From: Milton Aupperle <milton@outcastsoft.com>

Date: March 19, 2012 10:56:23 AM MDT

To: Astro_IIDC@yahoogroups.com

Subject: Re: [Astro_IIDC] Wrestling with Venus

Hi Allan;

Very nice image and super detail. Were you shooting it during the day or in the evening?

Glad to hear it worked for you.

That's a very narrow bandwidth filter.

If you look at something like the AstroDon UVenus filter:

http://www.astrodon.com/products/filters/uvenus_filter/

it transmits ~ 98% light in the range of 325 - 381 nm (range of 56 nm) , so it would be letting in ~ 7 times as much light as an 8 nm filter width does.

TTYL..

Milton Aupperle

PS: Did you use Astro IIDC 4.08.00 Alpha 03 for the processing or not?

On 19-Mar-12, at 10:24 AM, Alan Friedman wrote:

Greetings,

Here is an image of Venus prepared from data collected with the C14 at our club Observatory.

http://www.avertedimagination.com/img_pages/wrestling.html

It had been several years since I had wrestled with Venus - I had forgotten how much the transmission drops in near UV wavelengths through optical glass. This, and the sensitivity drop off on the CCD chip of my Flea 3 camera makes for a huge increase in exposure when imaging at the 395nm wavelength of CaK... I would estimate 40X that of green light with the gain at maximum. The frames were very difficult to work with, but this is where the cloud tops become visible, so wrestle we must. Once I settled on the best settings in AstroIIDC, the software did a good job of estimating quality from some very noisy raw frames.

clear skies and best wishes,

Alan

Alan Friedman

avertedimagination.com