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Old 24-09-2021, 08:16 PM
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multiweb (Marc)
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Venus UV/IR 22/09/2021

Got some pretty good data Wednesday night. It was nice and cool and the air was quite steady early evening. The scope was cool as well as I took it out later in the afternoon and it was kept indoors so I think it made a big difference. I caught Venus quite high in the sky. Luckily I was able to focus accurately as well. All worked perfectly this time.

I got 4 streams of 120s in UV and a couple in IR of the same duration.
CN-212 @ f/37 8320mm FL
Astronomik 807nm IR
Baader U Venus Filter 350nm
ASI462MC SER 16bit ~@100-130fps

Joined the video in PIPP and stacked the best 19% ~9000 frames.
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Old 24-09-2021, 08:38 PM
Lariliss (Larissa)
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Good pictures and the great model, posing photos.

Venus should be in focus of our cameras, in the same way as it is in focus of multi-functional exploration missions planned to it for deep understanding!
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Old 24-09-2021, 09:37 PM
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Looks great Marc

No issues with the 462 at the UV end then
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Old 24-09-2021, 09:54 PM
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Good pictures and the great model, posing photos.

Venus should be in focus of our cameras, in the same way as it is in focus of multi-functional exploration missions planned to it for deep understanding!
Thanks Larissa.

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Looks great Marc

No issues with the 462 at the UV end then
Thanks Dunk. Yeah no issues. The conditions were a lot better and I did remove the AR window on the camera this time as well as shooting in 16bit SER. So it's a combination of things. Removing the AR window did make the stream brighter in UV so maybe it's not a clear window. Can't be sure though if it's because the air was steadier but I could see the shades more clearly in the stream. Then again the clouds are different from beginning of the month and seem more pronounced. Processing the 23rd now see if it looks the same.
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Old 25-09-2021, 10:30 AM
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Very cool Marc - great stuff!
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Old 25-09-2021, 10:58 AM
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Was it difficult to remove the AR window? Wondering if itís worth doing on my 224mc or just leave as is?
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Old 25-09-2021, 11:10 AM
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Very cool Marc - great stuff!
Thanks Pete. I was quite happy with that one. My PB to date. It would be very hard to do better with my aperture. I was also advised to shorten my FL so will give that a go next.

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Was it difficult to remove the AR window? Wondering if it’s worth doing on my 224mc or just leave as is?
In my case it was just a matter of unscrewing the camera front and remove it. It's just a piece of glass held in place by pressure with an O'ring. Very cheap design but effective.
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Old 25-09-2021, 03:10 PM
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Cool shots of Venus. Great detail of the clouds.
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Old 25-09-2021, 03:11 PM
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Thanks Dunk. Yeah no issues. The conditions were a lot better and I did remove the AR window on the camera this time as well as shooting in 16bit SER. So it's a combination of things. Removing the AR window did make the stream brighter in UV so maybe it's not a clear window..
Ah thanks for the reminderÖI need to perform surgery on the 183 mono I was planning to try. I remember seeing a ZWO plot where the AR rolls off transmission below 400nm, so Iíd imagine they use much the same glass. The 462 has strong response in IR so itís not the usual UV/IR cut. Iíll also be using an SCT so that extra glass will no doubt work against me.

Itís really fascinating at the moment, as I donít remember seeing images like yours in previous years, so maybe itís a factor of UV-sensitive cameras becoming a bit more common. Good times
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Old 25-09-2021, 09:58 PM
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Originally Posted by Camelopardalis View Post
Ah thanks for the reminder…I need to perform surgery on the 183 mono I was planning to try. I remember seeing a ZWO plot where the AR rolls off transmission below 400nm, so I’d imagine they use much the same glass. The 462 has strong response in IR so it’s not the usual UV/IR cut. I’ll also be using an SCT so that extra glass will no doubt work against me.

It’s really fascinating at the moment, as I don’t remember seeing images like yours in previous years, so maybe it’s a factor of UV-sensitive cameras becoming a bit more common. Good times
Going to try with a ASI178MM next which is a lot more sensitive in UV. I also have to figure out if my barlow is opaque to UV. The FFC is a fluorite quadruplet.
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Old 25-09-2021, 09:59 PM
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Cool shots of Venus. Great detail of the clouds.
Thanks Ray. Yes I got a fair amount this time.
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Old 26-09-2021, 07:28 AM
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Another great set Marc.

Be interesting to see what the 178 yields. I'm weighing up a few options myself for doing our sister planet a bit more justice.

