beginners astronomy

BEGINNERS ASTRONOMY

Martin Crow Crayford Manor House Astronomical Society

Planetary observing and Imaging

Last time


Lunar observing using a telescope:

Using charts / maps of the Moon

Things to look out for

Grazing occultations

Drawing / sketching

Safe Solar observing using binoculars and a telescope:

Do’s and don’ts

Ways to observe safely

What to see in white light

Other ways to view the Sun

This week:


Observing the planets

Naked eye

Telescopically: Eye

Camera

Webcam

Observing the Planets


The ‘classical’ planets have been known since ancient times.

They were noted as different from other stars because they were not ‘fixed’and the Greeks called them ‘Asteres Planetai’ or wandering stars.

The ‘classical planets are: Mercury, Venus, Mars, Jupiter and Saturn although the Greeks would have included the Moon and Sun with these.

All of the classic planets can be viewed with the naked eye.

Naked eye



Why do we only see Mercury and Venus in the morning and evening twilight sky?

Venus can be seen in the day light sky when well placed.



Why when we observe the planets naked eye can we not see them as disks?

The unaided eye can generally only resolve about 3 arc minutes at best.

Celestial body Angular diameter

Sun 31.6′ – 32.7′

Moon 29.3′ – 34.1′

Venus 9.565″ – 66.012″

Jupiter 29.800″ – 50.115″

Saturn 14.991″ – 20.790″

Mars 3.492″ – 25.113″

Mercury 4.535″ – 13.019″

http://en.wikipedia.org/wiki/Sun

http://en.wikipedia.org/wiki/Moon

http://en.wikipedia.org/wiki/Venus

http://en.wikipedia.org/wiki/Jupiter

http://en.wikipedia.org/wiki/Saturn

http://en.wikipedia.org/wiki/Mars

http://en.wikipedia.org/wiki/Mercury_(planet)



What you will see will be very much determined by:

With a telescope

The seeing.

Magnification

The physical properties of the telescope



Seeing

The better the seeing the more detail you will see.

Good seeing is generally associated with misty foggy weather when the air is very still.

The higher the object is in the sky the better the seeing.

Seeing is often disturbed around trees and over buildings.

Observing planets is not so affected by light pollution.

With a telescope



With a telescope

Observing using a long focal length telescope will normally give best results.

Magnification – how to work it out.F f

Magnification = F divided by f

Example: F = 500 f = 10 500/10 = 50



Resolution.

The finest detail that a telescope can see is its angular resolution.It is equal to 1.22λ/D (radians).Where λ = wave length in meters.D = the diameter of the object glass / primary mirror in meters.What this says is that to see more detail you need a bigger diameter.

With a telescope

The physical properties of the telescope



With a telescope

Features on Jupiter's surface

Shadow transits and the motion of the Galilean moons

Phases of the inner planets Venus and Mercury and any visible surface detail.

Things to observe and do:

Keep notes / drawings in your observing log book

Observe Saturn's beautiful ring system and moons

Make use of tables and charts to aid and plan your observing



With a telescope



With a telescope and camera

The cameras automatic metering needs to be over ridden.

The ISO needs to be set to 100 or 200 – experiment. Note that thehigher the number the grainier the image will be i.e. less detail.

Exposures between 1/5 sec and 1/60 are normal.

If your camera has a histogram use it to help you get the best exposure.

How to:




Jupiter




Saturn




Image of Jupiter taken using film (1990).



With a telescope and webcam (Lucky dip imaging)

What you need:

A webcam with CCD sensor

Adapter and infrared blocking filter

A laptop and free software from the internet – Registax or Avistack.




How does it work?




Registax in action – hopefully!



Images by Simon Dawes




Any questions?

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