This project is an accessory that will help you to take great astrophotos using the camera on your smartphone. Unlike some commercially made versions, our design can be adapted to suit a wide range of phone models.
The method of imaging used is called ‘eyepiece projection’ or ‘afocal projection’ because it involves taking a photograph through a telescope’s eyepiece (unlike ‘prime focus photography’ where the camera replaces the eyepiece).
The camera lens must be firmly supported in a similar position to the eye when visually observing. This is where our adaptor comes into play.
Tools – A hack saw, tenon saw or similar; drill and bits for screws; a 40mm bit for nosepiece hole; files
Materials – A small sheet of good quality 6mm plywood (about A4 size); short lengths of 20x10x1.5mm and 15x15x1.5mm aluminium channel
The phone is held between two pairs of clamps mounted on a rigid baseplate.
This has a nosepiece which securely inserts into a tube that clamps to your scope’s eyepiece.
These two parts are made from plumbing fittings: a push-fit straight connector and a blanking plug for 40mm PVC pipe.
This means that it is easy to attach and remove the whole unit without any fiddling about in the dark.
The clamps have thumbscrews and are spring-loaded, facilitating small adjustments to the alignment, allowing you to centre your phone’s lens precisely over the eyepiece.
Hold the phone
The eyepiece (and the distance between the eyepiece and camera) magnifies the view of the object.
By exchanging the eyepiece for one of a different focal length, the size of the image can be varied.
Large magnifications do result in dimmer and fuzzier images, so this technique is best suited to bright objects under good conditions.
Our prototype was designed around a Google Phone 2, which has a fairly large case, but by slightly modifying our downloadable plans you can adapt the design to suit any phone of up to 12mm thick (adjust the amount of soft padding inside the clamps to grip your phone).
We found it helpful to attach the finished clamps to our phone and draw around them on a scrap of card to check their positions before cutting out the plywood base plate.
Many phones have their lens behind the top right corner of the screen, but if your phone is different it should be easy to adapt the layout of the base plate to suit.
We fitted our plumbing connector eyepiece tube to a 12mm Plössl, but we found that most of our standard Plössl eyepieces fitted well.
You might consider buying and fitting a few of these inexpensive tubes to a selection of your eyepieces so you can experiment during an imaging session without having to unscrew anything.
Print out the downloadable plans and use them to mark out and cut the aluminium channel.
Use the drill, hacksaw and files to produce the required shapes.
Make sure there are no rough edges before gluing anything together.
Glue the two sides of each clamp together.
We added an extra top layer of aluminium to increase overall strength.
Cut the inner blocks and knobs from plywood and drill to fit the nuts and screws.
To obtain the springs we cannibalised an old pen.
Assemble the inner parts of each clamp, checking that all fit and operate properly.
We added thin felt inside the inner clamping section so it moved smoothly but without being loose.
When you are happy, glue the blocks into the outer case.
Draw out the shape of the base plate onto your plywood.
After checking the layout with your clamps and phone, carefully cut it out and smooth the edges.
Create the slots by drilling a row of holes then filing smooth.
Add small strips to create guides.
Paint the base plate then cut the PVC plumbing parts.
Remove the blank end of the socket plug.
Pull off the ring and O-ring from one end of the connector then cut a series of slots.
These will compress around the eyepiece with a Jubilee clip.
Loosely fit the clamps (fully tighten them once the phone is in its best position).
Glue the nosepiece into the base plate.
Attach the eyepiece holder to an eyepiece with a Jubilee clip, then fit the phone and push the nosepiece into the holder.