I read about the aperture thing too and I think that must have more to do with the shorter exposure times you'd be getting from a bigger objective rather than greater resolution. Meaning if you get good seeing (not easy for UV), you could compansate to some large extent, as you could with even more sensitivity in UV. 8.5" ain't too bad for an 18 arcsec object whose angular size will basically double by late November while still presenting enough sunlit surface for clouds to be seen. Also, UV should increase your instrument's resolution thanks to the shorter wavelengths. IR does the opposite.
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Old 26-09-2021, 08:23 AM
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Another great set Marc.

Be interesting to see what the 178 yields. I'm weighing up a few options myself for doing our sister planet a bit more justice.
Thanks

It does have a much better QE between 300 and 400nm ~40 to 60%. You have to take the AR window off again. I saw a UV shot on the same night taken with a C14 and the details blew my socks off.

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I read about the aperture thing too and I think that must have more to do with the shorter exposure times you'd be getting from a bigger objective rather than greater resolution. Meaning if you get good seeing (not easy for UV), you could compansate to some large extent, as you could with even more sensitivity in UV. 8.5" ain't too bad for an 18 arcsec object whose angular size will basically double by late November while still presenting enough sunlit surface for clouds to be seen. Also, UV should increase your instrument's resolution thanks to the shorter wavelengths. IR does the opposite.
True but the SNR is so much easier to reach with a a bigger aperture. The flux is just not there with 8.5". Too hard yakka that's why I've already been looking into getting a larger mirror. I'll see what the 178MM brings up. They're on back order. I have no idea what availability and delivery times are right now.
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Old 26-09-2021, 09:16 AM
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Going to try with a ASI178MM next which is a lot more sensitive in UV. I also have to figure out if my barlow is opaque to UV. The FFC is a fluorite quadruplet.
Got the answer about the FFC. Somebody asked the same thing
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Old 26-09-2021, 10:11 AM
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Cool shots Marc.
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Old 26-09-2021, 11:01 AM
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Good to know the C14 works well at UV. I'll try our club's again when conditions are better.

When I had the 120MM on the 8" dob, I thought the SNR wasn't too bad actually. Image scale was the problem there, and to a degree, seeing. I'll have a 8" GSO CC here soon so will see what that might yield. Sick of doing hand tracked vids with the dob...
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Old 26-09-2021, 11:53 AM
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That's an interesting comment about AR coated windows...
I use the ASI 178 with the MiniSHG and have imaged in the CaK with no problems.
I should remove the window and see if the difference is measurable with the spectrograph.
The ZWO data shows a 15% QE at 300nm which doesn't seem to match an issue with the coated window.
https://astronomy-imaging-camera.com.../asi178mm-mono
ZWO also push to use a UV-IR filter on colour camera with AR coated windows??!!
https://astronomy-imaging-camera.com...-ir-cut-filter
This infers to me that the AR coating is not equivalent to a UV reject coating.
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Old 26-09-2021, 12:35 PM
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Originally Posted by peter_4059 View Post
Cool shots Marc.
Thanks Peter.

Quote:
Originally Posted by N1 View Post
Good to know the C14 works well at UV. I'll try our club's again when conditions are better.

When I had the 120MM on the 8" dob, I thought the SNR wasn't too bad actually. Image scale was the problem there, and to a degree, seeing. I'll have a 8" GSO CC here soon so will see what that might yield. Sick of doing hand tracked vids with the dob...
Actually I have a 8.5" TAK CC and I would love to start pushing a big dob.

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Originally Posted by Merlin66 View Post
That's an interesting comment about AR coated windows...
I use the ASI 178 with the MiniSHG and have imaged in the CaK with no problems.
I should remove the window and see if the difference is measurable with the spectrograph.
Excellent. It'll be interesting to see the results.

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Originally Posted by Merlin66 View Post
The ZWO data shows a 15% QE at 300nm which doesn't seem to match an issue with the coated window.
https://astronomy-imaging-camera.com.../asi178mm-mono
ZWO also push to use a UV-IR filter on colour camera with AR coated windows??!!
https://astronomy-imaging-camera.com...-ir-cut-filter
This infers to me that the AR coating is not equivalent to a UV reject coating.
I have a graph from C. Pellier that was sent to me recently about the AR window cut in the lower part of the spectrum. It's on my other PC. I'll post it.
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Old 26-09-2021, 01:44 PM
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Here's the info that was emailed to me Wednesday 22/09/2021 by Niall McNeill and here his shot of Venus on POVL. Same patterns I caught but so much better resolved.
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Old 26-09-2021, 02:50 PM
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I would have thought his comparison would have included the Baader CCD Blue filter and the Baader Venus filter
https://www.baader-planetarium.com/e...er-(blue).html
https://www.baader-planetarium.com/e...---350nm).html
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