focus mask for DSLR

[m37]

Hi all

I've made simple focus masks for every scope I've ever had, I get on really well with them; particularly the cost

[Thalestris24]

Hi

Sorry, I can't help... I imagine the pattern would be too difficult to scale down - but I may be wrong! I use APT focus tool for scope and dslr - just minimizing the FWHM / HFD seems to work quite well.

Louise

[davew]

I've used a Y mask with arms around 1.5mm thick. The angles are exactly the same as the classic Bahtinov.

I found that this would work reasonably well down to around an 80 to 100mm FL lens. It's just possible to see the spikes with a 50mm lens but the accuracy can't be good enough unless the lens is stopped down to, say, f4. When I use the Y mask I normally aim at a bright star ( Alpha star in any large Constellation normally works ) because a small star doesn't produce enough energy.

The classic Hartmann never worked for me.

Dave.

[m37]

Thanks for the replies guys. I will keep at it.

Cheers

Chris

[m37]

Well I seem to have cracked it! Gave up on card and scalpels and got a peanut butter jar lid and drilled two holes near the centre with an HSS bit. Magic.

[Astrosurf]

Excellent! Can you post a pic?

Alexxx