Beginning Astrophotography

(BASICS)

 

 

What do I need? CONSTELLATIONS CIRCUMPOLAR PHOTOGRAPHY
Where do I go? "DOT-STREAK" PHOTOGRAPHY PLANETARY MOTION PHOTOGRAPHY
What do I do? DEFOCUSING PHOTOGRAPHY SUN & MOON PHOTOGRAPHY

 

This tutorial section gives you the basics for amateur astrophotography.  Astrophotography can be done by students for school or Science Fair projects as well as by amateur astronomers.  For examples of astrophotography done by amateur astronomers, visit the EAAA Astrophoto Gallery.



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What do I need?

Astrophotography, also called "star shooting," can be done quite simply by even young students if they have the proper equipment and the ability to focus their eyesight through a viewfinder. Until the age of four or five, many children cannot coordinate their vision to accomplish this. Most elementary students, however, have enough fine muscle control and focusing ability to enable them to take fine astrophotos of constellations, comets, or planets.
Astrophotography can become quite complex, as the photographer moves up from simple camera work to prime-focus photography (using a telescope as a telephoto lens), digital work, and more.

The basic equipment needed for simple astrophotography is:

1) a star chart or field guide unless you are photographing constellations or objects that you are familiar with and can find easily

2) a 35 mm SLR (Single Lens Reflex) camera with a 50-55 mm lens and a "Bulb" (B) or "T" setting which allows the lens of the camera to stay open until you end the exposure

3) a camera tripod

4) a cable release (screwed into the shutter release button so you can begin and end photos without exerting any pressure on the camera body (thus avoiding streaking or blurring through magnified camera motion)

5) 35 mm color film (several 12 or 24 exposure rolls rather than 36 exposure rolls that can't be finished in a reasonable amount of time)

6) a flashlight with a red filter or red cellophane to use if you are using the star chart, but which does not interfere with photos in progress or your dark adaptation.

7) a log book (Record each shot: the subject; the film type and speed, the duration of the exposure, and the atmospheric conditions, otherwise, you may not know what those shots were supposed to be, and you won't learn from mistakes so that you can correct them next time.  The log of exposure times when matched with your photos will show you what exposure resulted in the best shot.) 

Very high speed film, such as ASA 1600 or 3200, can record images with a very low light source, but even a streetlamp or the porch light coming from a neighbor's house will cause overexposure, and will wash out the sky. Taking a longer exposure with a slower speed of film (ASA 200 or ASA 400) will increase image clarity while maintaining a good, dark background sky. Different films will give different hues to the "blackness" of the night sky. Experimentation with the various brands of film is the only way to achieve personal satisfaction. Check the film used by various astronomy club members in the Members' Gallery section and its links on the EAAA web page. This experimentation is one reason that you should by the smallest roll of film possible. The other reason for the smaller roll is because it is hard to take up a roll of even 24 exposures in one sitting.

Film deteriorates, so you want to use up your film as soon as possible after you open and load it. (Keep unused film in a waterproof, zipped shut, plastic storage bag in your freezer--take it out and load it just before you leave for a photo shoot).

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Where do I go?

Astrophotography can be done from your yard, an abandoned airfield, an open field in the country, camping areas in state or federal parks, or at the beach. One of the main concerns for a photo site is not just whether or not the site is very dark and free of light pollution, but whether you have adequate security. Never go to a remote location without taking at least a small group of friends. It would also be wise to tell someone where you went and what time you expect to return home. Groups of four or five will not only give you better security, but will also provide for companionship and technique sharing.

A group stargaze and overnight picnic provides a nice alternative to the standard backyard cookout. If you choose a campout at a dark sky site (Open Pond in Conecah State Forest, or the Munson site in Munson, Florida), you have the security of ranger patrols and helpful campers.

Many astronomy clubs have various stargazes and all night observing marathons. If you go out with such a group, you not only have security, but you also have the added benefit of being with knowledgeable people who can give help or advice, as needed. Many of these groups also have astronomical equipment (telescopes in various sizes, binoculars, cameras, tripods, timers, et cetera) that they loan to members for a nominal fee for several weeks, or possibly months for special projects. You can find the club nearest you by going to sites that list astronomical societies, such as Sky & Telescope, Astronomy, or the Astronomical League.

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What do I do?

Look for clear weather. The skies are especially clear just after a cold front has passed through. Excessive humidity can fog up your lenses. Excessive heat can cause atmospheric distortions.

Because astrophotos may not show clear boundary indications to film developing technicians, you may want to take an initial shot in daylight, and another daylight or indoor shot in the middle of the roll. This gives developers guidelines as to the length of each shot...even if the film appears to have a stretch of shots made with the lens cap on.

After selecting your special site, attach the cable release to the camera and attach the camera to either the tripod or to a "Scotch Mount." (In order to avoid image streaking, the camera must be equatorially mounted piggyback on a telescope with a clock drive, manually guided with an equatorial mount--"Scotch Mount," or must be limited to a maximum duration of about 25 seconds.)

After taking a daylight or indoor shot, set your shutter speed at "B," so that the shutter will stay open until you manually release the shutter by unscrewing the cable release set-screw. Adjust the film speed window (on the same dial--see illustration below) to show the ASA number of the film that is loaded into the camera, such as ASA 400. For night shots, the camera does not need to be "on." You will not be using "match-needle." Also, while home, attach your cable release to your camera. The cable release is the kind of essential item that you will find missing when you are 68 miles from home at the dark sky site, and everyone else is using theirs.

