10392 replies to this topic

[clamchip]

I'll try your suggestion, sounds like a good plan.

The only thing I can think of is Towa put priority on straight-thru observing for baffle size and location, even

though it was made for export where everyone typically uses a prism. Japanese amateur's prefer straight-thru

observing and that's the way they built it, I'm guessing.

 

Robert

Edited by clamchip, 04 February 2025 - 02:31 PM.

[clamchip]

I set the scope up with the supplied AH20mm straight thru.

Here it is at infinite focus. You can see how much drawtube is out, near full draw.

I would say the "moving baffles" in the drawtube are OK, tight but OK, not

enough for me to alter the scope over. All I was going to do is slide one baffle. To slide

the offending baffle no problem but I will not be able to slide it back. I would need

to make a puller and pull it back.

Robert

 

Edited by clamchip, 04 February 2025 - 05:40 PM.

[clamchip]

I torture tested Jason and absolutely no reflections off the walls, as expected with this too small

baffle at the sky end of the drawtube. This is very nice for contrast. I might get in there and make a mess

of things unless I sit down and draw the light cone and measure the baffles. Do it right or don't do it

at all, is what nurse Mendy is telling me. Frenchie says let's open a bottle of wine. Michelle flat out wants

it nuked out of there right now, no if's and's or but's. 

Robert

 

 

 

 

[jragsdale]

Speaking of baffles, is there an automatic baffle generator anywhere online? Like input the desired field stop size, aperture, focal length and number of baffles and it will tell you the hole size and location to put them? I'm hoping to 3D print some semi-automatically.

[Steve Allison]

Deleting post. I did not read some of the earlier posts carefully enough. Sorry.

[deSitter]

Speaking of baffles, is there an automatic baffle generator anywhere online? Like input the desired field stop size, aperture, focal length and number of baffles and it will tell you the hole size and location to put them? I'm hoping to 3D print some semi-automatically.

I think this is right.

 

-drl

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[luxo II]

Not quite - this is the geometry to design baffles… the spacing between them and the field of view matter,  too. The location of the first sets the location of the next and so-on
 

Edited by luxo II, 04 February 2025 - 10:51 PM.

[CHASLX200]

Moved the OTA off the floor this AM from the Mon nite on the 10" F/6 when i ripped my arm open.  Narrow doors are not fun.

[jragsdale]

Not quite - this is the geometry to design baffles… the spacing between them and the field of view matter,  too. The location of the first sets the location of the next and so-on
 

Excellent! Now just need that turned into a program or spreadsheet you can fill out.

[ccwemyss]

I rearranged the rings and accessories on the Edmund 4". I originally used a long Losmandy dovetail that happened to have holes where the mount screws could pass through and be hidden. But then the center of gravity was too far back, so I made a sliding counterweight to go up front for balance. Although it worked, it also meant that the back end would swing through a wide range of heights, from kneeling to tiptoe. And, of course, I couldn't reach the counterweight to adjust it when it was pointing skyward. 

 

So I narrowed the span between the OTA rings a bit and moved them as far back as I could. Then I slightly shortened the counterweight bar to fit between them (the weight won't clear the rings as it slides), and remounted the Edmund Voyager finder with a bit more space between its rings. The scope now has much less length behind the mount, and the weight is well within reach. Although it's pretty busy in that section of the tube now. I might rework the weight posts to mount on the far side of the finder rings, to reduce the clutter. But will give it a try first, to see if I like it or want to try something more radical like moving the Telrad base, so the weight can go even farther back. 

 

 

Chip W. 

[kjkrum]

https://www.gorin.it/extra/Oculari.pdf

There's an optical layout in there called the Tucson. I have to build one.

[clamchip]

It doesn't take much snow on my driveway to make us stuck here.

I have a gas powered snow blower and shovels if needed, a solid 2 hour job.

This winter I prepared for it and I'm not going to clear my driveway.

So I'm stuck here with all my telescopes, plenty of food, but no eggs! we have

chickens but they don't lay eggs this time of the year. No eggs no baking, bummer.

I did make eggless waffles, not too bad, I will say with reservations.

Today is 4 inch f/10 day. I did a trade with a friend and I have this lens I should

test. And I think I have a piece of tubing.

 

Robert

[jragsdale]

No eggs no baking, bummer.

We use Bob Red Mill's Egg Replacer for baked goods, can hardly tell the different in a baked item and WAY cheaper than eggs at today's prices.

