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The visibility of Venus Venus is the only planet or star that can be seen by the naked eye during the day. Following the
 

Summary: The visibility of Venus
Abstract
Venus is the only planet or star that can be seen by the naked eye during the day. Following the
method of Westheimer (1985) for representing a point source as a single pixel on a screen with
a resolution of 120 pixels per degree, we can convert the magnitude of Venus and the sky
luminance into a luminance contrast signal with a contrast of 2.22. Detection models calibrated
to the Modelfest data predict that such a target is below threshold (Watson and Ahumada,
2005). Modifications are proposed to the models to keep Venus visible.
A Digital Venus
Following Westheimer's (1985) suggestion for representing a point source on a digital
display, we set the display resolution to 120 pixels per degree and solve for the contrast
needed to represent Venus. Using a sky luminance measurement of 4200 cd/m^2 (Minolta
CS100A) , the required single pixel contrast turns out to be 2.22.
The assuming an effective duration of 0.25 sec, the contrast energy relative to 10^-3
degree^2 seconds is 19.3 dBB.
Figure 1. The phases of Venus. At its
closest approach, Venus subtends 66
arc seconds. (credit: TBGS
Observatory, photo by Chris Proctor;
http://venus.aeronomie.be/

  

Source: Ahumada Jr., Al - Vision Science and Technology Group, Human Factors Research and Technology Division, NASA Ames Research Center

 

Collections: Engineering