Bahtinov Mask

[Mike]

Some time next week.

Just give me the numbers for the generator, it will be a lot easier.

I will need to convert the .svg file to .dxf for the laser cutter.

[RobertM]

Ok, will do

[Fay]

I have an 8" one I can sell

[The Thing]

I used the web generator (Mac's link below) and printed it on an A4 self adhesive photo sticker, sprayed it with photo shield stuff, then stuck it on an old plastic folder cover then cut it out with a craft knife. I believe sharp edges are crucial rather than perfectly straight lines as its the edge that causes the diffraction. I have tried a couple of configurations and fewer slots seems to be better. 8" masks must be easier to cut than one for Mick's Burgess.

[mickw]

8" masks must be easier to cut than one for Mick's Burgess.

I still see diffraction spikes when I look at a lightbulb 

At least I know it's in focus 

[Carole]

Wish I'd seen this revived thread a couple of days ago, might have saved some blisters on my fingers from all the pressing with the cutting blade.

[MarkS]

I've just seen the animation at the beginning of this thread.  I was dead impressed until I realised it was my own!

[Carole]

 

[Mac]

 

[Mike]

Note that the maximum size of the cutting bed for the laser is 310mm x 585mm so nothing over 310mm in diameter. Suitable materials - thin MDF sheeting or acrylic.

[mickw]

So the Lightbridge is out then   

When would you want the materials by ?

[Mike]

Acrylic can be cut up to 4mm depth and MDF up to 3mm. I can get materials from Hamar Acrylic which is just a short walk from London Hackspace. I'm doing some for Robert tomorrow (if he gives me the dimensions) so I'll let you know an idea of prices then. I know it is £3 per hour to use the cutter plus cost of materials on top.

[mickw]

PM on it's way

[Mike]

Did a few tests today cutting some of the 3mm MDF Mick gave me:



This was using the 80mm dimensions Robert gave me for his scope.

The acrylic Mick gave me was useless though, it just burnt. It needs to be branded Perspex apparently if you want smooth edges. I shall pick up some in black from Hamar Acrylic some time this/next week and do some more tests.

[Mike]

Just for a laugh I made some planetary gears (tenuous astronomy link) too.