40 replies to this topic

[MAT_Blue]

Buy a 2” GSO single speed focuser from Agena for about $150, take out the three screws, remove the existing focuser, install the 2” and secure with the three screws ! It fits perfectly, took me about 20 minutes ! If you need some info Agena is great to supply their knowledge ! Just make sure you have the ID of the tube to match the proper size focuser !

Looking at the pix of your scope, it doesn't look like you had to add an extender to get focus with the 2" focuser.  The Agena web site says one may be needed.  Not??

[LDW47]

Looking at the pix of your scope, it doesn't look like you had to add an extender to get focus with the 2" focuser.  The Agena web site says one may be needed.  Not??

Agena says that just to cover their rear in those times with some scopes where you do need one, all companys cover their a*s ! They don’t know what scope each person who orders a rplacement focuser has unless you contact / talk to them, which you can do, then you will get the low down on a particular scope ! I will say I sure didn’t need one with my C80 !

Edited by LDW47, 13 February 2019 - 06:24 PM.

[MAT_Blue]

Agena says that just to cover their rear in those times with some scopes where you do need one, all companys cover their a*s ! They don’t know what scope each person who orders a rplacement focuser has unless you contact / talk to them, which you can do, then you will get the low down on a particular scope ! I will say I sure didn’t need one with my C80 !

Thanks.  The stock focuser will extend out to 230mm from the end of the tube.  The GSO one will only go about 175mm (per the specs on the Agena web site).  I don't think I ever got the focuser extended that far out.

If you get a chance, could you take a couple of close-in pix of the focuser installation on your scope and post them?  Thanks in advance.

[LDW47]

Thanks.  The stock focuser will extend out to 230mm from the end of the tube.  The GSO one will only go about 175mm (per the specs on the Agena web site).  I don't think I ever got the focuser extended that far out.

If you get a chance, could you take a couple of close-in pix of the focuser installation on your scope and post them?  Thanks in advance.

Here are the pics you requested, I really don’t know what you are looking for / to see ? I hope these will do !

Attached Thumbnails

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[MAT_Blue]

DCFF31BE-81E3-4E71-BDA1-39421B875625.jpeg

Here are the pics you requested, I really don’t know what you are looking for / to see ? I hope these will do !

 

Thanks a lot.  Those are perfect   I just wanted to see what it looked like installed.   Looks very simple.  I feel really confident it will work great.  I ordered mine today.  Can't wait now.

[LDW47]

Thanks a lot.  Those are perfect   I just wanted to see what it looked like installed.   Looks very simple.  I feel really confident it will work great.  I ordered mine today.  Can't wait now.

It will, they are a great focuser for the price as you can see !

[MAT_Blue]

This is an excellent scope for its optics, and you will like the sharp views of doubles, etc. 

 

You have several choice for setting up a dovetail.

 

The first is similar to the note above by Starman876, except you will see that one of the rings does not clamp down to the OTA tube.. it was desinged to be held in place by the Vixen Celestron Alt-az mount itself, which slotted into those small rectangular areas on the rings that you measured.  You would drill into those slots to attach the dovetail, but would stilll have the problem that one ring has no clamping option. You also face the problem that that only way to get the rings off of the OTA, is to remove the dewshield or focuser and slide them off. 

 

A logistically easier solution (but more $$) is to buy a  set of hinged rings and attach the dovetail to them.

 

Great scope and worth the effort to find the best mounting options for you.

 

Mike

I ended up getting the hinged rings from Agena.  Work great.  Thanks for the tip.

[Brent Campbell]

The original alt atz mounts do suck.  I purchased a vixen Polaris mount head and transfered the alt atz mounts legs to it.  The original rings with Scope seem to fit well.   Sadly I’m going to be selling this Scope soon because it’s redundant to my Astro tech 102 Ed which has a similar focal length.

[MAT_Blue]

The original alt atz mounts do suck.  I purchased a vixen Polaris mount head and transfered the alt atz mounts legs to it.  The original rings with Scope seem to fit well.   Sadly I’m going to be selling this Scope soon because it’s redundant to my Astro tech 102 Ed which has a similar focal length.

Hope the old Firstscope finds a good home.

