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"Možda su crne tačke bile ptice u letu..."
(Maybe the black dots were birds in flight)
Notes on
AMATEUR TELESCOPE OPTICS
On an early autumn day of 1608, Hans
Lipperhey, a spectacle maker from Middelburg, in the Netherlands'
coastal province of Zeeland, applied before the States General of The
Hague for a patent on an "instrument for seeing far". By that time, use
of small rounded glass disks to aid the natural eyesight wasn't new. Those
bulging out on both sides, resembling lentil - or "lens" in
Latin - have been used to correct for farsightedness since the mid 13th
century. The idea of a device for magnifying distant objects may have been already
grasped for some time as well. But this was the beginning of something else. In the summer of 1609, Galileo, Harriot,
and others, turned the new Dutch invention - the "spyglass" - toward the night sky. The telescope was born.
This tale grew old, but our fascination
with telescopes has not. Following text is an attempt to give more
of an insight into their inner workings. More specifically, how do they
form images and what
factors determine their quality. Somewhat unusual, the main aspect is
that of the optical wavefront, as opposed to the geometric (ray)
"interface". That deliberate choice, while perhaps somewhat less
convenient, allows for more accurate qualitative assessment, and should throw more light at the underlying physical
fundamentals. Main reference sources are as follows:
(1) Astronomical Optics, Daniel J. Schroeder, (2) Aberration Theory Made
Simple, Virendra N. Mahajan, (3) Optical Imaging and Aberrations
I and II, Virendra N. Mahajan, (4) Optics, Eugene Hecht, and (5) Telescope Optics,
Harrie Rutten and Martin van
Venrooij.
Most of raytracing plots and routine checkups are by
ATMOS, Massimo Riccardi,
and
OSLO,
Sinclair Optics. Most of diffraction patterns were generated by
Aberrator, Cor Berrevoets.
For additional reading, see extensive
coverage of telescope optics and related subjects at Bruce MacEvoy's
Astronomical optics
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