8 replies to this topic

[akdwivedi]

I dont know if it qualifies as classic scopes. I acquired a used Celestron 125mm f/6 telephoto lens. It has a huge secondary mirror, came with a small mount which could be screwed directly to a arca swiss plate and mounted on a ball head.

 

it certainly looks very old design, has a label says made in USA and has a 4 digit serial number.

 

I tried to unscrew the photo mount and see if I could attach a standard vixen dovetail but it wasnt possible. the distance between the two screws was too wide to attach the vixen dovetail. So I got a 140MM Vixen mounting ring and they fit perfectly. I have ordered a smaller 150mm vixen doevtail, but in the meantime have mounted it on a 210mm vixen plate. The rings are white in colour, I could not get a black ring.

 

It balances very well on a az gti. I had an hour of clear skies before clouds rolled in, the stars are sharp and round. The view was quite bright compared to my F/10 C6, I guess it has to do with f/5.6 even though it has 5inch aperture compared to C6. I was thinking the collimation would be terrible, but surprising it held very well. I checked in out of focus disks and they look very different with a huge central disc (which is probably due to large central obstruction). I will try to fine tune collimation before I try any photography.. For visuals the stars are good.

 

This looks like an ultimate light weight setup - az gti, carbin fibre tripod and C5 f/5.6.. the rings look more heavier than the scope. Any suggestions for better rings.

Attached Thumbnails

• 
• 
• 
• 

[Senex Bibax]

I dont know if it qualifies as classic scopes. I acquired a used Celestron 125mm f/6 telephoto lens. It has a huge secondary mirror, came with a small mount which could be screwed directly to a arca swiss plate and mounted on a ball head.

 

it certainly looks very old design, has a label says made in USA and has a 4 digit serial number.

 

I tried to unscrew the photo mount and see if I could attach a standard vixen dovetail but it wasnt possible. the distance between the two screws was too wide to attach the vixen dovetail. So I got a 140MM Vixen mounting ring and they fit perfectly. I have ordered a smaller 150mm vixen doevtail, but in the meantime have mounted it on a 210mm vixen plate. The rings are white in colour, I could not get a black ring.

 

It balances very well on a az gti. I had an hour of clear skies before clouds rolled in, the stars are sharp and round. The view was quite bright compared to my F/10 C6, I guess it has to do with f/5.6 even though it has 5inch aperture compared to C6. I was thinking the collimation would be terrible, but surprising it held very well. I checked in out of focus disks and they look very different with a huge central disc (which is probably due to large central obstruction). I will try to fine tune collimation before I try any photography.. For visuals the stars are good.

 

This looks like an ultimate light weight setup - az gti, carbin fibre tripod and C5 f/5.6.. the rings look more heavier than the scope. Any suggestions for better rings.

Looks like a C90 on steroids!

[Terra Nova]

It might be nice as a sort of RFT. I assume the visual back can take full advantage of a 1.25” diagonal and eyepieces without vignetting?

[telesonic]

These little scopes are pretty rare, and just for information - or if you are curious, there was a topic (registry) on here about serial numbers on the C5's, so you might want to look at that. It might give you a little more data on when it was made, your scope is a pretty low serial number.

 

I have one of these C5 telephoto's in my astro / photo kit, and yes at F/6 focal ratio it is a relatively fast scope for such a short length, due to the SCT design. And, as you have come to know, it has a rather large secondary mirror. I've had mine for several years, and I really like it for a grab-and-go scope - but there are some things that I've learned about it over that time.

 

1. The original collimating screws on the secondary can be easily stripped, when trying to collimate with a slotted screwdriver. (I learned this the hard way)

2. You can buy better hex-head screws from a hardware store, or change them out to Bob's Knob's... which is what is on my C5 now. They work, they could be better though. I don't recall what the thread diameter of pitch is, but it should be easy to find should you need to replace the stock screws.

 

I think your rings are fine, and I'm not sure how you could improve them... there aren't many options as far as I'm aware of. I used similar rings for my C5, they work.

Finder mounting on these isn't difficult, it just takes a little ingenuity - on mine, I removed the tripod mounting bracket from the scope, and used the stock tripod mounting location holes in the rear cell for a small finder shoe - either for a GLP or optical finderscope.

 

 

 

[akdwivedi]

Yes, it has a visual back and accepts a 1.25inch diagonal and eyepieces. I tested this with a 20mm and a 10mm eyepiece and they worked fine without any vignetting. The views of orion were quite nice yesterday with this setup. 750mm at f/6 is almost as good as my orion 120st but this is extremely light compared to that scope.

[akdwivedi]

 

These little scopes are pretty rare, and just for information - or if you are curious, there was a topic (registry) on here about serial numbers on the C5's, so you might want to look at that. It might give you a little more data on when it was made, your scope is a pretty low serial number.

