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SCT Baffle Tube Inside Diameters?

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#1 BillP

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Posted 16 November 2014 - 03:14 PM

Since either the inside diameter of the baffle tube or the back port diameter will govern the largest eyepiece field stop that will work with these instruments without vignetting, wanted to compile what these were for the various SCTs.  For the Celestron products found the numbers on their site (http://www.celestron...the OTA itself?).  However, was wondering what the Meade numbers might be?

 

OTA / Baffle opening

 

C14 / 54mm

 

C11 / 54mm

 

C9.25 / 46mm

 

C8 / 37mm

 

C6 / 27mm

 

C5 / 27mm

 

C127 Mak / 27mm

 

C90 Mak / 15mm

---------------------------

Meade 6 / ??

 

Meade 8 / ??

 

Meade 10 / ??

 

Meade 12 / ??

 

Meade 14 / ??


Edited by BillP, 16 November 2014 - 03:15 PM.


#2 evan9162

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Posted 16 November 2014 - 03:58 PM

I have an old 2120 OTA (10", F/10), the baffle tube at the rear port is around 56mm.  



#3 EuropaWill

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Posted 16 November 2014 - 07:32 PM

This brings up the question...

 

If I replaced my 2" Refractor style diagonal in my C11 with a SCT diagonal...would my Meade Series 5000 SWA 40mm EP vignette?  



#4 junomike

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Posted 16 November 2014 - 10:09 PM

This brings up the question...

 

If I replaced my 2" Refractor style diagonal in my C11 with a SCT diagonal...would my Meade Series 5000 SWA 40mm EP vignette?  

Yes!  My 40mm 68-70° EP's vignetted my Generic Dielectric diagonal due to the tapered nosepiece and collar.  I need to use my AP Maxbrite to get un-vignetted views.

 

Mike


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#5 EuropaWill

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Posted 16 November 2014 - 11:03 PM

But my rear sct port is connected to a 2" adapter currently. Shouldn't that sct port be already vignetting the 40mm SWA despite the 2" refractor style diagonal and adapter?



#6 BillP

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Posted 17 November 2014 - 09:05 AM

Is the rear port smaller than 47mm in diameter?  If so then yes it will vignette a 40mm 68 deg EP.  FWIW, when I did a diagonal comparison I discovered several 2" diagonals that would vignette with a 40mm 68 deg EP.  So the diagonal can be the problem also.



#7 GlennLeDrew

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Posted 17 November 2014 - 09:08 AM

Will,

The impact of vignetting depends also on the separation between the obstructor and the focus/field stop. The SCT diagonal has a 38mm restriction immediately ahead of the mirror. This more sharply vignettes the outer field than does the same 38mm rear port aperture because the latter is farther from the focus and so casts a less sharp shadow. 



#8 ewave

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Posted 17 November 2014 - 09:22 AM

BillP, lets throw in the Celestron Edge models as well. Although not quite certain, the C9.25/C11 and C14 "Edge" models all have ~ 47mm after the corrector, but the actual baffles still may hold true to their classic counterparts? The C8 Edge from reports are ~ 37 or 38mm.



#9 GJJim

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Posted 17 November 2014 - 09:46 AM

The rear baffle aperture for the Meade 14" f/10 ACF (circa 2009) is 47 mm. This model also has a edge mask on the secondary that reduces its effective aperture by ~ 0.8". Something tells me that the field illumination profile on this OTA may not be optimized for astrophotography.  :grin:



#10 evan9162

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Posted 17 November 2014 - 10:30 AM

I have an old 2120 OTA (10", F/10), the baffle tube at the rear port is around 56mm.  

 

BTW, this is measured by removing the 3.25" -> 2" SCT thread step-down adapter.



#11 Dom543

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Posted 19 November 2014 - 01:56 PM

Meade 8" f/6.3 (different from f/10)

Baffle tube ID 50.5 mm (2" ep barrel fits inside)
with 10 mm long 42mm ID narrowing at rear port SCT thread.

--Dom

Edited by Dom543, 19 November 2014 - 01:59 PM.


#12 BillP

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Posted 19 November 2014 - 03:29 PM

Dom,

 

How you liking that scope for visual?



#13 MrJones

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Posted 19 November 2014 - 04:17 PM

Meade 6" ACF from an LS system is ID 31mm with calipers.

 

There are at least 2 different baffle tube designs though. My previous 6" ACF from an LT system was threaded the full length of the tube and this one is smooth.

 

I guess that helps explain the large secondary obstruction vs. C6 and this: http://www.cloudynig...ct-maximum-fov/



#14 Dom543

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Posted 22 November 2014 - 08:17 PM

Dom, 
How you liking that scope for visual?


Bill,

I am very happy that I managed to pick up one of these f/6.3 tubes on CN classifieds. But I am using it 90% for electronically assisted observing (EAO) from the place I work part of the year just outside of Boston. My observing perch is on the top of a steel fire escape that has its own dynamics (vibrations). You can see a photo here
http://www.cloudynig...l-setup/page-14 ,Post #338 (the last one).

If you have ever watched broadcasts made with Mallincams or other security video cameras, you know that the experience they offer is not the same as quality visual observing from a dark place. But one can still enjoy astronomy from light polluted or otherwise marginal places (e.g. steel fire escapes) and see details in objects that might not be otherwise discernible with the same apertures.

The Meade native f/6.3 OTA's are my favorites for video or Lodestar assisted observing. This is mostly due to the fast focal ratios (below f/3) that are not easily achievable with f/10 OTAs. I also took my 8" f/6.3 OTA to a trip to Hawaii once. Simply because this was the largest tube that I could take as carry-on in my backpack.

To sum up, the f/6.3 OTA's are special purpose scopes. Their visual quality doesn't match that of my 7" f/15 Mak or 14" Edge HD under ideal conditions. But in special circumstances, when other factors (video camera, poor setup, seeing, light pollution) limit the quality of the experience, they can be the right tool for the job.

--Dom

#15 Dom543

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Posted 22 November 2014 - 08:29 PM

Meade 7" f/15 Mak baffle tube OD 38mm (1.5").

Meade 10" f/6.3 SCT baffle tube OD 57mm (2.25").

--Dom

#16 Sheldon

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Posted 01 September 2018 - 06:29 AM

I've decided to disassemble my LX200 14" and modify the ID of the baffle tube on a lathe.  If that does not work, I will buy a 1 7/8" I.D. or 2" I.D. stainless pipe and have it machined and  blackened.  I am thoroughly incensed with the idea that there are no sources for such parts.  Half **** engineering on the part on major telescope manufacturers is inexcusable.

 

Shelddn




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