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[4]

80mm long focal length refractor

January Project of the Month [3]
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savarin

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news to me, we just did one at the museum here on sunday, about 80 people.
 

savarin

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Saturday night was first light for the scope.
A few things became apparent as the evening progressed.
This is not a scope for beginners.
The field of view is somewhat narrow meaning objects pass through the field rather faster than expected.
Being a manual telescope the slow motion controls are very important.
The clutch on the azimuth control is very good but the altitude left a bit to be desired as it slipped no matter how tight I screwed up the adjuster so I replaced the two plastic plates with aluminium.
This is most of the parts involved. The top plastic disk is replaced with the aluminium next to it and sits in the gear wheel, its then sandwiched between that disk and the bottom disk.

parts-1.jpg

alt-parts-2.jpg

alt-parts-3.jpg

Then the tabbed stainless washer is slid on.

alt-parts-4.jpg

Then the assembly is squeezed up with the brass nut and fancy cast pressure plate with all its inclusions.

alt-parts-5.jpg

Now it works, slack and the scope can be manually moved, tighten with the brass nut and the slo-mo control works.

alt-parts-6.jpg
 

ch2co

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Savarin

Long refractors are great scopes but..... They are long and have a narrow field of view which makes them great for planet and double star observations.
But just a tiny amount of movement makes the field of view move around a lot.
I remember the first time I set up my home brew 105mm f15 Jaegers scope (over 5.5 feet long) I was astonished at how careful I had to be to balance it
on its mount. At the time I had it mounted in a wooden box structure about a foot long that I could loosen up and slide back and forth on the scope which made it
easy to balance out on the mount. After finding the sweet point I tightened the box up and it rode easily in either a altitude-azimuth mount that had
very little friction. Balance was paramount or the scope would slowly try to move down on whichever end was heavier. Late I built a pair of aluminum
mounting saddles tied together on the bottom with a dovetail bar. I already had found a good balance point so it behaved easily on a small equatorial
mount that I had rescued and rebuilt. The first star party I went to was out in the middle of nowhere and my little scope handled wonderfully until
the wind began to blow and it became unusable due to it bouncing around to much. The mount wasn't sturdy enough to really handle a long scope like that.
Next swap meet I picked up a used MUCH heavier mount that I had to completely rebuild. The innards reminded me of a small automotive transmission.
The scope become a wonder to use, until I added a lens shade to the top end. Suddenly even the much beefier mount just
didn't track worth a darn. Balance was once again rearing its ugly head. After moving the scope back a little in the saddle all was well again.
I have finally installed a sliding weight bar along the rear section of the main tube which made it simple to rebalance the scope whenever
I add or take off an accessory piece like a large finder or tracking scope with camera attached, just by sliding the weight forward or backward
on the balance bar. Just a little front to back out of balance can make a huge difference in the operation of the clutches and drive train, and the
viewing.
Beautiful work you are doing. Far more artistic than any of my.

Chuck the grumpy old guy who is going to view the total eclipse of the Sun from along its centerline in about 3-1/2 days. (Clouds willing)
 

hman

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Saturday night was first light for the scope.
CONGRATULATIONS on your achievement!!!!

It's been absolutely wonderful reading your build description. You're a true artist in metal.
 

savarin

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Thank you John that really is appreciated.
Its been a bit of a struggle at times and I still have to powdercoat the pier and feet.
 

savarin

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I like the idea of the sliding weight Chuck I may just copy that.
 

savarin

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It is finished, no more to do, nada.
Awesome views of the moon but I couldnt blow up Saturn to a large size but it still looked good and the manual controls kept it in the eyepiece.
Well pleased with the whole thing.
the-scope-1.jpg the-scope-2.jpg
Now to start the binoculars
No rest for the wicked.
 

Downunder Bob

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G'day Charles, as always I'm constantly amazed by your inventiveness when it comes to makeing a workaround, not only do you make it work, it looks good as well.

Bob
 

rwm

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That is very sharp looking! Any chance you could post a pic or two to demonstrate the image quality? Can you take a cell phone pic thru a telescope?
Robert
 

savarin

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Thanks Bob and Robert.
I will attempt to get a shot through the scope but they have never been very good in the past.
At present its cloudy nights most nights so I dont know when.
Its mainly a lunar and planetary scope as its focal length is rather long.
 

ch2co

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Thanks Bob and Robert.
Its mainly a lunar and planetary scope as its focal length is rather long.
Hey, Savarin, don’t forget that these long refractors are great for double star observing, some of my favorite objects. With a long focal length eyepieces (my longest is 60mm) they are very good for a lot of deep sky objects. Besides show stoppers like Saturn and Jupiter and their myriads of constantly changing moons, the Orion Nebula is gorgeous and a real jaw dropper especially good for showing to the general public. Four of my favorite telescopes are long refractors.

CHuck the grumpy old guy

PS I just had a fight with the spell checker on my phone substituting “Savings” and then “Savage” when I typed your name.
 

Downunder Bob

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Finder scope finished and looking very nice.
However, I now have a cemented 50mm japanese doublet that may be a better objective but it needs the central tube to be another 15mm longer and a different lens cell. Maybe after its all finished.
View attachment 111494

At last I can start on the focusser unit.
I couldnt find any 60mm plate but did find some 100mm round.
Now came the hard part, I dont have a mill but need to convert this cylinder to a block.
It wont fit securely in the chuck.
I scribed the block size on the top of the cylinder, drilled the centre and mounted it on the compound in place of the tool post.
I used a rule to align the scribed line with the face of the chuck.
View attachment 111492
The only tool I could use that had sufficient off set happened to be the Eccentric Engineering diamond tool holder and this proved to be just right held at an angle in the 4 jaw.
View attachment 111490
about half way through here. as I got closer to the scribed line I just had to make a tiny re-alignment to bring it back to spot on.
View attachment 111491
Instead of doing the same thing to the other side I mounted it against the chuck jaws as there was just enough room and have started milling the other side. I'm hoping they will be parallel by doing it this way.
The first cuts seem to point this way.
View attachment 111493
G'day Charles, Brilliant6 work and as usual an amazing way of doing things. I see you're putting a Diamond tangential tool holder thru its paces. I've been wondering if they are worth it. but it looks like they are.
Bob.
 

savarin

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I think the Diamond tangential tool holders are well worth while I really like mine. Very simple to sharpen.
 
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