Rocketry Planet

Welcome to the Rocketry Planet How-To Classroom Series!

Rocket-based photography has quite a long history, dating back to the introduction of the Estes AstroCam in the late 1960s. When it was brought out, it would only take a single shot per flight, always when the parachute was deployed.

Since then, many hobbyists have modified cameras for use in rocket flight, and have devised several ingenious methods of triggering them. This series of articles will describe my own efforts in this interesting field of endeavour, and will describe the steps needed to modify and control the camera while in the rocket. The design of the rocket, and the manner of mounting the camera, is an exercise best left to the person intending to fly the rocket — although there are several articles describing various manners of mounting.

Film cameras are the types most commonly used in rocket-based photography, so I'll start with those. Later on, I'll describe my efforts to modify digital cameras for flight, along with the electronics needed to control them.

First and foremost - DO NOT modify an expensive camera! There is a very good chance that you will either damage the camera in the course of modification (I ruined a total of four, before getting it right.) or it may be damaged during the flight. No matter how well you protect things, the risk of damage is not zero — so remember to not fly anything you cannot afford to lose.

Point-and-shoot cameras are the best way to go, because they are quite inexpensive. My personal opinion is that fixed-focus cameras are preferable, because they don't take as long to be ready between shots. They are, however, increasingly difficult to find although you can likely pick up some occasionally through online auction sites. You also have a choice between 35mm and APS film sizes.

35mm is more common than APS film, so getting replacement film and processing will be easier. 35mm film can also be 'pushed' - by scraping the coded metal strip on the film canister; you can trick the camera into using a higher shutter-speed (assuming that the camera you use has that feature.) and thus get sharper pictures.

Be sure that you get a camera with an electronic shutter-control system! You cannot do the modifications I'm describing with a mechanical shutter. If the buttons feel 'soft' when you press them, it's very likely that your camera has an electronic shutter, and you can proceed.

It's also beneficial to have a camera that is activated by opening a lens-cover, as this reduces the number of wires you need. If your camera has an ON/OFF button, you'll need another pair of wires to bring them out to your control system.

Once you have your camera, it's time to start the modifications. You'll need some precision screwdrivers (Philips-head and slotted), a soldering pencil with a fine tip, some ribbon-type cable (two or three conductors, depending on whether your camera is fixed-focus or autofocus) and a place to work.

The first step is to VERY CAREFULLY open up your camera. There are several small screws that hold the case together - remove them and put them aside in a safe location.

Some cameras will not make this easy. If you have difficulty, an option is to pop the shutter button out of its recess by forcing a small screwdriver underneath it and prying it upwards. You may need to score the button with a sharp knife to do this.

WARNING! When you have the camera open, the capacitor for the flash will be exposed. This will hold a very high voltage, and WILL hurt if you should accidentally touch the wires. If you can find where the capacitor is connected to the circuit board, you can discharge the capacitor by touching the ends of a length of wire to these points. Again, you must be extremely careful while doing this - and there will be a flash and a loud CRACK as the capacitor is discharged.

If you can, it is now possible to disconnect the flash capacitor from its charging circuit by cutting the wires leading to it. Cut as close to the circuit board as possible, and again as close to the capacitor as you can. Do not worry if you are unable to do this - it's an optional step.

With the casing opened, or the shutter button off, you should see a set of contacts on the circuit board - they will be copper-coloured and shiny. These are the points you will solder to. If you have a fixed-focus camera, you will only see two contact points. An auto-focus camera, however, will have three — and you will need to determine which contacts to bridge in order to trigger the shutter. That, however, can be determined once the wires are in place.

You'll need to put a small amount of solder on each contact, in order to make the wires bond properly. Melt some solder onto the tip of your pencil, and carefully touch the tip to the contact. A very small amount of solder will be left behind, but that's all you need. Strip the wires and place some solder on the bare wires as well — being careful not to allow the individual strands of the wire to spread out. Next, holding a wire on top of the contact point, touch the tip of your soldering pencil to the wire. After a moment the solder will melt, and you can remove the tip of the pencil to allow the solder to cool. This will leave a solid joint between wire and circuit-board - test it by gently pulling on the wire to make sure that it doesn't separate. If the joint breaks, you will have to re-do it. Otherwise you can proceed with soldering the other wires into place. (This includes the wires for the ON/OFF button, if necessary.)

At this point, you can reassemble the camera. Thread the wires through the hole where the shutter button used to be, and replace all the screws you removed.

Now it's time to test your handiwork. Install a battery into the camera, and turn the power on. You won't need film for this test — that will come later. If you've done everything correctly, the little display should indicate that you have no film in the camera. If the display doesn't come on, you have some other testing to do — check for solder between the wires or the 'fingers' of the contacts.

If you have a fixed-focus camera, strip the free ends of the wires for the shutter button, and hold them together. You should hear a soft 'click' as the shutter is activated, followed by the film-advance motor. For an auto-focus camera, two of the three wires will be joined together — and the third will trigger the shutter when touched to the other two. This will take some patience, as you will need to try each combination to determine which two wires are joined together, and which is left free.

Once you are satisfied that everything is working, the wires need to be protected against mechanical vibration which can cause the solder joints to separate. Place a small piece of masking tape over the shutter-button hole, soak with CA adhesive, and coat with a layer of silicone-based outdoor caulking material.

At this point, you can put the connector of your choosing onto the free end of the wire, set up your control system, and buy some film to take pictures from your rocket.