Rhomboid prism & my auxiliary telescope
Posted 19 May 2019 - 06:23 PM
I almost finished my collimator
Today I received a 3-9x40 rifle scope to make the auxiliary telescope, but it’s too long and heavy so it's too difficult to stabilize behind binoculars eyepieceAnyway, I think I have all things to complete my collimator. In the next few days I will complete the test stand and consider whether I can replace a lighter auxiliary telescope.
I use a Celestron CPC 11in for collimator tube with a reticle at focal plane
Rhomboid prism ~ 50 usd from a Vietnamese optical company
A Vixen Az-Alt adjustment for Test stand
Rhomboid prism & my auxiliary telescope
My auxiliary telescope
Nice work!!!
I knew someone would get one put together. I just need TIME. This contraption is not that difficult. Bill did everyone a favor by offering these tricks and details to the masses, in my opinion. I will post pics when mine is done too.
Nice work with the aux scope. Keep at it!
Posted 20 May 2019 - 02:03 AM
Hi
From your picture in post #75 I'm not sure how your mounts are attached to the table?
Be careful that any movement of the binocular support relative to the telescope will ruin your efforts.
I have myself wasted some effort trying to troubleshoot such a setup before realizing target and binoculars were drifting relative to each other during the collimation process.
Regards,
Ant1
Posted 20 May 2019 - 03:17 AM
Hi
From your picture in post #75 I'm not sure how your mounts are attached to the table?
Be careful that any movement of the binocular support relative to the telescope will ruin your efforts.
I have myself wasted some effort trying to troubleshoot such a setup before realizing target and binoculars were drifting relative to each other during the collimation process.
Regards,
Ant1
Sure, Ant1.
I only used the camera tripod to check auxiliary scope function.
The next day, I will make a stable test stand based on the Vixen Az-Alt adjustment.
Posted 04 June 2019 - 06:06 PM
I have used 5 x 20 golf scopes as auxiliary telescopes, combined with JTII beam combiners or equivalents, for Navy-style use. 5X is a bit high for rapid freehand use, but motion damping elbow pads on an armrest can help. I made adapters for Navy (1923) 3X auxiliary scopes to JTII and to other, approximately equivalent , rhomboidal beam combiners. Search "Dinka" and /or "Nuer" for pictures .
Hanna in ATM II or III shows a mounted Navy style auxiliary scope with peek-around rhomboid attachment. Freehand was common practice among Navy OMs. During WW II, Hanna and his crew work closely with the Mare Island optics repair people. ?????
Golf scopes can be used to measure the angular sizes of features of real or simulated distant targets. To convert golf hole ranges on its reticle to angular quantities, use a military or nautical binocular with a mil scale in one eyepiece, a transit, or a theodolite from a friendly surveyor. A little bit of easy trigonometry might be useful, if needed.
IIRC, the golf scope reticle ranges use hole marker pole height as a constant (??).
Posted 22 July 2019 - 09:28 AM
Made one this weekend!
Hopes dashed so far... I was really wanting this to work. For BC, for us all. An affordable collimator for the masses! How cool would that be?!
I re-read post #19. Not sure why an apology was needed, Ant1 shows the problem well. The Spherical aberration caused by the Fresnel lens is awful! The first thing I did was focus a binocular at distance. I used a Bausch & Lomb 8x30, then attempted to focus the screen and Fresnel lens to the binoculars distant setting. You just can't get a clean, sharp focus, not gonna happen! Clean focus, Tack sharp, Crisp, all words used to describe good resolving characteristics. If those words are acceptable for good resolution, the word garbage comes to mind for this set up. I have another Fresnel lens coming, hoping that the one I just tested was a dud. This Fresnel not only has spherical (expected), it also caused a notable degree of step on an otherwise perfectly collimated glass! The degree of step varied depending on where I lined the glass up (side-to-side and up-and-down). A total deal breaker! Hopefully, next lens will perform without causing step. Just for the record, step was very evident visually, and ,I did not use an auxiliary scope to detect. Not being able to reach a focus at 8x, can't imagine what it will look like at 24x with the aux-scope. It's kinda like writing a letter, but, instead of using pen and paper, you are given a sheet of paper, bucket of black paint, and a brick to write with.
Cory
Posted 25 July 2019 - 07:23 PM
What about the 2-axis adjustable fixture question I asked in in #69 and #71, above, and before? That is, when using the C 14 or C8 in reverse, as target collimator sources of artificial targets at infinity distance, do you transfer the fixture from the Mk. 5 for use with the Celestron reversed telescopes? Or??
Look at the 2-angle adjustable milling/grinding rotary fixtures/tables in Travers or Manhattan Supply, etc. Stable without a doubt, and repeatable. I have two Leitz 2 second optical dividing heads, ca. 125 pounds each. Certainly stable, but overkill for adjusting binoculars.
I have some Gaertner lathe bed style optical benches, with various attachments, which could be used for stable, albeit heavy equipment applicable to this thread's topic, or to the various other applications for which they are suitable, as described in detail by Horace Selby in ATM III.
Also have a big Ealing optical bench with, IIRC, a carriage. Heavy, 7 1/2 feet in length, lathe bed style bench. Some superficial rust.
But I have never used these optical benches. Good for precise measurement of focal length, radii, node location ( via the nodal slide), etc.
Edited by Gordon Rayner, 26 July 2019 - 02:58 PM.
Posted 20 May 2020 - 06:08 AM
Hello
I’m making the auxiliary telescope, I’ll interested to know the beam tolerance of the rhomboid.
Vietspace or Cory, what is your requested tolerance?
thanks
Phil
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