Dobsonian mount not staying tight

[bntwillis]

Hey All,

I have a Celestron Starhopper with a dobsonian mount. I have taken it out a few nights and have really enjoyed using it. My problem is, the two handles that tighten the tube at a specific height don't seem to work real well and the tube never seems to stay locked. So even when I do get an object in my sites, I have to constantly hold the tube with my hands to keep it set. It is so bad I have not been able to calibrate the siting scope. Any suggestions.

Thanks in advance.

Regards,

Bob

[kernowstargazer]

I found this when i was first using my Skywatcher 150 dob but then relised that one of the handles needs to go on the opposite side of the focuser and the handle with the bearing on goes on the side with the focuser and this what i use to loosen or tighten depending on what and where im viewing and the other handle stays perminantly tightish.

[bntwillis]

Thanks, I will check that out.

[Moonshane]

it may also be that if you are using heavier eyepieces that you need to add a small counterweight system at the primary end.

[bntwillis]

So, here is what the problem is. The problem is not the dobsonian mount, instead it is with the two brackets that attach to the tube of the scope (which in turn attach to the mount). Both of them have become loose and there is a lot of play (they are not tight to the scope). I tried to tighten them up (each is attached with two screws that go into the body of the tube and into the interior of the scope). Well I got one unscrewed and the nut and washer fell into the tube of the scope. Fortunately they did not fall down onto the mirror. This made me realize I am going to need access into the interior of the scope to get all of these nuts, washers and screws tightened. So now, what is the best way to get access AND be able to get the scope back together with minimal effort. Do I remove the mirror at the top of the scope and gain entry that way? Or do I go through the bottom (where the primary mirror is)? Any advice would be greatly appreciated.

Thanks,

Bob

[Moonshane]

personally, I'd remove the primary. it's quite straight forward, just go carefully and ensure nothing drops or touches the primary surface.

you'll need to collimate afterwards either way (as you should before every session in any case).

hope all goes well.

[bntwillis]

thanks Moonshane, that is how I will spend my morning here.

[kernowstargazer]

Good luck with it. I want to flock my tube and it scares the living daylights out of me taking the OTA apart.

[bntwillis]

Easy as pie. Thank you so much. No problem at all. I did notice the primary had a bit of dust on it. What is the best way to clean that, this is for future reference. Just got done collimating.

[bntwillis]

oh - kernowstargazer - thanks for the tip about the handles with the bearing being on the side of the scope with the focuser, changed that too. makes sense now that you say it, easy access for when viewing.

[Moonshane]

re the dust the best way to deal with it is ignore it. a mirror has to be pretty bad to affect the view at all. you can clean it if you must but it will not benefit you and could potentially detract from the view if you leave micro scratches.

if you want to then this thread is good http://stargazerslounge.com/beginners-help-advice/134032-cleaning-mirror.html

[kernowstargazer]

No worries mate as i made that mistake when i first took mine out for a view. I aint cleaning my mirror until i cant see my reflection down the OTA:D.