Problems with Y-mask

[stargazerlily]

Hi everyone,

Tonight I had a go with my home made Y-Mask on my 50mm Canon lens. The problem is that I couldn't generate any diffraction spikes from the mask when trying to focus on a star. When the lens was way out of focus I could see the Y shape itself in Live View. When I focused the other way, the Y shape disappeared then reappeared again but was inverted.

I've attached an image to show what it looks like on the camera. I made the support from thin plastic card and the actual Y shape from thin plastic strips. I used a template for the Y-shape from the web. To hold the mask in place, I used a Coken filter holder screwed into the end of the lens. The plastic support fitted into the rear-most slit of the Coken holder, the one for the flat lens guard.

Any ideas as to why the mask didn't (or couldn't) generate any spikes?

Many thanks

Pete

[butlermike]

It might be too close to the lens. From what I've seen the masks are used un the end of dew shields or lens covers rather than sitting that close to the lens. Try extending the distance somehow perhaps with a homemade lens cover out of card as a low cost way to try it.

[stargazerlily]

Thanks for the suggestion. I'll try again using an old lens hood instead of the Cokin holder.

Cheers

Pete

[Digz]

I would also try to increase the thickness of the 'strands' with your current setup, then try moving the mask further away.

I was thinking of a what would be best to attach a mask to my lenses and never considered my filter holder, however as butlermike has suggested this might be putting the mask too close to the lens.

[davew]

Try increasing the bar width by all means but the main problem is the focal length.

When using the mask and a wide lens, aim for the brightest star in the sky or part of sky you want to image in. Try and download the focus image to a laptop for the best chance of seeing the spikes.

I have found the spikes start to get more noticeable from about 100mm and up.

An alternative at the moment are the moons of Jupiter. If you can make them out then you've got to be close enough

Dave.