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tim53
Pooh-Bah
Reged: 12/17/04
Posts: 1440
Loc: Highland Park, CA
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But...
First things first.
First, here's a series of pics of the lens and cell. The cell appears custom made, but it seems like a decent machine job. The lens doesn't move in the cell by much at all. I set it on top of a plastic sourcream tub (or whatever it was) so I could lower the cell from the lens as you see in the pic after I took out the retaining ring.
There are a few small chips out of the edge of the lens. Most of these are covered by the retaining ring, but the one you see that's been marker'd out in black is about 1/2" into the field from the retaining ring.
The cell is unpainted, so the main reason I took it apart was to squirt some flat black on it to help cut down reflections off that shiny aluminum.
But when I got it apart, I noted the two "3"s printed on it, with arrows. These aren't in line and aren't pointing in the same direction. The guy who gave me the lens/cell about 5 years ago has passed away, so I don't know whether it was assembled incorrectly, or if this alignment is a result of some testing!
And finally, as I design a means of holding it in the plywood tube I'm about to make, which way is the sky? Both outer surfaces are convex, but the lens on top in the picture is thinner at the edge than the other. I presume that this is the biconvex element that goes skyward, but if someone knows different, by all means tell me! 
The spacers between lenses are tape of some kind. The two lenses are stuck together with them. Otherwise, I'd gently lift the top element off and determine this for myself. Probably, I'll have to do that anyway, if the lenses aren't aligned properly here.
Anyway, first pic. Next, I'll go back outside and double check the FL before I cut any wood.
-Tim.
--------------------
"We`re just waiting looking skyward as the days come down.
Someone promised there`d be answers, if we stayed around."
-Orchestral Maneuvers in the Dark, "The Romance of the Telescope"
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tim53
Pooh-Bah
Reged: 12/17/04
Posts: 1440
Loc: Highland Park, CA
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2:
--------------------
"We`re just waiting looking skyward as the days come down.
Someone promised there`d be answers, if we stayed around."
-Orchestral Maneuvers in the Dark, "The Romance of the Telescope"
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tim53
Pooh-Bah
Reged: 12/17/04
Posts: 1440
Loc: Highland Park, CA
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In both pics, the "3"s with arrows are visible. In the upper element, it's on the left side, with the arrow pointing down. in the lower element, it's on the right, with the arrow pointing up.
-Tim.
--------------------
"We`re just waiting looking skyward as the days come down.
Someone promised there`d be answers, if we stayed around."
-Orchestral Maneuvers in the Dark, "The Romance of the Telescope"
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DAVIDG
Carpal Tunnel
Reged: 12/02/04
Posts: 1985
Loc: Hockessin, De
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Tim,
The arrows should line up so the heads are pointing at each other. They are indications of were the wedge in the the elements cancel each other and the biconvex element is the crown and faces the sky.
You should have between 5 to 10 thousands clearance around the diameter of the elements vs the ID of the cell. If the cell is too tight it will pinch the optics when it cools and it also cause one to easily chip the edges trying to get it in and out the cell.
Does the metal lip on the inside of the cell have three raised areas at 120 ° apart ? If so, these areas should be aligned with the foil spacer between the lens elements so that you get even pressure when the retail ring is applied.
The lens should have a slight rattle when you place it in the cell and give it a light shake. Check it in two direction that 90° apart. Either the elements or the cell might not be perfectly round. My friend's 6" Schupmann had a cell that was out of round and was pinching the optics. The lens rattled just fine in one direction but was very tight in the other. Opening up the cell made a huge difference in the images.
- Dave
--------------------
Homemade 'scopes 8"f/7,6" f/5", 6"f/4, 4.25" Schief. 60mm Coronagraph,60mm H-alpha system, 4.25" White-light Solar Newtonian,solar spectroscope, 4.5" f/16 Schupmann Medial refractor, 14 Stellafane awards 7 in optics
Engineering = Taking what you have and making what you need.
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tim53
Pooh-Bah
Reged: 12/17/04
Posts: 1440
Loc: Highland Park, CA
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I'll go outside and check!
-Tim.
--------------------
"We`re just waiting looking skyward as the days come down.
Someone promised there`d be answers, if we stayed around."
-Orchestral Maneuvers in the Dark, "The Romance of the Telescope"
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tim53
Pooh-Bah
Reged: 12/17/04
Posts: 1440
Loc: Highland Park, CA
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Dave:
The lens elements weren't hard to get apart. So I have the arrows pointing toward one another now.
The cell fits better (feels like a few 'thou gap after I rotated it about 90 degrees from where it was). There are no shims on the surface against the back element (4th surface). I could probably scare up some thin cardboard shims or something. Any paritcular recommendations?
