# Astrophotography without a telescope?



## explody pup (Dec 28, 2006)

Today's Astronomy Photo of the Day reminded me of something I've been wondering for a while.  Is it possible to capture a very dim (to the naked eye) object in the night sky such as the Andromeda Galaxy?  It's certainly large enough to fill a frame even without the use of a telescope.  Is the Earth's rotation too fast to get a sharp image?  Would a high ISO, say 1600, help without destroying clarity?  What about photographing our own galaxy?


----------



## Big Mike (Dec 28, 2006)

I don't know much (or anything) about astrophotography...but I have read that most digital cameras have an infrared filter that makes it hard to photography the stars etc.  Canon made a special release of the 20D*a*...which had the infrared filter removed or modified to allow for astrophotography.


----------



## kwjones (Dec 28, 2006)

It can be done, they do it with film camera's.  http://www.astrophotography.com/cameras.htm

Unless you have a tripod that has built in automatic tracking of the object you want to photograph, your best bet is to take more, shorter exposures and combining them them in a software program like Astrostack.  If you has a telesope that can auto track an object, there are a few companies like www.scopetronix.com that make a device that will allow your camera to piggy back on the telescope.


----------



## astrostu (Dec 28, 2006)

Photographing a bright object is easy.  However, photographing a faint object is much more difficult because of Earth's rotation.  The sky rotates 360° in 24 hrs, which boils down to 1/4° (15 arcmin) per minute.  This probably doesn't mean much to you, but it's the same as saying that if you set up your camera to point directly at a star, over the course of 1 minute, that star will move 1/2 the width of the full moon.  If you are trying to image something like M31 (Andromeda Galaxy), then you'll probably have a lens on with a ~6° field of view.  If you're using - for example - a Canon 350D that's about 3500 px across, then the galaxy would move by approximately 150 pixels over the course of a 1-minute exposure.  Andromeda is very bright, but its light is spread across an _area_ over 40 times the size of the full moon which effectively decreases its brightness by a factor of 10,000; so a short enough shot without a tracking mount will result in black.

So, without a mount that tracks with Earth's rotation, you are limited to very bright objects (e.g., Moon, Galilean Satellite positions around Jupiter, very bright comets (rare)) or to objects where you _want_ it to be blurred across the frame (like star trails).  But if you have a mount that tracks, then you are only limited by the size of your lens (aperture and length).

Thus, to directly answer the thread's title:  Yes, you can do astrophotography without a telescope.  A telescope just acts to collect much more light (light collection goes as area of the lens/mirror) than a camera lens, and they usually have built-in clock drives to compensate for Earth's motion.


----------



## THORHAMMER (Dec 28, 2006)

it would be neat to have a large telescope and tracker attached in the back your pickup, drive to a very high spot above the smog and closer to the sky. Use a laptop inside to control the shot. 

better yet, the huge observatory(s) , they should let people hook up their cameras to them....rent out 20 minute periods of time or something...at night


----------

