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80mm long focal length refractor

savarin

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I took very fine cuts so as not to over stress the tool bit.
Sanding with differing grades of wet and dry soaked with WD40.
Down through the grits starting at 240, 800, 1200.
Then tripoli on a sisal or hard denim buff depending on how deep the remaining scratches are then white rouge/alluminium polish on a soft cloth buff.
It takes way too much time and I am totally over it:headache: the trouble is once you polish one item all the others have to be done else it looks terrible.
 

savarin

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I have decided three bolts on the plate and one bolt and one peg on the boss.
Drilled and tapped one bracket and the plate so far.
I will make a short pointed peg to mark the boss for that hole and a 2mm point to mark for the bolt threaded hole.
It hurts when you want to get going but other things encroach on your time preventing you from ploughing ahead.
 

savarin

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A small pointed rod to find the spot for the hole
azimuth-plate-brackets1.jpg

replaced with a peg once the boss has been drilled
azimuth-plate-brackets2.jpg
but look at all those scratches I now have to polish back out.
 

savarin

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Brackets installed along with a forked front tube support.
az-plate-brackets.jpg
First tests appear to have solved the flexure in the plate.
Next I wanted a pair of three hole brackets so I can fix a carry handle between the,
The first set I made from some 10mm scraps and rounded the ends in the lathe by bolting them to a long handle, pivoting off a 6mm rod in the tool post so I could control the rounding process.
Its looks as dangerous as hell but its only aluminium and by only taking small cuts it was extremely controllable, way easier than I expected.
tri-bracket-1.jpg
And produced this, nicely rounded off.
tri-bracket-2.jpg
However the 10mm brackets looked so out of proportion I went back and redid them again in 6mm scrap.
Then I bolted the pair to the wonderfull vertical slide and milled out the sides to reduce the amount of filing required.
tri-bracket-3.jpg
Not brilliant but way less filing required.
tri-bracket-4.jpg
and ended up with these.
tri-bracket-5.jpg
Being scrap they need a heap of sanding on the faces before ---- yep! you guessed it, more polishing.
 

rwm

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Brilliant work with your new slide. That fixturing plate with holes is a great idea. I need to do that.
Robert
 

savarin

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Got the handle brackets polished
handle-brackets.jpg

Used a chunk of cast to make a screwed cap
finder-cap.jpg

To fit the finder scope
finder-cap-2.jpg
I did polish it but there are some shrink marks in the centre so I think its going to end up black.

Started on the handle by knurling the centre, this will bolt onto the two brackets above
handle-1.jpg
Now I need to move the tail stock over to turn the two ends in a taper. I've never done this before so it will be a bit of a learning experience.
 

savarin

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This went easier than I thought it would, a pleasant surprise.
handle-2.jpg

Just have to drill some holes to fit it here.
. handle-3.jpg

This thing looks more complicated every day, I wonder if I will ever finish it?:laughing:
 

savarin

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More bits.
I made a brass shield to go round the azimuth gear. It looked great.
BUT! I,D.10T moment, the telescope couldnt be removed from the support structure. :bang head:
Oh well, back to the drawing board and design one thats easily removable with captured screws so they wont be lost when dropped in the dark.
I came up with this, some 12mm plate with a section milled out (sorry, no pics) with one end rounded the same way I did the auxiliary holders. (A bit scary but doable)
Then mounted to a wooden backing plate bolted to the face plate.
The centre cut out then a flange cut.
A bit of filing to clean up and test fit.

gear-shield-1.jpg

looks ok, the brass sheet will be fixed to the rounded part reaching down to the milled out section.
Just looking at it now I think if the holes the two knurled screws go through were elongated vertically it would allow the shield to tilt away from the gear allowing the scope to clear the shield.
We will see.
gear-shield-2.jpg
 

savarin

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Now working on the azimuth control.
I squared up a block of aluminium to hold a shaft with two bearings for an extension rod that links the flexible knob/shaft to the azimuth worm drive.
I was just going to drill through its length and counterbore for the bearings but the first drill bit snapped when it was almost through.
Hmm, no more ally to start again so I had a re think and re designed the block as shown in the drawing below in the hope a wood working solid carbide router bit would cut through the embedded drill bit and I could drive it out the remaining bits.
Heres the new design with the block and embedded drill bit.
azimuth-bearing-block3.jpg

Lets start milling and see
azimuth-bearing-block1.jpg

and finally, Yay! it worked
azimuth-bearing-block2.jpg
The angle milled to the face that has the bolt holes is so the shaft can angle out a bit for more clearance between it and the altitude control.
Have to counter bore the ends for the two bearings.
And of course more sanding and polishing.
 

brino

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Hey Savarin,

Thanks for sharing even your little mistakes. Because this is not an uncommon occurrence in my shop:(, I wanted to take the opportunity to pick your brain about it.......

Was it a HSS drill bit?
If the drill was mostly thru, could you have started from the other end of the part and drilled thru and punched out the broken drill bit?
How did the milling cut go when you made it as far as the imbedded drill bit?
Did you mill clean thru the broken bit, or just open up a space to pull it out partially intact?
Also, why choose this method over EDM? was it strictly about the small diameter broken bit and access thru the recess?

