Custom Bahtinov

[Ken82]

Just got a new clear mask from pro astronomy. Really pleased with this 😀

[tomato]

Nice, does it work as is or do you have to paint it black?

[x6gas]

It'll work as is.

The built-in Bhatinov on the WO RedCat is also clear.

Ian

[Ken82]

15 minutes ago, tomato said:

Nice, does it work as is or do you have to paint it black?

I believe this type of mask gives larger spikes so it’s easier to focus narrowband. 

[tomato]

Right, I’ve noticed a conventional mask does give “intermittent” spikes when trying to focus with NB filters, so this sounds like a good solution.

[fozzybear]

who is the supplier tried to google Pro astronomy

Cheers

[Ken82]

https://www.proastronomy.co.uk/

[fozzybear]

On ‎14‎/‎09‎/‎2020 at 23:44, Ken82 said:

https://www.proastronomy.co.uk/

there are no prices on there website is that correct? Do you have to email them?

[Stu Todd]

You could make your own for next to nothing - http://www.deepskywatch.com/Articles/make-bahtinov-mask.html

[Ken82]

2 hours ago, fozzybear said:

there are no prices on there website is that correct? Do you have to email them?

If you fill out the details of your custom mask they will get back to you on price. 
 

£20+ postage for my 120mm custom mask. 

[vlaiv]

On 14/09/2020 at 19:54, tomato said:

Right, I’ve noticed a conventional mask does give “intermittent” spikes when trying to focus with NB filters, so this sounds like a good solution.

That always happens with B masks whether mask is clear or not.

Same reason spikes on stars in RGB are rainbow colored. Angle of diffraction of light depends on wavelength of light. This is how diffraction gratings in spectroscopes work. Same happens here and what you see is first, second, third, fourth, .... order lines smeared by seeing with narrow band and mask.