84 replies to this topic

[vietspace]

Rhomboid prism & my auxiliary telescope

 

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[vietspace]

My auxiliary telescope

Edited by vietspace, 19 May 2019 - 11:52 AM.

[vietspace]

 

A reticle paper at the focal plane of CPC 11in

 

[shredder1656]

IMG_0168.JPG

 

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 eyepiece

Anyway, 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

 

 

IMG_5196.JPG

My auxiliary telescope

 

 

IMG_6580.JPG

 

A reticle paper at the focal plane of CPC 11in

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!

[Ant1]

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

[vietspace]

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.

[Gordon Rayner]

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  (??).

[Cory Suddarth]

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

[Gordon Rayner]

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.

[phtz]

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