Davon Micro-Telescope.

Everything relating to microscopy hardware: Objectives, eyepieces, lamps and more.
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apochronaut
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Davon Micro-Telescope.

#1 Post by apochronaut » Tue Oct 27, 2015 3:19 pm

This is a peculiar thing, made in England between the late 19th century and the 1920's. The later ones had a slightly more modern design but generally, they didn't change much. They were a kit, with several objectives and eyepieces as well as the options for use as a telescope all housed in a handsome wooden case. They show up for sale in the U.K., sometimes.
The telescope barrel has a cemented triplet for an objective( not cracked as the picture indicates; that is a reflection) and is quite well corrected. The objectives are in inches with an N.A. stamped on the barrel, i.e. 1 inch N.A. .20, and are R.M.S, standard. The eyepieces are the old 1" diameter, widely used prior to the adoption of the R.M.S. standard of 23.3mm. Generally there has been an attempt to fit it with good optics for the time. It is easy to see that the principle, could be improved by using an apochromatic triplet for instance as the primary objective and low power apos for objectives.

The stand itself is well made and all brass, with a rack and pinion coarse focus and a micrometer screw fine focus ,acting on the objective mount. The mirror nestles into a little hook , when not in use, or since it is focusable it can be removed and saved from damage, no doubt the reason it has survived this long. Mine does not have a condenser but the sleeve under the stage, which accepts the telescope barrel, can accept a condenser too, so there may have been one.

By using a shorter focal length objective , you can get an incredibly close focus and it turns into a macro lens. With a 16mm objective, you can focus at about 2 ft. and the weave in fabric is magnified about 20X.
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zzffnn
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Re: Davon Micro-Telescope.

#2 Post by zzffnn » Tue Oct 27, 2015 7:23 pm

Very cool! Thank you for sharing!
How does it work as telescope though? As it is shown in photo 1 (do you have to remove the microscope objective)?
So microscope is 100x total and macroscope is at 20X? What about telescope magnification?

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lorez
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Re: Davon Micro-Telescope.

#3 Post by lorez » Tue Oct 27, 2015 7:38 pm

That is a most interesting instrument. What are your plans for restoration ?

lorez

JimT
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Re: Davon Micro-Telescope.

#4 Post by JimT » Tue Oct 27, 2015 9:55 pm

I actually knew that primitive telescopes and microscopes (having a similar optic train) had been used a long time ago as both with some modifications. But I am not that old ;)

apochronaut
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Re: Davon Micro-Telescope.

#5 Post by apochronaut » Tue Oct 27, 2015 10:07 pm

Fan. It actually uses the microscope objective when used as a telescope. You can increase the telescope magnification , within reason by changing the microscope objective.

The Macro function, I just recently discovered while messing with it. I will play with it some more and see what it's limits are. The telescope image is quite poor , about 5 X with the 1" objective( approx. 5X). A No.2 eyepiece is usually about 10X, and this one looks to be about that.

Part of it's function is possibly due to it's rather odd eyepiece ,which has a concave eyelens. The eyepiece is marked : Davon No, 2.

Lorez. I've had this for a long time and have really done nothing with it. I have been thinking of painting the base but aside from that, I may just clean up the brass. Everything works as it should.

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Re: Davon Micro-Telescope.

#6 Post by gekko » Wed Oct 28, 2015 12:06 am

A very nice old instrument. I guess (I may be wrong) that the main difference between a microscope and a telescope is the focal length of the objective? Thank you for showing this.

apochronaut
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Re: Davon Micro-Telescope.

#7 Post by apochronaut » Wed Oct 28, 2015 1:28 am

Pretty much. What they have done here is use a lens system to bring an image to focus at the microscope stage , rather than at an eyepiece. From there it is picked up and magnified by the microscope, rather than being picked up and magnified by the telescope eyepiece.
Essentially, the entire microscope is an extended eyepiece.

charlie g
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Re: Davon Micro-Telescope.

#8 Post by charlie g » Wed Oct 28, 2015 2:03 pm

I love the way you blended off:'buggones' post on our moon...bravo, apochronaut!

