Category: Solar log
On Monday the 24th of May I shot a few images of the Sun with my Coolpix 4500 connected to a 32mm Plossl eyepiece. The first image shows a large prominence. The image was shot through the Coronado PST. The second and third image were shot through the Herschel prism, mounted on a 4-inch refractor. The filters used are a Baader Kontinuum filter and a neutral density 3.0 filter, also from Baader.You can click on all three images to enlarge them.
The sketch was made using a low cost 15 mm Ultrawide (66 degrees) eyepiece with long eye-relief from Sky watcher. The picture was much clearer and showed more detail than my 15mm Vixen Lanthanum. The latter is absolutely darker, and much more expensive (about 5 times the price of the Skywatcher 15mm). Other eyepieces that were used during observing were the 21mm Denkemeier, 12 mm Nagler T4 and the 9mm Ultrawide from Skywatcher. I hope the Sun will start showing a little more details in the H-Alpha band in the next few months. I really enjoyed the H-alpha sketching. It makes you look very careful for details.
I tried different eyepieces with the 4-inch TAL: the Vixen LV's, the Zeiss vario zoom-eyepiece and a 32mm Televue Plossl. The best overall view I got was from the 32mm Plossl. At a magnification of 30x the granulation was at its best, even better than in the Zeiss zoom. I noticed that the granulation gradually fades away with increasing magnification. I also compared the Zeiss zoom eyepiece (25-10mm) with the Vixen LV's (20, 15, 12, 10, 9, 7 and 5mm). Although the views through the high quality Zeiss zoom were slightly sharper and clearer than through the Vixen LV's, I still prefer the LV's for their great eye-relief of 20mm. With the Coronado PST I only used the 15mm LV. This eyepiece showed me the most pleasant view, and higher magnifications added almost nothing.
The visual impression you get from Sunspots with the Baader Herschel Wedge and the 4-inch refractor is hard to describe. No image I shoot comes near the sharp and detailed view I get live at the eyepiece, but I always shoot a few images to document the observing session in my observing log. The image below was shot with the Nikon Coolpix mounted on the Herschel Wedge using the 32mm Televue Plossl. The camera settings were 100 ISO, f 5.1, 1/125s and 4x optical zoom.
Click to enlarge!
In the centre of the image you see the active region 908. The more or less pear-shaped group has an area with a few umbra’s that seem to form one large umbra in the form of a cloverleaf. To the left of this almost circular feature lie several smaller dark umbra-like areas, divided by one or two light-bridges, I detected at a magnification of 100 times. The whole group is surrounded by a penumbra, which is also breached by the Lightbridge’s. The Lightbridge’s are not very clear on the image, but visually they where absolutely visible, as where the inner and outer bright ring around some parts of the umbra / penumbra. There where no faculae around AR 908 or on any other part of the Sun.
In H-alpha, the darker umbra’s where very easy to see, but I detected no bright patches in the AR 908 area (plages or flares). I did see two large bright areas around AR 907 and AR 909 (the two smaal groups towards the right edge of the image). Between 907 and 908 I detected a long, snakelike bright area. There where only a few smaller prominences visible. Between AR 908 and the edge of the solar disk I detected two dark filaments.
It is amazing what you can see with the PST. I shot the image below later that day. It should give you an idea of what I saw, but I have to admit that the image doesn't come near to what I actually saw through the small solar scope. The filaments looked like very fine threads and I cannot capture them as I visually saw them. But that goes for a lot of objects. I once observed M 13 under very good conditions with a superb telescope. There is no single picture that comes even near to what I saw that night. Any camera cannot beat the eye-brain combination. I'm sure of that.
Anyway, here's the best image I could shoot (and process) of this "flying" prominence. It was shot with the Nikon Coolpix 4500, image size 2272 x 1704, highest quality, iso 100, 1/8 second, f / 8.2. I used a 15mm Vixen Lanthanum eyepiece (magnification is about 26x) and 4x optical zoom. Image processing: level adjustment (in different color channels), brightness/contrast, hue/saturation (only in magenta) and unsharp masking.
