What's the deal with Bahtinov focus mask?

[emadmoussa]

So..yeah, not a clue. Does the focus mask make any difference really?? oris it another Accessory you must have but end up not using at all?

[Paul Laws]

Best 15 quid you'll ever spend. Seriously.

Regards.

[steppenwolf]

I use mine every imaging session - an invaluable aid to focusing for imagers.

[emadmoussa]

Hoe about visual?

[emadmoussa]

HOW

[Spec-Chum]

Have you ever looked at a star through the top of a tree?

If you have you'll notice that even through the tree when you're in focus the star looks like a star but once you start to defocus the star will split into lots of random shapes scattered over a wider area the more you defocus due to the branches of the tree getting in the way.

That's what this mask does, but in a much more controlled manner. When the star looks like, well, a star you know you're in optimum focus.

Not really essential for visual work, we can get close enough by our eyes and the size of the star point alone, but it's useful for astrophotography.

[emadmoussa]

I mean, what does it actually do you cant do manually or without it?

[RikM]

Completely unnecessary for visual, absolutely essential for imaging.

It changes the shape of bright stars into a set of three diffraction spikes. If you are a little out of focus, the middle spikes will be offset to one side or the other. As you get closer to focus, the middle spikes cross through the centre of the other sets. When you are in perfect focus, they will cross exactly through the centre. It is a very accurate way of focussing.

[Paul Laws]

Well I suppose if you are gifted with far superior eyesight to the average Joe then you won't need one.

Putting the central spike between the auxiliary spikes is so straightforward it makes no sense guessing if a star is in focus.

Some software allows a FWHM figure but I still prefer the mask.

Regards.

[PeteC]

Not necessary for visual but for imaging if you'd rather spend 5 minutes getting perfect focus using a mask instead of an hour messing about without it and still getting it wrong then I think the mask wins.

[mareprah]

I decided to get my own bahtinov when i spend a whole night imaging, just to come into the house noticing that i didn't hit the perfect focus. Whole night spent miserably... Get it or make it if you're going into AP.

[sammy1075]

http://stargazerslounge.com/topic/140075-good-by-bahtinov-hello-the-lord-mask-amen/

have a look at this for the SW 80ED, could the same thing be made for other scopes!!!!!

[nightfisher]

Im mainly visual, but have a bahtinov mask for each of my scopes, they are a superb item

[emadmoussa]

Im mainly visual, but have a bahtinov mask for each of my scopes, they are a superb item

As far as I know, they don't make much difference visually, do they?

[Spec-Chum]

As far as I know, they don't make much difference visually, do they?

That really depends on how accurate you can focus by eye. Visual use is quite forgiving in this respect, AP not as much.

[The Sailor]

Maybe this will be of some help:

http://en.wikipedia.org/wiki/Bahtinov_mask

Jim

[Scott]

i use it for both visual and ap. the time it takes it makes no sense not to use it.

Scott

[emadmoussa]

I'm mainly visual, use a webcam for planetary imaging through a guidescope. Anyway, will it make easier for planetary observation? All the examples I saw so far were of deep space..

[r3i]

I'm mainly visual, use a webcam for planetary imaging through a guidescope. Anyway, will it make easier for planetary observation? All the examples I saw so far were of deep space..

Still very handy for planetary imaging - point your webcam at a nearby bright star first then use the mask to get that in focus, then you can go to the planet with your kit in focus (remembering to remove the mask of course).