1721 replies to this topic

[JoshKnight]

Scroll down to #7 in this thread ... the dropbox link to the manual for a C14 worked for me

 

https://www.cloudyni...-documentation/

[napierm]

Hello,

 

I've been lurking and reading on this forum and others.  A retired engineer gave me a Celestron C8 Ultima.  He says he bought it new in 1990.  Also said it cost over $3K for the package.  That would be over $7K today.

 

Serial number 859306.

 

Trying to attach an image or two but I don't see how.

 

It has an attached Astro Master (not the Pro) digital setting circle that works well on both RA and DEC.

 

Has a 50x80 Polaris right angle finder with a lit reticle and a circle for Polaris that I can't quite figure out how to use properly.  There is a strait adapter to swap out the angle but the optical length is different by almost 1/4 inch which is tedious.  Focus is done with threads on the front of the finder.  Says made in Japan but the quality isn't quite there.

 

I don't see how to line up the OTA and finder exactly with the axis of the fork assembly so that the sighting would be accurate.  Point it exactly at Polaris, turn the fork and the reticle doesn't quite line up anymore.  Tweaking declination gets you closer but not enough that the Polaris reticle circle would be useful.  Probably didn't help that the fork mount was all apart so likely I didn't follow some undocumented alignment procedure on assembly.

 

Has a very heavy tripod with a heavy wedge.  Heavy enough that it is easier to carry them separately and then assemble.  Spent time turning a brass spindle to make it easier to turn the wedge on the tripod for polar alignment.  They really sold this stuff by the pound.

 

Viewing seems good to me.  I've defocused on different bright stars and the rings look pretty well centered.  I wouldn't know which way to adjust it so I've left it as is.  Takes nice pictures of the moon with a Nikon D750 on the T adapter.  I've never gotten my little Dobsonian to do that.

 

Even came with a sun filter to put on the front of the OTA.

 

Biggest downfall is that the drive electronics are dead.  Power supply and inverter are dead (even with new Gates batteries) and the electronics engineer I got it from couldn't fix it either.  Didn't help that there are no schematics and Celestron actually scraped the silkscreen off of the parts to make it impossible to maintain.  Dennis said he shipped the drive to Celestron who then said they couldn't fix it and sent it back.  Guess nobody kept the schematics for maintenance.  How will anyone fix the electronics they sell now in 30 years.

 

This is the version just before the PEC upgrade and has a 120V motor.  The worm gear and driven gear are very nice.  Ran the motor on a variac to test it.   At 90V the motor starts reliably.  Once running it will keep going down to 20V.  I ran it for a day on 60 Hz (no choice, power line) and the Astro Master RA display didn't move by more than a minute back and forth.  So this version wants 60Hz nominal for sidereal speed, not 60.164 Hz.  I think so anyway.

 

I've read that the big gear has 359 teeth.  I don't know the gear ratio of the 120V motor to the worm gear.  I think it is 1 turn in 4 minutes.  If any does know the right frequencies for this drive version I would like to know.  Otherwise I'll just have to experiment.  Want 40Hz to 80Hz for E/W buttons.  Somewhere around 60 Hz for sidereal.  Tad slower for sun.  Somewhere around 58 Hz for moon.

 

I measured the drive current which is surprisingly small:  ~28 mA at 95V; ~38 mA at 130V.  Pulling hard on the fork made no difference that motor keeps right on going with no change in current.  Motor doesn't get warm.  So max power about 5W.

 

My current project is re-inventing the wheel for a battery powered inverter.  Power electronics is not really my area but given time I can make something work.  LTSpice simulations say that the transformer drive (which does seem the simplest way) doesn't work well at various frequencies.  Can optimize for 60 Hz but then at 40 to 80 the source current goes way up.  Current/voltage spikes on a laminated doorbell transformer look ugly.  Best results for low power is a 12V to 120V DC inverter (40 mA max) and then a bridge motor driver.  Add simple electronics to provide pulses, current limiting and dead times.  Simulation says that the fixed pulse lengths give a consistent current flow over the 40 to 80 Hz range.

 

I'm doing it as a small board that just takes 12V and a clock to provide the drive.  Minimize development risk and time.  With modern chips it can be very small.  With that going I can use any little micro on a board to generate the frequencies and controls.  End goal is to duplicate the functions and use the original front panel.

 

Yes, I should just toss the fork and buy a GEM but I like this setup as is.

 

Cheers,

 

Mark Napier

[RSX11M+]

Hello,

 

I've been lurking and reading on this forum and others.  A retired engineer gave me a Celestron C8 Ultima.  He says he bought it new in 1990.  Also said it cost over $3K for the package.  That would be over $7K today.

