Focusing on planets with a Bahtinov mask???

[beamer3.6m]

Hi

I asked on another thread if you can use a Bahtinov mask to focus a webcam on a planet but thought it would be useful to ask it again in a separate thread to ensure it is clear anddoes not detract from the original thread.

So, if for example you wanted to focus your webcam on Saturn can the Bahtinov mask be useful and if so how, it appears that the mask can only focus on a fixed point like a star.

Confused.

[Merlin66]

The mask need the diffraction disk from a pinpoint star object to generate the spikes.

It just won't work on anything other than a star.

[Stephen]

I wouldn't dare question an expert, but I managed to get diffraction spikes off of Saturn three nights ago without any problems?

[nightfisher]

due to infinity focus i think if you focus scope on a star with b/mask then swing onto planet or lunar feature it will still be in proper focus, might be tricky focusing a webcam on a star so you could use a 6.3mm ep then pop in webcam when planet centre`d

[Merlin66]

Kh3ldar,

Which scope were you using?

The focal length must have been short enough for the planet to appear as a pinpoint of light....

[Bizibilder]

In theory you could focus your scope/webcam on a bright star and then slew round to find the planet which should then be in perfect focus. The trouble is that finding a planet with the tiny chip of a webcam is tricky! I find that I can focus well enough using the laptop screen - however you must take your time and I often spend 10-15mins getting it "just right". Time well spent - as your images will show.

[Stephen]

Kh3ldar,

Which scope were you using?

The focal length must have been short enough for the planet to appear as a pinpoint of light....

SW 200P 1200mm, 1/3" Mono CCD - Saturn appeared as a pea admittedly, but not pinpoint?

pic

[Psychobilly]

With the Bahtinov you may get multiple images of Saturn...I did it with a crescent Venus once looked quite cool never tried it on Saturn though...

Peter...