Lightbox project

[Ivor]

I've decided to build myself a light box and there are many good examples on the internet. One of my key requirements is robust, portability and compact , as I don't expect to get a new telescope anytime soon I don't need it to exceed 150mm x 150 x ? to fit my FLT 110. I would like to keep the depth to a minimum and I like to be able to cover the diffuser to protect it.

From looking at all the designs out there one thing I'm not sure about, is why some solutions involve long boxes when others use flatter ones, is it irrelevant, something to do with the scope's focal length or the level of diffusion?

I like this approach http://www.astrosurf.com/comolli/flatfield2.htm,  I'd use a different material maybe a box like one of these http://www.maplin.co.uk/mb-plastic-boxes-1676 but I need to work out the required depth first?

Any ideas?

[JonH]

To defuse the light evenly I was told to rip apart an old LCD monitor and use the stuff out of one of those as there pretty much isn't anything better out there for the job!

[Ivor]

I've seen a project based around this approach however it goes away from my compact and robust requirement.

[JonH]

I've seen a project based around this approach however it goes away from my compact and robust requirement.

I don't think you quite got what i mean Ivor,
If you rip apart an old LCD or LED monitor (i just finished doing one) in order from front to back i had the glass front then the bit that produces the image then behind that i had two thin sheets of semi opaque plastic, the rest is going in the bin. Those think sheets are designed to disperse light evenly are no thicker than a few sheets of paper and can be cut to any shape or size you want.
They don't look like much but holding them up to a light it is easy to see how good they are.

I would guess some designs are longer than others to give the light the distance it needs to diffuse properly, but by using these fancy thin sheets would be able to make it almost totally flat.....

[Mike]

I would have thought that some thin sheets of white perspex would do the same job.

[JonH]

I dunno, held a bright LED torch right up to them but you can't see the sorce of the light at all just the whole sheet lit up.

[RobertM]

Ivor,

If you're interested I have a large number of white LEDs left from my Flat box project going free (same basic design).  I bought 100 for next to nothing from China so I've many more than I could possibly need for even a few more.  These are white LED's that I specifically chose to have as even a colour temperature as possible.  From memory I think they are 100mw.

PM me if you're interested.

Robert