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TEC 140 and MK V bino.....

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#1 HowardK

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Posted 13 October 2013 - 02:50 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?

#2 crazyqban

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Posted 13 October 2013 - 02:53 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.

#3 HowardK

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Posted 13 October 2013 - 02:58 PM

Ty Sergio

#4 Eddgie

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Posted 14 October 2013 - 08:47 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???

#5 tomcody

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Posted 14 October 2013 - 10:09 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

#6 Astrojensen

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Posted 15 October 2013 - 02:36 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

#7 HowardK

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Posted 15 October 2013 - 07:17 AM

Ty

Thomas

#8 HowardK

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Posted 16 October 2013 - 01:02 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

#9 Astrojensen

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Posted 16 October 2013 - 02:48 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

#10 HowardK

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Posted 16 October 2013 - 07:16 AM

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

Thanks
Thomas

#11 Astrojensen

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Posted 16 October 2013 - 07:23 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

#12 HowardK

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Posted 16 October 2013 - 01:36 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

#13 DaveJ

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Posted 16 October 2013 - 01:55 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


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. :grin:

#14 HowardK

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Posted 16 October 2013 - 03:23 PM

Yes Dave

U r right

#15 HowardK

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Posted 16 October 2013 - 03:25 PM

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

#16 HowardK

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Posted 16 October 2013 - 03:26 PM

I use a pair of 3-6mm Nagler zooms

How about u?

#17 DaveJ

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Posted 16 October 2013 - 03:30 PM

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!

#18 Astrojensen

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Posted 16 October 2013 - 03:30 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

#19 Astrojensen

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Posted 16 October 2013 - 03:32 PM

Also need to do some color comparisons with stacked GPCs.


Clear skies!
Thomas, Denmark

#20 HowardK

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Posted 16 October 2013 - 03:39 PM

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

#21 Keith-in-Texas

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Posted 16 October 2013 - 10:37 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

#22 Stellarfire

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Posted 18 October 2013 - 01:20 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

#23 t.r.

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Posted 18 October 2013 - 02:03 PM

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

#24 mark8888

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Posted 18 October 2013 - 02:27 PM

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?

#25 Stellarfire

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Posted 18 October 2013 - 02:47 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):

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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