Calcium Full Disk 25th August

It seems to have been a while since I imaged in calcium wavelengths, so on Sunday afternoon I decided to go for a full disk with the skywatcher ED80 stopped down to 60mm, coronado 2x cemax barlow and the Grasshopper camera with the homebrew calcium filter.  It was interesting to see the polar faculae are noticeably larger in size than plage bright points mid disk.  The polar faculae in calcium match up very well position wise with these features in the 2 disks prior to this post.

Sodium Full Disk 25th August

I was going for the trio of full disks on Sunday so had to shoot a sodium disk with the Daystar Quark.  There is little to see but around the poles the polar faculae synonymous with solar minimum conditions were visible.  Taken with the Tecnosky 60mm f6 scope.

Ha Full Disk - 25th August

The sun at first sight appears blank again, however a number of small filaments can be seen on the disk; at the south pole the diffuse filaments represent the proms in the previous 2 posts that I did an animation of.  Mid disk a filament and brighter plage are the remnants of the active region that first appeared at Easter time, now with a coronal hole also associated this region is now on it's 4th rotation of our star.  In the northern hemisphere the filaments are associated with the magnetic fields due to sub surface cycle 25 jet stream activity, with a small emphemeral region at the 2 o'clock position being cycle 25.  At the north pole polar faculae can be seen shining through the chromosphere as bright points.  Throw in a few proms too and there is more than meets the eye.  Taken with a Lunt 50C etalon double stacked with a Daystar Quark, Baader solar telecompressor and a FLIR Grasshopper 3 camera.

Still Raining on the Sun - 24th August

Saturday gave me some free time and with blue skies I decided to try another animation of the active prom region that has been rounding the limb.  I got 140 frames covering 45 minutes real time to produce this animation.  I included an Earth scale just so you can see how small we are in the bigger picture of things that happen on our star.  Taken with the Coronado SM90, 1.6x barlow and Grasshopper IMX174 camera.

Descending Prominence Knots and Coronal Rain - 23rd August

Friday started grey and misty for me which was frustrating given the forecast was for blue skies, however by early afternoon all the low cloud burnt off to reveal really quite blue skies without the usual haze. I went out and set up and also pleasantly surprised the SSM was coming in with seeing values in the region of 2-3 arc seconds:

I knew this was too much to bother with the HaT so got the SM90ii out. With nothing of note on the disk worth pursuing, I went hunting for the big prom that was visible; Starting off with a 3x barlow it quickly became clear that this scale was going to be too much, so dropped down to the 2x, again too much (I was running files through AS3 on the fly), however dropping down to a magnimax barlow nosepiece giving me a image scale of ~1.6x straight away it was obvious on firecapture this scale to image at was working with the seeing. I decided to opt with the smaller image scale knowing I would get something I could work with rather than waste time (and hard drive space) chasing an elusive super close up that might or might not work out.

Using the Grasshopper with the IMX174 chip I went in automated mode, using the Hinode solar guider to keep the scope squarely on the prom and the SSM and plugin in FC to set a threshold so I was only recording the sharpest of frames. Despite the prom looking pretty quiescent on GONG I could tell from looking visually through the SM90 there was quite a bit of subtle activity with it so decided just to blitz it, and get as much data as my diminutive hard disk would allow. A few passing fluffy clouds interrupted what would have been a perfect run but these have little effect on the result. I managed just shy of 40 minutes of observation from 14.57 to 15.36. I decided to leave the less sharp images in the sequence as they keep the continuity of the movement that was visible, only deleting the cloud sections. I ended up with an animation of 120 frames spanning nearly 40 minutes, so a cadence of about 3 frames a minute.

The result pleasantly surprised me. I aligned in ImPPG with several alignment iterations as Photoshop just locked up every time. I know the image is inverted to the norm, but is looks strange raining the wrong way. It then got me looking around as to whether coronal rain is the right terminology for it, as, traditionally coronal rain is associated with post flare loops, and there was definitely no flaring with this! Turns out there are different categories of coronal rain with the rain in this type being called 'descending prominence knots'. The rain part refers to the condensation of cooler material - plasma on the sun as opposed to water on Earth, however in post flare loops the rain is guided and forms along the magnetic field lines, whereas in this situation the field lines in a prominence are flat (compared to looped) so the rain forms due to temperature differences (instability) in the corona. As the environment is 'viscous' they fall back towards the sun at less than terminal velocity. Given all frames are timestamped and we know image scale it would be quite possible to work out a velocity for these 'descending prominence knots' (or raindrops), i've not done this but theory suggests a few tens of kilometres a second. The science in all this is really very new, this paper https://iopscience.iop.org/article/10.1 ... /1/21/meta from 2014 is perhaps the most comprehensive I found, and heavy going in parts still gives useful information.

The STEREO image suggests a couple of brighter points about to round the limb at these low southern latitudes (remember my ani is vertically inverted), given there latitude this means they are cycle 25, and this is also contemporaneous with the latitude of the prom, so, definitely the area to keep an eye on this weekend.

