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Standard 2" Dielectric or premium 1.25" Diagonal?

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#1 CosmoNewt

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Posted 14 August 2019 - 03:38 PM

I need help deciding on what diagonal to purchase for my AT102ED.  I was initially inclined to purchase the AT 2" but it is currently unavailable and I need to get this scope fully operational.  My premium eyepieces are 1.25", the widest being a ES 24/68* which should theoretically give me around 2.25*, more that enough to view many of the nebulas I plan on looking at.  My 2" eyepieces are mostly my finders for my 8" Zhumell Z8 (30 mm GSO superview and 38 mm Agena SWA).  After the purchase of this refractor I am not planning on spending much more for a long time until I get a lot of observation time and can appreciate this setup fully.

 

I have decided that my options are either a premium 1.25" such as  TeleVue Everbrite or the 2" Orion Dielectric Diagonal.  The difference of $60 is not a big deal to me.

 

I like the idea of the TeleVue being the last 1.25" diagonal I will ever need to buy and own.  It has a solid construction that will accept the heavier 1.25" eyepieces, holds its value, and has excellent optics.    

 

The Orion 2" will accept my 2" SWA but that really is the only immediate benefit I will reap.   I chose the Orion based on looking very similar to the AstroTech. 

 

I considered GSO and its clones but the 1.25" adapter is machined in a way with a dish that will not allow my larger 1.25" eyepieces to sit flush and I have concerns about how secure it will hold them. 

 

Currently I am steering towards the TeleVue based on my current setup.  I would like to get some other opinions. 

 

Thank you and clear skies. 


Edited by CosmoNewt, 14 August 2019 - 04:07 PM.


#2 sg6

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Posted 14 August 2019 - 04:16 PM

If the scope has sufficent focal length then the 2" dielectric. They are fairly hight reflectivity and I cannit think a "Premium" one would be flatter.

 

Also the 2" allow you to use 2" eyepieces.

 

What is the travel on the focuser?

I can just get a 1.25" eyepiece to reach focus and the travel on my 72ED is 40mm (think 38 to be totally accurate).


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#3 rustynpp

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Posted 14 August 2019 - 04:23 PM

No question - get the 2". It's very likely that at some point you'll want to try a 2" EP, and once you do you'll stop using the 1.25".

 

Someone will correct me if I'm wrong, but it's my understanding that - all else being equal - a 1.25" EP will likely perform better in a 2" diagonal than a 1.25". This owing to the fact that most defects in the diagonal mirror will be near the edges, which aren't visible to the EP in the 2" diagonal but are in the 1.25".

 

Watch the classifieds and Astromart for used premium 2" diagonals. If you give it a few weeks you may be able to snag a deal.


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#4 Migwan

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Posted 14 August 2019 - 04:30 PM

Have the 24ES68 and like it, but 2.25° is not enough in my opinion.   Might as well grab some scissors and cut the ends of Andromeda.   jd


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#5 photoracer18

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Posted 14 August 2019 - 04:31 PM

I have a lot of different diagonals. In fact closer to one per scope as some came with them used. I have AT dielectrics in both 1.25" and 2", a GSO dielectric in 2", and 2 Stellarvue dielectrics in 2", a regular one and a 1/10th Lambda one. I use the AT 1.25" for travel as my set of travel eyepieces are all 1.25" (Vixen LV). The SV 1/10th Lambda stays in the case with my SVA130T. The others I use interchangeably in the rest of my scopes. I find that the GSO with the countersunk 1.25" adapter works really well on my Pentax XLs with the big barrels fine.


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#6 CosmoNewt

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Posted 14 August 2019 - 05:09 PM

Thanks for your help. I will get the 2" and will not look back.

 

 

With the extra money saved I can consider either a 45 correct image for terrestrial viewing across the bay or maybe a solar filter in time for Mercury's transit......more versatility.  


Edited by CosmoNewt, 14 August 2019 - 05:23 PM.

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#7 CosmoNewt

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Posted 14 August 2019 - 05:16 PM

 

What is the travel on the focuser?

I can just get a 1.25" eyepiece to reach focus and the travel on my 72ED is 40mm (think 38 to be totally accurate).

The travel of the focuser on the AT102ED is 92mm.   



#8 nicoledoula

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Posted 14 August 2019 - 05:17 PM

Premium 2" diagonal


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#9 M11Mike

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Posted 14 August 2019 - 05:17 PM

Good choice - more versatility!!!

 

M11Mike


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#10 CosmoNewt

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Posted 14 August 2019 - 05:23 PM

Premium 2" diagonal

I wish.  $320 is just a little out of my reach.  



#11 M11Mike

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Posted 14 August 2019 - 07:01 PM

Cosmo - I use a GSO 2" Dielectric (Agena  Astro) --- excellent 2" diagonal - $100 shipped - brand new.

High quality and works wonderfully - this replaced an older TV "Everbrite" 2" I had that cost twice as much.

M11Mike


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#12 CosmoNewt

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Posted 14 August 2019 - 07:20 PM

Cosmo - I use a GSO 2" Dielectric (Agena  Astro) --- excellent 2" diagonal - $100 shipped - brand new.

High quality and works wonderfully - this replaced an older TV "Everbrite" 2" I had that cost twice as much.

M11Mike

In fact this is what I ended up getting. I was initially concerned with the countersink, but photoracer put my mind at ease.  I called Agena and they said the width of the countersink is 51mm.  The ES 24/68 will stick out some but it will work perfectly fine.  I have a tendency to overthink things.  In a few days I will have my diagonal along with a Rigel QF and ready to rock.  

Thanks for your help and Clear Skies.  


Edited by CosmoNewt, 14 August 2019 - 07:22 PM.

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#13 Spikey131

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Posted 15 August 2019 - 07:51 PM

In fact this is what I ended up getting. I was initially concerned with the countersink, but photoracer put my mind at ease.  I called Agena and they said the width of the countersink is 51mm.  The ES 24/68 will stick out some but it will work perfectly fine.  I have a tendency to overthink things.  In a few days I will have my diagonal along with a Rigel QF and ready to rock.  

Thanks for your help and Clear Skies.  

Good move.  Now get a Meade 56mm plossl and you don’t need a finder.



#14 Jon Isaacs

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Posted 16 August 2019 - 08:13 AM

Good move.  Now get a Meade 56mm plossl and you don’t need a finder.

 

Cosmonewt already has a 38mm Agena SWA, this will provide the maximum possible field of view possible with a 2 inch eyepiece.  

 

Jon



#15 LDW47

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Posted 18 August 2019 - 07:03 PM

Good move.  Now get a Meade 56mm plossl and you don’t need a finder.

I have been looking for a 50-60mm ep, where do you get the 56mm Meade or it an older model ?



#16 Traveler

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Posted 18 August 2019 - 10:38 PM

here:  https://www.astrosho...56mm-2-/p,47520

 

There is also an Omegon incarnation for 10 euro less...




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