-Tim.
--------------------
"We`re just waiting looking skyward as the days come down.
Someone promised there`d be answers, if we stayed around."
-Orchestral Maneuvers in the Dark, "The Romance of the Telescope"
|
rwiederrich
Goldfinger
Reged: 11/17/05
Posts: 8320
Loc: Bremerton Washington
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Quote:
But...
First things first.
First, here's a series of pics of the lens and cell. The cell appears custom made, but it seems like a decent machine job. The lens doesn't move in the cell by much at all. I set it on top of a plastic sourcream tub (or whatever it was) so I could lower the cell from the lens as you see in the pic after I took out the retaining ring.
There are a few small chips out of the edge of the lens. Most of these are covered by the retaining ring, but the one you see that's been marker'd out in black is about 1/2" into the field from the retaining ring.
The cell is unpainted, so the main reason I took it apart was to squirt some flat black on it to help cut down reflections off that shiny aluminum.
But when I got it apart, I noted the two "3"s printed on it, with arrows. These aren't in line and aren't pointing in the same direction. The guy who gave me the lens/cell about 5 years ago has passed away, so I don't know whether it was assembled incorrectly, or if this alignment is a result of some testing!
And finally, as I design a means of holding it in the plywood tube I'm about to make, which way is the sky? Both outer surfaces are convex, but the lens on top in the picture is thinner at the edge than the other. I presume that this is the biconvex element that goes skyward, but if someone knows different, by all means tell me!
The spacers between lenses are tape of some kind. The two lenses are stuck together with them. Otherwise, I'd gently lift the top element off and determine this for myself. Probably, I'll have to do that anyway, if the lenses aren't aligned properly here.
Anyway, first pic. Next, I'll go back outside and double check the FL before I cut any wood.
-Tim.
Tim before you attempt to seporate the two elements...DON'T!
The 3 three's may have originally been placed there for alignment...and over time someone may shifted the two elements to correct for aberrations.
Let things be alone. After you mount the cell..do a star test and see if the elements have shifted or not.
If the spacers are *sticky* this may be to hold them in place at that inclination.
Good luck...and remember to post your progress on my yahoo site too..... 
Rob
--------------------
www.goldmtobservingcenter.com
A great place for amateur astronomers, and ATM's to come and enjoy their hobby.
http://tech.groups.yahoo.com/group/HomemadeRefractorTelescopes/ My homemade refractor group.
www.vimeo.com/6014031
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DAVIDG
Carpal Tunnel
Reged: 12/02/04
Posts: 1985
Loc: Hockessin, De
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Tim,
I use Kapton tape for shims, both along the back rim and three tabs along the slide, that will minimize metal to glass contact.
Take the lens and place it under monochrome light if you have it or if you don't use an Engery Saver type bulb. You should see interference rings between the two elements. They should appear perfectly round when viewed from looking straight down on the elements. If the rings are off center, then that usually indictates that one of the spacers in thicker then the others.
You said that the spacer were tape ? If so then they don't sound like the stock spacers and maybe the wrong thickness. Jaegers is still around under Jaegers Jr. They might know the correct thickness of the spacers.
The "right" way to set the spacing is to set the lens up in double pass autocollimation mode and look at the correction in green light, then adjust the spacing for the least amount of spherical abberration.
- Dave
--------------------
Homemade 'scopes 8"f/7,6" f/5", 6"f/4, 4.25" Schief. 60mm Coronagraph,60mm H-alpha system, 4.25" White-light Solar Newtonian,solar spectroscope, 4.5" f/16 Schupmann Medial refractor, 14 Stellafane awards 7 in optics
Engineering = Taking what you have and making what you need.
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tim53
Pooh-Bah
Reged: 12/17/04
Posts: 1440
Loc: Highland Park, CA
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Rob:
Oops, I already moved them. But since I have the pics from where they were before, I could move them back.
Dave:
I have compact fluorescent lights in my shop. Will those work?
-Tim.
--------------------
"We`re just waiting looking skyward as the days come down.
Someone promised there`d be answers, if we stayed around."
-Orchestral Maneuvers in the Dark, "The Romance of the Telescope"
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tim53
Pooh-Bah
Reged: 12/17/04
Posts: 1440
Loc: Highland Park, CA
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OOo!
I just tried that with the compact fluorescents, and it WORKS!
The rings are there, and seem to be perfectly concentric, but how many should there be? Seems there's thousands of them.
-Tim.
--------------------
"We`re just waiting looking skyward as the days come down.
Someone promised there`d be answers, if we stayed around."
