Jump to content

  •  

CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.

Photo

celestron 125mm f/6 telephoto lens

  • Please log in to reply
8 replies to this topic

#1 akdwivedi

akdwivedi

    Mariner 2

  • -----
  • topic starter
  • Posts: 217
  • Joined: 17 Apr 2021
  • Loc: Singapore

Posted 28 January 2022 - 04:15 AM

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

  • C5 front.jpeg
  • C5 serial 2.jpeg
  • C5 ring mounted.jpeg
  • C5 ring mounted.jpeg

  • Neptune, deepwoods1, mashirts and 5 others like this

#2 Senex Bibax

Senex Bibax

    Viking 1

  • *****
  • Posts: 993
  • Joined: 01 Feb 2019
  • Loc: Ottawa, ON

Posted 28 January 2022 - 08:15 AM

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!


  • telesonic likes this

#3 Terra Nova

Terra Nova

    ISS

  • *****
  • Posts: 27,077
  • Joined: 29 May 2012
  • Loc: 39.07°N, 229m AMSL, USA

Posted 28 January 2022 - 12:33 PM

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?



#4 telesonic

telesonic

    Viking 1

  • *****
  • Posts: 645
  • Joined: 17 Oct 2016
  • Loc: SW Idaho

Posted 29 January 2022 - 12:12 AM

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.

 

C5 750 2
Grab And Go Scope Gear
C5 Finder Test

 

 


  • mdowns and akdwivedi like this

#5 akdwivedi

akdwivedi

    Mariner 2

  • -----
  • topic starter
  • Posts: 217
  • Joined: 17 Apr 2021
  • Loc: Singapore

Posted 29 January 2022 - 12:13 AM

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.

#6 akdwivedi

akdwivedi

    Mariner 2

  • -----
  • topic starter
  • Posts: 217
  • Joined: 17 Apr 2021
  • Loc: Singapore

Posted 29 January 2022 - 12:57 AM

 

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 likes this

#7 telesonic

telesonic

    Viking 1

  • *****
  • Posts: 645
  • Joined: 17 Oct 2016
  • Loc: SW Idaho

Posted 29 January 2022 - 05:43 PM

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 likes this

#8 akdwivedi

akdwivedi

    Mariner 2

  • -----
  • topic starter
  • Posts: 217
  • Joined: 17 Apr 2021
  • Loc: Singapore

Posted 30 January 2022 - 11:57 PM

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.
 



#9 photoracer18

photoracer18

    Aurora

  • *****
  • Posts: 4,900
  • Joined: 02 Sep 2013
  • Loc: Martinsburg, WV

Posted 31 January 2022 - 07:20 PM

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.


  • akdwivedi likes this


CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.


Recent Topics






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics