Author Topic: Giant binocular  (Read 33366 times)

34_40

Re: Giant binocular
« Reply #135 on: August 22, 2022, 07:11:14 AM »
quite the collection of linkage.  What are the functions?  I'm assuming some sort of zoom perhaps?
Clausing 108, Clausing 8520, Atlas Horizontal, Lincoln stick and mig welders

savarin

Re: Giant binocular
« Reply #136 on: August 22, 2022, 08:36:51 AM »
A brief description of what has to happen with astronomical telescopes.
The parabolic mirror reflects the light travelling down the scope back up to a secondary flat mirror that reflects that light out the side usually into an eyepiece where it is focussed.
All the mirrors have adjusters, the primary mirror has three adjusting screws that tilt the mirror to make the light cone hit the secondary at the right spot to be reflected out into the eyepiece.
These adjusters are usually at the bottom of the scope underneath the mirror cell.
Once adjusted correctly they usually only need a tiny tweak now and again.
This is called collimating the mirror.
In a binocular each tube then has to be adjusted to bring both the images into call it co-collimation so your eyes can successfully merge the two images into one.
 If this co-collimation is a bit out your brain takes over and merges them for you BUT in the process giving you the most thunderous headache ever.
All these rods will allow me to tweak the co-collimation whilst looking through the eyepieces to ensure the images do allign perfectly. (I hope)
The first one as pictured is actually to move the complete mirror cell sideways as another aid in merging the images.
One mirror will move at 90' to the other mirror.
I hope this makes some sort of sense.

34_40

Re: Giant binocular
« Reply #137 on: August 22, 2022, 07:42:49 PM »
makes a lot of sense now! never knew there was so many things going on in there. And I can imagine the headache.. every couple years I get new eyeglasses so I've experienced that pain.  Thanks for the info.
Clausing 108, Clausing 8520, Atlas Horizontal, Lincoln stick and mig welders

savarin

Re: Giant binocular
« Reply #138 on: July 15, 2023, 06:38:03 AM »
I have been doing bit, honest, but life has the habit of getting in the way.
Both mirror cells are finished, the mirrors will sit of the ring of soft rubber, a rubber disk will be glued to the back of the mirror with an aluminium disk glued to that. 
The mirror backs will be ground to a convex radius of curvature of 142.5", the aluminium disks ground to a concave roc of 142.5" as well, the middle of the ally disk has a 10mm bolt pulling the mirror down onto the rubber border distorting it from a spherical roc to a parabolic shape.
The front concave curve of the mirrors need a radius of curvature (roc) of 144", this will be ground in roughly with the abomination of a machine shown below.
 The pendulum carries a spinning diamond disk at its end.
I used a diamond cutting disk with WD40 to hollow out the aluminium disks but was very surprised at how long it took.
 (And the mess)
 To set it up I set the pendulum at 122.5" from the centre of the top pivot to the edge of the diamond blade.
 I then adjust the three tripod legs so the diamond disk "just" kisses the edge of the aluminium disk all around.
 Then raise the legs equally till the diamond disk touches about an inch from the centre and start grinding, the aluminium disk rotates anti clockwise pretty fast and the diamond dish rotates clockwise so it cuts against the direction of the main turntable. Lower the pendulum a little and off again, rinse and repeat.
 The arrow is to remind me, if I get the direction wrong the diamond disk rides up onto the aluminium disk too fast to control. No big deal but if it happens on the glass mirrors they have a habit of cracking. (dont ask me how I know)
The large disk with all the steel dumps epoxied to it is the main tool to grind the mirror backs at 142.5" roc. This has to be kiss ground at 122.5" roc to just clean it up.
Another tool has to be cast in this to use on the aluminium disks to get them tidied up to 142.5" roc. 
The two glass disks were ground out at 144" roc with the diamond disk blade and plenty of water to keep the glass dust down.
They ground down about an hour each but one of the disks chipped on the edge. I'm hoping a good chamfer will solve the problem but if not I have enough glass to cut another one.
« Last Edit: July 15, 2023, 06:41:05 AM by savarin »

34_40

Re: Giant binocular
« Reply #139 on: July 15, 2023, 09:08:26 AM »
UM..... WOW!  :c029: :bravo_2:
Clausing 108, Clausing 8520, Atlas Horizontal, Lincoln stick and mig welders

