filter from the lens. No skylight filters, no ultraviolet filters, no filters of any kind. The filters will create a reflection situation that will cause a double image in your picture.
Set the shutter on "Time" and you're ready to go.
Hold a piece of cardboard in front of the lens, open the shutter, then, when everything has stopped vibrating, remove the cardboard and start your exposure.
Start with an exposure of about 11/2 minutes. Then increase your exposure in increments of 10 seconds till you have made a three-minute test. Just be sure to take your time and write down exactly what you do on each frame.
Next, try changing lenses. Do the same things with a 100, 105 or even a 135 mm lens. The star trails will be considerably different. If your longer focal length lens is slow (f.4 or higher), start your exposure tests at two minutes and go up to at least four minutes.
Your resulting star trail pictures will give you an idea of what you can look forward to.
Before you begin your night testing, shoot the first one or two frames in good, natural daylight. This will give automatic cutting machinery something to lock on to so that your frames won't get cut in half.
As for processing: The best thing is to handle this with the same care as you do all your other film. Many stores are geared for special instructions. If so, tell them what you are shooting. Explain that these are pictures of the night sky so they can pass the information on to the processing lab. If you use the one-hour processing facilities, explain the same thing yourself. Otherwise, their automatic exposure machines may get a wrong reading from the back sky and the results will be ugly purples and blues.
When the processing is over, take a long had look at each one, match it to your carefully taken notes and go from there. The first roll will give you a good start.
The clearer fall nights are almost here, so get ready to point your camera up.