Appenzellersun, Polar Coelostat arrived , now in maintenance

swisswalter · Post by **swisswalter** » Tue Jan 21, 2014 8:12 pm

Hi all

finally we came to an agreement. 12 pairs of shoes for an old famous coelostat :cheer:

that one has been built in Switzerland in the late 50's by Jakob Lienhard and has been sold to Germany in 1981. Now it's back to Switzerland again :cheer:

It needs now to be understood by me and refurbished, set up and aligned. Then we get pics (so I hope) with 8,3 m FL :woohoo:

a glimpse from the direction of the viewer

the light path

the reflecting mirror

The mirrors are in perfect shape, but have never been tested. They are uncoated at the moment. If I need more light, I can alwas coat the one or the other or both.

Has some body a manuel to this instrument , or is willing to help me to get it to run

One thing I tested so far, the clock runs wunderful

astrotrailer · Post by **astrotrailer** » Tue Jan 21, 2014 9:54 pm

Is mirror at point A a parabolic mirror of 8.3 m focal length?

Ralph

Suncityan · Post by **Suncityan** » Tue Jan 21, 2014 9:59 pm

Looks like a wonderful project Walter, please keep us posted.

swisswalter · Post by **swisswalter** » Wed Jan 22, 2014 5:35 am

Hi Ralph, Hi Tommy

thank you very much.

Yes the mirror at point B is a parabolic with 8,3 m FL :woohoo:

Post by **marktownley** » Wed Jan 22, 2014 7:05 am

Oh wow! A fine instrument there Walter. That was good value at just 12 pairs of shoes. I look forward to watching the project develop

Carbon60 · Post by **Carbon60** » Wed Jan 22, 2014 7:19 am

Nice one, Walter. Looking forward to seeing how this progresses.

A wonderful clockwork project for a Swiss guy.

Stu.

Derek Klepp · Post by **Derek Klepp** » Wed Jan 22, 2014 7:41 am

Yes we will be watching the Swiss clockwork on this one.A very interesting piece Walter. You will need a nice display case for this.
Cheers Derek

swisswalter · Post by **swisswalter** » Wed Jan 22, 2014 3:36 pm

Hi Mark, Stuart and Derek

thank you very much. I'm very eager to get it run, test and then mount. I visited today a clockmaker to get an replacement of a little broken shaft in brass. He will do it for free because of that very rare instrument. I'm so happy.

swisswalter · Post by **swisswalter** » Wed Jan 22, 2014 4:17 pm

Hi all

here I try to import a film taken of Jakob Lienhard in his obs in the 50'ies. Don't be afraid, your speakers work, but the film has no sound

the direct link

http://www.videoportal.sf.tv/video?id=9 ... ea6a28b328

SolarJohn · Post by **SolarJohn** » Wed Jan 22, 2014 5:41 pm

The video link does not bring you to an operable video!

swisswalter · Post by **swisswalter** » Wed Jan 22, 2014 5:45 pm

Hi John

sorry I'm working on it. The direct link posted works for me at our solarchat site

Stephen: Please, I need your help to embed the video

Post by **marktownley** » Wed Jan 22, 2014 9:37 pm

That's a great vid Walter! I've tried to embed it for you but can't do it...

swisswalter · Post by **swisswalter** » Thu Jan 23, 2014 5:13 am

Hi Mark

thank you very much for your effort

swisswalter · Post by **swisswalter** » Sat Feb 01, 2014 6:50 pm

First tiny step done

ordered a new part (just a one to one copy of the broken part). Should arrive in ten days.

