Astronomy

Information about Astrophotography



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One of the things that an amateur astronomer begins to think about soon after they begin seeing some of the interesting objects in the night sky is that they wish they could capture this on film. Of course, astronomers have been photographing the objects in the sky for quite some time. Astronomy magazines show some of the most amazing sights week in and week out.

So how can one do this from home? Well first of all you need the right equipment. And second you will need to live with some disappointment. Taking some of those full color pictures of amazing nebulae and galaxies takes some serious equipment and skill and a great deal of money. But you can take some interesting and even some high quality photos from your backyard with a small telescope.

First of all you have to decide what you are going to capture the pictures on. It has been increasingly popular for people to use CCD technology to take digital pictures. However people have been using 35 mm film to photograph objects through telescopes for far longer.

To use a 35 mm camera you are going to need one that is an SLR (slow motion reflex) camera. This is essential. Objects in the telescope tend to be dimmer than objects you would photograph with a camera in daylight. You will need to be able to lock the lens open for a longer length of time than you would for a normal picture.

One thing you will notice is that photographs of longer than a few minutes length tend to show the stars as just streaks of light on the picture. This is because the sky is moving but at a speed that you don't even notice it. Film, however, will notice it and capture it. In order to keep the scope moving with the night sky to keep the object centered in the camera long enough to capture it you will need to be using a scope that has an equatorial mount and a tracking motor. Almost every refractor, reflector and schmidt-cassegrain telescope will have an equatorial mount. Dobson telescopes will not. Most that come with an equatorial mount will at least offer you the option of getting a tracking motor on it.

Pictures of brighter objects, such as the moon will tend to require exposure times of less than one second. Planets will require exposures of two to ten seconds depending upon the planet and the magnification you are attempting. In general results will improve by using a lower magnification eyepiece although the object will be far smaller. Clarity will be far better though.

Nebulae and other dim objects require very long exposure times. For these types of pictures tracking motors alone will not correct the telescope enough to keep the object centered. You will have to correct the telescope either manually or by using a CCD device to keep an object centered. Some of these photographs can be an hour or more in length of exposure time.

One of the benefits of using CCD is that you can immediately see the results of your work. You can also take pictures in far less time and delete pictures that didn't come out well without spending a lot of time and money on wasted photographs.
However, these cameras tend to be rather expensive.

The sun can also be photographed. There are mirror filters that can be placed on the end of a telescope which allow you to see sunspots and photograph them through a telescope. More expensive (extremely expensive) hydrogen filters will allow an astronomer to photograph solar flares and surface activity of the sun.

In general the items that you will need for basic backyard astro-photography are:

A telescope
Equatorial Mount and tracking motor
a 35 mm SLR camera (or ccd)
A docking ring (to connect the camera to a tube that connects to the telescope)
a docking tube (that connects to the telescope from the camera and will fit over an eyepiece or connect directly to the rear of the telescope to make the scope itself act like a big telephoto lens)
A manual lock for your SLR camera to lock the lens open for long exposures

Most of these items are not prohibitively expensive. You can take good photographs of the inner planets (Jupiter and Saturn will prove to be the best objects in photographs for various reasons. You will be disappointed in any of the other planets appearance in film or at the eyepiece). You can take some amazing photos of the moon and the sun (using an appropriate solar filter). With the proper equipment you can even take some awesome pictures of certain bright nebulae.

From my driveway in a major urban area I took pictures of the planets and the Orion Nebula which came out extremely well on film. In general black and white film will show the greatest contrast but unless you do your own developing it is tough to get anyone else to develop black and white. Color, however, has certain drawbacks in long exposure photography. Colors tend to blend into red. Objects that you have exposed tend to turn red. That may (probably isn't) the true color of the object. The reason for this is complicated but in any event it does often result in a bright and colorful object on film. Black and white eliminates this issue but, of course, shows no color at all. Many of the photos you see in astronomy magazines are really composite images of the object which tend to show a more true color.

If you are serious about photography through your telescope join a local astronomy club. Chances are you will find other members who can recommend what items to buy and perhaps can lend you access to objects that are too expensive to afford for personal use. Some clubs in my area loaned out hydrogen filters for solar pictures to members and these filters are often way too expensive for most amateurs to purchase.





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