Wednesday, 27 February 2013
Tuesday, 26 February 2013
Sunday, 24 February 2013
My recent visit to Switzerland as seen in previous blog posts involved me visiting my good friend Swisswalter, where among other things affordable CaK solar was a hot topic.
Walter has tried various combinations of filters in the past to get a CaK result and so we had alot to discuss. Whilst looking through his collection I spotted a filter labelled 393nm SP (short pass) 10a. Visually this looked pretty much identical to the front filter from the CaK PST that I use with the Baader K-Line to get results indiscernible from the native CaK PST and the Lunt CaK filter and so had some optimism with this. We decided to disassemble the Lunt CaK filter to see what it contained; interestingly the filter at the eyepeice end of the unit was also a yellow filter, that looks also identical to the one from the PST and the 393SP. The rest of the unit contains 2 identical filters that when look through visually has the deep purple hue of the Baader K-line.
The weather was not clear enough to test the combinations on the day, but Walter kindly did this a few days later. There were surprises in the outcome: First off the reference image, the Lunt B1200
Then the Baader K-line and the 393SP; rather lacking in constrast in comparison to the Lunt image, but, for the homebrew filter combinations, possibly one of the best yet...
The 393SP/K-line image quite clearly lacks the contrast of the Lunt, but there is some detail being pulled out compared to what we would expect in a normal CaK image. I suspect the outcome is due to a broader bandpass compared to the Lunt letting in more of the continuum light and hence the poorer constrast. However, Walter tried the the 393SP/K-Line in conjunction with the Lunt B1200 and there was a suprising improvement in results, with more contrast visible.
So, an outcome, if not the outcome that was intended! I'm hoping Walter may be able to test the yellow filter from the Lunt B1200 with the Baader K-Line, this may also give us a result?
In the mean time, when I got back to the UK my GG400 long pass filter had arrived and so was time to try this out. I figured the falling transmission at wavelengths shorter than 400nm may have the effect of tightening the bandpass of the K-Line/CaK PST combination I was using, well, we had about half and hour of clearish skies and so decided to try it out. With the GG400 in this stack the image curiouslly reverted back to essentially a whitelight image lacking in any CaK features. Hmmmm, not what I wanted or was hoping for, but, we have to take from this what we can, and while a negative result is annoying atleast it shows us that something doesn't work.
Since then I made an interesting find; Andy Dodson in New Zealand has been modding his CaK PST in much the same way as I have http://www.pbase.com/andy_dodson/evoloution_of_my_ca_k_filter&page=2 We had both wanted to replace the bf5 in the CaK PST with a larger option, we have both tried the Omega options off EBay and had reached the conclusion that these were lacking in the optical quality needed. Now this is where our approaches differed; I had used the Baader K-line whereas Andy had used the Baader U or 'Venus' filter. Now, when you look at Andys excellent images it's very clear this filter is also very effective when used with the 'front end' of a CaK PST.
Now, the fact we have two different filter combinations that work very effectively tells us something about the front element of the CaK PST assembly, as this is the one that is the common factor in both setups. Using a simple CD spectroscope the front element from the CaK PST shows no transmission below 450nm, now, this quite clearly isn't the case as it is very effective at 393nm. So, what I think is going on here is that the CaK PST front filter is showing the same style of transmission as the blocking filter that is used in a Ha setup. In other words a very narrow (2.2a) pass at the chosen wavelength 393.4nm, then a band of blocked transmission to ~450nm then above this a normal transmission. This is what happens with the blocking filters used in Ha setups, but at obviously a different range of wavelengths.
So, where does this leave us in the search for a suitable 'commercially available' filter to use in conjunction with either the Baader K-line or U filter. Well i've been looking for sometime now and are not aware of any off the shelf blocking type filters centred on 393.4nm - they may well be a bespoke filter, which could start to make things expensive.
However there is one more alternative I would like to explore with the Baader K-Line, and that is a 387/11nm bandpass filter, this has really steep sloping sides and cuts off just above 393nm. Certainly in the UK they are available here http://www.laser2000.co.uk/semrock_filter.php?code=CFW-Ex01-Clin-21.8-D but at £199 are in the same league price wise as the K-Line. Could be expensive if it doesn't work, fortunately the company offers a 30 day no questions money back guarantee if the filter doesn't do the job you expect it to. What makes me more confident with this setup than others i've looked at? Well consider the transmission curves below.
You can see the transmission of the 387/11nm in blue with the K-line in red, and then the resultant curve in green. We can see if we zoom in this gives us a lovely tight bandpass centred on 393nm with a transmission of ~46%.
Now, maybe this is still too broad a bandpass to do CaK imaging effectively, but is clearly a lot tighter bandpass than the Baader K-Line on its own. Fulvio Mete's excellent website on imaging at CaK wavelengths http://www.lightfrominfinity.org/VHIRSS%20Solar%20Images/VHIRSS%20solar%20images.htm he posts this image which shows the Calcium K line is actually really quite wide (compared say to Ha).
