You didn't order any extra 80ED sized masks, did you?
If we mention your name to the laser cutting mob, do we get a 90% discount?
If I send them the 80ED file that you've created, they'll know what to do with it, aye?
Regards,
Humayun
as i said earlier i wont be handling peoples individual orders. you are most welcome to drop my name - might not mean much though. the file is all you need with it noted you only want the ed80 and the 127ed. remember to as for shipping to yourself
I finished my masks over the weekend too. I sprayed each one with a metallic primer followed by a coat of flat black. The C9.25 and Vixen have a closed cell foam collar fitted underneath, so that they sit on the C9.25 metal corrector plate cell (actually on top of the 6 screws on the cell) and the Vixen objective cell. Both can be fitted even when the dew shield is fitted on the OTA.
The Mewlon Mask just fits around the end of the OTA, held in place by a closed cell foam collar glued to the S/S mask – I used a contact adhesive for all cells and left them to outgas over the weekend just to get rid of any solvents. For the C9.25 and Vixen 102, I added a knob which allows me to grip the mask and lower it into the dew shield.
The larger masks are very rigid so good choice on the 1.2mm (1.5mm?) S/S.
All I need now are some clear skies to try them out!
I finished my masks over the weekend too. I sprayed each one with a metallic primer followed by a coat of flat black. The C9.25 and Vixen have a closed cell foam collar fitted underneath, so that they sit on the C9.25 metal corrector plate cell (actually on top of the 6 screws on the cell) and the Vixen objective cell. Both can be fitted even when the dew shield is fitted on the OTA.
The Mewlon Mask just fits around the end of the OTA, held in place by a closed cell foam collar glued to the S/S mask – I used a contact adhesive for all cells and left them to outgas over the weekend just to get rid of any solvents. For the C9.25 and Vixen 102, I added a knob which allows me to grip the mask and lower it into the dew shield.
The larger masks are very rigid so good choice on the 1.2mm (1.5mm?) S/S.
All I need now are some clear skies to try them out!
Cheers
Dennis
they look fantastic Dennis, I like the knobs - very sauve!!! I sprayed mine with flat black metal etching/primer top coat in the one go. i used SS hooks as the handles - you will see them this evening when I take a picture of them.
one thing I thought the mewlon was to fit on the inside and not like what was in the image you posted? Did i stuff up?
they look fantastic Dennis, I like the knobs - very sauve!!! I sprayed mine with flat black metal etching/primer top coat in the one go. i used SS hooks as the handles - you will see them this evening when I take a picture of them.
one thing I thought the mewlon was to fit on the inside and not like what was in the image you posted? Did i stuff up?
Hi Dave
No – you didn’t stuff up; in fact, you delivered on time, to budget, to specification and met the customer requirements fully. You also provided an added value service by generating the drawings for my set of masks as well as arranging all the procurement and shipping, so top marks to you my son!
The Mewlon mask was always intended to fit on the outside of the OTA, as unlike the C9.25 and Vixen 102, the Mewlon does not have a front end cell for the mask to rest on.
Great job guys looks great, and is it just me or do they look like Pacman. I wonder if that's how the inventor got the idea, maybe he likes the Pacman game.
I've been watching this thread with interest for a while and thinking this mask was a lot of mucking around to make but finally decided to give it a try.
I cut one out of some thick plastic last night - tried it out tonight and works better than I expected. The point of best focus was much easier to find than with the Hartmann mask.
Nice work Peter. The middle star looks the sharpest to me – is the sequence before focus – at focus – through focus or is it just my eyes!
Last night I noticed than when using the mask visually with my C9.25 and Pentax XW14 eyepiece, I could cause the central bar to “move” when I moved my eye around the eyepiece, so it does seem a very sensitive method of focusing.
I should have included a bit of explanation and the corresponding images either side of focus with the new design. The last three images are my attempt at either side and in focus with the Hartmann mask. I was using the same step size based on the focuspal motor focus controller, repeating the routine with each mask. I found it a lot more difficult to pick the sweet spot with the Hartmann mask as on the live screen the images look very similar for a few steps around the point of best focus. It is easier to pick the difference from these images when you see them side by side.
HI David ,
I am responding to your PM on the forum , as other members may have a similar question.
How effective is this mask for fast minor , grab and go scopes ?
Are the effects similar for visual observations or is this predominately an exercise for astrophotogphy?
My newton specs are
130mm aperture
f/5
focal length 650mm
45mm or 35% central obstruction by secondary mirror
I tried doing the the calculations but there was a term or two which threw me so I just guessed the data.
Can you help with the claculation.
given the limitation of this scope is there going to be a noticeable difference
I finally got a chance to test my aluminium framed fishing line version...
:thum bsup:
It works great!
No messing with changing exposure settings on the camera either.
I did notice that when the image was out of focus there are a mess of diffraction spikes... maybe that's something to do with some fitting errors or the fact that I mis-strung my mask (so the angled lines are not in the same plane as the horizontals).
One thing I did notice though, is that the diffraction spike don't work the way I expected... out off focus the intersection moves along the horizontal spike and doesn't coincide with the star image... this seems to be different to what the others are doing. I think it is because I changed the direction of the strings to make the mask more structurally sound... I didn't think it would change the way it works like that.
HI David ,
I am responding to your PM on the forum , as other members may have a similar question.
How effective is this mask for fast minor , grab and go scopes ?
Are the effects similar for visual observations or is this predominately an exercise for astrophotogphy?
My newton specs are
130mm aperture
f/5
focal length 650mm
45mm or 35% central obstruction by secondary mirror
I tried doing the the calculations but there was a term or two which threw me so I just guessed the data.
