Imaging the Sun in a very narrow band centered on the h-alpha emission line (656.3 nm) yields some of the most stunning images of our star, which show a wealth of details and features on the solar surface which are not visible in white light. I have recently built a so-called “modified PST” solar telescope from a used Coronado PST. The instrument is still “work in progress” and I will most likely report on its construction in another article.
I left my solar telescope to collect dust for a quite a while, but in the month of October 2014 a huge sunspot group, called “AR 2192” (see for example here), put on a really impressive show. This revived my interest in solar imaging and kind of “forced” me to find the time to acquire some images. Unfortunately not under the best observing conditions, because it was very close to the solar limb and it would very soon disappear from view into the invisible side of the Sun.
The weather had been awful over Northern Italy during the first half of October, but fortunately it got better in the last days of the month. Therefore, I set up my equipment and concentrated all of my imaging effort around 1 pm on October 27th and 28th.
The “host” telescope of my modified PST is a 1000-mm f/10 refractor, which was stepped down to 70 mm by adding a Baader ERF filter in front of the objective, while the rest (etalon + blocking filter) was taken from a Coronado PST. This resulted in a telescope offering decent views, but with a very narrow useful field. This makes it more suitable for digital imaging rather than for visual observation.
Unfortunately the seeing was very bad during both imaging sessions, therefore I had to use my camera (a PGR Chameleon) only at the prime focus, without being able to increase magnification (e.g. through a barlow lens).
Below is a selection of my best shots. They look quite different from each other in both hue and details, because they were processed while experimenting with different techniques and software (Autostakkert, Registax and Photoshop). The overall result is not really top-notch, but I think that it was very interesting to give it a try. And anyway, I’m pretty sure there is some room for improvement in all respects: telescope, weather (particularly the seeing), and in the processing.
One last note: all times in the captions are expressed in UT.
On October 28, I briefly drew my attention away from sunspot group AR2192 to image some other features on the solar surface, such as the prominence below, but the final result outcome is nothing special:
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