Flats using laptop screen

[astropixel]

Posted here instead of gallery.

Not sure if comment is possible? The image is a flat, produced using a laptop screen as a luminous surface.

The target is a white image created in GIMP with the laptop screen at full brightness.

http://www.synergous.com/wp-content/uploads/2010/07/IMG_3381.jpg

[Nocturnal]

The most important things with flats are:

- uniform target
- exposure length keeps the ADUs in the linear range of the sensor

As long as both are satisfied this will work great. Uniformity of LCD panels can be a problem. In fact I just got of the phone with Vizio to replace my high end LED backlit TV because there were some slight darker areas that were distracting.

[Nigel Ball]

Rowland

I think you're using the Canon 1000D?

That is the camera I had before I bought the QSI

The 1000D has a 12 bit converter so the full range is 0 to 4095. I used to make sure the average adu of the flat was just under 2000

I've dug out one of my old flats and below is the screen grab in Maxim showing the distribution

HTH

Nigel

[Silvercup]

Hi:

I'm going to use a digital picture frame. I'ts cheap and portable.

I'll post the results.

Best, Silvercup.

[Nocturnal]

Good idea!

[astropixel]

Thanks, Sander, Nigel, Silvercup.

I think uniformity is OK. How do I measure ADU in Pixinsight?

Interested in seeing the results with a digital picture frame too.

This is the master flat showing histogram distribution?

[Nocturnal]

ADUs are pixel values. Unfortunately the default way of reading FITS files in PI means that the 64K values get rescaled to 0-1 which is fine for processed images but not for raw data. At least to me the original 0-64K values have meaning Luckily you can adjust the readout mode to show integer values. Click on the blue triangle next to the readout values in the bottom of the window.