The Sun in Hydrogen Alpha, July 31, 2004

All Images Copyright Steve Cannistra

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This is my first solar image through the Coronado Personal Solar Telescope (PST), using the Canon 10D with an afocal camera adapter from Orion Telescope.  This scope permits wonderful views of both prominences and surface detail, through the use of an adjustable tuner.  Note that the Coronado PST is specially made for safe solar observing.  You should NEVER use a regular telescope for this purpose, unless you have the appropriate kind of solar filter
(note that the common type of Ha filter used for deep sky astrophotography CANNOT be used for solar observing).   Failure to use the proper equipment for solar viewing can lead to permanent eye damage.

Description:  There is a large solar prominence in the upper left that is associated with two large solar spots known as 0682, which are now on the far side of the sun (no longer visible).   Visually, I detected small prominences on the other limb as well, although I evidently did not "catch" them at the right point in my tuner adjustment.  A sunspot is clearly visible, located just upper right of center, and there are a few solar filaments seen on the sun's surface (the linear red streaks).  Filaments are the same structures as prominences, except that they are seen against the background of the Sun's chromosphere and appear dark because they absorb the background light.  When they swing around to the edge, they appear as fiery plumes shooting into space (and are then called prominences).  Here is a good website for those interested in learning more about the Sun.

Photographic Details:

Date:  July 31, 2004
Coronado PST.
Mount:  Portable motorized equatorial mount from Orion (light weight, relatively inexpensive, and easy to set up).
Camera:  Canon 10D, in afocal configuration, using a Meade 26mm Plossel eyepiece and the Canon 24-85mm zoom lens set to about 40mm focal length.  I focused the PST using a homemade Hartman mask and focused the camera to infinity, tweaking the focus by taking several shots and adjusting as necessary.  For some early test shots, I had a UV filter in place to protect the camera lens, but soon found out that this caused a Newton's Ring effect that completely disappeared when I removed this filter.

Exposures:  A total of 100 exposures were taken in Raw mode, at 1/125 second f5.6 for surface detail, and at 1/60 second f5.6 for prominences.  I adjusted the tuner on the PST intermittently throughout the exposures in order to capture surface detail as well as prominences (but not in the same image).  From these 100 shots, I eventually chose one image for surface detail, and one image for prominence detail (see below).
Conditions:  Temperature 80 degrees F; average seeing; humid; many passing clouds.
Post-processing:  I used the technique described on Paul Hyndman's website, as well as in the July 2004 issue of Sky and Telescope.  The basic idea is to select two images, one that is properly exposed for surface detail, and the other for prominence detail.  The grayscale red channel is used for all processing steps (there is very little leakage of signal into the green and blue channels in the 10D).  The red channel is enhanced using curves and Lucy-Richardson deconvolution in ImagesPlus, and the two images (prominence and surface) are recombined in Photoshop.   The Channel Mixer tool (Photoshop layers) or equivalent is used to produce a false color image as shown above.

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