[Kitfox]

Robert, get some Black Marans.  Ours lay every other day through the winter with no supplemental lighting (36 degrees north).  The Colombian Wyandottes stop completely from late November until late January.

 

Removed the mirrors from the 8" Tinsley.  They look to have decent coatings, so off to get some distilled water.  Going to work a bit on this focuser, too...I think it's a keeper, as if I have a choice; it's integral to the baffle tube.

 

Just an aside, why do the coatings on these mirrors from the 60's hold up and those from the 80's are failing?

[deSitter]

Robert, get some Black Marans.  Ours lay every other day through the winter with no supplemental lighting (36 degrees north).  The Colombian Wyandottes stop completely from late November until late January.

 

Removed the mirrors from the 8" Tinsley.  They look to have decent coatings, so off to get some distilled water.  Going to work a bit on this focuser, too...I think it's a keeper, as if I have a choice; it's integral to the baffle tube.

 

Just an aside, why do the coatings on these mirrors from the 60's hold up and those from the 80's are failing?

Interesting, first I've heard of this. Two guesses - less aluminum used, inferior or no SiO2 overcoating.

 

-drl

[Kitfox]

Interesting, first I've heard of this. Two guesses - less aluminum used, inferior or no SiO2 overcoating.

 

-drl

 

I know it's a bit anecdotal, but my two Tinsley's and a late 60's Questar all have quite nice coating condition.  I wish this child of the 60's was aging as well...

[Eric P]

I had a beautifully machined Robin Casady dovetail plate that fit nothing I owned until today.  An off-cut of black walnut, some threaded inserts and oil later I now have plate for my old Epsilon 160.

 

 

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[Airship]

Ugh. I had my 6" f/15 Jaegers refractor out yesterday as part of my use, use it, use it phase. All was well until I heard a distinct TINK from the drive box on the Cave mount that I am using. It sounded like something dropped on the enclosure, but I could see anything. However, much to my dismay the scope was no longer tracking. That can't be good. I opened the drive box and found the drive gear was not turning. On close inspection, the drive shaft was turning, but not the gear. Apparently, it popped loose from the shaft, though I was worried that something might have failed in the internal gear train. I decided to put everything away until I was rested and not to risk doing something stupid like dropping a tiny gear in the grass. To make a long story short (too late) I found that the drive gear and shaft were in good shape. The gear formed a good friction fit with the shaft and it looks like it was originally soldered on, though it doesn't look like silver solder. This could be what saved the drive train as the solder failed instead of the shaft. The root cause was the driven gear was almost seized, requiring a _lot_ of force to turn it. I should have checked this earlier, but the drive gave the illusion of working so I let it go. The fix was to just loosen the two mounting bolts that hold the worm assembly, spin the worm to make sure it was free (it was) and then to carefully snug the mounting bolts. There's enough play in the assembly that I could tighten everything down without binding the worm and wheel and without any significant play between the worm and wheel. On the drive gear and shaft I cleaned, cleaned, and cleaned them again, and then did is again to remove any grease. I didn't want to use an abrasive like steel wool as I didn't want to loosen the excellent fit between the great and shaft. I added just a drop of Loctite, and then quickly and firmly pressed the drive gear back onto the shaft. I was tempted to use solder, but for now I thought I'd try something a little less permanent in case I need to take it back apart (hopefully that's a hard no). After letting the Loctite cure for a couple of hours (just to be safe) I re-engaged the drive gear to the driven gear as carefully as I could making sure that there was good engagement between the gears, not too loose and not too tight, and snugged the motor mounting bolt. I fired up the drive for a couple of hours and it gave all the illusion of working. I'll know more the next chance I get to take the scope outside. Hopefully I dodged a bullet on this one. A search of the web suggests that these gears and motors are hard to replace. I have a very rough though floating in the back of my head that if it ever came to that I might try replacing the drive motor with a stepper motor, but hopefully it would come to that. Just in case I have squirreled away a couple of stepper motors and driver to play with.

 

So much to try, so few clear nights...

 

One crisis at a time...

 

[clamchip]

This telescope came to me in a bundle I bought from a fellow amateur up the road a spell last year.

Mostly raw tubing for telescope construction, a few unmounted objective lenses and this telescope.

I picked it up to move it today and I thought whoa that's light for a brass telescope, blow me off me

yardarm it's made of wood!

The grip is woven cloth. It has a sliding sun shade. It's missing the eyepiece section which undoubtedly

had the maker's name. 50mm edge contact objective in a proper cell. 

