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Location of Gasspath

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Starry Jack
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Location of Gasspath

Post by Starry Jack » Sun Jul 07, 2019 2:00 pm

Does the distance of the glass path from the front of the etalon matter? I have a Baader 1:7 glasspath snug in front of the etalon in a 152mm f6.5 stage two mod (using the original blocking filter).

Thanks,
Jack
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marktownley
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Re: Location of Gasspath

Post by marktownley » Mon Jul 08, 2019 5:17 am

Yes, the greater the distance the greater the magnification (and aberrations) produced. A glasspath will have a working distance listed somewhere I guess.
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Starry Jack
Im an EXPERT!
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Re: Location of Gasspath

Post by Starry Jack » Mon Jul 08, 2019 5:35 pm

Thank you, Mark
Explore Scientific 152mm f6.5 achromat
Aeries D-ERF
Quark Chromosphere f27 native, (f14 when focal reduced)
Mallincam .5x focal reducer (large format)
ZWO174 (IMX249 chip 5um)
Huge Sense of Adventure Viewing Creation

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Re: Location of Gasspath

Post by AndiesHandyHandies » Tue Jul 09, 2019 8:39 pm

Hi

Its the distance the barlow is from the focal plane which matters.

I have found, with measurements on stars by AstroRod, that placing a 2" 2x ED barlow in front of the PST Etalon, that because there it is about 200mm effectively from the focus of the re-focussing lens focal plane it actually gives 4x.

So I would expect the glasspath in the same place to give double its rated power. So I suppose it is optimum on a F6.7 scope. F6.7 x 1.5 = F10.

Andrew.

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