phzahn
member
Reged: 08/19/11
Loc: Littleton Colorado
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Re: and finally
[Re: highfnum]
#4832083 - 09/28/11 12:15 PM
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Yes, when you remove the last convex lens, that fixed 30mm one under the beamsplitter, everything goes negative, images look farther away.
You are now looking thru the concave 30mm moveable lens.
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highfnum
Carpal Tunnel
Reged: 09/06/06
Loc: NE USA
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Re: and finally
[Re: phzahn]
#4832432 - 09/28/11 03:07 PM
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excellent - that means Im starting to understand whats going on
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highfnum
Carpal Tunnel
Reged: 09/06/06
Loc: NE USA
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Re: and finally
[Re: phzahn]
#4832818 - 09/28/11 06:56 PM
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can u determine fl of convex lens
estimate is good enough
just focus on indoor light and measure distance
where image is sharpest
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phzahn
member
Reged: 08/19/11
Loc: Littleton Colorado
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Re: and finally
[Re: highfnum]
#4833802 - 09/29/11 10:01 AM
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hello highfnum,
Finally, someone that does not assume that I am any sort of an optical expert. You ask your questions in a clear and easily understood manner, keep it up, I do appreciate it.
The answer to your question is 70mm. That is the max distance for a nice bright sharp focus.
Edited by phzahn (09/29/11 10:03 AM)
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highfnum
Carpal Tunnel
Reged: 09/06/06
Loc: NE USA
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Re: and finally
[Re: phzahn]
#4833915 - 09/29/11 11:02 AM
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thx - I try to reduce number of assumptions
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DonnyM
member
Reged: 10/20/10
Loc: Spirit Lake, Idaho
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Re: and finally
[Re: highfnum]
#4844304 - 10/04/11 10:13 PM
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My lens arrived tonight. Wow that's allot of glass.
There are a few scratched on the large housing but the optics are clear other than a little dust.
The zoom works easy if I rotate the inner helical piece. It moves so easy if the lens is pointing down it will spin back to its stops.
The big geared ring on the outside does not turn. There is a chrome knob on one side next to the geared ring. If I loosen it the ring still does not turn.
Whats the simplest way to get to the 4 screws that hold the shutter to the beam splitter?
Donny
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TedK
newbie
Reged: 01/08/11
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Re: and finally
[Re: DonnyM]
#4844386 - 10/04/11 11:21 PM
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To add to the mix...
I've been following this discussion avidly. Playing with the lenses, I'd come to a somewhat independent conclusion that I needed additional lenses between the corrector lens and an eyepiece.
I would've gone for the complete unit if it was available when I bought the lens set. (I'm not convinced I won't anyway, that or kick myself forever if I miss the chance).
I've been trying to chart this lens design out
So when you guys are discussing the additional lenses in the complete unit, please humor me and add a little more description than concave or convex. Please? Yeah, I know you might be working on getting the real details like type of glass and focal length, but I would love any additional crumbs you all might drop.  
I have the original drawing in Google's sketchup, and yeah, they're my crummy lens drawings.
Edited by TedK (10/04/11 11:38 PM)
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DonnyM
member
Reged: 10/20/10
Loc: Spirit Lake, Idaho
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Re: and finally
[Re: TedK]
#4844464 - 10/05/11 12:49 AM
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Ok the silver knob does release the main part to rotate. I would say this is the focus. I was trying to turn the gear while the lens was sitting on the table face down. In that case you have to turn everything else.
There is a silver plate screwed to the inner rotating assembly this is adjustable to allow for the amount of focus travel in or out. There are 9 holes and the slotted plate covers 3 holes. So it has allot of adjustment.
I pulled the beam splitter out and I see a lense in the shutter housing and small lens in the back of the main lens assembly. Will the lens in the shutter need to be removed to allow use of a camera?
I still do not see how to remove the shutter box without taking it apart from the inside. I would like to avoid that.
Looking at the size of the little lens it is making me wonder if I will get full coverage of the chip in my DSLR.
Donny
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phzahn
member
Reged: 08/19/11
Loc: Littleton Colorado
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Re: and finally
[Re: DonnyM]
#4844948 - 10/05/11 10:39 AM
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Donny,
to get the shutter housing off you must first remove the shutter plate from the inside of the box. Under the shutter plate are 4 screws holding the shutter housing to the beamsplitter housing. There are no lenses in the shutter box. There is a lens in the back of the beamsplitter housing. That lens will stay there even after you remove the shutter box. Between the shutter box and the beamsplitter housing are some plastic shims. I think they may have been used to set the distance to the film used. You wont be needing them.
The shutter plate is held in its box with two screws that you can see on the outside of the shutter box. You will have to take the wiring harness end connector apart and put it back together after you have the shutter out. No big deal.