Can you help with the claculation.
given the limitation of this scope is there going to be a noticeable difference
i will have a look when i get to work on Monday - have left the file on m PC there
The guy (David Polivka) who designed and coded the “Bahtinov Mask Generator” has just released V 0.4. This (free) Generator is a web based application that generates a “Bahtinov Mask” pattern suitable for your OTA based on your input parameters.
From Dave's website:
Changes:
Version 0.4. 2008/10/18
Moved to new hosting provider.
Complete rewrite of mask generation code.
SVG opens fine in Corel Draw 12 (and, I think Corel Draw X4) now.
SVG now converts to DXF cleanly in Inkscape. You should be able to take the resulting .DXF directly to a machine shop/laser cutter/etc.
Split the existing generator page up into 4 pages (Overview, Generator, FAQ, and Change History) to make them more manageable.
Segregated parameter entry so it's not so overwhelming - broke it into Basic parameters, Advanced parameters, and Print options.
Entry validation added.
Appropriate parameters will accept numbers with decimal points.
Added an option to make the center of the left-hand side a bar instead of a slot.
Added an override for the slot width.
Added an option to scale the SVG to 72DPI for use with Adobe Illustrator.
Cleaned up the text a bit - now consistently use "slot" to mean an opening in the mask and "bar" to mean a solid bit.
Thanks once more to Pavel for his original design and to David for his superb implementation of the Generator and his on-going development and support. Here is the link to astrojargon, where the Generator is hosted.
Cheers
Dennis
PS – For Canon 40D owners Dave has also written an application that can interrogate the 40D and return the value of the number of shutter operations.
The guy (David Polivka) who designed and coded the “Bahtinov Mask Generator” has just released V 0.4. This (free) Generator is a web based application that generates a “Bahtinov Mask” pattern suitable for your OTA based on your input parameters.
From Dave's website:
Changes:
Version 0.4. 2008/10/18
Moved to new hosting provider.
Complete rewrite of mask generation code.
SVG opens fine in Corel Draw 12 (and, I think Corel Draw X4) now.
SVG now converts to DXF cleanly in Inkscape. You should be able to take the resulting .DXF directly to a machine shop/laser cutter/etc.
Split the existing generator page up into 4 pages (Overview, Generator, FAQ, and Change History) to make them more manageable.
Segregated parameter entry so it's not so overwhelming - broke it into Basic parameters, Advanced parameters, and Print options.
Entry validation added.
Appropriate parameters will accept numbers with decimal points.
Added an option to make the center of the left-hand side a bar instead of a slot.
Added an override for the slot width.
Added an option to scale the SVG to 72DPI for use with Adobe Illustrator.
Cleaned up the text a bit - now consistently use "slot" to mean an opening in the mask and "bar" to mean a solid bit.
Thanks once more to Pavel for his original design and to David for his superb implementation of the Generator and his on-going development and support. Here is the link to astrojargon, where the Generator is hosted.
Cheers
Dennis
PS – For Canon 40D owners Dave has also written an application that can interrogate the 40D and return the value of the number of shutter operations.
Dennis,
What program do I need to run the Generator
Ian C
Dennis,
What program do I need to run the Generator
Ian C
Hi Ian
The “Generator” is a web based application where, for the simple version, you enter the details of your telescope aperture and focal length, followed by how thick you want the outer ring to be.
The “Generator” will then produce a “bahtinov.svg” file which you then save to your PC. “svg” stands for Scalable Vector Graphics (SVG) which is an XML specification and file format for describing two-dimensional vector graphics.
A program called Inkscape (a free and open source vector graphics editor application) can open .svg files and I know that CorelDraw12 now opens the .svg files from the “Generator”.
I ran the generator and made up a template for my FS102 (820mm f/l, 102mm clear aperture and 150mm overall diameter). I then transferred it to a piece of thick-ish plastic card I have (left over from dewshields) and marked it out dot by dot. After cutting two slots and suffering stuffed knuckles with the pressure on the knife, I stopped. It's a crazy way to do it.
Question - is anyone making these at all now? Silly trying to get one from someone before Lostock - so I guess I'll attempt to borrow one up from some poor sap there (I'm coming for you h0ughy!!) and see how they work.
Anyways, just checking to see that someone either is or isn't producing any more....
I ran the generator and made up a template for my FS102 (820mm f/l, 102mm clear aperture and 150mm overall diameter). I then transferred it to a piece of thick-ish plastic card I have (left over from dewshields) and marked it out dot by dot. After cutting two slots and suffering stuffed knuckles with the pressure on the knife, I stopped. It's a crazy way to do it.
Question - is anyone making these at all now? Silly trying to get one from someone before Lostock - so I guess I'll attempt to borrow one up from some poor sap there (I'm coming for you h0ughy!!) and see how they work.
Anyways, just checking to see that someone either is or isn't producing any more....
I ran the generator and made up a template for my FS102 (820mm f/l, 102mm clear aperture and 150mm overall diameter). I then transferred it to a piece of thick-ish plastic card I have (left over from dewshields) and marked it out dot by dot. After cutting two slots and suffering stuffed knuckles with the pressure on the knife, I stopped. It's a crazy way to do it.
Question - is anyone making these at all now? Silly trying to get one from someone before Lostock - so I guess I'll attempt to borrow one up from some poor sap there (I'm coming for you h0ughy!!) and see how they work.
Anyways, just checking to see that someone either is or isn't producing any more....
contact the firm that did mine - you can open the file you produced and create a dxf file and send it to them - with express post maybe you can have it before you go
