some questions about Quark: filter, barlow...

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OscarP
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some questions about Quark: filter, barlow...

Post by OscarP »

Hello:

i have a Quark Chromo (4.2x) and a cheap 102mm f500 refractor in SW altz goto mount. Small+cheap+fast setup.
I use it for visual (99% time) with Baader uv/ir 2" in the nose of 2"diagonal, and usually with aperture stopped to 65,75,..and only short time frames.

It is a good idea to use a Barlow for achieve ideal F values with a fast (and cheap) achromatic refractor?
I read people do this with Quark Combo, but with a Quark with 4.2x, in F4.9 refractor, you can get a "decent" F30 small setup with a 1.5x Barlow...
I know the best is telecentric optics, but I think a normal Barlow can´t do so much worse a cheap achro optics..
I have a televue powermate 2.5x 1.25", but it gives me a very high F51 (f5250) , and a 1.5x Barlow can give me F30., so.l..:

must i stop my refractor aperture from 102 to 70 to achieve F30 or can i use a 1.5x barlow in quark´s nose and use all my 102mm?


Second question is if i use full 102 aperture maybe my 2" Baader/uv/ir is a small protection (front mount erf it´s far from my budget), so:
must i use a baader 35nm ccd filter and how? stacked with 2" uv/ir? before or after uv/ir? only one of them? Maybe the 2" uv/ir in the nose of diagonal and a 1.25" 35nm in the nose of barlow/quark?

Thanks, and sorry for this large text, is better ask to experienced users and no to play with my eyes...


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MalVeauX
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Re: some questions about Quark: filter, barlow...

Post by MalVeauX »

Hi,

You're much better off masking the aperture than introducing a barlow before your Quark. The angles generated in a barlow are different than in a telecentric. A barlow just isn't what you want to use for a mica-spaced etalon, it needs on-axis parallel rays, which comes from telecentric. So just mask your aperture to produce the desired focal-ratio needed and you're set.

Yes, your 35nm HA filter is a good D-ERF to use. Take out the UV/IR block filter and just put the 35nm HA filter there instead on the nose before your diagonal or 2" extension or whatever you're using. It will eliminate more thermal energy and handle larger apertures. The 2" UV/IR block filters really do not block much heat in reality.

Very best,


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Re: some questions about Quark: filter, barlow...

Post by marktownley »

Stopping down to 70mm is the best approach.


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Valery
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Re: some questions about Quark: filter, barlow...

Post by Valery »

OscarP wrote: Mon May 24, 2021 9:53 am Hello:

i have a Quark Chromo (4.2x) and a cheap 102mm f500 refractor in SW altz goto mount. Small+cheap+fast setup.
I use it for visual (99% time) with Baader uv/ir 2" in the nose of 2"diagonal, and usually with aperture stopped to 65,75,..and only short time frames.

It is a good idea to use a Barlow for achieve ideal F values with a fast (and cheap) achromatic refractor?
I read people do this with Quark Combo, but with a Quark with 4.2x, in F4.9 refractor, you can get a "decent" F30 small setup with a 1.5x Barlow...
I know the best is telecentric optics, but I think a normal Barlow can´t do so much worse a cheap achro optics..
I have a televue powermate 2.5x 1.25", but it gives me a very high F51 (f5250) , and a 1.5x Barlow can give me F30., so.l..:

must i stop my refractor aperture from 102 to 70 to achieve F30 or can i use a 1.5x barlow in quark´s nose and use all my 102mm?


Second question is if i use full 102 aperture maybe my 2" Baader/uv/ir is a small protection (front mount erf it´s far from my budget), so:
must i use a baader 35nm ccd filter and how? stacked with 2" uv/ir? before or after uv/ir? only one of them? Maybe the 2" uv/ir in the nose of diagonal and a 1.25" 35nm in the nose of barlow/quark?

Thanks, and sorry for this large text, is better ask to experienced users and no to play with my eyes...
Using of the 1,5x Barlow in this telescope will work absolutely nicely. I doing this with my two F/5 refractors 100mm and 150mm.
The native Quark telecentric 4.2x will produce a telecentric beam in either way will you use a Barlow before it or no barlow at all.

A 2" Baader 35mm should be mounted in a front tube of a 2" diagonal. However if your scope will track the sun for long periods, better to use a front full size DERF filter. This will prevent any kind of internal tubulence.

See the image taken with a Quark Chromosphere (standard version) with a 150mm F/5 refractor + full size ARIES DERF+ 2x Barlow + Basler1920-155 camera.

As you can see, there is no any detectable image degradation due to Barlow 2x use.


Valery
Attachments
_2020-06-08 UT04h45m SW150F5 full size DERF ARIES 2xBL QUARK Chr Basler1920.jpg
_2020-06-08 UT04h45m SW150F5 full size DERF ARIES 2xBL QUARK Chr Basler1920.jpg (429.53 KiB) Viewed 858 times


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