You do not have to take the shutter apart from the inside. The shutter is on its own plate. Remove this entire assembly after the two side screws are removed from the outside of the box. They are the two lowermost screws. The entire shutter plate then lifts out revealing 4 screws that hold the box to the beamsplitter.
Again, only 2 screws hold the shitter plate in the box. They are not the slotted screws, they are the screws that need an allen wrench to unscrew.
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DonnyM
member
Reged: 10/20/10
Loc: Spirit Lake, Idaho
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Re: and finally
[Re: phzahn]
#4846335 - 10/06/11 12:26 AM
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Thanks for the information. Pretty slick how the shutter comes out. Hopefully this weekend I can make a nice holder for the the lens and a adapter for the camera. I need to figure out how far away from the 30mm fixed lens under the beam splitter to the camera chip needs to be.
Looks like I will need the other lens in the top of the beam splitter. Without it the spot size is around 1" in dia at 6" from the 30mm fixed lens. At 3 feet its 1/2" in dia.
Zoomed all the way out and the lens focused as short as I can it is 48" from the fixed 30mm lens to a focused point. I used a group of 4 bright led's in a dark room at 12' from the lens. And projected them on a sheet at the back. Came to focus at 48".
Tomorrow I will try it with the upper lens from the beam splitter.
Donny
Edited by DonnyM (10/06/11 12:54 AM)
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DonnyM
member
Reged: 10/20/10
Loc: Spirit Lake, Idaho
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Re: 6" Triplet - F1.25?
[Re: phzahn]
#4846767 - 10/06/11 09:52 AM
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Peter,
Do you have any pics of unscrewing the lenses? The inside of mine is very dirty. Tons of dust.
thanks,
Donny
Quote:
Oh my, I just found out this can be taken further apart without risk.
By removing the focus stop plate the entire moveable lens barrel can be unscrewed from the main objective tube. Beamslitter, cam ring, fixed and moveable 30mm lenses and the negative 90 mm lens set, the whole shebang.
Peter
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phzahn
member
Reged: 08/19/11
Loc: Littleton Colorado
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Re: 6" Triplet - F1.25?
[Re: DonnyM]
#4846967 - 10/06/11 11:19 AM
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Donny, I have not done this yet, but it is on my list of things to do, when I get a little more time, perhaps in the next two weekends.
I got this idea from studying the pictures on the Surplus Shed website. I am fairly sure that I am correct.
Before you jump into the fire I strongly advise you to honestly evaluate your own mechanical aptitudes. Please do not take that statement as any sort of insult, it is not intended to be that at all.
This is a pretty complicated assembly, and it may well be that once we get into it a bit, some unforseen issue may arise, it usually does.
I own a fair sized industrial machine shop and this sort of work we do on a daily basis. I have no problem going where no man has gone before. But that is only because I have just over 40 years experience dealing with assemblies far more complicated than this lens.
When I take this apart I will document it with pictures and a lot of measurments. I know that those of us who have an interest or investment in this lens want to know all we can about it. I will have a detailed instructional post here on how to do the disassembly with any cautions as required.
I will also make a nice 2D CAD assembly detail of the lens including as many dimensions and travels as I can document. I will make the drawing available to everyone in two ways. You can either ask me for a the CAD file to import into your own CAD program or I will scan the drawing into a .jpg file. It may be too big to post here, but I would be happy to email it to anyone with interest.
TedK, I have taken note of your request and will do my best to get as much information as possible during the disassembly. I will also do a little experimenting with what can be done to effect the focal length and some other things.
OK, if I have forgotten anything or you all have any special requests better ask now so I can do it all at one time. I dont intend to take this apart more than just the one time.
Best Regards,
Peter
as always, please excuse typos.
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SBarden
super member
Reged: 01/11/11
Loc: Sunspot, NM
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Re: 6" Triplet - F1.25?
[Re: phzahn]
#4847426 - 10/06/11 03:27 PM
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Hi Peter, if you happen to have a spherometer, it would be good to measure the outer surfaces of each lens.
I have access to Zemax and have a model of the triplet and negative doublet. If I can get ideas on the rest of the optics, I might be able to find a working solution (though it wouldn't necessarily be the same as the actual lens given lacking details of glass types and inner surfaces).
If you don't have a spherometer or other means to estimate the surface curvature, that is fine. Someday I'll likely take mine apart, but not any time soon.
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DonnyM
member
Reged: 10/20/10
Loc: Spirit Lake, Idaho
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Re: 6" Triplet - F1.25?
[Re: SBarden]
#4847981 - 10/06/11 09:22 PM
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I managed to get a chance to do some measurements.
I used my Sony A300 DSLR to see where it came to focus with the beam splitter box in place. The prism is removed. Just the lens that was closest to where the shutter was is left in the box.
