[[1ponders] (Paul)]

Hint: in masking in the triangles keep the adjacent sides of the triangles as parallel to each other as possible.

The closer to parallel the sharper the diffraction spikes when focus is achieved (depending on seeing that is). My bottom triangle looks slightly out of alignment with the top two but that is only due to the angle I took the photo. All the triangles are equilateral triangles and of the same size. I have read that the shape and size of the holes isn't critical. However after using unequal sized and shaped holes and equal sized and shaped, I've found this arrangement much easier to use, especially if the seeing is not so good.

Notice I've used three long pieces of tape to form a large equilateral triangle on the outside then filled in the final side of each triangle where the outer tape crosses the perimeter of each circle. I used a compass with the radius set from the centre of the mask to the outer edge of one of the circles and scribed a circle round all three circles. Where where it touched each circle was where the long pieces of tape ran from/to.

Do both sides of the mask to stop sticky tape from touching the corrector plate for SCTs or picking up bits of dirt that can become dislodged and fall into your OTA for newts, and to strenthen the mask.

Next fine night I'll image Sirius to give an idea of how the spikes look/work

Good luck

ps I cut out the lid of a twenty litre plastic mayonaise tub for the mask and cut a Brocolli box lid into a circular collar to fix the mask to, to slide over the top of the OTA.