Astronomy

How to Photograph Objects Visible in a Telescope



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Have you ever looked through one of those astronomy magazines at a newsstand and wondered how those guys took those wonderful looking pictures? Did you assume that they all came from the Hubble Telescope? They didn't. For over a hundred years now astronomers have been taking photographs of objects in the sky right here from the Planet Earth.

Quite a few very good photographs can be taken from moderate sized telescopes which amateur astronomers all over the world have in their homes. Granted, you will not see photographs of any quality coming from people using the piece of junk telescope that they bought from the department store. The equipment needed is just a bit more sophisticated than that.

In general what you need are the following items:

1. A decent telescope that allows you to connect a camera to the end or over an eyepiece

2. A connecting ring from the camera to a metal camera tube or to the end of the scope

3. A camera tube that connects to the scope and covers an eyepiece (for taking magnified shots of an object)

4. A decent SLR camera for taking photographs of various exposure times

5. Film (100 speed for bright objects and high speed film for dim ones)

6. A locking camera release cable (a long cable that allows you to lock the shutter open for extended periods of time)

7. A good location to shoot from

Starting from the above list, let's discuss each item in detail.

Decent telescopes are widely abundant. My preference are the schmidt cassegrain type scopes but you can get good pictures with many types of scopes. The keys, however, to good photographs are a stable equitorial mount (to minimize vibrations) and a good tracking system on the scope (to minimize errors and corrections). Tracking and errors are not really an issue for objects within our solar system such as the sun, moon, most planets, most comets, etc... But for galaxies, nebulae and other dim objects tracking is critical to good success taking a picture.

Connecting rings and photo tubes are available from Orion on the net or from various providers advertising in astronomy magazines. SLR cameras for astronomy are a little more difficult to come by. There are people that still make these cameras but some of the older ones are better for astronomy. Used camera supply stores often will have an old model SLR that does not require a battery for holding the shutter open. This is preferable. It would really suck to be in the 30th minute of a 60 minute exposure and have your battery die and the shutter close and you not even be aware that either has happened. This wont happen with a mechanical SLR camera with a locking cable release.

For long exposure shots you may need exposure times of up to 60-90 minutes to get a full detailed picture of an extremely dim object. Black and white film often produces the best detail in these kinds of shots. Color film often turns the object red over long exposures even if that is not the true color of the object. Black and white film will not do so. The red color tends to bleed all over the picture and wash out a great deal of the detail. Color works just fine for most other objects in the sky.

Location is often a major issue in taking long exposure pictures. Light pollution from nearby major cities will show up as a green shadow on your pictures from the direction of the town. It is best to shoot from remote locations when possible. Of course, those remote locations are not as comfortable as taking a picture from your own driveway or back yard.

In today's digital age there are newer and better options for photography. Digital SLR cameras may be able to photograph through a telescope if you can find a docking ring capable of it. CCD devices are available which are basically digital cameras made for astronomy. These hook to a computer and allow you to enhance and clean up your images. They can take pictures in far less time than with a camera.

Error correction is a major and critical issue with film photography with long term exposures through a scope. There are devices available to help with correcting a telescopes tracking but require the user (you) to be at the eyepiece correcting the scope manually throughout the exposure. It takes some serious diligence to sit at an eyepiece over an hour correcting the scope over and over again. Unfortunately, even in todays computer age, scopes are not perfect and will not correct themselves accurately enough to keep an image directly within the exact same spot of the eyepiece for a long term photo. A ccd device can correct for you but these cost additional money.

Photography through telescopes is a fun and rewarding hobby but it takes some money and some research. It also takes some trial and error. Finding exposure times for getting good pictures is a chore. Some objects are too bright and will require you to slow down the picture and take less exposure time. Dimmer objects require more exposure time. The speed of the film makes a difference too. You can go through a lot of film to get one or two good shots. Planets tend to take exposure times of 2-4 seconds. Less for brighter ones. The moon can be shot at the highest exposure speed (lowest time open). However, magnification also affects the exposure time needed. Higher magnification requires higher exposure time.

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