|Solar H-a maging on a shoestring
Coronado PST and ToUcam
The image to the right is the result of
multi-stage processing, using the
"direct-coupled" image seen above as the
The luminance channel is isloated from
the B/W image (which is actually in RGB
format), and processed using different
different paths for the surface, limbs, and
proms. The grayscale results are then
converted into RGB, colorized, and
combined (more details can be found in
my "In Search of Solar Nirvana" section) or
"Ha Solar Imaging Techniques" PDF.
I'll "flesh out" this page as time permits...
but in the meantime am satisfied
non-invasive imaging with a PST is not
only do-able, but can provide satisfying
Processing info: Images gathered and
converted using K3CCDTools, processed
with ImagesPlus, and assmbled/polished
in Adobe PhotoShop CS.
I finally got the chance to gather a few images with the new Coronado PST H-a solarscope, and will pad out this section as time
permits, but wanted to get these first images posted. In an effort to explore H-a imaging on a modest budget, a ToUcam webcam
was used in lieu of a pricier, more complex device (such as a digicam, DSLR, or dedicated astro-CCD).
The first order of business was the attachment of the ToUcam to the PST. Unfortunately, the webcam eyepiece adapter positions
the ToUcam a few mm outside of focus. Two simple, non-invasive work-arounds were tried... each with success.
The first passes were made using the Coronado CEMAX Barlow lens as a relay. It can be unscrewed from the Barlow, and
threaded into the ToUcam adapter (standard-size filter threads are used). The image scale is a tad large though, capturing a
quadrant-sized chunk of the sun (below left, reduced from 640x480 for display here). Wanting to capture at a smaller image scale
and lacking only a few mm of back-focus, I decided to see if a modified ToUcam adapter could be used. Okay, I didn't get out the
tools to resize my adapter just yet, but used the next best thing... a test-bed prototype (translation: duct taped the ToUcam to the
eyepiece opening! :o) The resulting image scale was much more suited to full-disk work, alowing about 2/3 of the disk to be
captured (below right, in reduced format).
Coronado CEMAX Barlow lens/relay Direct-coupled to PST EP
The ToUcam provided enough dynamic range so as to capture both proms and surface detail at one exposure setting, and a
single image was chosen as the basis for making a final composite, (disk surface/hairy limbs/proms). Individual frames from the
AVI (video) varied considerably, so no stacking was performed. This results in less blurring of detail, but the downside is a noisier
appearing image, but the final image size can be reduced to help mask the roughness.
The ToUcam was used in Black/White mode, allowing focus to be more readily discernable. Images were captured in 640x480