Jump to content


Photo

How small is too small?

  • Please log in to reply
21 replies to this topic

#1 DavidNealMinnick

DavidNealMinnick

    Ranger 4

  • *****
  • Posts: 360
  • Joined: 06 Mar 2006

Posted 19 May 2013 - 09:28 PM

Borg makes some small EDs, down to 45mm. This is the Pocket Borg, a 25mm f/7 achromat.

Attached Files



#2 DavidNealMinnick

DavidNealMinnick

    Ranger 4

  • *****
  • Posts: 360
  • Joined: 06 Mar 2006

Posted 19 May 2013 - 09:29 PM

Focus is achieved by sliding the lens section.

Attached Files



#3 DavidNealMinnick

DavidNealMinnick

    Ranger 4

  • *****
  • Posts: 360
  • Joined: 06 Mar 2006

Posted 19 May 2013 - 09:31 PM

With diagonal.

Attached Files



#4 DavidNealMinnick

DavidNealMinnick

    Ranger 4

  • *****
  • Posts: 360
  • Joined: 06 Mar 2006

Posted 19 May 2013 - 09:31 PM

Cell.

Attached Files



#5 DavidNealMinnick

DavidNealMinnick

    Ranger 4

  • *****
  • Posts: 360
  • Joined: 06 Mar 2006

Posted 19 May 2013 - 09:32 PM

Handy.

Attached Files



#6 DavidNealMinnick

DavidNealMinnick

    Ranger 4

  • *****
  • Posts: 360
  • Joined: 06 Mar 2006

Posted 19 May 2013 - 09:34 PM

Where do I attach the finder?

Attached Files



#7 Scott in NC

Scott in NC

    80mm Refractor Fanatic

  • *****
  • Administrators
  • Posts: 15191
  • Joined: 05 Mar 2005
  • Loc: NC

Posted 19 May 2013 - 10:37 PM

Now that's small. I don't recall ever seeing a scope that was dwarfed by a Plossl before! :lol:

#8 Koala117

Koala117

    Mariner 2

  • -----
  • Posts: 205
  • Joined: 11 May 2013

Posted 19 May 2013 - 10:44 PM

Wow, that's just tiny!

What would one use this for, if not a finder scope? That is.. with a 25mm it's what, 7x magnification. Would the light-gathering ability be worth-while?

I did try to google it but only found the 45mm. What would this cost? Not that I'd buy one, I'm just curious. o:

#9 Jon Isaacs

Jon Isaacs

    ISS

  • *****
  • Posts: 43583
  • Joined: 16 Jun 2004
  • Loc: San Diego and Boulevard, CA

Posted 19 May 2013 - 10:48 PM

Borg makes some small EDs, down to 45mm. This is the Pocket Borg, a 25mm f/7 achromat.


David:

Have you tried it yet?

Jon

#10 Astrojensen

Astrojensen

    Fly Me to the Moon

  • *****
  • Posts: 5117
  • Joined: 05 Oct 2008
  • Loc: Bornholm, Denmark

Posted 20 May 2013 - 02:39 AM

I've tried my WO 72ED stopped down to 25mm and it's possible to see surprisingly much. From a dark sky, many Messier objects and even quite a few NGCs are visible.


Clear skies!
Thomas, Denmark

#11 Derek Wong

Derek Wong

    Messenger

  • *****
  • Posts: 403
  • Joined: 27 Apr 2008
  • Loc: Glendale, CA

Posted 20 May 2013 - 02:50 AM

Borg makes some small EDs, down to 45mm. This is the Pocket Borg, a 25mm f/7 achromat.


This is a nice little scope, would love to hear about it. See here for a photo of it with an erecting prism:

http://www.tomytec.c...ail/summary/9/1

If you put an Ethos 13 in the diagonal, you could carry the setup by the eyepiece...

Derek

#12 csrlice12

csrlice12

    Voyager 1

  • *****
  • Posts: 10588
  • Joined: 22 May 2012
  • Loc: Denver, CO

Posted 20 May 2013 - 08:21 AM

.....and, it's reversable, you can look thru either end! :lol:

#13 chaoscosmos

chaoscosmos

    Mariner 2

  • *****
  • Posts: 247
  • Joined: 26 Jan 2013
  • Loc: Mission Viejo CA

Posted 20 May 2013 - 10:35 AM

Why? oh why? I say. :roflmao:

#14 Koala117

Koala117

    Mariner 2

  • -----
  • Posts: 205
  • Joined: 11 May 2013

Posted 20 May 2013 - 12:04 PM

I've tried my WO 72ED stopped down to 25mm and it's possible to see surprisingly much. From a dark sky, many Messier objects and even quite a few NGCs are visible.


Hi, Thomas =)

I wonder: Would that be an equal comparison? That is to say, wouldn't your 72 have a much longer focal ratio, and as such, have much more magnification? Or am I misunderstanding what 'stopped down' means... (which is possible since I'm still learning!)

#15 t.r.

t.r.

    Skylab

  • *****
  • Posts: 4417
  • Joined: 14 Feb 2008
  • Loc: 1123,6536,5321

Posted 20 May 2013 - 12:28 PM

Thats ridiculous...I too ask, Why???

#16 Jon Isaacs

Jon Isaacs

    ISS

  • *****
  • Posts: 43583
  • Joined: 16 Jun 2004
  • Loc: San Diego and Boulevard, CA

Posted 20 May 2013 - 01:00 PM

I've tried my WO 72ED stopped down to 25mm and it's possible to see surprisingly much. From a dark sky, many Messier objects and even quite a few NGCs are visible.


Hi, Thomas =)

I wonder: Would that be an equal comparison? That is to say, wouldn't your 72 have a much longer focal ratio, and as such, have much more magnification? Or am I misunderstanding what 'stopped down' means... (which is possible since I'm still learning!)


The 72ED probably has a focal length of about 430mm, this 25mm scope is F/7 so it has a focal length of 175mm, so indeed, using the same eyepiece, the magnification would be considerably greater with the stopped down 72mm. You would have to use different eyepieces if you wanted to do a side by side comparison.

I have to think a 25mm scope is more of a curiosity than a practical tool. One could increase the aperture to 35mm and keep the focal ratio at F/5 without compromise.

Jon

#17 Koala117

Koala117

    Mariner 2

  • -----
  • Posts: 205
  • Joined: 11 May 2013

Posted 20 May 2013 - 01:09 PM

The 72ED probably has a focal length of about 430mm, this 25mm scope is F/7 so it has a focal length of 175mm, so indeed, using the same eyepiece, the magnification would be considerably greater with the stopped down 72mm. You would have to use different eyepieces if you wanted to do a side by side comparison.

I have to think a 25mm scope is more of a curiosity than a practical tool. One could increase the aperture to 35mm and keep the focal ratio at F/5 without compromise.

Jon


Ahh, okay! I understand a little better now. =)

I did manage to find a picture/article of it that someone else posted on the internet, for those interested:
http://digiborg.word...org-h2b-rocket/

#18 csrlice12

csrlice12

    Voyager 1

  • *****
  • Posts: 10588
  • Joined: 22 May 2012
  • Loc: Denver, CO

Posted 20 May 2013 - 02:15 PM

could you swap out the focuser for 2" eyepieces??? Think of the FOV!! Put an old nonwaterproof ES82 30mm on it!! (truely doubtful you'd see anything, but hey, we can all imagine!) :lol:

A serious question though, what was this "scope" designed for???

#19 Astrojensen

Astrojensen

    Fly Me to the Moon

  • *****
  • Posts: 5117
  • Joined: 05 Oct 2008
  • Loc: Bornholm, Denmark

Posted 20 May 2013 - 03:04 PM

could you swap out the focuser for 2" eyepieces??? Think of the FOV!!



I'm saying only two words: Field curvature!


Clear skies!
Thomas, Denmark

#20 Astrojensen

Astrojensen

    Fly Me to the Moon

  • *****
  • Posts: 5117
  • Joined: 05 Oct 2008
  • Loc: Bornholm, Denmark

Posted 20 May 2013 - 03:12 PM

Hi, Thomas =)

I wonder: Would that be an equal comparison? That is to say, wouldn't your 72 have a much longer focal ratio, and as such, have much more magnification? Or am I misunderstanding what 'stopped down' means... (which is possible since I'm still learning!)



As Jon already pointed out, aperture for aperture, the comparison is fair, but the eyepieces will need to be of much longer focal length in order to get comparable magnifications. Also, the stopped down scope with the longer focal length is more or less guaranteed to have superior optics, especially in terms of color correction, but also most likely much better spherical correction.

With the optics stopped down to 25mm f/17.2, my WO72 has an absolutely perfect star test and double stars (the ones it can resolve that is!) are amazingly perfect. I've never seen so crisp low-power fields either. A bit dim, but extremely sharp. Quite lot of things visible, if one care to look.


Clear skies!
Thomas, Denmark

#21 DavidNealMinnick

DavidNealMinnick

    Ranger 4

  • *****
  • Posts: 360
  • Joined: 06 Mar 2006

Posted 21 May 2013 - 07:31 PM

Borg makes some small EDs, down to 45mm. This is the Pocket Borg, a 25mm f/7 achromat.


David:

Have you tried it yet?

Jon


Jon, yes, I used the 25 Plossl as the finding ep and a 6 Expanse, barlowed, yielding almost 60x. Enough to show Saturn's rings. Finding anything becomes part of the challenge with it, and of course its utility is rather limited, but it adds another dimension to the hobby. And is quite portable!

#22 DavidNealMinnick

DavidNealMinnick

    Ranger 4

  • *****
  • Posts: 360
  • Joined: 06 Mar 2006

Posted 21 May 2013 - 07:38 PM

Wow, that's just tiny!

What would one use this for, if not a finder scope? That is.. with a 25mm it's what, 7x magnification. Would the light-gathering ability be worth-while?

I did try to google it but only found the 45mm. What would this cost? Not that I'd buy one, I'm just curious. o:

I have all my Borg receipts except this one, and don't recall how much it was. I would have to call up Ted Ishikawa at Hutech to remind me. I've had it a few years, now, and take it out now and again.






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics