PST stage 2 mod :ERF question.

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inhapi
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PST stage 2 mod :ERF question.

Post by inhapi »

I got my hands on a free (!) PST. The coating on the (pre meade era) 40 mm lens is corroded, but I hope the etalon is still fine.

I plan to do a stage 2 mod. I have found the suitable adaptors for it already online (swiss shop porduces them.)

I wonder, using a 70mm F8 refractorr: do i need a full sized front ERF of can I use one of these internal 2" ERF's

e.g.:https://www.teleskop-express.de/en/filt ... read-16760
There is also this option from Antila:
https://www.teleskop-express.de/en/antl ... erf2-17768

I will test this mod on a 80 mm refractor as said, but if it works well I might use it on an 120 mm refractor, but then with front erf.

Thanks for any help.


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Re: PST stage 2 mod :ERF question.

Post by Dennis »

To me the Antlia 2" version looks like a nice solution for a 70mm refractor.
If only this was available when i started out with my Quark and a 100mm refractor.


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Re: PST stage 2 mod :ERF question.

Post by inhapi »

Would I be able to use this on a 100mm or even 120 mm refractor ?


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Re: PST stage 2 mod :ERF question.

Post by marktownley »

I've used a 2" filter as a sub aperture ERF on 100mm and was OK, an external is better though.

Dpn't forget that 70mm scope needs to be running closer to f10 to work well/


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Re: PST stage 2 mod :ERF question.

Post by inhapi »

okay, Also have a 90 F10, seems perfect then.


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Re: PST stage 2 mod :ERF question.

Post by marktownley »

inhapi wrote: Thu Mar 07, 2024 9:28 pm okay, Also have a 90 F10, seems perfect then.
I think that would be your best choice for a PST mod.


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Re: PST stage 2 mod :ERF question.

Post by AndiesHandyHandies »

Hi

On my 90mm F6.7 I use an internal ERF stack. And done extensive temperature and safety reviews.

I would do a better job than Daystar suggest to lengthen the life of the blocking filter and keep it cool and on band.

I use a T2 Baader prism. With some Blue Lightning T2 pass-through to 1.25" filter adapters for mounting 1.25" and 2" filters for a ERF pack.

First on the front T2 thread of the diagonal the above adapter with a 1.25" 7nm Baader.
Then a T2 to 2" nosepiece, 2" Red CCD filter, then a 2" UV-IR filter and then another T2 to 1.25" pass through with a 1.25" Cheap Chinese filter body with 20mm aperture. The front two bits have had the black turned off and the alloy slightly hollowed and polished to reflect unwanted heat. When setting up and till on axis.

The UV-IR filer is positioned so that the cone of light only falls on it in use. As optical glass absorbs little energy and when on the sun you can see the reflected light passing safely back out of the front of the scope, half the apature.

Cheers. Andrew.


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