Hey all,

Looking for some advice about a specific effect. LDing an opera and the director asked for a 'lunar eclipse' effect and I'm trying to think how to do this technically.

The plan is to have a glass moon gobo on the cyc. Having multiples isn't an option budget wise, so can anyone think of a way to slowly block out the light (that would be remotely controllable). My first thought was a DMX dowser, but in my experience these tend to move quickly and be full or nothing, as opposed to a nice, smooth, slow motion.

Does anyone know of a brand of dowser that could accomplish this or have any other suggestions?



Well-Known Member
If your eclipse effect is in front of the light rather than in the gate (gobo slot), it's going to be out of focus at best. Try it with a piece of wood or something as a test (don't start a fire).

I wonder if there's a super clever way to install a custom shutter with a curve cut into it, and control it with a servo from outside the fixture. I'm sure it's possible, with only several weeks of R&D.


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Premium Member
I uploaded the program I wrote to control our dowser. You will need a Phidget USB controller for a regular servo. The angles of 'Open' and 'Close' are settable, as is the speed. Edit the .ini file to change them. Build yourself an arm to attach to the servo with whatever shape you want the shadow to be on the other end.


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Renting to Corporate One Fixture at a Time.
You could do a S4 on a stick with the gobo and have one of your follow spot op manually do the eclipse. With whatever shape you could come up with.

It's not remote controlled but if you got an op sitting there.


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Senior Team
Premium Member
I don't think a douser will work. They're specially designed to NOT go in the optical plane, so as to make a nicer fade without "artifacts," which is exactly what you want in this case. You want to see the wipe of the blade. As said, most dousers won't go slow enough, if there is any speed control at all.

I doubt even the best moving light would work, but here's one thought provided you have a light with two interchangeable gobo wheels. (MAC ViperProf or VL3000SP come to mind; I'm sure there are other/better/more suited to the application.)
Wheel 1 has the moon gobo, always in.
Wheel 2 has an open slot and next to that is a "black dot" glass gobo (like a circle/cone gobo without the connecting lines.

Roll Wheel 2 in as slowly as the fixture allows. With some, it might be smoother using mSpeed or vector mode.

Two lights, each with at least two phases of the moon gobos (steel) and cross fade between them, then advance the dark unit's gobo. Like an old-fashioned slide show with two projectors.

An alternative, provided a visual moon is not used, is to fade out every light from SR to SL (or the opposite) in a cascading fashion. It will probably take several subtle cues for this, and at some point someone will ask, "Why is that side of the stage dark?" Is the trouble worth it as opposed to a 100ct fade to black? Designer's Decision.

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