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.
Post Reply
User avatar
MalVeauX
Ohhhhhh My!
Ohhhhhh My!
Posts: 104
Joined: Tue May 09, 2017 7:58 pm
Location: Florida

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,

User avatar
Montana
Way More Fun to Share It!!
Way More Fun to Share It!!
Posts: 17775
Joined: Mon Oct 17, 2011 5:25 pm
Location: Cheshire, UK

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

User avatar
MalVeauX
Ohhhhhh My!
Ohhhhhh My!
Posts: 104
Joined: Tue May 09, 2017 7:58 pm
Location: Florida

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,

User avatar
krakatoa1883
Oh, I get it now!
Oh, I get it now!
Posts: 31
Joined: Sat Jun 11, 2016 9:41 am

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.

Best.
Raf
My personal page on Google+

User avatar
MalVeauX
Ohhhhhh My!
Ohhhhhh My!
Posts: 104
Joined: Tue May 09, 2017 7:58 pm
Location: Florida

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.

Very best,

User avatar
Montana
Way More Fun to Share It!!
Way More Fun to Share It!!
Posts: 17775
Joined: Mon Oct 17, 2011 5:25 pm
Location: Cheshire, UK

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


User avatar
MalVeauX
Ohhhhhh My!
Ohhhhhh My!
Posts: 104
Joined: Tue May 09, 2017 7:58 pm
Location: Florida

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,

User avatar
DSobserver
Almost There...
Almost There...
Posts: 520
Joined: Sun Feb 19, 2012 2:36 pm
Location: FRANCE

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?

christian viladrich
Im an EXPERT!
Im an EXPERT!
Posts: 215
Joined: Sun Jun 14, 2015 4:46 pm
Location: France
Contact:

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
Christian Viladrich
Co-author of "Astronomie Planétaire"
http://www.astroplanetes.com/

User avatar
Carbon60
Way More Fun to Share It!!
Way More Fun to Share It!!
Posts: 4272
Joined: Wed Mar 07, 2012 12:33 pm
Location: Lancashire, UK

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.

Stu.
Lunt LS60THa B1200 PTFT
150mm H-alpha Solar telescope with Lunt35 mod
DMK41, Basler acA1920-155
NEQ6 Pro-mount
Fluxgate Magnetometers (1s and 150s Cadence)
More images at http://www.flickr.com/photos/solarcarbon60/

User avatar
MalVeauX
Ohhhhhh My!
Ohhhhhh My!
Posts: 104
Joined: Tue May 09, 2017 7:58 pm
Location: Florida

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,

User avatar
Astrograph
Ohhhhhh My!
Ohhhhhh My!
Posts: 175
Joined: Tue Aug 05, 2014 1:00 pm
Location: London
Contact:

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.

User avatar
MalVeauX
Ohhhhhh My!
Ohhhhhh My!
Posts: 104
Joined: Tue May 09, 2017 7:58 pm
Location: Florida

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,

User avatar
krakatoa1883
Oh, I get it now!
Oh, I get it now!
Posts: 31
Joined: Sat Jun 11, 2016 9:41 am

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 557 times
sun20170609_CaH_dett2.jpg
sun20170609_CaH_dett2.jpg (42.83 KiB) Viewed 557 times
Raf
My personal page on Google+

User avatar
MalVeauX
Ohhhhhh My!
Ohhhhhh My!
Posts: 104
Joined: Tue May 09, 2017 7:58 pm
Location: Florida

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,

User avatar
Montana
Way More Fun to Share It!!
Way More Fun to Share It!!
Posts: 17775
Joined: Mon Oct 17, 2011 5:25 pm
Location: Cheshire, UK

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 :)
Alexandra

User avatar
MalVeauX
Ohhhhhh My!
Ohhhhhh My!
Posts: 104
Joined: Tue May 09, 2017 7:58 pm
Location: Florida

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!

Very best,

User avatar
Astrograph
Ohhhhhh My!
Ohhhhhh My!
Posts: 175
Joined: Tue Aug 05, 2014 1:00 pm
Location: London
Contact:

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.

Derek Klepp
Way More Fun to Share It!!
Way More Fun to Share It!!
Posts: 11765
Joined: Wed Oct 19, 2011 10:02 am

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.
Derek

User avatar
Valery
Way More Fun to Share It!!
Way More Fun to Share It!!
Posts: 2421
Joined: Sun Nov 18, 2012 3:13 pm

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


Valery
"Solar H alpha activity is the most dynamic and compelling thing you can see in a telescope, so spend accordingly." (c) Bob Yoesle.

