Re: [ATM] Recognising TDE

["James Mulherin" <jcmulherin@opticalmechanics.com>]

Rachmand:

> Sincere thanks for clarification.
> May I ask one more thing.
> Is there also any sign for recognising TUE by star
> test?

As you may know, TDE is much more common than TUE just because TDE is so
easy to make (even by accident). I'm probably not the best person to answer
the TUE/star testing question but I'll take a shot at it. I did consult
Suiter's Star Testing Astronomical Telescopes but the book only talks about
the effects of TDE. 

Any way, here goes. A TDE spreads light radially outward from the star's
image causing spikes and causing loss of contrast. On the other hand, a TUE
causes light to come to focus ahead of the light coming from the good part
of the mirror. In fact, this light crosses the focus point and then
continues on radially outward. I suspect that the effect of a TUE is
essentially the same as a TDE, although I doubt that anyone could produce in
a TUE the kind of extremely steep slope that can be produced in a TDE.

Can any one else comment on this. Is a mild TUE effectively the same as a
mild TDE in the star test? 

James

James Mulherin
Optical Mechanics, Inc.
jcmulherin@opticalmechanics.com
www.opticalmechanics.com
Tel: (319) 351-3960
Fax: (319) 351-3943

> 
> With regards
> Ramchand
> --- James Mulherin <jcmulherin@opticalmechanics.com>
> wrote:
> 
> > Rachmand:
> >
> > > May I be a bit clear when you say that - ""If you
> > have
> > > TDE the focused star will be hairy"". It denotes
> > that
> > > I will be seeing several tiny spikes on the outer
> > > diffraction ring going in different directions? Or
> > the
> > > outer big ring itself would be composed of several
> > > hairs?
> >
> > There will be many small spikes radiating outward
> > from the focused star
> > image. You probably won't see the first diffraction
> > ring as it will be
> > washed out by the spikes.
> >
> > If you suspect you have TDE you can confirm it by
> > masking the edge of your
> > mirror. Start by masking the outer .5" of the
> > mirror. Most TDE is not wider
> > than .5" Mask the mirror and see if the spikes go
> > away.
> >
> > James
> >
> > James Mulherin
> > Optical Mechanics, Inc.
> > jcmulherin@opticalmechanics.com
> > www.opticalmechanics.com
> > Tel: (319) 351-3960
> > Fax: (319) 351-3943
> >
> > >
> > > With regards
> > > Ramchand
> > > > star will be hairy.
> > > --- James Mulherin
> > <jcmulherin@opticalmechanics.com>
> > > wrote:
> > >
> > > > Hello
> > > >
> > > > > <<On the sky you can usually recognize a
> > turned
> > > > edge
> > > > > immediately>>
> > > > >
> > > > > May I know what are the signs of recognising
> > TDE
> > > > > immediately and unambiguously?
> > > > >
> > > > > RCVirwani
> > > >
> > > > Focus on a bright star. If you have TDE the
> > focused
> > > > star will be hairy. The
> > > > turned edge represents a steep outward slope
> > that
> > > > throws light radially away
> > > > from the star image. Some of the light goes into
> > > > making up the radial
> > > > "hairyness" and the rest is spread out across
> > the
> > > > field of view, reducing
> > > > contrast.
> > > >
> > > > James
> > > >
> > > > James Mulherin
> > > > Optical Mechanics, Inc.
> > > > jcmulherin@opticalmechanics.com
> > > > www.opticalmechanics.com
> > > > Tel: (319) 351-3960
> > > > Fax: (319) 351-3943
> > > >
> > > >
> > >
> > >
> > > Yes, you can easily make a big telescope not a
> > toy.
> > > Click below for detailed information both in Hindi
> > and English :
> > >
> > >
> >
> http://in.geocities.com/rc_virwani/make_telescope_yourself.htm
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> >
> __________________________________________________________
> > > Enjoy this Diwali with Y! India Click here
> > > http://in.promos.yahoo.com/fabmall/index.html
> >
> >
> 
> 
> Yes, you can easily make a big telescope not a toy.
> Click below for detailed information both in Hindi and English :
> 
> http://in.geocities.com/rc_virwani/make_telescope_yourself.htm
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> __________________________________________________________
> Enjoy this Diwali with Y! India Click here
> http://in.promos.yahoo.com/fabmall/index.html

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