MVNSC – Mississippi Valley Night Sky Conservation The Night Sky Around Us Lecture 3
Program developed by:
Mississippi Valley Conservation
Authority Royal Astronomical Society of Canada
Ottawa Astronomy Friends
Instructor: Pat Browne
Assistants: Shawn McKay
Course runs each Friday during the month of April Course time: 19:45 – 22:00 formally with priority given to observing when clear.
The Local Night Sky as it appears April 15 2016
Some reflections from last week …
Question: How do we describe the rotational motion of Earth’s moon?
Answer:Earth Moon Interaction: Rotational Period = Orbital Period
The moon turns on its axis in exactly the same time period that it takes to go around the earth, 27.3days. It rotates slowly 13 degs per day as well as orbits slowly at 13 deg/day so it keeps the same side always toward the earth (but not toward the sun). This synchronous rotation of the moon around the earth is the result of a tidal locking of the moon to the earth. Torques (twisting forces ) are applied to the moon which slow down the rotation and keep it aligned, pointing to the major axis of the earth-moon system.
Question: How do we know how to orient the lunar finder charts?
Configuration for Virtual Moon Atlas
- Refractor with 1 mirror on the prism holding the eyepiece E-W Flip>/li>Here’s how you rotate the image in Virtual Moon Atlas
- For binoculars – no rotation or flip
Question: What Jovian moons were visible in the eyepiece in our brief observing session last week (April 8 2016 around 9pm)
The Effect of Moonlight on viewing Deep Sky Objects or… (Where have all the Messier Objects Gone?)
If we go out and try to observe the objects circled in red, (our list of Messier Objects like M1 (in Taurus), M42 (in Orion), M44,(in Cancer) (M65, M66) in Leo), we will find them – barely – faint and low contrast … WHY…
Light from the Moon is so bright as to overwhelm the darkness needed to view deep sky objects. This effect is similar to light polluted skies. However even moonlight is eclipsed in an overly lit Night Sky!
Light from Artificial Sources
The challenge of LED lighting
With the evolution of energy-saving LED lighting, comes the challenge of choosing the healthiest type of light. Wattage efficiency of all LED lighting is about 30-50% higher than traditional technology such as incandescent bulbs and high pressure sodium (street lights)
With new LED outdoor lighting fixtures, there is a growing concern about the potential negative effects of blue-rich white light, even from fixtures with proper shielding. The case against blue light is well founded
with regard to discomfort glare, circadian rhythm disruption, light scattering, skyglow and biological systemdisruption in wildlife.
Outdoor lighting with high blue light content has a significantly higher intensity sky glow component than lighting with less blue light.
Lunar Observations and Science: Early Observations: Galileo Galilei – Italy 1610 – Lunar Features as Mountains and Craters measured from shadow lengths
“I feel quite sure that I first viewed the moon in my small scope with just as much incredible delight as Galileo did in his… No photograph has yet been made which is not cold and flat and dead when compared with the scenes that meet my eyes when the moon is viewed through even a small telescope” -Leslie Pelletier, Starlight Nights
Galileo observed that the line separating lunar day from night (the terminator) was smooth where it crossed the darker regions of the moon, but quite irregular where it crossed the brighter areas.
From this observation, he deduced that the darker regions are flat, low-lying areas, while the brighter regions are rough and covered with mountains Based on the distance of sunlit mountaintops from the terminator, he estimated that the lunar mountains were at least 6kms in height
(Note you may need to download it to play it).
Because of the view during the first quarter week (1/2 lit) we can see the light rays straight to the moon and perpendicular to us. : Measuring Mountain Heights – Galileo
The mountain peak is some small distance away from the terminator as shown in the illustration below (However it is placed on the other side of the terminator in this picture)
Note also that the diameter of the moon in terms of Earth radii was estimated during a lunar eclipse: … Based on a total eclipse of the Moon, the Greeks found that the Earth’s shadow in terms of the the Earth’s diameter is 3.5 Moon diameters.
So the lunar diameter was estimated at roughly ~ 12,756/3.5 ~ 3700 km courtesy http://www.nuffieldfoundation.org/practical-physics/diameter-moon
- explore and understand Lunar phenomena
- the Origin and Evolution of the Moon
- Interactions between the Earth and the Moon
- To further
See the videos from LRO here: Lunar Science – Millstone News Night Sky
Standard names for Phases of the Moon
To understand the lighting on the moon – try this:
Courtesy – Mary Lou Whitehorne – Astronomy Handbook For teachers (publ. RASC)
At Full Moon there are no Shadows to Observe
See: See Lunar Observing and the Isabel Williamson Lunar Guide (Millstone News article)
Here is a list of such objects, and we can check them with Virtual Moon software . This extract is from the WIlliamson Guide.
Make sure the feature is visible for the day of the lunar cycle.It’s good to pick three basic types of features to study:
- Mountains – Montes
- “Seas (basins)” – Maria
This image is taken from the Virtual Moon Atlas available for both windows and linux Virtual Moon Software
Tips to Getting your ‘bearings’ on the Moon:
Start at the terminator. This gives you a good sense of your x-axis.
- Locate a unique easy-to-identify feature like the Montes Apennines
- Then locate the craters you are supposed to study either North or South of there
- NOTE BENE: Find out what kind of image you are seeing:
- Reflector telescopes produce an image with South Up
- Refractor telescopes (if you are using an additional diagonal mirror) produce Left-Right reversed
- Binoculars produce the magnified image of the moon.
- For our first target, let’s pick Craters on the Terminator – Ptolamaeus for example . This one is given as an exercise in the MillstoneNews Night Sky section: Lunar Road Map – How to Observe…