-Orchestral Maneuvers in the Dark, "The Romance of the Telescope"
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tim53
Pooh-Bah
Reged: 12/17/04
Posts: 1440
Loc: Highland Park, CA
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Okay, I just tried it again with the lenses oriented like they were in the pic above (there were shadows of the shims still visible to help me do that), and the rings are way off center.
They're right on center with the arrows aligned, though. The shims look like they have a weak adhesive on one side, and they're all regularly sized - 1/4" long by 3/4" wide.
-Tim.
--------------------
"We`re just waiting looking skyward as the days come down.
Someone promised there`d be answers, if we stayed around."
-Orchestral Maneuvers in the Dark, "The Romance of the Telescope"
|
rwiederrich
Goldfinger
Reged: 11/17/05
Posts: 8320
Loc: Bremerton Washington
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Quote:
Rob:
Oops, I already moved them. But since I have the pics from where they were before, I could move them back.
Dave:
I have compact fluorescent lights in my shop. Will those work?
-Tim.
Dave is giving you steller advice...but I would be a bit more cautious. Dave mentioned that Jaegers may not have used tape(sticky) back spacers and they may have been placed after the fact. And like Dave also mentioned a double pass autocolimation will reveal the spherical rings you are looking for to optimize spherical aberrations. this may have been done and this may be an indication why the spacers are what they are and that the arrows do not line up.
Nothing is set in stone...so check the current alignment before you *THINK* you need to make changes to it. There might be reasons why things are the way they are.
There is pleanty of time to realign the arrows and set the elements up as they theoretically should be.
Good luck.
Rob
--------------------
www.goldmtobservingcenter.com
A great place for amateur astronomers, and ATM's to come and enjoy their hobby.
http://tech.groups.yahoo.com/group/HomemadeRefractorTelescopes/ My homemade refractor group.
www.vimeo.com/6014031
|
rwiederrich
Goldfinger
Reged: 11/17/05
Posts: 8320
Loc: Bremerton Washington
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Quote:
Okay, I just tried it again with the lenses oriented like they were in the pic above (there were shadows of the shims still visible to help me do that), and the rings are way off center.
They're right on center with the arrows aligned, though. The shims look like they have a weak adhesive on one side, and they're all regularly sized - 1/4" long by 3/4" wide.
-Tim.
Excellent! You just figured it out.
It appears the 2 elelements have shifted and the test revealed that. I would have done the monchromatic light test before and determined the current alignment. You just did it the other way around. Good and it proved very successful...
See..how much a little education can reveal....?
Now you know a bit more on how to align and even test your objectives elements alignment.
This is the best kind of way to educate yourself...and it didn't harm a thing.
Dave is to be warmly thanked for his acute attention. 
Rob
--------------------
www.goldmtobservingcenter.com
A great place for amateur astronomers, and ATM's to come and enjoy their hobby.
http://tech.groups.yahoo.com/group/HomemadeRefractorTelescopes/ My homemade refractor group.
www.vimeo.com/6014031
|
tim53
Pooh-Bah
Reged: 12/17/04
Posts: 1440
Loc: Highland Park, CA
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Rob and Dave:
I took this pic of the rings with my iPhone (love 21st century technology!). Obviously, I couldn't hold the phone exactly on axis, but I got a lot closer than I could with my haid. The ghost rings are due to reflections viewed off axis.
How does this look? (other than the obvious grunge from the spacers and the dirt that's enhanced by the technique and my stretch of the image!)
--------------------
"We`re just waiting looking skyward as the days come down.
Someone promised there`d be answers, if we stayed around."
-Orchestral Maneuvers in the Dark, "The Romance of the Telescope"
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tim53
Pooh-Bah
Reged: 12/17/04
Posts: 1440
Loc: Highland Park, CA
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The two black blobs near the edge at top and lower right are where the bigger chips have been inked out.
-Tim.
--------------------
"We`re just waiting looking skyward as the days come down.
Someone promised there`d be answers, if we stayed around."
-Orchestral Maneuvers in the Dark, "The Romance of the Telescope"
|
tim53
Pooh-Bah
Reged: 12/17/04
Posts: 1440
Loc: Highland Park, CA
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|
Quote:
Quote:
Okay, I just tried it again with the lenses oriented like they were in the pic above (there were shadows of the shims still visible to help me do that), and the rings are way off center.
They're right on center with the arrows aligned, though. The shims look like they have a weak adhesive on one side, and they're all regularly sized - 1/4" long by 3/4" wide.
-Tim.
Excellent! You just figured it out.
It appears the 2 elelements have shifted and the test revealed that. I would have done the monchromatic light test before and determined the current alignment. You just did it the other way around. Good and it proved very successful...
