Different Ca-K options, differences?

Use this section to discuss "standard" Baader/Coronado/ Lunt SolarView/ Daystar, etc… filters, cameras and scopes. No mods, just questions/ answers and reviews.
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Different Ca-K options, differences?

Post by MalVeauX » Sun May 28, 2017 4:34 pm

Hey all,

I have HA covered for now. And white light covered for now.

I'm interested in adding Ca-K to my line up.

I'm curious though, what are the differences between these options, or is there really any difference:

Quark Ca-H-line - $1k
Lunt Ca-K module - $700~2k
Baader Ca-K II filter (requires white light filter in addition) - $350

What are the Quark/Lunt systems doing with Ca-K wavelength that a white light setup and baader Ca-K filter are not doing?

++++++++++

I have:

Quark Chromosphere (HA)
Baader Astro Solar Film (White Light) filter
Baader Solar Continuum filter
ASI174MM

Looking for an option to bring Ca-k into the fold.

Very best,

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Re: Different Ca-K options, differences?

Post by Montana » Sun May 28, 2017 6:26 pm

A Baader CaK filter is no good, it is barely faculae on white light. I think it is 80A wide from what I remember. You need 2A wide for decent CaK imaging. A Lunt CaK wedge is the way to go unless you can find a used Coronado CaK PST. I have had a bad experience with Daystar so I can't say anything about that.

Alexandra

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Re: Different Ca-K options, differences?

Post by MalVeauX » Sun May 28, 2017 6:31 pm

Thanks,

I figured there was something that was truly different. So the filter is basically pointless and costly.

Looks like I'll have to pinch pennies to get a good Ca-K filter. Will hold off for now then.

Very best,

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Re: Different Ca-K options, differences?

Post by krakatoa1883 » Mon May 29, 2017 11:13 am

If you look at my Google+ page linked below you can see some images I made with my Baader K filter and compare it to images taken through a more expensive Ca-K module. The filter is not bad, but as Alexandra points out it has a 80 A wide band so it delivers less contrast and less detail compared to the Lunt module.

If you can then go with the Lunt, but if money matters you may also consider the filter in spite of its limits.

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Re: Different Ca-K options, differences?

Post by MalVeauX » Tue May 30, 2017 1:06 pm

Hrm,

Seems the Baader filter really isn't worth while. Just looks like white light with a bit more contrast around the faculae. Not good enough for $350.

I'm curious about the Lunt CaK module. I'm curious how it has a narrow band pass, blocking filter, etc, in that diagonal blocking filter, without an etalon, no power source, no tuning, etc. Compared to something like the Quark CaH which has tuning and all that. I guess I'm curious because CaK is the chromosphere and also ultra narrowband, so why is it different than Halpha for example in terms of only needing a blocking filter wedge and not requiring an etalon and blocking filter and all that.

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Re: Different Ca-K options, differences?

Post by Montana » Tue May 30, 2017 1:48 pm

I'm no expert but both the Lunt and Coronado filters are just filters (with coatings) to achieve the narrow band pass. Nothing special is needed, 2.4A (Lunt) and 2.2A (Coronado) is still very wide when it comes to band pass. Remember the special hydrogen alpha filter is made as such to achieve 0.3-0.7A wide (that is narrow). The Quark CaH filter just works in a completely different way, I think in a similar way to their Halpha filter, but I am sure I read somewhere that it is 5A wide, but then the Calcium H band is very wide (relatively) compared to the others. If you read Christian V's most recent post I asked where his filter was from and it was from filter company I have not heard off but it seems to have done a brilliant job viewtopic.php?f=4&t=22556 . You can also buy Calcium K filters from Omega Bob of Ebay but you really do need 2 to double stack them. My CaH filter from him is 5A wide and not really very good.
You will not be disappointed with the Lunt wedge, it is just point and shoot, no tuning required for this wavelength.

Alexandra


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Re: Different Ca-K options, differences?

Post by MalVeauX » Tue May 30, 2017 5:30 pm

Thanks for the links,

There seems to be so much vague information and very little concrete with photos in the same place. In one spot you can get a great photo and vague information about the equipment. In another, there's charts and read outs on the equipment, but no photos. I get that CaK is more of an imaging wavelength, and I'm not interested in visual anyways as I'm always looking through a camera to do it regardless.

I would just think there's other options other than $1k modules like the Lunt/Quark out there. The PST CaK is discontinued and not available. There are scopes dedicated to CaK from the major manufacturers, but I'd definitely rather have a module design to move between scopes over time.

Very best,

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Re: Different Ca-K options, differences?

Post by DSobserver » Fri Jun 02, 2017 5:58 am

Visually à lunt cak filter is impressive!