Jake Parker

Re: Giant binocular
« Reply #140 on: July 17, 2023, 07:03:21 AM »
I like that grinder pendulum set up bud!

savarin

Re: Giant binocular
« Reply #141 on: July 17, 2023, 09:44:49 AM »
Thanks but I wish I had thought of using a cheap angle grinder on the end instead of the slow spin dryer motor, it would have been easier and lighter to swing. Also the faster speed of the angle grinder would have produced a smoother surface.. Still, it did get the job done.

savarin

Re: Giant binocular
« Reply #142 on: October 27, 2023, 11:13:07 PM »
Grinding the steel tools is taking a lot longer than I expected.
 The bottom tool is formed concave to grind the mirror backs, the top tool which will end up at the same curvature except convex to grind the aluminium puller disks.
 Heres a video showing the grinding process with 80* grit, the top tool is free wheeling, it just overlaps the bottom disk/tool. This causes the tool to spin faster in the centre of the bottom tool and slower at the edge thus deepening the curve.
 I have approximately 2/100ths mm to go in the centre.
https://youtu.be/4Z62BnRnaJc
Why am I building a giant binocular?
 Because these are the largest I have (25x100) and I need-want-desire-hope for- greater magnification.
I built these so at public sessions I could find the object then lower or raise the height to fit anyone else looking through them.

savarin

Re: Giant binocular
« Reply #143 on: October 27, 2023, 11:24:27 PM »
Heres the back side of the mirror ground to 400 grit with an even curve and no zones to the best of my measuring ability.
 its very smooth but I stopped at 400 so there is a bit of a key left for the glue to bond.
the jig with the 400 diamond lapidary disk smoothing the edge and getting the mirror rounder.
 Its sprung loaded so keep grinding till the diamond disk stops pulsating in and out. Always assuming I have the glass centered.
The glass is held in place under tension from that central bolt pressing downwards.
 I will have to make a 45' bracket to hold the diamond disk at that angle to cut the edge chamfer.
 If you look close at the join between the steel disk and the glass you will notice a large chip out.
This happened when the vertical pendulum grinder ran away from me a hit the edge. 
I'm hoping I will be able to remove most of it when I chamfer the edge, if not and it screws up the figure I have a heap of 19mm glass to cut another from.
 Still so much to do.

savarin

Re: Giant binocular
« Reply #144 on: October 27, 2023, 11:36:09 PM »
Couple of short noisy vids showing the grinding.
 I dont know why it published them as shorts though. (Maybe because they are--------------short?) 
Grinding the mirror back convex with a heap of lead weight
https://youtu.be/a4M5TlZ4ldc
grinding the mirror edge smooth at 90 degrees
https://youtu.be/JGmQmMbEoTk
grinding the edge bevel at 45 degrees
https://youtu.be/U7m32XYPSEk
The mirrors are not quite centered on the turntable so the pulsing of the diamond disk is quite pronounced.
 Both mirrors now have their back face bevels done.
For the 90' I let the diamond disk free wheel but for the bevels it took way too long so I drove the disk with my drill, mirror moving clockwise and diamond disk anti-clockwise. 5 mins to do each mirror, took way longer than that just to set them up.
BUT, it was way messy with glass dust and water splashing everywhere that I didnt really notice till it dried.

savarin

Re: Giant binocular
« Reply #145 on: November 24, 2023, 07:05:39 AM »
Due  to the curved back I have to set the mirror in plaster so it can sit flat on the turntable.
This also allowed me to bevel the edge.
(bevel 2)
the glass tile fine grinding tool is glass mosaic tiles about 1/4" thick. It was cast in the hollow of the mirror so hopefully its not far off the desired radius of curvature.
(Glass tile tool)
I've sealed the plaster so I doesnt soak up water (I hope) at least not too much.
This is where the numbskull component kicks in.
I kept reading the spherometer the wrong way and thought I was flattening the curve, instead, I was deepening the curve. Doh!  :38:
Eventually I twigged and started reading the correct way  ie this is 0.0221
(sphero 1)
I need to get to 0.0179, currently I'm at 0.0188 so hopefully soon.

savarin

Re: Giant binocular
« Reply #146 on: November 24, 2023, 08:08:35 AM »
I should of added that it was zeroed on a flat   at 1 on the small dial and 0 on the large dial.
As the probe had to extend into the curve of the glass it extended more thus reading backwards.