From: "Milton Aupperle" <milton@outcastsoft.com>

Date: March 29, 2009 10:37:19 PM MDT

To: Astro_IIDC@yahoogroups.com

Subject: Re: weekend solar images

Hi Alan;

No problem.

Thanks for the details.

I always wondered what you sort of focal length, exposures and gains you used for shooting prominences.

With a 16 bit camera, you might have enough bit depths to record both the disk and prominence in a single (post stretched) frame.

TTYL..

Milton Aupperle

--- In Astro_IIDC@yahoogroups.com, Alan Friedman <alan@...> wrote:

Hi Milton,

Thanks for the note. Apologies for not providing more technical info -  

I am really an image person at heart (but I think you already know  

that!).

The set-up uses the A-P stowaway (FL=450mm) and the Baader FFC with a  

2.5 inch extension. I've not measured it exactly but I think the  

effective focal length is in 1500-1600mm range. Settings vary with  

each, but a good average is:

exposure: 23ms

gain: 600

gamma: .9

The captured streams are 600-900 frames in length - 100-150 frames are  

selected for stacking. Seeing is very poor overall, but there are a  

small number of sharp frames in each stream. Anticipating the dwell  

moments between high turbulence while capturing and then evaluating  

and hand selecting the data for stacking are the two most challenging  

parts of the process.

For those who might be interested, I will be doing a presentation on  

solar and lunar imaging techniques at the Mid-West Astro-Imaging  

Conference in June.

best wishes,

Alan