hope you've all enjoyed the conjunction of jupiter and venus after sunset. here's a cellphone shot from my front yard:
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| venus above jupiter 6/9/2026 8:48 pm |
i've been taking the opportunity to point the bigger scope at venus with some success, catching cloud structure in ultraviolet light:
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| Venus UV-IR 6/13/26 used the Baader UV for this |
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| Venus UV 6/13/2026 03:33 UTC cloud structure visible |
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| Venus IR 6/13/26 04:07 UTC partially illuminated disk without cloud structure |
Thorlabs ultraviolet filter:
i was informed that the Thorlabs UV filter (bandwidth 380-420 nm) is better than typical filters such as the baader U-filter for my system as the coatings on SCT scopes block much of the UV light in the range of the U-filter. i've been trying to capture images with this filter for the past year with no success. i've dispensed with the barlow, tried earlier and later in the day...nothing but a white disk. Having tried 2 days in a row with no contrast, i decided to run a comparison between the two...and voila i detect cloud structure with both filters!
i guess the take home is that you need to keep firing away for good atmospheric conditions on both earth and venus.
Comparison below:
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| Baader U filter 320-380 nm average of 2 nine minute captures details below |
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| Thorlabs UV filter 380-420 nm average of 2 nine minute captures details below |
My impression is that the contrast is better with the Baader filter, but the image is more blurry. The Baader filter required 10 times the exposure as the Thorlabs (10 ms vs 1 ms) likely making the latter more effective at "freezing" seeing, giving a sharper image. Now it's time to get out the Barlow where the transmission difference will be a more significant factor.
Note, the Thorlabs filter came in an unconventional size, requiring a separate order of an adapter, so be sure and speak with someone about the appropriate adapter if ordering.
image details:
East Bluff, CA
wide field Samsung galaxy S22 ultra
6/9/2026 8:48 pm
venus
6/13/26 03:15-04:07 UTC
camera ZWO ASI 290MM
filters: Baader IR pass "685", Baader U-filter bw 320-380 nm, Thorlabs UV filter 380-420 nm
celestron 11" Edge HD, no barlow
firecapture
autstakkert (best 10%)
biggsky
photoshop
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UV 350 nm 03:33.5 UTC 20:33.5 local alt 24 deg Duration=540.004s FPS (avg.)=91 Shutter=10.80ms Gain=351 (58%) Histogramm=71% |
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UV 350 nm 03:43 UTC 20:43 local alt 22 deg Duration=540.000s FPS (avg.)=67 Shutter=14.80ms Gain=351 (58%) Histogramm=91% |
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UV 400 nm 03:15 UTC 20:15 local alt 28 deg Duration=540.004s FPS (avg.)=451 Shutter=1.022ms Gain=351 (58%) Histogramm=78% |
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UV 400 nm 03:58.3 UTC 20:58.3 local Alt 18 deg Duration=539.989s FPS (avg.)=451 Shutter=1.818ms Gain=351 (58%) Histogramm=85% |
IR 685 nm
(IR image above)
04:07.4 UTC
20:07.4 local
alt 17 deg
Duration=180.005s
FPS (avg.)=451
Shutter=0.119ms
Gain=306 (51%)
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