All dimensions are to the face of the camera with no lens installed. I am focusing on trees a couple miles away. To rainy to see the sky or the mountains that are 15 miles away.
Zoomed out, focus all out I get 1/4"
Zoomed out, focus all in I get 1 1/4"
Zoomed in and focus all in I get 2"
Zoomed in and focus all out I get 1 1/2"
I was worried about vignetting. That is not a problem. The problem I do have I guess is my chip is not able to see the full image. I can move the camera around and there is more image in all directions. I think a much larger chip size could be used. The Sony chip is 23.6 x 15.8mm or 0.920" x 0.622".
I wonder if I need a focuser or if I can just mount the camera on a adapter and use the lens to do the focus. Seems there is enough travel.
There is a lock for the focus. I am not seeing a lock for the zoom. Any suggestions?
Donny
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phzahn
member
Reged: 08/19/11
Loc: Littleton Colorado
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Re: 6" Triplet - F1.25?
[Re: DonnyM]
#4848792 - 10/07/11 11:29 AM
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Yes the zoom changes the focus distance quite a bit. I dont think that the lens focusing will be enough if you want to use the zoom of the lens. Seems to me your going to need a focuser at the back as well.
So you took out the prism? That is not something I plan on doing. I saw that the adjustment screw on the side view lens carrier was waxed, and I also saw that the prism is mounted with slotted holes in its carrier plate. I have to believe that a lot of attention was given here to make sure the alignment was dead on.
I plan to use that side port for guiding and/or finding. If you dont intend to use it for anything, removing the prism is a good idea as it gets all the available light to the camera chip. But the picture Keiths' friend took shows there is still a lot of available light even with the splitter prism installed.
As you saw, focusing with the beamsplitter lenses completely removed is over 45 inches. I also did a few similar quick and dirty tests. That 45+ inch difference can be reduced to approximately 18 inches depending on the zoom setting.
There are so many possible options with this lens. I become more and more convinced that to do this right will require much patience, and far more experimentation than the little I have done so far.
For instance, you can change the size of the image by manipulating the distance between the 30mm convex and 30mm concave lens. If you fix that distance so they move in tandem I think you would wind up with an image that would fit your camera chip. This is purely speculation, the test was done late at night after work.
I would prefer to use this in the shortest configuration possible. But I will not rule out a standard length telescope setup with this assembly as the main objective. But only if there are some clear and useful advantages to doing it that way.
I much prefer to have the weight concentrated on the mount the way it is with the short configuration. Seems to me this is about as good as it gets for very long exposure photo work.
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phzahn
member
Reged: 08/19/11
Loc: Littleton Colorado
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Re: 6" Triplet - F1.25?
[Re: SBarden]
#4848797 - 10/07/11 11:32 AM
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Sam,
Sorry I do not have an instrument like that at my disposal. I have seen one I think. Is it one of those things that has a 1" dial indicator and resembles a depth micrometer setup?
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SBarden
super member
Reged: 01/11/11
Loc: Sunspot, NM
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Re: 6" Triplet - F1.25?
[Re: phzahn]
#4860855 - 10/14/11 01:21 PM
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Yes, it is a dial indicator mounted on 3-legs to measure the saggital depth.
Sam
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SBarden
super member
Reged: 01/11/11
Loc: Sunspot, NM
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Re: 6" Triplet - F1.25?
[Re: SBarden]
#4860862 - 10/14/11 01:23 PM
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At long last, I finally have mine mounted up. With any luck and a forgiving wife, I'll try to get some images this weekend. It has been spectacularly clear here this week and the moon is now past full, so the early evening should provide a bit of dark time. I'll take some photos of my setup as well.
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phzahn
member
Reged: 08/19/11
Loc: Littleton Colorado
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Re: 6" Triplet - F1.25?
[Re: SBarden]
#4866458 - 10/17/11 06:30 PM
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I've just noticed something.
With the focusing ring turned all the way clockwise to the stop, changing the zoom from minimum to maximum does not appreciably (maybe 1/4") change the focus distance for an eyepiece, about 3.6 inches for my lens.
With the focus ring turned all the way counterclockwise, moving the zoom from minimum to maximum changes the focus distance from 3.5 inches to 1.8 inches.
Something to keep in mind if you want the most room for a camera or something.
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SBarden
super member
Reged: 01/11/11
Loc: Sunspot, NM
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Re: 6" Triplet - F1.25?
[Re: phzahn]
#4866684 - 10/17/11 09:15 PM Attachment (89 downloads)
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Here is an image of M31. 100 second exposure at medium zoom with a Blue 80A filter and my Quantix camera.
I've noticed that at higher zoom, I'm getting coma in the outer regions of the field. At minimal zoom, that coma is very negligible.
Edited by SBarden (10/17/11 09:16 PM)
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