Front end replacement ERF for new "blue" PST??

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Re: Front end replacement ERF for new "blue" PST??

Post by marktownley »

Interestingly I tried this (in my bf15) with a unmodified SM90ii etalon yesterday, and with the CCD there is quite clearly a huge light leak going on somewhere, the ccd sensor was completely saturated. Putting a 7nm Baader ha filter in the optical train stopped this.

I also found that the front surface of the mirrored (objective side of the filter) had developed a frosted surface to it. I've tried to get some pics of this but is difficult to see in the camera...
P1080245.JPG
P1080246.JPG
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This is very clearly on the top surface and is soft and can be 'scratched off'. I'm going to try and remove it chemically. Interestingly i've seen on the CN forum several times now, people reporting exactly this same thing on Lunt CaK and Ha blockers on the ITF.

Anybody else got / seen this?


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Re: Front end replacement ERF for new "blue" PST??

Post by swisswalter »

Hi Mark

that does not look good at all with that ITF filter. I would not chemically clean it, instead take a Diamond based grinding paste with a grain of 125 nm diameter Free samples on request ;)


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Re: Front end replacement ERF for new "blue" PST??

Post by marktownley »

It is water soluble, as is the coating on the other side of the filter... :?


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Re: Front end replacement ERF for new "blue" PST??

Post by swisswalter »

marktownley wrote:It is water soluble, as is the coating on the other side of the filter... :?
Mark do I understand that right? The stuff which migrates to the surace is water soluble.


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Re: Front end replacement ERF for new "blue" PST??

Post by marktownley »

It 'washes' off with a cotton bud dipped in water, as does whatever is coating the rear side of the filter... Very unusual...


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Re: Front end replacement ERF for new "blue" PST??

Post by swisswalter »

Hi Mark

next time when cleaning the ITF please send me the Cotton bud, I'll analyse the substance which migrates to the surface


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Re: Front end replacement ERF for new "blue" PST??

Post by Merlin66 »

Mark,
Interesting....
I haven't seen similar "staining" on my Maier filter - not yet anyway.......


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Re: Front end replacement ERF for new "blue" PST??

Post by Merlin66 »

Mark,
Seems strange based on earlier reports and the transmission curves we've seen that your SM90/Maier results should be so dramatically different.
Have you tried a combo of the BelOptic UV-IR/Kg3 and the Maier???


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Re: Front end replacement ERF for new "blue" PST??

Post by marktownley »

Hi Ken, I don't have the beloptik uv/ir kg3, but the baader 7nm Ha or D-ERF used in conjunction with the SM90 completely solved the problem... Weird...


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