You can't use high magnification otherwise it becomes too dark but you can easily see the famous structures.
Only bright prom are visually detectable
I use it with a 90mm scope

I remember in the past that visually it was impossible to see something with Coronado one

There is nothing vague. What do you want to know?

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Re: Different Ca-K options, differences?

Post by christian viladrich » Fri Jun 02, 2017 7:25 pm

Hi,
Just a quick input there : the Baader K line filter is not a Ca K filter nor a Ca H filter. As explained by Alexandra, its bandpass is so large that it includes both Ca K and Ca H lines.

Here is a comparision between a K line filter :
Image

and a Ca K filter :
Image

I've got another one here :
http://www.astrosurf.com/viladrich/astr ... -Kline.jpg
http://www.astrosurf.com/viladrich/astr ... 63-Cak.jpg

This being said the K line filter is still useful (compared to green or red filters) for the three reasons :
1) the contrast of the granulation (and of sunspots) increases when the wavelength decreases. In other words, we have more contrast in blue light than in red light,
2)the diffraction decreases (ie. resolution increases) when the wavelength decreases,
3) this is a narrow band filter (8 to 10 FWHM), so there is no more issue with atmospheric dispersion.

Compare for example this image at 540 nm (so called Baader continuum filter):
Image

with this one at 396 nm (Baader K line):
Image
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Re: Different Ca-K options, differences?

Post by Carbon60 » Sat Jun 03, 2017 5:56 am

A very informative thread. Thanks guys.

Like all things, you get what you pay for, Marty. I can recommend the Lunt CaK module.

Good comparisons and info Christian.

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Re: Different Ca-K options, differences?

Post by MalVeauX » Sat Jun 03, 2017 4:22 pm

Thanks Christian, that helps with a lot of questions.

Great comparisons too. It looks like the K-line filter is still better than just a Continuum filter, I can see the faculae better for sure, and the contrast and resolution looks much better. Though, at $350 for that filter versus the $50 I got the continuum for, I think ultimately its better to just put that money towards a Ca-K module that is real, and not just the K-line filter.

Very best,

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Re: Different Ca-K options, differences?

Post by Astrograph » Thu Jun 08, 2017 3:29 pm

To add my two pennies worth.

The Daystar H Line is as much for visual as imaging. It needs to be used with an ERF. You can use an Astronomik UV/IR cut as this has a window for calcium or a Baader Blue filter. You can't use a Baader UV/IR as it blocks below 400nm. The Daystar works OK even at F8 but really needs a 2x Barlow. You have to be careful with your choice of eyepiece / barlow as the coatings on some block sub 400nm heavily. Some scopes also will not have enough in focus without using a tele-centric (and then you have the coating issue to contend with). The new Baader TZ-3 is known to work well with Calcium but I know the other models don't. The H Line is more blue than the purple of K and does not seem to offer the same sort of prominence visibility as K. Alexandra is right that its bandpass is 5A

The Lunt CaK module is very easy to use with any refractor. The module is a tube that fits inside the focuser. It has a rejection filter on the end of it so you need nothing else. The B1200 version seems to work with everything. You can add a barlow to it but you need to be careful for the reasons outlined above. The APM 2.7x is a good choice as it as nearly 99% transmission at 400nm and works well in the Calcium wavelengths. It is 2A bandpass. You can use it with the K Line as a sort of cheap DS but I don't think its ideal. Proms are visible when you expose just for them.

The Baader K Line filter is alright I think. Its not cheap but it does offer a big contrast boost. You can use it in a wedge (but remove the ND3) or with solar film and also as an add on for the Lunt. One thing to be careful of is getting a bad one. The filter is two filters and if they are misaligned then you get double or even triple images. If you see this, send it back.

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Re: Different Ca-K options, differences?

Post by MalVeauX » Fri Jun 09, 2017 12:02 am

Thanks for the info,

Overall, if I ever buy something for Calcium, I will probably go for the Lunt module. It just makes sense and I'm not going to be getting a big ERF any time soon. I'd love to just get a PST CaK but I guess those are super rare these days and discontinued. The Lunt has a massive wait time, but I'd rather get it used anyways from someone getting out of it. We will see. I have a few little filters I'm going to experiment with in the mean time and just watch the market for a while and see if a Lunt shows up.

Very best,

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Re: Different Ca-K options, differences?

Post by krakatoa1883 » Fri Jun 09, 2017 7:25 pm

I agree with Astrograph. I just purchased a Quark H and I found it complements well my Baader K that I keep for imaging granulation as it provides more contrast than Baader Continuum. For me it has an advantage compared to the Lunt module: I can use it not only with my refractor but also my solar newtonian that can be safely used at full aperture. Same with the K filter.
20170607_CaH.jpg
20170607_CaH.jpg (57.57 KiB) Viewed 3085 times
sun20170609_CaH_dett2.jpg
sun20170609_CaH_dett2.jpg (42.83 KiB) Viewed 3085 times
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Re: Different Ca-K options, differences?