Now it is obvious that the horizontal scale on the two plots immediately above are different, but the profile of the curves is similar, and maybe, just maybe, the 387/11 K-line combination whilst not having as tight a bandpass as the 2.2a CaK PST it might come close enough through cutting out that bit more continuum light to make CaK visible? The problem we're now getting is the cost - potentially up to £400 for 2 filters (K-line & 387/11), throw in the fact you would need an ERF - possibly another filter, or ideally a solar wedge and the price is getting pretty close to a Lunt B1200. However, if you have some of these elements already then the cost isn't too bad. Oh, and the fact this system runs at 25mm clear aperture - the Lunt B1800 & B3400 CaK modules are thousands of $$$ to buy, if it works, then despite the expense, maybe it's not that bad after all...
So, the plan now. Well, it's just total cloud cover here in the UK, but when the clouds do go for long enough then i'm going to get one of these 387/11nm filters courtesy of the 30 day money back guarantee and will test it out with the k-line. Fingers crossed it will work! Till then I have to wait till the clouds go, but can be sure I will report back on the results!
Saturday, 23 February 2013
February has been a sparse month for me in terms of solar observation with poor weather here in the UK, however in the latter half of the month when the clear skies of high pressure sat over the country I was visiting CERN in Switzerland. Whilst frustrating in the sense I was not at home over the half term break to capitalise on the clear skies, the experience at CERN is something else again.
I was privileged to enjoy conversation (and a beer!) at length with the great Klaus Batzner. Klaus is a very humble man in terms of his own achievements, but from anyone else perspective his achievements are astonishing, and previously unknown to me have solar connections. Klaus was in the class of 1947 at Gymnasium Leonhard in Basel, Switzerland before commencing his studies at the University of Bern. In the early 1960's Klaus started his work and research at CERN when the director at the time was Victor Frederick Weisskopf, 10 directors and 50 years later and Klaus is still at CERN!
Klaus is a rare breed - both scientist and and engineer; normally physicists come up with ideas and it is the job of the engineer to physically manufacture things, however Klaus could do both.
This photo taken at CERN in June 1979 shows council members visiting the technology exhibition. Klaus Batzner makes a demonstration; Gerhard Fisher and Wolfgang Paul observe on the background (centre).
Klaus initial work concentrated on particle accelerators and particle physics, and was a key member of the team who worked on the Proton Synchrotron; The Proton Synchrotron (PS) is a key component in CERN’s accelerator complex, where it accelerates protons delivered by the PS Booster or heavy ions from the Low Energy Ion Ring. Below is a montage picture I took of the LEIR on my visit.
Ions from the PS then pass onto to the Super Proton Synchrotron where Klaus worked on the team that earned Simon Van der Meer the Nobel prize for physics in 1984 for the contributions to the CERN project that led to the discovery of the W & Z particles, two of the most important contituents of matter.
Klaus can be seen on the right hand side of this image with Simon Van der Meer and Hans-Otto Wuster. The image below was taken in June 1976. After the acceleration to 80 GeV in May the 200 GeV energy was attained on June 4, followed by a successful attempt to reach 300 GeV and then 400 GeV by the Council session on June 17. Here at the desk (centre) Boris Milman and Bas de Raad, (right) Pat Mills and a machine operator. Then standing on the back Jacques Althaber, Simon Van der Meer, Hans-Peter Kindermann, Raymond Rausch, John Adams, Klaus Batzner, and still back Antonio Millich, Jim Allaby, Wim Middelkoop, Bo Angerth, Hans Horisberger.
Klaus Batzner, a great physicist and engineer! Thank you for the time you spent talking to me.
Monday, 18 February 2013
Walter lives some 700m asl in the Swiss Alps in a lovely village called Wolfhalden. Despite the morning dawning cloudy it soon became apparent there were going to be some nice breaks for solar observation.
While we waiting for the breaks to materialize Walter kindly showed me his extensive collection of telescopes - at least 14 I counted, and also his extensive collection of astro accessories. It wasn't very long before we had dismantled (and reassembled!) most of Walters scope collection to see what was inside, how they were put together and how they worked. We naturally then turned our attentions to scope modding, and Walter kindly allowed me to retro-fit his PST etalon assembly with an 'acrylic ring' to help centre the important glassware. Many drawings were produced as we discussed 'creating' several new scopes, with the traditional PST etalon and also using a Lunt 50mm etalon; collimating lenses and refocussing lenses were hot gossip!
We had some very interesting discussions on the Lunt CaK filter, and after thoroughly disassembling Walters B1200 and seeing what it was made up of and how it worked turned our attentions to Walters extensive collections of bits and bobs, all stored in a particularly elegant glass fronted cupboard seen below, discovered that he had a 393nm 10a shortpass filter. Visually this appears to be identical to the very front filter from the CaK PST that I use with my Baader K-Line to get narrow band CaK images with my home brew setup. A bit of very crude spectroscopy with a angled CD showed that the 393SP and the CaK Pst front filter are very similar if not identical things. Walter is going to test this theory the next time the sun returns properly to Appenzellerland...