Thanks!
-brino
 

savarin

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Hey Savarin,

Thanks for sharing even your little mistakes. Because this is not an uncommon occurrence in my shop:(, I wanted to take the opportunity to pick your brain about it.......

Was it a HSS drill bit?
yes

If the drill was mostly thru, could you have started from the other end of the part and drilled thru and punched out the broken drill bit?
Hmm, never thought of that, what a dick. It was approx 1.5" in and I was unsure if it had wandered

How did the milling cut go when you made it as far as the imbedded drill bit?
I went clean through in the vertical direction, it made a fair bit of screeching as I went through but didnt seem to be a problem.
Then I milled along the the bit from the top not quite touching it then milled horizontally into it not quite touching it. This allowed me to pick it out and l drove the remaining bit into the gap.
Then some cleaning up but no dro fitted (dont have one so not perfect.)

Also, why choose this method over EDM? was it strictly about the small diameter broken bit and access thru the recess?
It was too thin and too deep so would have taken days I reackon.

Thanks!
-brino
no worries mate.
 

Bill Gruby

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Charles, I have never seen anyone put the 9X20 lathe to work like you do. You are an inspiration to all. Kudos my friend.

"Billy G"
 

savarin

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Thats very nice of you Bill, thank you.
Continuing with the azimuth bearing block.
I had a bit of a hard time deciding how to clamp this for boring it out for the stainless roller bearings.
After a couple of attempts to mount it on the face plate and being unable to get it centered to my satisfaction I had another idea.
I turned a mandrel to the inner dia 7mm to a tight slip fit in the holes and mounted it between centres in the 4 jaw chuck.
To get sufficient clearance I had to use a 3 to 2 mt adapter and a 2mt centre, gently tightening the jaws in the hope it would stay centred.
Then removed the mandrel and tail stock out the way and bored the hole for the bearing.

azimuth-bearing-block4.jpg

And it fits. I flipped it around and did the same for the other end.
azimuth-bearing-block5.jpg
Now I just have to hope they are parallel and the 6mm shaft will fit in them smoothly.
I have a bit of a problem with the altitude control cover plate as shown above.
When tightening the friction knob your knuckles now hit the two knurled screws removing a bit of skin. Answer - make a longer friction knob, that means another bit of brass casting.
 

savarin

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The bearings work and the shaft fits nicely.
I had to use two universal joints to transfer the motion from the knob to the worm wheel.
altaz-controls2.jpg
but it rotates very smoothly. The new shield around the altitude gear is now aluminium as I had no brass wide enough.
Heres an overview of the how the controls hang.

altaz-controls1.jpg
I've made a new stainless washer to reduce the backlash in the azimuth clutch and that seems to be a lot better.
Now waiting for a short length of 100mm dia aluminium tube to make the dew shield.
Unlike a standard GEM mount the controls stay in the one place and never foul each other.
 

savarin

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Whilst waiting for the 100mm dia tube I thought I may as well start on the fitting.
I turned a bit of 12mm plate to approx size and bored out the middle.
Bored this to the loose slip fit to the lens cell, then ground a grooving cutter and cut two "O" ring grooves, I did this with the lathe in reverse so it was easier to see paying a lot of attention to the screw on chuck to ensure it didnt un screw.
lens-hood-1.jpg

They fit just right with only a tiny bit proud
lens-hood-2.jpg

This is now a fairly tight push fit to the front of the lens cell
lens-hood-3.jpg
Now this ring has to be turned down to fit the inside dia of the 100mm tube, when ever that arrives.
 
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savarin

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turned the ring to a tight fit inside the tube and used high strength bearing lock to hold it in place.
Centered in the 4 jaw and cut a thread inside to act as an antireflection surface once coated in matt black.
Centering was a long job, every tiny adjustment of a jaw flexed it and sent the other three out of wack, it took forever but I got there.
Yes, thats a huge overhang and I was unsure if it would actually work but it did with no problems.
I really must make a carriage stop but the clamp worked perfectly.
dewshield-1.jpg

I then turned down two mandrels for each end so I could clean them up and sand and polish the tube.
This shot is after using 800 grit followed by 1200 grit
dewshield-2.jpg

Then it was of course polished.
dewshield-3.jpg

Mounted in place
dewshield-4.jpg
Very rigid, no chance of falling off or being knocked off.
Six more jobs left:-
1 make a solar filter holder (easy)
2 make a new end cap to fit in the dew shield (easy)
3 cut the central pier into two for ease of transport (easy)
4 cast a joiner for them (bit harder)
5 dismantle and re clean/polish everything (arghhhh)
6 powder coat all the black parts. (not my problem)
That should be the lot, I hope.
 

