Sun in H-Alpha
The following images of the Sun were taken with my Coronado Personal Solar Telescope (PST) using a Toucam Pro webcam. See also my CCD Solar images taken with a Starlight Xpress SXV-H9 CCD camera.
The PST and webcam setup is shown below.
| In order for the Philips Toucam Pro webcam to reach focus on the Coronado PST, a short webcam adapter is required. This is shown here: |
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When the webcam is inserted into the PST eyepiece tube it lies flush as shown here: |
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| This picture shows the Coronado PST mounted on the Celestron Ultima 9.25 fork. |
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I've found that the white plastic casing of the webcam is not totally opaque and degrades image contrast. Aluminium foil solves this and also helps keep the heat down. |
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The image processing steps for the solar images are detailed at the bottom of this page.
| 29th April 2006 |
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3rd May 2006 |
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6th May 2006 |
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The disc is normally exposed at 1/1000 sec, with the gain at about midway
slider. AVI files are recorded using 5 frames per second. The frames are stacked
in Registax 3 and the final stack saved as a 16bit RGB TIF file (no wavelet
processing). For the proms I use 1/250 sec, gain also about midway slider and
also 5 frames per second. The frames are stacked in Registax and saved to a
16bit RGB TIF file (also no wavelet processing).
Each stack is then opened in PaintShop Pro and the "Image/Split Channel/Split to
RGB" menu option is used to extract separate RGB frames. The green and blue are
discarded and only the red channel is saved. The red channels are opened in
Photoshop CS. For the disc image the levels are slightly adjusted to use as much
dynamic range as possible. The proms levels are adjusted to show as much of the
proms as possible with the disc being overexposed. For both images the
"Filter/Video/De-Interlace/Even Fields" is then used to remove the horizontal
lines. The "Filter/Sharpen/Unsharp Mask" is then used with "Amount=200%",
"Radius=1", "Threshold=0" to sharpen up the images and bring out some detail.
Within Photoshop CS the composite is constructed as follows. The disc image is
selected and the "Feather" tool used to select the disc only - click outside the
limb and the select the inverse. Copy the selection and paste over the proms
image and nudge it so that it overlaps as best you can. Once you are happy
select "Image/Mode/RGB Color" to allow you play with colours. Now select
"Image/Adjustments/Curves". For the RED channel move the curve up, for the GREEN
channel move the curve down, for the BLUE channel move the curve further down.
You can play with these until you are happy with the colour then save it in
whatever format you want.