BASIC DESIGN AND COMPONENTS:

An old Meade DSI monochrome CCD camera was used, that was just laying around collecting dust. The camera was mounted in a wooden box for ease of construction and component layout. A shutter system was also designed to protect the CCD from direct sunlight during daylight hours.

> 1/2" Birch plywood for housing. (primed + 2 coats of exterior latext inside and out)

> DSI monochrome CCD- The filter bracket was removed. Custom adapter bushing made to mate lens to camera.

> 5" diameter acrylic dome to cover camera and shutter area.

> 12VDC 80MM Fan to provide good air flow inside dome and eleminate any fogging.

> Soleniod- 12 VDC Pull type to actuate the shutter mechanism.

> Fish Eye Lens I could not find the one that I purchased sometime back. This link is the closest comparable unit.

ALL SKY CAMERA CONSTRUCTION

Link to >NEW DESIGNS<

This project is an inexpensive approach to providing a nightime view of sky conditions during my imaging sessions. The occasional cloud can easily be detected from my control monitor inside the house. As seen in the image below, a "sucker hole" is opening up around the Big Dipper and clearing seems to be developing from the North-East.

Note: The total field of view is ~ 150 Deg. North to South. The step on the South side is a silhouette of the corner roof line on my house. Even though some of the field-stop is cut off in the East and West, there is still plently of visible sky to see approaching clouds.

DETAILED VIEW OF SHUTTER PIVOT MECHANISM

This view (with fan removed) shows the solenoid pistion connecting rod attached to the small lower bushing. As the solenoid plunger pulls back it rotates the lower bushing and upper bushing attached to the shutter. Only 1/4" travel with this arrangement gives enough travel for the required shutter movement. That's about all most of these solenoids will travel. I modified the piston and added an internal spring to return to "home" closed postion.

FINISHED UNIT
Shown mounted on the weather station mast. A simple hinge for the plastic dome was made from .040" thick polyetheylene. A custom machined aluminum cover was also added to protect the 12 vdc soleniod and its wiring..

MOUNTED ON WEATHER MAST
A simple L shaped bracket off the side of the box allows for effective mounting and support. This also allows quick removal for any needed maintenance.

AN AFTER THOUGHT ADD-ON- PHOTO-SENSOR TO CONTOL THE SHUTTER
This finished view shows the Lens Assemby for capturing ambient light. The system is set to open the shutter when it starts to get dark/ after sunset and close the shutter at daybreak/ before sunrise.

LENS ASSEMBLY FOR CAPTURING LIGHT
The clear lens was custom machined from acrylic rod stock and the light baffle from 1/4" I.D. brass tubing. This assembly captures the outside light and acts as a light pipe to transfer the light down to the Phototransistor inside the camera box. The small black plastic flange is a tight press fit over the lens for mounting.

The entire assemble was fit into the box and glued in place with super glue.

PHOTO SENSOR SWITCH INSTALLED IN CAMERA BOX
Things were getting a bit tight, but the board fit-in OK. The phototransistor simply slips up inside the brass "light tube" and I just super glued the relay housing down. If I ever need to remove the circuit, I should be able to lightly pry it out with sharp chisel. I know this is a bit rought, but very effective. It would have been very difficult to get in with a screw to hold things down at this point. Also note: The Sensitivity Adjustement is a small brass rod with a chisel point that presses into the Circuit Board Potentiometer. This rod extends outside of the box allowing light sensitivity to be controlled.

EVERYTHING CLOSED UP WITH FAN COVER PLATE
I used 1/8" clear plexiglass to mount the fan. Also, seen here are (3) power recepticals for 12vdc Supply, A Switch Over Ride Circuit, and a 15vdc Supply.

WIRING DIAGRAM

THE PHOTO SENSOR SWITCHING CIRCUIT
This is a do-it-yourself Kit. Ya get the PCB, components and some instructions. "Soldering Required" After diligently putting this thing together......it didn't work! I found that their instructions and drawing were incorrect for the wiring of the Phototransistor. I had to reverse the +/- connections. After that, all worked well. It seems to have a good range from light to dark and is quite sensitive. The black/red wires are 12vdc supply and the 2- black leads are the switch control wires.

The circuit has a SPST Relay Switch for control and will handle 3 amps @ 12 vdc. This is more than enough to handle my solenoid actuator. The unit is powered by 12vdc. Source for the kit: MCM Electronics

MEAD AUTOSTAR ENVISAGE USED FOR IMAGE CAPTURE

I'm running in auto exposure mode, saving the jpg file to my web folder, overwriting the file and refreshing the image on the web page every 5 seconds. I'm taking images @ 8 sec. exposure with dark frame subtraction and you can easily see stars down to 3.5 -4.0 magnitude.

NOTE: The Meade DSI CCD camera is very sensitive and works best during dark-sky nights. Sun-lit or Moon-lit skies over-saturate the camera. LINK TO CAMERA

SOLENOID PLUNGER MODIFICATION
Added a spring to return the plunger. A similar plunger shown above before modification. Also shown is the push-rod made up from pieces of precision brass and copper tubing. To overcome spring force, I'm using 15VDC. The solenoid is drawing about 420 milliamps and does get warm (140 deg F) but seems to be robust enough to easily handle this on a continous duty basis.

SHUTTER IN CLOSED POSITION

The small turn down tab on the right of the shutter acts as fixed stop for the closed postion. This tab rests against an inner light ring baffle. The inner light ring baffle is just slightly higher than the fish eye lens and the felt covered shutter just clears the top of the baffle to minimized light leaks.

NOTE: It's not a perfect light seal, but good enought to protect the camera from direct sun light and produce dark frames on a dark night. Also, the brass shutter was covered (both sides) with Protostar Flocking with adhesive backing. The inside of the light baffles were flocked as well.