Is a CAK scope worth getting?

[Astroblagger]

Hello was just wandering what people though about Cak scopes? how do they compare using visually with the H Alpha scope? Or are they more suited for imaging, iv got a H Alpha scope and am blown away by the view down the eye piece, but wandered if the Cak one is worth the money?

[Merlin66]

Unless you have the eyesight of a 16 yo, visual observations in CaK will be extremely difficult. Are we age we loose the sensitivity down in the violet UV.

The Cak is used primarily for imaging. You need a suitable CCD camera. The DSLR has a UV cut-off above the Cak so doesn't record it....

Cak modules are becoming difficult to find. The Coronado CaK scope is no longer produced. Lunt have a CaK filter module but some users have experienced fitment problems due to the overall length.

HTH

[hunterknox]

Seconded. Pretty much useless visually but great for imaging.

[GlassWalker]

Baader do a CaK filter in 1.25" size which you can use with any ordinary telescope. Comes with safety film which is also a must.

As always the weather hasn't cooperated so I've only had one chance to use it so far. Here is a imaging comparison with e PST:

Left: H-alpha on PST just as cloud was coming over. Right: Baader CaK on Nexstar 4SE. Both with a modified Canon 450D, so I wouldn't rate a CCD as a necessity although it will probably help a bit.

CaK does look different from H-alpha. I haven't tried visual with it at all as I suspect I'm past the best age group for that.

[Merlin66]

The broadband Baader CaK filter gives an "overview" of the sun's features in and around the CaK/ H wavelengths.

The much narrower band width of the Coronado or Lunt (2.2A/ 2.4A v's 80A for the Baader) really bring the CaK detail to life!

(GlassWalker - was your 450D given the FULL full spectrum Mod? ie the front anti-alias filter removed as well as the Colour balance filter?

The AA filter also acts as a UV-IR cut which significantly reduces the response in the UV....)

[GlassWalker]

My 450D has all filters in front of the sensor removed. If I could, I'd remove the colour array too which doesn't help for narrowband imaging... but that's where the DMK41 comes in.

While the Baader CaK isn't a very narrow narrowband filter, like everything else, if you want much more, you pay much more!

[Merlin66]

Sounds like you've got a good FULL spectrum camera mod.

Yes, getting that narrowband filter without the widepocket price is like looking for the Holy Grail!

(Omega had some 25mm diameter 40A bandwidth filters centered on the CaK wavelength for around $25.......http://www.omegafilters.com/store/Products)

[GlassWalker]

I originally had a clear glass mod on it as I wanted to retain AF for other uses, but trapped dust annoyed me too much so I removed that and it is now as unfiltered as it gets.

The Baader is 8nm, so halving that could be interesting. Can't see a cheap one on there at the moment.

Wonder why they don't make the PST CaK version any more?

[Merlin66]

I think they were just not selling enough of them....really only suited to a "specialised" imaging market......

[Astroblagger]

where would i be able to pick up the baader 1.25" cak filter and saftey film from then?

[Merlin66]

TS sell them....

http://www.teleskop-express.de/shop/product_info.php/info/p3415_Baader-stacked-1-25--K-line-filter-for-Solar-photography.html