From: Milton Aupperle <milton@outcastsoft.com>

Date: September 27, 2009 3:15:50 PM MDT

To: Astro_IIDC@yahoogroups.com

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

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