Wratten #39 filter

[Merlin66]

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?

[JA]

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/274394855882?var=574525500112


ZWB1.... reasonably tight around 320nm without much appreciable Red-IR pass response
https://www.ebay.com.au/itm/274394021287?var=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/273922140011?var=574524784290

Best
JA

[N1]

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.

[Merlin66]

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)

[astro744]

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/product/809761-REG/Sensei_sur4648_46_48mm_Step_Up_Ring .html

and

https://www.amazon.com/Sensei-SUR4648-46-48mm-Step-Up-Ring/dp/B00AE1MPJ4

[Merlin66]

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!!!!!!!!!!!!!!!!!

[astro744]

The Amazon freight is ridiculous. Even the filter price. I didn’t click further so didn’t 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/Sensei-48-46mm-Step-Down-Ring

Just read the description and make sure it is what you want.

[astro744]

I found the following explaining step-up and step-down tings.

https://www.bhphotovideo.com/explora/photography/hands-review/wisdom-step-and-step-down-rings