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We use LCD projectors for our Bishop Museum Starlab programs.  We set the LCD projector to its lowest brightness level and then generally use the projected images in a chunk either at the start or the end of a program, so that the star show part of the program can be presented without any visual distraction.

Downside of using these LCDs: the image is pretty bright, even at the lowest brightness setting, and the setup takes longer than just slapping in the ol' slide projector.  

The upside:  using an laptop and LCD is much quieter than using a slide projector.  It also allows you to use video clips, play CD walk-in music off the computer, update images very quickly etc.

Mike

Mike Shanahan
Education Director
Bishop Museum
1525 Bernice Street, Honolulu HI 98817
Office: (808) 847-8235
FAX: (808) 7-8250
Pager: (808) 361-7318
Cell: (808) 386-1419
www.bishopmuseum.org


-----Original Message-----
From: Informal Science Education Network [mailto:[log in to unmask]] On Behalf Of Glen Moore
Sent: Tuesday, November 02, 2004 8:44 AM
To: [log in to unmask]
Subject: Re: Using Data Projectors in Starlab

ISEN-ASTC-L is a service of the Association of Science-Technology Centers
Incorporated, a worldwide network of science museums and related institutions.
*****************************************************************************

Harry

The relationship is between lamp life and brightness setting will not be
linear. A reasonable reduction in brightness will increase life but the
(halogen) lamps may not like being constantly run too cool.

I am surprised that your projector doesn't adjust low enough in
brightness using the built in brightness controls. Perhaps a combination
of setting low brightness on the projector and some mechanical
brightness reduction will work for you. One option is to use some
neutral density material.  If it is a DLP then a simple piece of
Polaroid will give you a factor of 2. Putting a diaphragm in front of
the lens will give you adjustable control but will create some
vignetting. You may find this acceptable depending on the particular
projector - place the diaphragm as close to the lens as possible - try
it will various sized holes in cardboard diaphragms first.

While you are projecting a video image, is the appearance of the
starfield so important? Attention will be on the image. There is a trade
off when the projected image loses its impact in order to preserve the
starfield. Ideally it would great to have a bright image against a dark
starry background.  However the crosstalk effect, with a image lighting
up the rest of the dome, gets more noticeable as the dome size reduces.

Of course if you can brighten up the starfield this will help. That is
another issue.

Glen Moore
Science Centre and Planetarium
Wollongong


Harry White wrote:

>ISEN-ASTC-L is a service of the Association of Science-Technology Centers
>Incorporated, a worldwide network of science museums and related institutions.
>*****************************************************************************
>
>Does anyone out there use data projectors in their Starlabs ?
>
>If so, have you investigated de-rating the bulb at all ?
>
>The projectors are far too bright to go happily with the starfield projector
>and reducing the current should greatly increase the bulb life.
>
>I haven¹t tried it yet and I suspect some clever electronics will shut the
>projector down as soon as the current falls.
>
>Has anybody out there tried it  ?
>
>Thanks
>
>

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