by John Church
Planetary Photography in the Film Era
Back in the 1970’s (BC = “Before Computers”) I had my own modest home darkroom and did a lot of film developing and B&W printing. I was greatly helped in this effort by advice from a professional photographer at work and an experienced lunar and planetary photographer in the AAAP.
I learned about things such as compensating developers to reduce the inherently high contrast of extra-fine grain film such as Kodak’s High Contrast Copy and a similar film called H&W Control. I also learned about advanced printmaking techniques called “dodging” and “burning in”, and which grades of printing paper to use in various situations. One of my lunar photos and two of my planetary photos taken with the 6-1/4 inch Hastings-Byrne refractor were published in Sky & Telescope. The lunar photo is currently on display in our observatory.
In those days we didn’t have such things as Photoshop or the ability to overlay several negatives to get rid of local film defects and bring out details that an individual exposure might have missed. However, we still got by. What we did was to take many consecutive exposures of the same object and print the best single negative.
Before I took custody of the Hastings-Byrne in the fall of 1972, I used my Edmunds 4-inch refractor for lunar and planetary work. It actually did pretty well. Here is my photo of Mars taken at 11 pm on August 18, 1971 near its very favorable opposition of August 10. Its closest approach to Earth had been on August 12 at a distance of only 34.9 million miles, which is nearly as close as it can get. And to top it off, there was no planetary-wide dust storm such as the one we’ve had to suffer through this year. I was fortunate in that the seeing was very good on that particular evening, helped out by a slightly hazy sky. South is up and east is to the left.
For those interested in the technical details, I used Barlow projection at an effective focal ratio of about f/60 to get as large an image on the negative as I conveniently could. The film was High Contrast Copy in a Praktina SLR with the lens removed, and the exposure time was 12 seconds. I made the print using 22 x floor projection, with the enlarger lens set at f/4 and an exposure of 15 seconds on Kodabromide F-5 paper. I’m afraid, however, that little of this will make much sense these days. Unfortunately, I seem to have mislaid the orginal negatives and so no further enhancement would be possible.
I used a convenient application on the Sky & Telescope website (https://www.skyandtelescope.com/observing/interactive-sky-watching-tools/mars-which-side-is-visible/) to find the longitude of Mars’ central meridian (10 degrees) on that UT date and time, i.e. August 19, 1971 at 0300 UT. This application also provides an image of the surface with the central point shown in a red circle at that time. As with my photo, south is up.
Comparing this with my photo lets us identify several features. First of all, the south polar cap is conspicuous. Sinus Meridiani is just below center and slightly to the left, with Noachis above it. Sinus Sabaeus extends leftward from Sinus Meridiani and Mare Serpentis is above the latter. The well-known feature Syrtis Major is disappearing on the left limb, with Iapygia and Hellas just above. Mare Erythraeum is conspicuous above and to the right of center.
To make things even more interesting, here is a Viking Orbiter mosaic image of Mars in a Mercator projection, with 0 degrees longitude in the center and south up. Many of the same features are obvious here. Hellas has frost on it, which is a fairly common occurrence in this low-lying area. [Credit: NASA]
Note the famous Valles Marineris as a nearly horizontal streak in the westward part of Mare Erythraeum. Could I possibly have caught a hint of it in my own photo? I like to think that maybe I did.