Coulter 10.1" red tube compact telescope advice required

[MrZuiko]

Hi everyone,

I have just picked up a Coulter 10.1" f4.5 red tube dobsonian wow it's huge and I understand a classic telescope from the USA.

I didn't pay a lot for it as I was told that the optics were very dusty and dirty,on closer inspection when I got home I found the mirror to be more than just dirty it's tarnished and will require re-covering as well as the secondary which I have to say is massive.......compared to the 6" f8 I'm making which has David Hinds optics and I'm very near to completeing it,you can  see in the back ground on it's pipe mount.

Now what I would like your thoughts on is the Coulter worth sending off to get recovered,I had planned to re make the rocker box out of 3/4" ply,repaint the sonotube etc but is the mirror worth the expense and how much and where would I send it if I restore this telescope.

Your thoughts and advice please!

Clear skies all.

                   Ash.

Edited April 25, 2022 by MrZuiko

[JeremyS]

These Coulter mirrors were of very variable quality. Some very good and some almost unusable. No way of knowing how yours is in its current state.

the other consideration is where the mirror is damaged. Hopefully it is just the coating that needs replacing, rather than damage to the surface, but difficult to tell from a pic.

[Louis D]

Clean off the dust and see if you can do some basic star testing with the remaining reflectivity to get some idea of it's figure.  If one or the other mirror is completely hazy, I guess you're out of luck on that front.

These scopes really contributed to Dobs being written off for use only as light buckets for DSOs rather than as serious planetary observing tools as well.  Also, the mechanics were pretty crude as I recall.  FWIW, I haven't seen one at a US star party in at least 20 years.  Some were converted to truss Dobs after having their mirrors refigured and recoated.

[MrZuiko]

Hi,

Thanks for your replies......this is the condition of the mirror with the dust removed!!! I was thinking the same to get it out and test it.

Here in the UK I have found out it will cost almost £230 to have both the mirror and secondary recoated! I'll probably end up giving it away!

 

Ash.

[Louis D]

Give it first (and possibly last) light and let us know.  Nothing ventured, nothing gained.

[NGC 1502]

Although the mirror is in poor condition a star test will still be valid.   If it were me, I’d collimate and try it.  Make sure it’s fully cooled and learn how to star test.  A basic star test at medium to high power tells a lot. Be aware that the star test can reveal minor errors of no real consequence, so be critical but not over critical.

Only you can decide if it’s worth spending the money.  If the mirrors are poorly figured then a recoat will mean it’s a light bucket for galaxies and faint nebula.  
 

On the other hand you may just get a nice surprise and it’s a competent all-rounder👍

[MrZuiko]

Thanks guys for your help and advice..........

Ash.