Sergei Golyshev (AFK during workdays)
Laboratorium Solaris: I don't know...
for sure, but it seems that I have got some extra grip on solar imaging :)
I was very pleased with the contrast of the chromosphere images produced by PST-DMK23 combo. But... While the proms were visible through the eyepiece, they were hardly (or not at all) detectable on the images. All attempts to drag them out in processing resulted in appearance of otherwise undetectable defects including residual shot noise and smearing/charge leaks, not to mention the artificial feel of the images. What to do?
The obvious feature of Coronado PST is the "sweet spot" of a size about 1 mm in terms of real image size. It is located in the middle of the FoV and becomes overexposed first.
I have thought of it as a problem. But this time I have noticed that if the prominence falls into the sweet spot, it pops out.
The second point is that PST works at its full power at EFL of 800 mm. So here comes obvious conclusion: if I want prominence, I need to place it into the sweet spot.
By using focal extender/Barlow lens the size of the sweet spot on imaging sensor becomes larger, and the image becomes more uniformly illuminated.
The resulting image show both increased contrast of "surface" details and proms on the limb also stand out more prominently :)
Next new step was to apply wavelet sharpening, which I had kept disregarded for a while. Wavelets were applied using AstraImage software. Some practice is required and maybe more frames are needed for better wavelet processing, but wavelets really add to the resulting contrast.
Even more extra contrast can be obtained by high-pass filtering, but it comes with the cost of finest low-contrast details. Here the victim is the long singular spicule in the lower left corner of the image. Now it is barely seen if the image is viewed in darkened room. So high-pass filtering perhaps should be omitted.
16.03.2015, 09:29:23 GMT+4.
TIS DMK23U274 via 2x Barlow lens on Corondo PST.
Stacked 20% of 1200 frames acquired in 1 min. Flatfield was acquired by defocussing the image with the same camera setting.
Stacking and correction in Autostakkert!2. Resulting image was deconvolved (Cauchy type, 0,3 pixels, 9 iterations) and wavelet-treated in AstraImage PRO 3.0. High-pass filtering was done in Photoshop.
Laboratorium Solaris: I don't know...
for sure, but it seems that I have got some extra grip on solar imaging :)
I was very pleased with the contrast of the chromosphere images produced by PST-DMK23 combo. But... While the proms were visible through the eyepiece, they were hardly (or not at all) detectable on the images. All attempts to drag them out in processing resulted in appearance of otherwise undetectable defects including residual shot noise and smearing/charge leaks, not to mention the artificial feel of the images. What to do?
The obvious feature of Coronado PST is the "sweet spot" of a size about 1 mm in terms of real image size. It is located in the middle of the FoV and becomes overexposed first.
I have thought of it as a problem. But this time I have noticed that if the prominence falls into the sweet spot, it pops out.
The second point is that PST works at its full power at EFL of 800 mm. So here comes obvious conclusion: if I want prominence, I need to place it into the sweet spot.
By using focal extender/Barlow lens the size of the sweet spot on imaging sensor becomes larger, and the image becomes more uniformly illuminated.
The resulting image show both increased contrast of "surface" details and proms on the limb also stand out more prominently :)
Next new step was to apply wavelet sharpening, which I had kept disregarded for a while. Wavelets were applied using AstraImage software. Some practice is required and maybe more frames are needed for better wavelet processing, but wavelets really add to the resulting contrast.
Even more extra contrast can be obtained by high-pass filtering, but it comes with the cost of finest low-contrast details. Here the victim is the long singular spicule in the lower left corner of the image. Now it is barely seen if the image is viewed in darkened room. So high-pass filtering perhaps should be omitted.
16.03.2015, 09:29:23 GMT+4.
TIS DMK23U274 via 2x Barlow lens on Corondo PST.
Stacked 20% of 1200 frames acquired in 1 min. Flatfield was acquired by defocussing the image with the same camera setting.
Stacking and correction in Autostakkert!2. Resulting image was deconvolved (Cauchy type, 0,3 pixels, 9 iterations) and wavelet-treated in AstraImage PRO 3.0. High-pass filtering was done in Photoshop.