bahtinov mask for lunar

[nightfisher]

does a focus mask work for lunar imaging, so you focus on a star then pan across to the moon keeping the same focus? just cant help thinking a star will be much further away than the moon

[Demonperformer]

yes. The star is further away, but if you think of the cone of light emanating from a point on the moon or star, culminating in a 6" diameter circle (the aperture of your telescope) the difference in terms of angle of the cone is negligible compared to the coarseness of the average focusser.

[Jannis]

In theory, it won't be acurate as a star is waaaaaay futher away then the moon. but i tried it myself, and for planetary, it works well. for lunar it worked too i guess, but i could focuse moon just as acurate manually trough live-view though.

That was with an F5 scope and the 550d camera.

[guyroch]

does a focus mask work for lunar imaging, so you focus on a star then pan across to the moon keeping the same focus? just cant help thinking a star will be much further away than the moon

Yes, I do. Infinity is infinity.

Guylain

[Bizibilder]

It works very well - infinity is pretty much anything over a few hundred yards as far as a scope is concerned.

[Photosbykev]

With a DSLR and 600mm prime lens it is possible to see the focus changing from the front of the moon to the edge but the DoF covers any variation in focus

[PeterW]

I get focus on the moon by looking at a zoomed in image from my camera and rolling the focus back and forward to determine a range of best focus and then dropping the focus in the middle. Can take a few attampts and seeing can mess it up. Pick on a nice high contrast region.... the moon has lots and it is quite simple and gives good results.

Cheers

PEterW

[JamesF]

Infinity is infinity.

Guylain

Well, there's a statement to make

The set of integers is infinite in size, but between each pair of consecutive integers is an infinite number of real numbers, so

the infinite set of real numbers must be infinitely bigger than the

infinite set of integers.

Maybe

James

[nightfisher]

just had a look at the mask generator site and my laptop wont allow me to open the file, so gonna have to try to buy a ready made one for the tal100rs, any idea where i might get one

[Freddie]

download GIMP, it's free, that will open the file for you.

[astrobob]

..

[nightfisher]

download GIMP, it's free, that will open the file for you.

thanks for the tip freddie

[Demonperformer]

Or make a Y-mask - does the same job without all that tedious cutting out

[RobH]

Yes....use your bahtinov to focus on a star and then shift to the moon.

Focus will be the same.

This goes for planets too of course.

[Andrew*]

It works very well - infinity is pretty much anything over a few hundred yards as far as a scope is concerned.

With a DSLR and 600mm prime lens it is possible to see the focus changing from the front of the moon to the edge but the DoF covers any variation in focus

I got some excellent answers when I asked this question: http://stargazerslounge.com/equipment-discussion/113977-infinity-focus-point.html

The bottom line is it depends on the scope, but in any case, you need more than just a few hundred yards, but anything from (in an extreme case) 200km outwards is effectively infinity.

HTH

Andrew

[TheThing]

I've used this process when imaging Jupiter before and it worked fine. I never really understood how, but I do know, thanks for the explanation.