Largest full size 185 - 356mm Dielectric Energy Rejection Filters (D-ERF) by ARIES Instruments.

User avatar
Astrograph
Ohhhhhh My!
Ohhhhhh My!
Posts: 175
Joined: Tue Aug 05, 2014 1:00 pm
Location: London
Contact:

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 :)

User avatar
marktownley
Librarian
Librarian
Posts: 22039
Joined: Tue Oct 18, 2011 5:27 pm
Location: Brierley Hills, UK
Contact:

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!
Image
http://brierleyhillsolar.blogspot.co.uk/
Solar images, a collection of all the most up to date live solar data on the web, imaging & processing tutorials - please take a look!

User avatar
marktownley
Librarian
Librarian
Posts: 22039
Joined: Tue Oct 18, 2011 5:27 pm
Location: Brierley Hills, UK
Contact:

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?
Image
http://brierleyhillsolar.blogspot.co.uk/
Solar images, a collection of all the most up to date live solar data on the web, imaging & processing tutorials - please take a look!

User avatar
Astrograph
Ohhhhhh My!
Ohhhhhh My!
Posts: 175
Joined: Tue Aug 05, 2014 1:00 pm
Location: London
Contact:

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.

User avatar
Valery
Way More Fun to Share It!!
Way More Fun to Share It!!
Posts: 2421
Joined: Sun Nov 18, 2012 3:13 pm

Re: Different Ca-K options, differences?

Post by Valery » Wed Jun 14, 2017 6:14 pm

Mark,

For Ca K and Ca H the best refractors are TOA 130 and 150. All other refractors regardless of manufacturer are poorly corrected at these wave lengths.

If you can use a 6" F/12 achromat, you will be OK with crisp images at Ca K/H. But such a scope is not quite transportable and not easy useable.

Another, best (IMHO) solution is a Marksutov telescope.

Any coating is OK.


Valery
"Solar H alpha activity is the most dynamic and compelling thing you can see in a telescope, so spend accordingly." (c) Bob Yoesle.

Largest full size 185 - 356mm Dielectric Energy Rejection Filters (D-ERF) by ARIES Instruments.

User avatar
Astrograph
Ohhhhhh My!
Ohhhhhh My!
Posts: 175
Joined: Tue Aug 05, 2014 1:00 pm
Location: London
Contact:

Re: Different Ca-K options, differences?

Post by Astrograph » Wed Jun 14, 2017 10:25 pm

Valery, where is the basis for TOA scopes being so wonderful at sub 400nm? They are just pretty ordinary APO's using ordinary glass. Nothing more.

Any coating is not OK. For proof of this see this wavelength test between the Pierro Astro ADC and the cheap ZWO. The PA has fused silica prisms which pass sub 400nm light better and coatings that are designed to compliment this. The difference is quite obvious.

In any case we are getting away from how this thread started.
Attachments
PA - ZWO ADC.jpg
PA - ZWO ADC.jpg (111.21 KiB) Viewed 380 times

User avatar
Merlin66
Librarian
Librarian
Posts: 2855
Joined: Tue Dec 13, 2011 1:23 pm
Location: St Leonards, Australia
Contact:

Re: Different Ca-K options, differences?

Post by Merlin66 » Thu Jun 15, 2017 11:27 am

Does it really matter?
The current CCD cameras dramatically fall in sensitivity in the UV.
The shortest wavelength I've been able to record with the spectroscope is just below 3700A.
"Astronomical Spectroscopy - The Final Frontier" - to boldly go where few amateurs have gone before
https://groups.yahoo.com/neo/groups/ast ... scopy/info
"Astronomical Spectroscopy for Amateurs" and
"Imaging Sunlight - using a digital spectroheliograph" - Springer

User avatar
Valery
Way More Fun to Share It!!
Way More Fun to Share It!!
Posts: 2421
Joined: Sun Nov 18, 2012 3:13 pm

Re: Different Ca-K options, differences?

Post by Valery » Thu Jun 15, 2017 7:08 pm

Astrograph wrote:
Wed Jun 14, 2017 10:25 pm
Valery, where is the basis for TOA scopes being so wonderful at sub 400nm? They are just pretty ordinary APO's using ordinary glass. Nothing more.
Rupert,

Please, no offence. You are not a pro, nor a specialist in the optics as far as I know. But I am.

