VI. Focal Settings
IX. Photo Development
First of all, understand that I am not an expert in this field. As a matter of fact, I have only have extensive work with tripod mounted photography of the stars. Someday, I hope to move up to the big leagues and purchase a telescope with a drive. Currently I own a Celestron C4.5, and it's a great scope, but it does not have the necessary drive to make it a useful astrophotography tool. I have been able to accomplish some limited shots of bright objects like the Moon through my scope using a technique called "prime focus photography". I'll get into that in just a second though. In the meantime, I have gotten some really good starfield/Milky Way shots with just a regular tripod, 35mm Minolta and some really good film. The following is a primer for this kind of photography. Be ready though- you are NOT going to catch the kind of pictures that make posters. There won't be any nifty pictures of the rings of Saturn or the Horsehead Nebula. What you will catch is the sight you beheld when you took the picture and if the object is bright enough you'll have a memory for a lifetime. <Top>
It seems like the magnitude limit for photographing objects in the sky with a tripod and camera is somewhere around 4 or 5. Beyond this, you can't keep star trails from occurring before you can collect enough light information. However, this limit can still provide for some great shots. I have found that the following has worked quite well. <Top>
This one is pretty simple. In fact, the simpler the better. It does little good to be out in the field, trying to get just right foreground, dodging airplanes in the sky (if you are in a populated area), for you to be fooling around with this knob or that button. Granted, there will always need to be some adjustment to this or that, but by the time you are in the field your goal is not to have to deal with that stuff. When I go out and lock my lens on and load my film, I am ready to take pictures. The camera you should look for is preferably all manual, that is no power focusing, film winding, shutter speed setting or anything else that might use up valuable battery power. Of course, I am not speaking from experience. The camera that I have used does use a battery for holding the shutter open, but nothing else. The worst thing you can have happen is to have the shutter open for an exposure and then have it give up with the sound of a telltale <click> as the exposure comes to an abrupt end! <Top>
For objects like comets, starclouds and bright planets, Fuji SG 800 or Kodak RG 1000 both fit the bill. I don't have a preference between the two. They are both good films. It seems that the RG 1000 gives a little truer to color presentation of the background, while Fuji seems a little more yellow. These films are also good for dramatic star trails with a brightly lit foreground.
For Moon shots and long exposure star trails, you might try either Fuji Super HG 100/200 or Kodak RG 100/200. I have used the Fuji 100 for the Moon shots below (images forthcoming) and had great success. For shorter star trails, you also can use a 400 ASA film.
There are a number of other films on the market. I know that hypered films are making strong gains among the astrophotography community, as are slide films. I don't leave those out on purpose, I just have not used them. They have a good reputation, and their results are well documented in any Sky & Telescope or Astronomy. For this kind of use, however, they may be like bringing a machine gun to a squirrel hunt- it is just WAY too much firepower. Try using the off-the-shelf film listed above. <Top>
This is amazingly important. The aperture of your camera determines how much light is allowed to reach the film and what focal length you'll be taking pictures at. Go too big and you'll over-expose your pictures. Too small and you'll wonder what you were photographing, since you won't be able to see a thing! For most dark sky use, you'll select the greatest aperture possible. For example, I use a f/2.2 setting on my 45mm lens and f/3.5 on my 125mm lens. Those are the largest settings possible, but would not be appropriate for bright, daylight pictures. <Top>
Unless you are capturing focused pictures of the foreground in your picture, you can use the "infinity" setting on the lens. It looks like a sideways 8 on the dial. <Top>
I. Star Trails
II. Star Fields/Comets/Bright Constellations
III. Prime Focus Photography
IV. "Eyepiece Projection"
Star Trails <click here for examples>
The techniques are many for this kind of astrophotography. One of the most dramatic (and dizzying when you view the results) is the method behind star trails. The most successful way to accomplish great shots is to pick a good foreground. It is this that will make your picture memorable and publishable. In star trail photography, you actually let the Earth's rotation do all of the work. You pick a point in the sky (Polaris is a good place to start) and using a shutter release cable to hold your shutter open, you simply let the film collect light for a specified amount of time. For example, you may decide to open the shutter and time the length for 5 minutes, or an hour. When accomplishing long star trails you should use a low ASA such as 200 or 400. Don't use 1000 ASA film for an hour exposure, or it will be way overexposed. This technique is also used for capturing meteor showers.
