|Sunspot Activity 30-July-02
There has been a considerable amount of solar activity of late, as shown by the above groupings. This image was captured
using an 8" Mak-Newt and Kendrick/Baader full aperture solar filter, with a Nikon CP995 digital camera direct-coupled to a
17mm Nagler eyepiece. Of 150 images taken in the 10 minutes series from 17:00hrs EDT, there were 7 or 8 "keepers", and
the rest were throw-aways. The low angle of elevation and a very hot, unstable atmosphere minimized the "catch", but
I prefer to extract the "Baader Blues" that the raw images are endowed with, in favor of more natural coloring. To that end, I
split the original image into RGB +l components, boost the R and G channels, tweak the luminence, and reduce the level of
the B channel. While this would also work with a straight B/W image, shooting in B/W mode tends to yield a flatter
appearance than the full color mode, which seems to better translate the topographical features. In any event, the
advantage of increased resolution of the raw B/W mode images seems to become a moot point with judicious processing.
The image was further enhanced using channel re-assignment, as described in the following panel.
Processing included mild contrast stretching and 25 iterations of Richardson-Lucy deconvolution using an 11x11 Gaussian
blur, courtesy of ImagesPlus software. Final tweaks were performed with Adobe PhotoShop.
The above close-up was taken with a 9mm Nagler eyepiece in place of the 17mm Nagler. The camera was at maximum
optical zoom of f5.1 (31mm fl) in each image. Note the granulation and characteristic darkening near the limbs in each
image, as well as light bridges and fibril structure in the spots, spanning from the penumbra to the darker central umbra
Reds and Blues occupy either end of the spectrum captured by most consumer grade digital cameras and tend to have
lower resolution than the Green channel, as most digicams allocate twice as many G pixels than R or B. As an experiment
to increase image resolution, this image and the one at the top of the page were processed using composite luminence in
place of the lower-res B channel and a duplicate of the higher-res G component was converted and used to replace the
luminence channel. Using some additional suggestions from a film-based astro-imaging guru friend (thanks Les L!), I was
able to wring even more detail from each (also thanks to solar imaging guru Gordon G for his guidance!). The resulting
images preserve most of the feature nuances captured within the original spectral range, while enhancing definition of
features such as granulation, penumbral fibrils, light bridging, and limb darkening being more prominently displayed.
What do you think...?
(click on the below link to check out a raw original... yeouch!)
|Solar image using re-assigned Blue and luminence channels