ITF filter on the way out?

Use this section to discuss "standard" Baader/Coronado/ Lunt SolarView/ Daystar, etc… filters, cameras and scopes. No mods, just questions/ answers and reviews.
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swisswalter
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Re: ITF filter on the way out?

Post by swisswalter » Sun Dec 14, 2014 6:34 am

Hi John

sorry to hear that. Drop Rikki an email, she will send you a new one, easy replacement.
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Re: ITF filter on the way out?

Post by swisswalter » Sun Dec 14, 2014 8:24 am

O.k. John

good luck. If everything breaks, just drop me an email. I might have an original ITF for free
Only stardust in the wind, some fine and some less fine scopes, filters and adapters as well. Switzerland 47 N, 9 E, in the heart of EUROPE :)

from 7 am - 7 pm http://www.nanosys.ch

from 7.01 pm - 6.59 am http://www.wastronomiko.com some times vice versa ;)

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swisswalter
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Re: ITF filter on the way out?

Post by swisswalter » Wed Dec 17, 2014 5:18 am

Hi John

great news. Sealing the edge sure doesn't hurt
Only stardust in the wind, some fine and some less fine scopes, filters and adapters as well. Switzerland 47 N, 9 E, in the heart of EUROPE :)

from 7 am - 7 pm http://www.nanosys.ch

from 7.01 pm - 6.59 am http://www.wastronomiko.com some times vice versa ;)

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Bob Yoesle
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Re: ITF filter on the way out?

Post by Bob Yoesle » Fri Dec 19, 2014 7:50 pm

The edge of a new ITF should already be sealed with an epoxy resin. It fails due to thermal loading and cycling - developing micro-cracks which allow atmospheric moisture to invade the filter layers. To avoid this from occurring, you need to use an IR blocking filter a head of the ITF. This would be a Baader DERF, the Lunt EFR, or the BelOptic ERF, etc. You could also use a sub-aperture secondary IR "mini" ERF ahead of the ITF, such as the Baader Red CCD filter.

FYI - Lunt seems to have moved away from using an ITF in their newer solar scopes. Instead, they use a "blue glass" filter substrate with AR coatings, combined with IR blocking on the ERF, etc. Some of these have also experienced deterioration of the AR coating, but this generally appears toward the center of the filter, not the periphery as occurs with the ITF. Lunt has been just as diligent in replacing these as well.

This trend away form using an ITF and instead using an IR blocking ("hot mirror") and absorbing element is also used in the SolarScope blocking filters, and can be readily adapted to most etalon systems: Use an IR blocked ERF such as the Baader, Lunt, or BelOptic, combined with use of a short IR dielectric on a blue glass or a KG heat absorbing substrate for the longer IR.

I'm replacing the rusting ITF on a Coronado BF30 with Oliver Smie's ( BelOptic http://beloptik.de/en/top/welcome/ ) UV/IR cut on KG3 ( http://beloptik.de/en/left/if-uv-ir-cut ... ng-filter/ ) as the ITF replacement, used in concert with my Baader DERF 110. Essentially what is used by SolarScope for its filter systems. Oliver's prices are very reasonable, and he turned the 48 mm version down to 34 mm for a little extra in order to be a drop-in replacement, allowing the filter to fit in the tilted ITF cell... :-)
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Re: ITF filter on the way out?

Post by Andre444 » Tue Oct 30, 2018 9:37 pm

Hi, if i replace the original ITF from the pst for the beloptic ITF . Will i able to use higher magnification? Thanks.

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Re: ITF filter on the way out?

Post by Bob Yoesle » Tue Oct 30, 2018 11:09 pm

Perhaps, but the only difference may be image brightness (peak transmission), not resolution or ability to magnify the image. A brighter image does make higher magnifications easier to be able to see detail with. Check with Oliver at BelOptik.

If the PST has another RG630 filter in the filter system, then the BelOptik UV/IR KG3 filter might be adaptable to replace the ITF. Again, contact Oliver and see what he says.
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