If you are so lucky as to have a bright comet to photograph, that will be an ideal simple subject. Constellation photos are also simple to do. They are useful as classroom study, or, when taken by students, can be incorporated into reports or science fair projects. The set-up procedures for this type of astrophotography will be the basis for all other astrophotography that you might do.

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CONSTELLATIONS

The constellation Scorpius, rising above a large thunderhead with a fork of lightning was taken with a 28 mm wide-angle lens for a 45 second exposure.  
The image has been cropped to feature the constellation without the extended vista.

Simple constellation shots can be enhanced by the inclusion of trees, unusual structures--man made or natural, groups of people, or unusual and decorative lights.

When you line up a constellation shot, see what added elements there could be in that shot... unless you want merely sky and stars. Don't just set up the tripod and pan the camera around...move the tripod to the area that will give you the most interesting shot from the best angle. A series of astrophotos is not necessarily taken from one spot, but may be taken from different areas of one locale, or from entirely different locales.

To get a good constellation shot, sight through the viewfinder until the constellation and any foreground enhancements are set as you would like to see the print. When you are satisfied with the setting, use the cable release to open the shutter without jarring or nudging the camera. If you have not used a cable release before, push down on the button at the end, and turn the set-screw just under it until it is moderately tight. This will keep the shutter open until you unscrew the set-screw to release the shutter. Practice on an unloaded camera to become familiar with it before you have to use it in the dark.

Bracket your exposures. Take at least three exposures of varying durations of the same subject in the same setting. Log your information. Later, you will be able to go over the photos or slides with the log as a guide as to which exposures got the best shot. There are variables that will affect the quality of your photos--streetlights, auto headlamps, moonlight, billboards, bug zappers--try to avoid areas where the quality of your shots will be affected by these variables, and take staggered (bracketed) exposures. You might try a 10-second exposure, a 15-second exposure, and a 25-second exposure. Log each, so you can later compare which was best. The next time you take photos, you may want to fine-tune your bracketed exposures around the best of those shots by adding or subtracting a few seconds.

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"DOT-STREAK" PHOTOGRAPHY

 

Orion photo illustrating dot-streak technique by EAAA member Charlie Strickland using a 55 mm lens--30 seconds for the dot; 2 minutes gap; 10 minutes for the streak.

The naked eye cannot discern star colors as well as the photographic plate which has had time to absorb light. Stellar colors are an indication of the age and intensity of stars. Reddish or orange stars are older and cooler stars, whereas the white or blue-white stars are younger and hotter stars. If you want to show star colors, one of the best methods is the dot-streak technique.

In order to take a dot-streak photo, you set up as you would for a simple constellation shot. Then, after you have begun your exposure and it has run for up to 20 seconds, you hold a dark piece of paper or some other opaque object in front of the lens for about a minute. After a minute, remove the object, being careful not to bump the camera or lens. The camera will resume the exposure. Let it run for several minutes--the longer it runs, the longer the colored streaks will be. Use the cable release to terminate the shot. You will end up with a "portrait" of a constellation, with colored star trails showing its path through the heavens.

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DEFOCUSING PHOTOGRAPHY

Again, set up for a simple constellation shot. After you have gotten about 20 seconds of exposure, very slowly and very carefully turn the camera lens (already set at infinity) a little bit at a time for a minute or longer. You will end up with artistic color smears that show the stars' ages.

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CIRCUMPOLAR PHOTOGRAPHY

You will need a slower film for this kind of shot--ASA 200 will do well. Find the North Star (Polaris), and center it in your camera viewfinder. Using the cable release, open the shutter and secure the cable release set-screw to keep the shutter open. Do this when you know that dawn is not a couple of hours away, and when the moon will not be washing out your shot. The length of the exposure will partly be determined by the amount of light interference probable where you are set up. After moonset or during New Moon would be a great time to experiment. Set up the shot and then....go read a book. Play a game of solitaire--play two! Take your time--anywhere from five minutes to several hours, but remember...the darker the site, the longer the exposure. Consequently, if you have the neighbor's bug zapper and streetlights nearby, you'd better limit exposures to less than a half-hour.

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PLANETARY MOTION PHOTOGRAPHY

Planetary motion shots follow the guidelines for constellation shots with the exception that in order to show motion, one must take a series of photos every evening or night, or every couple of days for a number of weeks. The background for each exposure should be the same--marking the spot where the tripod legs sat with spray paint will allow you to set up easily. If you are using a marker for your shot, such as a flagpole, church steeple, statue, or framing of trees or shrubbery, you should set the tripod at the same place in relation to those markers.

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SUN & MOON PHOTOGRAPHY

Both solar and lunar photography are generally too difficult for beginners. Complex formulae are often used to calculate exposure times, and even then you need to bracket. Special filters are often used--especially for solar shots. If you still want to take pictures of the sun, photograph a projected image of the sun. Students should avoid solar photography entirely unless an adult is providing a projected image for them to photograph with their backs to the sun.

Lunar eclipse photography is completely different. Due to atmospheric conditions, you do not know how dark the eclipse will be...so, you bracket with a wide range of exposure times.

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"SCOTCH MOUNT" PHOTOGRAPHY

The directions for the construction and use of the "Scotch Mount" are on the EAAA web page, The Scotch (Haig) Mount.  This method of photography allows you to get longer exposure time for your astrophotos without having to invest in a clock drive system for a telescope that is clock-drive compatible.

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