Until then I read about grinding my own custom made mirror :woohoo:

Post by **marktownley** » Sat Feb 01, 2014 7:05 pm

Nice! Those are proper plans 8)

DavidG · Post by **DavidG** » Sun Feb 02, 2014 8:36 pm

Hi Walter,
Very nice instrument. It is a version of Gerrish mount like the one built by my good friend Jim Daley http://stellafane.org/tm/tg/daley2/daley2.html
With the primary mirror having a 8 meter focal length and what looks like a 120mm aperture, it is most likely not a parabola but a sphere since it makes no difference optically at that long a focal length. You do have to worry about astigmastism thou since the flat mirror is feeding the primary at of axis angle. If you measure that angle I can raytrace the optical path and post a spot diagram and see if the astigmastism is problem. What is the diameter of the flat mirror ? I'm sure you know that the clock drive is tracking at 1 rev in 48 hours.
One of the draw backs of this design is the open optical path. You might consider enclosing it or setting up the optics over a grassy area.

- Dave

DavidG · Post by **DavidG** » Sun Feb 02, 2014 8:44 pm

Walter,
It looks like the writing on the back of the primary mirror is "R= 8360". If this is the case that usually means the the Radius of Curvature is 8360mm and the focal length will be 1/2 of this or 4180mm.
So the primary mirror needs to be this distance away from the focuser or the image won't come to focus and the diameter of the solar image will about 38mm.

- Dave

swisswalter · Post by **swisswalter** » Sun Feb 02, 2014 9:01 pm

Hi Dave

thank you very , very much for your comments. It happened while walking with our dog this afternoon that I thought about the figur R= -8360. Then I had a doubt about the 8 m FL.

Please can you confirm that the FL can be 4,2 m ? I'm sure the second mirror is "only" a spehere.

The flat mirror has a diameter of 200 mm, the collecting mirror a diameter of 150 mm.. What do you need to make your calculations ?

I'm most exited you chimed in

DavidG · Post by **DavidG** » Sun Feb 02, 2014 11:27 pm

Walter,
The simplest method to find the focal length of the primary mirror is to use the Sun and measure the distance from the surface of mirror to the were the image comes to sharp focus. Since the mirror is both uncoated and also has a long focal length, there is no danger of catching anything on fire from the focused image of the Sun. The uncoated glass reflects only 5% of the light and the image is also very large so it is not strong enough to cause problems.
As for the angle to measure, if you look at the picture you posted with the light path drawn out, you need the angle that is formed between the optical path going up through the focuser and the light path being reflected off the flat mirror toward the 150mm primary mirror. Picture the light path as being a right triangle so you need the angle the primary is tilted so as to be aligned with the center of the flat mirror.
By the way, are you sure the primary mirror was mounted below the flat mirror ? I think the primary might have been mounted above the flat mirror.This would make the angle that the flat mirror needs to tilt to direct the light to the primary much smaller. Please see this article that gives examples of the typical optical arrangements http://articles.adsabs.harvard.edu//ful ... 9.000.html

- Dave

swisswalter · Post by **swisswalter** » Mon Feb 03, 2014 5:24 am

Hi Dave

thank you very much for your help and also for the link of the article which I have found too. As soon as the sun Permits I'm going to measure the FL of the Primary mirror. I'll try also to measure it by m easuring the grinding depht of the mirror.

As for the setup I'm sure it is that way, otherwise the sun could not enter the focusing tube.

Please stay tuned

swisswalter · Post by **swisswalter** » Mon Feb 03, 2014 7:34 pm

Hi all

we took the chance to measure the FL of the primary mirror. I have learned trough you:

R=2xf

well let's see what we end up with

the measuring team

searching for the reflections (not as easy as it may look)

close to the focal point

even closer

measuring point

the result

DavidG · Post by **DavidG** » Mon Feb 03, 2014 8:11 pm

Walter,
I'll assume that the 4.045 meters is 1/2 the distance you measured to were the reflection of the lamp was in sharp focus. You should have measured 8360mm and 1/2 of that being the focal length or 4180mm. Most likely why you did not measure the 8360mm distance is that you need to place a screen next to the light source so they are co planar and move them together until the reflection is focused sharply on the screen. When you find that position, that will be the radius of curvature and 1/2 of that being the focal length. If you use parallel light as in Sunlight, then were the image comes to focus will be the focal length.
Here is a website that shows how to easily measure the radius of curvature using a flashlight and card board screen http://www.obairlann.net/reaper/astrono ... -test.html

