Monthly Archives September 2012

Autoguided versus Unguided Long Exposure Astrophotography

I wanted to demonstrate, visually, the difference between an unguided versus a guided exposure.  When taking photographs of deep sky objects, stars can move as fast as 500 kilometers per second or as slowly as a few kilometers per second.  This makes taking nice round images of stars a bit difficult.  To counter the movement of the stars, an Autoguider is needed, which is an additional camera sensor (either on the camera that is taking the photo or an independent camera strictly used for guiding).  In short, an Autoguider is a sensor that constantly makes short exposures to take a picture of a star and put it in memory.  A software program calculates the stars position, monitors its movement, and calculates the necessary correction to bring the star back to its original location.  The software then issues commands to the telescopes drive system to make the correction.  Since the sky is constantly moving, the telescope mount is able to move with the sky and object you are photographing looks like it is frozen in time.

Below, you will find an Autoguided, 4 minute exposure of the Andromeda Galaxy.

Below, you will find an Unguided, 90 second exposure of the Andromeda Galaxy

If you notice the difference in the stars from guided and the unguided exposures, you will see that the stars look smudged in the unguided exposure and the stars look like round balls of light in the guided exposure...

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Testing Out the SBIG ST-2000XM CCD on M31

ST-2000XM CCD
15 Minute Luminance Exposure

The last few nights have been crystal clear, which gave me a great opportunity to test out my latest purchase (used of course).  I bought a 10 year old SBIG ST-2000xm, which is a  CCD (“Charged Coupled Device”) camera and is strictly used for Astrophotography.  The image above is a 15 minute (L) exposure.  I have not learned the art of stacking multiple images yet but the theory behind image stacking is the more images you stack, the more you increase the signal and decrease the noise.  There is so much more detail that I am lacking as just taking a single exposure in Lumiance, I am missing the Red, Green, and Blue (RGB) color spectrum.

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The Man in the Moon Graces the Night Sky

The desert sky in Rancho Mirage, California creates a beautiful backdrop to photograph the Moon and tonight, the Moon was hiding until it peaked over the clouds, creating cool effects.  The way the clouds were dispersed in the sky, it gave the illusion that the Man in the Moon was winking over the clouds.

The Man in the Moon

The Man in the Moon

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Deer Lick Galaxy Group NGC 7331

Deer Lick Galaxy Group NGC7331

Deer Lick Galaxy Group NGC7331

I was out on August 28, 2012 shooting various objects in the night sky when I found out that I could view the Deer Lick Galaxy Group from my backyard.  At a mere 49 million lightyears away, this is the furthest deep sky object I have photographed so far.  This is not the greatest shot but you can see the largest Galaxy in the group.  The exposure was not long enough to capture light from the other Galaxies so I will have to revisit this one.

The Deer Lick Galaxy Group was coined by Tom Lorenzin (author of “1000+ The Amateur Astronomers’ Field Guide to Deep Sky Observing”) to honor Deer Lick Gap in the mountains of North Carolina, from which he had especially fine views of the galaxy group.

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