Using the good old 150/750 tube, with a ND3.8 film in front, I obtained the following frames.
For reference, a Lunt CaK image, colorized and mono
And the infrared cwl 850nm, fwhm 20nm filter showing the active regions






ASI 178MM (cooled), IR850nm 20nm fwhm, Skywatcher 72/420 ED-APO, ND5, mountpusher, EQ3-mod — I believe this image shows the Calcium Triplet
For comparison, here’s the Baader CaK 5nm image (tovább…)
As you know, due to various reasons, lately I’ve been doing solar imaging almost exclusively, focusing on full disk observations. Of the many filters I have turned towards the Sun — some dedicated solar filters, some more in a hacker spirit –, the Calcium K wavelength is one of my favorites, obviously. Now that Baader started selling its generation ii CaK filter, I figured I’d test it against itself, the first generation, and against Lunt’s Calcium module.
As you also know, I record images as a hobby, without any specific scientific goal, I just like the rigor and if some aesthetics can arise from it, in the form of nice solar disk images in this case.
TLDR0: not much difference, but still.
TLDR1: if doing full disk, if you have the old CaK and like it — keep it and your setup the way it is, the new filter is nice, the profile is standard, but overall, doesn’t show anything new nor better than the old one. Both are that good. Obviously not as good as Lunt’s CaK, but they are a fair competition, given the price range.
TLDR2: if you have the Venus U filter, do use it. It’s not as good for the Sun’s active regions as the CaK, but still pretty good. Also, give the dark blue a chance. Or basically any filter you own.
TLDR3: for Venus, the new filter may yield better images, due to it letting through about two times more light (half the expo time). I like very much the CaK images I obtained of Venus, in the 2020 epic season.
Venus, on 2020-04-05, using Baader’s CaK (gen1), as a false bi-color image with a green filter, mapped to cyan and orange respectively, with a N150/750 tube.
EQ3-mod, mountpusher, Sharpstar 60/330 ED-APO, Lunt CaK B600 LS6CAKMDS2, ASI 178MM (cooled)
EQ3-mod, mountpusher, Lunt LS60T Ha B600, ASI 178MM (cooled)
EQ3-mod, mountpusher, Sharpstar 60/330 ED-APO, Lunt CaK B600 LS6CAKMDS2, ASI 178MM (cooled)
EQ3-mod, mountpusher, Lunt LS60T Ha B600, ASI 178MM (cooled)
EQ3-mod, mountpusher, Sharpstar 60/330 ED-APO, Lunt CaK B600 LS6CAKMDS2, ASI 178MM (cooled)
EQ3-mod, mountpusher, Lunt LS60T Ha B600, ASI 178MM (cooled)
EQ3-mod, mountpusher, Lunt LS60T Ha B600, ASI 178MM (cooled)
EQ3-mod, mountpusher, Baader Astrosolar ND3.8 Film, TS-Optics 76/342 TS76EDPH, Baader Solar Continuum 7.5 nm 1.25″, ASI 178MM (cooled)
EQ3-mod, mountpusher, Baader Astrosolar ND3.8 Film, TS-Optics 76/342 TS76EDPH, Baader Venus U filter, ASI 178MM (cooled)
EQ3-mod, mountpusher, Sharpstar 60/330 ED-APO, Lunt CaK B600 LS6CAKMDS2, ASI 178MM (cooled)
EQ3-mod, mountpusher, Lunt LS60T Ha B600, ASI 178MM (cooled)
EQ3-mod, mountpusher, Baader Astrosolar ND3.8 Film, TS-Optics 76/342 TS76EDPH, Baader Solar Continuum 7.5 nm 1.25″, ASI 178MM (cooled)
EQ3-mod, mountpusher, Baader Astrosolar ND3.8 Film, TS-Optics 76/342 TS76EDPH, Baader Venus U filter, ASI 178MM (cooled)
EQ3-mod, mountpusher, Sharpstar 60/330 ED-APO, Lunt CaK B600 LS6CAKMDS2, ASI 178MM (cooled)
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