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Diagonal for Nexstar 8SE that won't hit base mount

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#1 Mack Truck

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Posted 30 December 2012 - 08:50 AM

Any advice for a diagonal for a Celstron Nexstar 8 SE ? My main concern is that the stock unit hits the base of the mount when you aim at zenith.

#2 Geo.

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Posted 30 December 2012 - 02:02 PM

An SCT specific diagonal may work, but have you tried sliding the tube forward a bit on its dovetail?

#3 Eddgie

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Posted 30 December 2012 - 03:15 PM

If your scope does not have a seperate dovetail, then your best chance of reaching focus with a 2" diagonal will be the Televue 2" short diagonal and the matching Televue 2" short adapter.

Astronomics catalog listing for SCT Short Adapter

Astronomics catalog listing for Televue Short Diagonal

You can ask on the SCT forum if someone can confirm that this will work if your scope does not have a dovetail mount.

There is one other option that results in an even shorter unit. The Baader diagonals all accept the Baader T2 accessories. One of the accessories that Baader sells is a SCT to T/2 converter. This is only 15mm long (about 1/3" shorter than even the Televue short diagonal and short adapter). This would give you the best chance of clearance, and additionally, would give you the shortest possible light path, resulting in the widest possible true field your scope can provide using 2" eyepeices and working at full aperture.

And the Baader has this too. For less than the Televue diagonal, you can buy the Baader 2" Mirror diagonal with a 2" Clicklock eyepiece holder! Now you're talking!

Look at figure #3 on this page for a picture of how short this setup is. You can't get any shorter than this and still be able to rotate the diagonal (there is a 10mm adapter, but it does not allow diagonal rotation)....

Picture of Baader unit with short adapter on SCT... See figure 3

And finally there is the cheap solution... As I recall, Celestron used to sell a short SCT diagonal that was intended to work for scopes that had limited fork clearance.
I believe Meade may have offered one too.

#4 Midnight Dan

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Posted 30 December 2012 - 09:28 PM

Hi Mack:

Your 8SE should have a dovetail rail on the side of the scope, which is held onto the mount with a clamp and a big thumbscrew. You can loosen the clamp and slide the tube forward to allow more clearance.

The stock unit will definitely clear the base on an 8SE if the dovetail is properly adjusted.

-Dan

#5 Mack Truck

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Posted 31 December 2012 - 03:02 AM

Thanks for the input. I think the Baader is what I need, but do you know exactly what accessory I need directly to the back of the Nexstar 8 SE ? I checked Baader's web site, but my german is pretty limited!

#6 bcuddihee

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Posted 31 December 2012 - 09:32 AM

Actually, william optics makes a 2" diagonal and sct low profile adapter. The way it works is that you unscrew the nosepiece from the diagonal and screw on the adapter. Then unscrew the stock visual back from the scope and screw on the diagonal. This combo will clear the base on the 8se.

#7 Mack Truck

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Posted 31 December 2012 - 09:40 AM

Actually, william optics makes a 2" diagonal and sct low profile adapter. The way it works is that you unscrew the nosepiece from the diagonal and screw on the adapter. Then unscrew the stock visual back from the scope and screw on the diagonal. This combo will clear the base on the 8se.

Once it is screwed to the Nexstar can you still turn it sideways or is it locked ?

#8 mclewis1

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Posted 31 December 2012 - 10:23 AM

It's locked, the friction between the edge of the diagonal ring and the area around the opening at the rear of the scope keeps things in place. You just loosen the ring slightly, turn to new position, and tighten ring ... no problem. You don't want the diagonal to have the ability to move until you want it to move. With heavier components (big 2" eyepieces, binoviewers, cameras, etc.) you want things to be as solid as possible.

#9 Mack Truck

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Posted 31 December 2012 - 10:28 AM

Both William Optics and Baader diagonals seem to be very good products. Any feedback with William Optics ? Being in Europe I am a bit concerned about shipping from Taiwan (they do not offer a lot of shipping option). On the other hand, I had a bad experience with a Baader zoom eye piece (lots of dirt in the zoom) so I am also hesitant to go German...

#10 Bob Griffiths

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Posted 31 December 2012 - 10:51 AM

I am quite surprised that someone did not direct you to the Nexstar Specific forum located directly above this form..

That is where the Boys that run an 8se hang out...
and the topic you are interested in has been discussed many many times..

There is also dicussions about modifying the dovetail to allow even more adjustment room..by using either Rons rail or Eddies Bracket... both cheap and very effective solutions ..

I run a Denkemier 2 inch P/S diagonal on both my 8i (earlier model of the 8Se) as well as on my CPC1100 my 8i uses Rays Bracket BUT I can clear the base with room spare to with the 8i on the very few nights I find a need to actually observe at Zenith..

BTW... I read and replied to you one post about eyepieces on the other Asrto forum.. I think you will find more help here then over there with your specific scope..

Bob G.

#11 bcuddihee

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Posted 31 December 2012 - 11:12 AM

On the Nexstar you will not need to rotate the diagonal, it should be kept in the 12 o'clock position.






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