78 replies to this topic

[refractory]

A motorized chair itself can act as azimuth part of the mounting, so that only altitude is an issue for a chair-mount (can I call it that?). I'm not thinking of tracking, equatorial, etc.

An F/4 8 inch tube can easily fit between the lap and eye for most adults (I'm somewhat on the short side and its alright for me). So I'm thinking something along the lines where the tube pivots for azimuth NEAR the eyepiece, so that the viewer doesn't have to bend over much. Counterweight for the tube ahead of the mirror (like in those old ATM scopes), maybe another one for the tube/mount behind the chair so the weight doesn't come down on the viewers legs. Or other architectures...

Jess Tauber

[Art Bianconi]

I believe that making any wheel chair, motorized or not, an integral part of the scope is a mistake.

For one, it means modifying the wheel chair. As one who has been contracted to design motorized walkers for geriatric applications, tampering with an existing device is a risky endeavor.

Second: any movement of a wheel chair by it's occupant, will disturb the scope.

If this effort is being undertaken by an ATM or astronomy group, for the benefit of a community of physically challenged individuals, then every wheel chair in that community must be modified.

Cassegrains, Schiefspieglers and refractors all share one thing in common: the location of the eyepiece. I've already cited Porter's Springfield scope as yet another example of an OTA where the eyepiece is cantelivered out into space, far enough from the pier, to support easy access to those with physical difficulties.

Won't it be far less expensive and serve a far greater number of people, to modify an existing pier to give adjustable height than to limit access to astronomy, to those who have a specialized chair?

Art
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[refractory]

The idea I have is not having the mount a permanent part of the chair- rather it is something that can be clamped on. No muss, no fuss, adjustable to many different chairs. Only one person can view at a time anyway. And scopes are moved all the time, even jogged. In any case I'm not even thinking here in terms of large star-party type gatherings. Just intimate little get togethers, with the least expensive and elaborate facilitation for use. The OTA itself can always be removed from the chair-mount and used conventionally for the other viewers.

BTW- if the mount is ON the chair, the chair is lots less likely to knock anything over by accident.

Jess Tauber

[Chriske]

Although we're almost having a standstill because of the intense heat for the last weeks here in Belgium, we're still planning and drawing......and drinking.....
We've decided to add a tracking scope as well, so the users will be able to make some long exposure photo's through that scope.

This is how it looks like this very moment(main telescope not shown) only the hugh rotating flat and the tracking scope (a demolished refractor) are visible.
The demolished refractor has been folded to fit that 140 mm long and 315 mm diameter tube. This is the result of the necessary 'refractorsqueezing :






...maybe this will reveal the 'secret'...? ....

[Chriske]

Still at it...
As promissed some info.

Some parts :


There was no way to connect the dewshield in a simple manner to the tube so it would not be visible to the spectators. So we had to 'invent' these hughe arrows. We connect the dewshield to them with a few small screws. At the samez time all inexperienced observers can see where the arrow (and telescope) is pointing at. There is also a build-in laserpointer(no finderscope). This part contains the hughe flat 270 x 380 mm. The most tricky part was to draw the cuts to fit the dewshield with the tube...



Most upper part is a tracking scope.
Second is the holder for the big flat. It needed about 14 lbs of lead to compensate for the dewshield.
Thirth is the secundary cage.



Inside view of the trackingscope. Flats not yet installed.
Last flatholder not visible in this picture. The fourth flat is located in the very centre of the drum and is pointing toward the point of view of this picture.


I modified my(sorry..our.. ;-) kitchen so I can grind and polish 'around the clock'. These will be 4 x 400 mm flats. Only one needed for this scope. Just started #1200...

We hope to finish it before 8 sept...

[Moravianus]

A similar effort is underway in Texas

I learned about it on the Yahoo Zambuto group. Carl Zambuto is making one of the mirrors. From his post:

"McDonald Observatory is in the process of getting a new public viewing telescope called the Wheelchair Access Telescope. It is a two-mirror Pfund telescope, having two 18" f/8 fixed paraboloids, horizontal optical axes, one due north facing south and the other due south facing north.
A central 24" steering flat with a 4.25" conical hole is located at the instrument center. The flat steers sky objects into either 18" mirror, depending on which half-hemisphere is being viewed, and the focus is fixed. 2" custom binoviewers and 2" periscopic monoviewer are available to accomodate the full ADA height range. All eyepiece heights and instrument clearances are fully ADA-compliant."

[Chriske]

Someone send me that link a few days ago.
Nice project, very nice indeed. But I think our budget is a *bit* tighter...

