Re: the mag the Sony 4 lux camera is capable of seeing

From: Björn Gimle (b_gimle@algonet.se)
Date: Wed Jun 04 2003 - 05:03:05 EDT

  • Next message: Willie Koorts: "Re: the mag the Sony 4 lux camera is capable of seeing" 

    One number doesn't confuse me - Magnitude is 2.5 * 10-LOG(Brightness)
Or Brightness = 2.512^Magnitude
LOG(100)=2, so 100*  = 5 mag
2.5*LOG(16) = 3.01
2.512*2.512*2.512=15.85

But lux ratings do: If I remember correctly, my five year old Sony Hi-8,
which my children now use, has a rating of 0.7 lux in normal mode (there
is no NightShot) and at max optical zoom (12*?) I got ten stars in the
Pleiades, and at least three Jovian moons.

Since then, most cameras boast "0 lux"! (<0.5?)

An article in S&T Feb-2003 compares Meade Electronic Eyepiece ($70, no
lux rating), PC164C ($130, 0.0003 lux), PC165C ($230, 0.05 lux) and
StellaCam-EX ($700, 0.005-0.000005!) - and uses different scopes,
different subjects and different exposures to compare (!) some results.

Rainer Kracht uses an integrating Mintron 12V1C-EX and lens f=75mm f/1.3
to get satellites down to +12.
Greg Roberts' 1004x gives him satellites down to +8.3 with 0.003 lux and
an 82 mm f/1.6 lens.
Several messages on SeeSat-L (and DSat).

With 11-inch scope and 0.0003 lux, S&T only got to mag +10

/Björn

----- Original Message ----- 
From: "Tom Wagner" ...
> etc. I did some starlight magnitude tests with my Sony digital video
camera
> [DCR TRV 340]. Following are the results.
>
> The lens setting was 50 mm, F 2.4 at 20X magnification.
> The imaging device is a 1/6", 460K gross pixels CCD.
> The video was actually 290K Pixels.
> The minimum illumination capable of being perceived is 4 Lux
> Using the so-called "NightShot" mode I could barely see a star that was
mag.
> +3.
> Using the "Super NightShot" mode I could barely see a star that was
mag. +6.
...
> According to Sony the Super NightShot mode is about 16 times brighter
than
> straight NightShot.
>
> Now can someone tell me how 16 times correlates to 3 magnitudes in
> brightness?
>

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