American Association of Variable Star Observers (AAVSO)
Sun, 06/25/2017 - 11:04

I use a light box with low voltage "grain of wheat" tungsten light bulbs to create my flats.  For years I've been annoyed by the fact that the B flats take much more exposure than the rest of the filters due to the poor output of the tungsten bulbs in the B band.  I've occasionally looked for alternative light sources for my light box that have a more balanced output but could not find anything that I liked. 

Does anyone know of any newer types of small light bulbs that would be suitable for a small light box?  I know that there are newer LED lights that appear white but heard that their output is not smooth across the visible spectrum.

Here's what I'm looking for:

1) Balanced output from the B band through Ic, with a smooth continuum in between.

2) Low voltage (3 to 12V DC).

3) Little or no waste heat (I don't want to start any fires inside my light box!).

4) Low cost.

Appreciate any advice on this subject from other CCD photometrists.





light box

Hi Bob,

There are several ways to address this problem that I can think of quickly.

- use a second bank of the bulbs that can be switched on when you are doing flats.  You might even run this bank at higher voltage to increase the color temperature.  At worst, you double the light and halve the exposure time.

- use quartz-halogen bulbs.  They run hotter/bluer and so your B exposures would be shorter.

- add a second bank of white or blue LEDs, and use those when you make your B flats.

- do your blue flats as twilight flats rather than lightbox.

- replace the light box with an EL screen, like a flip-flat.  More expensive, but gives good BVR flats.  Of course, then your long-exposure flat becomes the Ic flat!


American Association of Variable Star Observers (AAVSO)


Thanks for the tips.  Since I already have some mini tungsten bulbs, I'll probably just run then at a higher voltage to get the light level I need and maybe a slightly hotter color temp.