Focus mask recommendations for wide(ish)-field lenses?

[Dezerker]

Hi everyone,

Do you have any recommendations for good bhatinov (or similar) masks that can be used for DSLR lenses in the 50 - 200mm range?

Even with 10x live view on the DSLR, the star and spikes are too small to see reliably with the one I have currently (which is actually designed for an ED80 scope) - with my eyesight at least.  I realise you can take a short exposure, zoom in on the image to check it, make a tweak to the focus and repeat until you get it, but that can eat into imaging time and all that fiddling increases the risk of nudging something out of polar alignment, so I was wondering if, and how people get around that?

Any advice would be much appreciated!

Dez

[Budgie1]

You can make your own, either out of something like card or using a 3D printer.

If you Google "bahtinov mask generator" there are a lot of resources available, including video tutorials and the Bahtinov Mask generator will allow you to produce a mask to your own size specifications.  

[LuckieEddie]

Here's a post from last week that may help.

 

[Dezerker]

Thanks for that - I might have a crack at making a card version (no 3d printer, sadly) but otherwise the AstroKraken folks will be getting a sale!

Thanks again!

[Gfamily]

8 minutes ago, Dezerker said:

Thanks for that - I might have a crack at making a card version (no 3d printer, sadly) but otherwise the AstroKraken folks will be getting a sale!

Thanks again!

If you  have a laminator, it is easy to print onto paper and make a fairly resilient mask that way.

I made my own yesterday - used an online generator which i printed out and laminated.  I then cut out the white bits with a craft knife and steel rule. 

I then cut around the mask, leaving 4 tabs that I can use with an elastic band to attach to the OTA (a 72mm refractor in my case)

[AstroMuni]

25 minutes ago, Dezerker said:

Thanks for that - I might have a crack at making a card version (no 3d printer, sadly) but otherwise the AstroKraken folks will be getting a sale!

Take a look at this too..its easier to make https://www.cloudynights.com/topic/224593-better-alternative-to-bahtinov-focusing-mask/

[Dezerker]

2 minutes ago, AstroMuni said:

Take a look at this too..its easier to make https://www.cloudynights.com/topic/224593-better-alternative-to-bahtinov-focusing-mask/

That definitely looks easier - thanks, and interesting to see you can control the brightness a bit by the amount that you cut out.  I might try a Y-mask first just to test...

Thanks again for all of the advice.

[newbie alert]

A bahtinov mask for a 80ed won't work precisely for a lens as the aperture and focal length is different, best to  make one for the equipment used . A friend made a decent one from a cd perspex case and scribed in the pattern with a craft knife.. worked extremely well 

[happy-kat]

I make Y masks and use with camera lenses and a 50mm telescope. I do find its easier once you get your focus by eye manually with the Y mask (don't always see the spikes) to take a quick exposure image and if using a camera I'm connected to DSLR controller on phone then save the image and pinch zoom to check the spikes close up