18 replies to this topic

[rwoodin3]

I'm posting this in hopes of positive advise and help to find a solution to adapt 60mm/2.36" male threaded OD, 54mm non-threaded ID rear cell on what I think is a 1990's Celestron C14 SCT, to the common 2"/M48 thread on all or most SCT accessories.

I bought this used "black tube" C14 the beginning of August. I have it mounted to a used AP1200GTO I also purchased around the same time. The equipment is all attached to a concrete pier in my back yard roll off roof shed.

So, the info on this scope is it's a 14" Celestron SCT with "Celestron" printed in orange on both sides of the black tube. On the top of the tube, there is one sticker that says "StarBright coatings" with no mention of XLT. There is another sticker the says "Fastar Compatible". The optics appear to be in very good condition. 

The issue is on the back of tube there is ribbed sandcast metal with the rear cell tube protruding very slightly. I do not know tpi, but the OD measures 60mm at the top of the threads. The ID of rear cell is something like 54.7mm, but my caliper is a cheap digital one, so it's probably just 54mm id. There is nothing else on the back around the 60mm rear cell.

The scope came with a Lumicon Giant Easy Guider (with missing OAG tube, but an intact 80mm "corrector" mounted in metal frame and, and adapter ring with female threaded 60mm ID an OD of 91mm. The outer surface of the ring is grooved and is fixed to the giant easy guider by 3 brass tension screws that secure the guider to the adapter ring. I can mount my ASI294MC Pro camera to the easy guider, but I'd like more flexibility to connect a ZWO EAF controlled 2" GSO linear bearing focuser, a coma corrector/reducer, ASI camera, filters etc.
I contacted Agena-Astro and all they could say is it looked as is maybe a piece was missing and to contact Celestron.

I had already contacted Celestron and am awaiting feedback from them.

I contacted High Point Scientific and am awaiting feedback from them.

 

Here is all relevant dimensions

 

rear cell of C14 = 60mm OD threaded, 54mm ID unthreaded

 

Giant Easy Guider = 91mm ID unthreaded, 100mm OD unthreaded

 

Giant Easy Guider to rear cell adapter ring = 60mm ID threaded, 91mm OD grooved

 

GSO 2" linear bearing focuser = Main assembly 73mm ID unthreaded, SCT adapter ring 73mm OD unthreaded, SCT adapter ring ID 50mm threaded ** The SCT adapter ring screws onto a 50mm rear cell and tension screws clamp the main assembly onto outer part of the SCT adapter ring. Item is shown here - https://agenaastro.c...dual-speed.html

 

I'll attach pictures that show what I'm trying to explain here.
Hopefully this post is in the right category.

 

Thanks in advance for any info you can provide.

 

Ralph

 

 

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[The Planetman]

You're needing what some call a visual back. Screws on the back of the scope and adapts down to 2".
Send me a PM. I think I might be able to help you out.

[davidmcgo]

Looks like the baffle nut came off inside of the giant easy guider.  There should be a threaded ring with 3.28” OD threads and inside that match the protruding tube threads.

 

Dave

[rwoodin3]

Looks like the baffle nut came off inside of the giant easy guider.  There should be a threaded ring with 3.28” OD threads and inside that match the protruding tube threads.

 

Dave

Yes, the adapter ring in the easy guider comes out ... easily! But the 91mm outer surface is not threaded. It has a groove on it. The Giant easy guider has brass screws that tighten down into that groove to securely clamp the ring inside the front of the easy guider, so the whole assembly can be screwed on to the threaded 60mm baffle tube.

[rwoodin3]

Looks like the baffle nut came off inside of the giant easy guider.  There should be a threaded ring with 3.28” OD threads and inside that match the protruding tube threads.

 

Dave

Thanks kindly, Dave. I sent you a pm just now.

[davidmcgo]

I have not received a PM.

 

If you have the tapered adapter for the Easy Guider, take a good look inside it and see if the baffle nut is stuck inside it.  

 

Dave

 

Thanks kindly, Dave. I sent you a pm just now.

Edited by davidmcgo, 29 August 2024 - 09:34 AM.

[rwoodin3]

I have not received a PM.

 

If you have the tapered adapter for the Easy Guider, take a good look inside it and see if the baffle nut is stuck inside it.  

 

Dave

Sorry Dave. I confused you with The Planet Man, who I'm PMing with. I just took another look inside GEG. There is no baffle nut.