Post by MalVeauX » Sat Jun 10, 2017 2:09 am

Thanks, Very nice!

Good point about the Quark and being able to use it with non-refractors. Ultimately one day I want a 9.25" SCT. But then again, I don't think I'll ever afford the ERF's needed for such an aperture; especially two separates one for CA and one for HA. Sigh. So maybe I should keep it simple with smaller apertures of 5 inches and call it a lifetime lol. Guess we'll see what comes up for sale first, and for what price, as that always tends to dictate it for me. I don't buy new.

Very best,

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Re: Different Ca-K options, differences?

Post by Montana » Sat Jun 10, 2017 10:00 am

Well, Valery sells large aperture ERFs that have a gap at CaK, WL and Halpha so you only need one :)
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Re: Different Ca-K options, differences?

Post by MalVeauX » Sat Jun 10, 2017 2:44 pm

That would be great, if I ever got a big enough scope to warrant it, but for now, I dont' think I'll be venturing over 5 inches for a while. Getting the 9.25", the D-ERF, the calcium module, and the cost to mod the 9.25" with a PST etalon (at the very least) will be like a $5k+ expense. Not quite ready for that! Maybe when I retire!

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Re: Different Ca-K options, differences?

Post by Astrograph » Sat Jun 10, 2017 3:18 pm

The Airylab HaT and the new 235mm D-ERF will allow Ha and WL. Calcium with an SCT is pointless as they are very poor at sub 400nm wavelengths.

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Re: Different Ca-K options, differences?

Post by Derek Klepp » Mon Jun 12, 2017 4:09 am

Mal for starters the Lunt B1200 wedge should get you good results with your 120mm scope. I have had great success with mine on both an 80 mm f11 scope and a 5" f7.5apo.Don,t worry about the Baader CaK to start off with.
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Re: Different Ca-K options, differences?

Post by Valery » Tue Jun 13, 2017 9:32 am

Astrograph wrote:
Sat Jun 10, 2017 3:18 pm
The Airylab HaT and the new 235mm D-ERF will allow Ha and WL. Calcium with an SCT is pointless as they are very poor at sub 400nm wavelengths.
Hi Rupert,

SCTs are not so bad at Ca K and Ca H ! They at least better at Ca K than at H-a resolution wise.
With additional corrective optics (special SAFIX or special Barlow) it will be perfect even at Ca K&H.

See here: viewtopic.php?f=4&t=22680


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Re: Different Ca-K options, differences?

Post by Astrograph » Tue Jun 13, 2017 10:25 am

I can only comment on results with my own eyes Valery. Planetary imagers all over the world suffer with poor blue / UV band images using SCT's. Images are not terrible but they are not the quality of other wavelengths. Corrective optics may help but they are not freely available. You should change that :)

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Re: Different Ca-K options, differences?

Post by marktownley » Tue Jun 13, 2017 6:20 pm

Astrograph wrote:
Tue Jun 13, 2017 10:25 am
You should change that :)
I agree!
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Re: Different Ca-K options, differences?

Post by marktownley » Tue Jun 13, 2017 9:26 pm

Astrograph wrote:
Tue Jun 13, 2017 10:25 am
Planetary imagers all over the world suffer with poor blue / UV band images using SCT's. Images are not terrible but they are not the quality of other wavelengths.
I totally agree Rupert. What refractors do you recommend as the top performers in the deep blue (CaK) wavelengths?
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Re: Different Ca-K options, differences?

Post by Astrograph » Tue Jun 13, 2017 10:41 pm

The issue with most is coatings Mark. By design they pass the visible wavelengths and normally have a severe cut lower than 400nm. Reflectors have a double wammy as the mirror coating is often limited in its reflectivity at different wavelengths. Something like an SCT then has a coating on its corrector. As you know from testing the Calcium H Quark, eyepieces etc with odd coatings make a huge difference to what you see.

I know with LZOS refractor optics that there is something like a 50% loss in transmission at the UV wavelengths but as low as 486nm they are still efficient and way above diffraction limited (0.96 actually). In theory an oilled CaF2 refractor like a TEC would be best because CaF2 is very transparent to UV wavelengths and because of the oilling the optics are uncoated internally so you get max transmission of these wavelengths. There is only coating on the front element.

So basically an oilled CaF2 Refractor that is made properly should be best. A TEC is the only current choice. The only others are older AP and Zeiss APQ's. These makes all acquired the skill to make oilled scopes reliably.

Downside is an APQ is now priced so high its for collectors only. First CaF2 TEC is the 160. Yours for £14K sir.

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