- Dave

swisswalter · Post by **swisswalter** » Mon Feb 03, 2014 8:48 pm

Hi Dave

thank you very much for your help and the hints, but I don't agree at the moment. If the R of the spehre is 8360 I should find f around 4160 wich I have found with ~4050. Where do I mistake

DavidG · Post by **DavidG** » Mon Feb 03, 2014 10:34 pm

Walter,
The light source ( your lamp) and the reflection off the mirror were it comes to sharp focus must be next to each other and you need to move them as unit until the reflection comes to a sharp focus. Please see the website I provide a link to.
Think of it this way, when a you look at a star the light comes to focus at the focal length of the mirror. As the object gets closer, the focus point moves more away from the mirror. When the light source is located at the exact radius of curvature, the focal point will also be at the radius of curvature and those distances will be exactly the same. If the light source is not at the radius of curvature, the light will come to focus somewhere BETWEEN the focal length and radius of curvature. So what you did was have the lamp located at some position but not at the exact radius of curvature. The mirror was farther away then 8360mm which caused the image to come to focus at 8100mm. So if you move the lamp closer the image would come to focus a little farther away. You keep doing this until both distance are the same, now your at the radius of curvarture. Also if you look at the mirror, it should totally fill with light, not just part of it or you see the lamb in it. The screen you focus the image on needs to be right next to the lamp and you move them as unit toward and away from the mirror until you find the position that the image is at sharp focus. When you do this you are forcing both the lamb and the focused image to be at the radius of curvature and 1/2 of that distance is the focal length.

- Dave

DavidG · Post by **DavidG** » Mon Feb 03, 2014 10:35 pm

Walter,
The light source ( your lamp) and the reflection off the mirror were it comes to sharp focus must be next to each other and you need to move them as unit until the reflection comes to a sharp focus. Please see the website I provide a link to.
Think of it this way, when a you look at a star the light comes to focus at the focal length of the mirror. As the object gets closer, the focus point moves more away from the mirror. When the light source is located at the exact radius of curvature, the focal point will also be at the radius of curvature and those distances will be exactly the same. If the light source is not at the radius of curvature, the light will come to focus somewhere BETWEEN the focal length and radius of curvature. So what you did was have the lamp located at some position but not at the exact radius of curvature. The mirror was farther away then 8360mm which caused the image to come to focus at 8100mm. So if you move the lamp closer the image would come to focus a little farther away. You keep doing this until both distance are the same, now your at the radius of curvarture. Also if you look at the mirror, it should totally fill with light, not just part of it or you see the lamb in it. The screen you focus the image on needs to be right next to the lamp and you move them as unit toward and away from the mirror until you find the position that the image is at sharp focus. When you do this you are forcing both the lamp and the focused image to be at the radius of curvature and 1/2 of that distance is the focal length.

- Dave

sullij1 · Post by **sullij1** » Tue Feb 04, 2014 2:46 am

Very cool stuff boys! I will be lurking watching the action.

Post by **Merlin66** » Tue Feb 04, 2014 3:27 am

Walter,
What Dave is saying is position the torch immediately behind a hole in a large(ish) piece of card and locate that at 8300mm (near enough to start with.....)in front of the mirror.
When the lamp is pointed at the mirror the reflection should be seen on the card close by the lamp aperture.....slowly move the lamp/card until you get the best focus (of the lamp) on the card.
That will measure the radius of curvature, the focal length is half this....
Make any sense??

swisswalter · Post by **swisswalter** » Tue Feb 04, 2014 5:27 am

Hi Dave, Hi Ken

thank you very much for your comment and help. We do not disagree. The test I used gives indeed the same result as your procedure described ( see also www.stathis-firstlight.de ). That procedure I used is a very common first test of a mirror while grinding it. I had the primary filter filled with light but was not able to take a pic of that situation because it reacts immediately of any little missalignment. Using the laser to measure the distance was just an additional check, and it works.

