Flat computer screen as light box?

[michaelmorris]

I've heard of people using an TFT flat computer monitor as a light box for taking flats. I can pick one up for as little as £25 at my local computer fair. Has anyone here used one? Do they work okay for taking flats?

[Milamber]

What is wrong with a t shirt? Don't they work any more?

[brianb]

What is wrong with a t shirt? Don't they work any more?

He hasn't got a clean one

Yes I have used the computer screen dodge. Just open an empty window & maximise it, focus the camera on infinity, get real close to the screen, keep the camera lens front parallel with the screen surface, work with the room darkened so there are no reflections / other significant light sources. Results are OK for normal/tele lenses. The results are not so good with wide angle lenses where small variations in the light output at different viewing angles makes the flats "overcompensated" for fall off towards the corners.

[Tim]

If you are going to do that Michael, why not just have a white board on the fence with a flourescent tube lighting it? I wouldn't fancy bringing a monitor out every time and plugging in etc.

I've tried a few methods, not a screen though, and the best results have come from sky flats with a white T shirt. I do them either at twilight or dawn, or sometimes both. If you have a camera that is prone to dust motes (eg QHY8) then they are essential.

[michaelmorris]

If you are going to do that Michael, why not just have a white board on the fence with a flourescent tube lighting it? I wouldn't fancy bringing a monitor out every time and plugging in etc..

I have an observatory so there wouldn't be any hauling anything out. I don't have a fence I can point the scope at. If I have a white board in the observatory, I've got to illuminate it evenly - hence the monitor idea.

... best results have come from sky flats with a white T shirt. I do them either at twilight or dawn, or sometimes both.

I'm rarely observing/imaging at dusk or dawn, hence the light box idea.

[SteveL]

How about making your own from an EL sheet, which will give a nice flat illumination. Stuck bretween two bits of perspex, with another layer of perspex polar frost to diffuse it even further (and prevent reflections back from objectives bouncing back off the shiney smooth perspex).

EL Panels