 

Serial number 859306.

 

Trying to attach an image or two but I don't see how...

Images: Upper right drop-down menu (next to "Sign Out") then "My Gallery". Once posted there you can share them elsewhere.

 

We can help you identify the scope if you post some images. Please include one down the throat, the assembled mount from the side of the forks, and the base - including any printing on covers.

 

1990 for SN 859306 does seem about right.

 

Moderators admonish us for discussing too many operational details or basics here, so please seek help in other forums for those.   

 

I believe you have a fairly typical drive base with hysteresis synchronous a/c motors. These were designed to track with incoming line frequency once a minimum voltage is achieved, and to ignore voltage variations. Timing was indeed arranged to match sidereal rate. Drive controllers were available back in the day, to more precisely adjust when required.

 

But it's not a scope suited to long exposure astrophotography **, but today's cameras can yield good results in much shorter exposures than yesteryear's film.

 

It's a good decision not to attempt adjustments or collimations if viewing seems good. (at least not until you become much more familiar)

 

**Re-reading your description of the Electronics issues, I may have the wrong drive in mind. Your images should help. 

 

Sending "Vintage" scopes to Celestron for service has not yielded predictable results as of late, and is inadvisable.

Edited by RSX11M+, 06 May 2024 - 08:16 PM.

[napierm]

[Jesse7Mak]

I just bought a C8 optical tube from a private party.  I have no purchase information for it.  It’s a black tube, has a coating label of StarBright XLT, and it is Fastar compatible.  It has orange anodized aluminum Vixen top and bottom rails.  The focuser mounting plate is anodized orange.  The serial number of the tube is S78254.

 

I’d be curious to know the age of this tube, but it doesn’t really mean much if I don’t.

 

It’ll be going onto a Losmandy GM-8 push-to mount.  It’ll be a companion to my Meade 7” Mak, also on a push-to GM-8 mount.

[RSX11M+]

 

Thank you for the images.

 

As you surmised, you do have a Celestron Ultima C8.

 

Drive electronics - This is an analog era design, with DC to AC inverter as the RA drive. It was intended for use with 9v lead acid batteries. That any of it's electronics might survive in working condition after 34+ years would be remarkable. 

 

Uncle Rod gives a good review of his in "Guide to Used SCTs" [pg28-32] with particular praise to a "Crown" schmidt-corrector among other things. He too foresaw future electronics problems, and mentioned a replacement board offered by "Tangent Instruments".

 

This still online article (updated Feb 2020) gives details and has info on the Tangent upgrade. Here's another with an updated version.

 

Frankly, the Tangent drive board looks much easier to replicate or reverse engineer than the original. Who knows, you might still locate one.

 

However, designing your own would be a worthy project. I have scopes from before and after this era, but none with "King Tracking Rate" - about which I have always been curious. Still, my interest is as a collector and historian, more than an astronomer or astrophotographer. 

 

Remounting the OTA, if that's what you decide, should be more than satisfactory given all the praise I see for this particular model's optics.

 

Best of luck and fun - please update us once you decide on it's future.

Edited by RSX11M+, 11 May 2024 - 10:51 PM.

[RSX11M+]

I just bought a C8 optical tube from a private party.  I have no purchase information for it.  It’s a black tube, has a coating label of StarBright XLT, and it is Fastar compatible.  It has orange anodized aluminum Vixen top and bottom rails.  The focuser mounting plate is anodized orange.  The serial number of the tube is S78254.

 

I’d be curious to know the age of this tube, but it doesn’t really mean much if I don’t.

 

It’ll be going onto a Losmandy GM-8 push-to mount.  It’ll be a companion to my Meade 7” Mak, also on a push-to GM-8 mount.

We do have a couple examples of "S-----" serial numbers in the C8 registry. 

 

Both indicate these were supplied as OTAs originally.

 

Unfortunately, I can make no guesses as to manufacture date except a wide range bounded by the introduction of Fastar (1997) and S88491 associated with May 2019 purchase or manufacture.

 

If you could supply some images, we might help narrow that down a bit. The orange anodized focuser mount should be a clue, perhaps another member will comment.

 

Either way, thanks for registering.

Edited by RSX11M+, 11 May 2024 - 10:23 PM.

[Jesse7Mak]

We do have a couple examples of "S-----" serial numbers in the C8 registry. 

 

Both indicate these were supplied as OTAs originally.

 

Unfortunately, I can make no guesses as to manufacture date except a wide range bounded by the introduction of Fastar (1997) and S88491 associated with May 2019 purchase or manufacture.

 

If you could supply some images, we might help narrow that down a bit. The orange anodized focuser mount should be a clue, perhaps another member will comment.