It looks to me like a navel glass. The Quartermaster had a spyglass like this one, I'll bet that's what

it is. I would like to clean the lens and find the focal length to see how much length the missing tail

section might amount too.

If anyone knows anything about this oldie please let's hear. I know almost nothing about telescopes

as old as this one.

Robert

 

Edited by clamchip, 12 February 2025 - 12:22 AM.

[clamchip]

I'm learning a few things about my mystery scope.

The main tube is called a "barrel" and it's wood in my example and it has "brass ends."

My "barrel" is "rope" covered with knotted ends.

I'm still pretty sure it's a Maritime Telescope, or Ships Telescope, but not necessarily a military Naval Telescope. Ships

carried a telescope with them for all sorts of important duties.

The edge contact objective is unusual and I hope might help point me to the maker.

My big fear is the missing aft section on this telescope may have been a "single draw" and it's going to be a pain to

reproduce it. I'm hoping the tail piece is supposed to be fixed with a helical rotating eyepiece affair, something I can

make easily.

I know nothing about brass era telescopes, I'm a curious monkey though.

"And now where is that clamchip Robert? let's see it."

"Right here at the red arrow I will have a better picture soon

 

Edited by clamchip, 12 February 2025 - 05:10 PM.

[clamchip]

Well this mornin I had the wind taken from me sails, I'm dead in the water. Better go drownd my face under the tap

of a keg of me favorite brown owl . Might as well finish what I'm doin and put me spyglass back in me drawer.

The focal plane is about 2 inches inside the tube. I guess the missing erector must "bring it out" where it can be

examined by the eyepiece. And that's a big huge bummer.

I finished tidying up the telescope. The retractable lens shade was very hard to slide so I carefully removed some

shallow dents and now it works as it should. The lens as you can see has a clamchip and you can see a flat spot

in the cell at 5 O'clock, no doubt the clam maker. Notice how thick the chipped flint is. I found a number eight on

the cell holder but could not find a matching number on any mating parts.

The lens display's very nice centered Newton's rings, and it's really cool that it is edge contact, no spacers. Exactly

50mm or 2 inches in diameter. Mounted in the cell clear aperture is 48mm and around F/11. With a 30mm Erfle and

it's huge eye relief I was able to slide it into the end of the tube 1-1/4" and view at infinity and it's astonishingly

sharp and bright at 18 power.

What an interesting short lived project. It's not gone to the grave yet. I'm wondering if one of those lens type image

erectors might extend the focal length and bring the focal plane out of the tube.

Robert

 

Edited by clamchip, 12 February 2025 - 05:12 PM.

[clamchip]

[deSitter]

Shouldn't be too hard to make a two-schromat erector from a spare Plossl. That will bring out the focal plane. Details in Sam Brown.

 

-drl

[clamchip]

I was able to put together a tailpiece for this old wood tube scope.

Luck was with me today I found a 1-1/4" eyepiece holder that threaded into the end of the telescope.

From here it was easy, find an optical devise to draw the focal plane out of the tube.

I tried every lens gadget in hobbyland, every Barlow, etc. and finally a Edmund Image Erector did it.

This Edmund unit has what I think actually is two achromats, held in it's tube with split-rings so it's tunable

from 1.5X to around 3X by sliding the lens holder inside this tube. I have it as low power as it will go.

I'm sliding the image erecting tube for focus. It is very smooth to focus in a helical fashion, the chrome plate

riding on anodized aluminum has a great feel and surprisingly precise. You focus where I placed the arrow

on the paper, I find this the most natural and comfortable position. The chrome erector tube has a step in it

and I have it adjusted so infinite is almost at the step with plenty of drawout for the garden.

I picked a big heavy Sherman tank eyepiece for good balance since this telescope is to be hand held when

observing. I'm not sure what the overall power of this system is. Native is 18 power, add the Image erector and

I would like to guess around 20X -25X or so, definitely difficult to hold without experience. I'll find a rest for

it when I observe, fence rail or a tree branch or something.

Robert

 

 

Edited by clamchip, 13 February 2025 - 05:24 PM.

[clamchip]

Here it is outside for a shakedown cruise around the neighborhood.

Too much power, I want to hand hold it. I have a 45mm eyepiece I can try, that's a 30 in there now.

A star prism would be a nice feature, like the old man from my files. I wish I knew something about

this cool old photo but sorry nothing.

Robert