Garden Spot Observatory
Flat Field Box
The purpose of this tool is to allow images of a plain, uniformly lit
(flat field), surface to be taken.
Such images capture imperfections, dirt and dust in the imaging train. Later these flat field images
can be digitally subtracted from the images of your intended subject.
The box is made of foam core board sections held together by white gaffers'
The lid is five sheets glued, taped and cut with a whole that matches the circumferance of the telescope's
optical tube. The diffuser (a quilter's template) is sandwiched between the bottom two.
Inside the lid four incandescent bulbs are wired in series. A small wall
deflects the light down into the box
for even illumination of the diffuser screen.
The box is sealed to prevent dust from accumulating on the screen.
A potentiometer and 9-volt battery are attached to the outside allowing the intensity of the light to be
adjusted. The box sits on the end of the telescope and weighs less than 2 lbs.
Foam Core Boards
White Gaffer's Tape (aka duct tape)
Diffuser Plastic (quilters' templates work well)
(1) 9-volt battery
Radio Shack Parts:
(2) 272-1132 - 2.47v bulb 2-pack
(4) 272-356 or 357 - base
(1) 271-265 - potentiometer
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This page and all images are Copyright PAO 1998-2002. Images may be reproduced with permission.