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Showing posts from February, 2012

Why a GEM for astrophotography?

*The GEM*
During a past on air hangout I spoke a bit about photographing Deep Space Objects and the equipment that I use to take those photos.  One of the things that was mentioned is that I use a GEM (German Equatorial Mount) on a very heavy tripod.  The GEM or Equatorial Mount is a really fancy way of saying it’s a tripod head that aligns the camera lens (either regular lens or telescope) with the earth’s axis.  I didn’t really explain in great detail why this is a must when you are trying to do very long exposures or “Stack” several shorter exposures. Below is a photograph I took from the back deck of my house.  I had my camera mounted on a “Regular” camera tripod.  The region of the night sky may be recognizable by many people, it is the Orion Constellation area.  This photograph was achieved by taking several 13 second exposures (@24mm) and “Stacking” them using a free program called Deep Sky Stacker.  The total exposure on the image is just under 6 mins. Since the earth moves,…

Deep space photography is not as hard as you think it is!

Deep space photography is not as hard as you think it is!

Yes, to get some spectacular images of galaxies and nebula you do need a good telescope (or lens) and GEM (german equatorial mount) so that you can take longer exposures without elongating the stars and get a bit closer to the object you wish to photograph.

There are however several deep space objects that you can photograph without using specialized equipment.

In 1771 Charles Messier was kind enough to amass a list of 45 objects (the list now contains 110) in space that can be seen quite easily with the aid of binoculars or a small telescope.

Many of these objects can even be photographed using high ISO and the maximum length of exposure your chosen lens and camera will allow (without getting star trails). More on that here

The photograph on this page is a good example of what I'm talking about.

The photograph was originally intended to be a test of my new camera and its high ISO performance, but when I looked at …

The Power of Stacking Images

This was taken on an entry level DSLR with a 10 mp CCD sensor. Which is far from a great camera by today's standards.
The lens used was a very old kit lens from my old Pentax ME-F a 35mm 1.7
I was basically testing the lens performance at imaging stars, the night was not very good for astrophotography either, there was poor visibility and periodic clouds.
In the near future I will be doing another "stacking" of images with a bit longer (80mm) focal length using just my dslr, a regular lens, and a tripod.  I will make another post with the resulting image to show the power of stacking even more.
Settings used Exposure - 15 seconds Iso - 800 Lens - f 2.8 2 second delay timer to minimize shake
I took 5 images and stacked them using a free program called Deep Sky Stacker and did some further processing in Photoshop.

I've also labelled the more known stars and some areas that contain some of the better known deep space objects. You can even see (faintly) the Orion nebula…

Why Subtract Dark Frames?

I’ve seen many people doing night time / astrophotography I thought it would be beneficial if I did a really quick post on Dark Frame Subtraction.

Below are two images, one shows a section of a photograph before dark frame subtraction and the other shows after. (note the red dot in the before image)

First I’ll explain what a Dark Frame is for those who do not know. A dark frame is simply a photograph taken in complete darkness that is designed to capture the “Bad Pixels” on your camera sensor. When you take long exposures your camera tends to get “Hot Pixels” which show up in your image (sometimes as red dots). The intent of Dark Frame Subtraction is to reduce the amount of noise that is produced by your camera. 

Many of today’s cameras have “High ISO” or “Long Exposure” noise reduction. Essentially this does the exact same thing that I’ve done in post processing for this example. To explain this a little more, when you use these settings your camera will take the “Light Frame” (image th…