Age old question; ever-changing answer.  Right now, as of December 2003, the standard films for much of astrophotography is Kodak E200/Elitechrome 200 slide film and Fuji Provia 400F slide film.   These film have become the standard for several reasons:

• They are highly sensitive to the red color of emission nebula
• They lose less of their speed over time when compared to other non-hypered films (more on hypered film later)
• They are the last remaining choices of films available that meets the requirements of astrophotographers
• They have finer grain than most any other color emulsion which makes them suitable for enlargements
• They can be push processed an extra one or two stops without a significant increase in grain.

Fuji Provia 400F is a professional film and can only be found at professional camera shops and on-line ($7.00 a roll from B & H Photo).  Kodak E200 is like the 400F in that it is also a professional film, making it somewhat hard to find, though Elitechrome 200 is a consumer version of the same flim and is easily found anywhere film is sold.  Between the two, the Fuji Provia is the more balanced film for color, with better blue sensitivity that the E200, making the Fuji the best film for galaxies and reflection nebulae.  The E200, while a bit weak in the blue response, is more sensitive to red light, meaning that it is the film of choice for emission nebulae.  

The only negative factor of either film is that they are slide emulsions, not print, though the positives outweigh the negatives.  Slide film takes more time to develop, so feedback isn't as immediate as getting prints from a local one-hour photo shop.  But slide film doesn't show defects, such as scratches and dust, as readily as a typical negative when scanned, thus shortening your post-processing time.  Plus, there just isn't a print film in production, at this time, that can compete with these slide films.  

Other outstanding films are no longer produced or have been replaced by more current emulsions.  My favorite is Kodak Royal Gold 400 Select Series, also called Supra 400 in the professional variety of the same emulsion.   But this film is now replaced by the Kodak Royal Supra series which isn't a very good performer unless used hypered.  The RG400, much like the PPF400 and LE400 before it, had such a good color balance including the all important red spectrum along the hydrogen alpha line (656 nm).  These films also function well on galaxies since they have good sensitivity to the blue part of the spectrum.  As I already mentioned, my experience is that E200 lacks in this area.  It takes much longer exposures with E200 to get the blue saturation of most any other film.  But since most other films have good sensitivity to blue, one of any number of Kodak or Fuji films, among others, should give good results on galaxies in the shorter exposure lengths.  Hypered Royal Gold 200 is a favorite for longer exposures since it loses little speed over time, as is true of any hypersensitized film.

One of the more difficult object-types to photograph are planetary nebulae.  They emit a more greenish color along the oxygen-III spectral line which is normally at the point of crossover between blue and green sensitivity. So color images of these objects often are inaccurate because of the overbalance of reds and blues. Interestingly, many tri-color filters used in CCD work are lacking in this area as well.  Finding good filters that cover this crossover gap is important to CCD imagers. Finding a good film for this purpose is just as difficult.

But perhaps the best film for astrophotography is actually a black and white film.   Kodak Technical Pan 2415 film is a very slow (ISO 25) film with tremendously fine grain. This alone makes it unsuitable for astrophotography. But when you hypersensitize this film it gets something like a ten-fold speed increase losing very little speed over time.  Plus, it too is extended across the red spectrum making it a terrific film for emission nebula.  

Many photographers will use TP 2415 to add a luminance layer to color information from another image.  Since it has such fine grain and can be used with filters to match the spectra of the objects you are shooting (i.e. using a hydrogen-alpha filter for emission nebula) these black and white images can not only provide tremendous detail to such objects but can then be enlarged greatly for wall prints.  Using such a fine grained, detailed image as a luminance layer works well since this information is retained when the color information is added.   In fact, some of the best astrophotographers around will take it a step further.   Some, like Chuck Vaughn, will take four similar exposures with TP2415 using a luminance layer and individual RGB-filtered layers and will compose some pretty incredible images. It's a lot of work but the results are amazing.

As film makers constantly cater to the professional portrait photographer more and more film is becoming less suitable to astrophotography.  Red sensitive emulsions are disappearing because they tend to make skin tones look unnatural.  Perhaps it's a good thing that CCDs are coming into the reach of many beginning and experienced astrophotographers.  The number of good films for astrophotography (short of hypering everything) seem to decrease on a daily basis. 

Therefore, don't shoot yourself in the foot by choosing a poor film.  It's hard enough to get good shots.  No other factor affects an otherwise good effort than choosing a poor film. 

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