Re: [bigdob] Re: ATM 32" observing reports, close to the end

["at making" <atmaking@hotmail.com>]

>This is "music in my eyes". At really good high mountain sky conditions the
>Veil reveals in a 20" more beauty and detail, than the mind can catch
>already. Next year I will see, how it looks like in a 32", when we 
>hopefully
>will have finished our "big one".

I wish you great time at the eyepiece ! During one of the night, a 24" was 
next to it. Their is a lot to see in a 24" but all the details visible "at 
the limite" are easy in the 32" and of course you see deeper. The better the 
sky the bigger the gap. It also depends of the object, sometime the gap was 
not that big and sometime it was important.

>Of particular interest for us is the fact, that a 40 mm meniscus is stable
>enough. So I suppose, that our 57 mm thick plano concave blank should show
>even with a classical type cell no astigmatism too? I think we should
>consider your "piano wire" lateral support as well.

I can't say anything about a 57 mm blank may be it's not that far from a a 
40 mm meniscus. I don't kwow. If you want to user piano wire, you might 
start with a 2,5 mm diameter wire. The 22" got 1,5 mm, the 32" 2 mm. As your 
blank is heavy, the cell is really very important. The heavier the harder 
the problem. On the 32", the cell is seperated from the lateral support. 
Lateral support or a part of the mirror box but the cell itself move along 
the optical axe on the collimation screw. It's not like in an obsession like 
mirror cell or, starmaster. I was afraid to have possible flexion while 
going to horizon to zenith. If the lateral support are part of a very strong 
mirror box, it can't move. With classical system, I mean lateral support, 
sling or other system, their is always possible flexion in the cell itself 
while going up and down. If you choose to put lateral support or any other 
system on the cell itself, take very strong support to avoid any shifting of 
the primary which means decolimation and mirror movement.




>I wish you good luck with the tracking system too.


Thanks  ! I don't worry about it, the view was so good that we spend every 
second at the eyepiece !

Frédéric Géa
http://astrosurf.com/altaz/index_e.htm

>Stathis Kafalis
>http://www.geocities.com/dobsonstathis
>
>----- Original Message -----
>From: "at making" <atmaking@hotmail.com>
>To: <atm@shore.net>; <bigdob@yahoogroups.com>
>Sent: Monday, August 19, 2002 10:00 AM
>Subject: ATM 32" observing reports, close to the end
>
>
> >
> >
> > Hi,
> >
> > For the first time, I have observed in the 32  with a tuned astatic 
>cell.
>A
> > friend who know this kind of cell very well tune it in few minutes. I 
>was
> > not far but now is good. The difference in the view is simply amazing ! 
>I
> > was afraid to have some astigmatism but fortunately there is nothing
>visible
> > while going from zenith to horizon. The last part to tune is the 
>tracking
> > but the first tests are a big promise. It could have been finished but a
> > lack of time and our enthusiasm to share time at he eyepiece under a 
>good
> > sky as give us problem J
> >
> > The scope is easy to setup, about 10 minutes. Currently the primary is
> > transported in a separate box. The mirror box and rocker or on a 
>trailer.
> > The primary and top cage in a station wagon. Two people "drop" the 
>mirror
>in
> > the cell, remove wheels, put the truss, the cage, baffle system and it's
> > ready. First surprise, on 4 setup, twice the scope didn't need to be
> > collimate ! and and an other time a small collimation. I know try to
>always
> > installed the truss at the same place and this way, it does not seem to
> > require collimation. May be I will don't need to have the remote
>electrical
> > collimation system.
> >
> > The place was a pass in south of france, at 4800 ft. Fun, we decided to 
>go
> > at this place at night, so the trip and setup was done during the night.
>The
> > sky was great naked eye, with a very broad and full of detailed Cygnus
>area.
> > As for many new scope, we spend  first observing session on classical
>bright
> > object. We were not disappointed to say the least.
> >
> > M27 was not the classical hourglass shape. It was full of thin details,
>and
> > extension, only visible on heavy processed CCD images. The extension are
> > like an "echo" of the classical shape.
> >
> > The veil nebula was a AMAZING view ! the central part (between the two
> > brightest arc) was like the brightest arc in a 20" ! You have to use 
>high
> > quality CCD shot to see as much details and in many case it's more
> > impressive at the eyepiece. The broadest part near 52 cygni remember me 
>a
> > all the ramifications of  rivers are branches of a tree. Complex, hard 
>to
> > describe. It was with the paracorr and nagler 20 mm eyepiece.
>Unforgettable.
> >
> > M33, at low power (paracorr +20 mm nag), NGC604 got a distinct shape 
>with
>a
> > haze around it , and some  stars (with good seeing). I will use higher
>power
> > and try to make some drawing next time as it will be at an even better
>dark
> > site.
> >
> > 6543 was great. With good seeing, all classical details were visible.
>Green,
> > with something like a dark brown/deep red faint line at is perimeter. 
>The
> > faint galaxy next to it was easy. Around cat's eye, the haze was visible
>and
> > something I never notice before, a reinforcement of this haze was 
>visible,
> > opposite to the direction of the galaxy if memory serves me.
> >
> > M13 was big, fully resolved. The faint galaxy between M13 and ngc 6207 
>was
> > easy to see and got a shape.
> >
> > We also spend time on NGC253, 891, M15, Stephan's quintet,
> >
> > I can't wait to have the tracking as it full capacity. It should have 
>been
> > already finished but when you begin to jump from an object to an other,
>it's
> > hard to stop 5 minutes J.
> >
> > Strange things happen, during humid night, the graphite fabric I used to
> > cover parts of the cage and focuser board, and in a smaller proportion,
> > other parts of the cage are covered with humidity. The truss itself 
>(also
> > graphite tubing but made an other way) don't seem to suffer to much of
>that
> > problem. A good point, this graphite tubing is not cold during cold 
>night
>so
> > gloves are not necessary like for alu truss. Rigidity of the full
>structure
> > seems to be excellent. Something I will need to modify a little is the
>size
> > of the 3 pad that touch the ground, a little wider will be better for
> > stability on "unstable" grass place.
> >
> > Piano wire seems to be good. They are 2 mm in diameter and support a 44
>kgs
> > (around 97 lbs). Their "free part"  are not very long (around 20 mm) but
> > seems to be enough. To use the scope as it full capacity, it's good, 
>when
> > the collimation is finished, to aim the scope at zenith, move the 
>primary
>by
> > hand for few millimetres and aim the scope at horizon to let it take is
> > position without any stress. Good point to, the meniscus seems to be 
>very
> > rigid. I even wondering if it could not have been put on a 18 points ! I
> > know that sound an exaggeration but it's not the case. The meniscus is 
>40
>mm
> > thick, but seems to have a stiffness close to what can give a 24" 40 mm
> > thick, flat shape. I will speak about that with Luc Arnold soon. The 
>shape
> > seems to be a real bonus. If I'm not lazy, I might  make an even simpler
> > cell (astatic with 18 points) one day to see how the glass react.
> >
> > Sorry for the double mail for people whom are on atm and bigdob.
> >
> > Frédéric Géa
> > http://astrosurf.com/altaz/index_e.htm
> >
> >
> >
> >
>
>




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