Friday, August 15, 2008

20080815 Sun (DSLR)

First time really got chance to try out DSLR with H-alpha solar filter, but I didn't get enough time to do tracking, so I'm doing all things on fixed tripod.

Seeing is very poor since the sun is very low already, transparency dropped due to the low angle as well. The sun is pretty inactive, too. I can see some very subtle prominence.

A very slight hint of the prominence at the lower right corner, 1748 (GMT+8), focus way off... exposure is hard to control for color CMOS, red is way saturated, but green and blue is under... so none of the channel is useful. SM40/BF10/Borg 45ED II at prime focus:-

This is taken with a 2x barlows, red channel is saturated, while green and blue channels are void.

This is taken with a 2x barlows too, red channel is again saturated, green is a bit over and blue is useful but noisy.

DSLR and H-alpha is very hard to do, live view is used but the focus is still very hard to determine. I guess it could be better when the sun is more active. And I guess a modified DSLR should be better, since H-alpha signal is effectively removed by the low pass filter, so now what we're capturing is from signal leakage, and thus the high noise level. Green and Blue channel will be even worse since they both require even stronger signal leakage.

Not an good tool indeed.

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