What I also learned that day, is that there are probably two factors that are very important for getting good images: get the image focussed as good as possible and shoot a few series, so you can catch a moment of good seeing. I shot a few series in the morning, and I didn't get one good image. Around 12 O'clock local time I shot another series, with the same equipment and settings. I got significantly better images than a few hours before. Only two things could have changed: I re-focussed the camera and probably got lucky with moments of good seeing.
Click on images to enlarge
The images where shot with the Nikon Coolpix 4500, a 15mm eyepiece, full optical zoom, exposure 1/30s, ISO 100, f / 5.1, 2274x1704 pixels. Processing: level adjustment, contrast and brightness, hue/saturation and unsharp masking.
I also had the chance to have a look at the Sun in “white light” with my new Herschel Prism mounted on the TAL 100RS. On the image below (taken with the Coolpix 4500, a neutral density 3.0 filter and a Baader Continuum filter, ISO 100, exposure 1/500s, f / 2.6, 2272x1704 pixels. Processing: Contrast/brightness and unsharp masking) you can see active region 0810 in white light. The green color is caused by the Continuum filter. I didn’t find the time for more detailed images, because…. a lot of paintwork was still waiting.
This sketch should give you a general idea where the different features where situated on the solar disk.
1. Three large QRF’s (Quiet Region Filaments)
2. Active region 791 with a sunspot and two plage’s (white areas around Sunspot)
3. Active region 792 appearing at the limb of the Sun with bright plage
4. Big prominence, probably an active Class II eruptive (from Zirin classification)
5. Large hook shaped prominence.
The first two images where shot with a 10mm eyepiece and 2x optical zoom, 1/4s, f 10.3, ISO 100. The first image is the original image, slightly altered with some level adjustment and unsharp masking. Two filaments and the big prominence (4 on the sketch) are visible as well as the brighter area of Active Region 792 on the limb of the Sun (about 1 o’ clock). The second image shows only the green channel from the first image. The prominence disappears but the surface features are much better visible.
The next image shows a large part of the Sun, again only in the green channel. The original image was shot with a 12mm eyepiece, no optical zoom, 1/30s, f 6.6, ISO 100. Again some unsharp masking and level adjustments have been applied. On this image you can see the three filaments and at the bottom centre active region 791, a sunspot with some bright plage’s above and to the right.
The last image shows the big prominence. This image is an RGB one, but I split the colour channels, did some level adjusting, unsharp masking and curves adjustment only in the red channel, before merging the three channels together again. This produced a more or less realistic image of the big prominence, but a lot of testing and training has to be done. However, this being the first images shot through the Coronado PST, I am very satisfied. If you want to comment on the images or have some more tips for me, please feel free to do so! You just have to register once and you can always log into the comment fields.
Clear skies to all of you!
UPDATE friday 29 July 2005 at 14.00 hrs UT !!!!!
At the moment there is a big prominence visible as well as the active region AR 792. Here are some images from some two hours ago (click to enlarge!)
Enjoy the images for now. Details on the images will follow within the next few days. I will keep you updated.
This morning I observed and photographed two groups of sunspots, NOAA 0756 and 0757. After months I got a chance to have a look at some sunspots with the refractor. It was very hot (28 degrees Celsius); there where no clouds, and the sunspot group 0756 was large and impressive. I noticed while shooting the images that with higher magnifications and/or optical zoom the exposure times get longer, and the seeing gets more disturbing on the images. I hope that the new Herschel prism from Baader (still waiting on it) will give me more light at higher magnifications and much shorter exposure times.
The first image was shot with the Nikon Coolpix using the TAL 100RS 4-inch refractor and a Televue 32mm eyepiece with 1x optical zoom. The second, more detailed image was shot with the same telescope and camera, but with a 20mm Vixen Lanthanum eyepiece and 4x optical zoom. The big sunspot group is NOAA 756 and the smaller group to the right is NOAA 0757.