See..how much a little education can reveal....?
Now you know a bit more on how to align and even test your objectives elements alignment.
This is the best kind of way to educate yourself...and it didn't harm a thing.
Dave is to be warmly thanked for his acute attention.
Rob
And you know what? I get all goose-bumpy with excitement doing this kind of stuff! Like I got when I looked through Dave's and others' schupmans at Stellafane 2 years ago.
I'm going to dig up that old Telescopics 8" mirror kit that I "started" 37 years ago and finish it when i get the chance. And if this refractor performs well enough on the planets, maybe I'll try to make one myself! (a schupman, that is).
-Tim.
--------------------
"We`re just waiting looking skyward as the days come down.
Someone promised there`d be answers, if we stayed around."
-Orchestral Maneuvers in the Dark, "The Romance of the Telescope"
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KevinP
super member
Reged: 06/25/07
Posts: 170
Loc: Edmonton
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Quote:
Take the lens and place it under monochrome light if you have it or if you don't use an Engery Saver type bulb. You should see interference rings between the two elements. They should appear perfectly round when viewed from looking straight down on the elements. If the rings are off center, then that usually indictates that one of the spacers in thicker then the others.
- Dave
I don't mean to hi-jack this great thread, but this quote caught my eye.
My 80mm lens came without index marks, so I marked them as they sat in the box and try to keep them aligned when I fit them to the cell. Can I assume this technique works for smaller lens sets also? I am almost ready to mount the lens permanently and it would be nice to have everything aligned as close as possible before hand.
--------------------
Kev
Sketches
------------------
Antares 200 mm / f5
ATM 82/700 refractor in progress
Bushnell 10x50
Celestron 15x70
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tim53
Pooh-Bah
Reged: 12/17/04
Posts: 1440
Loc: Highland Park, CA
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Kev:
I just tried to do the same thing with a couple of 3" lenses, and can't see the rings. ONe's an f/6 and the oher's an f/15.
-Tim.
--------------------
"We`re just waiting looking skyward as the days come down.
Someone promised there`d be answers, if we stayed around."
-Orchestral Maneuvers in the Dark, "The Romance of the Telescope"
|
DAVIDG
Carpal Tunnel
Reged: 12/02/04
Posts: 1985
Loc: Hockessin, De
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We're getting things mixed up here. First the alignment marks, what was done was the thickness of each element was measured and the high and lows spot on each found. The alignment marks are the high spot on one and the low spot on the other. When they match up the wedge in each element cancels. If you have a lot of wedge a star turns into a tiny spectra and a small amount makes star astigmatic.
Second the interfernce test. This is to determine if the air gap between the two elements is the same. The wedge in the elements and the air gap are not 100% related to each other. You can have the wedges off set in the element and with air gap spacers being the same thickness get perfectly concentric rings.
The interference test doesn't work on all lens. The reason is that either the air gap bewteen the two elements is too large and/or the two inner radii are different. From the picture of your 6" f/15 your only see rings in the middle, that is because only at that area are the two lens close enough for them to form. It also indicated that the radii are somewhat different. If they were close or the same, you would rings form across the complete surface if the spacing was close enough. Back to figuring another Schupmann objective.
- Dave
--------------------
Homemade 'scopes 8"f/7,6" f/5", 6"f/4, 4.25" Schief. 60mm Coronagraph,60mm H-alpha system, 4.25" White-light Solar Newtonian,solar spectroscope, 4.5" f/16 Schupmann Medial refractor, 14 Stellafane awards 7 in optics
Engineering = Taking what you have and making what you need.
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tim53
Pooh-Bah
Reged: 12/17/04
Posts: 1440
Loc: Highland Park, CA
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Thanks Dave for the explanation!
Okay, I managed to determine the focal length by setting the lens in its cell on the picnic table outside and viewing a distant hill (about 1.5 miles away) with a 28mm RKE. This came out to 86". So, allowing for some focuser travel and 2" star diagonal backfocus, plus distance inside the support for the cell (that will be incorporated into the dewcap), I get a tube length of 78". A convenient length. I would rather err on the side of too short, because I didn't with my 6" f/10, and I can't use 2" star diagonals with it (until I cut it shorter, that is). I can always add a block behind the focuser to bring it out more if needed.
I'm going to start cutting a pattern for the baffles, then the baffles, then the tube slats for the nonagonal tube.
Speak now or forever hold your peace! (especially if you think I'm about to screw up!) 
-Tim.
--------------------
"We`re just waiting looking skyward as the days come down.
Someone promised there`d be answers, if we stayed around."
-Orchestral Maneuvers in the Dark, "The Romance of the Telescope"
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