OBSERVING SATURN WITH THE ALPO OBSERVING SATURN WITH THE ALPO - - PowerPoint PPT Presentation

OBSERVING SATURN WITH THE ALPO OBSERVING SATURN WITH THE ALPO OBSERVING SATURN WITH THE ALPO OBSERVING SATURN WITH THE ALPO

Julius L. Benton, Jr. Coordinator ALPO Saturn Section

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• Guiding Principle of the ALPO

Guiding Principle of the ALPO Guiding Principle of the ALPO Guiding Principle of the ALPO

Encourage and coordinate regular, systematic investigations of our solar system with instrumentation readily available to amateur astronomers.

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INTRODUCTION INTRODUCTION INTRODUCTION INTRODUCTION

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Value of Amateur Planetary Observations Value of Amateur Planetary Observations Value of Amateur Planetary Observations Value of Amateur Planetary Observations

• Freedom to observe at leisure for extended periods of time.
• Systematic observations provide long-term records for further

study by professional astronomers.

• Observations of changing atmospheric features on Saturn are

used to alert professionals in selecting targets for high- resolution spacecraft imaging.

• Skilled observers routinely produce excellent digital images at

different wavelengths that are useful to professional astronomers.

• Amateurs have actively participated in the Cassini mission.

• Some Achievements by Amateur Observers

Some Achievements by Amateur Observers Some Achievements by Amateur Observers Some Achievements by Amateur Observers

• Long-term visual work confirmed that distinct belts and zones are

not just occasionally seen on Saturn’s globe.

• Cassini's and Encke's divisions are not the only “gaps” in the rings

(ripples or “intensity minima” were routinely seen prior to Voyager).

• Ring C can be seen and imaged with small-to-moderate apertures.
• Long-term studies show a recurring pattern for atmospheric storms.
• CM data reveal variations in rotation rates for the SEB and NEB.
• Intensity estimates of belts and zones show a subtle seasonal effect.
• The tenuous Ring E external to Ring A was seen prior to Voyager.
• Dusky radial "spokes" were reported in Ring B prior to Voyager.
• The bicolored aspect of the rings and brightness asymmetries around

Ring A have been seen visually and successfully imaged.

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Suggested Suggested Suggested Suggested Equipment for Equipment for Equipment for Equipment for Observing Saturn Observing Saturn Observing Saturn Observing Saturn

• Minimum aperture recommendations:

10.2 cm ( 4.0 in ) for refractors. 15.2 cm (6.0 in) for Newtonians and Catadioptrics.

• Equatorial mount with slow-motion controls and a clock-drive.
• Color filters of known wavelength transmission.
• A printed or on-line ephemeris (e.g., Astronomical Almanac,

WinJupos, WIMP).

• Digital imager and a laptop with software to process images.

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• Saturn apparitions last about 378 days between conjunctions.

Plan your observations well ahead of the observing season. Start observing early when Saturn is just visible before sunrise. Continue monitoring Saturn through opposition to conjunction. Keep accurate records (e.g. date & time, location, telescope, magnifications, filters, etc.).

• Use standard observing forms for reporting data (available on

ALPO Website).

• Submit all observations on a regular basis via e-mail or s-mail).
• Strive for simultaneous observations (i.e., two or more
• bservers viewing at the same time on the same date).

Some Keys Some Keys Some Keys Some Keys to Meaningful Results to Meaningful Results to Meaningful Results to Meaningful Results

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ALPO Saturn Observing Programs ALPO Saturn Observing Programs ALPO Saturn Observing Programs ALPO Saturn Observing Programs

• Visual numerical relative intensity estimates.
• Full-disc drawings of Saturn using ALPO observing blanks.
• Regular digital imaging of Saturn at various wavelengths.
• Central meridian (CM) transit timings of features on the globe.
• Visual estimates and measurements of belt and zone latitudes.
• Visual monitoring and imaging of "intensity minima“ in the rings.
• Studies of the bicolored aspect and brightness asymmetries around

the circumference of Ring A.

• Accurate timing and imaging of stellar occultations by Saturn.
• Specialized studies at small or edgewise ring inclinations (e.g.,

transits of satellites and their shadows across the globe).

