ERF's and a Quark +150mm F5 Refractor

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pete_w
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ERF's and a Quark +150mm F5 Refractor

Post by pete_w » Sun May 29, 2016 11:34 am

Hi,
When using a Quark with a 150mm F5 refractor is there a way to avoid the cost of an external full diameter ERF?
Could I use internal 2" filter(s) as an ERF like the Baader 35nm H-Alpha maybe with a UV/IR cut behind it?
Is it safe/possible to mount a D-ERF of less than full diameter, say 2" - 3", internally, as long as its at the end of a tube with no opportunity for light to circumvent it?
Thanks
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Re: ERF's and a Quark +150mm F5 Refractor

Post by grimble_cornet » Sun May 29, 2016 12:08 pm

Several people seem to be doing it:
A couple of people on here are using smaller ERFs mounted internally - I did this with a 70mm Baader ERF mounted on the inner end of the focuser tube of my 152mm f5.9 before getting a 160mm external one.
Rupert at Astrograph.net is selling a 152mm plus Quark package which uses a 2" Baader 35nm H-Alpha filter fitted internally so I would imagine its safe.
I went for the 160mm external to reduce tube currents and it does make a difference but at a significant cost.
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Re: ERF's and a Quark +150mm F5 Refractor

Post by Bojan » Mon May 30, 2016 1:39 am

Acording to daystar an ERF is necessary only above 150mm however verify this yourself.

Yes it is possible to mount an ERF internally but you will still be rejecting the heat in the tube which will cause turbulence and "poor seeing". You won't be getting the full benefits of mounting the ERF internally vs externally

A UV/IR cut filter could be used and as long as you're not tracking too long you should be ok.
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Re: ERF's and a Quark +150mm F5 Refractor

Post by marktownley » Mon Jun 06, 2016 7:43 pm

It will work, just at the expense of seeing due to turbulence.
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Re: ERF's and a Quark +150mm F5 Refractor

Post by Valery » Thu Jun 16, 2016 9:34 am

marktownley wrote:It will work, just at the expense of seeing due to turbulence.
The seeing is the most expensive component in the successful imaging. I would gladly pay, without any hesitation for a better seeing in my telescopes. For example, let take that a typical seeing in my telescopes at my location is 1,5" - 2". I will immediately pay 50K for the seeing improvement to 0,7" - 1". And will pay $250K for 0,5" - 0,7". I then will build several small and medium sized domes for rent at such an excellent seeing place!

And I can't understand the sense of having 150mm scope which will work mostly at the level of 100-120mm scope.
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Re: ERF's and a Quark +150mm F5 Refractor

Post by marktownley » Thu Jun 16, 2016 12:39 pm

Valery wrote:The seeing is the most expensive component in the successful imaging. I would gladly pay, without any hesitation for a better seeing in my telescopes. For example, let take that a typical seeing in my telescopes at my location is 1,5" - 2". I will immediately pay 50K for the seeing improvement to 0,7" - 1". And will pay $250K for 0,5" - 0,7".

And I can't understand the sense of having 150mm scope which will work mostly at the level of 100-120mm scope.
Totally agree Valery.

I'm set up now with air cooling for my HaT to see what effect (or not) tube currents has on imaging with respect to the telescope being acclimated.
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