On the third link is a variant of Bahtinovmask with threads..
I was always wandering if I can build something similar to tennis racket (but with thread pattern that will produce diffraction spikes useable for focusing.
This guy was a bit faster than me...
The Mewlon has a 3 vane spider which effectively acts in a similar manner to the BahtinovMask when the OTA is pointed at bright stars.
The image generated by the 3 vane spider is not as clearly defined as the image generated by the BahtinovMask, especially on fainter stars, so focus is easier to establish and far more certain due to the multiple diffracting elements of the BahtinovMask.
For laymen such as myself, who wouldn’t know a Fast Fourier Transform if it hit them on the head, regardless of whether it was in the time or frequency domain, I find the diagrams and explanations both on IIS and CN very educational and fascinating to read about.
I was browsing the Bintel website and noticed that they now offer the BahtinovMask in a range of sizes from 14” down to 80mm, with some ‘scope specific sizes such as the C9.25.
Prices range from $25 – $59 and they look like the aluminium product from the Kendrick range, who also have a flexible plastic film range due out in Feb 2009.
Thanks Mike – I was interested in the 80mm thin, flexible plastic film model for my camera bag for the 400mm F5.6 but I only saw the alu models on the Bintel website.
The developer of the “Bahtinov Grabber” application (Niels Noordhoek) has now added an auto focus routine to his (free) software!
The Bahtinov Grabber application overlays a 3 line grid on top of the close-to-focus diffraction spikes and produces a directional indicator (+ or -) and a numerical read out of focus accuracy to assist with finding optimum focus. Link to post on CN.
Hi Dennis,
Were you able to download the focus control version - the link seems to be to the older version.
Peter
Hi Peter
I had planned to build an artificial star over the next couple of days and use it in the back garden with one of my OTA’s, so I can play with the auto focus application. So, although I have downloaded the application from the link, I haven’t unzipped/installed it yet.
I just unzipped the exe as I was writing this reply, and it shows a date of 23/05/2009 – is that what you get?
The chap from The Netherlands whose nom de plume on CN is “amateur” has posted a new link to the Bahtinov Grabber software and I think it is the auto focus version?
Not yet Peter – I’m currently investigating sources of flexure on my side by side set and killing them off one by one – nasty vermin they are! So, the few clear nights we’ve had have been given over to that project.
At the moment, manually focusing with the BahtinovMask gives me great results, but I will try the SW somewhere down the line. I’m thinking of the Canon 40D in Remote Live View Mode as a starting point.
I was browsing the Bintel website and noticed that they now offer the BahtinovMask in a range of sizes from 14” down to 80mm, with some ‘scope specific sizes such as the C9.25.
Prices range from $25 – $59 and they look like the aluminium product from the Kendrick range, who also have a flexible plastic film range due out in Feb 2009.
Cheers
Dennis
I bought the Kendrick 'flexible plastic ones" from BinTel for $29 for the 8". So far I have used it only for visual and a bit of experimental imaging, but I am amazed that it worked so well! I wonder why I even bothered to attempt to make my own for this price. Thanks Mr. Bahtoniv, I do hope you are getting some financial recognition from this?
Here is a 5 second exposure of Antares at ISO800 with the Canon 40D at the prime focus of the Mewlon 180 F12 (2160mm) with my BahtinovMask fitted. The image is an 800x600 crop from the centre of the frame. Seeing was estimated to be 5-6/10 for the session.
I bought a laser cutting/engraving machine for my business and can cut any vector or even raster graphic from acrylic or mdf panels. This includes these Bahtinov Masks. It will be very cheap if it's just cut from 3mm MDF in a round shape and you are ready to paint a mask yourself and find a solution for mounting a mask onto your scope. The maximum diameter I can cut is 11"(working area of my laser is 24x12") and let say for easy pricing it will be $1 for each inch of your scope aperture + real postage cost. Usually it's from 55c to $1.10.
I can also cut it from foam panels but have no idea how much they are.
I bought a laser cutting/engraving machine for my business and can cut any vector or even raster graphic from acrylic or mdf panels. This includes these Bahtinov Masks. It will be very cheap if it's just cut from 3mm MDF in a round shape and you are ready to paint a mask yourself and find a solution for mounting a mask onto your scope. The maximum diameter I can cut is 11"(working area of my laser is 24x12") and let say for easy pricing it will be $1 for each inch of your scope aperture + real postage cost. Usually it's from 55c to $1.10.
I can also cut it from foam panels but have no idea how much they are.
Can you cut foam, for example, round holes in a foam block for an eyepiece box?
