Film Imaging

Well after playing around with the digital camera, and realizing the limitations of the one I owned, I wanted MORE. I did take the time to gather a few resources for research.

Two good (book) resources are “Astrophotography for the Amateur” by Micheal Covington, and “Splendors of the Universe” by Dickinson and Newton, both of which are available through Barnes & Noble.

After perusing these pages, I realized that I needed a fully manual camera, and regretted immediately selling my old Canon AT-1 at a garage sale. I did manage to pick up an Olympus OM-1 with a Zeiss f/1.4 lens at a small local camera store for only $75, which is probably half the going price for the camera body alone.

First Steps (Tripod): I had read enough to realize the complexity of this art form, so started out with the recommended star trail images with the camera mounted on a fixed tripod. Two words of wisdom (about all I can offer here): Experiment and Document

Document: This is truly a marriage of art and science. If you do not copiously document your efforts, you will be doomed to a lifetime of frustrations, combined with heaps of useless negatives. The film companies and your local camera shop will love you however.

Develop some type of simple log to record the following: Frame #, Date, time, object (as precisely as possible including general magnitude), location and conditions, Film type and speed, f/stop and exposure time. If you think this is too much of a hassle, try another form of imaging, because this is the only way you will improve, and I can almost promise your first efforts will not thrill you. I have a simple log constructed in both Word and Excel, just request a copy and your format preference, and I will be happy to e-mail either or both to you. The good news is that most of the information for your shots will be the same, so you only have to document a few specific items for each shot.

Experiment: A good place to start is with this “free exposure calculation software” from Covington. The other is by checking out the specific exposures taken by an expert like Jerry Lodriguss on his website, who graciously supplies the specifics to the wonderful shots he has posted on the web (notice the information that he logs for each exposure). However, this still does not eliminate the need to experiment, which means bracketing your exposures by varying the f/stop (if through the lens), and exposure times.

What you will find out is that there’s great deal of variables imposed on you by your surroundings. You will also find out rather quickly what limitations are imposed on you by the amount of light pollution present in your environment. In my very light polluted location (between Dallas and f/ort Worth) it is almost useless taking exposures greater than 5 minutes because of the saturation that occurs due to the ambient background light. To an even greater extent than when practicing visual astronomy, “the darker the better” is the catch phrase for astro-imaging.

Piggyback: After having some fun with star trails, I was ready to move on to taking some more sophisticated imaging. The next logical step, is piggybacking your camera on a telescope.

If you have the first 3 taken care of then you will be out somewhere between $15 to $35 for the bracket to get rolling. If you have a nice assortment of lenses for your camera, then you can really go far here. Use the wide angle for nice Milky Way or constellation shots, and telephoto for some nice detailed shots. Just remember, the longer the lens, the longer the exposure, the more challenging the tracking, so start off with some wide field stuff. When you do get into the longer exposures (not if, but when), you will need a couple of additional items, which will also prepare you for the next step, Prime focus.

Additional accessories for longer exposures: This is where things can get expensive, but you can still exercise restraint and keep to the $100 ballpark and get satisfying results.

2.) If you want to go a step further, add a CCD guider for accurate autoguiding of long exposures. ($300 used to very expensive for new imager/guiders)

The illuminated reticle eyepiece has lighted cross hairs to help you keep your telescope exactly on your target. Drop it in place of your regular eyepiece, and practice keeping a star right on target. The CCD guider is a more painless, but more expensive alternative, which does the job for you by controlling your scope directly.

Primefocus: This method uses your telescope as the lens for your camera by coupling it directly to the visual back via some relatively inexpensive hardware. The f/stop will be your telescope focal ratio. With my LX-90 I have an f/10 lens with a focal length of 2032 mm. As you are probably aware by now, this is where we get into long exposure times, but more gratifying results.

3.) Off-axis guider: This device goes between the camera and the telescope, and picks off a bit of the light and directs it up to an opening in which you insert an illuminated reticle eyepiece, or ccd guider. ($80-$450)

4.) (Optional) Focal reducer: This handy item can reduce the focal ratio (f/stop) of your scope. There are a variety available, the most common one is an f/6.3, which takes an f/10 scope down to (you guessed it) an f/6.3, or an f/6.3 scope to an f/4. It also flattens the field, reduces the magnification by about 36%, but increase your field of view (FOV) by 56%. For an f/10 scope, this can essentially reduce exposure times in half. ($130-$180)

Eyepiece Projection: Now in addition to the scope itself, you are magnifying the image through the eyepiece, with corresponding increases in exposure times. In my experience, this is the realm of the ccd autoguiders, or those who are very good with self guidingon any but the brightest objects.

To give you an example, with eyepiece projection through my f/10 scope with a 26mm eyepiece, this produces a focal ratio of f/36.2. It would require about a 3-hour exposure to get a galaxy of average brightness. That being said, choose your objects wisely with this configuration. It can be great for bright objects like; the Moon, planets doubles and star clusters.

1.) Variable Tele-Extender or Variable-Projection Adaptor: This device threads onto the eyepiece-holder. Sliding the cell permits a wide range of magnifications with the same eyepiece.

5.) Most photo-shops are clueless about how to develop an astrophoto prints. I ended up getting a film (negative) scanner. See details in processing.