Jump to content

  •  

CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.

Photo

I think I have made a terrible mistake

  • Please log in to reply
8 replies to this topic

#1 decep

decep

    Mariner 2

  • *****
  • topic starter
  • Posts: 201
  • Joined: 19 Aug 2018
  • Loc: Griffin, Georgia

Posted 26 June 2020 - 08:03 PM

I little while back, I posted here about repairing a prism where the cement had started to become opaque.  https://www.cloudyni...cemented-prism/

 

I have recemented the prism, but it is not reflecting the image like it should be.  I estimate less than 1% of the light is being reflected where it should be ~50%.  Almost all light is being passed straight through.

 

I am starting to suspect there was a reflective coating on the right angle prism element in addition to the cement.

 

It is hard to google without knowing the right terms.  I am guessing the right angle prism I have is actually a "right angle prism mirror."  The stuff I thought was "coatings" were actually  a reflective coating as opposed to a anti-reflective coating?

 

post-299052-0-29145900-1590798114.jpg



#2 Eddgie

Eddgie

    ISS

  • *****
  • Posts: 26,318
  • Joined: 01 Feb 2006

Posted 26 June 2020 - 08:10 PM

If it is the lower prism it is called the beam splitter. There is a 50% reflective coating on one face.

 

https://en.wikipedia...wiki/Binoviewer


  • decep and Cali like this

#3 TOMDEY

TOMDEY

    Fly Me to the Moon

  • *****
  • Posts: 6,753
  • Joined: 10 Feb 2014
  • Loc: Springwater, NY

Posted 26 June 2020 - 08:48 PM

Well, decep... in the great scheme of things... the value is learning how things work, which you have accomplished. I'd save ~terrible mistake~ for such things as cutting off a finger and such. We tinkerers here have demolished more stuff than most people buy in a lifetime. Chalk it up to "destructive testing". I was a coating engineer/scientist for twelve years, and saw it all when it comes to coating abuse. We would get stuff back from customers, swearing up and down that the coating was somehow defective... with the blatant evidence they had decided to clean/refurbish something and ruined it. It's cool that you described what happened there.

 

Quality optical systems are generally serviceable, in the hands of certified experts... like my good friend Bill Cook. Guys with the training, tools, and experience doing that professionally for years/decades. For most of us hobbists here, the entry fee to exploratory surgery is that --- the patient may die... probably will die. But it's worth the risk of seeing what's inside!    Tom


  • Ken Sturrock, vtornado, PETER DREW and 1 other like this

#4 mashirts

mashirts

    Messenger

  • *****
  • Posts: 497
  • Joined: 18 Sep 2014
  • Loc: Elgin, TX

Posted 26 June 2020 - 09:34 PM

20mm cube 50/50 beam splitters are the largest size on Surplus shed at the moment. That is probably too small.


https://www.ebay.com/itm/203029064734

That is a 30mm 50/50 cube in ebay. That is about as good a deal for a non-wait-a-month shipping from china or Hong kong.

I am the only bidder now and not dying to have it, but at that price refuse to not at least try. I probably won't bid much more than the $24.

Good luck.

#5 decep

decep

    Mariner 2

  • *****
  • topic starter
  • Posts: 201
  • Joined: 19 Aug 2018
  • Loc: Griffin, Georgia

Posted 27 June 2020 - 11:34 AM

Well, decep... in the great scheme of things... the value is learning how things work, which you have accomplished. I'd save ~terrible mistake~ for such things as cutting off a finger and such. We tinkerers here have demolished more stuff than most people buy in a lifetime. Chalk it up to "destructive testing". I was a coating engineer/scientist for twelve years, and saw it all when it comes to coating abuse. We would get stuff back from customers, swearing up and down that the coating was somehow defective... with the blatant evidence they had decided to clean/refurbish something and ruined it. It's cool that you described what happened there.

 

Quality optical systems are generally serviceable, in the hands of certified experts... like my good friend Bill Cook. Guys with the training, tools, and experience doing that professionally for years/decades. For most of us hobbists here, the entry fee to exploratory surgery is that --- the patient may die... probably will die. But it's worth the risk of seeing what's inside!    Tom

Yeah, I meant "terrible mistake" more in the Arrested Development style than a true tragedy.

 

I do not think anything I have done here is truly permanent.  I will separate the lens elements again and will probably look for another beam splitter on eBay.

 

Astronomy is still primarily a DIY hobby, more so than many people think it should be.



#6 decep

decep

    Mariner 2

  • *****
  • topic starter
  • Posts: 201
  • Joined: 19 Aug 2018
  • Loc: Griffin, Georgia

Posted 27 June 2020 - 11:34 AM

If it is the lower prism it is called the beam splitter. There is a 50% reflective coating on one face.

 

https://en.wikipedia...wiki/Binoviewer

Its so obvious when you say it that way.  smile.gif



#7 decep

decep

    Mariner 2

  • *****
  • topic starter
  • Posts: 201
  • Joined: 19 Aug 2018
  • Loc: Griffin, Georgia

Posted 27 June 2020 - 11:39 AM

20mm cube 50/50 beam splitters are the largest size on Surplus shed at the moment. That is probably too small.


https://www.ebay.com/itm/203029064734

That is a 30mm 50/50 cube in ebay. That is about as good a deal for a non-wait-a-month shipping from china or Hong kong.

I am the only bidder now and not dying to have it, but at that price refuse to not at least try. I probably won't bid much more than the $24.

Good luck.

I am a patient guy.  I will hunt for a new beam splitter on eBay and get one eventually. 



#8 rob.0919

rob.0919

    Mariner 2

  • -----
  • Posts: 216
  • Joined: 26 Oct 2007
  • Loc: Derby , UK

Posted 27 June 2020 - 06:18 PM

Worth giving Denis a shout out....?

He's your man.

Georgia and Croatia are in the same ball park as well. Well, sort of......



#9 decep

decep

    Mariner 2

  • *****
  • topic starter
  • Posts: 201
  • Joined: 19 Aug 2018
  • Loc: Griffin, Georgia

Posted 27 June 2020 - 09:13 PM

Georgia and Croatia are in the same ball park as well. Well, sort of......

Its on the same planet, at least.  :-)
 




CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.


Recent Topics






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics