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Photography Using the Questar Telescope
Taking high quality photographs through the Questar telescope, or through any very long focus ("ultra" telephoto) lens requires special considerations in technique and choice of equipment. It is possible to record images using standard photographic procedures employing marginal equipment, but in order to realize the optimum performance possible with fine optics on a consistent basis, it helps to have a basic knowlege of the factors and components that will determine the final quality of your results. So, while there are several basic techniques employed these must be practiced and learned for successful imaging with a Questar or any telescope; each method has its uses or limitations.
Although this article primarily addresses 35mm still photography with the Questar telescope, many of the same principals also apply to applications that use any long focal length lens or microscope, whether it is to be used for imaging on film, or with integrating CCD or "real time" video formats.
This paper was written for those new to photography using a telescope, that want the best results possible from their equipment These procedures are not intended to overly complicate a straight forward photographic pursuit, they just offer considerations and principals that will help you achieve satisfying results.
For telescope photography applications the 35mm format, single lens reflex (SLR) model is the camera of choice. The selection and availability of suitable new and used SLR camera bodies is quite good, their costs are relatively moderate, portability is excellent, and there is a very good selection of high resolution color or black and white films, and fast good definition color films with stable substrates suitable for the task.
The argument "the larger the negative format the better the image quality" does not generally apply to this application unless one requires extreme enlargements into prints showing very fine details, or the coverage of wide fields of view (when using telescopes and associated hardware that can cover larger film formats) are desired. There might be an advantage in adapting to a larger camera format if the film type or emulsion that you need is only available in that format, but with the possible exception of a requirement for an "Instant film" this situation rarely arises.
Small, lightweight, and easily portable telescopes (such as the Questar 3-1/2) are generally not able to cover a film frame size much bigger than the 35mm (24mm x 36mm) still format. Questar offers adapters for some medium format cameras such as the Hasselblad (6cm x 6cm), or one can be fabricated for a special application. However, if you are trying to take advantage of the increased film size for improved image quality then you could be wasting your time. A relatively high magnification may required to fill these larger formats with a Questar, and light losses and other problems caused by these extreme effective focal lengths (EFL) make the pursuit impractical for many applications.
If you are considering the purchase of a film camera to use with your Questar, the camera should ideally offers at least the following features:
The reasons for choosing some of these options is explained later in this article. If you have one of the new highly automated cameras that has everything, but lacks interchangeable parts then you might consider buying a used camera body just for use on your telescope. Some older, models of the Nikon, Canon, Contax, and Olympus cameras will have all the features you need, at reasonable prices.
As we all know, a sharp photograph is dependent upon sharp lens focus at the time of exposure. You now use one or more of the many types of camera focusing screen patterns to focus your camera, the centered split circle image and microprism being two of the most popular designs furnished as standard with film cameras.
Most "off of the shelf" or non-interchangeable focusing screens (microprism or split Image) will not work well with a telescope of extremely long focal length lens. This is because of the relatively slow optical speed of ultra telephoto lenses, or any lens with a maximum aperture ("f stop", or "f ratio") of slower than about f/3.5 to f/5.6 including the Questar, one or both halves of the split circle focus aid pattern in the focus screen appear will dark. And so obtaining an accurate focus using this focus aid becomes impractical.
Consistent and accurate focus at focal lengths above 400mm usually requires a specialized design of focusing screen. The recommended screens are usually listed by the manufacturer in the camera body instruction manual and will usually be designated for use with "ultra telephoto" and/or "microscope" imaging applications. These screens employ a fine matt pattern overall, possibly with a clear spot in the center that may or may not include a small cross hair. Screens are made to fit particular camera bodies. Some screens which we do suggest include the "Type U" by Nikon (available for the F3, F4, and F5 series cameras), and the "1-12" by Olympus (available for the ON-1, and OM-1N bodies). An optional focusing screen may require exposure compensation for correct light readings with some built in camera meters, so read the information supplied with your camera and the screen.
Obtaining critical focus is also made easier by employing a high magnification accessory. An eyepiece magnifier will attach to the camera's finder viewing window, it may be a straight or right angle device (such as the "Varimagni" for Olympus, or the DG-2 for Nikon). The magnifier may possibly be an entire assembly that replaces the camera's porro prism finder assembly; resembling a stove pipe (such as the DW-4 for the Nikon F3) these will also have some diopter focus adjustment to compensate a user with focus related vision deficits.
The special screens that have a clear center spot surrounded with a ground glass periphery can be used with a technique called "parallax focusing". This procedure takes a little practice. Rough focus is obtained on the ground glass, then on the clear area. Fine focus is obtained by moving one's head in a motion that suggests a a "yes" or "no" type of gesture. As the eye moves across the viewing aperture the subject will move or "twitch" in relation to the cross hair. When this movement ceases, and the cross and subject remain constant with each other, correct focus has been obtained. This is not subject to eye sight diopter difference. If it appears sharp for me, then it will appear sharp for you if you know the technique. This is not quite as time consuming as it may sound, and the effort spent mastering this technique will be more than justified In your photographic results.
Because of these focusing screen considerations, a camera that can accept interchangeable focusing screens is very desirable if you plan to do much photography with a telescope; even better if the camera can accept and has available an optional high magnification finder.
After achieving correct focus, the photographer must determine the proper exposure. Many cameras when indexed for through the lens "stop down" or manual metering will perform well with the Questar. Automatic camera can be set to "Aperture Priority" and then their meters will react to lighting changes by selecting an appropriate shutter speed. Remember, the focusing screen that you employ for parallax focusing may require exposure compensation for correct light readings with some built in camera meters, so check the information supplied with your camera and screen. If exposure compensation is needed, you can adjust your film speed dial to compensate for the difference.
Effective "T" or "transmission stop" numbers take into account the lens design efficiency at transmitting light. This is not just a simple measure of the ratio of focal length to aperture diameter (as "focal ratio" is). "T" takes into account the effects of anti reflection and reflective coatings, and of the central secondary mirror obscuration. "T" stop numbers are listed in the Questar instruction manual for configurations including prime focus, and for most combinations of extension tube and optional positive or negative lens combinations. The "T" stop figures are treated In the same way as the more customary "F" stop.
The conventional 3-1/2 inch Questar lens with a full extension tube set attached allows for full 35mm negative coverage; in this configuration its effective photographic speed is rated at about T/18. Use 18 as the effective "F" number for exposure calculations; this is a setting between F/16 and F/22 on a typical camera exposure meter.
If a Questar is attached to an SLR with "off the film plane metering" then one can rely on meter settings. Usually, all exposure compensation will be controlled by adjusting your camera's shutter speed, or by selecting an appropriate film exposure index. Neutral density filters may be used to provide slower shutter speeds within the range of the camera, or for some other desired effect.
If one can approach close to the object that is to be photographed, then a hand held or spot metering system can be a good accessory. With the spot meter you will be metering close to the actual field of the photograph instead of the small portion to which you may be accustomed when using shorter lenses. Use the "T" numbers on the charts for your "F" number meter setting and adjust your shutter speed accordingly.
Of course, the advanced photographer may use incident readings or even "rule of thumb" to determine fairly accurate exposure settings. It is strongly advised especially at the beginning of your telescope use, that exposures be "bracketed": any scene or event that warrants the photographer's interest and investment of time should be exposed above and below the indicated exposure in addition to what is metered and determined to be "right on." This not only acts as insurance for getting the photograph, but also serves as good reference for fine tuning your film, camera, and lens combination.
Even though a positive (slide) film has some desirable characteristics (particularly contrast), if using a negative film then one will have greater exposure latitude. The negative may produce a better print if the exposure time was slightly off nominal.
Notes made about your procedures and camera settings at the time of shooting are invaluable for future evaluation of your photographic technique. You may notice that notes taken a day later or while reviewing your processed film are usually about as effective as no notes at all.
Camera Support & Stability:
Even though the basic 3-1/2 inch Questar barrel assembly weighs only about three pounds and almost any tripod will keep it off the ground with some security, a robust tripod is a must when shooting at extreme focal lengths. Keep in mind that a Questar telescope provides about 30X magnification compared to a conventional 35mm focal length lens! So a cheap or very lightweight camera tripod and head which are designed to hold a camera operating at maybe up to 6X (with about a 200mm lens) will be wholly inadequate for use with an ultra telephoto lens. And the larger lenses such as our Questar 7 will require even more rigid supports.
A tripod of marginal quality that produces rough and jerky head movement is barely noticed with lenses of short focal length, yet can become three or more photographic fields of view jumps with telephoto lenses! The user will immediately begin to appreciate a fine quality tripod with a pan head; one with smooth motions left to right (azimuth) and up or down (elevation), and with positive "no creep" locks.
When using an SLR camera with an ultra telephoto lens, as it takes a picture there are two major mechanical components in motion that can affect the final image: the shutter and the view finder mirror. One may notice that even with a sturdy tripod support that your small, lightweight 35mm camera can react rather violently during exposures when the mirror and shutter are in operation. Some are smoother than others but all currently available 35mm SLR cameras shake, and shake enough to seriously degrade the sharpness possible with the Questar. The problem comes from these objects being in motion, which are generally in two separate directions causing the camera to oscillate in an almost circular manner.
The SLR has a mirror that normally rests in front of the camera shutter curtain to divert light from the lens to the viewfinder. When one presses the camera shutter release the mirror will swing up rapidly (kicking the camera in a vertical direction) to allow the light to continue on through to the shutter. The mass of the mirror in motion slapping into place will produce vibrations that are just perceptible to the camera operator but will resonate in the camera for some milliseconds as the mirror is opening.
When the shutter is released and the reflex mirror snaps up, the shutter slashes its way across the back of the camera releasing energy in the horizontal plane (yes some shutters do move in the vertical direction, but they still shake). Using an air release and hanging a hundred pounds of shot bags on the tripod will not stop these camera acrobatics, and in most cases dampen them only slightly.
If you have doubts that this is a serious problem, focus your telescope on a distant object at high power with the camera attached. With the camera cocked, look through the telescope's eyepiece and release the shutter with a cable, air release, or the cameras timer, and watch what happens. It almost looks as though someone has kicked the tripod doesn't it?
Oh, you say your camera is equipped with a mirror lock-up provision, great, lock it up and try again. Yes it's not as bad, but the shake is still there. It is a fact, unless you lock up a mirror prior to the exposure, and are using the very finest professional cameras with a very "quiet" shutter you probably cannot get the sharpest photographs when the image is moving during exposure and "smearing" the image across the film.
Another manner by which these vibrations may be lessened, but not totally eliminated is by using a fixture to create a common mounting foundation for the camera and lens as a unit. Questar currently offers two types of camera cradles that will do this conveniently. A rise/fall platform at the camera end of the aluminum beam makes matching your camera's height to the lens a simple process. Tying the two components together makes for a sturdy, integrated unit that Is easy to use.
With an accurate camera focus, a robust tripod, a calm air path, and the camera mirror locked up prior to exposure, some shutter speeds will allow photographs that may be of sufficient quality for some photographers, or meet the needs of specific applications. Again, we are talking about trying to achieve results that take advantage of the images possible when using high resolution Questar optics.
Another way to insure vibration less exposures is to bypass the camera shutter altogether.
The shutter card exposure procedure eliminates camera shake. This is a version of the old press photographer's "hat trick" for long exposures. A diagram for a slotted card is included below for suggestions on measurements. Make the card from ad board or foam core, and cover it with black flocked paper using a spray adhesive. Flocked paper wears rapidly but it is very black and nonreflective.
Illustration 1. Shutter card. Note that all card dimensions may be altered with the exception of the 2 inch slot.
A rapid pulling of the card from up to down (or from down to up) produces a speed of about 1/125th of a second; slower will result in about 1/60th, etc. Remove the card entirely for a moment, then replace the solid portion of card for exposures slower than about 1/2 second.
Illustration 2. Using a Shutter card. Questar telescope with camera shown at left, shutter card in front of lens.
This may seem like a drastic extreme to resort to, but this technique allows you to get shake free photographs at reasonable shutter speeds (of about 1/125th of a second and slower) without additional expensive and specially made components. This procedure really does work, and works very well with a little practice.
If you own a camera with the attributes just discussed and an automatic exposure system, try this variation of the card trick. Compose your photograph and focus. Just before releasing the shutter, cover the front of the lens with a black card. With the card in place release the shutter with an air or cable release, and allow a very short time for vibrations to settle out, and then rapidly remove the card. With the card in place the camera is receiving insufficient light for exposure and the shutter remains open. When the card is removed light strikes the film and the system meters the exposure and closes the shutter. The only vibration that occurs is during the brief instant when the shutter curtain moves to close. This procedure will not work with auto exposure systems that set the lens aperture to adjust exposure. Remember, in any of these card applications the card should never contact the telescope. Make the card as black as possible and try to let your shadow fall upon it to help avoid fogging the film, especially when using films with fast emulsions.
If you have a subject that allows you to control the illumination, such as in a studio or close-up situation (insects flowers, birds, etc.), try leaving your camera shutter open on the "B" or "T" setting while working in a dark place, and expose using only a light source. The action stopping ability of a strobe, flash, or even the timed use of an incandescent lamp will eliminate any vibration problems caused by the camera.
We always suggest the use of a timer shutter release, or better yet a remote cable or air release, or electronic remote control for making exposures. We prefer a cable or air release with a tube no longer than three feet unless more is required. If a cable is used then it should be soft and flexible enough to isolate your movements from the camera. In addition, a motor drive or auto winder may be an asset; this is not for speed, although it s an advantage in this respect but it allows you to compose your photo accurately and work for extended periods for bracketing and card work without disturbing the camera as you recock the shutter. The additional weight also helps to dampen vibrations.
Motion picture cameras also vibrate the system, especially at start-up. And so these should be used with a camera cradle or unifying beam type of tripod mounting. Film cameras that generate lots of movement have been used successfully employing two separate mounting platforms and a light tight, non-contacting, tube between the camera and lens.
The vibration problems discussed above do not apply to the use of video cameras excepting some types of "still video" cameras that do employ mechanical shutters. Using long lenses with video is great because video imaging is done without the movement any mechanical parts, and you are able to view your results as you shoot. The importance of a quality tripod still applies though, and in this situation you may seriously want to consider a slow ratio geared head for positioning control if you will be tracking an object, or changing fields of view while recording.
Now that you are aware of the photographic considerations that effect your choices of equipment and technique using the Questar as a long focus lens, we will shift to variables over which you have very little control but that also have definite effects on photographic results.
The air that separates us from our subjects could be equated to a type of "liquid" medium. This liquid is normally not like that found in a still pool, but more similar to that observed in a slow running stream. The transparency of the air can be equated to clear or clouded water, and atmospheric turbulence to the flow of the stream.
You will quickly notice that photos taken through long air paths will show an apparent lack of contrast. This brings up a point regarding telephoto effects. Long lenses do seem to "compress perspective", and accentuate haze effects, etc. Though these comments may be used with some accuracy within the photographic community, these statements may be thought of in a different way.
A photograph of a distant scene, say one mile from the camera position, that includes trees, a human figure, and an automobile, shot on a fairly clear day through the telescope and viewed as a photographic print will have a distinct look. The perspective seems to be compressed. Trees that may have an actual separation in depth of one hundred feet or more appear to be pushed together, almost on the same plane. The figure in the photograph that is considerably closer to the lens than the automobile will appear smaller and out of scale with the car. A loss of normal contrast may also be noted, and sharpness may not be quite what is expected because of turbulence in the air path.
If this scene had been shot at the same time, from the same position with a normal or short telephoto camera lens, and a full negative print of like size where made, the print would exhibit great apparent sharpness, contrast, and a more three dimensional view of closer foreground objects in the frame. But let's compare apples and apples and then see what happens.
Photograph an area when using the normal lens, and then again from the same spot with a telephoto lens (a very small area of the normal lens appears on the film). If both are enlarged to make a print that matches the area content, you will note some interesting effects. Disregarding the fact of increased film grain size, and the film's limited lack of sharpness because of the great enlargement, the pictures will look the same! The contrast matches, perspective matches. Trees are still pushed together and sizes remain the same, and the atmospheric effects on sharpness is the same. It looks as though we really didn't change perspective at all, did we?
A couple strolling down the beach at sunset will obscure your sight of the sun if it is observed while the couple is twenty feet distant; even though the sun is approximately 865,000 miles in diameter. If this couple is now observed in the same line of sight from a distance of two thousand feet with the Questar, they suddenly begin to resemble the romantic pair you saw silhouetted against that huge red solar disk on the cover of a travel brochure. Again, if technically possible a photograph shot with a shorter lens and then enlarged to create a print with the same image size as the telescope image, will exhibit the same appearance as the telescope print.
The point we are trying to make here is that compromises in apparent quality of very long focal length photographs taken with theoretically perfect lenses, are typically caused by natural conditions and are not failures in lens performance.
We have briefly touched on the two major natural limiting factors of long focal length photography. Just as our model stream flows, so does the air. A smooth continuous flow, such as a light breeze that remains uniform between you and the subject is great! Light reflected from your subject arrives at your lens relatively undisturbed and undistorted. When differences in air flow occur we have a problem. Just as in the stream, curves, obstacles, temperature differences, and depth create eddies that affect your ability to clearly see the stream bed.
What we may commonly refer to as "heat waves" is the basic problem. These turbulent eddies and currents bend and scramble light. The light no longer travels in a straight unhindered line to your lens. This effect causes unsharp photographs by not only distorting the image, but also by causing the image to "scintillate" or move on the film during exposure. Contrary to what many believe this turbulence can be as annoying on a cold day as on a hot one. The key phrase here is temperature difference in the path, not just the high or low temperature. If the ambient temperature is a chilly forty degrees during a sunny day, then shooting over a roof top or a dark paved area will normally yield poor results because the warm air rising from these heated surfaces roll, or boil as they mix with the cooler air of a different density. Even shooting out through the open window of a heated room can cause extreme distortion from the airflow across the front aperture of the lens even though long range "seeing conditions" may be excellent.
Turbulence can also be a problem in close-up work. Heat from incandescent lamps, fan currents from other instrumentation, or the temperature extremes of the subject itself, can all cause scintillation that can seriously degrade high magnification photographic or visual quality.
Atmospheric haze is a little more apparent to the unaided eye. Most of the stuff that obscures our skies and gives us those beautiful red sunsets is particulate matter. There is no way to filter this type of material out of your photographs. About all you can do is to shoot through as little air as possible (get closer). Light scatter from moisture and ultra violet (blue blur) effects can be treated to some degree with filters. We will talk about these shortly.
Because these facts of nature are basically uncontrollable, procedures that take advantage of your surroundings are about the only way to lessen these problems. Try to got back into that smooth flow or quiet pool area in the middle of the stream. If possible keep your line of sight as far above the ground as possible, shoot from a hill or the top of a man made structure. Avoid a line of sight that has features that include objects with gross temperature differences from the surrounding air. Sometimes shooting across a body of water may yield excellent seeing conditions, but sometimes the opposite may be true.
If it is at all possible, plan your photo sessions for times early or late in the day. It is during these periods you are most likely to experience the time sometimes referred to as "the null." This is the period of time that night and daytime temperature extremes are beginning to overlap, and all things come as close to the same temperature as possible while still offering enough light for photography. Take some time during a leisurely day to find this "prime time". Set your telescope out about an hour and a half before sunset and acquire and object at a considerable distance. Check the conditions through the eyepiece about every ten or fifteen minutes. Soon a time will come when seeing conditions will change from minute to minute. The calmest time may occur before sunset and continue on into the darkness, or you may see conditions deteriorate again before sunset. The lesson here is that good conditions may be very short in duration and subject to change at anytime. Shoot while you have the chance, it could possibly get better, but the conditions can just as easily deteriorate.
The eye and the brain act as a very sophisticated image processor. As you look through the eyepiece, your brain can interpret a fluctuating image and make perfect sense of it all, and in great detail. Unfortunately, your film is not that adaptable and it just lays there very passively recording the information just as its received. If the light reflected from your subject dances around in a area larger than it should actually displace on the film, an unsharp photograph will result. The next time you find conditions that you feel are very good, look through the telescope's eyepiece at high power. Try to find a lined object (like a twig or pole), or a point source of light In the field at a long distance, and slowly bring the image slightly out of focus. Does the image twitch? If it does, you have demonstrated that you can overlook small amounts of scintillation that the film cannot. If you see no movement, shoot now because this condition is not likely to last for long!
The Quick-Change filter holder and Drop-In filters available from Company Seven for the Questar allow filter use and changes without removing the camera from the telescope. Photographs of most subjects can be taken without any filtration, but under some circumstances the use of a filter may be advisable.
The UV (ultra violet blocking) filter helps remove short wave length light that is scattered in the atmosphere. This light serves no real useful purpose in our photographs and tends to lessen subject contrast. This filter generally needs no exposure compensation, but when adding any additional optical surfaces into the system be sure to recheck your focus carefully.
Basic Equipment and Techniques of Astronomical Imaging with The Questar
There are many possible configurations, and accessories available for the Questar both from the factory and also from third parties most of which Company Seven offers. Many new choices arecoming available since CCD astronomy has recently become so capable and affordable. Company Seven maintains much of this equipment on display in our showroom, we also describe some of the hardware in our Internet Site, and maintain some articles at our "Library" section of the Web Site but, this will not be enough to help everyone.
