Tuesday, February 14, 2006

11 Feb 2006

This is a H-alpha solar observation party organized by HKAS. This is the 3rd or 4th time which I joined their observation in all these years, due to my family engagement.

Observation location in Hokoon in Tsuen Wan, around $25 HKD taxi from Tsuen Wan MTR station, it hosts the biggest robotic telescope in Hong Kong, at least once the biggest.

On the spot were several setup, mine is a SM40/Ranger/binoviewer/TGSP2, a close by is a internal double stacked maxscope 60mm with video camera (Watec), a CaK setup on a maybe 3" refractor, a double stacked SM60/Sky90/Tak EM2 with Lumenera Infinity 2-1 camera.

The sky was bad, very foggy. The view on my setup were very dim, featureless in the first glance. Similarly for the CaK setup, it was bright, but again looked featureless.

On looking through the internal double stacked setup, the contrast was much washed out by the dirty air, but still, we can see some feature, a quite long filament too despite there is no sunspot at that moment. A bright patch can be seen near the filament end.

Upon discovering the feature, I can locate all of them from my setup as well. And then I switched to the CaK setup and saw the same bright patch. Not bad.

We did some side by side comparison of the two 60mm double stacked system.

1. The internal one gives a dimmer view, slightly less contrasty, but no ghost image to begin with

2. The external one gives a brighter view, more contrasty and a ghost image which should be removed by tilting the Tmax.

Double stacking provided a dramatic difference. The internal one is matched by Coronado but the external one were obtained without matching, so you see external double stack really better.

For photographic usage, I would say better aperture should be better since it provides more resolution. However, without great contrast, resolution means nothing since you cannot differentiate subtle difference due to the lack of aperture. Resolution and contrast are twins. Having said that, I'd rate aperture more important than bandwidth for photography, and bandwidth more important for visual observation.

For photographic purpose, the b/w toucam which I just acquired in the same morning didn't work at all. So, we only have Lumenera and Watec b/w video camera for comparison. Frankly, both work out great... I'd prefer the far more expensive Lumenera a bit for image quality, due to the higher frame rate and bigger dynamic range.

Video setup is good in the sense that the head is lighter, a DV recorder will be easier to operate and the battery will last much longer than a notebook. That Watec features a 1/2" CCD chip which is enough to encapsulate the whole solar disc and with propose powermate/barlow, high level detail can be obtained without problem.

With video system, you can have PAL to get more pixels at 25 fps, or NTSC at VGA but 30 fps.

An eye opening event, too bad that the sky does not very much cooperating.

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