I like this vintage device...I hope the old professors in microbiology lab sections did not use the device to closely observe their pupils from the front desk.

It is of interest to me just what the use was for this device...field work, or hobby use. Quite an instrument to enjoy. all the best, charlie guevara

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Re: Davon Micro-Telescope.

#9 Post by apochronaut » Wed Oct 28, 2015 2:57 pm

Thanks, Charlie. I doubt if this was used as a professional tool. Although the quality of the lenses is very good, it doesn't really meet the standards of either an excellent telescope or an excellent microscope for it's day.

The telescope objective has me confused. What would the reason be for a triplet, unless it was an apochromat? Would not a doublet have sufficed?

Someday, I will play with this a little more and see just exactly what it is capable of. Perhaps with a low power apochromat, it could be a decent spotting scope. There is an exterior thread on the objective, which seems as though it might take a shroud. If this went through the hole in the stage, it would block interference from extraneous rays, which the way it is set up now, are definitely there.

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gekko
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Re: Davon Micro-Telescope.

#10 Post by gekko » Fri Oct 30, 2015 3:06 am

apochronaut wrote:Pretty much. What they have done here is use a lens system to bring an image to focus at the microscope stage , rather than at an eyepiece. From there it is picked up and magnified by the microscope, rather than being picked up and magnified by the telescope eyepiece.
Essentially, the entire microscope is an extended eyepiece.
Thank you. That reminds me of a little pen-like simple microscope (Radio Shack I think) that many years ago I used to use to check the stylus of my record player for wear: It had an outer tube with a lens that slid over the microscope part to convert it into a telescope.

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Re: Davon Micro-Telescope.

#11 Post by apochronaut » Fri Oct 30, 2015 12:28 pm

I'm sure the principle would be the same, Gekko but due to the fact that this has interchangeable R.M.S. objectives, the microscope ( and telescope too) image is dependent on the quality of lenses and corrections in that objective. After I started this thread, I tried out a an older brass ,10x .25 achromat of known performance. Two things were striking: along the high contrast border, there was just an ever so slight amount of chroma visible and it gives a pretty sharp approx. 10-15X image. I tried an apochromat but it was worse, probably due to the eyepiece not being compensating. Presumably, whatever chroma is there, is the result of the objective being an achromat and the triplet telescope objective, actually provides a pretty well corrected, primary image.
As a microscope, it is good up to about 400X, without a condenser, with good quality achromats. In the telescope mode, the N.A. of the microscope objective is fairly irrelevant because it is receiving a focused beam of light. It is merely a series of lenses , doing a magnifying job and adding any aberrations it is prone to. It is the diameter of the telescope objective lens that determines the brightness of the image and at only 1 1/4" it is a pretty small diameter refractor.

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gekko
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Re: Davon Micro-Telescope.

#12 Post by gekko » Fri Oct 30, 2015 12:38 pm

apochronaut wrote:I'm sure the principle would be the same, Gekko but due to the fact that this has interchangeable R.M.S. objectives, the microscope ( and telescope too) image is dependent on the quality of lenses and corrections in that objective. After I started this thread, I tried out a an older brass ,10x .25 achromat of known performance. Two things were striking: along the high contrast border, there was just an ever so slight amount of chroma visible and it gives a pretty sharp approx. 10-15X image. I tried an apochromat but it was worse, probably due to the eyepiece not being compensating. Presumably, whatever chroma is there, is the result of the objective being an achromat and the triplet telescope objective, actually provides a pretty well corrected, primary image.
As a microscope, it is good up to about 400X, without a condenser, with good quality achromats. In the telescope mode, the N.A. of the microscope objective is fairly irrelevant because it is receiving a focused beam of light. It is merely a series of lenses , doing a magnifying job and adding any aberrations it is prone to. It is the diameter of the telescope objective lens that determines the brightness of the image and at only 1 1/4" it is a pretty small diameter refractor.
Many thanks, apochronaut. I am always fascinated by the inventiveness and ingenuity involved in making those old instruments (both optical and mechanical ones).

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