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

Bushnell Custom

  • Please log in to reply
6 replies to this topic

#1 asmart

asmart

    Explorer 1

  • -----
  • topic starter
  • Posts: 75
  • Joined: 31 Dec 2020

Posted 20 July 2021 - 01:13 PM

Are the old 10x50 Bushnell Custom's equiped with BAK4 prisms? How do they compare to todays low end Bak4 Porros?


Edited by asmart, 20 July 2021 - 01:32 PM.


#2 MartinPond

MartinPond

    Fly Me to the Moon

  • *****
  • Posts: 6,380
  • Joined: 16 Sep 2014

Posted 20 July 2021 - 01:29 PM

All customs I know of were made with BAK4, Barium crown glass,

    with a low bubble density.  I wouldn't expect that to be any different

    in old vs. new times.

 

BaK4 (note the lower case a) or Bak4 is a Chinese Phosphate glass,

     basically PSK4 Schott glass. It has a lower index than BAK4.

     Chinese BaK4 has twice the allowed bubble density of normal PSK4.

     I would expect that to be the more important quality loss.

     I'd prefer well-done BK7 to that, contrast-wise, and even dispersion-wise.


Edited by MartinPond, 20 July 2021 - 01:32 PM.

  • WALL.E likes this

#3 pat in los angeles basin

pat in los angeles basin

    Apollo

  • *****
  • Posts: 1,033
  • Joined: 20 Nov 2015

Posted 20 July 2021 - 01:39 PM

"How do they compare to todays low end Bak4 Porros?" A little more specific? I have 2, and they are a great bino. If you have the  possibility of getting one at a reasonable price ($100-150). I wouldn't hesitate. Even with the simple coatings, they put  out a great image with very good focus. A couple caveats- weighty and  the eyecups are fragile. I bought both pairs used and both looked like they had a hard life (likely hunting) but both are above reproach in their operation. I'm looking for a third one BTW!!    Pat



#4 pat in los angeles basin

pat in los angeles basin

    Apollo

  • *****
  • Posts: 1,033
  • Joined: 20 Nov 2015

Posted 20 July 2021 - 01:40 PM

Yes they are BaK4 BTW. Pat



#5 asmart

asmart

    Explorer 1

  • -----
  • topic starter
  • Posts: 75
  • Joined: 31 Dec 2020

Posted 20 July 2021 - 01:41 PM

Thanks for the info. After you posted I googled and ran accross the following.

 

This is what you should know: the "BAK4" glass used for the prisms of Chinese binoculars is not the same as Schott BaK4 – and it's not just the upper-case letter ‘A’ that's different. In fact, it's not even Barium Crown, which is what BaK stands for! It is a phosphate crown glass with a lower refractive index and dispersion than Schott BaK4 (but higher than BK7). It also potentially has a higher "bubble count"; this is noticeable as a slight milkinesss to the image when compared with good quality glass.

 

In practice, this may not be all bad. Unless you have very wide-angle binoculars, you are unlikely to notice the effect of the lower refractive index, and the lower dispersion than "real" BaK4 means that there may be less dispersion in the image (not that you are likely to be able to see it). The potentially higher bubble-count means there will be more light scatter inside the prism.

 

This is from : https://binocularsky...c_minefield.php

 

 



#6 asmart

asmart

    Explorer 1

  • -----
  • topic starter
  • Posts: 75
  • Joined: 31 Dec 2020

Posted 20 July 2021 - 01:42 PM

So Bushnell Customs are probably good binoculars assuming they are in good shape. I appreciate the info greatly.


Edited by asmart, 20 July 2021 - 01:57 PM.


#7 MartinPond

MartinPond

    Fly Me to the Moon

  • *****
  • Posts: 6,380
  • Joined: 16 Sep 2014

Posted 20 July 2021 - 03:47 PM

Customs are excellent.

They almost all use a 1,1,2 eyepiece,

which has a little wider field a a lot more comfortable eye placement.

And other touches..




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.







Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics