Bahtinov Mask

[Luke.]

I was wondering if I would benefit from having a Bahtinov Mask?
I am only using my DSLR, which does not have live view.
For the lens I am using, I would need a 67mm mask which I understand can just clip on to one of my filters?

[raymo]

I'm guessing that using a Bahtinov mask without "Live View" would be very
difficult, as the star would be so small. You normally magnify the star 5 or
10 times when using the mask. I expect somebody has tried, and will give you a definitive answer.
raymo

[Luke.]

I was thinking to take the exposure and then zoom in on the image to check the focus.

[raymo]

You can do that, but be prepared to do it a number of times before you get
it right. The focus movements are so minuscule that
you could hunt backwards and forwards either side of focus many times before chancing upon good focus. The longer the lens is, the easier it is
to use that method. Much easier with a 500mm lens than a 50mm one.
raymo

[Luke.]

This will be for a 300mm lens.
It is taking a number of times to get it close but I was wondering if the mask would be more accurate in the end.
A camera with live view will be my next purchase but not for a while.

[raymo]

I don't think you'd even be able to see what you are supposed to be doing
with a mask at that small an image scale. You could probably find a used DSLR with live view,body only, for around $250 on ebay, sell yours, and
you're not too far out of pocket. You'd probably get a Canon 450D body
around that price; good camera.
raymo

[poider (Peter)]

can i use a template for a bahtinov mask without having to cut out plastic etc, could just cut the template and use that?
Peter

[Luke.]

Originally Posted by raymo

I don't think you'd even be able to see what you are supposed to be doing
with a mask at that small an image scale. You could probably find a used DSLR with live view,body only, for around $250 on ebay, sell yours, and
you're not too far out of pocket. You'd probably get a Canon 450D body
around that price; good camera.
raymo

Yup I am putting some money away for a Nikon 5300/5500. Not interested in Canon.
I will sell off my old camera body and one or two lenses I don't use anymore which should make back half of the cost.

I won't bother with the mask for now as it seems I won't have much use for it. I am not in any rush to upgrade my equipment as I can still learn with what I have now.

Thanks all!

[AstroJunk (Jonathan)]

Are you planning to use a standard camera lens Luke? If so, do on auto focus On a cloud or similarly distant object during day time and find the exact focus point of the camera. Remember it or turn it to manual focus so that you don't lose the position and use it at night

I wasted too much time trying to get a focus at night with my DSLR before I realised this!

[Luke.]

Yes just a standard lens. It's fairly clear tonight so I will give the auto focus a try. Thanks for the tip.

[AstroJunk (Jonathan)]

This is a 4 min 105mm shot - My camera actually focusses before the infinity stop. Came as quite a surprise!

[raymo]

Almost all DSLRs can go past the infinity symbol. It would be so simple if they didn't. The problem with Jonathan's method is that
during an evening imaging session focus can need to be adjusted, or a knock of the camera and focus is lost.
raymo

[peter_4059 (Peter)]

I've used a small bahtinov mask with my 400D stock lens - works a treat.