Upload
mervyn-stone
View
213
Download
0
Tags:
Embed Size (px)
Citation preview
BEGINNERS ASTRONOMY
Martin Crow Crayford Manor House Astronomical Society
Observing Meteors and Variable Stars
Last time
Martin Crow Crayford Manor House Astronomical Society
Types of observation – visual and imaging
A bit about the Solar System and other things
About observation
This week: Practical visual observing
Martin Crow Crayford Manor House Astronomical Society
Meteor watch:
Visually observing variable stars
Visual observation
What are meteors
Imaging meteors
A look at setting up and using telescopes
Practical observing
Martin Crow Crayford Manor House Astronomical Society
Visual observations of variable stars
Naked eye is perfectly adequate for observing variable stars brighter than mag 4.
Martin Crow Crayford Manor House Astronomical Society
Martin Crow Crayford Manor House Astronomical Society
Martin Crow Crayford Manor House Astronomical Society
Practical observing
Martin Crow Crayford Manor House Astronomical Society
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
Martin Crow Crayford Manor House Astronomical Society
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
Martin Crow Crayford Manor House Astronomical Society
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
Martin Crow Crayford Manor House Astronomical Society
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
Martin Crow Crayford Manor House Astronomical Society
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
Martin Crow Crayford Manor House Astronomical Society
Observe the sky at about 50 deg in altitude and about 40 deg in azimuth away from the radiant.
Where to look
Practical observing
Martin Crow Crayford Manor House Astronomical Society
Stuff you’ll need
An accurate time piece
A dim red torch
Note pad / observing sheet and pens
Martin Crow Crayford Manor House Astronomical Society
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
Martin Crow Crayford Manor House Astronomical Society
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
Martin Crow Crayford Manor House Astronomical Society
Send your observations off to the Meteor section of the BAA.
Next
Practical observing
Martin Crow Crayford Manor House Astronomical Society
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
Martin Crow Crayford Manor House Astronomical Society
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
Martin Crow Crayford Manor House Astronomical Society