Tuesday, September 03, 2013

Astrophotography 101

Cassiopeia, showing the double cluster and M31
ISO 1600, f5.6, 18mm, 30secs, Fog filter

The Great Square of Pegasus with M31
ISO 1600, f5.6, 18mm, 25secs, Fog filter
The Plough, clearly showing Alcor and Mizar
ISO 1600, f5.6, 38mm, 30secs, Fog filter
So as we approach Autumn the skies are most certainly getting darker and so I took myself out with the camera to see what I could get.

Over the summer months I have been reading up on and getting to grips with my camera in a more Astrophotography mode. Like most things of this nature it can become a mine field and you soon find yourself over-whelmed with information. But, with a little perseverance, you can get there.

A computer with decent photo processing software is essential in getting some decent results. GIMP is my tool of choice and is free.

My tips so far are:
* Use a tripod
* Take a "dark" frame for later use
* Use highest ISO possible with a wide aperture (low f-number)
* No more than 30 second exposure
* Turn OFF Noise Reduction
* Normal image settings with auto White Balance

When processing the images in GIMP I used the dark frame and the difference layer setting. This will remove any "noise" produced by the camera and any rogue pixels that may look like stars if a dark frame were not used.

Next I adjust each colour channel (Red, Green, Blue - in that order). Move the mid-slider towards the left-hand side (white point) until the image shows the "next" colour. So if adjusting red, this would show green and adjusting green would be blue. Close levels window.

You may wish to adjust the mid-slider (re-open the levels window) to find a better brightness. Make further adjustments with the Curves tool. Adjust the contrast and brightness if required.

One little trick I did pick up is the use of a Fog filter (I use a Foggy A from Kenko). This will make the brighter stars stand out from the background.


No comments:

Post a Comment