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 Post subject: Re: IR/UV cutoff
 Post Posted: Wed Nov 15, 2017 4:53 pm 
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Joined: Wed Nov 09, 2016 11:37 pm
Posts: 46
Location: Oslo & Jotunheimen, Norway
Sam wrote:
you can use one 1.25" filter on the 294 with the help of 1.25-T2 adapter

Yeah I think we could, sometimes. Other times we shouldn't. And other times again, we can't.
- Ok if the scope is not faster than f/4 or so, and there's enough room for the relatively high 1.25" cell filter plus adapter, and the sensor is not bigger than 4/3.
- Not ok with fast instruments like a f/2 Hyperstar setup, much more vignetting introduced in a case with relatively bad inherent vignetting.
- Many mFT lenses are of great value and quality, but could only be used, with a 1.25" filter and the 1.25-T2 adapter, if the filter cell above the threads are 4.0mm or less. Have not come across anything lower than 6.0mm.

Sam, can I please have the exact protect window (glass) measurements?
I'd say ZWO is specializing in cameras, wouldn't expect that you have all kinds of filters!
(ASI camera body design housing a protect window based on standard filter sizes, like unmounted 31mm and 36mm, would be great)
It's only EUR 55 extra, plus long wait, to have custom size filters, as long as the thickness matches reasonably.

_________________
-olav
CGEM-DX, AZ-EQ6 x2, C11HD/.7red/Hyperstar, TS-APO130 flat/red, TS-Star71, ASI1600MMC + EFWmini w/CLS-RGB-Ha, ASI1600MMC + EFW w/CLS-LRGB-Ha-O3-S2, ASI294MCPro, ASI290MM + EFW w/LRGB+IR642+IR742+IR807+U+CH4, SmartEQpro, EOS5D2-mod & ++lenses.


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 Post subject: Re: IR/UV cutoff
 Post Posted: Thu Nov 16, 2017 9:37 am 
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Joined: Wed Nov 09, 2016 11:37 pm
Posts: 46
Location: Oslo & Jotunheimen, Norway
I ended up with a temporary solution, making a "filter rim extender" for 31mm filters.
I think the mounted 31mm filters, from Astronomik and possibly other manufacturers, were best suited. The rim is thin and low, no threads or profiling. These filters measure 31.08 x 3.62 mm.
I pressed the filter into a 3mm thick plastic disc, making it flush at bottom and sticking out 0.62mm at the top, which is ok even for the tight mFT lenses.

As for the ASI294, I'd say that the lack of an original or accessory IR/UV-block protect window is a glitch.
Due to it's very high dark current (but other great features), the only good AP scenario would be with very fast instruments, making 1.25" filter/holder not such a great idea. (Check out the CN thread if you'd like)

_________________
-olav
CGEM-DX, AZ-EQ6 x2, C11HD/.7red/Hyperstar, TS-APO130 flat/red, TS-Star71, ASI1600MMC + EFWmini w/CLS-RGB-Ha, ASI1600MMC + EFW w/CLS-LRGB-Ha-O3-S2, ASI294MCPro, ASI290MM + EFW w/LRGB+IR642+IR742+IR807+U+CH4, SmartEQpro, EOS5D2-mod & ++lenses.


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