Double Stacked CaK Disk - 29th September

My newly constructed double stacked CaK filter is showing itself as a keeper.  Compared to a single stack CaK unit the plage is much brighter compared to the background disk and super granulation is much more evident and apparent over the entire disk.  More interestingly is that proms are much more apparent than in the single stack filter.  Today a surge prom in the 2 o'clock position was easily see, even in this image taken with the 40mm at f20.  There are tantalising hints of the spicule layer also being visible.  Given that this shot  was taken in poor seeing conditions with a low altitude sun, it does bode for even better results when conditions are ideal.  There is still work to do; a 'ghost' is visible superimposed on the right hand side of the disk, but this should be relatively easy to either remove or throw out of the field of view.  In short, i'm really pleased with this filter, I just wish I had got it 6 months earlier this year!

ar11850 & Surge Prom - DS CaK 29th September

ar11850 CaK, a photo by Mark Townley on Flickr.

There was a lovely surge prom visible today using the double stacked CaK filter. The faint CaK spicule line can also just about be seen on the limb. It seems that double stacking in CaK makes the prominences much easier to see compared to the single stack images. I was pushing things today with the low altitude sun, with this shot being taken with the 100mm at 2000mm focal length with the DMK31 camera, but this image is just about usable... It definitely has much promise for when the sun is higher in the sky.

ar11850 & ar11846 DS CaK 29th september

ar11850 ar11846 caK, a photo by Mark Townley on Flickr.

A medium scale shot of the departing active regions visible on the suns disk today taken with the 100mm at 1000mm focal length with the DMk31 camera.

Ha Full Disk - 29th September

The sun may not have many large active regions at the moment, but the disk is far from being bland.  Lots of filaments are visible in this image taken with the Coronado DS40 at f20 with the DMK31 camera.

CaK Full Disk 22nd September

ds cak full disk colour, a photo by Mark Townley on Flickr.

Even on a relatively quiet day on the Sun as it was as we passed into autumn there is still plenty to see in CaK wavelengths. This was another outing for the double stack CaK filter, which had been redesigned in its configuration to remove the reflections and ghost images that were present when i first set it up. It is performing very well now with only minimal ghosting at the bottom of the disk which should be fairly easy to remove with a bit of tilting. This was taken with the 40mm @ f20 with the DMK31 camera.

Ha Full Disk - 22nd September

DS Ha full disk bw, a photo by Mark Townley on Flickr.

Some intermittent september sunshine allowed me to shoot this full disk using the DS40 at f20 with the DMK31 camera.

DS CaK Full Disk 'vs' Solar Dynamics Observatory AIA1700 - 21st September

The above shot was taken with my very recently constructed 'double stacked' filter; this is a concept i've been wanting to realise for sometime now.  Commercial CaK filters have a bandpass of >2.2a, however by stacking 2 of these together in series it should be possible to reduce the bandpass down to 1.5a.  This is well within the performance of many professional observatories world wide and with it should bring advantages over the commercial units.  Yes, there will be a reduction in the through pass of light but this is easy to address with an alternative choice of ERF, however the pluses out weigh this; reduced bandpass means an improved signal to noise ratio for the image, and with it super granulation cells are much easier to see, while still faint prominences and filaments are also easier to see than in commercial form.  Plage areas appear much brighter than usual, and the non active disk is much darker.  

When I looked at the monochrome version of this image I was struck at how much it resembled the images the Solar Dynamics Observatory Atmospheric Imaging Assembly (AIA)1700 camera.  So much so I decided to colour the above image with their palate and do a direct comparison; the image below was taken by the SDO at the same time I took the image above.

Comparing the 2 images directly I don't think the double stack CaK filter is performing too bad, especially when you compare the 2 imaging systems:

The Solar Dynamics Observatory is a NASA mission that was developed by the Goddard Space Flight Institute that sits in orbit above Earth taking photographs of our star at an estimated cost of 817 million USD. 

The double stacked CaK system was developed by me and sits on Earth looking through 300 miles of atmosphere and the optical system for this cost less than 1000 GBP.

When taken in comparison like this, I think the double stack CaK system has a lot to offer and will offer great images for a lot longer than the estimated 5 year life time of the Solar Dynamics Observatory.

Below is my monochrome version of the image which is also very comparable in detail to that of the Paris Meudon Observatory seen below it.

DS Cak Full Disk

DS Cak 40mm f20 colour, a photo by Mark Townley on Flickr.

