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Some Handy Measurements

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#1 Jeff B

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Posted 24 January 2020 - 03:51 PM

I though you all might be interested in this info as many of us have the AP and Baader BBHS and Zeiss spec prism diagonals (with the T2 quick changer system).  

 

Using my DPAC test set up, I directly measured some interesting stuff.

 

1. AP diagonal has a 105mm light path from the front face to the top of the diagonal.

 

2. The Baader BBHS silver diagonal has a light path of 51mm from the front face to the diagonal to the top of the T2 quick changer

 

3. The  Baader Zeiss spec prism diagonal has a light path of 39mm from the front face of the diagonal to the top of the T2 quick changer.

 

4. With the 1.25X  and 1.7x GPCs screwed into the bottom of my Zeiss 30mm CA viewer, I needed to rack the focuser out an additional 21.2mm and 38.8mm respectively, on average, for all three diagonals.

 

Regarding number 4, when you reverse the GPC elements and put them into the quick changers rather than into the bottom of the viewer as I did,  those differences in focuser rack out will be slightly larger, maybe a couple of mm's,  as they are slightly further away from the focal plane in that configuration, giving them slightly more magnification.

 

Jeff


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#2 Eddgie

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Posted 24 January 2020 - 06:19 PM

Very nice work.

 

These figures are pretty close to what Baader provides in the Maxbright Owners Manual and Alpine (for the diagonal light path measurements).

 

Baader is usually pretty good about this stuff, but the big question mark is why the 1.7x and repeatedly been reported to only be giving about 1.5x.  Now most people would be happy if they can still reach focus, but again, Baader is usually pretty close on specs for light path lengths, so surprised about the miss on this other kind of important spec for the .1.7x..

 

Nicely done though.  Actual measurements are always good.


Edited by Eddgie, 24 January 2020 - 06:25 PM.

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#3 Jeff B

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Posted 24 January 2020 - 07:06 PM

Very nice work.

 

These figures are pretty close to what Baader provides in the Maxbright Owners Manual and Alpine (for the diagonal light path measurements).

 

Baader is usually pretty good about this stuff, but the big question mark is why the 1.7x and repeatedly been reported to only be giving about 1.5x.  Now most people would be happy if they can still reach focus, but again, Baader is usually pretty close on specs for light path lengths, so surprised about the miss on this other kind of important spec for the .1.7x..

 

Nicely done though.  Actual measurements are always good.

Thanks Eddgie.

 

Yeah, I've noticed the short fall in the 1.7X GPC's magnification too.  I measure ~1.55 to 1.6X -ish, depending on where it is in the light path, the viewer used and the focal ratio of the objective.  Coupled with its modest back focus extension, it's my favorite GPC to use with my CFF 160 F6.5 triplet.  

 

Actually, I've not bothered to measure the 1.25X GPC though.  I wonder how accurate that number is too.

 

Jeff


Edited by Jeff B, 24 January 2020 - 07:07 PM.


#4 Jeff B

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Posted 31 January 2020 - 03:41 PM

Some more handy, direct measurements, again, taken in my DPAC set up but this time of viewer light path lengths. 

 

All viewers use a Baader style T2 Quick changer adapter (custome for the Denk II) and measurements were made with the Ronchi grating sitting on the top of a viewer eyepiece collet while focusing to a null in DPAC.  The viewers were attached to the same diagonal with the same T2 dovetail.

 

My usual suspects (with the results) are from left to right in the line up photo:

 

1. Zeiss "Sharpest" (now with "APO" designation too), with Baader Click-lock eyepiece collets from Denis Levatic:  137mm

 

2. Zeiss Sharpest like above but with "blue" eyepiece collets, again from Denis:  127mm

 

3. Good old Denk II:  118mm (114mm w/o the T2 dovetail adapter)

 

4. Zeiss 30mm with blue collets from Denis: 118mm

 

5. Good old Baader MK V, super charged by Denis for 30mm clear aperture:  112mm

 

These measurements should be of help.  I really need them for my refractor ATM projects.

 

Enjoy.

 

Jeff

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Edited by Jeff B, 31 January 2020 - 05:41 PM.

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#5 bcarter1234

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Posted 31 January 2020 - 05:36 PM

Hey, I have that exact same dryer!

 

A buddy and I had just picked up his brand new sprint car from the fresh from the paint shop. We drive to another guys house to drop off some tools. When we pull up the guy and comes out and says "Wow! Nice trailer!" He did not have a racing bone in his body. ;-)

 

Thanks for posting this information, helpful even for a reflector user. Hmm, Zeiss 30mm.....

 

Take care,

Brent



#6 Eddgie

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Posted 31 January 2020 - 07:31 PM

It is incredible that they can keep the Mark V light path 112mm.  That is shorter than the new Maxbright II.

 

The Denk is longer than other reports (116mm) but I would imagine that this is due the light path length of the T2 adapter. 

 

137mm is pretty tall but many of the new refractors are binoviewer ready, but this might be a bit too much even for some of them. With a T2 diagonal, that is 175mm of light path. 

 

 

For future reference, the Binotron is 127mm with the focusers all the way down. 

 

Good data.  Thanks for providing. 



#7 denis0007dl

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Posted 01 February 2020 - 01:49 PM

Some more handy, direct measurements, again, taken in my DPAC set up but this time of viewer light path lengths. 

 

All viewers use a Baader style T2 Quick changer adapter (custome for the Denk II) and measurements were made with the Ronchi grating sitting on the top of a viewer eyepiece collet while focusing to a null in DPAC.  The viewers were attached to the same diagonal with the same T2 dovetail.

 

My usual suspects (with the results) are from left to right in the line up photo:

 

1. Zeiss "Sharpest" (now with "APO" designation too), with Baader Click-lock eyepiece collets from Denis Levatic:  137mm

 

2. Zeiss Sharpest like above but with "blue" eyepiece collets, again from Denis:  127mm

 

3. Good old Denk II:  118mm (114mm w/o the T2 dovetail adapter)

 

4. Zeiss 30mm with blue collets from Denis: 118mm

 

5. Good old Baader MK V, super charged by Denis for 30mm clear aperture:  112mm

 

These measurements should be of help.  I really need them for my refractor ATM projects.

 

Enjoy.

 

Jeff

Very nice collection Jeff,

 

didnt know you have so many binoviewers from me bugeyes.gif



#8 AtmosFearIC

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Posted 01 February 2020 - 09:59 PM

This is really helpful as I’ve been thinking of changing from the Baader MkV. Never realised that it was one of the shortest on the market. Maybe binoviewing with the Mewlon 250CRS is not going to be practical with the corrector installed.


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