The basis for TOA scopes being so perfectly corrected is in the design of these objectives. TOA states for Triplet Ortho Apochromat = triplet with equal (close to this) apochromatic correction across spectrum. They are not only corrected for secondary spectrum (common focus for wide spectral range) but they also corrected for spherical aberration for almost entire spectral range they are purposed for. In the ordinary apochromats spherical aberration is corrected only for a single wave length. Usually this is 540nm and near it. In the TOA objectives spherical aberration corrected for ALL wave lengths. Therefore images at 400nm is same crisp as at, say, 540nm and even crisper because of lower diffraction influence.
Similar designs (with widely spaced lenses) are well known for optical designers for a loooong time. The only disadvantage is a poor temperature equilibration with enviromental air. This is a key factor and most designers prefer lower corrected objectives, but with much faster thermal equlibration. Somewhen in a past we have discussed these questions with Roland and Yuri. They too are not fans of orthoapochromatic objectives because of this mentioned above disadvantage. But for a Ca K imaging they are almost a perfect choice in such a size.

Again, for 400nm +/- several tens of nanometers, all coatings are about similar performance +/- a few % in transmission. Of course if an objective consists many lenses with lower transmission in UV, then a final transmission will be about 20% lower - absolutely not critical for imaging there.


Valery.
Last edited by Valery on Sun Jun 18, 2017 11:50 am, edited 1 time in total.
"Solar H alpha activity is the most dynamic and compelling thing you can see in a telescope, so spend accordingly." (c) Bob Yoesle.

Largest full size 185 - 356mm Dielectric Energy Rejection Filters (D-ERF) by ARIES Instruments.

User avatar
Astrograph
Ohhhhhh My!
Ohhhhhh My!
Posts: 175
Joined: Tue Aug 05, 2014 1:00 pm
Location: London
Contact:

Re: Different Ca-K options, differences?

Post by Astrograph » Thu Jun 15, 2017 11:12 pm

Valery. I take a pride in helping people to try and understand the reality of what is out there rather than back up marketing BS. Many things look great on paper. In the real world what is delivered is often nowhere near. That applies to Tak as much as any other. TOA's, regardless of their design strategy set no new heights for performance. Being replaced by customers for something better is not uncommon. I don't dispute that in theory it might be better but there are many designs out there that promise much and deliver little new, if anything. Design is one thing, implementing it is another and doing it consistently is another still. I see this all the time. It is constantly frustrating that something that seems so simple as some shaped and polished glass put together can vary so widely in performance on a case by case basis with the same telescope. I see this because I inspect all I sell. What becomes clear is that who makes it is much more important than how or what it is made from.

I am well aware of your own experience and qualifications with optics. I feel no need to question that. You know nothing about me so please don't insult me. I run a professional astronomy business.

User avatar
marktownley
Librarian
Librarian
Posts: 22039
Joined: Tue Oct 18, 2011 5:27 pm
Location: Brierley Hills, UK
Contact:

Re: Different Ca-K options, differences?

Post by marktownley » Fri Jun 16, 2017 8:54 am

Good discussion chaps.

I've certainly tried all of the CaK options above, and my preferred one is a double stacked CaK PST filter of my own design. If I had to pick from an 'off the shelf' unit I would go for a CaH quark, if cost was no objective I would go with the Lunt B3400 or maybe a custom job from Solar Spectrum.

In terms of scopes i've only ever used 'budget' cheap refractors with CaK and there is significant variance in light throughput (different scopes, same focal ratios, same camera, same day), this can only be glass types or coatings causing the variance. When I reviewed the CaH Quark there was significant variance in brightness visually using different eyepieces. These are just my observations.

As i've become more experienced with my solar imaging i've learned to see the results of spherical aberration when imaging at CaK wavelengths, and, as above there is significant variation between scopes.

I certainly don't have the experience of using the higher end scopes that both Valery and Rupert have, but, being a nerd I do enjoy reading test reports and so I take something from these (and I do appreciate a test report isn't everything!).

For me, in the less than ideal seeing I have a lot of the time, a dream scope for me would be a 5-7" frac and a tri-band (full aperture) ERF, but it would have to cut the mustard at 393nm. To get to that point though I do need to win the lottery! :D
Image
http://brierleyhillsolar.blogspot.co.uk/
Solar images, a collection of all the most up to date live solar data on the web, imaging & processing tutorials - please take a look!

User avatar
MalVeauX
Ohhhhhh My!
Ohhhhhh My!
Posts: 104
Joined: Tue May 09, 2017 7:58 pm
Location: Florida

Re: Different Ca-K options, differences?

Post by MalVeauX » Sat Jun 17, 2017 9:59 pm

Hi all,

Just a little update.

I'm tinkering with a Skybender with a 380~395nm pre-filter inside, IR rejection filter on the nose, and two 393nm filters stacked on the camera nose. I used a focal reducer to do the full disc. And I used a 3x barlow for the details. I did some white light too just to compare (white light was done with a baadar solar film & solar continuum filter).

Image

Image

Image

Image

Image

What do you guys think? Close? Or is it mainly just white light that looks like it, but not really calcium?

++++++++++++++++++++++++++++

The skybender itself and the filters:

Image

Image

Image

Very best,

User avatar
marktownley
Librarian
Librarian
Posts: 22039
Joined: Tue Oct 18, 2011 5:27 pm
Location: Brierley Hills, UK
Contact:

Re: Different Ca-K options, differences?

Post by marktownley » Sun Jun 18, 2017 8:10 am

Hi Marty. One of those 393 filters needs to be mounted internally in the skybender - at the moment all it is doing is acting as an extension tube. Apollo has had some success with these setups in CaK.
Image
http://brierleyhillsolar.blogspot.co.uk/
Solar images, a collection of all the most up to date live solar data on the web, imaging & processing tutorials - please take a look!

User avatar
MalVeauX
Ohhhhhh My!
Ohhhhhh My!
Posts: 104
Joined: Tue May 09, 2017 7:58 pm
Location: Florida

Re: Different Ca-K options, differences?

Post by MalVeauX » Sun Jun 18, 2017 12:17 pm

Hi Mark,

The filter inside the tube is a 380~395nm pre-filter. Then the two 393nm filters. Do you think the pre-filter should be exchanged to one of the 393 filters and then just one 393 on the nose of the camera?

I can see through the 393 filters, but I cannot see through the 380~395, it looks like a mirror on both sides when I take it out and look at it.

Very best,

User avatar
marktownley
Librarian
Librarian
Posts: 22039
Joined: Tue Oct 18, 2011 5:27 pm
Location: Brierley Hills, UK
Contact:

Re: Different Ca-K options, differences?

Post by marktownley » Sun Jun 18, 2017 12:36 pm

I would try a 393 on the 380~395 filter, but, if apollo recommends the configuration it is in go with it.
Image
http://brierleyhillsolar.blogspot.co.uk/
Solar images, a collection of all the most up to date live solar data on the web, imaging & processing tutorials - please take a look!

User avatar
MalVeauX
Ohhhhhh My!
Ohhhhhh My!
Posts: 104
Joined: Tue May 09, 2017 7:58 pm
Location: Florida

Re: Different Ca-K options, differences?

Post by MalVeauX » Sun Jun 18, 2017 1:56 pm

Yea, I'm only setup this way because that's how he suggested it be used. I didn't notice much difference tilting though. I'm curious if putting the 380~395 on the nose with the IR rejection and then putting a 393 in the tilter and a 393 on the camera would be more appropriate?

I'm trying it out as I didn't buy it, just seeing if there are alternatives to the $1k options (Lunt, Quark) since there really isn't a lot of Ca options out there really, compared to HA. Really bummed the PST CaK is no longer made, as that would have been ideal for me I think for cost.

Long term, I can't decide if a Quark CaH or a Lunt CaK BF would be ideal. I think ultimately I will stay within refractors of 6 inches or less for this, simply due to cost of moving into a big aperture SCT and the ERF required, etc. It's just too costly. I can however manage 6 inch refractors. I'm just not sure if the Lunt BF1200 would be best, if I put a 3x or 5x barlow on the 150mm refractor (one day at least), or if a Quark CaH unit would be more appropriate for something like that. I would like to be able to do full disc and high mag with the device. The Quark CaH still seems to need long focal ratios but at least lacks the barlow so I could do full disc with that. But the Lunt is attractive as well. Just not sure what would really be ideal for imaging (I do 1% visual, with a PST, just to look for morning proms basically).

Very best,

User avatar
Montana
Way More Fun to Share It!!
Way More Fun to Share It!!
Posts: 17775
Joined: Mon Oct 17, 2011 5:25 pm
Location: Cheshire, UK

Re: Different Ca-K options, differences?

Post by Montana » Mon Jun 19, 2017 6:59 am

Wow! I think these images are fantastic! lovely and crisp and lots of plage seen around the spots in the centre of the disc. That is impressive! what aperture is the scope and what are the 393 filters?

:hamster: :bow

Alexandra

User avatar
Astrograph
Ohhhhhh My!
Ohhhhhh My!
Posts: 175
Joined: Tue Aug 05, 2014 1:00 pm
Location: London
Contact:

Re: Different Ca-K options, differences?

Post by Astrograph » Mon Jun 19, 2017 9:21 am

Personally I think you would be better off with the Lunt CaK module is you can just use it with no extra costs and it will work. The Daystar CaH will require an ERF of some kind. Although I have used it on an F6.5 scope visually and it looked 'ok' it really needs to be at least double that. An important consideration with the Daystar is back focus. If you add a telecentric then things can be made to work because the focal point gets moved further back. If you want to use it on its own then your scope must have enough back focus to accommodate the Quark and still allow focus. On many Chinese scopes there is not enough back focus (and hence inward movement on the focuser) to reach focus. This is not an issue with the Lunt as it is fitted internally.

User avatar
MalVeauX
Ohhhhhh My!
Ohhhhhh My!
Posts: 104
Joined: Tue May 09, 2017 7:58 pm
Location: Florida

Re: Different Ca-K options, differences?

Post by MalVeauX » Mon Jun 19, 2017 1:24 pm

Montana wrote:
Mon Jun 19, 2017 6:59 am
Wow! I think these images are fantastic! lovely and crisp and lots of plage seen around the spots in the centre of the disc. That is impressive! what aperture is the scope and what are the 393 filters?

:hamster: :bow

Alexandra
Thanks!

Scope is 120mm refractor (Celestron Omni XLT 120; F8.3). The 393nm filters are just 1.25" filters that I received with the Skybender. I'm not sure about their make/origin. Maybe Semrock?
Astrograph wrote:
Mon Jun 19, 2017 9:21 am
Personally I think you would be better off with the Lunt CaK module is you can just use it with no extra costs and it will work. The Daystar CaH will require an ERF of some kind. Although I have used it on an F6.5 scope visually and it looked 'ok' it really needs to be at least double that. An important consideration with the Daystar is back focus. If you add a telecentric then things can be made to work because the focal point gets moved further back. If you want to use it on its own then your scope must have enough back focus to accommodate the Quark and still allow focus. On many Chinese scopes there is not enough back focus (and hence inward movement on the focuser) to reach focus. This is not an issue with the Lunt as it is fitted internally.
I have no issue with backfocus; I use straight-through, no diagonals, and my focuser is linear bearing and I use assortments of extensions to get focus with my current telecentric barlow in my Quark no problem.

Interesting, didn't realize the Quark CaH would need an ERF. I read it just needed the standard UV/IR cutter just like the other Quarks for heat rejection, but beyond that, just had to be at F7 or greater and it was good to go. Unless my understanding is incorrect?

Ultimately I too think the Lunt is the way to go in the long run for CaK for me, if I get to that point. I will keep using this Skybender setup for a little while and see what I can get out of it before moving to something else. I'd love to have both just to compare and see if one really is superior with my setup or not. I like my Quark Chromosphere, but I definitely appreciate the idea of not needing another powered device to manage.

Do you think the B1200 would be a limitation with a 3x or 5x barlow on a 1,000mm scope (120mm aperture, F8.3) using an ASI174MM?

Very best,

User avatar
Astrograph
Ohhhhhh My!
Ohhhhhh My!
Posts: 175
Joined: Tue Aug 05, 2014 1:00 pm
Location: London
Contact:

Re: Different Ca-K options, differences?

Post by Astrograph » Mon Jun 19, 2017 2:18 pm

Hi,

To clarify the back focus comment. A telecentric adds backfocus. You need a telecentric (not a barlow) to allow an etalon to operate correctly and onband. The Quark Calcium does not have a telecentric as its bandpass is wide and scopes from F8 should be OK. The problem is that inserting the Quark Calcium into the light path uses up what back focus you have. With some scopes you will not get focus. You don't need extensions, you need a scope whose focuser retracts further inwards. This is not a factor with the Lunt as it has a collimating lens inside.

The Quark Calcium has a block in it nose which allows no ERF below about 60mm. Above that you can use an UV/IR cut but a 120mm scope needs some better. A Baader blue filter is best as this passes the calcium wavelength. It is also dielectric so reflects energy. The Lunt needs nothing as its ERF is built into the front of it.

I have used a B1200 (this refers to the 12mm size of the block) with an 800mm scope. That was OK. The diagonal of your 173 is just over 13mm so you would get some vignetting. Just use ROI. Don't wast money on a B1800

User avatar
MalVeauX
Ohhhhhh My!
Ohhhhhh My!
Posts: 104
Joined: Tue May 09, 2017 7:58 pm
Location: Florida

Re: Different Ca-K options, differences?

Post by MalVeauX » Mon Jun 19, 2017 2:58 pm

Hi thanks, makes sense. The Quark Calcium sounds more fussy than the Quark Chromosphere!

Lunt sounds more simple. I don't mind a little vignetting. Thanks!

Very best,

Post Reply

Who is online

Users browsing this forum: Garrybluebot and 1 guest