[APML] Sunspot Picture

[Jerry Lodriguss <jerry@astropix.com>]

Hi yall,

I've posted a shot of the two large sunspots that are currently on the sun.

It's at: http://www.astropix.com/HTML/SHOWCASE/SUNSPOTS.HTM

Although it was taken with a Nikon D1h digital camera, the image processing 
may be of interest to the few film photographers left alive on this list. <G>

A series of approximately 300 images were taken manually one after another 
with the camera in anti-mirror shock mode and triggered with the self-timer 
to reduce vibrations.

The raw images were then imported into Photoshop 7 with the Adobe Camera 
Raw plug-in and were exposure adjusted, contrast increased and sharpened in 
the ACR module. Because the images were low noise from having been shot at 
ISO 200, noise reduction in the ACR module was set to zero.

All of the images were then opened in Photoshop and enlarged to 200 percent 
and examined for sharpness and the best image was selected.

The image was further adjusted in Photoshop for tonality, and sharpened 
with an unsharp mask of 100 percent, 0.5 pixels and 0 levels. Another 
unsharp mask of 100 percent, 2 pixels and 2 levels was applied. False color 
was added with a layer in the darken blending mode.

Shooting 300 images was a method of hoping to luck out and get one with a 
moment of especially good seeing. This technique goes back many decades and 
has recently been advanced greatly with web cams for planetary photography 
where videos are shot at a high frame rate and specially designed software 
selects the sharpest frames and stacks them together to create a low-noise 
image.

In the case of a web cam, the images are relatively low resolution in terms 
of the total number of pixels, but the resolution of the seeing is matched 
to the image size at the focal plane producing excellent results. In this 
case a larger file size of approximately 3.5 megabytes was produced by the 
Nikon digital camera.

Jerry


Photoshop for Astrophotographers - http://www.astropix.com/PFA/PFA.HTM











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