 

I have one of these C5 telephoto's in my astro / photo kit, and yes at F/6 focal ratio it is a relatively fast scope for such a short length, due to the SCT design. And, as you have come to know, it has a rather large secondary mirror. I've had mine for several years, and I really like it for a grab-and-go scope - but there are some things that I've learned about it over that time.

 

1. The original collimating screws on the secondary can be easily stripped, when trying to collimate with a slotted screwdriver. (I learned this the hard way)

2. You can buy better hex-head screws from a hardware store, or change them out to Bob's Knob's... which is what is on my C5 now. They work, they could be better though. I don't recall what the thread diameter of pitch is, but it should be easy to find should you need to replace the stock screws.

 

I think your rings are fine, and I'm not sure how you could improve them... there aren't many options as far as I'm aware of. I used similar rings for my C5, they work.

Finder mounting on these isn't difficult, it just takes a little ingenuity - on mine, I removed the tripod mounting bracket from the scope, and used the stock tripod mounting location holes in the rear cell for a small finder shoe - either for a GLP or optical finderscope.

 

 

 

 

 

Thanks for tips. Certainly the collimating screws need replacement. I will also check the mount for a small guidescope. the black rings look lot better. 

[telesonic]

Thanks for tips. Certainly the collimating screws need replacement. I will also check the mount for a small guidescope. the black rings look lot better. 

You are welcome, glad to help. These are cool little spotters / scopes.

 

I don't recall what the thread is on the collimating screws is, diameter and pitch isn't listed on Bob's Knobs website - but I do know I have some hex ones around here in my parts box. If I can find them, I will measure them for you.

 

One other option for mounting a finder / guidescope on this kind of setup: you could use a flat aluminum bar across the top of the rings, and add your finder bracket to that. I went with the stock tripod mounting location, and used a bracket from Scopestuff (though I don't recall which part number it was) which has slotted holes for adjustment. I think it was #RDPS. I bought shorter mounting screws from the hardware store, as to not hit the mirror too.

 

The black rings on mine are actually purchased for my older Vixen/Celestron C-4.5 reflector, and they fit either scope without additional felt. I bought those hinged rings on Orion's website some years ago. They should fit your C5 if it's not the Vinyl wrapped tube, which I don't think yours is. (it look's painted to me)

 

Being a fast scope, they are kinda tricky to collimate - (not too difficult, just moreso than a C8 SCT @ F/10) so if you do replace the screws, keep that in mind.) It's also best to remove one, and replace - one at a time. I did mine in the daytime, with a distant object centered in a reticle eyepiece, then once the new screw was in... I re-centered it by adjusting that screw, then again for the other two. This kept it fairly well aligned, with only a few minor adjustments needed on Polaris at night.

 

Cheers,

T

[akdwivedi]

You are welcome, glad to help. These are cool little spotters / scopes.

 

I don't recall what the thread is on the collimating screws is, diameter and pitch isn't listed on Bob's Knobs website - but I do know I have some hex ones around here in my parts box. If I can find them, I will measure them for you.

 

One other option for mounting a finder / guidescope on this kind of setup: you could use a flat aluminum bar across the top of the rings, and add your finder bracket to that. I went with the stock tripod mounting location, and used a bracket from Scopestuff (though I don't recall which part number it was) which has slotted holes for adjustment. I think it was #RDPS. I bought shorter mounting screws from the hardware store, as to not hit the mirror too.

 

The black rings on mine are actually purchased for my older Vixen/Celestron C-4.5 reflector, and they fit either scope without additional felt. I bought those hinged rings on Orion's website some years ago. They should fit your C5 if it's not the Vinyl wrapped tube, which I don't think yours is. (it look's painted to me)

 

Being a fast scope, they are kinda tricky to collimate - (not too difficult, just moreso than a C8 SCT @ F/10) so if you do replace the screws, keep that in mind.) It's also best to remove one, and replace - one at a time. I did mine in the daytime, with a distant object centered in a reticle eyepiece, then once the new screw was in... I re-centered it by adjusting that screw, then again for the other two. This kept it fairly well aligned, with only a few minor adjustments needed on Polaris at night.

 

Cheers,

T

thank you.. Celestron lists M3x10mm as the size of collimating screws for C5 (https://www.celestro...n-optical-tubes).. I guess it will work, but a confirmation will certainly be appreciated.
 

[photoracer18]

I have owned three of those, even 2 at a time. I find that on average they tend to be slightly better than the F10 models. I could be prejudiced a little. McBroom's Camera Price Guide includes them in the lens section with a recommendation if you don't mind the typical OOF donuts on bright objects. Not seen in astro images.