 

Either way, thanks for registering.

I’ve asked the seller for details, so we can add to the body of knowledge a little bit.

[John Carpenter]

New to CN, new to telescopes.  Have a 1973 C8 that I am playing around with to see what I can see.  Serial # 212783.  Some troubles as this scope spent the last 20 years heat cycling in an non-insulated attic.  Looks nice though. Expect to ask a lot of questions as I get things running.

 

 

[Kasmos]

New to CN, new to telescopes.  Have a 1973 C8 that I am playing around with to see what I can see.  Serial # 212783.  Some troubles as this scope spent the last 20 years heat cycling in an non-insulated attic.  Looks nice though. Expect to ask a lot of questions as I get things running.

 

 

1973 C8.jpg

That's a very nice telescope to start out with!

 

Just so you know. the forum moderators don't like it when you go off topic with a bunch of questions in this thread, so it's best to start it's own Topic/Thread when you have questions about it.

 

In case you don't have one

The owners manual below is for a newer version but it should have enough similar information to get you started

 

https://wiki.telesco...ting_Manual.pdf

[deSitter]

New to CN, new to telescopes.  Have a 1973 C8 that I am playing around with to see what I can see.  Serial # 212783.  Some troubles as this scope spent the last 20 years heat cycling in an non-insulated attic.  Looks nice though. Expect to ask a lot of questions as I get things running.

 

 

1973 C8.jpg

Wow that is pretty!

 

-drl

[Jesse7Mak]

I just bought a C8 optical tube from a private party.  I have no purchase information for it.  It’s a black tube, has a coating label of StarBright XLT, and it is Fastar compatible.  It has orange anodized aluminum Vixen top and bottom rails.  The focuser mounting plate is anodized orange.  The serial number of the tube is S78254.

 

I’d be curious to know the age of this tube, but it doesn’t really mean much if I don’t.

 

It’ll be going onto a Losmandy GM-8 push-to mount.  It’ll be a companion to my Meade 7” Mak, also on a push-to GM-8 mount.

I can’t go back to edit this.

 

The original owner bought this as part of the Celestron Advanced VX package in 2016 from High Point Scientific.

 

[CHASLX200]

I can’t go back to edit this.

 

The original owner bought this as part of the Celestron Advanced VX package in 2016 from High Point Scientific.

 

IMG_2595.jpeg

Much better with a D plate. I never checked to see if they make a Vixen to D plate holder for my GP mount.

[Jesse7Mak]

Much better with a D plate. I never checked to see if they make a Vixen to D plate holder for my GP mount.

A Losmandy dovetail is already on the way!

 

I don’t recognize the rail in that photo of a current Celestron Advanced VX, it’s wider than the one on the optical tube I have.  It could be that had been changed since 2016, I couldn’t find old catalogs or product sheets to compare.  The tube I have surely has a Vixen rail, roughly 45 mm wide dovetail.

Edited by Jesse7Mak, 12 May 2024 - 04:54 PM.

[RSX11M+]

New to CN, new to telescopes.  Have a 1973 C8 that I am playing around with to see what I can see.  Serial # 212783.  Some troubles as this scope spent the last 20 years heat cycling in an non-insulated attic.  Looks nice though. Expect to ask a lot of questions as I get things running.

 

 

1973 C8.jpg

I would classify that as a "near-mint" sand cast orange tube C8 with exceptional paint condition. That era requires a near extinct power chord, so take care if you have it or if not, spend time looking for it.

 

The date you pose would be correct. Thank you for posting.

[Jeff L]

Serial number 359.

 How do I get this mirror out? Remove caulk and it should come out right? 
I’m new to this so I’m learning as I go. Also where might I find parts? I’m missing the finder and might need a secondary mirror replacement. I need a schematic for the collimator on the secondary. Primary too for that matter.

 Any hints would be greatly appreciated.

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Edited by Jeff L, 16 May 2024 - 12:10 PM.

[M_athias]

Maybe this will help:

http://www.laughton....c11-disasm.html

[deSitter]

Serial number 359.

 How do I get this mirror out? Remove caulk and it should come out right? 
I’m new to this so I’m learning as I go. Also where might I find parts? I’m missing the finder and might need a secondary mirror replacement. I need a schematic for the collimator on the secondary. Primary too for that matter.

 Any hints would be greatly appreciated.

A good start!

 

-drl

[pierce]

Serial number 359.

 How do I get this mirror out? Remove caulk and it should come out right? 
I’m new to this so I’m learning as I go. Also where might I find parts? I’m missing the finder and might need a secondary mirror replacement. I need a schematic for the collimator on the secondary. Primary too for that matter.

 Any hints would be greatly appreciated.

