by Sam Bissette
The following article appeared in THE PRACTICAL OBSERVER, December 1995 issue, published by Typographica Publishing Co., 313 Raphael Avenue, Middlesex, NJ, 08846-1224, USA, Gordon Bond, Editor and Publisher. It is reproduced here with the permission of the publisher. A complimentary copy of this issue is available from the publisher on request.
Accidents occasionally produce unusual results. This was the case in 1991 when I was trying out a new microscope. I had placed a 35-mm color slide of the night-time sky on the viewing stage to see what film grain might look like. But after a quick look I immediately forgot about the film grain. To my amazement, many both bright and faint star images and other astronomical information were embedded in the emulsion. Experiments with various magnifications quickly convinced me that this method deserved more time and effort. Thus began a four-year period devoted to perfecting photographic methods and techniques for astronomical observing using a microscope. "Astromicroscopy" is the name I gave this unconventional observation method.
Described most simply, astromicroscopy is a method of photographing the night sky with a 35-mm camera, loaded with color film, and a 50-mm lens, properly filtered, piggybacked on a tracking telescope. The slides produced then become a kind of permanent data bank available for observation at any time. The slides can be projected on a screen or seen under a microscope with magnifications up to 500 diameters. A color slide or photo also can be taken of what is seen through the microscope by mounting a camera on it. This is called "astrophotomicrography."
This method was first presented publicly in 1992 at the Southern Star Astronomical Convention in North Carolina. This was followed by an article in the Reflector of the Astronomical League in May 1994. Complete information about astromicroscopy is available on CompuServe's Astronomy Forum and the Texas Astronomical Society's Stargate BBS in Dallas. A manual--A Guide to Astromicroscopy--can be downloaded from these two sources. It contains a research report on a microscopic examination of the Northern Hemisphere sky with 77 color slide illustrations.
Taking Slides of the Night-time Sky
To photograph the night sky, I use a Nikon 35-mm single lens reflex camera, FE2, with a f/1.4 lens stopped down to f/2, set on bulb exposure, focus set on infinity, and with a Lumicon minus violet filter in combination with an Orion wide-band LPR filter and a lens shade. The Ektachrome 400 used will be pushed one stop when developed to ASA 800. The camera is mounted on a Celestron SCT on a piggyback mount and is aligned with the telescope. After the telescope is polar- aligned, the setting circles are set, and the tracking is started, the sky area to be photographed is determined and the telescope is locked.
The timer is set for an eight-minute exposure. The lens is opened with a locking cable release while the lens shade is covered with a cap, and then the cap is removed. When the exposure time is up, the lens shade is again covered and the shutter released. The usual astrophotography precautions should be taken: dew protection, unwanted light protection, telescope vibration prevention, and fine tuning the tracking. The result should be a fine, sharp color slide of a large area of the sky with no magnification-- quite suitable for microscope viewing.
Viewing the Slide through the Microscope
I use two kinds of microscopes. One is a binocular low-power zoom microscope for viewing, and the other is a traditional three- objective microscope for viewing and photography at magnifications from 50X to 500X. A color-corrected light is used for both instruments. To view a slide, place it on the viewing stage and propel it gently with the fingers over the stage while viewing through the focussed eyepiece. The right ascension and declination coordinates for the slide, recorded when it was taken, can be used to match the slide with a sky atlas. Begin searching with the lowest magnification of the microscope, moving the slide back and forth. Look for double stars, nebulae, star groups, and other astronomical information. Increase magnification when needed. The atlas can provide identification of catalogued objects.
Faint green bars are probably asteroids. At times, satellites will appear. Occasionally, the brighter galaxies can be identified, as well as globular and open star clusters. The viewing sessions can rapidly increase your knowledge of astronomy. Projection of the slides on a two- by three-foot white cardboard screen is also a way of seeing the overall area well.
Photography through the Microscope
To connect the camera to the microscope, first remove the camera lens. Then mount a camera adapter on the microscope. Screw a T-Ring that fits your camera into the adapter, and connect the camera to the T- ring. This way, the optics of the microscope replaces the camera lens. Load the camera with Ektachrome 400 film; set the exposure indicator on automatic, and adjust the camera to give five stops of overexposure by reducing the film speed indicator together with the exposure compensation dial. This step is important for a correct automatic exposure. Place the 50-mm slide on the viewing stage, and with the camera unlocked from the T-ring, locate and center the object to be photographed. Replace the camera, and, looking through the viewfinder, focus the camera with the microscope focus wheel and then lock the microscope focus. The picture is ready to be taken. Release the shutter and wait for the click of the shutter closing which could be from one second or so to perhaps thirty or forty seconds. After the picture has been taken, advance the film. If the process is done carefully, a sharp color slide should be produced.
It is useful to keep a record of exposures with a log showing the name of the object, its coordinates, constellation location, estimated location in millimeters from the center of the 50-mm slide, magnification, etc. This information can then be put on the slide itself after development. Be sure the slides are numbered in the order taken by the processor.
Identifying Astronomical Objects
Stars will be overexposed in the center and will have individual colors around the edge. Look for double and triple stars, as well as stars that are so close together they look like a single oval star. Patches of red indicate specific nebulae or areas of nebulosity. Stars that are surrounded by a red patch may be planetary nebulae. The many faint blue objects are usually stars so photographically faint that they record their presence only by blue dots. Most Messier open star clusters can be examined in detail with star counts, configurations, and double star observations. Globular clusters are pink fuzzy balls. Irregular-shaped objects are a special group, and some can be identified as galaxy groups, faint open clusters, or even coupled galaxies. Green-white ovals are usually optical flares from the camera lens and filters and are usually very near third magnitude stars or brighter. Occasional violet or other unusual colored streaks, patches, or dots are usually film development flaws.
Astromicroscopy is simply another viewing method that has its individual advantages and disadvantages. It is of particular interest to amateur astronomers because of its overall educational value in learning one's way around the night-time sky by looking at a real sky- -not a printed atlas. The ability to probe deeply with the microscope magnification brings into view objects that normally might be missed in conventional telescope viewing. Astromicroscopy also provides an introduction to piggyback photography, the simplest form of astrophotography. Finally, a practical advantage of this method is that it enables one to observe the night sky indoors, at any time or season, and free from such problems as light-polluted skies, insects, and bad weather.
This being said, this method does not give the visual and photographic detail obtained with deep-sky observing. Galaxies and other faint objects usually will not be seen. The experience of being out under the night sky is one enjoyed by active astronomers, and they might not wish to give up that experience for indoor observing. For the very knowledgeable serious astronomer with many years of experience in observing, astromicroscopy may appear to be too simple a method.
As for my own most recent experience with this method, I just completed a year-long project in collaboration with an Australian amateur astronomer, Robert Price. He photographed the entire Southern Hemisphere sky using the astromicroscopy method, allowing me to undertake a slide-by-slide microscopic examination of his beautiful work. The observation log produced more than a hundred entries, supplemented with color slides of interesting astronomical subjects-- both identified and unidentified objects and phenomena. The experience was a real test of astromicroscopy and astrophotomicrography and expanded my knowledge of the Southern Hemisphere half of the sky, which I--a resident of the Northern Hemisphere--never see. Click here to view several of these slides.
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