Revolutionary new way of focusing! No less!
Posted 29 July 2008 - 10:27 PM
I like this focusing mask thanks for the links and info. I'll try to make one like you've pictured, but first I may use the diffraction angles you've given on a mask like this...LINK
I've been experimenting with the three holed Hartman mask and I think breaking up the symmetry with diffraction spikes like you've described will make it more useful.
Posted 30 July 2008 - 12:41 AM
The main advantage of the mask proposed by Pavel is that you see very clearly where are you right now (before focal point, after it) and there two diffraction spikes give nice and easy reference to compare to. The mask at your link provides no such "reference" lines. The picture just gets messy when not in focus. But one thing for sure it's much easier to make and to try.
Posted 30 July 2008 - 05:57 AM
I understand your point, I'll give it a try. I see the key to this is to have two elements that are complementary and a third that contrasts Like here ... MASK
And as your pictures show, the ability to gauge in and out focus is enhanced by the diffraction spikes. I've experienced some frustration using just the three circle mask so I'm eager to try this novel design.
Posted 31 July 2008 - 04:16 PM
Thanks for passing on the design.
Posted 31 July 2008 - 04:34 PM
Posted 31 July 2008 - 04:34 PM
Posted 31 July 2008 - 05:04 PM
John- I do have some nice machine tools and engineering software. I'll have to cut Dennis and Pavel in on the action. Couldn't you just see the look on Pavels face when big royalty checks start rolling in?
I do think I have an understanding of how the design works, and why you can't just scale it for other size scopes.
The axis is centered for the "left" side and has a precise light block of 50%. The "right" side has a 20 degree angle that is centered to blocked area of the left. The right side has a light block of 40%. The axis of the right open area must align to the center of the left blocked area. If it centered, then the spikes you see when in focus will align correctly.
I don't read Russian, so I had to look a photos and calculations that Pavel posted.
If this works like I think, then it will be simple for me to draw this design for any size scope.
Posted 31 July 2008 - 06:05 PM
Posted 31 July 2008 - 06:16 PM
Posted 01 August 2008 - 01:03 AM
Posted 01 August 2008 - 06:41 AM
i see now.
My lines are very straight.
Posted 01 August 2008 - 06:54 AM
Posted 01 August 2008 - 02:27 PM
Posted 02 August 2008 - 12:50 PM
This blows my hartman mask away.
Here is my test image going from in focus to out of focus in both directions.
This was only a very small movement with the focus knob
Posted 02 August 2008 - 12:53 PM
Posted 02 August 2008 - 01:05 PM
I plan on using them in the August Challenge in the beginner imaging thread.
Posted 02 August 2008 - 01:10 PM
How does this mask deal with seeing? Does the central line shift as seeing changes? That would be a terrific benefit of this mask if it's seeing independent.
Posted 02 August 2008 - 01:18 PM
Posted 02 August 2008 - 01:45 PM
here is a 60 second exposure of Jupiter. I was attempting to bring in the mag 15 moon Himalia. This was with a Meade DSI Pro. You can see the spikes off of the other moons are equal in all directions. i think the focus was dead on.
Posted 03 August 2008 - 06:51 AM
Posted 03 August 2008 - 08:34 AM
I drink ALOT of coffee....seems the plastic covers on the cans can be exacto'd easier than cardboard. Will give it a go
Posted 03 August 2008 - 09:23 AM
Posted 03 August 2008 - 11:03 AM