ch2co

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Savarin
As usual good lookin' stuff. How do you plan to keep the polished finished polished and avoid scratches, oxidation etc?
I have always had most of my tubes powder coated with the exception of smaller stuff like finders, laser mounts etc.
The last two tubes that I made were a lens shade for my 105mm f15 and a main tube for a little 80mm f9.5. both those
tubes like most of my tubes are cheap welded irrigation tubing that always has a main seam that isn't very round.
I ground the seam mostly flat conforming to the rounded surface of the tube, then I turned
both these tubes on my lathe just like you did, but had a lot more oxidation. One tube was too long for my little lathe
and I had to improvise a bearing that pressed against the fully retracted and almost falling off the end of the lathe tail stock.
I tried to put a brushed finish on them, but it came out looking all wrong. Then I had the idea to use my angle grinder with a Scotch bright disk while the tubes were turning
slowly on the lathe for a finish that hides all the old scratches not already removed as well as the unevenness of the area around
the ground down weld. I am very pleased with the results and have gotten a lot of good comments on this finish from fellow
astronuts. So far after almost a year, this finish doesn't show scratches or oxidation that I have run into in the past.
Here's a couple of shots of it.
IMG_7191.jpg IMG_7200.jpg IMG_7647.jpg IMG_7649.jpg
 

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savarin

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Savarin
As usual good lookin' stuff. How do you plan to keep the polished finished polished and avoid scratches, oxidation etc?
I've used an ultra clear lacquer for all the brass bits but am not worrying about the aluminium. I think the lacquer will get scratched eventually and have to be redone.
I'm hoping the dulling will occur slowly and I wont notice it until it really needs a clean up:laughing:

Nice scopes, is the gem mount tracking? It looks a good one.
 

ch2co

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The mount started out life as non goto, but with tracking. I totally tore it down and cleaned and rebuilt it with new bearings and proper new grease, quite unlike
the black tar that the chinese decided it should have. I added to stepper motors and an off the shelf computer control board that turned it into a goto.
I can control it from my iPhone or computer over a wireless interface. Very convenient. I'm still working on the tripod to make it more stable and easier to set up.
All my polished aluminum tends to get dull in a very splotchy sort of way. I'm always getting my hands covered with various foods during long nights under the stars
and going gulp my scopes. My next telescope attempt will be a 10" f4.5 Surrier-truss tube reflector that can be used either in a Dobsonian
base or attached to the mount mentioned above.
Do you guys have astronomical gatherings down under? You're welcome to come join us at the next big one close to home.

CHuck the grumpy old guy
 

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savarin

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Most cities have a club, I'm in our local astronomy group but the only idiot who builds scopes.
It seems to be a lost art in most places. Quite a few do it down south, say 5 or 6, there must be more because we have a large supplier catering to the market.
I've just found out that Skeye for my samsung tablet has the ability to align and turn the scope to a push to with planetarium.
I cant wait to try that out.
Very cloudy at night these days so that must mean the scope is ready to test.
 

ch2co

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Even down under? I thought that you guys were different somehow.
I belong to the Denver Astronomical Society. We are a group about 400+ strong and do a LOT of astronomical outreach at schools, civic groups, libraries, etc.
We are almost 118 years old (although I'm a bit younger) and have a home base at the University of Denver Historic 1894 Chamberlin Observatory. We
offer two public nights with lectures tours and views through "our" little 20" 1894 Alvin Clark / Saegmuler telescope each week and one Open House with
the observatory open to the public and members set up 20 -60+ personal telescopes on the south lawn all looking up through Denver's light polluted skies.
We have many amateur telescope makers some of whom are vastly superior to anything I can turn out.
Here's a peek of our scope.

IMG_8251.jpg 2 cham16.jpg 1 Astronomer Aiden Kai Miller.jpg CH2 Solar.jpg
 

savarin

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This time of the year up here is supposed to be the wet season so its usually cloudless days but rainy nights.
We are getting the clouds at night but no rain.
Now that is a think of beauty.
We are a small club and before we became an official real club with all the resulting rules and regs we did a lot of schools outreach.
I presented a lot of them and it was all no charge.
Now we are official the club charges for those sessions which I dislike immensely so am no longer involved and we dont do very many now.
we still do public viewing on our light polluted beach front once a week and only ask for a gold coin donation. Its very popular but the objects are few, a couple of planets, the moon and thats about it.
Our dark site is approx 20 mins out of town and is very good with just a hint of orange glow behind the hills.
 

savarin

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Now the larger dew shield is on it needs a larger cap.
The resistance of the "O" ring is sufficient to hold it in place firmly.
dew-shield-cap-1.jpg
dew-shield-cap-2.jpg
 

12bolts

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Looking good Charles, I must pick a good night to come down for a visit.

Cheers Phil
 

savarin

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sounds a winner, wait till its powder coated as its in bits at the moment.
 

12bolts

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Are you coming to Tyto this weekend Charles? And will this be centre stage if you do :encourage:
 

12bolts

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It was in our local rag today. Townsville astronomy club is coming to Ingham to show all us country hicks how to look at the cheese in the moon and stuff :p Sorry cant find the link for that online
Tyto is the local information centre and wetlands. https://www.tyto.com.au/
 
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