Taken with the tiny 40mm f10 OTA that makes up the SM40 scope this image shot at f20 shows a surprising amount of detail, recorded using the DMK31 camera.

ar11843 & ar11841 DS CaK 21st September

ar11843 ar11841 DS CaK 100mm f20, a photo by Mark Townley on Flickr.

The sun starts to take on an almost 3 dimensional textured look to it's surface around the limb with the double stacked CaK filter when used with the 100mm at 2000mm focal length. Taken with the DMK31 camera.

ar11850 DS CaK 21st September

ar11850 DS CaK 100mm f20, a photo by Mark Townley on Flickr.

Taken with the 100mm @ 2000mm fl with the DS CaK filter and the DMK31 camera.

ar11846 DS CaK 21st September

ar11846 DS CaK 100mm f20, a photo by Mark Townley on Flickr.

Taken with the 100mm @ 2000mm fl with the DS CaK filter and DMK31 camera.

ar11849 DS CaK 21st September

ar11849 DS CaK 100mm f20, a photo by Mark Townley on Flickr.

Taken with the 100mm @ 2000mm fl, DS CaK filter with the DMK31 camera.

Double Stacked Full Disk - 21st September

DS Ha Full Disk colour, a photo by Mark Townley on Flickr.

The first day of astronomical autumn brought clear(ish) skies on saturday. The sun is quiet at the moment but far from inactive, with smallish active regions, filaments and prominences putting on a show for us.

Double Stacked CaK Full Disk 16th September

DS CAK full disk bw, a photo by Mark Townley on Flickr.

After some considerable time searching I finally have bought another second hand CaK PST. The method behind this was simple; to double stack a CaK filter. The CaK PST filter in it's native form has an advertised bandpass of <2.2a, compared to the 2.4a of the Lunt unit. By putting two CaK PST filters in series the bandpass will tighten to an estimated <1.5a. Well what is to be gained from this exercise? Double stacking in Hydrogen alpha wavelengths has the effect of improving the signal to noise ratio by reducing continuum light leakage into the image - in simple terms the contrast should be better. Images of the CaK sun taken with instruments with a tight bandpass, eg spectroscopes or BASS2000 show the disk itself to be much darker, with plage relatively much brighter, but also with tentative hints of prominences and filaments, something I have observed before in single stack CaK on certain occasions. Well when the image above was taken conditions could not have really been any worse; the sun was at <10 degrees altitude in the sky and was imaged through the haze of high cloud. In addition our star was pretty devoid of activity, there was only one or two very small spots, no proms and the filaments that were there were only very small and hairline - not untypical of our star at solar minimum! However, given the cumulative effect of all these factors I am very pleased with the outcome, the image definitely shows more contrast to what I am used to, and the most apparent thing is that the supergranulation cells are easily visible across the whole disk. If I really stretch the original TIFF file I can start to see the filaments that were visible. Typically since getting this setup the weather has been what can only be described as typically autumunal and have not been able to explore with it as much as would hope. Still, as I write this there is high pressure upon us (and cloud!) but there are breaks forecast, add to that the sun has increased in activity and if the clouds do clear then hopefully should have some good results to share!

Double Stacked Disk - Sunday 8th September

Ha full disk BW, a photo by Mark Townley on Flickr.

Taken with the Coronado DS40 at f20 with the DMK31, there wasn't a lot happening on our star this weekend, with only a few small spots visible. Despite the blue skies first thing in the morning it wasn't very long before the clouds and heavy showers took over and solar observing was over for another day.

ha Full Disk 7th September

ha full disk colour, a photo by Mark Townley on Flickr.

Things are VERY quiet on the sun at the moment with very little on the nearside, even this view taken with the DS40 shows sparse detail. Hopefully things will pick up and this isn't a sign of a things to come!

Big Prominence - 7th September

big prom ds100 bw, a photo by Mark Townley on Flickr.

Taken with the double stack PST mod at 2000mm fl with the DMK31, this picture shows double stacking does show some promise, however these images from saturday are all slightly in the wings of the Ha line. The DS PST mod is complicated to setup, and at the moment i'm still working out all the many variables and their innumerable combinations. The problem I do have is a spell of consistent and continuous sunshine to test out properly. Still, with each outing i'm getting a better understanding of how it works and the optimum way to set this combination up.

Floating Prom 7th september

floating prom ds100, a photo by Mark Townley on Flickr.

A prom floats above the surface in this DS shot.

Proms With The DS PST Mod - 7th September

prom ds100 bw, a photo by Mark Townley on Flickr.

Taken at 2000mm fl with the DMK31.