Many observers wishing to do astrophotography often ask. Can I do
astrophotography without a telescope using simply a standard 50mm lens
and camera.
The answer is yes you can.
Using an S.L.R. camera and a standard 50mm lens with a manual "B"
setting one can open the shutter for a maximum of 15 seconds near
the Celestial equator and 20 seconds close to the pole (+90 -90)
before stars start to trail on the film. This is an effect caused
from the rotation of the Earth, the diurnal motion. The area of sky
recorded on a 35mm film frame is 28deg by 42deg which is some 1000 square
degrees of sky. Ideal for constellation photography,
See Cassiopeia.
If the maximum aperture of the lens is say F1.8 or F2
it is always best to close down one stop to say F2.8 or the stars on
the edges of the field recorded will be faint from vignetting and
blurred. Also the camera should be mounted on a very firm tripod
and a cable release must be used. Holding the shutter mechanism
down for many seconds with a finger causes unwanted contact so more
chance of camera shake etc.
Also wind can be troublesome so avoid this at all times. If you
live in a city avoid pointing the camera in the direction of street
lights or your films will become fogged and blurred from the light
pollution emitted from Mercury and sodium lighting. For best
results go to a darker site away from the city lights. You will be
amazed how much more you will record on your photographs.
Fast films such as 400asa or better still the 3200 T-Max black and
white films are ideal and one can reach magnitudes of the order of 9
mpg on nights of good transparency and with no Moon above the
horizon.
Colour slide film such as the Agfa 1000 are also ideal and these
will record the colours of the stars well.
A project of which any person could do is to produce and make their
own finder charts for locating the stars and many deep sky objects.
Also a more serious aspect of this type of astrophotography is the
search for new stars or Novae. You could photograph many areas of
sky on a regular basis and compare your latest negatives with the
previous ones taken. On the other hand one could monitor the rise
and fall in brightness of many variable stars. One such example is
the variable star "R" Corona Borealis.
Also Aurora and meteors (shooting stars) can be recorded on film in
less than 10 second exposures, and the brighter comets in 25 second
exposures.
All negatives can be mounted as slides so that they can be shown at
your local astronomical society meetings or to your friends.
January 1999
By John Fletcher. Mount Tuffley Observatory. UK (C)