Lunt Calcium Offers

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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Lunt Calcium Offers

Post by Astrograph » Fri Apr 24, 2020 10:57 am

Offers from Lunt Solar!

Some excellent Calcium-K offers from Lunt have just arrived

B600 2" Straight CaK Module was £1071 Now £758
B1800 2" Straight CaK Module was £1853 Now £1309
B3400 2" Straight CaK Module was £2906 Now £1929

You just these module in the focuser and thats it. No ERF needed. All built in. Designed for scopes up to 100mm.

See details here

http://astrograph.net/epages/www_astrog ... um_Filters



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Re: Lunt Calcium Offers

Post by DeepSolar64 » Wed Apr 29, 2020 2:13 am

I just wish they had a CaH module. It's really hard for most people to see detail visually in CaK, especially if one is older. CaH is said to be a bit easier.


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Re: Lunt Calcium Offers

Post by Montana » Wed Apr 29, 2020 7:35 am

Only 3nm easier :) I can't see how it makes much difference, that is a really small shift (393nm vs 396nm) I am sure it is only down to brightness levels to the eyepiece and how the equipment is made. The Lunt CaK modules are lovely and bright. But try before you buy!

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Re: Lunt Calcium Offers

Post by Astrograph » Wed Apr 29, 2020 10:48 am

Calcium K is only for imaging. Unless you are young or have had a cataract operation you cannot see it. In any case it is in the UV band so staring at it is not a great idea!

Calcium H as offered by Daystar can be seen but its a less interesting wavelength. That filter is also 5A compared to 2.4A for the CaK modules and contrast is far worse.

The other very big issue with visual at these wavelengths is compatibility with accessories like eyepieces and diagonals.

The coatings on many eyepieces, barlows etc have a steep cutoff at 400nm and so kill the light transmission at 396 and 393nm. Baaders popular 2" clicklock diagonal has a UV/IR block on the mirror so that kills it too.

Cameras are the only way I am afraid



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Re: Lunt Calcium Offers

Post by Montana » Wed Apr 29, 2020 11:59 am

Are you saying I am young then Rupert :lol: you make me blush :) (I hope you don't think I have had a cataract operation).
I find the Lunt module views amazing, as does the hubby :)

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Re: Lunt Calcium Offers

Post by Astrograph » Wed Apr 29, 2020 12:42 pm

Hey Alexandra, surely your only in your twenties?? :D

I'm not an Ophthalmologist (but have a customer who is so maybe I will ask about this) but the human eye typically has a range of 380-740nm. The bottom of that covers the Calcium wavelengths. It should be understood that we don't see colour. Our eyes react to the photon energy in light and derive a 'colour' from that.

The lens in the eye by default blocks UV wavelengths. People who had a cataract op have no lens in the eye so they can 'detect' wavelengths down to 300nm.

However as I said, we don't 'see' the colour, it is the result of energy activating Opsin Proteins in the retina. Apparently though you need a number of Opsins to activate to trigger a signal but a high number of activation's has a tendency to reduce signal transmission.

As we get older our ability to detect shorter wavelength light diminishes by as much as 70%

All eyes are different. Some people can 'see' wavelengths at the extremes of our visible spectrum better than others regardless of age. I can see a purple / blue image with some detail via a CaK filter but its not to the same degree as the camera see's it. With H-Alpha the difference is less marked.



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Re: Lunt Calcium Offers

Post by marktownley » Wed Apr 29, 2020 2:15 pm

Astrograph wrote:
Wed Apr 29, 2020 10:48 am
The coatings on many eyepieces, barlows etc have a steep cutoff at 400nm and so kill the light transmission at 396 and 393nm. Baaders popular 2" clicklock diagonal has a UV/IR block on the mirror so that kills it too.
If you do know any (brands) that do have good transmission at CaK then spill the beans...


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Re: Lunt Calcium Offers

Post by Astrograph » Wed Apr 29, 2020 3:12 pm

Well, to be honest my current knowledge is limited by testing the Calcium Quark, Lunt CaK Modules and planetary imaging of Venus which is best done at around 350nm, plus the result of lab scope testing.

- Below 450nm most coatings are dropping off and limiting transmission. At 450nm transmission is typically 99%. At 400nm it has dropped to 88% and still falling on many optics. It places much more demands on all the other parts like the sensor, barlows etc

- Optics do not work so well below 450nm. The strehl ratio of scopes at 430nm (scope testing does not go lower than this normally) really falls off. At this point the difference between 'artisan' and mass production really tell. Two 4" class scopes I had tested, with Chinese and Russian optics, had strehl of 0.95 and 0.97 at 656nm respectively. The Chinese scope was used by a deep sky imager who loved it. At 430nm, the strehl ratio of the two scopes was 0.38 and 0.87 respectively. That is a huge difference. You get what you pay for.

- The APM 2.7x ED Barlow. This is a generally outstanding barlow that is diffraction limited right across its range. Its coatings pass CaK quite well and its been used effectively for CaK images. I seem to remember Stephen Ramsden's CaK prominence image that was highly commended in the 2014 APOTY competition used one. It is also photo visual and has a flat field up to 30mm.

- The Baader 2" Clicklock is one to avoid as it blocks UV light. I don't know about other Baader mirror diagonals. I will ask.

- The FLIR / Point Grey Blackfly with ICX692 chipset (1/3")is very good for Calcium as its QE is nearly 60% compared to more fashionable sensors that struggle to get to 45% QE at near 400nm

- I have not experimented yet but will be trying out the Pierro Astro ADC (Atmospheric Dispersion Corrector) with a CaK module as soon as the Sun returns. This uses fused silica prisms and is optimised for wavelengths down to 300nm. With planetary imaging, a good ADC makes a huge difference to image quality. As blue light is the most dispersed it should allow a significant improvement to overall sharpness of CaK images.

- I seem to remember that visually with the Calcium Quark, Televue eyepieces did not perform well. They were very dark in comparison to some others. I would need to revisit that but if my memory is good on that its down to the coatings.



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Re: Lunt Calcium Offers

Post by christian viladrich » Wed Apr 29, 2020 8:05 pm

20 years ago, I could see details visually Ca K details. Now, this is no longer the case ...

I recently made measurements of the UV transmission of various Barlow lenses. This was for observation of Venus in UV with a 320-385 nm filter and an ASI290 camera.Transmission in Ca K would be larger :
http://astrosurf.com/viladrich/astro/in ... ission.htm

ZWO is planning to offer an option for optical windows optimized for UV on their cameras.

BTW, Ca H and K are basically the same in terms of features visible.


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Re: Lunt Calcium Offers

Post by marktownley » Wed Apr 29, 2020 8:55 pm

So the APM 2.7x was the winner. Useful to know Christian.


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Re: Lunt Calcium Offers

Post by Montana » Thu Apr 30, 2020 8:03 am

Interesting info Rupert, I wonder if I used my ADC I could get my CaK to work better on my C11 without stopping down so far?

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Re: Lunt Calcium Offers

Post by Astrograph » Thu Apr 30, 2020 10:08 am

CaK on your C11? Are you using a full cover on the scope with an offset hole? I hope it also has an ERF in it as otherwise that could be very bad for the secondary.

SCT's are notoriously bad at passing blue wavelengths due to the corrector plate coating. They don't make the best scopes for imaging at sub 400nm. Certainly I would try the ADC but it will require a bit of thought as to how to set the prism because the dispersion is altitude related. I am not sure if you would be able to see the improvement onscreen.

This is one of the things I was going to explore. I have a CaK module arriving soon so this was one of the things I wanted to try. If I figure out a way to do it I will post a thread.



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Re: Lunt Calcium Offers

Post by christian viladrich » Thu Apr 30, 2020 11:05 am

There is no need to use an ADC with Ca K imaging since the bandpass of Ca K filter is very narrow.

With an filter having a bandpass smaller than 5 nm, the atmospheric dispersion is negligeable even for high resolution with a 300 mm telescope and the Sun 15° above the horizon.


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Re: Lunt Calcium Offers

Post by Astrograph » Thu Apr 30, 2020 11:28 am

That is logical Christian. This is more a personal test of my own to satisfy curiosity.



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Re: Lunt Calcium Offers

Post by Montana » Thu Apr 30, 2020 1:32 pm

Yep, I have a Valery filter on the front (Aries) :)

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Re: Lunt Calcium Offers

Post by DeepSolar64 » Thu Apr 30, 2020 3:53 pm

I have worn glasses since I was 4 years old and since 1980 UV activated Photogrey lenses and now Transitions lenses that block a lot of UV light from reaching my eyes. I have wondered if these might slow or stop yellowing of my eyes lenses and increase the chance of me being able to see CaK? If I could only find a way to try one and see.

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Re: Lunt Calcium Offers

Post by MapleRidge » Fri May 08, 2020 2:04 am

Just a quick comment on visual CaK.

Prior to cataract surgery my visual views through the Lunt B1200CaK or B1800Cak on a variety of scopes was nothing more than a deep blue smudge...could not even make out the limb/sky line to tell if the sun was close to centered.

Post cataract surgery in my right eye (2015 or so), the right eye sees CaK sharp, just like WL to the non enhanced eye.

Still, I'll stick to imaging and not do any more UV damage to the eye than I can help!

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Re: Lunt Calcium Offers

Post by DeepSolar64 » Fri May 08, 2020 6:44 am

I wonder if there is any real danger to the eye with viewing CaH and Cak if one is visually capable of doing so? Both are close to the borderline of violet and ultraviolet. It's a moot point with most people since they cannot see it anyway but those who have had cataract surgery can. And some young people. Is there a real danger visually? Brian, there is nothing wrong with being cautious.

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Re: Lunt Calcium Offers

Post by Astrograph » Fri May 08, 2020 9:23 am

I would speak to an ophthalmologist if unsure. Your eye does not 'see' anything. Proteins react to different amounts of energy and send signals in the retina. There are so many other obstacles with viewing calcium (like coatings on eyepieces) that its better to just treat it as an imaging wavelength.



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Re: Lunt Calcium Offers

Post by Solar B » Fri May 08, 2020 11:15 am

James

I do think the calcium wavelengths are worth looking 😉 into , however as always caution is

advised.

My own experience at 495nm is very limited .... approx 14 yrs ago I did have a Cak PST ... couldn't

see a thing but it was amazingly good for imaging .... around the same time I obtained one of

the Baader Cak filters and I can't remember what exactly I did but I placed this filter in

combination with an AE solarvue2 H wedge where approx 5% of the suns light was still hitting it

the result was probably the brightest Cak image ever viewed 💙 it was incredible but pure UV

& highly dangerous ... I only tried this once and obviously wouldn't recommend any else to 💀

Brian


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