Transit Observing primer
What is it that one will need, in order to be able to make the best of this event? Whatever be the level of equipment that is possible for any one of us, there will be possibilities of participating in observing the event.
Simple handmade equipment and binoculars Telescope with projection apparatus
Telescope, solar filters and tracking Possible observations
Handmade projection equipment if you own simple field binoculars
Start with the simplest possibility - if we do not have access to any sophisticated equipment - can we see the Transit with a simple pinhole camera projector that is usually used for observing eclipses?
In principal, yes. The problem is that of details - how satisfied will one be with what can be seen with a simple pinhole camera projection - long box type of a projection to get the maximum possible contrast and image size. How much of the details will be possible to see with such a simple equipment - not any of the details really - the only question that will need to be answered on the 8th of June 2004, is whether Venus on the disk of the Sun, is at all visible to one through such a pinhole projection apparatus.
To avoid disappointment, we may plan for two different purposes to be served by the long box projection apparatus that we are making.
First
we make a simple pinhole camera projection apparatus that we can test on the 8th
–use the same projection apparatus, in conjunction with simple field
binoculars – this will definitely give us good views of Venus moving across
the disk of the Sun – as well as views of any possible sunspots that maybe
visible on the Sun’s disk on the day of the transit.
What
do we have to do to make this projection apparatus? We need a long rectangular
box – about 4-6 feet in length and about 1 ft
by 1 ft in cross section. The longer length of 6 ft is required for
simple projection, while a length of 4 ft
will suffice for binocular projection. Make a plywood rectangular box
(firm thick cardboard will also serve the purpose for short term usage) –
blacken the inside of the box for better contrast and visibility.
Cover
one end of the box with sunpak sheet or any other material that allows you to
cut small holes in it and insert the eyepiece end of binoculars or a small
telescope. The other end should have a white blank sheet of paper placed on the
inside to serve as the screen. (Graph paper for some of the observations)
On
the sunpak end of the long box – make one small hole with a thin nail to serve
as the pin hole. Look at the projection of the Sun, on the other end of the box,
with this pinhole and note its size.
Next
to this pinhole make two small holes, just a little smaller than the diameter of
the eyepiece holder of your binoculars – If you are using a small telescope
then make one single hole to fit its eyepiece holder. Insert the Binocular or
telescope eyepiece in these holes and try pointing the box towards the Sun and
obtain a projected image on the screen side of the box. This will need a bit of
a practice with pointing the box towards the Sun and the dealing with the
required focusing, while the eyepiece holders are fitted inside the sunpak
material – but, it can be done and soon one will get a good feel for doing the
adjustments and obtaining a projected image of the Sun.
Binoculars, rectangular box and the sunpak sheet cover
Never ever try looking at the Sun directly – pointing at the Sun, for the box, can be done by looking at its shadow and trying to minimize it. One other precaution needed here is that the binoculars that is being used should not have any plastic or vinyl parts which may melt due to the intense heat generated by pointing the binoculars at the Sun.
View of the projected image of the Sun inside the box.
Practice this with viewing the Sun for sunspots well before the actual event. One thing one will notice is that it is difficult to hold the box steadily, so that an undisturbed image can be seen. One way of achieving stability of the projected image, is to keep this box, in a larger container, fill some amount of sand at the bottom and work this sand around the projection box – pack it around the box, once it is in a position to view the Sun. It is amazing the stability that can be achieved with this simple technique. Alternatively, if you have binoculars with a stand, then one only needs to project an image of the Sun on a screen using the binoculars and just ensure that the screen is in shadow other than the projected image. Most binoculars owners in India, do not usually have a tripod stand to go with them, in which case the box projection method and sandbox, could be used very easily to obtain good views of the Sun, and most definitely be able to view Venus crossing the disk of the Sun as well as see many of the details of the event.
Telescope with projection apparatus Telescope, solar filters and tracking