First Light Report ..Coronado CaK PST..

[Greg]

First Light Report. Cak Coronado PST.

First of all thanks to Steve at First Light Optics for managing to get hold of one of these for me to try out. Much appreciated.

What Coronado say..

"PST-Cak Product Description

Coronado P.S.T. CaK is a truly remarkable telescope linking two of our most recent technological breakthroughs. By combining the optical design of the price friendly P.S.T. with the Calcium K line filters of our CaK 70 telescope we are again making solar discovery a real and attainable aspect of Astronomy.

The unique CaK filter isolates a layer of the Sun that is below and slightly cooler than the layer viewed with a Coronado Hydrogen Alpha filter. The transmission line is centered at 393.4 nanometers and is isolated using thermally stable interference filters. Given that this telescope has a much smaller aperture than its bigger brother, the CaK 70 telescope, you can anticipate a drop in resolution but not in contrast, safety, or quality. The magnificent super granulation cells that gather and strengthen in this layer of the Chromosphere may not be visible to all, as most humans eyes through the process of aging are not particularly sensitive to this wavelength. The primary purpose of any CaK instrument is for imaging."

"Due to the short wavelength of the CaK line some people may have difficulty seeing every detail. However, imaging at this wavelength using standard cameras and webcams is relatively easy and produces images that are readily viewable."

• Aperture: 40mm

• Focal Length: 400mm

• F/Ratio: F/10

• Bandwidth: <2.2Å

• Thermal Stability: 0.005 Å/°C

• Safety Blocking: >10-5 from EUV/IR

What I say..

The CaK PST has the same aperture as its brother the Ha of 40mm f10. To use it is very simple. I originally mounted the scope on a photographic tripod, but the last few times I have mounted it on the HEQ5 Pro piggy backed on the ED80 with the Baader solar filter to give CaK and white light viewing. There is a small "Window" on the top of the scope for aligning the solar disk and the small focus knob is under the scope. What it doesn't have is the "Tuning ring" Found on the Ha version.

I find the mounting it on the HEQ5 a much better option for the CaK PST. (Reason to follow..Be patient!!)

The CaK PST views ionised calcium at 393nm in extreme violet range of the visual spectrum to reveal the sun’s lower chromosphere to let you see events before they are visible in Ha.

Whereby the Ha PST uses a aetalon filter to isolate a waveband of less than 1A (0.1nm) To view the upper chromosphere, the CaK PST uses a glass multicoated interference filter with a waveband of 20A(2.0nm). This filter reveals bright areas on the disk around sunspots sometimes before they are visible in Ha.

The two drawbacks of this for visual work are that the human eye is not particularly sensitive to this part of the visual spectrum and the Cak PST produces a very dark image. You need to be dark eye adapted to make any real observations at this wavelength. I used a dark sheet over my head and gave my eye time to "Dark adapt".. This was where a driven and aligned mount came into it’s own as I didn’t have to concentrate on moving the mount I could concentrate on the dark image in the eyepiece.

The CaK PST comes with a 20mm eyepiece as standard increasing the magnification gave no real benefit to visual observing as the image became darker and more difficult to focus.

Another think to consider before purchasing this scope would be that not all people can see the CaK line; this is due to age, eye condition etc.

Where this scope comes into its own is in the solar imaging department, an area which Coronado emphasizes.

“Due to the short wavelength of the CaK line some people may have difficulty seeing every detail. However, imaging at this wavelength using standard cameras and webcams is relatively easy and produces images that are readily viewable.”

If I get chance and a good clear day then i'll get the Toucam on it and do some imaging.

Would I purchase the scope……Most definitely, although after I have purchased the Ha one first!

Greg

[dazza1639]

I'll look forward to seeing some images perhaps some comparisons of white light, Ha & Cak taken at the same time to show what each reveals. When I looked at the sum yesterday with a baader solar film cap the sun was featurless. I would have expected a little more activity now that we're comming out of solar minimum.

[Kai]

Good report Greg.

Hope you are planning on bringing it to the Star Party.

I have looked through the HA version and a chance to look through the CAK version would be nice.

I also agree with your comments on which one you would buy first, i think i would go for the HA one myself

[Jaffa007]

Nice report...... thanks for the explanations after the tech bits, much appreciated 8)

Also looking forward to seeing images. :thumbleft:

[Albireo380]

Thanks Greg, I have been thinking about either the Ha or CaK for my local Astro Soc - (I am getting to spend some of their cash - So watch out Steve, FLO will get a call this Spring). Your report has confirmed me in my thought that the Ha is the one to go for first.

Tom

[Jamie]

Great first light report mate.

Sweet set up you have there too.

Now show us some images.......please..

[The Warthog]

Excellent report! I picked right up on "The magnificent super granulation cells that gather and strengthen in this layer of the Chromosphere may not be visible to all, as most humans eyes through the process of aging are not particularly sensitive to this wavelength." Hmmmph! Grumble. Youth is wasted on the young!

[Albireo380]

Hmmmph! Grumble. "Youth is wasted on the young!"

Oscar Wilde, if I am not mistaken, WH.

[lunator]

greg

Nice report,

It must have been fun getting dark adapted in daylight.

You say you would get the Ha 1st, is that due to being able to view more easily?

Cheers

ian

[Greg]

You say you would get the Ha 1st, is that due to being able to view more easily?

Yes Ian,

The CaK PST is primarily for imaging the CaK line, however the disk is visible in the eyepiece, although there were no sunspot activity when I was viewing. People with good eyesight can use them visually.

I wanted to get the Canon on PST and put the feed through the lappy to see if there was a good image for visual but the cloud rolled in.

As for the dark eye adapted bit, I put my sunglasses on for ten mins and then put a dark blanket over my head whilst observing. That seemed to do the trick.

[TheBFG]

Many thanks for that i have been looking at purchasing a solar scope but still am not sure which. Thats one down at least, with me being blind as a bat

[Merlin66]

The other issue for imaging is that not all cameras are responsive that far down in the UV.

The baader UV-IR filter fitted to some DSLR's etc cuts off at 400- 390nm so is marginal on the H-K lines

[JAO]

Great first light review. Look forward to further updates on how thi unit performs

Adrian

[LMC]

Great review. A friend of mine has a CaK PST mounted on an EQ5 afixed to his roof.

It's linked to his telly and his PC monitor. Makes a great conversation starter!

More "going on" in the CaK line than Ha, but its very difficult, (and impossible for me) to get an image thru' the eyepiece.

[Gazabone]

Out of curiosity, I think I read somewhere that CaK was best left to imaging as there are high levels of UV and may lead to cataracts. Has anyone else come across this being said? In the meantime, I'm very happy with my Ha PST, great little scope.

[Merlin66]

The "normal exposures" using a CaK filter (which significantly reduces the amount of UV getting through) for visual observing is absolutely safe.

The more realistic problem is the loss of UV sensitivity in older eyes.... not many mature amateurs can see the Ca bands.

The best (and only solution) is to image in CaK with a reasonably sensitive fast frame camera - DMK series for instance.

The latest digital spectroheliographs being used by amateurs are recording detail almost as good as the very expensive commercial filters.