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  #121  
Old 22-07-2018, 09:39 AM
Stefan Buda
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The mounting pads that will hold the back plate are done. Because the back plate will not be adjustable, like on the ODK10, I can use 4 mounting points, for extra rigidity.
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  #122  
Old 26-07-2018, 08:07 AM
Stefan Buda
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The front end is nearly complete. Apart from the secondary mirror, the only thing missing is the PCB that will collect all the wiring. With the help of my son, a professional quality Gerber file has been produced and will be sent for manufacturing.
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  #123  
Old 26-07-2018, 08:26 AM
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Atmos (Colin)
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This is all coming together beautifully
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  #124  
Old 26-07-2018, 08:49 AM
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Awesome!
How are the optics going?
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  #125  
Old 27-07-2018, 11:38 AM
Stefan Buda
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Quote:
Originally Posted by Lognic04 View Post
Awesome!
How are the optics going?
I'm fine grinding the corrector lenses at the moment.

The back plate took two setups on the mill and two on the lathe, with about 14 hours work, but I'm very happy with the precision I achieved.

I won't be providing any more updates until early September, as I'm about to go away to wormer places until the end of August - missing half of the great Mars opposition.
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  #126  
Old 27-07-2018, 03:43 PM
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I just cannot believe how perfect this is working out! No, I take that back - after receiving some custom bits from Stefan, I CAN believe it.

If only I could afford a bespoke scope like this without my wife surgically removing what I cherish so much
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  #127  
Old 28-07-2018, 07:20 AM
sharpiel
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If only I could afford a bespoke scope like this without my wife surgically removing what I cherish so much
Your Tak?
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  #128  
Old 28-07-2018, 07:28 AM
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multiweb (Marc)
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This is nearing completion now. Will you flock the inner tube?
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  #129  
Old 28-07-2018, 12:59 PM
Stefan Buda
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Quote:
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If only I could afford a bespoke scope like this without my wife surgically removing what I cherish so much
If I turn this thing into a commercial product, perhaps I should offer, as an optional extra, some form of protection gear for men in your predicament.

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This is nearing completion now. Will you flock the inner tube?
Yes, I intend to use self adhesive synthetic velvet, if I can obtain some, as my old supply is running low.
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  #130  
Old 28-07-2018, 03:57 PM
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Your Tak?
Touche Les
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  #131  
Old 29-07-2018, 11:31 AM
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Stefan, such a work of art. Beautiful!
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  #132  
Old 03-10-2018, 03:57 PM
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Time to revive this thread. I've been back for a full month now, but so much work has piled up while I was away, that I haven't been able to make much progress until now.


The only progress worth mentioning is that I managed to keep one of my small polishing machines going in the evenings and I finished polishing a small batch of corrector lenses. Last year when I tried to get a couple of lenses BBAR coated, the cost turned out to be prohibitive, so this time I'm trying to bring the unit cost down by getting more lenses coated.
The small silicone mould for casting polishing laps worked very well.

The day before I left for my trip, my son sent off the GERBER file of the small PCB, that will live inside the secondary hub, to China for manufacturing. About ten days later my son emailed me that the finished PCBs have arrived. I was stunned.
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  #133  
Old 05-10-2018, 04:17 AM
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Nice!
Can you show us your grinding/polishing machines?
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  #134  
Old 13-10-2018, 09:48 AM
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Not very spectacular but very important progress over the last week:
I dug up the old test plate for the 16" Dall-Kirkham secondary mirror, with the associated tools, and reground it into a test plate for the CDK250 secondary.
I had to change the RC from 950 to 1110, which didn't take long. After the manual grinding I did about 4hrs of machine polishing followed by manual figuring. When the Ronchi lines were looking quite good, I set up the Bath interferometer to find a Strehl of about .8 Further figuring/testing got the Strehl ratio to .939 at which point I called it done.

Also I sent off a bunch of corrector lenses to Longman Optical to have them broad band AR coated. Fingers crossed.

The second picture is for Logan.
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  #135  
Old 13-10-2018, 10:13 AM
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Cool! Thanks for the pic.
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  #136  
Old 24-10-2018, 02:51 PM
Stefan Buda
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Good Progress: I made two secondary mirrors, a second Back Plate and Dovetail plate.
I had bought three 120 diameter blanks, so I turned one into a grinding tool and used the rest to make two identical secondary mirrors. Looks quite certain that I will make more than one of these instruments and, in order to bring down the anodising cost, I also duplicated the Back Plate and Dovetail Plate.

Never stops amazing me how long it takes to get an optical surface from about 1/4 lambda to something like 1/10 lambda (on the wave front). The damn law of diminishing returns really tests one's patience.
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  #137  
Old 24-10-2018, 03:18 PM
Imme (Jon)
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Quote:
Originally Posted by Stefan Buda View Post

Never stops amazing me how long it takes to get an optical surface from about 1/4 lambda to something like 1/10 lambda (on the wave front). The damn law of diminishing returns really tests one's patience.
Looks great....what kind of time are you talking to go 1/4 to 1/10?
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  #138  
Old 24-10-2018, 04:00 PM
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Excellent work Stefan, great to see this project slowly coming together.
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  #139  
Old 24-10-2018, 04:17 PM
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Wow, you seem to be very fast at this process?!
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  #140  
Old 24-10-2018, 04:25 PM
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Quote:
Originally Posted by Stefan Buda View Post
Good Progress: I made two secondary mirrors, a second Back Plate and Dovetail plate.
I had bought three 120 diameter blanks, so I turned one into a grinding tool and used the rest to make two identical secondary mirrors. Looks quite certain that I will make more than one of these instruments and, in order to bring down the anodising cost, I also duplicated the Back Plate and Dovetail Plate.

Never stops amazing me how long it takes to get an optical surface from about 1/4 lambda to something like 1/10 lambda (on the wave front). The damn law of diminishing returns really tests one's patience.
Hi Stefan, what are we looking at? Parallel lines? Can you make the difference between 1/4 and 1/10 just looking at the patterns?
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