Using recently acquired skywatcher ST102 refractor, see above with collapsible dark box and shroud. Along with a Baader CaK double stacked filter 390 – 398 nm covering both CaK 393.7 nm and CaH 396.85 nm I managed to image the sun in Ca k.
The filter was attached to a DMK41 mono CCD camera with a x0.5 focal reducer to enable whole disc imaging.
The CaK filter needs an energy rejection system to be used on scope, it comes packaged with 3.8 OD Baader film, but a Herschel wedge can also be used.
Other CaK systems like those available from Lunt contain both Cak filter and energy rejection system, hence the cost.
I missed the early morning activity recorded by Nick and Roger and by this afternoon there was little prominence activity according to Gong, so I just concentrated on Sunspot AR2670, imaging using CaK filter and the Baader 590nm Contiuum filter.
Whole disk in CaK, showing Plages
Colourised CaK whole disk.
Left white light image without x0.5 focal reducer.
Centre CaK without focal reducer.
Below colorised Cak
With x2 Barlow (below), smaller image white light. Trying to dodge between clouds meant that the sun was getting lower during the session and subsequently I was imaging over my neighbours roof and the garage roof, started to get lots of atmospheric wobble. However I was reasonably pleased that different detail could be imaged with the CaK filter, couldn’t take H alpha (656.78nm) at same time as I’d used the vixen rail I normally attach it to, to mount the ST102 on the HEQ5. Compare the rese CaK images with Rogers H alpha.
The white light image shows what is happening on surface of suns photosphere, the observeable surface at 5500k, H alpha shows what is happening in the chromosphere, the layer above the photosphere where the temperature rises to 50000K at its upper level. CaK images show what is occurring between the upper photosphere and lower chromosphere.
At 393.37 nm CaK is not visible to eye , in fact there is a lot of UV being passed, not good for the eyes, so this filter is for imaging purposes only.
Future activity will compare Herschel wedge / Baader film combinations with CaK filter and comparison with H alpha images from Coronado PST.