Star Fields/Comets/Bright Constellations
For starfield and comet shots, as well as bright constellations, you'll use the same technique. That is, you'll use the 800/1000 ASA films, but the exposures will be much shorter. For Comet Hale-Bopp, I found that a 30-45 second exposure was ideal. Starfields, like the Milky Way, also do well at this exposure length. Any longer, and you'll run the risk of the objects in your picture trailing off. I recommend a one minute maximum for fixed tripod shots. Any longer and you will notice significant trailing, especially in any blowups of the pictures you make. <click here for my Comet Hale-Bopp pictures>
Prime Focus Photography
Another technique is called "prime focus photography". I must confess that I have not used this method yet. The idea here is to make the telescope into a giant telephoto lens. This requires additional equipment (an adapter to connect the camera to the focuser is necessary- consult a knowledgeable store in your area) but the results, from what I understand, are amazing. The term "prime focus" is derived because the image is being projected directly onto the film at the point of focus. For dim objects, you would most certainly need a clock drive to correct for Earth's rotation during the long exposures. Many thanks to Bruce Jensen for his clarification of this technique. <Top>
This term is especially descriptive given the nature of this technique. It is amazingly simple to attempt, but a lot of practice is needed. Essentially, what you do is place the camera up to the eyepiece of your telescope, and inside the viewer of the camera you line up the image of what you are photographing. Basically, you are taking a picture of the image in the eyepiece. I haven't read anything on the limits of this technique, but in my short experience it seems that you would have to have a very bright target so that the light information records quickly. Pictures of Comet Hale-Bopp would not come out very well with this technique (although I am going to try it). However, the Moon comes out great, as the picture below shows. The shutter speeds for this kind of photography should be very quick, as with any bright or moving object. 1/250th and 1/500th shutter speeds were both good starting places. One of the biggest challenges of this kind of photography is the fact that after one or two shots, complete re-alignment of the equipment is necessary to keep up with your moving target. <Top>
"Eyepiece Projection" Photography
Now we come to one of the most important items of all of this information, and that is "bracketing". This is especially important to the beginner. Bracketing is the term for taking many of the same shots, but while doing so you alter the settings on your camera. The hope is that if you take 5 pictures, at least 1 or 2 will be great. The settings that you'll adjust include the aperture (but only for bright objects), exposure length and even film. Granted the last one, film, will be done much less often. When you are first starting, it is a good idea to also chart each shot, so that you can compare them with the hope that you won't have to bracket as much. For example, when I started taking Hale-Bopp photos I made notes of each shot's exposure length and description. Then, I knew enough about each picture that when I got my pictures back I was able to accurately tell which pictures were the best, and after that I only had to adjust my exposures a couple of times per set. That way, after I take a couple of what should be good shots in a certain reference frame, I can move on to find another foreground image, or angle, etc. If you would like to see the log that I use to keep track of my photo information <click here>. <Top>
And last, but by no means least, is the development of your photos. You can spend all night and hours on end trying to get the best shots, but if you take it to a shop that is unknowledgeable about astrophotos, or uses sub-standard equipment, you could lose every bit of that effort. I have only been bitten by this problem once and that was when I took my pictures to a local club store (like Sam's or PRICE CLUB), trying to get a break on the development. Their One-Hour service was very competent, but when I submitted some shots for the 3-day service (they send those out somewhere offsite to be processed) they came back scratched, to the point that every one was damaged. A scratch on a negative translates to a very bright white line in the picture. So, the moral of the story here is don't skimp- if you are not developing your own shots, make sure that the place you are taking them can do astrophotos. ASK, they will tell you.
To assist your developer, here are a couple of tips: First of all, in astrophotos, it can be difficult to determine when one photo ends and the next begins. In order to provide a starting place for the developer, I have picked up the habit of shooting the first couple of shots in the daylight, that way they get an idea of where the first exposures are beginning and ending. Second, let your developer know ahead of time that your shots are astro in nature. Astrophotos usually require extra attention and hand processing. The final recommendation is that you ask that the negatives do NOT be cut. It can be a hassle to get a long tape of negatives, but it is worth it. If they incorrectly cut the negatives, you can forget about reprints. Also, tape the negatives into a roll. Don't use paper clips, or even rubberbands, as they can scratch the negatives as well.
If you live in the Northern San Diego County area, I highly recommend Lou and the rest of the staff at Magic Color in Oceanside, California. Their number is 760.967.6014. <Top>
I hope that this little primer has been helpful. As I learn and perfect new techniques that I read or hear about, I'll post my results. What's important to realize is that this information will only take you so far. The buzzword for the day here is PRACTICE. Over and over again... Eventually you'll have pictures you'll be proud of, and most of all, you'll have something to remember that perfect night of observing. <Top>
P.S. If you would like more information on astrophotography, you should read the short lesson that renowned astrophotographer Jason Ware has on his page. The URL for that website is http://www.galaxyphoto.com.
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