From: Alan Friedman <alan@greatarrow.com>

Date: February 15, 2010 9:02:38 AM MST

To: Astro_IIDC@yahoogroups.com

Subject: Re: [Astro_IIDC] Sun..

Hi Mark,

I often set the gamma below 1 (.9 typically) when capturing prominences and above 1 (1.25) when capturing the solar chromosphere ("surface" in Hydrogen Alpha). I'm not sure I understand your exposure... the FPS rate will be constrained by the chip size and bit depth to 15 or 7.5 fps, but the shutter setting should be very fast yielding a short exposure.

You might enjoy this picture:

http://www.avertedimagination.com/images/thierryandgreg.jpg

of the great French imager Thierry Legault (whose article you referenced in your previous post) underneath my solar observing cloth at NEAF a few years back... also posing with Greg Piepol and his impressive solar set-up.

cheers,

Alan

On Feb 15, 2010, at 10:33 AM, Mark Gaffney wrote:

Alan,
Should the Gamma stay at 1.0 for the Sun as usual? I tried everything
possible this morning & couldn`t get anything decent-unless my
collimation is significantly out, which seems probable after removing
the secondary?With the Scorpion I began with the Baader IR/UV filter
as you advised then removed it & had just the nosepiece on the camera.
Whilst I could see a nice sunspot I couldn`t bring it to focus. The
Base exposure was 133 ms although I tried upping it to 266 ms & beyond
all the time playing with the exposure slider, fps & incremental
selections. I had the brightness mostly right down & no colours for
the B/W Scorpion.

..I did try your dark cloth over my head & the lap-top screen like one
of those old time photographers but it kept slipping when I reached
for the focusing knob! (I had some clothes pegs holding it on the
screen) Sorry I don`t have anything to show for it..!

Mark.