What is hanging everything up is the adapter ring that IS inside the GEG has internal hole with threads that fit the 60mm baffle tube, however, the 3.5" external perimeter of this adapter ring is not threaded, it has a groove, that allows it to be secured to the scope end of the GEG with brass tension screws that go through holes at scope side of GEG, into the groove of the 3.5" adapter ring. The 3.5" adapters I see for sale are all large format SCT thread. I will probably end up drilling and tapping holes in one of those adapters and use grub screws to secure to the 3.5" GEG adapter. I'm experiencing the used scope curve ball effect here!
 

 

[davidmcgo]

I think what you are saying is the 60/91 adapter ring is actually the GEG adapter ring and the baffle lock nut stuck inside.  There is a lip there and a different hue to the anodizing.  I had a GEG years back and the adapter ring with the groove was pretty thin walled.  ID of it was to fit the 3.28” (83mm) threaded baffle nut.  
 

Dave

Edited by davidmcgo, 30 August 2024 - 01:49 PM.

[davidmcgo]

See photos 6 and 8 in the ad here for what the GEG adapter looks like without the baffle nut stuck in it:

 

https://www.astrosel....php?Id=186409 

 

Dave

[rwoodin3]

I see what you mean in those photos. There is definitely no adapter with threaded 3.28" ID. If there was, there is nothing on the back of the scope to connect it to. The ID of the adapter in this GEG is 60mm.

I'll get something to fit on it that I can adapt to 2" SCT thread adapter and put my GSO focuser on it. After using the GSO focuser on my 10" Meade SCT, there's no going back to main mirror wobble and image shift.

I actually bought 3" lock screws so I can lock the mirror in focus and just fine focus with the GSO linear bearing focuser using the ASI EAF.

[davidmcgo]

The piece with the 60mm ID is a separate part, think of a disk with a 60mm hole with inner threads and the outer edge has 83mm threads.  This is what Celestron calls the baffle nut.  That part got jammed in the GEG adaptor.  You have the part, you just need to separate it out of the GEG adapter and then get some thread locker and put it back on the scope.  The GEG adapter is 83mm inner diameter by itself.

 

Dave

Edited by davidmcgo, 30 August 2024 - 01:48 PM.

[ccwemyss]

What you are calling the "60mm adapter ring" is two parts -- an inner ring, and an outer ring. The inner ring is the baffle lock nut. It has a 60mm threaded inside diameter, and a 3.28" outside threaded diameter. The outer ring is screwed onto the baffle nut, to provide a dovetail groove so that the guider can be rotated. The prior owner over-tightened the outer ring, so that the baffle nut came off with it and is stuck inside.

 

You need that baffle nut on the telescope. It holds the baffle tube in place, and the baffle tube is what the mirror rides on as it is focused. If the baffle isn't secured by the nut, the focuser pushing on the one side of the mirror mount can move the tube to a different angle, which will cause significant image shifts and loss of collimation. 

 

Chip W. 

[rwoodin3]

Guys, Dave, Chip, Ross...

 

Can't thank you all enough. Especially for Dave's persistence.

It was staring me right in the face all along.

Ross has sent me a 3.28" to 2" adapter.

Once I get out to the shed and get the GEG ring off the baffle nut, I'll be good to go.

 

[rwoodin3]

Adapters separated. All is well. Connections with scope at left, focuser at right.

 

[rwoodin3]

The piece with the 60mm ID is a separate part, think of a disk with a 60mm hole with inner threads and the outer edge has 83mm threads.  This is what Celestron calls the baffle nut.  That part got jammed in the GEG adaptor.  You have the part, you just need to separate it out of the GEG adapter and then get some thread locker and put it back on the scope.  The GEG adapter is 83mm inner diameter by itself.

 

Dave

Just curious, high strength or medium strength thread locker? I see loctite 242 blue/medium and loctite 271 red/high temp automotive...

[ccwemyss]

I would use the blue. The goal is to keep it from coming off again with an accessory, not to prevent the ability to disassemble the scope if that's ever needed. 

 

In fact, I'd try using it without any, to start with, until you are sure that the draw tube is truly centered and aligned (the C14 is quite sensitive to alignment -- see: https://www.wilmslow..._alignment.html). I'd only add it if it turns out that you're regularly changing the accessories, and it's not staying on the baffle when you do that. 

 

Chip W. 

[davidmcgo]

Agree with Chip.  I would use blue.  Just use a fresh tube, the stuff can go bad.  
 

Dave

[rwoodin3]

Thanks guys!

[davidmcgo]

Glad you got it sorted out.

 

Dave