For astronomical imaging one should be certain to employ a Questar telescope mounted onto either a Fork Equatorial Mount (as furnished with the "Standard" and "Duplex" models) or precisely attached onto an optional German Equatorial Mount each of which has a clock drive mechanism to precisely keep the telescope on target while the Earth rotates about its axis. An accurate set up and Polar alignment of the mount will help to insure very satisfactory results.
These are the most common techniques for film or CCD imaging (possibly with optional Color Filter Wheel) with a Questar are:
1) Piggyback - for large objects, providing wide sky coverage for astronomy. The telescope drive is the tracking platform, the Questar telescope becomes a "photo-guide telescope". This requires some optional hardware:
b) Guiding Eyepiece with an illuminated reticle
d) (Optional for CCD) CCD Camera with a Camera Lens Adaptor, and computer
OR (For Film) Camera with moderate Tele to Wide Angle Lens, Cable Release, Mirror Lockup.
2) Prime Focus Short Exposure - basically a camera shooting directly through the telescope exposing for seconds or fraction of seconds (for Sun and Moon). Usually this requires:
b) Camera Adapter Ring ("P" Series)
d) (Optional for CCD) CCD Camera with a Camera Lens Adaptor, and computer
OR (For Film) Camera, Cable Release, Mirror Lock up.
3) Prime Focus Long Exposure Film - basically a camera shooting directly through the telescope, exposing for minutes or longer. Suitable for astronomy - imaging of the faint objects where time exposures are necessary. We suggest:
b) Off Axis Guider
c) Guiding Eyepiece with an illuminated reticle
d) Declination Control Motor
e) Camera Adapter Ring ("P" Series)
f) Counterweight (certainly)
g) Drive Corrector (Powerguide, Powerguide II for example)
h) Camera, with Cable Release, Mirror Lock up.
OR for Prime Focus Long Exposure with CCD - CCD camera shooting directly through the telescope, exposing for minutes or longer. Suitable for astronomy - imaging of the very faint objects (even from suburban settings) where time exposures are necessary. We suggest:
b) CCD Camera with autoguide CCD (SBIG Model ST-7 or ST-8 for example)
CCD camera with reliable Track & Accumulate function
c) Declination Control Motor
d) Counterweight (certainly)
e) Drive Corrector (Powerguide, or Powerguide II for example)
4) Modified Prime Focus - a camera with extension tubes to vary the effective focal length and focal ratio shooting through the telescope. Suitable for research uses, long distance microscopy, and astronomy. We suggest:
b) Camera Adapter Ring ("P" Series)
c) Counterweight (possibly)
d) (Optional for CCD) CCD Camera with a Camera Lens Adaptor, and computer
OR (For Film) Camera, with Cable Release, Mirror Lock up.
5) Modified Prime Focus - a camera with Positive (Telecompressor) or Negative (Barlow) to vary the effective focal length and focal ratio shooting through the telescope. Suitable for research uses, long distance microscopy, and astronomy. This will require:
b) Camera Adapter Ring ("P" Series)
c) Positive or Negative Lens installed onto the Swivel Coupling or Extension Tube
d) Counterweight (almost certainly)
e) (Optional for CCD) CCD Camera with a Camera Lens Adaptor, and computer
OR (For Film) Camera, with Cable Release, Mirror Lock up.
6) Telextender - a camera with and eyepiece/ocular employed as a high magnification Negative (Barlow) element to dramatically increase the effective focal length and focal ratio shooting through the telescope. Suitable for research uses, long distance microscopy, and high magnification astronomy (planets, double stars, etc.). This will require:
b) Camera Adapter Ring ("P" Series)
c) Eyepiece installed into the Extension Tube Set, on the Swivel Coupling
e) film Camera with Cable Release, Mirror Lock up.
b) High Resolution CCD Camera CCD (SBIG Model ST-5/7/7E, or Celestron Pixcel 237
for example) possibly with optional Color Filter Wheel.
d) Right Ascension Drive.
Please understand that the choice of technique and hardware for astrophotography are matters which can require some thought and discussion in order to reach a suitable conclusion. This article can only serve as a basic outline, as it does not go into detail about other optional hardware choices (filters, etc.), or detailed operational techniques (film choice, exposure time, etc.). We would be pleased to discuss these aspects in some detail with you in order to advise you further. It is best if you can arrange to visit our showroom in Laurel, Maryland where we maintain a good selection of instruments and the associated accessories on display.
Contents Copyright 1994-98 Company Seven and Questar Corp. All Rights Reserved