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.
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.
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.
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.
Quote:
Originally Posted by multiweb
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.
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.
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.
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.
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?
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?