From: Alan Friedman <alan@greatarrow.com>

Date: March 19, 2012 11:06:04 AM MDT

To: Astro_IIDC@yahoogroups.com

Subject: Re: [Astro_IIDC] Wrestling with Venus

Thanks Milton... yes, shooting in the waning hours of sunlight, 7 to 7:30 local time. It was a beautiful clear day and as soon as the sun set, the heat radiation sent the seeing into a tailspin. 

I purchased the K-line filter for solar work primarily, but found it suitable for Venus, though very narrow as you point out. Normally, Venus is out of reach for me from my backyard pier, but now that we have a nice planetary instrument at the club observatory I might look to add a more traditional UV filter to my collection.

best,

Alan

On Mar 19, 2012, at 12:56 PM, Milton Aupperle wrote:

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
>