The A.L.P.O. Saturn Section
Secondary in size only to Jupiter, the planet Saturn lies at
a mean distance from the Sun of some 9.5 AU
(astronomical units). Considered only as a globe, the
planet is a somewhat smaller, dimmer, and relatively
quiescent replica of the giant Jupiter. With its majestic and
symmetrical ring system, together with the brighter eight
satellites accessible to moderate-size telescopes, Saturn
emerges as an object of exquisite and unsurpassed
beauty, holding a particular magnetism for the visual and
photographic observer alike. Besides its aesthetic
qualities, Saturn exhibits numerous features requiring
persistent and meticulous observation. At opposition, the
globe of Saturn subtends an angle of about 17" (seconds
of arc) in equatorial diameter, while the ring system's
major axis spans nearly 42". Those experienced at
observing Jupiter will note that Saturn requires almost
twice the magnification needed for the Giant Planet so that
a disc of comparable proportions is produced. In addition,
those with relatively small telescopes will frequently find
that Saturn is relatively barren and changeless, seldom
displaying the wealth of activity that is so common on
It is quite hazardous to try to establish some inflexible
minimum with respect to aperture, particularly when it is
recalled that extraordinary results have been obtained in
past years by experienced observers using extremely
small instruments. Almost any optical assistance will show
Saturn's spectacular ring system, and the major disc
features are revealed with a 7.5cm. (3.0in.) refractor,
including perhaps a major belt and a zone or two near the
equator of the planet. Cassini's Division should also be
visible in the rings with such an instrument. Moving up to a
10.2cm. (4.0in.) refractor or a 15.2cm. (6.0in.) reflector,
the observer will discover that he has found about the
minimum aperture that will prove to be suitable for routine
and beginning detailed studies of Saturn. Of course, when
seeing and transparency conditions allow, the larger the
aperture, the bigger will be the image scale and the
greater the resolution and image brightness. Experienced
observers have found that a 15.2cm. (6.0in.) refractor or a
25.4cm. (10.0in.) reflector is an ideal instrument for
observing Saturn. More important than instrument design
is optical and mechanical quality, and the prospective
Saturn observer should obtain the best telescope he can
afford. Excellent optics and a stable mounting are of far
greater importance that sophistication of electronics in the
mounting or exotic substrates or coatings for the lenses or
mirrors. Some observers in recent years, for example,
have successfully used simple, but premium-quality,
Dobsonian reflectors when observing Saturn. The novice
should spend some time in experimental work with the
telescope he intends to use for following Saturn, seeking
to establish the best combination of magnification, filters,
and image size, brightness, and contrast. These topics,
and many others, are discussed in considerable detail in
The Saturn Handbook. After a bit of experience in
observing Saturn, individuals will want to become familiar
with the more advanced methods and techniques
described in that book.
Like Jupiter, Saturn displays in an appropriate telescope a
series of bright zones and darker belts that run roughly
parallel to the equator. Much of the fundamental
nomenclature assigned to the specific zones and belts of
Jupiter applies to Saturn. The Saturn Handbook gives more
detail on the specialized uses of all of the terminology
and nomenclature for Saturn.
Observations of the Saturn's globe, rings, and satellites
are organized into the following routine programs:
1. Visual numerical relative intensity estimates of belts,
zones, and ring components.
2. Full-disc drawings and sectional sketches of global and
ring phenomena (the Saturn Section furnishes templates
with the correct global oblateness and ring geometry to
facilitate drawing). All drawings submitted for publication
must be originals, not xerox copies.
3. Central meridian (CM) transit timings of details in belts
and zones on the globe of Saturn (utilized to deterimine or
confirm rotation rates in various latitudes).
4. Latitude estimates or filar micrometer measurements of
belts and zones on the globe of Saturn.
5. Colorimetry and absolute color estimates of globe and
6. Observation of "intensity minima" in the rings (in
addition to observations of Cassini's and Encke's
7. Observational monitoring of the bicolored aspect of the
rings of Saturn.
8. Observations of stellar occultations by Saturn's rings.
9. Specialized observations of Saturn during edgewise ring
presentations in addition to routine studies.
10. Visual observations and magnitude estimates of the
satellites of Saturn.
11. Routine photography, CCD imaging, photoelectric
photometry, and videography of Saturn and its ring
12. Simultaneous observations of Saturn.
Individuals interested in participating in the A.L.P.O.
Saturn programs should contact:
Julius L. Benton, Jr.
Associates in Astronomy
P.O. Box 30545
Savannah, GA 31410