Film Astrophotography

Film Based Astrophotography

CAMERA & FILM:

Film...I have used many different films over the years, changing films when the manufacturers changed to film characteristics making them unsuitable for use in celestial photography, mainly both 400 and 800 speed print films from Fuji. Finally I have settled Kodak Elite Chrome 200 and Ektachrome professional 200 as they have good reciprocity failure...they remain sensitive over exposures longer than 1 miniute and excellent color rendition, especially reds in emission nebulae.

Cameras usually used are fully manual 35mm single lens reflex cameras with removable interchangable lenses. The camera must be capable of locking the shutter open for extended exposures, automatic cameras soon exhaust the batteries, especially in sub freezing weather. Examples are the Yashica FX-7 and FX-3 series. It is a fact appreciated by mostly professional photographers that these cameras are extremely rugged and function well in temperatures of -25 C and even colder.

Vintage Visuals in Calgary are a great source for manual 35mm SLR's

Another requirement is that of a good quality locking cable release that allows one to lock open the shutter and close it with a minimum of vibration.

Elite Chrome specs (PDF)

E-200 spcs (PDF)

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Develop the film and leave uncut and unmounted. Use a high resolution scanner like the Epson 3170 that is capable of scanning slides as well as prints and negatives at very high resolutions. This scanner has Adobe Photoshop bundled with it that makes a powerful editing tool for enhancing your photos.

CACULATING EXPOSURES:

Typically we used to manually calculate exposures, but now there are at least two programs that are useful:

Covington's Calulator

Exposure tables for my equipment with calculations using Covington's program.

Jeff Polston's Starshot

These simply require you enter your particular telescope, eyepiece, or camera lens and film to get the exposure for the object intended.

MOUNTS:

A reasonably accurate equatorial mount is required in order to be able to track accurately enough for untrailed stars in your photos. I have found the Synta EQ6 is excellent for this purpose and heavy duty enough to mount substantial telescope/camera setups, with dual axis smooth drives.

PIGGY BACK SETUP:

Piggy backing the camera on the telescope involves mounting an adjustable bracket on the main scope so as to be able to point the camera independantly of the scope to fram subjects properly. Lenses in the 28mm to 70 mm range don't usually require guiding and the scope and camera can be aimed and the driven mount left to run.

Lenses of focal lengths over 70mm require a guiding illuminated reticle eyepiece and the aquisition of a bright guide star to guide out right ascension drive variations and remain centered in declination. I use a Meade 9mm guiding eyepiece with the Rigel Systems Pulseguide, the blinking reticle is adjustable and allows your eye tiny rests between pulses, allowing longer guiding times

For deep sky objects, I typically use lenses from 200mm to 500mm focal lengths, using the main telescope to guide. Rule of thumb is that the guiding scope focal length should be at least twice that of the photographic lens, example 1000mmm to 1200mm scope for a 500mm lens.

Piggybacked Telephoto Setup.

Leonid meteors, 10 minutes with 28mm f/2.5 lens

Constellation Orion, 15 minutes with 200mm f/4 lens

Rosette Nebula, 20 minutes with 500mm f/5.6 lens

PRIME FOCUS:

Prime focus is shooting directly though the telescope with the camera lens removed and using the telescope itself as super telephoto lens. 35mm cameras require a T-ring adapter that fits standard T threads and the camera's lens mount. A guiding set up is required and I favor using a seperate guide scope with a barlow and guiding eyepiece. Equivalent focal length must at least equal that of the main telescope. This is the primary setup for most deep sky objects as well as eclipses.

Prime focus guide scope.

Prime focus M42 12 minutes Fuji 400 film.

Lunar total eclipse, May 2003, 1/30 second.

EYEPIECE PROJECTION:

This is high resolution, high magnification work. A lot of amateurs have eschewed this level of film based imaging in favor of digital cameras and webcams. However, I live in a country at a latitude where we experience winter 8 months of the year and the best observing and imaging is done in the middle of winter. None of the electronic imagers function in below zero weather and certainly not the computers required to image with these devices unless you have an observatory with a seperate heated space. As most of my imaging is done in the field, I have decided to develop my skills as an emulsion based imager of the solar system as well as deep sky, besides film becomes more sensitive in cold weather.

Basic eyepiece projection adapter with eyepiece. In addition, a telexetender can be added to extend the projection distance even longer, resulting in higher magnification at the film plane. It is best to use a lower power eyepiece that gives a sharp image and then use the projection distance to increase magnification than a higher powered eyepiece that will result in a blurry image at too high a magnification. Filters can be added to increase sharpness or cut glare.

Examples of high resoultion images, exposure times typically 1/4 to 1 second, accomplished with the 'hat trick'.

RECORD KEEPING:

It is vital that you keep a record of each and every shot so as to eliminate unproductive setups and exposures and maximize the effective techiques. Below is a sample of the log sheets I use for my photos.

The final word is bracket your shots, shoot lots of film, record your setup and exposure data. I intend to add a processing guide to this page in the future.