Magnitude where the Pale Dot is blue?

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SUMMARY

The discussion centers on the color and magnitude of Earth, referred to as the "Pale Blue Dot," in comparison to other celestial bodies. The BV color indices and magnitudes of various planets and stars are analyzed, revealing that Earth has a BV index of +0.2, while other notable celestial objects like Venus (+0.82) and Mars (+1.33) are also discussed. The conversation references a NASA report for detailed color indices and emphasizes that the visual perception of color may vary with intensity, questioning the reliability of the BV index as an indicator of visual response.

PREREQUISITES
  • Understanding of BV color indices in astronomy
  • Familiarity with celestial magnitudes and their significance
  • Basic knowledge of the Voyager 1 mission and its imagery
  • Awareness of color temperature concepts in astrophysics
NEXT STEPS
  • Research the NASA report on BV color indices for a comprehensive understanding
  • Explore the impact of intensity on human color perception in astronomy
  • Study the differences in visual response between various celestial bodies
  • Investigate the methods used in the Voyager 1 imaging process
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Astronomers, astrophysics students, and anyone interested in the visual characteristics of celestial bodies and their comparative analysis.

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Earth is called Pale Blue Dot.
The famous picture of Pale Blue Dot with Voyager 1 from 40 AU is taken with a camera which is not assured to have the correct magnitude or colour sensitivity of naked eye.
As for BV colour indices of planets and one satellite, Wikipedia links to a Nasa report:
https://ntrs.nasa.gov/api/citations/19710009758/downloads/19710009758.pdf
It has more entries, but the major ones:
  1. Sun +0.63
  2. Mercury +0.97
  3. Venus +0.82
  4. Earth +0.2
  5. Moon +0.92
  6. Mars +1.33
  7. Jupiter +0.83
  8. Io +1.17
  9. Europa to Callisto all about +0.85
  10. Saturn +1.04
  11. Titan +1.3
  12. Uranus +0.56
  13. Neptune +0.41
Now compare the brightest stars...
  1. Sirius A0 magnitude -1.46, index 0.00
  2. Canopus A9 magnitude -0.74 index +0.15
  3. Rigil Kentaurus G2+K1 magnitude -0.27 but colour index quoted separately for components - A magnitude +0.01 colour index +0.71, B magnitude +1.33, colour index +0.88. I get colour index for AB approximately +0.75
  4. Arcturus K0 magnitude -0.05 colour index +1.23
  5. Vega A0 magnitude and colour index 0 by def
  6. Capella K0 magnitude +0.08 colour index +0.80
  7. Rigel B8 magnitude +0.13 colour index -0.03
  8. Procyon F5 magnitude +0.34 colour index +0.42
  9. (omitting from now on various A and B stars because they´re all bluer than Earth)
  10. Betelgeuse M1 magnitude +0.50 colour index +1.85
  11. Aldebaran K5 magnitude +0.86 colour index +1.44
  12. Mirfak F5 magnitude +1.82 colour index +0.38
  13. Sargas F0 magnitude +1.84 colour index +0.21
Judging by colour index, Sargas should look like Earth.
At its magnitude, does Sargas look like "pale blue dot"? Does Canopus?
 
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I believe the Blue/Visible (BV) index is used as an index of color temperature and is not a particularly good indicator of expected visual response. The response of the eyeball to color is likely to change with intensity. I have never personally played with it.

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