Accuracy of Bhatinov mask

[MarkOw]

Hi,

Wondered if anyone had any knowledge of how precise bhatinov masks need to be to work well. 

I was going to 3D print a few for my camera lenses and scopes but two possible issues.

1. My old 3D printer isn't the highest resolution, so the mask will not have perfectly sharp edges.

2. There seem to be different patterns available, some with more slits (harder to print accurately) and some with fewer slits (easier to print but does this make them less precise on focusing?)

Any experience on this would be useful, or should I just buy a set of commercially made masks instead (although seems less fun!) 

Thanks

[Vroobel]

Hi,

Try this online creator together with any 3D designing software:

https://satakagi.github.io/tribahtinovWebApps/Bahtinov.html

Do you have 0.2mm nozzles? They are highly recommended if you want to play with precise models.

Good luck.

 

[Xilman]

54 minutes ago, MarkOw said:

Hi,

Wondered if anyone had any knowledge of how precise bhatinov masks need to be to work well. 

I was going to 3D print a few for my camera lenses and scopes but two possible issues.

1. My old 3D printer isn't the highest resolution, so the mask will not have perfectly sharp edges.

2. There seem to be different patterns available, some with more slits (harder to print accurately) and some with fewer slits (easier to print but does this make them less precise on focusing?)

Any experience on this would be useful, or should I just buy a set of commercially made masks instead (although seems less fun!) 

Thanks

 

Given that I used a craft knife to cut one out of a sheet of corrugated cardboard which was part of the packaging of a replacement washing machine, I would say that it doesn't have to be very precise at all.

It worked perfectly for months but started getting a bit tatty. It's replacement is 1mm thick stainless steel which should last essentially forever.

I confess that I had never thought that I would rule a fully functional diffraction grating with a craft knife. It is a shame that I don't have any pictures of it to show you.

[AstroMuni]

1 hour ago, MarkOw said:

2. There seem to be different patterns available, some with more slits (harder to print accurately) and some with fewer slits (easier to print but does this make them less precise on focusing?)

This should help https://www.cloudynights.com/topic/224593-better-alternative-to-bahtinov-focusing-mask/

[tomato]

+1 for the mask cut out of corrugated cardboard. Mine worked a treat and only got binned after Tomatobro  bought me a nice laser cut one.

[MarkOw]

amazing, thankyou, so the answers is to forget the fancy 3d printer and use a knife and cardboard instead!

Thanks for the links, I'll try them out anyway. 

[AstroMuni]

15 hours ago, MarkOw said:

amazing, thankyou, so the answers is to forget the fancy 3d printer and use a knife and cardboard instead!

I cut mine out of the plastic cover page of a Tesco notebook as I wanted it to be a bit more durable than cardboard 🙂 

[Steve Ward]

20 hours ago, MarkOw said:

Hi,

Wondered if anyone had any knowledge of how precise bhatinov masks need to be to work well. 

2. There seem to be different patterns available, some with more slits (harder to print accurately) and some with fewer slits (easier to print but does this make them less precise on focusing?)

Any experience on this would be useful, or should I just buy a set of commercially made masks instead (although seems less fun!) 

Thanks

 

The pattern and spacing varies depending on the focal length/ratio of the optics being used.

When I collected my laser-cut masks from Keith of StarSharp years ago he did explain the technical side of it but that info has wafted away into the ether , but suffice to say that the correct pattern for your 'scope.lens does make a difference , hence the mask generator software and the multiple options available on the FLO page.

How they're cut matters less provided they're cut accurately , to be honest I'd go with the StarSharp mask as they're a very reasonable price , work extremely well and last forever.