From: Milton Aupperle <milton@outcastsoft.com>

Date: March 2, 2010 11:45:42 PM MST

To: Astro_IIDC@yahoogroups.com

Subject: Re: [Astro_IIDC] ExoPlanet Database

Hi Terry;

On 2-Mar-10, at 9:39 PM, Terrence R. Redding, Ph.D. wrote:

Milton, thank you for this.

I am one of those who will be trying.  BTW, what camera would you recommend I use?

Likely something with at least 12 bits of depth per pixel, cooled and low noise.

A 0.01 drop in magnitude is about a 0.93 % change in brightness.

A 8 bit camera  has 256 shades of gray, that means the the pixel will change in value by about 2 out of 255 for a 0.01 mag change. With any CCD noise, your going to lose this change in the background noise, so it's pretty unlikely you could detect a change of less than 0.03 mags.

A 16 bit camera has 65536 shades of gray, so a 0.94% change would be reflected as change of 655 out of 65536.

I've measured my Grasshopper 14 bit camera's noise level (at minimal gain of 64) and it comes out to be a random change of +/- 25 out of 16384. So theoretically I can detect a change of about +/- 0.15% change in brightness, which would be about 0.0017 magnitudes.

However I have never gotten lower than about +/- 0.01 magnitudes because of atmospheric issues (haze, turbulence etc.) in the attempts I've made under dark skies for 90 second exposures, which would be the correct exposure for about Mag 12 stars.

HTH..

Milton Aupperle

Terry - W6LMJ - 14.287

Terrence R. Redding, Ph.D.

Redding Observatory South, West Palm Beach, Florida

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