How to make a light-tight red-light sign box for star parties - project homepage

K. Fisher Rev. 6/6/2006

Star Party Red-Light Sign Box - Front View
Figure 1 - Red-light box - front view - red-light gel screen with no transparency
Star Party Red-Light Sign Box - Back View
Figure 2 - Red-light box - back view - transparency storage folder and flashlight insertion tube
Transparency generic sample - Planet
Figure 3 - Transparency generic sample - Planet
Removable mini-mag light source
Figure 4 - Removable mini-mag light source
Red-Light Sign Box with transparency inserted
Figure 5 - Transparency inserted in red-light box
Transparency sample - Dark cloud
Figure 6 - Transparency generic sample - Dark cloud


This document presents construction plans for a light-tight box to display red-light signs at star parties. The signs are laser-printed transparencies. The box is designed to screw onto a standard camera tripod mount. Using such a sign, it is possible to set-up an informational sign in front of a telescope at a star party that displays the type of object currently in the telescope. The intent is to have several of these signs in a line of telescopes pointed at different types of objects. Using a handout describing the major celestial objects (e.g. - double stars, dark clouds, open clusters, globulars, planetary nebula, several types of galaxies), the public can browse a line of scopes for an orrey of objects.

Attention was given to making the red-light box light-tight for white light.

This red-light box will be of interest to intermediate amateur astronomers and to astronomy clubs.

The approximate total construction cost in 2006 was $67.25 U.S.D. However, about 1/2 that cost is for one box of transparency paper for a laser printer. To build the red-light box alone, including buying a $10 U.S.D. mini-mag flashlight, is about $35. With a pre-existing flashlight, the expense is about $25 U.S.D.

The brightness of the illuminated transparency is dim and best for dark adapted eyes. Because the illuminated transparcencies are dim, the red-light box is unlikely to raise objections from other scope owners at a star party. The image can be brightned by substituting a brighter LED flashlight or by omitting the internal diffusion baffle.

A simple alternative to this sign display box is to purchase a variable red-LED flashlight from Rigel Systems or Orion Telescopes for $20-$30. Place paper signs on a clipboard. Hang the clipboard either from your telescope tripod legs or from a separate camera tripod.

Construction details handouts

The materials lists is presented below. Construction details and plans are presented in two pdf documents:

Assembly time is approximately 45 minutes.

Materials buy list

Item Qty Brand-Source Used for Price U.S.D. 2006
Main functional components
Mailing Box 13 1/2" x 2" x 2" 1 United Parcel Service Project container 1.80
Mini-mag Light 1 None White-light source 10.00
Gel Sheet - Red Diffusion #120 1 sheet Roscolux #120 Red Diffusion
Available from theatrical supply companies
Typically comes in 2' x 3' sheets
Converts diffuse white to red light 5.50
Automobile air cleaner wing washer-nut 1/4 inch 20 thread 1 ACE Hardware Screw-in point for camera tripod mount 0.80
Letter-sized manila folder 1 Off-supply 1/2 holds transparencies to front of box
1/2 holds stores transparencies on back of box
Transparency film for laser printers 1 box Universal Transparency Film by 3M, CG5000, 50/Pack Make transparencies 32.00
Insert tube for light
1/2" PVC threaded pipe 1 to 1 1/2" long (5/8" O.D.) 1 Hardware store Insert tube for mini-mag light 0.80
PVC 1/2" I.D. couplers - threaded 2 Hardware store ($1.20 each) Insert tube for mini-mag light 2.40
Black rubber stopper 3/4 inch by 5/8 inch 1 ACE Hardware Make insert tube light tight 0.55
Black neoprene ring 2 1/4 inch O.D. x 5/8 inch I.D. 1 ACE Hardware Make insert tube light tight 1.80
Light seal and reflection
White flat spray paint 1 can ACE Hardware Paint inside of mailing box to increase relfection 3.30
Aluminum kitchen foil 1 sq ft Common household product Diffuser reflector 0.00
White duct tape 1 roll Ace White Duct Tape
Ace 42911
1.88" x 5 yards
Mount components and seal box inside with reflection 3.30
Black duct tape 1 roll Ace Black Duct Tape
Ace 42913
1.88" x 5 yards
Light-tight seal outside of box 3.30
Other materials
Adhesive picture hangers 2 Anchor Adhesive Picture Hangers
Pack of 5
Ace Hardware 50595 (Anchor 47904)
Second mount point to hang sign on an observatory door 1.70
Total cost 67.25

Assumed materials


Tips for printing transparencies

If MS PowerPoint is used to prepare transparencies, that program includes a toner saving feature that overrides printing black background slides.

To work-around this limitation, draft slides white on a black background. Print the slides black on a white background and onto white paper. Use a copier with a positive-to-negative reversal feature. Copy the paper slides on to the transparencies.

Another work-around is to save the PowerPoint slides to a jpg format. Then use a standard image print utility to print the jpg slide directly to the transparency. These lower level utilities usually do not have a toner saving program feature built-in.

Report errors and broken links

Legal disclaimers

No implied warranty

The content of this website are distributed without charge in the hope that it will be useful, but without any warranty, including without any implied warranty of merchantability or fitness for a particular purpose, to the extent permitted by applicable law. The content of this website is distributed "as is" without warranty of any kind, either expressed or implied. The entire risk as to the quality and performance of the red-light box and data herein are with you, including any general, special, incidental or consequential damages arising out of the use of or inability to use this website.

Site tracking and Child Safe-Surf Rating


Any original materials on this website to the extent that copyright is held by this author, including the handouts, are released to public domain. Astronomy clubs and educators are encouraged to freely replicate this site.

Prepared by: K. Fisher 5/2006