 

There are no 'schematics' to telescope optics as they aren't electrical circuits.   I would be VERY hesitant to remove the optics as its easier to damage them, and the primary at least really doesn't look to be in that bad condition.

 

you can use most any finder scope, odds of finding whatever was originally supplied on a EARLY C8 are slim to none and anyways those likely were 6x30 and not very good..   I like 9x50 erect field right angle finders, most made today have 'vixen shoes' and part #RDPS here, https://www.scopestuff.com/ss_rdpb.htm will attach to existing accessory screws on the scope OTA and hold a finder like... https://www.amazon.com/Astromania-Angled-Finder-Upright-Non-Reversed/dp/B01FA18G18

[Kasmos]

There are no 'schematics' to telescope optics as they aren't electrical circuits.   I would be VERY hesitant to remove the optics as its easier to damage them, and the primary at least really doesn't look to be in that bad condition.

 

you can use most any finder scope, odds of finding whatever was originally supplied on a EARLY C8 are slim to none and anyways those likely were 6x30 and not very good..   I like 9x50 erect field right angle finders, most made today have 'vixen shoes' and part #RDPS here, https://www.scopestuff.com/ss_rdpb.htm will attach to existing accessory screws on the scope OTA and hold a finder like... https://www.amazon.com/Astromania-Angled-Finder-Upright-Non-Reversed/dp/B01FA18G18

I completely disagree.

Being a low serial number scope (#359) he should make the effort to put it back to as close as possible to original.

And it isn't that hard to find a suitable one.

 

Compare Jordan's finder on C8 #66 (I believe it's marked circle T)

To the one on my 1979 (marked Oval M)

And they apparently used similar ones for quite sometime.

I see these style of finders fairly often in the classifieds and I'll bet if he put up a want ad, it wouldn't take long to find one.

[Jeff L]

There are no 'schematics' to telescope optics as they aren't electrical circuits.   I would be VERY hesitant to remove the optics as its easier to damage them, and the primary at least really doesn't look to be in that bad condition.

 

you can use most any finder scope, odds of finding whatever was originally supplied on a EARLY C8 are slim to none and anyways those likely were 6x30 and not very good..   I like 9x50 erect field right angle finders, most made today have 'vixen shoes' and part #RDPS here, https://www.scopestuff.com/ss_rdpb.htm will attach to existing accessory screws on the scope OTA and hold a finder like... https://www.amazon.com/Astromania-Angled-Finder-Upright-Non-Reversed/dp/B01FA18G18

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[deSitter]

I completely disagree.

Being a low serial number scope (#359) he should make the effort to put it back to as close as possible to original.

And it isn't that hard to find a suitable one.

 

Compare Jordan's finder on C8 #66 (I believe it's marked circle T)

66-Finder.jpg

To the one on my 1979 (marked Oval M)

79-Finder.jpg

And they apparently used similar ones for quite sometime.

I see these style of finders fairly often in the classifieds and I'll bet if he put up a want ad, it wouldn't take long to find one.

I think it is the same 6x30mm finder found on all sorts of scopes. Ramsden eyepiece, lousy edge. Good objective.

 

-drl

[pierce]

I think it is the same 6x30mm finder found on all sorts of scopes. Ramsden eyepiece, lousy edge. Good objective.

 

-drl

you left out, narrow FOV, no eye relief, dim.

[CCD-Freak]

I completely disagree.

Being a low serial number scope (#359) he should make the effort to put it back to as close as possible to original.

And it isn't that hard to find a suitable one.

 

Compare Jordan's finder on C8 #66 (I believe it's marked circle T)

66-Finder.jpg

To the one on my 1979 (marked Oval M)

79-Finder.jpg

And they apparently used similar ones for quite sometime.

I see these style of finders fairly often in the classifieds and I'll bet if he put up a want ad, it wouldn't take long to find one.

I have my friend Phil's old C8 sn 195 and here is a picture of the finder.  Hope this helps identify what finder is supposed to be on yours.

 

[Jeff L]

There are no 'schematics' to telescope optics as they aren't electrical circuits.   I would be VERY hesitant to remove the optics as its easier to damage them, and the primary at least really doesn't look to be in that bad condition.

 

you can use most any finder scope, odds of finding whatever was originally supplied on a EARLY C8 are slim to none and anyways those likely were 6x30 and not very good..   I like 9x50 erect field right angle finders, most made today have 'vixen shoes' and part #RDPS here, https://www.scopestuff.com/ss_rdpb.htm will attach to existing accessory screws on the scope OTA and hold a finder like... https://www.amazon.com/Astromania-Angled-Finder-Upright-Non-Reversed/dp/B01FA18G18

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