martin crow crayford manor house astronomical society observing meteors and variable stars

BEGINNERS ASTRONOMY

Martin Crow Crayford Manor House Astronomical Society

Observing Meteors and Variable Stars

Last time


Types of observation – visual and imaging

A bit about the Solar System and other things

About observation

This week: Practical visual observing


Meteor watch:

Visually observing variable stars

Visual observation

What are meteors

Imaging meteors

A look at setting up and using telescopes

Practical observing


Visual observations of variable stars

Naked eye is perfectly adequate for observing variable stars brighter than mag 4.

Practical observing


The sight of ‘Shooting Stars’ is quite spectacular and ‘Fire Balls’ even more so.

Shooting stars are meteors.

Meteoroid: The current official definition of a meteoroid from the International Astronomical Union is "a solid object moving in interplanetary space, of a size considerably smaller than an asteroid and considerably larger than an atom".

Meteorite:A meteorite is a portion of a meteoroid or asteroid that survives its passage through the atmosphere and impact with the ground without being destroyed

The word Meteor comes from the Greek ‘meteōros’ meaning ‘high in the air’.

Practical observing


So what are meteors?

Grain sized particle entering the top of the atmosphere at high speed. Most Observed meteors are in the magnitude range of 1 to 4.

They can also be larger objects also entering at high speed. These are much brighter and are called ‘fire balls’ or ‘Bolides’ if above magnitude -5.

Re-entering rocket parts are also sometimes seen.

Practical observing


Meteor groups: Sporadics

Showers

Meteor showers are generally associated with periodic comets and are linked to known passes in the past.

The showers form as the Earth passes through the streams of particles left by the comet and so happen at certain times of the year.

The Perseid shower is associated with comet 109P Swift - Tuttle

The Leonids with 55P Tempel-Tuttle

The Geminids with the asteroid 3200 Phaethon

Practical observing


The shower meteors all appear to radiate from a single point in the sky.This is a perspective effect.

The constellation that contains these point give rise to the shower namei.e. the Perseid radiant is in the constellation Perseus

Practical observing


Meteor watch: Things to consider.

Ideally a dark site is needed away from interfering lights.

Haze and the Moon will also interfere.

It is better when the radiant is high.

Comfort is essential. A recliner and warm clothes, woolly hat and warm shoes.

Do it as part of a team if you can – it’s much more fun.

Practical observing


Observe the sky at about 50 deg in altitude and about 40 deg in azimuth away from the radiant.

Where to look

Practical observing


Stuff you’ll need

An accurate time piece

A dim red torch

Note pad / observing sheet and pens


Magnitude Object(s)

-4 Venus

-2 Jupiter

-1 Sirius

0 Capella, Rigel, Arcturus

+1 Regulus, Spica, Pollux

+2 Belt stars of Orion, Beta Aurigae, Gamma Geminorum,Pointers of Plough, Polaris, Denebola, Alphard

+3 Delta Ursae Majoris, Gamma and Delta Leonis, Epsilon Geminorum

+4 Eta Persei, Delta Aurigae, Rho Leonis

+5 Faintest meteors generally visible to naked eye

Practical observing


What to record

Time of the appearance (UT)

Magnitude estimate

Type: shower or sporadic

Constellation seen in

Presence and duration of any train if seen.

Any additional notes – colour, break up

Practical observing


Send your observations off to the Meteor section of the BAA.

Next

Practical observing


Imaging meteors

A DSLR camera is generally a better option although some ‘point and shoot’cameras are up to the job.

Generally use a wide field setting.

Set the ISO 800 or 1600 and low f number.

Exposure times 30 seconds to 120 seconds depending on light pollution.

Use a programmable timer to take the exposures.

Spare batteries or external power source very useful.

Focus is very important for sensitivity. Once focused disable the auto focus function.

Practical observing


Imaging meteors continued

Make sure that the camera date and clock is correct (UT)?

Also keep a visual watch

As a general rule of thumb only meteors brighter than zero magnitude will show up.

This apparent short coming can be put to good use.

It is very difficult to capture images of meteors

Observing as part of an organised team effort

martin crow crayford manor house astronomical society observing meteors and variable stars

Documents

practical observing

observation slide

phaethon slide

time martin

meteors imaging meteors

constellation perseus

shower meteors

observed meteors