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Strength of Meade 45 deg Erecting Prism

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#1 DeudeMann

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Posted 17 November 2019 - 02:46 PM

Hello all. I have a question regarding the structural strength of the Meade #932 45 deg erecting prism assembly. I searched so sorry if I missed a discussion on this.

I have a Meade ETX 90 on the way that I will set up for terrestrial spotting scope use with some of my existing eyepieces and what nots. I plan to use it with a 1.25" binoviewer and perhaps a DSLR. Though I know I can mount the DSLR directly without the prism, for various reasons I might want the correct orientation for the DSLR so it is possible I might use it with the diagonal. 

I want to use a 45 deg prism, like the #932, since the angle will be nice for spotting scope use and I will get correct imaging (not inverted or mirrored). However I am not very certain about hanging my Canon 80D  or binoviewer off of the end of something made from plastic. From what I understand the Meade #932 does not have an all-metal version, just versions with housings that are mostly or completely plastic. 

I have two concerns here:

- Maintaining axial alignment for decent imaging (flex)

- Not worrying about the eyepiece breaking and dropping my binoviewer and eyepieces, or my camera, in the dirt.

So the question is, need I be concerned?

I know there are nicer, metal housing versions of 45 deg diagonals out there but I like the idea of the integrated telescope adapter with the Meade version, and the price of the Meade is lower though I know you get what you pay for in this hobby.

Thanks

 


Edited by DeudeMann, 17 November 2019 - 02:47 PM.


#2 Jon Isaacs

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Posted 18 November 2019 - 09:07 AM

I have two concerns here:

- Maintaining axial alignment for decent imaging (flex)

- Not worrying about the eyepiece breaking and dropping my binoviewer and eyepieces, or my camera, in the dirt.

So the question is, need I be concerned?

 

 

I think you need to be concerned.  Even with a more robust diagonal, I'd be concerned that if I bumped it in the wrong way, something will break and everything would end up on the ground.

 

Jon



#3 Ernest_SPB

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Posted 18 November 2019 - 11:55 PM

#932 is durable enough to carry binoviewer or other eyepiece-like gadgets.

 

Note, that DSLR (including your Canon 80D) does not require right image orientation, so it is better to mount it without the diagonal. Erecting prism introduces more or less distortion coming from its roof edge and should not be used when not necessary.



#4 DeudeMann

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Posted 20 November 2019 - 11:12 PM

Thanks Ernest. The binoviewer is most likely the heaviest thing I will hang off of it.

I noticed today when I back-mounted my DSLR that the image was correctly oriented. That was a nice surprise. The little Mak actually makes for a decent high-power telephoto lens, although at f/10 it is slow of course and requires higher iso. For the price it's great, no question.  With careful focusing and a big tripod I took a photo of a parked truck that was 1.5 miles away (according to Google earth). From the image it was clear what make and model it was, and some of the detail on the wheels was visible.


Edited by DeudeMann, 20 November 2019 - 11:15 PM.



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