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"Philip Washington" <phwashington@xxxxxxxxxxx> wrote in message
news:pan.2005.06.25.05.16.40.20931@xxxxxxxxxxxxxx
>I am going to an observing area where other amateur astronomers may be
> i the vicinity. I use a laptop to control my CCD camera and telescope
> and
> was concerned about minimizing the light from laptop screen so I don't
> annoy other astronomers.
> I'm sure that other people have run into this situation at star parties
> and such and was wondering what is the best solution
> - keep the screen useful (viewable)
> - accessibility to the keyboard and mouse
> - prevent light leakage from disturbing other observers.
>
> I have heard of mounting red plexiglass over the monitor. Where is the
> best place to find this.
>
> I usually do use night vision red color schema on the computers, bu
> sometimes if a reboot is required it comes back with the standard color
> schema and therefore would like to avoid relying solely on this.
>
> Thanks in advance for any helpful suggestions.
There are actually two problems:
The first is the light as you 'look' at the laptop screen. Generally,
modern screens using EL backlights, only offer very limited 'diming' of
the display, so a filter is necessary. If you have a shop/business that
supplies 'stage lighting' equipment, there is a red film used for
floodlights. There are dozens (hundreds) of colours, but in the UK, the
deepest red film (used only normally for large stage lights, when doing
'dark' night scenes), is a good starting point. I use two layers of film.
I'd say that 90% of the films used are not actually dark enough. Most
stage films, have a significant 'yellow' component in their 'red' colours.
I used a layer of 'magenta', and 'primary red', which gives a very deep
red result (Lee 106, combined with Lee 113). 'Fire red', tends to be a
deeper red than the normal red tones, but in the Lee range, is too orange.
The second problem, is 'sidelight'. LCD's, let a lot of light out at
'shallow' angles close to the surface (try running your laptop in a dark
room, and look at the line of light along the top of the keyboard). This
leakage is worse in terms of other people's vision, that the light
directly 'through' the screen, and is not affected by dark colour schemes
on the screen itself. If you make the 'frame', that holds the film, stand
up like the edge of a tray, this will stop leakage here. There are also
systems sold for use on aircraft, as 'privacy screens', and these block
this light, and adding film to one of these would provide the structure
needed, and the blockage for this side light.
If you then use a really dark colour scheme (design your own, and set it
as the default colour scheme, in the daytime, then this will be the scheme
used when the laptop starts up), the result can work well. If you can even
faintly see the screen in a normal room, then it is too bright...
Best Wishes
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