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Equipment Discussions >> Binoviewers

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HowardK
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TEC 140 and MK V bino.....
      #6135284 - 10/13/13 03:50 PM

I read on the Astro Physics site this.....concerning fast refractors, mk v binos and a Baader glasspath compensator.....

Removable 1.25x Compensating Optical Element - This optical element eliminates the slight color error and spherical aberration that a prism beam splitter naturally introduces into the light path of all binocular viewers. It allows you to enjoy wide-field, low-power views of deep-sky objects, as well as high powers. This element (also known as a Glasspath Compensator) was designed by Roland Christen of Astro-Physics and is essential for telescopes with fast focal ratios. One of these optics should always be part of the optical path of telescopes with fast focal ratiosunless a BARADV or BPFFC is used.....

My TEC is f/7 and i enjoy her with a Baader prism diagonal and MK V binos.

Does the forum think i really need to use a 1.25x GPC with this setup?


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crazyqban
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Re: TEC 140 and MK V bino..... new [Re: HowardK]
      #6135289 - 10/13/13 03:53 PM

I have used my Mark Vs with and without the 1.25 GPC as suggested and I really cannot see any difference. I usually keep it in there and take it out if I need a little extra FOV.

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HowardK
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Re: TEC 140 and MK V bino..... new [Re: crazyqban]
      #6135299 - 10/13/13 03:58 PM

Ty Sergio

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Eddgie
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Re: TEC 140 and MK V bino..... new [Re: HowardK]
      #6136524 - 10/14/13 09:47 AM

I think that in a Televue 101 or similar fast scopes, the GPC might be beneficial. At f/7 or f/8, I think it is less cricitical.

For really fast scopes though I think that it might be best to use the Max mirror and the GPC (Televue 101 maybe).

If you can reach focus without it though I think you will prefer the ability to get lower powers and wider fields.

And for planets, you can always put in the GPC. This is the only time it would likely make a difference, though I am not convinced that it would.

And if you are using them and have not noticed anything wrong then that by itself should be all you need, yes???

Edited by Eddgie (10/14/13 11:12 AM)


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tomcody
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Re: TEC 140 and MK V bino..... new [Re: HowardK]
      #6136674 - 10/14/13 11:09 AM

Astro Physics recommends using a GPC or barlow, to correct aberrations in the prisms and I have noticed some off axis color (for want of a better word ) flashes if my eyes are not exactly centered when not using one and I remember reading that Dennis0007 (in another thread) also reported the same need to keep his eyes centered when not using GPC's. Now if the slight color flashes do not bother you? then of course you do not need the GPC's.
Rex


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Astrojensen
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Re: TEC 140 and MK V bino..... new [Re: tomcody]
      #6138310 - 10/15/13 03:36 AM

For critical lunar/planetary/solar observing, using a GPC can be beneficial. For wide-field deep-sky and low magnification observing, it's not important and can safely be ignored.


Clear skies!
Thomas, Denmark


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HowardK
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Re: TEC 140 and MK V bino..... new [Re: Astrojensen]
      #6138493 - 10/15/13 08:17 AM

Ty

Thomas


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HowardK
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Re: TEC 140 and MK V bino..... new [Re: HowardK]
      #6140216 - 10/16/13 02:02 AM

This from Yuri at TEC as stated from BAADER....

Hi Howard, here is the answer from Baader planetarium:
"The Mark V Bino has about 100mm of glasspath and every customer using our bino in conjunction with a refractive optics faster than f/8 ABSOLUTELY needs that 1.25x Glasspath-compensator. This is the correct answer".

Regards, Yuri


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Astrojensen
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Re: TEC 140 and MK V bino..... new [Re: HowardK]
      #6140252 - 10/16/13 03:48 AM

For critical observing, yes. For wide-field observing, where you're far below the diffraction limit, not at all. I do HIGHLY recommend using them or a barlow, when doing lunar/planetary observing, though.

Just stating the obvious.


Clear skies!
Thomas, Denmark


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HowardK
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Re: TEC 140 and MK V bino..... new [Re: Astrojensen]
      #6140403 - 10/16/13 08:16 AM

I'm going to keep my 1.25x GPC in my MK V binos.

Thanks
Thomas


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Astrojensen
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Re: TEC 140 and MK V bino..... new [Re: HowardK]
      #6140409 - 10/16/13 08:23 AM

I often observe without a GPC and can't notice a difference at low magnification whatsoever, apart from the fact that I'm getting 20% wider field. This is also true on my f/6 and f/8 refractors.


Clear skies!
Thomas, Denmark


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HowardK
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Re: TEC 140 and MK V bino..... new [Re: Astrojensen]
      #6141049 - 10/16/13 02:36 PM


I have now installed the Baader 1.25 GPC on my MK V Baader binoviewers and this setup has completely removed the colour fringing i was seeing on the moon thru my TEC 140 with the binoviewers and no GPC.....at higher magnifications

Am very happy


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DaveJ
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Re: TEC 140 and MK V bino..... new [Re: HowardK]
      #6141086 - 10/16/13 02:55 PM

Quote:


I have now installed the Baader 1.25 GPC on my MK V Baader binoviewers and this setup has completely removed the colour fringing i was seeing on the moon thru my TEC 140 with the binoviewers and no GPC.....at higher magnifications

Am very happy




I've experienced the exact same thing with my TEC 140 and MarkV binoviewers. I still use the MarkV without the GPC for low-power Milkyway sweeps with the 24mm Panoptics and that's a great view, too! Still, absolutely color-free high-power views of the Moon and planets with the 1.25 GPC is to die for. It's great to be able to have both with such a simple few-second conversion.


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HowardK
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Re: TEC 140 and MK V bino..... new [Re: DaveJ]
      #6141218 - 10/16/13 04:23 PM

Yes Dave

U r right


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HowardK
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Re: TEC 140 and MK V bino..... new [Re: HowardK]
      #6141225 - 10/16/13 04:25 PM

Although removing the GPC means racking the focuser in about 15mm ...which buggers up my perfect balance on my az eq6 mount!

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HowardK
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Re: TEC 140 and MK V bino..... new [Re: HowardK]
      #6141228 - 10/16/13 04:26 PM

I use a pair of 3-6mm Nagler zooms

How about u?


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DaveJ
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Re: TEC 140 and MK V bino..... new [Re: HowardK]
      #6141234 - 10/16/13 04:30 PM

Quote:

I use a pair of 3-6mm Nagler zooms.
How about u?




I have pairs of every single 1.25" eyepiece in my sig, and a whole bunch more that aren't listed. However, and this is sad, I don't have a pair of the 3-6mm Nagler zooms. I have the one and need to get another one to match!


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Astrojensen
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Re: TEC 140 and MK V bino..... new [Re: HowardK]
      #6141235 - 10/16/13 04:30 PM

I am currently comparing my 2.6x GPC and a 2" 2x GSO barlow, which gives very close to the same magnification, when the lens cell is attached to the 2" nosepiece on the Maxbright. So far, it seems the GSO barlow is actually brighter, sharper and has less color fringing than the 2.6x GPC, but I've only compared them twice so far, and the seeing wasn't too cooperative in either case. I was using my Telemator and 6" f/8 achromat, stopped to 112mm f/10.7, respectively, so it might be that the GSO changes the color correction better than the GPC does. I will need to try them on the newtonian. It's been a long time since I observed the Moon with the 12" dob, but from memory, the 2.6x GPC was color free in that scope.


Clear skies!
Thomas, Denmark


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Astrojensen
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Re: TEC 140 and MK V bino..... new [Re: Astrojensen]
      #6141238 - 10/16/13 04:32 PM

Also need to do some color comparisons with stacked GPCs.


Clear skies!
Thomas, Denmark


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HowardK
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Re: TEC 140 and MK V bino..... new [Re: DaveJ]
      #6141252 - 10/16/13 04:39 PM

Quote:

Quote:

I use a pair of 3-6mm Nagler zooms.
How about u?




I have pairs of every single 1.25" eyepiece in my sig, and a whole bunch more that aren't listed. However, and this is sad, I don't have a pair of the 3-6mm Nagler zooms. I have the one and need to get another one to match!





Do it man


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Keith-in-Texas
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Re: TEC 140 and MK V bino..... new [Re: HowardK]
      #6142059 - 10/16/13 11:37 PM

I read in an older thread on the Mark V bino that using it without a GPC can cause some unwanted reflections due to the GPC not being present to cover some highly reflective internal components.

In the same thread there was mention by some they purchased an extra GPC and removed the optics and used the GPC without optics to eliminate the internal reflections.

I always use a GPC in my Mark V to avoid this potential issue.

Best regards,

Keith


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Stellarfire
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Reged: 07/10/11

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Re: TEC 140 and MK V bino..... new [Re: Keith-in-Texas]
      #6144986 - 10/18/13 02:20 PM

Yes, the Mark V with empty GPC's is discussed here (see posts #6081488 - 15/09/13 03:50 AM, and #5664676 - 06/02/13 06:02 AM)

I am the Swiss guy who uses two Baader Mark V binoviewers without GPC's.
I do this since I consider the small GPC's as the potentially weakest part in the entire optical train. My 6" f/7.3 APO refractor / Mark V combo comes with most eyepieces to focus without a GPC. So - in this particular case - to me there is no real need for a GPC. I therefore use both Mark V's with empty black GPC frames put in place. This way the chromed ring on inside of the Mark V just behind the T-2 Quick Changer is covered and no reflections are degrading the image.

