Pointer Project

Below are downloadable files for creating a planetarium pointer. This project was supported by a PPA minigrant awarded to John Erickson in 2022.

• The PDF has a materials list and detailed instructions for building the pointer. 

• The .stl file has a 3D model for the body of the pointer, to be printed on a 3D printer.

• The .ai file has an Adobe Illustrator file for the arrow that the pointer projects. It is meant to be cut with a laser cutter, but the instructions in the PDF have an alternative arrow that does not require laser cutting.

As 3D models can be edited, this project is ongoing, and the intention is that as improvements are developed, they will be incorporated into the design. People are also invited to make their own improvements or customizations, and if they want to share any design on this site, contact John Erickson. (jerick<at>berkeley.edu)

John Erickson's rationale for this project:

I have long felt that every pointer that I have used has had some shortcoming. I’ll list a few. Some of these items come from others who have given me feedback about what they would like in a pointer, but most of them are things I have been thinking about for a long time. You may think I am being nit-picky, and so I am, but if even a small shortcoming can be fixed, then why not? Another note: Since I enjoy doing participatory programs, and since I wish to encourage others to do the same, instead of referring to the people who come to programs as ‘visitors’ or ‘audience’ I call them ‘participants.’ I suppose that word also applies to the presenter. 

• Pointers can be too bright. When pointing to the Pleiades you want something that does not spoil the view.

• Pointers can be too dim. In a daytime sky, or in a brighter image on the dome, the pointer can get lost.

• Laser pointers are not completely safe. The first thing some participants do when handed a pointer is ‘look down the barrel.’ A participant may also inadvertently shine a pointer into the eyes of another participant.

• The meaning of a dot is not as clear as the meaning of an arrow. The stars and planets are dots, and pointing out a dot with a dot is not optimal.

• Pointers that project an arrow sometimes have a poorly designed one. One I have seen in more than one pointer is a simple angled line, like a 'V' shape, which is ambiguous. Some participants use the point of the angle to show what they are pointing at (which is what I think the designers had in mind,) but some participants put the object they are pointing to within the angle, as if it is the mouth of Pac-Man eating the object.

• A pointer arrow can be too small, and it is difficult for the presenter to make sure participants find it and follow it. There are techniques to deal with this problem, but a larger arrow helps.

• Any pointer with an adjustable focus gets out of focus.

• Pointers with momentary contact switches may make sense in some contexts, but when using them in a participatory show, you have to show where the switch is every time you hand it to a participant.

• The switch is the first part of many pointers to break.

• A switch that is at the butt of a pointer is poorly placed to turn on and off easily.

• Changing batteries is a chore. So is disposing of used batteries.

So, the pointer I have developed has these features:

• A switch with two brightness settings,

• Plug it into a USB C to recharge it,

• Can be made with different colors of LED so that you can have multiple participants pointing at things, and you know which arrow belongs to whom,

• Switch is placed for convenience,

• Fixed focus,

• Shaped to be easy to hold, does not roll when set down, and is not too small to get lost in the dark,

• Fun to build, I hope.