From: Milton Aupperle <milton@outcastsoft.com>

Date: October 21, 2010 1:01:24 PM MDT

To: Astro_IIDC@yahoogroups.com

Subject: Re: [Astro_IIDC] solar mosaic reattacked!

Hi Jim;

On 21-Oct-10, at 12:38 PM, Jim Chung wrote:

Milton,

Your message may clarify how to shoot Ha flats for me.  I tried it

last weekend by pointing the scope to a clear patch of sky but of

course the Ha signal was so weak that I could get nothing, even with

insanely long exposures.

What does "insanely long exposures" mean in real terms?

1 Second, 10 seconds, 2 minutes??

Also, Gain can be increased as long as your shooting numerous flat frames to average the pixel variance, out.

Normally I create a Master Flat frame using the "Grab Avg. Frame" (page 87) and then use "Flat Frame Correct Movie…" (page 56) to post process the movie and balance things out. I leave the camera attached to the scope and always focus first before creating a Flat so it will remove dust on filters or CCD too.

When I do dark frames, I use up an entire night creating them. For exposures ranging from 1 minute to 20 minutes and usually average 4 to 20 frames for each average master dark I create.

So I should keep it pointed a the middle of

the sun and increase the exposure until the surface detail is washed

out?

Nope, that will not work.

But doesn't that simply oversaturate the ccd pixels?

Yes it does.

For a Good Flat, you want the pixels to have about a mid range values (128 for 8 bit, 32,768 for 16 bit).

HTH..

Milton Aupperle