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Observing the Sun in different wavelenghts
Yesterday I observed some interesting active regions on the Sun, especially AR 908. I used the 4-inch refractor and the Baader Herschel Wedge (with the Baader Continuum and ND 3.0 filters) for "white light"? observing and the Coronado PST for the H-Alpha line.

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.


image
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.
Posted by Math on 09/10 at 02:47 PM
Solar log • (6) CommentsPermalink

Hi again Math.

Your pictures of Sun in white light are beautiful.

I was always wondering about the granulation in white light and I’m thinking in getting one of these Herschel wedges mainly for my ED80 refractor but also for my Tak FS60C. However I’m not sure if I have refractors with aperture enough to observe these structures as I tried it previously with Baader Astro Solar film and Solar Continuum filter mounted on my ED80 and got very faint view of granulation. I have some question for you (sorry if they are so much):

Do you think 80mm of aperture would be enough to see granulation with a Herschel Wedge?

Do you notice great improving of the Herschel Wedge over the Baader Astro Solar film?

Have you heard about the Intes Herschel Wedge which seems to be cheaper but with worse protected against heat and light cone?

BTW, I recently received my fixed PST from Meade Europe (rusty objective replaced) and my impressions are that now I can reach more power than before with more level of detail. I even mounted a 10mm eyepiece barlowed 2X (5mm effective) and got detailed views of the H-Alpha features. It seems to me you should push your PST more than 15mm eyepiece. With my previous PST I was very comfortable with 7.5mm Ultrascopic eyepiece.

Thanks.

Posted by Julio Cesar  on  10/16  at  12:31 PM

Hi Julio,

1. Granulation.

I noticed that the smaller the aperture of the telescope, the better you see the granulation. It seems that you have two high quality telescopes that should show some granulation, but I am not 100% sure. I will check with a fellow observer from the local astronomy club. He observes with a 80mm Williams Optics telescope. I will let you know what his experiences are with the granulation.

2. Herschel wedge versus Solar Film.

In june we had a solar observing session with the local astronomy club. Everyone, evn the experienced observers, agreed that the new Baader Herschel Wedge with the Solar Continuum Filter (540nm in green light) gave the best contrast we had ever seen. Sunspots are much darker, the granulation is visible, and the Sun stands out against a black sky. A wonderful sight! Definitely better than the standard solar film, and when used properly, 100% safe. FOLLOW THE SAFETY PRECAUTIONS that come with the wedge.

3. I know the Intes is much cheaper, but the thing with the Baader is, that it is much safer and that the filters (Continuum and 4 different Neutral Density) are of a very high quality. The wedge itself (the mirror that bends of 90% of the light, and only reflects 10% up to the eyepiece) is made by Zeiss, a very high quality.

Please check the site of Baader Planetarium (I think its also available in english language) for the PDF’s on the Herschel Wedge and about the safety of using it. Before buying it, contact them if your refractor is OK to use with the wedge. There should be no plastic parts or glued lenses in the path of the light.

Clear skies

Math

Posted by Math  on  10/16  at  01:23 PM

Thanks for the info Math.

If you could talk with your fellow about views with the WO 80mm it could be useful for me.

Thanks also for your advises on safety. I didn’t find any amateur in Spain with a Herschel Wedge but read a lot about this accesory on forums. I’ll give some more tries to my Solar Continuum filter with the Astro Solar Film and low power eyepieces as per your experiences.

Clear skies.

Posted by Julio Cesar  on  10/16  at  03:44 PM

I just received a phonecall from my fellow observer. He tested the 80mm Williams with the Solar Screen, and with low magnification, he saw the granulation very clear. With the binoviewer he even saw the granulation better! He also noticed that with increasing magnification the granulation starts to disappear.

So generally, he got the same experience as I have with the 100mm refractor. With low magnification, the granulation is very easy to see, with high magnification it disappears. The Herschel Wedge will definitely increase the contrast even more, and the granulation will be even more visible.

Hope this helps.

Best regards

Math

Posted by Math  on  10/17  at  02:22 PM

Thanks a lot for the info Math.

I’ll test several magnifications during my next solar observing session (cloudy now at Madrid).

I found good commentaries about the Intes/APM Herschel Wedge and it seems that optically is a good quality prism. Problem is the heat and light exhaust is not very well controlled as in Baader wedge. Anyway it seems quite easy to control it and price difference will worth the effort, in my opinion.

I’ll continue investigating about the Herschel Wedge before taking a decision.

Thanks again for your good website and for sharing your experiences.

Clear Skies.

Posted by Julio Cesar  on  10/18  at  02:25 AM

hi math

i am not too familiar with photography,

My question is how do sunspots come into play when you take photographs that inlude lots of light

Posted by andrew77  on  11/19  at  09:48 AM

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