• Visual observations and magnitude estimates of Saturn’s satellites.

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Sample ALPO Sample ALPO Sample ALPO Sample ALPO Saturn Drawing Saturn Drawing Saturn Drawing Saturn Drawing Blank Blank Blank Blank

Although regular digital imaging of Saturn is very important, observers should not neglect to make routine visual numerical relative intensity estimates

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globe and ring features.

• Saturn’s Changing Ring Tilt Since 2009

Saturn’s Changing Ring Tilt Since 2009 Saturn’s Changing Ring Tilt Since 2009 Saturn’s Changing Ring Tilt Since 2009

• Saturn’s rings attain a maximum tilt of +27o toward Earth in October 2017.
• Summer solstice is approaching in Saturn’s Northern Hemisphere.
• Next edgewise ring presentations occur in 2025 (unfavorable) and 2039.

• Standard Nomenclature for Saturn

Standard Nomenclature for Saturn Standard Nomenclature for Saturn Standard Nomenclature for Saturn

• Conjunction

2014 Nov 18d UT

• Opposition

2015 May 23d

• Conjunction

2015 Nov 30d

Opposition Data

Equatorial Diameter Globe 18.5″ Polar Diameter Globe 16.5″ Major Axis of Rings 41.9″ Minor Axis of Rings 17.2″ Visual Magnitude (mv) +0.0mv B = +24.2o Declination −18.3o

Geocentric Phenomena for 2014 Geocentric Phenomena for 2014 Geocentric Phenomena for 2014 Geocentric Phenomena for 2014-

• 15 Apparition

15 Apparition 15 Apparition 15 Apparition

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SOME INTERESTING PAST SOME INTERESTING PAST SOME INTERESTING PAST SOME INTERESTING PAST AND AND AND AND RECENT OBSERVATIONS RECENT OBSERVATIONS RECENT OBSERVATIONS RECENT OBSERVATIONS

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• First imaged by Cassini at 23:26UT on December 5, 2010 at 35°N

Saturnigraphic latitude.

• By late February 2011 the massive storm widened by 15,000km

encircling the globe between Saturnigraphic latitude 35°N and 40°N.

• White spots arise as columns of material break through the upper

NH4-ice cloud deck and spread out.

• The NTrZ storm illustrates how shifting seasons and insolation can

help stir up weather on Saturn.

Images courtesy of NASA‘s Cassini Mission

The Memorable Great White Storm of 2010 The Memorable Great White Storm of 2010 The Memorable Great White Storm of 2010 The Memorable Great White Storm of 2010-

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11 11 11

• The Memorable Great White Storm of 2010

The Memorable Great White Storm of 2010 The Memorable Great White Storm of 2010 The Memorable Great White Storm of 2010-

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11 11 11

• ALPO Saturn Section received an appeal from Cassini scientists to

provide as many images of the NTrZ white spot as possible.

• Amateurs responded as early as December 10, 2010 and Pro-Am

cooperation continued during the 2010-11 apparition and beyond.

S E W N (IAU)

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Lingering NTrZ Storm Remnants in 2012 & 2013 Lingering NTrZ Storm Remnants in 2012 & 2013 Lingering NTrZ Storm Remnants in 2012 & 2013 Lingering NTrZ Storm Remnants in 2012 & 2013

• Between Saturnigraphic latitude 40oN and 45oN the globe remained

morphologically complex and brighter than usual following the storm.

2012 2012 2012 2012 2013 2013 2013 2013

S E W N (IAU)

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SATURN OBSERVATIONS DURING SATURN OBSERVATIONS DURING SATURN OBSERVATIONS DURING SATURN OBSERVATIONS DURING THE CURRENT 2014 THE CURRENT 2014 THE CURRENT 2014 THE CURRENT 2014-

• 15 APPARITION

15 APPARITION 15 APPARITION 15 APPARITION

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Pre Pre Pre Pre-

• Opposition Views of Saturn in 2014

Opposition Views of Saturn in 2014 Opposition Views of Saturn in 2014 Opposition Views of Saturn in 2014-

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15 15 15

S E W N (IAU)

Shadow of the Globe on the Rings is toward the East (IAU) prior to Opposition

NNNTeZ Dark Oval NTrZ White Spot North Polar Hexigon NNNTeZ Dark Oval

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Pre Pre Pre Pre-

• Opposition Views of Saturn in 2014

Opposition Views of Saturn in 2014 Opposition Views of Saturn in 2014 Opposition Views of Saturn in 2014-

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15 15 15

S E W N (IAU)

Shadow of the Globe on the Rings is toward the East (IAU) prior to Opposition

Bright area in EZn Elongated EZn White area

• Saturn at Opposition in 2014

Saturn at Opposition in 2014 Saturn at Opposition in 2014 Saturn at Opposition in 2014-

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15 15 15

S E W N (IAU)

• The Seeliger Opposition Effect is an apparent brightening of the rings

for a short interval near opposition.

• Caused by coherent back-scattering of µ-sized icy particles in the rings

when the phase angle between Sun-Saturn-Earth is <0.3° .

2014 2014 2014 2014-

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15 15 15 Opposition Data Opposition Data Opposition Data Opposition Data: : : : 2015 May 23d UT Eq Dia Globe = 18.5” Po Dia Globe = 16.5” Maj Axis Rings = 41.9” Min Axis Rings = 17.2” Visual Mag = 0.0 B = +24.2o Declination = −18.3o

• Changing Position of the Shadow of the Globe

Changing Position of the Shadow of the Globe Changing Position of the Shadow of the Globe Changing Position of the Shadow of the Globe

• n the Rings Before and After Opposition
• n the Rings Before and After Opposition
• n the Rings Before and After Opposition
• n the Rings Before and After Opposition

S E W N (IAU)

Sh G on R Prior to Opposition Prior to Opposition Prior to Opposition Prior to Opposition: : : : Sh Sh Sh Sh G on R is to the IAU East G on R is to the IAU East G on R is to the IAU East G on R is to the IAU East At Opposition At Opposition At Opposition At Opposition: : : : Sh Sh Sh Sh G on R is behind Globe G on R is behind Globe G on R is behind Globe G on R is behind Globe After Opposition After Opposition After Opposition After Opposition: : : : Sh Sh Sh Sh G on R is to the IAU West G on R is to the IAU West G on R is to the IAU West G on R is to the IAU West Sh G on R

Images courtesy of Christopher Go of Cebu City, Philippines

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Post Post Post-

• Opposition Views of Saturn in 2014

Opposition Views of Saturn in 2014 Opposition Views of Saturn in 2014 Opposition Views of Saturn in 2014-

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15 15 15

S E W N (IAU)

Shadow of the Globe on the Rings is toward the West (IAU) after to Opposition

NNNTeZ Dark Oval Multiple small NTrZ White Spots

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Post Post Post Post-

• Opposition Views of Saturn in 2014

Opposition Views of Saturn in 2014 Opposition Views of Saturn in 2014 Opposition Views of Saturn in 2014-

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15 15 15

S E W N (IAU)

Shadow of the Globe on the Rings is toward the West (IAU) after to Opposition

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Highlights of the 2014 Highlights of the 2014 Highlights of the 2014 Highlights of the 2014-

• 15 Apparition (So Far)

15 Apparition (So Far) 15 Apparition (So Far) 15 Apparition (So Far)

• The rings are inclined by +24o in 2014-15, so near-optimum views are

possible of Saturn’s Northern Hemisphere and North face of the rings.

• Numerous “intensity minima” have been seen and imaged in Ring B.
• The Pro-Am effort that began back in 2004 when Cassini started

monitoring Saturn at close range is still active in 2014-15.

• Observers are reporting discrete features within the belts and zones:

Recurring dark spots have been imaged at +41o and +64o Saturnigraphic latitude that seem to be increasing in complexity (especially the one at +64o). A recurring bright feature in the EZn has been imaged since about June 20th. Based on intensity estimates, the EZn is slightly brighter than usual. Multiple small bright spots have been imaged in the NTrZ (possible remnants of the 2010-11 storm?).

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)01.2.3

• Saturn and How to Observe It

is a comprehensive guide to ALPO Saturn observing programs and techniques. A fully revised edition is expected to be published by mid-2016.

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