Conversion Calculator - NELM (V) to MPSAS (B) systems

K. Fisher fisherka@csolutions.net Rev. 3/17/2008

Math Appendix

• Convert NELM (V mags) to MPSAS (B) sky brightness

• Formula: B_mpsas = 21.58 - 5 log(10^(1.586-NELM/5)-1)
• Source: Schaefer, B.E. Feb. 1990. Telescopic Limiting Magnitude. PASP 102:212-229 http://adsbit.harvard.edu/cgi-bin/nph-iarticle_query?bibcode=1990PASP..102..212S

• Convert MPSAS (B) sky brightness to NELM (V mags)

• Formula: NELM=7.93-5*log(10^(4.316-(Bmpsas/5))+1)
• Source: Olof Carlin, Nils. About Bradley E. Schaefer: Telescopic limiting Magnitudes . . . . Web page discussion of brightness in Schaefer (1990) and Clark (1994). http://w1.411.telia.com/~u41105032/visual/Schaefer.htm (accessed 7/2003)

• Convert extended object size (arcmins) and apparent brightness (V) to MPSAS

• Formula: objB_mpas = objMagnitude + (2.5 * (Log10((PI() / 4) * objMajorAxis_arcsec * objMinorAxis_arcsec)))
• Sources:
  Clark, R.N., 1990. Appendix E in Visual Astronomy of the Deep Sky, Cambridge University Press and Sky Publishing.http://www.clarkvision.com/visastro/appendix-e.html
  Covington, M. (1998, 2d). Appendix A, Astrophotography for Amateurs. pp. 259-261 http://www.covingtoninnovations.com/

• Compute an extended object's contrast index

• Formula: ContrastIndex = -0.4 * (objB_mpas - B_mpas)
• Source: Clark, R.N., 1990. Appendix E in Visual Astronomy of the Deep Sky, Cambridge University Press and Sky Publishing.http://www.clarkvision.com/visastro/appendix-e.html

• Test data

• See Clark, R.N., 1990. Appendix E in Visual Astronomy of the Deep Sky, Cambridge University Press and Sky Publishing.http://www.clarkvision.com/visastro/appendix-e.html

Revisions

• 3-17-2008 - Substituted long from of Schaefer-Garstang NELM conversion for Nils Olof Carlin's short forms. Change was intended to better integrate results return here and online Schaefer limiting magnitude calculators. Carlin's short verison is limited sky brightness of mpsas 19.1 or higher. The Schaefer long form extends accuracy of returns to some light-polluted skys down to NELM 2.0.

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Prepared K. Fisher fisherka@csolutions.net rev. 3/17/2008