We have an interesting visitor at the Curdridge Observatory - a solar Hydrogen Alpha filter. It is a Daystar hydrogen alpha university filter assembly rated at 0.5Å. This filter cuts out all the light except for a narrow band around Hydrogen Alpha. This allows us to see interesting detail on the disk of the Sun, and also flares coming out of the side of the Sun. A whole new world of solar imaging.
A phone-photo of the scope and filter in the back garden.
A closer shot of the filter with an eyepiece attached.
This type of solar hydrogen alpha filter is rather expensive. It incorporates a heater system and needs 45 minutes to warm up to working temps. Sadly it does not belong to us - it is just on loan for a few weeks. The winter is not the best time for solar imaging, but we did not let that stop us.
Naturally we use our webcams. We have used an SC3 modified webcam and a SC1 modified webcam with a black and white ICX908BL ccd chip instead of the normal colour one. With such a narrow bandwidth of light, it is a bit pointless to use a colour CCD chip.
We used our Meade LX200 telescope mounted in ALT-Az mode installed on the tripod at the Netley branch of the Curdridge Observatory. We used the cameras with and without a Meade 6.3 focal reducer. On the front of the scope is a sub aperture energy reduction filter.
Looking down a 26mm Meade Series 4000 eyepiece with the filter warmed up we could see good detail around the major visible sunspot. The would also see the "orange peel" effect on the surface of the sun, and some small flares leaping off the limb of the Sun. The image, as expected, was a deep red colour.
Our first image is a stack of 250 frames showing the main visible sunspot group. This uses the SC3 webcam with the black and white ICX424 ccd sensor. The 6.3 focal reducer is also in the imaging train. Captured in k3 and stacked in Registax. Curves and slight blur in photoshop.
This next image is after we swapped over to the smaller camera. The ICX098 chip has smaller pixels than the SC3 camera. This gives a smaller field of view and a better image scale. We stacked some 600 frames of this flare on the limb of the Sun. Using a longer exposure and more gain we saturated the disk to pick up the fainter details in the flare.
Again with the smaller camera - the same sunspot group as above. I find the wider field more pleasing, as its less effected by the very poor seeing due to the extremely low winter declination of the Sun.
Removing the focal reducer gives this image. Again, seeing makes things even harder... and of course the sun was getting steadily lower and lower.
A shot of a smaller spot with the sc3 and the focal reducer on. Looks like tasteless wallpaper to me. ;-)
We are very much beginners at using this combination of equipment, but the initial results with this remarkable filter are promising. With a higher sun and a bit more experience, good results should be possible. Mind you, for that amount of money, I'd hope the results are good! NB Not sure how long we can hold onto this toy for - I'd have thought next summer might be pushing it a bit.
