DIY Flat frame screen

[astrogardener]

Since moving up to a larger refractor the Gerd Newman screen I was using for flats with ED80 is now confined to the 'spares box'.

So what to do?

I looked around at ideas ranging from light boxes to T-shirts, but the laptop screen ideas got me thinking...

Here's a site that has the image of a laptop with a white screen:

http://blog.timesunion.com/opinion/files/2011/05/0518_WVquotation.jpg

When you're at the page, one click on the image makes it full screen.

Save it in images or somewhere then open in Windows pictures gallery, click on the '?' in top right corner and select luminosity levels (because it will be too bright). Change the levels for your required exposures for those perfect flat fields.

Save it and send to your desk top. Voila!

I've opened the image in MaximDL and checked the image for linearity, it's perfect

Cheer's, and happy snapping

[Kropster]

Useful website.

I have always wondered how good laptop screens are for taking flats?

How even is the illumination being as it is a series of fluorescent tubes, at least in older laptops.

Is there any way of testing any given screen and what could you use as a reference?

[IanL]

Slightly confused as to why you need to go to a web site to download an image of a white screen?  Why wouldn't you just open paint, resize the image to whatever resolution you need, fill the whole thing with whatever shade of grey you need to get the right ADU and then save it?

To test the flatness of a light source you take one flat, then rotate the light source through 90 degrees and take another.  Treat the first flat as if it was a light frame and flatten it using the second.  If your light source is truly a flat field then you will end up with a result that has no gradients.  Any residual gradient in the image would be the result of the light source not being perfectly flat.