With the widespread availability of computer video projectors, public presentation of astronomical images is easier than ever. However, these displays have limited dynamic range and are often set up poorly; often the contrast settings are excessive. This can have a severe impact on the appearance of astronomical images with faint details.
If you can access the video projector’s controls prior to your presentation, then try projecting a grayscale strip or at least an image with large dynamic range. A grayscale strip is available in the Help under Monitor Setup; various others are available on the Internet. Most importantly for astronomical images, adjust the contrast and brightness so that you can see the difference in shades of black at the dark end. Also try to make sure that you can discern brightness levels at the top end, to avoid excessively saturating bright parts of the images.
If you cannot adjust the projector prior to the show, then consider displaying the images using MaxIm DL. The Quick Stretch feature will allow you to quickly adjust the images for best display. If this is not possible because you are using PowerPoint, then it may be advisable to pre-adjust the images for lower contrast and brighter background, just to be sure the fainter details will be visible.
In the event that a video projector is not available, there are a number of options available for transferring images to slide film or overheads. However, most of these methods are expensive or have a long turn-around time. It is quite simple to photograph images directly from the screen, if due care is taken.
The Full Screen command on the View menu scales the selected image to fill the screen, and suppresses display of all other objects on the Windows desktop. For better results, you should first use the Process menu Resize command to scale the image to match the screen. This command interpolates the image, which will give a smoother representation.
The room lights should be off during the exposure. If your monitor has LED indicators, it is a good idea to temporarily cover them with two layers of black electrical tape.
Load a 35 mm SLR camera with ISO 100 slide film, and attach it to a tripod. Use a lens that allows you to fill the picture with the screen image (try to pick a lens which can be placed some distance from the screen - this will minimize geometric distortion). Align the camera square to the monitor and focus. Set the exposure to 1 second and the f/stop to approximately 4.5 (some bracketing may be required on your first attempt - be sure to record your settings). The long exposure will average out the effects of the monitor’s refresh scans.
The photograph will tend to increase contrast. To compensate for this, adjust the monitor controls so that the image looks washed out. This should be done in the dark so you can better see the image. By turning the contrast control down and increasing the brightness control, you can reduce the intensity of the bright areas while bringing the dark areas up (the background should look bright enough to the eye that the image is fairly washed out). The image will look terrible, but it will be just right for the camera. Again, some experimentation may be required for the best results.
When taking the picture, either use a cable release or the camera’s built-in timer to reduce any vibration.