Telescope Reviews: FILM for Astrophotography

Hey folks, a lot of beginners have not been using the best film for this hobby, and then getting frustrated by the poor results. Do not think that you need high speed (800 ASA) or better film. These speeds are designed for shutter speeds of 2 seconds or less, and have little correlation during long exposures. They also have very large film grain, which makes for poor enlargements.

You need a film with several properties.

1. Small grain. This makes your images sharp, and allows nice enlargements.
2. Excellent RED response. While there are a lot of blue and some green objects in the sky, RED is the one that is most common, and also easily lost with a poor choice of film. This is because the RED spectrum is near the end of the film's sensitivity and film makers often chop it off as unnecessary. They do not care that most of your subjects glow in the deep reds of Hydrogen Alpha. Some films do not even record this all-important spectrum at all! So you need a film that has good blue and green, but also very good response with REDS.
3. Limited Reciprocity Failure. When you shoot a normal object in daylight, if you decrease the amount of light coming in to the camera you can increase the exposure time to compensate. This is reciprocity. However, at long exposures, film tends to FAIL in this regard. This means that if a subject is very dim, a MUCH longer exposure is required to capture it. It also means that what you see in a 10 minute exposure may not be much different than in a 20! On the other hand, if you use a film with LOW reciprocity failure, you will be able to expose longer, AND capture more.

So which films are best?

First I recommend slide film. This requires the least amount of control by an unknowledgeable developer. But more importantly, there just are not many excellent color print films out there. Most have very poor blue and red response in the important wavelengths needed for astrophotography. There are a few color print films that will work, but they are very hard to locate, and require you to HYPERSENSITIZE them by baking them in forming gas (an advanced technique to reduce the reciprocity failure).

My recommendations:

- Kodak Elite Chrome 200 (E200). This film has amazing red response, way down to the Hydrogen Alpha line and produces deep cherry red nebula. It's also very fine grain, and has very low RF. It does suffer slightly in blue response.
- Fujichrome 400F Provia (or Fujichrome Sensia II 400). These have very good color response in blue and red! It also has fine grain, not as fine as E200, but very good. The film also has low RF and can capture below magnitude 18 in 25 minutes at f/4. This is my all-time favorite film.

The best way to stay on top of the changing world of astrophotography films, subscribe to the Astrophotography Mailing List Archives.

Clear Sky to yah!

CF

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Keep it simple, keep it cheap! Meade LXD75 SN8, Orion Guidescope, Olympus OM-1 and STI Stiletto. Celestron 15x70 Binos and SkyWindow. Learn all about POLAR ALIGNMENT with my Drift Method Tutorial and simulator!!