Next to that I meausred the curvature of the mirror, it is below 0,4 mm and above 0,3 mm, which gives the same result ~4,2 m focal length t= (D/2)2/2xR)

swisswalter · Post by **swisswalter** » Thu Feb 13, 2014 6:50 am

Hi mod gang

we are back again. I have received the broken part and I'm going to assemble the ceolostat the next weeks. Stay tuned.

Post by **marktownley** » Thu Feb 13, 2014 6:54 am

Hi Walter!

Keep us all updated.

swisswalter · Post by **swisswalter** » Thu Feb 13, 2014 4:28 pm

Hi Mark

I'm so happy that you have managed to get into the forum again too. I would have been feeling lost without you buddy. Did you notice that you have lost posting points as well as me. I'm a very new member to that forum, just joined it ;-) but I have already some hundreds post's ;-)

Hope you all over there stay dry (not meaning wine, beer etc. ;-) ) and safe

alex · Post by **alex** » Thu Feb 13, 2014 4:34 pm

Very impressive Walter!

Please keep us posted

swisswalter · Post by **swisswalter** » Thu Feb 13, 2014 5:10 pm

Hi Alex

thank you very much. I will :-)

swisswalter · Post by **swisswalter** » Sun Feb 16, 2014 1:32 pm

Finally after 14 days without sunshine I took the chance to measure the FL in bright sunshine

The FL is 4180 mm. The diameter of the disk hitting the camera is ~45 mm

swisswalter · Post by **swisswalter** » Sun Feb 16, 2014 1:38 pm

temporary setup on the garden table

: temporaryonthegardentable.jpg (698.91 KiB) Viewed 4314 times

the swiss clock drive

: swissclockdrive.jpg (976.38 KiB) Viewed 4312 times

Here you see also what has to be done regarding cleaning

The 12 o'clock position of the primary mirror

: 12oclockposition.jpg (841.3 KiB) Viewed 4310 times

a riddle to be still solved (swiss hieroglyphs) Maybe somebody has a hint

: theriddle.jpg (901.76 KiB) Viewed 4309 times

the secondary temporarely positioned in the garden

: temporaryposionsecondary.jpg (795.63 KiB) Viewed 4309 times

finding a place higher up the facade

: findingaplace.jpg (1016.53 KiB) Viewed 4309 times

swisswalter · Post by **swisswalter** » Sun Feb 16, 2014 1:56 pm

and now back inside

the workroom setup for cleaning

: workroomsetup.jpg (783.21 KiB) Viewed 4309 times

the first cleaned pieces, there are many many more to be cleaned

: firstcleanedparts.jpg (824.29 KiB) Viewed 4309 times

DavidG · Post by **DavidG** » Mon Feb 17, 2014 2:24 am

Hi Walter,
I think what the symbols mean is that if the Sun is drifting downward then you want to move the slow motion control in the direction the arrow is pointing to recenter the image.

- Dave

Peter Williams · Post by **Peter Williams** » Mon Feb 17, 2014 4:38 am

This apparatus makes me think of:
"Alles Touristen Und Non-technishen Lookens Peepers!
Das Machine control is Nicht Fur Gerfingenpoken Und Mittengrabben.
Oderwise is Easy Schnappen Der Springenwerk, Blowenfuse, Und Poppencorken Mit Spitzensparken.
Der Machine is Diggen by Experten Only. Is Nicht Fur Gerverken by Das Dummkopfen.
Das Rubberneken Sightseenen Keepen Das Cottonpicken Hands in Das Pockets, So Relaxen Und Watchen Das Blinkenlights."

