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Which would be better diagonal for my new Meade 80mm

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8 replies to this topic

#1 George Methvin

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Posted 12 February 2020 - 03:53 PM

I just received my new Meade 80mm adventure scope but want to get a better 1.25 diagonal which would be better a prism or a mirror diagonal. Thanks for the help.



#2 2696

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Posted 12 February 2020 - 04:20 PM

Depends on how much you want to spend, the Astro-tech 1.25" dielectric diagonals are great and pretty cheap at I believe $70. But if you want to go a little cheaper there are some GSO diagonals that I'm sure are much better than the one that came with the scope.
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#3 cookjaiii

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Posted 12 February 2020 - 04:24 PM

The short focal length (f/5) makes for a very steep light cone, and conventional wisdom says to stay away from prism diagonals because they will give you false color at short focal ratios.


Edited by cookjaiii, 12 February 2020 - 05:21 PM.

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#4 George Methvin

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Posted 12 February 2020 - 04:28 PM

Ok so you think I should go with a mirror diagonal, yea I may look at the GSO they should be better then what came with the scope. Thanks for the help I plan to use this little scope for wide field views of the night skies, Thanks again.



#5 George Methvin

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Posted 12 February 2020 - 04:30 PM

Wow did not know that about prism diag at f/5 giving more false color thanks for that info.



#6 vtornado

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Posted 12 February 2020 - 04:52 PM

This is a good diagonal.  I like dielectrics because the mirror is harder than a first surface

glass mirror and less easy to scratch while cleaning, and these do get dirty.

 

https://www.astronom...r-diagonal.html

 

This  diagonal below is  $30.00, and other members here have it and are happy.  You could

scratch this up, buy a new one and still pay less than the dielectric.

 

And don't worry too much about cleaning, I'm fairly carless with mine, but stuff does get

dumped into the diagonal from the eyepiece.  Maybe I clean mine every two years.

These also dew up when brought from outside to inside.

 

https://optcorp.com/...ec80c8f8db9236e

 

There is also another plain glass mirror by svbony that a friend of mine has for about the same price.


Edited by vtornado, 12 February 2020 - 04:55 PM.


#7 Redbetter

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Posted 12 February 2020 - 05:27 PM

The main thing the AT diagonal has going for it that cheaper diagonals mostly lack is that it has a properly made/aligned solid housing, nosepiece, and eyepiece holder.  

 

Avoid the OPT diagonal and any others like it.  I have had experience with two brand new OPT's and both were horribly misaligned, with mis-threaded bodies so that the nosepiece and eyepiece holder were nowhere near perpendicular to one another.  One was a little better than the other, but its mirror proved to be astigmatic.   


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#8 Paul Hooper

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Posted 12 February 2020 - 07:49 PM

I have the AT 1.25 dielectric.  Works great with my Meade - a real upgrade over the cheap plastic one it comes with.  And when I upgraded to a better scope, I didn’t feel like I needed to upgrade the diagonal right away.



#9 k5apl

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Posted 12 February 2020 - 10:06 PM

+ 1  for the Astro-Tech 1.25 inch dielectric diagonal.




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