Solar Images in H alpha, Calcium K and Visible

Most of my solar images have been taken in visible or H alpha , the Baader CaK filter in conjunction with a Herschel wedge provides a relatively “cheap” way of imaging in CaK.

Images in Visible light give detail of the photosphere , which we can consider as the Suns “surface”, above this is the chromosphere, the upper part of which is viewed in H alpha and mid section can be viewed in Ca K wavelengths. (Not quite this simple as there is some overlap, but broadly works this way) The Cak is sensitive to magnetic fields and the stronger the magnetic filed the brighter the image, this gives more detail of the plages around sunspots and more detail of how magnetic field varies in these areas.

After some time setting up a system to image in all 3 wavelengths a fine clear day arrived on Friday 22nd June and I imaged the sunspots and prominences , then went away, which is why I’ve only just finished processing images.

All images were taken using a mono CCD camera : Imaging Source DMK41, the H alpha images were taken using a Coronado PST, the Visual White light images with a Herschel wedge with a ND.3 filter and Baader continuum filter on the camera, using a Skywatcher Evostar 120 refractor. The Cak images were taken with a Baader Cak filter attached to DMK41 and using a Herschel wedge with either a ND.3 or ND 0.6 filter on Skywatcher  ST102 ( for full disc) and / or Skywatcher Evostar 120. All Images were 600 frame avi’s stacked in AutoStakkert, wavelets tweaked in Registax 6 and final processing in Photoshop CS6. Not having imaged for a while I soon realised that I needed to do some cleaning before the next session as the “dust bunnies”  were more numerous than usual, luckily I was either able to manipulate image to avoid most of them or eliminate them in processing.

I have left the images as mono as features show up better for comparison rather than processing in false colour.

Whole disc in CaK and H alpha, no prominences visible in CaK.














Main surface features in Cak in Evostar 120, left to right : faculae, AR2715, AR2713


















Faculae in Halpha x2 barlow



AR2715 In Cak, Vis,  H alpha (x2 Barlow)









AR2713 in Cak, Vis , H alpha (x2 Barlow)









Prominences x2 Barlow






Images from Observing Session on 29 June 2018

Hello Folks,

This is my first blog post so apologies if I break any rules!

Several folks made kind comments about my imaging setup at last Friday’s meeting; It’s a Skywatcher 150PL on a HEQ5, I was using a ZWO ASI120MC camera (colour) with an x3 barlow and an atmospheric dispersion corrector (ADC). The filter wheel was just set for a an IR cut filter. The ADC has a pair of prisms and is used to correct the ‘blurring’ caused by the low angle of the planets at the moment – I’m still getting the hang of it.

Seeing and transparency for Jupiter was very good, but Saturn was less good and I only got one decent run before it hid behind a tree…

Mars came up and I spent about an hour on it, my first try of the year. Unfortunately my EQdir lead blew up (literally!) and although the mount was tracking it was drifting a bit and I  had to target manually which was ‘challenging’. The imaging runs when it was low down were awful, especially as it took a while to get the ADC dialled in with my attention more on keeping the red blur on screen! The final image shows next to no detail, but all other images form that evening are pretty low on detail 9although some are a bit better than mine). This is because of a planet-wide dust storm on Mars, hopefully it will die down before opposition in about a month.

The good news is that mount and computer survived the exploding dongle and an off the shelf USB-serial dongle was easy to wire up as a replacement.

Thanks to all RAG members for making me feel welcome, and giving me some really helpful advice and assistance.

<edit, the previews should now link to the full size images – I hope!>


Jupiter and Europa
Jupiter and three moons

Sun in a new Light – Cak

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 White light, continuum 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.

Pete H

Venus and Mars (there’s a song about that)

Venus is shining strongly in the evening sky, even brighter than Jupiter in the morning sky, finally cleared the roofs opposite so had a go at imaging it, tried a different approach this time, have previously attached the DSLR to eyepiece using T ring and adapter, this time tried it with the DMK42 mono CCD camera with a red filter, to remove any chromatic aberration. Used 120mm Evostar  refractor on HEQ5pro, sidereal tracking mode, max frame of 15fps with DMK41 , #23A filter attached, 600 frame .avi files recorded with, no magnification, x2 Barlow and x5Barlow, also imaged Mars to left and above Venus with no magnification.

All images produced from stacking .avi in Autostakkert, wavelets in Registax6 and final processing/sizing in Photoshop.6



Venus with no magnification, slightly gibbous (about 60%),will become larger and more of a crescent as it moves to Greatest Elongation in January.





venus3psx2b with x2 barlow







venus0005psx5bwith  x 5 Barlow







venusandmarsMars and Venus with no magnification, taken under same conditions.

Mars is so far away now, even high magnification only shows a red disc, with no features, a UV filter would be needed to draw out any features in the atmosphere of Venus. (Did you hear that Santa?)





Have a Good Christmas and New Year!

Pete Hill