From: "Terrence R. Redding, Ph.D." <tredding@mac.com>

Date: September 27, 2009 4:04:32 PM MDT

To: Astro_IIDC@yahoogroups.com

Cc: Richard Nugent <rnugent@wt.net>

Subject: Re: [Astro_IIDC] Version 2 of Eros Light Curve and movie

Very good Milton.  Your comments are always appreciated.

I  believe I will try to do some photometry and astrometry with the camera I have tag  along with Richard Nugent as my guide and you as the teacher - with your software.  It will be a great learning experience to be able to compare our results.

I don't recall now whether Richard will be using his 14" scope or not.  I f he is he will have excellent dark skies compared to the sky glow I content with here in West Palm Beach.

Terry - W6LMJ - 14.287 

Terrence R. Redding, Ph.D. 

Redding Observatory South, West Palm Beach, Florida

http://olt.net/learningstyle/Site_2/Learning_Style_Research.html

How do amateur astronomers learn?

American Association of Variable Star

Observers (AAVSO): RTN http://www.aavso.org/

On Sep 27, 2009, at 5:15 PM, Milton Aupperle wrote:

Hi Terry;

Thanks for the compliment. I hope to re-shoot it in the next few
weeks, after the moon wanes.

For positional measurements the bit depth isn't going to matter as
much as it would for photometry. However it does make it easier to
detect faint stars with higher bit depth, like a Flea 2 (12 bit) or
Grasshopper (14 bit) monochrome.

With the Grasshopper EXHad camera using an AstroDon Clear (IR Cut)
Filter, I'm just reaching magnitude 19 to 20 the stars with 7 minute
exposures on my C8 from Calgary. That's with gains at minimum (to
reduce amplified noise), binned 1x1 and with somewhat light polluted
skies (about 1,190 ADU per minute of exposure). the light pollution is
what hurts the most with detecting faint objects, as they get lost in
the background "grayness".

A 14" will have 300% more light gathering capability than my C8 does,
so with a similar camera you should be able to reach the same depth
with a 2.3 minute exposures. If you run binned 2x2 then you can cut
the exposure time down to around 35 seconds and with moderate gains
likely can go that deep in less than 15 seconds. Binned 4x4 will cut
it down to about 9 seconds, but it will amplify the background light
pollution a lot too.

The Grasshopper will require cooling to keep the CCD from generating a
lot of hot pixels. The Fleas and Flea 2's are less susceptible to this
than the EXHAD models, but the HAD CCD's they use are also less
sensitive than the EXHAD. So it's all tradeoffs as far as sensitivity
and noise goes.

HTH..

Milton Aupperle

On 26-Sep-09, at 11:23 PM, Terrence Redding wrote:

>
>
> MIlton, very nice work.
>
> I was telling Richard Nugent about Astro-IIDC earlier tonight. He
> and I were discussing cameras to use for B&W imaging to support
> astrometry work. He is primarily interested in improving the
> positional data of asteroids and has a 14" LX200 to work with, as do
> I. He is interested in working with objects to 19th magnitude if
> possible.
>
> What camera would you recommend for such an effort? As you know I
> have the DMK21, but possibly a higher bit rate or larger chip?
>
> As always your comments will be greatly appreciated.
>
> Terry - W6LMJ - 14.287