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Old 30-11-2021, 10:57 AM
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Merlin66 (Ken)
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Wratten #39 filter

Looking at the various options (to assist with parasitic light in CaK) I found an interesting KODAK filter listed as "glass #39".


I've been unable to find a source of this filter....


Do any of the camera buffs have any contacts with technical filter suppliers who may be able to help?
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Old 30-11-2021, 05:26 PM
JA
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Hi Ken,

here are a couple of 380-390nm + one 320 filter

ZB1 B390....reasonably tight around 380nm without much appreciable Red-IR pass response. Many sizes available all mounted
https://www.ebay.com.au/itm/27439485...r=574525500112


ZWB1.... reasonably tight around 320nm without much appreciable Red-IR pass response
https://www.ebay.com.au/itm/27439402...r=574524646322


ZB2....reasonably tight around 380nm with appreciable Red-IR pass response. Many sizes available all unmounted, but you could possibly use a 48mm filter housing and perhaps fit one of the 45 or 46.5mm unmounted filters in it.
https://www.ebay.com.au/itm/27392214...r=574524784290

Best
JA
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Old 02-12-2021, 04:05 PM
N1 (Mirko)
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Ken, while I can't provide a specific answer re this filter, have you looked at the offerings of Edmunds, Thorlabs and the like? You'd be like a kid in toy shop with your particular interests. Can't comment on Thorlabs shipping but Edmunds ship from Singapore and while not cheap, it's pretty smooth and painless.
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Old 03-12-2021, 10:02 AM
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Merlin66 (Ken)
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OK, to wrap up the Search of the Holy Grail and show the final outcome....


Object:
To find a filter (or combo of filters) suitable for use with the MiniSHG to image CaK (393nm wavelength)


Solution:
The Astronomik L1 UV-IR filter blocks below 385nm and above 700nm
A Baader ND8 filter suppresses the light (12.5% transmission) across the spectrum


Plus either:
1. W47 "violet" filter - pretty common in astronomy - venus etc. This has a NIR leak suppressed by the UV-IR above. This filter has been given the thumbs up by other SHG users.

2.HOYA FL-W - this has a good transmission at 393nm and suppresses the visible spectrum. Looks promising, could be better than the W47.

3. ZB1/ZB2 - ZB2 has the best transmission at 393nm and suppresses visual but has a NIR leak. TBD



The other possible contenders are no longer available.
Kodak E39 last produced 1975

Hoya C12 Blue Cooling last produced 2015


I've ordered #1/#2/#3 filters for spectroscopic transmission testing and evaluation in the MiniSHG.
I'll hold the "best for the SHG" and re-sell the others.
(Anyone know where to find a M46 to M48 step up adaptor? ie to fit a 46mm filter on a 48mm female thread)
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Old 03-12-2021, 11:31 AM
astro744
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Quote:
Originally Posted by Merlin66 View Post
(Anyone know where to find a M46 to M48 step up adaptor? ie to fit a 46mm filter on a 48mm female thread)
Could you clarify what you need. Does your filter have a 48mm male thread and you want to screw onto lens/camera with 46mm female thread? The step up ring steps up from 46mm to 48mm from the cameras point of view. The step-up ring would have a 46mm male thread to fit the female thread on the camera/lens and 48mm female thread to fit the male thread of the filter. If the filter is smaller than the camera/lens then you need a step down ring which would have 46mm female thread to take a 46mm filter and 48mm male thread to screw onto camera/lens with 48mm female thread on it.

Only available in OS that I found so far but you could ring some camera stores. Its not a common size jump here. These are step-up rings.

https://www.bhphotovideo.com/c/produ...p_Up_Ring.html

and

https://www.amazon.com/Sensei-SUR464.../dp/B00AE1MPJ4
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Old 03-12-2021, 11:51 AM
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Merlin66 (Ken)
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I have an existing M48 filter with a front female thread and wish to mount a M46 filter on the front.
I think this needs a M48 male (to fit the existing filter) and a M46 female (to take the new filter)


Hmmmm $300 for the amazon one!!!!!!!!!!!!!!!!!
Attached Thumbnails
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Last edited by Merlin66; 03-12-2021 at 02:05 PM.
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Old 03-12-2021, 02:50 PM
astro744
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The Amazon freight is ridiculous. Even the filter price. I didnít click further so didnít see that. Sorry.

The Bhphoto one is reasonable. Not sure of freight.

I think though from your description you want a step down ring not a step up.

I found this one for you locally.

https://www.rubbermonkey.com.au/Sens...Step-Down-Ring

Just read the description and make sure it is what you want.
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Old 03-12-2021, 05:20 PM
astro744
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I found the following explaining step-up and step-down tings.

https://www.bhphotovideo.com/explora...tep-down-rings
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