Unequal Double Star Split Calculator - Chris Lord (1994) telescopic performance index algorithm for secondaries brighter than 13.0 magnitudes

K. Fisher fisherka@csolutions.net Rev. 2/3/2008


Chris Lord Algorithm Unequal Double Split Calculator

Aperture (mm): Magnitude of primary: Magnitude of secondary:
Aperture class (mm): Obstruction percent: Seeing (spurious disc radius):
Minimum TFOV separation to resolve: (arcseconds) during periods of stability in turbulent air

Calculator assumptions: Primary brighter than 9.0, the secondary is brighter than 13.0, the secondary is between 0 magnitudes and 7 magnitudes dimmer than the primary.

Table 1 - Antoniadi's 5 point seeing scale
ScaleDescriptionDisk diameter computed from D_mmDisk diameter for 8" (203mm) to 20" (508mm) scopes per the Canadian Weather Service Corresponding Lord's step
I Perfect steadiness; without a quiver. < 0.4"I<0.25 rho
II Slight undulating, with moments of calm lasting for several seconds. ~ 0.4-0.9" II>0.25 rho
III Moderate seeing, with larger air tremors. ~ 1.0-2.0" III<0.50 rho
IV Poor seeing, with constant troublesome undulations. ~ 3.0-4.0"IV<1.00 rho
V Very bad seeing, unsuitable for anything except possibly a very rough sketch.< 4"V> 1.50 rho

Source: Antoniadi scale wikipedia
Canadian Weather Service. http://weatheroffice.ec.gc.ca/astro/seeing_e.html
Lord, C. Jan. 2008. Personal Communication.
Notes: Lord's seeing performance characteristic ( n_e * rho) is expressed as a radius. The third column above is twice that radius - a diameter - in order to be comparable to the Canadian Weather Service table.

Math Appendix

Chris Lord's algorithm is:

References

Lord, Chris. 1994. Nomogram for Telescopic Resolution of Unequal Binaries. Brayebrook Observatory. http://www.brayebrookobservatory.org/BrayObsWebSite/HOMEPAGE/BRAYOBS%20PUBLICATIONS.html

Lord, Chris. 1994. A Report on the Analysis of the Telescopic Resolution of Unequal Binaries. Brayebrook Observatory. http://www.brayebrookobservatory.org/BrayObsWebSite/BOOKS/TELESCOPIC%20RESOLUTION.pdf

Lord, Chris. Jan. 2008. Personal Communication.

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Prepared K. Fisher fisherka@csolutions.net org. 7/2006 rev. 2/3/2008