For high power observations, the wanted increased focal length is achieved by a 2" Powermate, an A-P BARCON or BARADV, or the Baader FFC. Any additional GPC in the light path makes no sense to me.


Stephan


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t.r.
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Re: TEC 140 and MK V bino..... new [Re: Stellarfire]
      #6145062 - 10/18/13 03:03 PM

If I remember correctly the old Barcon barlow acts as a 1.7x compensator, correct?

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mark8888
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Reged: 09/24/10

Re: TEC 140 and MK V bino..... new [Re: Stellarfire]
      #6145096 - 10/18/13 03:27 PM

Quote:

I do this since I consider the small GPC's as the potentially weakest part in the entire optical train.




I'm interested in this comment, including "potentially"... have you compared the views using the GPCs (for example the 1.7) to views using a BARCON or BARADV (without a GPC installed) and found that the GPCs are inferior? If so, how? Or are you assuming that the view would somehow be worse because they are so small?


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Stellarfire
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Reged: 07/10/11

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Re: TEC 140 and MK V bino..... new [Re: t.r.]
      #6145124 - 10/18/13 03:47 PM

In combination with the long light path of the Mark V binoviewer, the BARCON (placed in front of the diagonal) yields slightly over 2.5x

Tammy provided us with following BARCON focal ratio figures when used without additional GPC (see his post #5664099 - 05/02/13 06:14 PM):

Quote:


2.52x BARCON-AP16T-T2Mirror-QC-MarkV-Delos-10

2.59x BARCON-AP16T-T2Mirror-QC-MarkV-Docter-UWA-12.5




Stephan


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Stellarfire
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Reged: 07/10/11

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Re: TEC 140 and MK V bino..... new [Re: mark8888]
      #6145180 - 10/18/13 04:24 PM

Quote:

Quote:

I do this since I consider the small GPC's as the potentially weakest part in the entire optical train.




I'm interested in this comment, including "potentially"... have you compared the views using the GPCs (for example the 1.7) to views using a BARCON or BARADV (without a GPC installed) and found that the GPCs are inferior? If so, how? Or are you assuming that the view would somehow be worse because they are so small?




I use most of the time a T-2 Prism Diagonal and prefer to achieve the desired focal length before the diagonal, instead of afterwards (as a GPC does).

And yes, your last line describes exactly what I am thinking. Looking at the small dimensions of the 2-element lens of the GPC which sells at $118.00 retail, one can imagine the required high level of precision and polish of this critical part...
I did some comparos on Luna and found that differences with GPC against no GPC (substituted by a high quality Barlow or Powermate element placed in front of diagonal) are subtle, but become visible at high powers over 400x. At low powers, there is no visible difference of image quality.

Stephan

Edited by Stellarfire (10/19/13 02:30 AM)


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RAKing
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Re: TEC 140 and MK V bino..... new [Re: t.r.]
      #6145282 - 10/18/13 05:28 PM

Quote:

If I remember correctly the old Barcon barlow acts as a 1.7x compensator, correct?




That is correct if you just use it as a Barlow with an eyepiece.

For binoviewing, we unscrew the Barcon from the eyepiece holder and thread it directly to the front of the T2 diagonal - replacing the AP nosepiece. Used this way, the Barcon was said to achieve a 2.4x magnification factor.

It looks like Tammy is keeping the AP nosepiece in place and threading the Barcon to the front of that, which will boost the magnification factor even more.

Cheers,

Ron


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tomcody
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Re: TEC 140 and MK V bino..... new [Re: Stellarfire]
      #6146257 - 10/19/13 09:14 AM

Quote:

Quote:

Quote:

I do this since I consider the small GPC's as the potentially weakest part in the entire optical train.




I'm interested in this comment, including "potentially"... have you compared the views using the GPCs (for example the 1.7) to views using a BARCON or BARADV (without a GPC installed) and found that the GPCs are inferior? If so, how? Or are you assuming that the view would somehow be worse because they are so small?




I use most of the time a T-2 Prism Diagonal and prefer to achieve the desired focal length before the diagonal, instead of afterwards (as a GPC does).

And yes, your last line describes exactly what I am thinking. Looking at the small dimensions of the 2-element lens of the GPC which sells at $118.00 retail, one can imagine the required high level of precision and polish of this critical part...
I did some comparos on Luna and found that differences with GPC against no GPC (substituted by a high quality Barlow or Powermate element placed in front of diagonal) are subtle, but become visible at high powers over 400x. At low powers, there is no visible difference of image quality.

Stephan



I also notice a small difference in quality of view in favor of the Barcon over the GPC when using a Baader/ Ziess prism, I was wondering why? but now I think it is not a quality difference between the Barcon and GPC, rather only a difference of magnifying before or after the prism!
I also do not notice any difference between the two when using a Maxbright mirror instead of the prism.
Rex


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