Barlow with Lunt CaK

[TareqPhoto]

Hi again,

I want to know when imaging using Lunt CaK, if i want to add a Barlow to go close ups, where should i place the Barlow, before the Lunt module or after i mean between the module and telescope or module and camera?

If i will place it before the module which is between telescope and module then how to protect the Barlow, using just UV/IR cut filter? Doesn't this filter kill the CaK band then?

Also from Lunt site they mentioned that it is recommended to use a refr up to 100mm aperture, i have B1200 so it is ok up to 120mm focal length, what will happen if we use for example a scope with 150mm stopped down to 100mm?

What is the best protection filter to be used with CaK? I mean CaK is just near by UV band, if using UV block filter isn't that like blocking CaK even slight?

[robert]

UV filter does block CaK. You can use an IR filter. The Barlow is ok between the module and camera. I have been using this arrangement for several years with an ED80 and ED100. No issues so far. Good luck.
Robert

[TareqPhoto]

UV filter does block CaK. You can use an IR filter. The Barlow is ok between the module and camera. I have been using this arrangement for several years with an ED80 and ED100. No issues so far. Good luck.
Robert

Ok, thank you very much Robert

[Montana]

I use the Lunt CaK on a TEC140 stopped down to 100mm. I also use from a 2x Barlow up to a 5x powermate between the module and camera. Been using it for years no problem.

Alexandra

[christian viladrich]

What size is your Barlow lens ?
As long as the light beam does not touch the metal body of the Barlow, there is no issue.
In orther words, you can use : refractor > Barlow lens > Lunt Ca K with no problem if the light beam passes only through the lens of the Barlow and does not touch its body.

[TareqPhoto]

I use the Lunt CaK on a TEC140 stopped down to 100mm. I also use from a 2x Barlow up to a 5x powermate between the module and camera. Been using it for years no problem.

Alexandra

That is great, so i will do that then, sounds it is better to place the Barlow after the module and not before.

Thank you

[TareqPhoto]

What size is your Barlow lens ?
As long as the light beam does not touch the metal body of the Barlow, there is no issue.
In orther words, you can use : refractor > Barlow lens > Lunt Ca K with no problem if the light beam passes only through the lens of the Barlow and does not touch its body.

I have Televue Powermates 2x and 5x, and also Televue 3x Barlow, but i really can't risk having any Barlow before the CaK if isn't protected or facing the scenario you mentioned, the body is getting hotter, i will insert it after and see how is that gonna work.

[Dennis]

The barlow will go between Lunt filter and camera. If you use a refractor up to 100mm aperture no extra filtering / protection is necessary. Stopping down to 100mm works too.

[TareqPhoto]

The barlow will go between Lunt filter and camera. If you use a refractor up to 100mm aperture no extra filtering / protection is necessary. Stopping down to 100mm works too.

Nice, mostly i won't use the Barlow with larger aperture scopes because they are already longer FL, unless i use something not that long, but i can try using the Barlow when necessary, just wanted to know where i can mount it, so it is after the Lunt module, while with Quark it is before.

I am thinking about selling my Televue 3x Barlow and go with something like Baader Telecentric 3x instead, TV 3x isn't bad but not in same quality class as Powermate, so maybe a telecentric Barlow can do better job than standard Barlow, for 4x i still think about Powermate because i will use it for planetary.

[Bob Yoesle]

My choice for optimum high resolution work would be to use a telecentric configuration and the Baader Research Grade TZ3, which is stated specifically corrected for CaK "Diffraction limited design with about 80% Strehl also at 396 nm (CaK)." Both the new TZ-3S and TZ-4S are stated to be "Designed especially for H-alpha and CaK subangstroem (sic) etalon filters."

Baader has an extensive Manual for the correct implementation of Solar Spectrum filters with their telecentric lens systems.

For using larger aperture, Altair Astro makes DERFs that can be used both for H alpha a CaK/H filters.

For a filter with a ~2.2 FWHM, an effective focal ratio of f20 + via the TZ3 (or the TZ-3S or 4S) should be more than adequate for contrast and contrast uniformity.

Alluxa-1A-Solex-Rug-f125-125-ASI290-17July2022-Graph-f-ratio (1).jpg (30.28 KiB) Viewed 257 times

Christian Viladrich

For a "naked" CaK filter an Edmund 394 10 nm bandpass or 400 nm short pass filter could be used to achieve additional blocking and block the H alpha peak of the DERF if needed, and a KG3 could handle the IR.

The only issue remaining after these issues for image quality are those of the objective. Your best choice is the Takahashi TOA 130 or 150, or to respace the objective of an achromatic telescope.