Interesting story of it's resurrection.

swisswalter · Post by **swisswalter** » Mon Feb 17, 2014 5:27 am

Peter Williams wrote:This apparatus makes me think of:
"Alles Touristen Und Non-technishen Lookens Peepers!
Das Machine control is Nicht Fur Gerfingenpoken Und Mittengrabben.
Oderwise is Easy Schnappen Der Springenwerk, Blowenfuse, Und Poppencorken Mit Spitzensparken.
Der Machine is Diggen by Experten Only. Is Nicht Fur Gerverken by Das Dummkopfen.
Das Rubberneken Sightseenen Keepen Das Cottonpicken Hands in Das Pockets, So Relaxen Und Watchen Das Blinkenlights."

Interesting story of it's resurrection.

Hi Peter

swisswalter · Post by **swisswalter** » Mon Feb 17, 2014 5:29 am

DavidG wrote:Hi Walter,
I think what the symbols mean is that if the Sun is drifting downward then you want to move the slow motion control in the direction the arrow is pointing to recenter the image.

- Dave

Hi Dave

very much. That is a good hint. We will see once installed

DavidG · Post by **DavidG** » Mon Feb 17, 2014 5:19 pm

Hi Walter,
I'm interested in the clock drive. The two brass gears attached to the clock look to give a ratio of 1:1 so that means the clock motor itself needs to turning at 1 revolution in 48 hours to track the Sun. Have you measured it's speed ?

- Dave

Spectral Joe · Post by **Spectral Joe** » Mon Feb 17, 2014 9:45 pm

Dave

It will be 1 revolution in 24 hours, because this is a heliostat, not a coelostat. A coelostat has the tracking mirror fixed in declination with it's surface coincident to the polar axis. To get the beam on the second flat the first flat's mount must be translated north-south as the Sun's declination changes. East-west translation is needed if the second flat shadows the first. A coelostat mirror rotates once in 48 hours and a polar heliostat once in 24 hours. There are a variety of other heliostat configurations, even altazimuth. A heliostat with anything other than the polar configuration will require two axis slow motions at rates depending on the geometry. If Walter's wonderful gadget is polar aligned it will track the Sun if it's turning once per day. Coelostats are more trouble to set up, but there is no image rotation as with a heliostat, which makes a difference in some cases.

: GEDC1070 (Medium).JPG (355.39 KiB) Viewed 4262 times

This is a photo of a coelostat, the tracks for translating the first mirror's mount are seen, the second flat has motor drives for tracking. Takes about a minute to acquire the Sun on average.

Joe

DavidG · Post by **DavidG** » Tue Feb 18, 2014 12:58 am

Hi Joe,
Thanks for jogging my memory about the Helio vs Ceolostat. I should have remembered the difference since I 'm restoring an original Hale spectrohelioscope that uses a Ceolostat.

- Dave

swisswalter · Post by **swisswalter** » Tue Feb 18, 2014 5:21 am

Hi Dave, Hi Joe

thank you very much for all your valuable Information.

@Dave yes it seems to be a 1:1 Ratio. I have not yet measured the Speed. I need to get it going, set up and have sunshine for some hours. Wow what a wonderful old piece you are restoring. Good luck.

@Joe thanks for sorting out heliostat versus coelostat. So then my gear is a polar Heliostat, right ? I'll bring it back, it was sold to me as a ceolostat

It is indeed aligned North/south, focuser beeing up north

Carbon60 · Post by **Carbon60** » Tue Feb 18, 2014 7:11 am

All fascinating stuff, guys. Very interesting.

Good luck with the restorations.

Stu.

swisswalter · Post by **swisswalter** » Wed Feb 19, 2014 5:41 am

Hi Stuart

thank you very much for the good wishes

Post by **marktownley** » Sun Feb 23, 2014 2:00 pm

Lovely to read how this has been developing Walter! Glad to see you making progress.

swisswalter · Post by **swisswalter** » Sun Feb 23, 2014 2:28 pm

Hi Mark

welcome back. Hope you had a great time and the pocket full of pics. We missed you