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Upgrade Denkmeier Binotron 27 BV

binoculars DIY eyepieces
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#1 lanfeng

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Posted 25 May 2019 - 04:54 AM

Upgrade Denkmeier Binotron 27 BV  

DIY by myself,I used it more than 3 years

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Edited by lanfeng, 25 May 2019 - 08:11 AM.


#2 PowerM3

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Posted 25 May 2019 - 09:06 AM

Wow, very nice work! I would be interested to hear if you noticed any improvements visually with these mods.



#3 Eddgie

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Posted 25 May 2019 - 04:07 PM

Nicely done.

The eyepiece holders appear similar to the Mark V Twistlock.   Can you share the source?



#4 lanfeng

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Posted 25 May 2019 - 08:01 PM

Wow, very nice work! I would be interested to hear if you noticed any improvements visually with these mods.

Eliminates any reflection inside.  contrast enhancement,friendly  to the planet, the moon and the ground.



#5 lanfeng

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Posted 25 May 2019 - 08:13 PM

Nicely done.

The eyepiece holders appear similar to the Mark V Twbutistlock.   Can you share the source?

yes,but no matter MV Twbutistlock or my eyepiece holders There are not concenient and efficient。Actually i like denk eyepiece holders .The bad part is not firm, too long.



#6 Eddgie

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Posted 25 May 2019 - 09:16 PM

Interesting. I have always felt like the Denk self centering dipoters were excellent, but on the B27, with the collimation collar, they add a lot of light path.

 

A very nice build though.



#7 lanfeng

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Posted 25 May 2019 - 09:52 PM

Interesting. I have always felt like the Denk self centering dipoters were excellent, but on the B27, with the collimation collar, they add a lot of light path.

 

A very nice build though.

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#8 Eddgie

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Posted 26 May 2019 - 06:49 AM

Good comparison photo.

 

The light path of the B27 does not really matter that much if it is use with the power switch and OCS, which I am guessing is the most common implementation. It does though raise the power slightly.  I know on my B27, even with the Newtonian extension tube at it's shortest length, while Denk says the low power is 1.3x, I never felt that this was correct (though to be fair, I never drift measured it).  I always felt like I was closer to 1.4x.   In a direct comparison to the Mark V using a 1.7x GPC and using the same 21mm eyepieces, I thought that the difference in true field was much less than it should be.   I thought the Baader 1.7 Newtonian GPC was indeed giving about a 1.7x field, while the field in the Denk was clearly larger, but it sure did not seem that much larger.   

 

Some of that though could be due to the small aperture of the power switch.  This is actually the smallest restriction in the Denk system because here, the aperture of the lens cells in the power switch is only about 25mm or so. 

 

Anyway, to me, because I used the Denk with the OCS, the light path was never a problem for getting to focus, but the total light path of the power switch and the Binoviewer body was a very demanding load on the focuser.   I tore up my Moonlight focuser by using the Denk B27 and heavy eyepieces.   I went through a tension spring (had to go to the refractor tension spring) and two sets of bearings in less than a year.  I eventually upgraded the focuser to the Feathertouch, but shortly after that, I moved to image intensified, so sold the B27.



#9 lanfeng

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Posted 26 May 2019 - 07:32 AM

I test it was 1.266X 2.2X 3.7X(ocs45+40+b27)

I use Feathertouch 2025 on my dob

 

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#10 lanfeng

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Posted 26 May 2019 - 07:45 AM

 power is small range variable.Distance from ocs to the power switch and BV light path



#11 Eddgie

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Posted 26 May 2019 - 09:35 AM

I test it was 1.266X 2.2X 3.7X(ocs45+40+b27)

I use Feathertouch 2025 on my dob

The Feathertouch is far more capable of dealing with this kind of configuration than the Moonlight or other standard Crayford focusers.

You will still tear up bearings, but they are cheap and easy to replace in the Feathertouch.    The problem with standard Crayfords is that as the bearings start to fail, they will drag on the soft (as compared to stainless steel) aluminum focuser tube and scratch and gall the tube which in time requires replacement.  This will not happen with the Feathertouch.

 

Also, in the Feathertouch, the drive shaft does not carry the load and remains light and smooth even in this extreme configuration.   With the standard Crayfords, the tension on the drive shaft has to be increased by an extreme amount to prevent the focuser tube from deflecting the shaft.  This extreme load is what causes the pre-load spring to fail to offer enough traction on the planetary rollers.   Moonlight will be happy to chance the Newtonian focusuer pre-load spring to the pre-load spring used in the Refractor focusers, so someone thinking of ordering a Moonlight for binoviewer use should specify that they want this pre-load spring at time of purchase.   I would not use a standard Crayford for a B27 though. It is just too long a moment and destructive to standard Crayford.  A WO or similar BV with light plossls would probably be fine. The P27 with power switch and heavy eyepieces really needs to be on a Feathertouch. 



#12 lanfeng

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Posted 26 May 2019 - 09:51 AM

YES Feathertouch.Stable and efficient,I use it more than 8 years,It's still as good as new



#13 lanfeng

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Posted 26 May 2019 - 09:54 AM

The Feathertouch is far more capable of dealing with this kind of configuration than the Moonlight or other standard Crayford focusers.

You will still tear up bearings, but they are cheap and easy to replace in the Feathertouch.    The problem with standard Crayfords is that as the bearings start to fail, they will drag on the soft (as compared to stainless steel) aluminum focuser tube and scratch and gall the tube which in time requires replacement.  This will not happen with the Feathertouch.

 

Also, in the Feathertouch, the drive shaft does not carry the load and remains light and smooth even in this extreme configuration.   With the standard Crayfords, the tension on the drive shaft has to be increased by an extreme amount to prevent the focuser tube from deflecting the shaft.  This extreme load is what causes the pre-load spring to fail to offer enough traction on the planetary rollers.   Moonlight will be happy to chance the Newtonian focusuer pre-load spring to the pre-load spring used in the Refractor focusers, so someone thinking of ordering a Moonlight for binoviewer use should specify that they want this pre-load spring at time of purchase.   I would not use a standard Crayford for a B27 though. It is just too long a moment and destructive to standard Crayford.  A WO or similar BV with light plossls would probably be fine. The P27 with power switch and heavy eyepieces really needs to be on a Feathertouch. 

what BV are you using now



#14 Jeff B

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Posted 26 May 2019 - 07:43 PM

The Feathertouch is far more capable of dealing with this kind of configuration than the Moonlight or other standard Crayford focusers.

You will still tear up bearings, but they are cheap and easy to replace in the Feathertouch.    The problem with standard Crayfords is that as the bearings start to fail, they will drag on the soft (as compared to stainless steel) aluminum focuser tube and scratch and gall the tube which in time requires replacement.  This will not happen with the Feathertouch.

 

Also, in the Feathertouch, the drive shaft does not carry the load and remains light and smooth even in this extreme configuration.   With the standard Crayfords, the tension on the drive shaft has to be increased by an extreme amount to prevent the focuser tube from deflecting the shaft.  This extreme load is what causes the pre-load spring to fail to offer enough traction on the planetary rollers.   Moonlight will be happy to chance the Newtonian focusuer pre-load spring to the pre-load spring used in the Refractor focusers, so someone thinking of ordering a Moonlight for binoviewer use should specify that they want this pre-load spring at time of purchase.   I would not use a standard Crayford for a B27 though. It is just too long a moment and destructive to standard Crayford.  A WO or similar BV with light plossls would probably be fine. The P27 with power switch and heavy eyepieces really needs to be on a Feathertouch. 

Very good information to have Eddgie and thank you.

 

Jeff




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