[photoracer18]

BTW, do you remember what dovetail bar and rings you used?  I bought an 11 inch dovetail bar from Agena and was going to see if I could do something with the existing rings.  I have a set of rings on my wishlist at Agena in case I need them.  They are:
https://agenaastro.c...e-ring-3-5.html
I measured the OD of the scope at 3 9/16", which is close enough, I suppose, for these rings advertised as 3.47 to 3.54 inches.
 
The main reason I wanted to keep the CB-80 was to use it as a short-focus scope for use with an ASI224MC camera.  I figure with a 0.5 focal reducer, I should be able to capture all of M31 and similar sized objects with it.  Something I don't think I could do with my 1500mm focal length NexStar 6SE.  I'm figuring the focal reducer will turn it from 910mm to 455mm focal length.

The chance is good that the 80mm will not be able to reach focus with a .5x focal reducer. Most of those type of reducers were made for SCTs which have a much larger range of focus than a refractor. Most if not all refractor reducers fall in the .7x range for the reasons I mentioned. Plus while you can use SCT reducers on refractors that have similar F-ratios you can't go as short as an SCT.

[LDW47]

Did you ever get / install a 2” GSO focuser for your scope ?

[MAT_Blue]

Did you ever get / install a 2” GSO focuser for your scope ?

No.  Not yet.  The weather here (St. Louis, MO) has been awful and I've got lots of other stuff to do.  Thanks for staying in touch, though.  If I get around to it anytime soon, I'll be sure to post something here to let people know how it went.

I did get the scope rings and mounted the Vixen bar and had one night with it using the goto alt-az mount that came with my NexStar 6SE.  Worked reasonably well.  It wasn't a "wow what a great scope" experience.  But the seeing was not good and it's pretty light-polluted where I live.  I haven't had a chance to use it in decent weather, good seeing and dark skies yet.

[pdxmoon]

Mount away! I have dove bars on all my classics (Tasco, Unitron) and mount on modern mounts like Porta II all the time. Great way to re-use these old beauties! Good luck!

[MAT_Blue]

Story about this scope.  My wife and I are spending the winter down south where it's warm.  I brought all my telescopes and astrocams with me except for the CB-80, which we didn't have room for in the van.  We drove back to St. Louis for Christmas but I didn't even think to bring at least one of the astrocams with me for the Jup/Sat conjunction.  Fortunately, the entire CB-80, old mount and all, was still there so I ended up using it to watch the conjunction.  The night was very clear and I got great views of the conjunction through the CB-80 with a 26mm eyepiece.  The best pix I got was eyepiece projection using a Canon G9X point and shoot (image attached).  It worked out so great that I decided my Christmas present to myself would be the 2" focuser, diagonal and 2.5x barlow.  The only 2" eyepiece I have is a 28mm.  Planning to get 10-12mm eyepiece.  We brought it back south with us and it's a great scope now.  Thanks for your support and encouragement.

Here's the best image I got of the conjunction with the CB-80, eyepiece projection and no tracking or guiding.

[billmalona]

What is the difference between C80 and CB80 scopes?

[MAT_Blue]

What is the difference between C80 and CB80 scopes?

I have what I purchased as a “Firstscope 80”, which I think is what’s called the CB80.   It came on with an alt-az mount and a wooden tripod.  It has a focal length of 910mm, making it f/11.3   There was also a C80, which some people think was the same OTA on a Polaris EQ mount.  These were both available in the mid-80’s. I’ve seen talk of a C80 with a focal length of 1000mm but I can’t document it.  That one may be a later model.  There’s another thread here that has pictures from a Celestron catalogue that shows the Firstscope 80 on the alt-az/wooden tripod version that I have and which I think is the CB-80.  There’s also a picture of the same OTA on an EQ mount that they call the C80. 

https://www.cloudyni...-80s-from-1985/

 

Here’s a thread that pretty much confirms that mine is the CB-80.  Mine looks exactly like this with the same specs. 

https://www.cloudyni...ere-these-made/

 

My CB80/Firstscope 80 is a nice scope with quality lenses (for 1985) but it’s not an APO.   I tried it for astrophotographry with an ASI294MC-Pro and it had pretty bad blue haloes around the stars but, except for that, produced good images.  It’s a great visual scope. 
 

Mark T.