Mine needs rather thin bars/inter-bar gaps... 5.5mm @ F/6.3 and 8mm @ F/10.
Plastic would probably be a better option that Aluminum, as the idea of putting some thing that heavy and solid next to the corrector plate scares me a little bit.
If some enterprising metal (or even plastics) fabricator has a laser cutter or similar, they could probably cut out aluminium (plastic) discs with the mask patterns at a reasonable price locally?
Maybe Ron at Sirius Optics, Underwood has some connections to local workshops?
Cheers
Dennis
i am getting a rough quote from a laser cutter from Victoria - will keep you posted. Dennis did you have a look at the rough calcs i did - are they correct assumptions or am i off my tree
David, the calcs in your excel sheet look good to me, although in the "formula" bar, its got D3/(150-200) - which in excel means D3 (focal length) divided by 150 minus 200) I simply removed the 150-200 part and experimented with values to give me fairly round numbers...
I have an idea. I’m going to design and build a low cost motorised version, with adjustable components, for on the fly customisation of bar/gap widths and angles.
Each bar will be controlled by its own stepper motor and angle adjuster so that I can adjust the bar width and gap, as well as the bar angle, to suit the ‘scope/sensor of choice on a per session basis.
There will be a hand controller so you can just punch in your ‘scope model and optical configuration and the mask will then self adjust. There will be the ability to store up to 100 Favourites in a custom library. It will be light weight and cost less than the Apollo Program!
David, the calcs in your excel sheet look good to me, although in the "formula" bar, its got D3/(150-200) - which in excel means D3 (focal length) divided by 150 minus 200) I simply removed the 150-200 part and experimented with values to give me fairly round numbers...
No, no, no…it is not 150 minus 200! Good pick up Alex.
The denominator is a range where you choose a value between 150 and 200 so that the bar width comes out as a reasonable number.
I have an idea. I’m going to design and build a low cost motorised version, with adjustable components, for on the fly customisation of bar/gap widths and angles.
Each bar will be controlled by its own stepper motor and angle adjuster so that I can adjust the bar width and gap, as well as the bar angle, to suit the ‘scope/sensor of choice on a per session basis.
There will be a hand controller so you can just punch in your ‘scope model and optical configuration and the mask will then self adjust. There will be the ability to store up to 100 Favourites in a custom library. It will be light weight and cost les than the Apollo Program!
Cheers
Dennis
the sad part is dennis - i was thinking about that and how it could be implimented - a separate mask is a lot easier
Have modified your file with my interpretation....
I notice the calculation is for bar/gap spacing combined. So presumably that is the critical measurement not the width of the bar or the width of the gap... soooooooooo... has anyone thought of modifying a cake rack to do this? A wire grid would maximise the light into the scope...
From what I see so far, Dennis' idea of the printed overhead transparency is the simplest and most cost effective method, especially for multiple F.L and it seems to work perfectly.
Have modified your file with my interpretation....
I notice the calculation is for bar/gap spacing combined. So presumably that is the critical measurement not the width of the bar or the width of the gap... soooooooooo... has anyone thought of modifying a cake rack to do this? A wire grid would maximise the light into the scope...
Just a thought...
Al.
thanks Al that fixes things up a bit (a lot really) -- happy baking
The C8 and the LX200R 10” would use the 13mm spacings while the vixen R200SS would use a 5mm spacing – the same for the 127ED. The ed80 would probably be a 10mm spacing
So you would need one mask per barlow setting.
But according to Dennis it does seem to work on his scope with a Barlow. So question is how sensitive is this to the change in FL?
I have an idea. I’m going to design and build a low cost motorised version, with adjustable components, for on the fly customisation of bar/gap widths and angles.
Each bar will be controlled by its own stepper motor and angle adjuster so that I can adjust the bar width and gap, as well as the bar angle, to suit the ‘scope/sensor of choice on a per session basis.
There will be a hand controller so you can just punch in your ‘scope model and optical configuration and the mask will then self adjust. There will be the ability to store up to 100 Favourites in a custom library. It will be light weight and cost less than the Apollo Program!
Cheers
Dennis
There's a simpler version, but would have no angle adjustment.
Use two of the same masks stacked one on the other, move one to the left(or right) and the spaces will close up.
Using this, the bar width would be adjustable, but their pitch wouldn't change, is that an issue?
Edit: actually, the more I think about it, the less it's gonna work. The spaces would be shifted off-centre as the bar width is adjusted.... unless.... both masks move simultaneously, one left and one right equal amounts... hmmm
After thinking a bit about the "modified cake rack" option, I now think I might try the "String Art" option....
Timber frame with nails at the appropriate places for the prototype and some cotton... (maybe use different colours so looks pretty hanging on the wall ). If it's a success, the real one would be a timber frame and fishing line through holes (just like stringing a racquet).
Turn that old photo frame into something useful...
Al.
EDIT: Hmm I'll have to think about that a bit more... I just realised my initial string art idea would just produce lots of diffraction spike and not aid focusing. But watch this space...
Last edited by sheeny; 09-09-2008 at 03:42 PM.
Reason: Thought about my suggestion! ;o)
A wire grid would maximise the light into the scope...
. But watch this space...
