Since the mid 1970's, I've been interested in Astronomy. I started with visual "deep sky" observing, but seeing the photographs taken by other amateur astronomers in Astronomy and Sky and Telescope magazines made me long for something more than a pleasant 'memory' of a celestial object. After a friend let me use his Celestron 8 as a guidescope for my 300mm telephoto lens to do a few short exposures of some bright nebulae and star clusters.....I guess you can figure out the rest of the story :-).

In early 1981, I ordered a Byers 812 German Equatorial mount and a Meade model 1060 Newtonian (10" f/6) tube assembly. The smaller scope 'piggybacked' is a 6" f/5 Newtonian added later for a high power finderscope. The 10" Newtonian tube assembly has been modified with heavy duty optical support systems, a custom made Off-Axis guider with a focal plane interrupt vibrationless shutter. This is used to stop the exposure without closing the 35mm camera shutter. This particular feature really makes long exposure photography much more bearable. I'll explain this later.

More features have been added to improve the final image, such as a Celestron Coma Corrector which is designed to improve the focus across the entire 35mm film frame. This problem, inherent in 'fast' Newtonians (any focal ratio below f/7) is caused by the inability of the optical system to bring all light rays to sharp focus on a flat film plane. I have also added light baffles on the back of the scope and a tube extension to the front of the scope to keep out unwanted stray light. The last thing I did was to create a series of resistor loops to provide gentle heat to the diagonal mirror, coma corrector and the guiding eyepiece. I live in a fairly humid area on the East coast of Virginia and do my photography at a dark site in NE North Carolina. (about 20 miles west of the Great Dismal Swamp) Optics will fog quickly in this climate.

With the Newtonian optical system, Off-Axis guiding, in my opinion is the only option for doing long exposure astrophotography. Shortly after receiving my telescope, I designed and built (with a little help from a machinist friend) my OAG. The total magnification with a 3.5x barlow and 12mm eyepiece is about 450x. The guide stars focus pretty well, especially when the seeing is very good. No blobs! My decision to go this route for guiding the main scope was based on previous experience with using a separate guidescope. Flexure in both optical systems during the exposure interval caused the star images to form lines or hook shapes, which ruined my photos. The OAG has solved the flexure problem by using a guide star with the same optical system used to record the image. Here is a description of a typical photo "shoot": After the scope is thoroughly polar aligned, (using the drift method) I will select an object to photograph that is near the meridian. The meridian can be described as an imaginary line running from the north directly overhead to the south. As a celestial object crosses the meridian, the Earth's atmosphere is thinnest. This is the optimum time to photograph an object as seeing and transparency will be at its best. After locating the object with my setting circles, I center it in the 6" finder. The object will then be perfectly centered in the 10" scope camera's viewfinder. I then select a guide star (hopefully a bright one :))and then the last step is to locate a bright star such as Capella or Vega that is nearest to the location of my photo subject. In the picture above of my OAG, there is a magnifier attached to the viewfinder of my camera. This gives a very highly magnified view of an area around the pentaprism spot in the camera viewfinder. I can then easily focus the bright star to a fine pinpoint, then lock the focus down, re-center the object in the finder, which usually re-centers the guide star.(the magnifier is removed from the camera before beginning the exposure) I'm now ready to open shutter and guide the scope. I guide all of my exposures manually.

With the switch to hypersensitized Tech Pan film, my exposure times increased to up to three hours in duration for a single object. The Byers 812 mounting has a limited run time of about two hours with its right ascension sector drive. I added a vibrationless shutter to interrupt the focal plane while still allowing the guide star to be viewed. With this shutter, I can now guide the telescope as long I wish. A simple procedure is used to reset the right ascension drive while in mid-exposure. When the exposure is about halfway done, usually around 60 to 90 minutes depending on total exposure time, I will close the focal plane shutter. I then reset the drive and locate the object in the 6" finder, center it and locate the guide star. I am now ready to resume the exposure.

It's nice to be able to stop the exposure to take a coffee break etc. The shutter is also handy to have when you see an airplane lit up like a Christmas tree heading right for the area of sky that you're shooting. It always seems like whatever location I use to photograph from, I'm deluged with lots of air traffic overhead. The Byers mount tracks very well and I usually don't have to keep my eye glued to the guiding eyepiece, which allows me to keep a wary eye out for aircraft.

When I started my deep sky collection of images, I used the old Kodak 103a films. The speed was rated at about ASA 400 and there were three different versions available. 103a-F (panchromatic), 103a-E (red sensitive), and 103a-O (blue sensitive). As you can see in the photo on the right, the film was very grainy, especially when trying to shoot smaller objects less than 10 minutes of arc in size, such as the galaxy shown in the images above with only 60 inches of focal length. I used these emulsions until 1988 when I switched over to hypersensitized Kodak Technical Pan film for obvious reasons as can be seen in the photo on the left. Exposure times were 130 minutes for the Tech Pan image and 60 minutes for the 103a image. Both images were made with the same telescope. I use a Lumicon model "600" hypering kit with a hand vacuum pump. The unhypered Tech Pan film is rolled onto a 35mm film developing reel and placed in the hypering chamber, in the dark of course. I then pull the vacuum down to about 29 inches (all that I can get out of the little hand pump). The film is then "baked" for 60 minutes @ 50 degrees centigrade. Finally, I flush the hypering chamber with forming gas (8% hydrogen/92% nitrogen) and pull the chamber down to 29 inches and repeat the flush/vacuum cycle once more before pressurizing to 6 psi. I then let the film bake for 60 hours @ 50 degrees centigrade. When the film is finished hypering, I will roll it back into a 35mm film cassette, place it in a homemade vacuum chamber and store it in the freezer until I'm ready to collect ancient photons.