Meanwhile, as we pontificated on the finer details of solar modding the clouds were getting ever thinner and the sun was starting to cast visible shadows, which for a poor weather suffering Englishman like me is cue to go out an take a look at our star!
Walter had his 100mm Lunt scope set up on the Losmandy G11 mount, and with a 16mm Televue Nagler eyepeice the views were certainly impressive. It was my first view through one of these pressure tuned Lunts and I have to say I was very impressed with the view. Bear in mind all my large aperture solar scopes are variants on the PST mod, and as such are troubled with the dreaded sweetspot, where bandwidth and centre band pass vary towards the periphery of the field of view. There were absolutely no issues of this with the Lunt 100, and compared to my PST mod the bandpass was also much tighter with the filaments being much darker and easier to see.
Given this was the first sun in Appenzellerland for over 2 weeks and we were all still merry from the night before proceedings as you can tell we were all very happy solar observers, and despite the near freezing temperatures and foot of snow in Walters garden this did nothing to dampen the mood. Despite the expense of these 'off the shelf' scopes, viewing through the Lunt 100 has certainly proved to me that if you can afford these things that they are definitely worth it - lovely even field of view from one side of the solar disk to the other! In the mean time we had donned our Charlie Bates Solar Astronomy Project solar glasses and hats in respect to the fine club that we are members!
Now as if things could not get any better, Walter decided it was time to bring out his Coronado SM90 etalon to double stack the Lunt 100 to create the infamous 'Luntanado' as originally created by Jim Lafferty. I'm used to a double stack in the form of my DS40 scope, but at over twice the aperture of mine the views that this setup afforded were phenomenal. I can only imagine that if the skies were totally free of cloud we would have delayed our departure time to head to Geneva and spent a little while longer taking in the detailed views that this scope offered. The only (very) slight downside of this setup was that the images were slightly dimmer than we might have liked due to the intermittent and variable cloud, and also the extra ERF in the chain from the SM90. The SM90 in this case is the newer Solarmax II design, with it's rich view tuning, now as you might expect myself and Walter discussed at some length the removal of the ERF from this etalon housing, however, it would appear that it is integral in the 'rich view tuning' this etalon offers. It should in theory be possible but would have to be replaced with some optical plate glass for this to work. This was also interestingly my first views of this richview tuning arrangement and it is fairly obvious how it all works: Essentially the tilt wheel on the mounting plate allows you to throw the reflection this second etalon makes in the double stack setup, but then the richview element allows you to bring the etalon very finely to the ideal position to get the etalon online and onband to extract maximum contrast and hence detail. Interestingly the richview pivots the etalon around its centre spot and then by definition halves the angle across the face of the etalon by which it is been tilted perpendicular to the optical axis. This will have the net effect of reducing any banding associated with this design of external etalon compared with tilting it at the circumference of the etalon. This is actually quite a clever yet subtle development in terms of tilting an external etalon, and is something that I will look to implement on my DS40. I'm going to look at the Richview system a bit more in a coming article on here.
Till the, I would like to thank Walter and Barbara for their hospitality and giving such an excellent time in our stay in Appenzellerland! I hope to see you both again soon!
Monday, 11 February 2013
Saturday, 2 February 2013
As new active region AR11667 rounds the limb it seems to be crackling with activity and several smaller assiociated spots. It should certainly be picturesque to view in the coming days. Taken with the SS127mm @ 1900mm fl with the DMK31.
For all of saturday a large detatched prom hovvered above the surface of the sun. It had a very low surface brightness making it difficult to photograph, but using the 127mm I got an image that was just about passable!
It is interesting to compare the disks from the single stack and double stacked scope. Despite less constrast, there is condiderably more resolution with the SS compared to the DS. The other obvious difference is image scale - the SS disks are nearly 3x the size of the those that come from the DS.
My first full disk mosaic of 2013 using the DS40 @ f16 with the DMK31. I wondered now I have the SS70 whether this scope would still be useful, but, depsite the smaller aperture of this double stack it still pulls out more features than the single stack scope. Quite low activity levels today but plenty to see with this scope!
Despite the clear blue skies the seeing conditions were terrible in the unstable northerly airflow. I didn't think this image would come out, but it has! This was taken with the 70mm @ f12 and DMK31 using my CaK stack. I used a peice of KG5 in the optical train today which seems to have cut back on some of the bloomimng in the raw frame, next time I will try an ITF to see what impact this has.
My first white light full disk of 2013 - this was taken with the 70mm @ f12 with the DMK31, I used the Lunt solar wedge and a Baader D-ERF as filter to try and tame the poor seeing back a bit. I'm not sure I like my pale yellow white lights, may have to explore a new colour for these as the year progresses...