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Re: (IAAC) Obj: M34 - Inst: Orion Optics 250MM F4.8 Vixen GP/DX



Thanks scott,
i have planned to remove the primary tonight and just check it over but i suspect i have no need just a case of putting my mind at rest. 
Thanks for all the input everybody i have relaxed and my warranty has been reinstated so alls well that ends well
Barry
> Don't Panic :-) This is an equatorial mounted reflector correct ? The 
> mirror in an scope on a german equatorial is going to need more restraint 
> than that of a Dobsonian due to the flips required when going from one side 
> of the mount to the other.   The important thing is that the optics in the 
> mirror are not pinched in anyway. The screws should restrain the mirror but 
> not be pressing on the glass. On my scope I usually run the screws in with 
> my fingers until they just touch then back off slightly, I do the same for 
> the mirror clips. This has worked for the past 15 years without any damage 
> to the optics.
> 
> Scott Hogsten
> 
> 
> At 03:46 PM 1/21/02  0000, you wrote:
> >
> >Thanks Jerry and everyone else.
> >
> >The scope in question is an orion optics Uk model and is a newtonian 
> >reflector at 250mm, The gentlemen who helped me i believe new not to 
> >overtighten the mirror, but felt that the nylon screws will indeed give a 
> >little in themselves. But he was adamant that the mirror should not move 
> >in its mounting certainly as much as it was. He had tried to collimate the 
> >scope pre the adjustments and could not get it correct. the tube was 
> >rolled along the workbench carefully and he had noticed the mirror moving, 
> >It was at this point that he had decided to take the scope apart. 
> >retightend the screws then collimated the scope. Now it is in collimation 
> >no problems in fact my views are visibly better stars are dots not 
> >streakes of lights. However the company concerened is a telescope maker a 
> >small comapny but they make thier own mirrors and tubes etc. the gentlemen 
> >i talk to owns this small company. If it had been a salesman i would have 
> >not listened to him because of the stature of the gentlmen helping me i 
> >mean a Dr of physics and a practising lecturer on astronomy and 
> >cosmology.  but because of whom i talked to i feel very confused.
> >
> >
> > > Barry,
> > >     Your telescope is a refractor, am I correct?  I am not sure if the
> > > mirror in a refractor is supposed to be tight, but I wouldn't think it
> > > should be very tight.
> > >
> > >     I own a 14.5" Starmaster truss mounted dobsonian reflector.  I do know
> > > that my mirror is extremely loose.  Yes, I said loose.  It rests on a mount
> > > that allows it to flex with temperature variations.  When I am transporting
> > > the mirror in the mount, it will move around a lot.  When it is in the
> > > telescope, it is resting on the mount and although you don't hear it moving
> > > when the telescope is moved, it is free to move ever so slightly if it 
> > needs
> > > to so it can flex with temperature variations.  If I tightened the mirror
> > > down to keep it from moving, what I would cause is the inability of the
> > > mirror to expand or contract with temperature variations and thus it may
> > > actually bend slightly because it doesn't have room to stretch.  The 
> > bending
> > > is probably what your manufacturer is concerned with because the bending
> > > will result in astigmatism, if I'm not mistaken.  In short, mirrors need
> > > room to move.
> > >
> > >     If I were you, I would contact the company and have their technical
> > > support get the thing correct and have them walk you through the steps to
> > > get it collimated correctly.  I don't own a refractor, so I can't help you
> > > on this one.
> > >
> > >     Different subject.  I noticed in your observing reports that when the
> > > report calls for magnification, you entered the focal length of your
> > > eyepiece.  Actually, magnification is figured by dividing the focal length
> > > of your telescope by the focal length of your eyepiece.  If, for instance,
> > > the focal length of your telescope is 1200mm and you use a 25mm eyepiece,
> > > your magnification is 48x.  I looked in the Orion catalog and could not 
> > find
> > > your scope.  Is it a refractor?
> > >
> > > Hope this helps.
> > > Jerry.
> > >
> > >
> > > ----- Original Message -----
> > > From: <barry.sharpe@btinternet.com>
> > > To: <netastrocatalog-announce@atmob.org>
> > > Sent: Monday, January 21, 2002 6:53 AM
> > > Subject: Re: (IAAC) Obj: M34 - Inst: Orion Optics 250MM F4.8 Vixen GP/DX
> > >
> > >
> > > Hi everyone,
> > >
> > > Perhaps someone can help me, I took my telescope to a member of our local
> > > astronomical society. Who just happens to be a Dr of physics works at our
> > > university. After repeated attempts at collimating my scope he could 
> > not get
> > > it right. so he stripped my scope removed primary and secondary 
> > mirrors. And
> > > found the offending item to be a nylon screw that holds with 2 others the
> > > side of the mirror to be lose.
> > > he tightened it rebuilt the scope and collimated it no problems. because it
> > > is a new scope he suggested i phone the makers and make a little complaint.
> > > Whilst doing so the makers informed me that this was incorrect and that 
> > what
> > > the gentlemen did may cause an astigmatism in my mirror. And would have
> > > invalidated any warranty on my scope. Firstly thier was a lot of play 
> > in the
> > > mirror so much so that if you moved the scope you could feel the mirror 
> > move
> > > inside. The telescope makers claim that this would not have affected the
> > > collimation. However i said surly it must do because in effect if the 
> > mirror
> > > moves off center then the collimation is bound to be affected. He denied
> > > this rather vermently and told me that what we had done was wrong. The
> > > gentlemen that had helped me is a long standing astronomer who lectures
> > > cosmology clases and looks after all the obervatories as well as radio
> > > telescopes surly he must know. my telescope since the rebuild is performing
> > > far better than it ever did. Am i to worry i don't believe he tightened it
> > > solidily just enougth to stop it moving around. Any thoughts would be
> > > greatly appeciated.
> > > Barry
> > >
> > >
> > >
> > > > ----
> > > >
> > > > Observation Poster: Barry Sharpe <barry.sharpe@btinternet.com>
> > > >
> > > > Observer: Barry Sharpe
> > > > Your skills: Beginner (< one year)
> > > > Date/time of observation: 19th January 2002 19:30 UT
> > > > Location of site: Welwyn Garden City  (Lat 51:47:24 , Elev 0:10:45 )
> > > > Site classification: Suburban
> > > > Sky darkness: 7 <1-10 Scale (10 best)>
> > > > Seeing: 4 <1-10 Seeing Scale (10 best)>
> > > > Moon presence: Minor - crescent or far from object
> > > > Instrument: Orion Optics 250MM F4.8 Vixen GP/DX
> > > > Magnification: 25mm
> > > > Filter(s): None
> > > > Object(s): M34
> > > > Category: Open cluster.
> > > > Class:
> > > > Constellation: Per
> > > > Data: mag   size
> > > > Position: RA :  DEC :
> > > > Description:
> > > > M34 found nice open cluster near zenith, spread out cluster in 25mm. Many
> > > are
> > > > white stars suggesting young cluster stars fill FOV. One double in centre
> > > of FOV, 50 - 100 stars; quiet a few pairs of stars, nice pinpoints of 
> > light.
> > > Very
> > > > nice open cluster. could not discern any particular pattern but view was
> > > constantly interupteb by cloud.
> > > > --
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