Saturn’s Cassini Division

Saturn's Rings
Saturn’s Cassini Division
Observation Data

Location: Atlanta, GA (33.7384° N, 84.4234° W)

Date and Time: 2023-09-18, 22:20 – 22:57 EDT

Sky conditions: Seeing – Good, Transparency – Mag 3

Instrument: Celestron C8 SCT @f/20, Aperture 203.3mm, Focal length: 2023

Mount: Advanced VX

Eyepiece: N/A (Imaging)

Reticle Device: N/A

Imaging Equipment: ZWO ASI 120MM-S, 2x Barlow, ZWO filter wheel, Astronomik ProPlanet 642 BP IR-pass filter

Image type and sensor: CMOS, AR0130CS 1/3″ sensor 

Image capture details: IR: Start capture: 22:49, End capture: 22:51, Exposure: 83.624ms, Gain: 70, best 20% stacked of 1436 frames. Software: ASICap, ASIVideoStack, Photoshop

Project Objectives

Within the three major rings that can be seen through the amateur telescope is the prominent gap known as the Cassini Division. It separates the “B” Ring, the brightest ring, from the “A” Ring and appears as a fine black line circling the planet. It is most easily seen on the two protrusions of the rings on either side of the planet known as ansae.

The axial tilt of Saturn and the inclination of Saturn’s orbit compared with the Earth’s, combine to cause the plane of Saturn’s rings to change their tilt. About every 7.25 years the rings go from edge-on to fully open. Your ability to see the Cassini Division will vary depending on how “open” or “edge-on” the rings are. Seeing and aperture size will also affect your ability.

Describe your view of the Cassini Division. Can you see it? Can you barely see it or does it “jump out at you”? How complete a circle of the rings can you detect? Include observation data and impressions.

Impressions

I have a decent view of the Cassini Division on the ansae. I can see that there is a darker division between the B and A rings, but it appears to gradually disappear. Saturn’s rings will be edge-on in March 2025, so the “gap” is closing, and we won’t be able to see the rings fully open until around 2031.

Saturn’s Disk Markings

Saturn’s disk markings
Observation Data

Location: Atlanta, GA (33.7384° N, 84.4234° W)

Date and Time: 2023-09-18, 22:20 – 22:57 EDT

Sky conditions: Seeing – Good, Transparency – Mag 3

Instrument: Celestron C8 SCT @f/20, Aperture 203.3mm, Focal length: 2023

Mount: Advanced VX

Eyepiece: N/A (Imaging)

Reticle Device: N/A

Imaging Equipment: ZWO ASI 120MM-S, 2x Barlow, ZWO filter wheel, Astronomik ProPlanet 642 BP IR-pass filter

Image type and sensor: CMOS, AR0130CS 1/3″ sensor 

Image capture details: IR: Start capture: 22:49, End capture: 22:51, Exposure: 83.624ms, Gain: 70, best 20% stacked of 1436 frames. Software: ASICap, ASIVideoStack

Project Objectives

At first glance, the face of Saturn’s disk seems rather boring, a bland creamy-yellow ball. Less than half the apparent diameter of Jupiter with proportionately duller markings, Saturn requires diligent study and a tranquil night of seeing. The greater your observing skill or equipment, the more subtle the details you will see.

You should be able to tell that one hemisphere is decidedly darker than the other. Can you determine which one? Belts, zones, and spots can sometimes be glimpsed through the planet’s top layer of obscuring haze. They are subtle. What do you see? Include observation data and impressions.

Impressions

I used a 642 BP IR filter to help bring out some surface details and improve seeing. The darker hemisphere is currently the southern hemisphere. In the northern hemisphere, the belts appear darker in color and the zones are lighter in color. The C Ring can be seen obscuring the disk around the Equatorial Zone. I could not make out any subtler details on the disk.

Saturn’s Rings

Saturn's at opposition
Saturn’s opposition – Seeliger Effect. North is up, East is left
Observation Data

Location: Atlanta, GA (33.7384° N, 84.4234° W)

Date and Time: 2023-08-26, 00:05 – 00:49 EDT

Sky conditions: Seeing – Good, Transparency – Mag 4

Instrument: Celestron C8 SCT @f/20, Aperture 203.3mm, Focal length: 2023

Mount: Advanced VX

Eyepiece: N/A (Imaging)

Reticle Device: N/A

Imaging Equipment: ZWO ASI 224MC, 2x Barlow, ADC, UV/IR Cut filter

Image type and sensor: CMOS, IMX224 1/3″ sensor

Image capture details: Start capture: 00:46 EDT, End capture: 00:49 EDT, Exposure: 100ms, Gain: 347, best 20% stacked of 1931 frames Software: ASICap, ASIVideoStack, Photoshop

Project Objectives

Saturn is the most impressive object in the solar system and surely one of the most beautiful. Saturn is the only ringed planet whose rings are visible in the amateur’s telescope. On a clear steady night, nothing rivals the sharp divisions and contrast seen in Saturn’s ring system.

Make a sketch or image of what you see. Place an arrow on your drawing (or image) to indicate the direction of drift when your scope is not tracking. Include observation data and impressions.

Impressions

Something really neat happens when you observe Saturn near opposition, the Seeliger Effect.

The Seeliger Effect, also known as opposition surge, is a phenomenon observed in astronomy when a celestial body, such as a planet or moon, appears significantly brighter when it is directly opposite the Sun in the sky. This alignment enhances the backscattering of sunlight, causing an increase in brightness. During opposition, the Earth is situated between the Sun and the celestial body, creating optimal conditions for this effect. The surge is particularly noticeable in planetary observations, leading to a momentary increase in brightness and a reduction in shadows on the surface. This phenomenon can be seen in my image above, taking note that the rings are brighter, and the planet’s shadow cannot be seen on the rings.