bahtinov masks

[Willow127mm]

Hi all I have bought a nexstar 5se mask by accident as I own a 5 inch Nextstar slt goto and I was wondering if they are compatible or if I need to sell it and start again.
any help appreciated.
Brad

[glend]

From an aperture point of view it would be fine however, the focal lengths are different and the spacing of the cutouts are designed for a particular focal length (I think). There is a Bat Mask making website that allows you to plug in your scope specs and then download a template to cutout your own - if you download the one that's right for your scope you can then compare it with the one you have.

[Willow127mm]

Thanx mate much appreciated
Brad

[jenchris]

Realistically it makes little difference.
you can use a three armed mask and it will work.
It just is a little clunky and fat I the ep.
more slots make for finer spikes.

[mariner10]

Hi Brad, I had a couple made up by a local mob and they are both the same pattern but for different sized apertures. One suits a 10" the other my guide scope and both work fine.

[julianh72]

If the mask you bought seems to have wider slots / fewer edges than the optimum for your telescope, you can try stringing it like a tennis racket, with one (or more) pieces of opaque string / thread running down the centre of each slot. You can either drill holes and string it like a tennis racquet, or you can glue lengths of string to the mask with a hot glue gun or similar. Make sure to keep the strings taught and parallel to the edges of the slots.

Voila! Twice as many edges, with very little loss of Aperture.

In fact, you can make a very effective Bahtinov mask using ONLY string for the diffraction edges:
http://njstargazer.org/Bahtinov.asp

[Willow127mm]

Thanx 2 everyone for their advice
much appreciated
Brad