Hope you like my cinema, just about to head out and see what I can get this morning.

Polar Faculae & Cycle 25 Jet Streams - 17th August

The sun may on the face of it be blank at the moment, but there are plenty of subtle signs visible of where we are in relation to solar cycles.  The image above in the top half of the image shows bright polar faculae,  these are magnetic areas on the sun, not strong enough to form sunspots or pores, but strong enough to be visible in a variety of wavelengths; in white light they are visible as white spots on the photosphere, but, higher up in the chromosphere in Ha wavelengths they appear as small bright jet like features shooting upwards.  They only form in the polar regions at solar minimum as the magnetic fields are stable at this time, during solar maximum the poles are under going a magnetic field reversal and so polar faculae are unable to form.

In the bottom half of the image we can see small, dark filaments; regions of plasma held aloft by magnetic fields, however these magnetic fields are in the jet stream regions where we expect to see the tell tale signs of cycle 25.  While these magnetic fields are still quite weak, only able to support filaments, over time their field strength in gauss will increase enough for them to start developing first of all pores and then sunspots, with developed umbra and penumbra.

Taken with the 90mm Coronado SolarmaxII telescope double stacked with a Daystar Quark to increase image contrast by reducing continuum leakage into the image.

Cycle 24 Equatorial Plage - 17th August

These small bright points are plage, the residual magnetism of cycle 24 on the suns equator.  These will slowly but surely become absent as cycle 24 magnetism is cancelled out and cycle 25 starts to become more prevalent at higher latitudes.  Taken with the 90mm Coronado SolarmaxII telescope double stacked with a Daystar Quark to increase contrast  by reducing continuum leakage.

Ha Full Disk 17th August

Been a while since i've had the time to observe what with one thing and another.  A quick peek at the sun as a whole shows we are still in the depths of solar minimum, one small prom and a few small filaments are about it.  However polar faculae are visible in both hemispheres.  Taken with a Lunt 50 etalon double stacked with a Daystar Quark.

Ha Full Disk - 7th August

The sun really is quiet - there's no prominences, no filaments, just a small flux region and a couple of brighter points of plasma around the solar equator, apart from that it's pretty representative of solar minimum conditions.  Taken with the Lunt 50 etalon, Tecnosky 60mm f6 scope, Daystar Quark, 0.7x solar telecompressor and the FLIR GH3 ICX814M camera.

Sodium Full Disk 6th August

I remembered yesterday evening I can use the Na Quark for full disks, and ever the optimist and despite looking on the AIA1700 image first thing and seeing yesterdays pores had gone, I still had a go at a full disk, and you know what - the solar dynamics observatory was right, there were no pores or spots remaining. A blank sodium disk then - one day some spots I promise!

Ha Full Disk - 6th August

Up early as usual, we're in unsettled air with jet stream Atlantic weather blowing in, and experience suggests there's normally a brief window of clear skies just after dawn and just before the heat of the sun gets convection going and clouds bubbling up. This was indeed the case and only had enough time for a couple of full disks, first off things in Ha with my preferred setup of Lunt50 etalon, 60mm f6 scope, Daystar Quark, 0.7x solar telecompressor and FLIR GH3 ICX916M camera. Where we had the emerging flux region yesterday seems to have quietened right back down now, but is still quite bright compared to the background disk. A few brighter points in lower southern latitudes mark the tell tale sign of the cycle 25 jet stream, and a few very small proms and filaments are about it for today.

Emerging Flux Regions - 5th August

There were 2 small emerging flux regions visible today on out star.  At its height the EFR on the right also sported small pores where the flux tubes broke through the photosphere, in Ha and higher up in the chromosphere they manifest as darker and cooler regions of plasma that arc and follow the magnetic field lines.  Taken with the Coronado SM90ii double stacked with the Daystar Quark and the FLIR GH3 ICX916M camera.

Old Active Region Remnants - 5th August

If you look back on this website in the archives to April this year you will see we had some quite large active regions gracing the solar equator.  Now, several rotations later this region of turbulent plage is all that remains.  Will it be visible in 2 weeks time when the area rounds the limb again?  Who knows?  Taken with the Coronado SM90 double stacked with the Daystar Quark.

Northern Polar Regions 5th August

While there may appear at first glance that not much is going on in this image, the bright patches of polar faculae, normally associated as white light features of the photosphere, here they also shine through the chromosphere as bright points.  Polar faculae are more prominent during solar minimum.  Taken with the Coronado SM90 double stacked with the Daystar Quark.

Ha Full Disk - 5th August

Another one of those days when Spaceweather says the sun is blank; but it isn't.  Two emerging flux regions can be seen in equatorial regions not long after coming over the limb, also on the opposite limb the region of turbulent plage that marks where active regions were visible back much earlier in spring.  Taken with a Lunt 50 etalon double stacked with the Daystar Quark.

Sale of Solar Items!

Having a good clear out of some solar stuff i've not used for a while, so it's the solar summer sale.  Check out my listings on SolarChat 

https://solarchatforum.com/viewforum.php?f=11