The following presentations which range in size from 20 to 70 slides are available free of charge on application. File sizes range from 400kb to 1mb. It is a condition of supply that:

1. The presentation not be used for direct commercial purposes,

These presentations are being supplied on trust. Please consider this in your use of this material.

When Emailing your request, please state:

a. Your name and postal address,

b. Your intended use of the powerpoints.

c. Which Powerpoints you require.

The information that is supplied will only be used for my records. - I may contact you if I develop a similar Powerpoint or update the original.

February 2002.

For years I have been fascinated by the concept of using projected transparencies to show motion involving astronomical objects on the screen in a much more controlled way and in much greater detail than motion picture or video. For example the sudden appearance of a supernova or the progression of the moon from a crescent through to full can be easily demonstrated. Ordinary slide projectors have a delay and certain amount of 'jittering' between images. On the other hand Dr. Bryan Bridge made a beautiful cross fader for two projectors for the Astronomical Association of Queensland and this worked very nicely, but it needed a certain amount of set up time, careful alignment, and precisely aligned slides for this purpose.

Enter the computer age and 'Powerpoint'. With this program, apart from a host of other features including graphics and sound, it is possible to provide these shows via the computer projectors that are becoming so popular, though they are still rather expensive. Of course they can also be viewed using your home computer. Transmission by Email or computer disc is also easy. 'Powerpoint' has a further advantage, namely that the image can be enhanced using the computer, further text or diagrams can be added to the image, and explanatory text can easily be interspersed as separate slides between the images. The images can be quickly and easily altered. For superimposing slides, they no longer have to be on precisely the same position and orientation….or size. All three can be manipulated in the processing.

There are some other considerations. Since the individual slides that you wish to use to show motion are to be loaded by the computer before being displayed, you must be careful to minimise the size of each slide if you want to display them in a fast sequence. This will depend upon the speed of the computer, but I have found little problem with individual 'fast sequence' slides no larger than 30kb and up to double this size for others. The total size of my presentations range up to 1mb and you certainly need to watch the final size if you want to fit it on a floppy or readily transmit it by email. Whilst each presentation has a 'story', I have used the system many times to show motion -Pluto moving over several days, a supernova in a galaxy, the lunar phase growing, libration on the moon, Leonid meteors, being just a few.

When I started developing these presentations, I began to realise that other features could be utilised to help presentation. When showing images of comets, I place the head of each comet on the same spot on the screen for effect. I also use a drawing like a constellation outline to orient the viewer and this can be dropped off when the same slide is repeated but without the outline.

The system also allows you to be a little fanciful and correct images by computer photo processing much more easily than on film, for example by colouring up an overexposed double star image of the spectacular coloured double Beta Cygni. A faint moon of Saturn is barely visible - no problem - enhance it. You want a photo of Venus in the morning sky and all you have is one of Jupiter with a bright star nearby… No problem, expunge the star and brighten up Jupiter. You have two images of Jupiter. One has a grossly overexposed planetary disc and four galilean satellites. The other has a well exposed disc but no moons. Remove the disc from the first and replace it with the second…but one of the moons was close to the planet and now looks odd. Never matter, remove and replace it!

I needed to simulate a transit of Venus and first needed a solar disc. I coloured and contrasted up a washed out 'Transit of Mercury' image that had been projected on a card and removed Mercury. Then, using a 'paint' type program, I produced a slightly fuzzy black disc of the appropriate size to suffice for Venus. I developed the Transit of Venus Powerpoint this way repeating the same background but moving the disc of Venus by regular increments guided by a template which I had taped to my screen! I 'painted on' the special effects at the contacts.

In all 'Powerpoint' presents exciting possibilities, not the deadly dull office presentations which are the successor to the dreaded overheads. I have just started and have not explored all the possibilities. However you need a few things after you have chosen your subject:

(1) Firstly you will need a computer with disc drive, printer and at least a flat bed scanner.

(2) Develop a theme and decide what you wish to convey. (Make it simple and try to 'lighten' at least each second slide with an image.)

(3) Get permission to use photographs in view of the copyright laws. - (For myself I avoid this potential problem by using my own photographs.) As a general rule of thumb copyright of this type expires 50 years after publication. Some sources (like NASA) allow you to use their material with acknowledgment.

(4) When setting the display time for each slide, take account of slow readers and the subject, but 20 seconds is pretty long and the whole presentation should be under about five minutes.

(5) In view of (4), consider rewriting, editing, and simplifying, your text.

But, you ask, "Why do it?" I see it as offering exciting possibilities for both presentation of observations/ experiences and for education. It is something with more life than a photo album or a slide show where you may have forgotten some salient points. Once completed it remains and can be easily accessed or transmitted if needed. As an example of the educational application, a number of my presentations are in use at the Sir Thomas Brisbane Planetarium for patrons to watch whilst awaiting their show.

Regarding the 'Powerpoint' presentations referenced above, I find it more satisfactory to email a presentation because it will be stored using your own equipment and thus the possibility of misreading a disc produced by another machine is avoided.

Peter Anderson.