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Old 03-11-2012, 12:23 PM
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Peter Ward
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Very Narrow Band-Pass filter Opportunity

I am looking at getting a custom run of 50mm square *1.5 nm bandpass* SII Ha and OIII filters made.

They will not be cheap..price TBA, but probably on a par with AstroDon 3nm (~$1k ea).....

To get a hold of a set, there is a minimum production run required, hence I'd be happy to sell the batch remainder at cost.

They will out perform *anything* currently available.

If you are interested send me a PM. Unfortunately without critical mass, it won't happen.

Last edited by Peter Ward; 03-11-2012 at 05:16 PM. Reason: more info, typo
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Old 06-11-2012, 06:26 PM
clive milne
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Peter,
As a vendor, I think it is incumbent upon you to include data on the focal ratio limit that these filters will actually offer an improvement over a 3nm (or even 10nm) passband filter.

2c

~c

Last edited by clive milne; 06-11-2012 at 09:08 PM.
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Old 07-11-2012, 09:33 AM
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Quote:
Originally Posted by clive milne View Post
Peter,
As a vendor, I think it is incumbent upon you to include data on the focal ratio limit that these filters will actually offer an improvement over a 3nm (or even 10nm) passband filter.

2c

~c
First up, This was never intended as a commercial post.

I was contacted by a filter OEM in the USA who has the capability to make ultra-narrow band filters...the likes of which I've not seen before, and would like to use myself.

The rub was, a minimum production run which would make incredibly costly
for just 3 filters.

I'm still waiting on the final specs myself, but yes, I take your point with convergent light cones there is likely to be a flattening of the bandpass curve. (also makes SII problematic)

That said, for anyone who have not used ultra-narrow band filters, there is a a chalk and cheeze difference between 3nm and 10nm filters, regardless of f-ratio. (AstroDon's web site has some nice examples)

Last edited by Peter Ward; 07-11-2012 at 10:15 AM.
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Old 07-11-2012, 11:14 AM
Poita (Peter)
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Any issues at f2?
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Old 07-11-2012, 06:16 PM
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Quote:
Originally Posted by Peter Ward View Post
That said, for anyone who have not used ultra-narrow band filters, there is a a chalk and cheeze difference between 3nm and 10nm filters, regardless of f-ratio. (AstroDon's web site has some nice examples)
I think Ken Crawford did this one which is a bit of an eye opener.

Out of my price range, we only got $28 instead of 28million out of lotto last night
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Old 07-11-2012, 08:35 PM
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You need dark skies for these or do they work in light polluted skies?

You will need long exposures. Any idea how much longer?

Greg.
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Old 07-11-2012, 09:11 PM
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Quote:
Originally Posted by gregbradley View Post
You need dark skies for these or do they work in light polluted skies?

You will need long exposures. Any idea how much longer?
They should work well under dark or light polluted skies but the narrower bandwidth would be particularly good for rejecting light pollution.

I'd argue that you don't need longer exposures with narrower bandwidth filters so long as they have equally good transmittance. Any extra signal you get with a wider filter is not useful data.

Cheers,
Rick.
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Old 09-11-2012, 08:48 AM
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Quote:
Originally Posted by gregbradley View Post
You need dark skies for these or do they work in light polluted skies?

You will need long exposures. Any idea how much longer?

Greg.
The narrower the filter, the brighter the sky you can accept (the filter rejects just about all unwanted sky background..a full moon/light pollution is not an issue ) . Exposures would be on a par with a 3nm..

That said it doesn't look like Oz has enough hard-core astro-imagers to make this one float.
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