[Mike I. Jones]

Hi Chris,
Congratulations on your system, I've been reading about it here. The more folks working to make astronomy available to the full population, fully and differently abled, the better. I designed the configuration and optics for the McDonald system, and have been having some good discussions on it over in Carl's Yahoo group. I received something interesting from Peter Abrahams with the Antique Telescope Society you might be interested in. Your wheelchair access scope looks to be a Steinheil configuration. See the following material from Peter.

Keep up the good work. Ours will be up and running in early 2007 out in REALLY dark West Texas, come look through it!
Mike

-----------------

The Dictionary of Scientific Biography has a short entry on Karl August Steinheil, 1801-1870. PhD astronomy 1825.
Private observatory near Munich. 1832 named professor of mathematics & physics at Munich U. 1849-52, worked in
telegraph communications, and in the ministry of commerce. On the request of Maximilian I, founded an optical workshop
in 1854. Later conservator of collections at Bavarian academy at Munich. 1842, invented a photometer. Improved
achromatic telescope with P.L. von Seidel. Improved silvered mirrors. Business continued by son & grandson. Biography in Allgemeine deutsche Biographie, XXXV, 720-4.
-------
And here is a translation of the German text I posted.... I'm not sure why he needed a corrector lens with a parabolic
mirror.

Excerpt from:
Steinheil, C.A. Aus einem Schreiben des Herrn Ministerialraths Steinheil an den Herausgeber. Astronomische Nachrichten 48 (1858) 145-150.

Attached please find an attempt of a German translation.
Andreas Maurer
almaur@bluewin.ch

Catoptric Meridian Circle or Transit Instrument.

The 6 inch aperture and 36 focal length main mirror’s axis is horizontally arranged from East to West, the mirror being
fixed on a stone pillar. The mirror receives light via a flat mirror which is constantly 45° inclined and which can be rotated around the parabolic mirror’s extended axis. This rotating axis and the flat mirror are perforated, hence the
picture of a point in the meridian will end in the rotating axis. It is here where the threads are positioned, they are
visible together with the point in the eyepiece. An altitude circle in the meridian and fixed on the hollow axis
measures the nadir from the mercury horizon.. The spherical deviation of the mirror’s peripheral rays is 0’’’374 which
are corrected by a small achromatic lens of large focal length and positioned in the tube 3 inches in front of the threads.

If both mirrors are arranged on a common support, f.i. as shown in fig. 1, a telescope will result. In this way the
axis A will change the azimuth whilst a rotation around b will change the altitude. If the axis A will be positioned parallel to the world axis the telescope is equatorially mounted as a rotation around A will measure the hour circle and b the declination circle. The eyepiece tube is, of course, equipped with a finder to make finding [a star] easier. However, this telescope has another, important advantage. A 6 inch instrument will cost only 300 fl and it should in its performance surpass a 6 inch refractor
since no color deviation will exist. Specially by this reason catoptric heliometers will be able to give excellent
results. I am convinced that by using silver mirrors on glass gigantic telescope dimensions can be reached but other ways of mountings will then be required. It seems to be
necessary to fix the telescope or to bring the two mirrors in a fixed position as the tube can be omitted.

[Chriske]

Hi Mike,

I did not know you were the designer of that scope...

We do not know what system ours is. Maybe there is a resemblance with another sytem but this one is our own 'design' The only item we copied is the drumscope(tracking scope, although modified). As I posted earlier this is only a scalemodel. Our goal is to make us a 18" scope, same setup. We will test this 10" to eliminate possible growingpains.

Lucky me, I have a 'crew' with the same passion always helping unconditionally...

[nytecam]

You're getting some interesting ideas Here's mine

Attached Thumbnails

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[Chriske]

Nytecam,

It looks like that is a Oldham-optical telescope type. They also use a flat to shorten long scopes, and lowering the eyeypiece to a height were no ladder or step is needed. One of the flats I'm grinding this very moment for this project will serve as secondary mirror for my 20" Folded newt.

[nytecam]

Nytecam,It looks like that is a Oldham-optical telescope type. They also use a flat to shorten long scopes, and lowering the eyeypiece to a height were no ladder or step is needed. One of the flats I'm grinding this very moment for this project will serve as secondary mirror for my 20" Folded newt.

Thanks Chris - the best example of a folded Newtonian variant is the US Naval Observatory 1.55-m Kaj Strand Astrometric Reflector Below is a scaled drawing for a folded Dobsonian with 18" f/8 and f/6 primaries - the f/6 secondary is slightly smaller at 15% gross obtruction and obviously shorter tube length at 78". A 1.8" [45mm] diam fully illuminated field is assumed in both cases. The relay optics, contained in the horizontal axis, serve to control extraneous illumination and perhaps additionally to correct spherical aberration from a simple spherical primary. I'm not expert in the latter and would appreciate feedback Obviously the engineering aspects of a turntable containing both scope and observer are not under-estimated and could be separated

Attached Thumbnails

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[Chriske]

Thierry just finished the 250 mm primary mirror.
Total effective polishing time about 4 hours...! That is starting from #1200 to the very end. Although I must admit he did not polish the very last wets to correct the bad zones. It was Thierrys' first mirror, so I decided to do the very last corrections myself.

Polishing with pads with our 'manually high pressure polishingdevice' : total polishing time 1 hours 45 min









Polished out completely

Zonal corrections with pads and rotation tool, total polishing time : 4.5 min
http://users.pandora...ierry11full.jpg http://users.pandora...ierry12full.jpg

http://users.pandora...ierry13full.jpg


Polishing with soft pitch total polishing time 2 hour 05 min
http://users.pandora...ierry14full.jpg http://users.pandora...ierry15full.jpg

http://users.pandora...ierry16full.jpg

I think we're ended better than 1/20 lambda

[Chriske]

Just finished the hugh flat. It took me nearly 8 hours to polish out completely that 400 mm flat. I made myself a very special and professional polishingtool ... The creaking sound is from the wooden polishingtabel suffering under the *enormous* weight, there is almost 50 lbs of lead on top of it.
I polished with three different tools, thinking they wood eliminate each anothers error and indeed it payed of. Three different tools, that is different shapes and different brands of polishingpads



After my first interference check (it was polished out completely) under a low pression sodium lamp the flat appeared to be perfectly flat. I had a another small flat(about 160 mm) from which I new it was not perfect, but I new what type of error it had( I would recognice it's pattern anywhere). I placed that small flat on the 400 mm flat to check and yes.... I only saw the error of the small one. At first I thought it was coincidence to see that pattern. I moved the flat to another spot on the 400 mm flat and I really was amazed to see the exact same pattern again on another part of that flat. And again I relocated it, and again..same pattern.
So this slavery payed of.

[Chriske]

Testing the height of the pier....

[nytecam]

Most impressive work especially the primary ..and with such speed;-)

[Olivier Biot]

Folks,

This telescope is one of the showcase attracions at the Hove public observatory open days this weekend. This telescope is great!

I had the opportunity to discuss this amazing project with Chris and his crew this afternoon. They have spent a considerable amount of time in it. I even sat in a wheelchair for the occasion, and observed the Sun through this scope. It is very easy to use!

I hope Chris will post some new pics and future ideas for this project soon!

Cheers

Olivier

[MMICKELS]

Chriske, can you post some more pics of the scope? How well does it work? Thanks!

[Chriske]

Rudje, Marco, Guy, Chris, Marc and last but not least Thierry

[Chriske]

The scope above is our prototype /scale model. Some growing pains has to be removed, but it works great. Ones our 'little boy' is finished we will start 'the fat one'. It'll be a 18" f/5, so same lenght because it hase to fit in one of the observingrooms here at Urania.
Many visitors during our open door looked through it, sitting in a wheelchair. The deal was, they only could observe sitting in a spare wheelchair Thierry brought along. So the visitors not only where testing the telescope itself but had to 'feel' the wheelchairusers 'everydayproblems'.
Thierry was amused to see these many 'false' wheelchairusers trying to reach the eyepiece of 'his' scope. He was content with the result...a *very* happy man. And a handy man to...

[Olivier Biot]

Hello kbon,

Welcome to CN!

Thanks for posting this movie - it helps in seeing the real thing in action

Cheers!

Olivier

[Macro]

I was just looking around and found this. Was wondering how it is being used now. Is the scope working good?

[Chriske]

It is working fine, but not installed (yet), The 10" was only a prototype. We had some growing pains to remove, once that is done and tested again we will start building an 18" . We also made a giant bearing out of smaller bearings. The one we installed was a bit to small for tha weight of that scope.

This moment busy working on other projects.

[The bear]

Chriske thank you for doing this having come from a wheel chair hopefully never to return this thread got me to thinking. i will eventually have to go back i fear this and tried to avoid thinking about it but it will happen one day. so it got me to thinking real hard about what design would work for me and for in the future. i do not want to spend the time making a scope or scopes i cannot use later on. this is a fine scope but becuase it is not portable i need one that is and will be easy to move and setup are there any ideas out there for one that is portable?
doc