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Hartman Mask Project |
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How can you get a reasonably close approximation on focusing for astrophotography? One way is by using a Hartman Mask. Hartman Masks are relatively easy to make and will help you make it close to the focus “sweet spot” for both observation and photography.
I completed my Hartman Mask for my 150mm newt in one day with the following materials:
· Fiber board · Hole saw · Jig saw · Compass (circle drawing kind) · Wooden knob · Black Felt · Flat black spray paint. |
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Determine overall size
This can be done by measuring the exit aperture of your scope or by tracing the lens cap, as I did on mine. Don’t make the mistake of using the marked aperture of your scope. The mask needs to fit the dimensions of your scope not the dimensions of your mirror or main objective lens. |
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Determine number of holes you want to use
Minimum of two. I suggest making them at least 10% aperture as your mask itself. The closer to the outer edge you can place them the better. Two holes is easy. Just put them on opposite sides. Three holes requires a little math to get them just right. |
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Cut the holes first
Cutting the holes first will give you plenty of support. You can work with the whole piece of wood. Notice how I used concentric circles to properly align my holes. This will ensure accuracy when using the mask |
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Cut out the mask and paint
Cut it with a jigsaw and sand for finishing. I am using a fast drying ultra-flat black spray paint. This will help cut down on any reflections when using the mask.. |
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Add a knob if needed
Not that it is really necessary, I added mine for looks. You can find these at any building supplies store. |
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Finished Product
Last step, cut black felt to size and glue with white glue to back side of mask. This should help with reflection problems and gives a smooth surface that will not scratch your scope. |
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