Horizontal Heavens Observatory "...From  A Galaxy Far, Far Away"
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This page was last updated on 10/08/14.

FLATFIELD LITEBOX PROJECT

1/4" Foam core was used for the donuts and the local Paper Tube Supply provided unique sized tubes at about a buck a foot.  Take your tape measure and size to your OTA.  The second image shows the "Funky Foam" sheets that helped me size and snug the dewshield/litebox junction perfectly!

White LED lights provide the illumination. "Funky Foam" was also used to coat the inside of the Litebox in order to help with diffusing light.   Used 4 for this litebox that will serve a NP-101 and TMB80/480 refractors.  When I get around to building the litebox for the 10" SCT I will use 6-8 LEDs.

UPDATE (below):  After Testing I had to eliminate light leaks so I added aluminum furnace tape at all hot glue edges being careful NOT to short out wiring.  Testing also showed that lights were too bright and needed to be dimmed so I added another diffusing layer, this time a piece of Mylar just above the lights.  These modifications now allow me to work with LRGB flats at f/5.4 without worrying about shutter induced errors from having too short of an exposure.  *SEE TABLE BELOW

 

FILTER	EXPOSURE @ f 5.4	ADU COUNT (White)
Luminance	0.86 sec	20,000
Red	4.71 sec	20,000
Green	2.35 sec	20,000
Blue	2.59 sec	20,000

UPDATE #2 - I built a second litebox of nearly the same size but 3" shorter and moved the second diffuser layer to the center instead of the outer donut.  this unit is somewhat faster with just the slightest dimming in the center over the first model.  The central bulls-eye is so slightly dimmer on a CRT monitor that if I posted comparative images on the Internet one might not be able to see the difference if posted in JPEG format.  Pragmatically, this will work out just fine in flat-fielding astro-images.  Below you see the difference in the construction from iteration number one and number two.

Litebox in place over the NP-101.  Used a modular plug to provide 12v power to the unit.  The total tube length is just 11" and I am trusting that this is enough.  I visually checked each LED so that each LED could illuminate the entire top of the tube/box without being cut off.  I did note that the LEDs do seem to be directional and care needs to be taken in pointing them diagonally across the FOV.