Good Event #1 - A Unique Opportunity at Perkins Observatory
I was on my way to eat lunch with some friends after the Columbus Hamfest. I always turn the radio on when I get in the truck, I don't go anywhere without it on. One of the guys was on there with another friend of mine, Jason N8XE, who was not at the hamfest. I waited a round and then tossed my call sign out there. The other guy had arrived at the restaurant and was getting off the air so that left Jason and I.
It turns out Jason was on his way over to Perkins Observatory in Deleware. He is a member of the Columbus Astronomical Society and was going up there to work on some telescopes and invited me along.
I have wanted to get up there for a while now. Jason has invited me to their star parties before but I have never been able to make it out. I have also never been to Perkins Observatory in general, either, so it was a two-for-one deal. Since I didn't have anything to do the rest of the day I figured this was too good of an opportunity to pass up!
So I met up with Jason just north of Columbus and followed him over to Perkins.
The purpose of Jason's visit there was to work on a mirror he is making for a 6 inch telescope. The process is pretty straight forward - you take a thick disk of glass, grind a concave in to it, and then perfect the curvature of the concave and conform it to very tight specifications manually. It is a very precise, time consuming art requiring some very interesting processes.
This is the mirror glass and a "tool" used for shaping/polishing.
You may be asking yourself "why is the mirror clear? Aren't mirrors opaque and highly reflective?" Yes. I will get to that.
We actually didn't end up using this tool. Jason made a new one. The symmetry of the tool doesn't matter too much.
The black stuff you see there is called Pitch and is a liquid - an extremely viscous liquid. The tool is made by using a stone or plaster disk and pouring a 1/4"-3/8" or so layer of hot pitch over it (with a dam around the disk to let the pitch build up). Then the channels are cut with a blade or knife.
The reason pitch is used for this tool is because it has the ability to conform to the shape of the mirror. By warming it up the conforming process takes less time. It is done by setting the tool on the mirror and placing weights on top so the pitch can flow (ever so slowly) and match the curvature of the mirror. The channels allow for the pitch flowing and also provide a space for the abrasive fluid to flow, which is used to do the real figuring and polishing work.
The new tool we made had a more clear yellowish color to it, but the process of making it and use of it is identical.
The process of figuring and polishing the mirror is by making a cerium oxide fluid and dripping it on to the mirror. The tool is then pressed on to the mirror to make sure the shape is perfectly conformed to the mirror. This takes a bit of time - about 15 minutes. Then the tool is rubbed back and forth across the surface of the mirror and then rotated and rubbed back and forth across at a slightly different angle. By walking all the way around the mirror the tool covers the whole mirror - more in the center and less on the edges (which helps to shape the mirror). This is also why the tool doesn't have to be perfectly symmetric - the tool is moved around the entire mirror anyway so it isn't that important.
I was put to work polishing the mirror a few times so I had my hands full and wasn't able to snag any good pictures of that process.
Here is where technology comes in to play on the process. The shape of the mirror is crucial. It is an incredibly tedious process requiring, in some cases, over 100 hours of work. To ensure that the mirror is being shaped properly a Foucault test can be done using a light source and camera placed at the Radius of Curvature. Here is a picture of what the testing looks like:
The image on the screen to the left is the reflection of the mirror. If you look close at the edges the lines hook inward. The object of the figuring and polishing of the mirror is to essentially get the reflection as flawless as possible.
By identifying "zones" (the holes cut in the template) of the mirror you can focus the work in certain areas. The box holding the camera here is on a precision XY table. Note the indicator dial - that is used to record measurements in .001" increments (which is a VERY large increment in the grand scheme of telescopes - measurements in Microns become quite significant).
Note the image below of the reflection.
By adjusting the XY coordinates of the camera stand to focus the device the zones will appear as dark or light. The dimensional difference between the zones (recorded with the indicator dial) are entered in to a computer program to calculate and graph other parameters.
We didn't get too far on the mirror work this trip. The new tool for the mirror was made and the parameters of the mirror were entered in to the computer to see where it stands. Outside of that, very little polishing/figuring was done - only a few rounds. As I said before, the process is very time consuming. At the present time Jason estimates having about 80 hours of work in this particular mirror. The good part - you really can't screw up a mirror! Unless the mirror is broken it can be worked on and fixed - it is just a matter of how much effort you put in to it. The more effort and care to get it "just right" the better the picture!
After the mirror is figured and polished to the right specifications it goes through a vacuum chamber to be condensation plated with aluminum oxide. This is what makes the mirror a "mirror", the glass is just the form that holds the aluminum oxide. Also, unlike the mirror in your bathroom, these have the aluminum coating on the front surface of the mirror. The reason for this is that the glass in front of your bathroom mirror gives a double-image, a single surface is a true reflection.
Aside from the mirror work, I was able to get around and document a few other neat attractions.
Being as much of a radio nut as I am (and, I'll admit - the ultimate geek in that I joined SETI a few years back) I found this pretty exciting. Perkins Observatory is home to the original receiver and recording gear used on The Big Ear, which most notably decoded the historical WOW! signal (see third photo below).
Apparently, there is a current project at Perkins Observatory to put a radio telescope on the air at the hydrogen line (around 1420mHz). Note this is the same frequency range the WOW! signal was recorded on. There are three dishes on the property already wired for use. The transverter, receiver, and other components are yet to be on-line. The setup, as far as I know, will not be using any of the original Big Ear gear.
OK, so one can not go to Perkins Observatory without knowing about "the big telescope." After all, that is what sits under the big dome, right?
This actually isn't the original telescope. The observatory was built in the 20's and the original telescope was replaced in the 60's with this one here. The old telescope somehow used this large concrete structure as a base/mount.
The rest of the workings of the observatory are also pretty interesting. I will let most of these last few pictures do the talking.
These next few pictures are of the drive and tension systems for the dome.
Jason wasn't exactly sure what this was used for.
This is the original telescope mirror glass. This is one HEAVY chunk! Also, the glass is not perfect - it has lots of bubbles in it if you look close. However, the consistency of the glass is not important - only the surface. This could very well be polished up, plated, and put back in service.
So that sums up most of my day! I was out for an extra 5+ hours that I didn't expect, however I really learned a lot and got a very unique experience. I have had an interest in astronomy for many years, I have a couple of telescopes myself, however I have never been too serious about it. Going to Perkins Observatory and having the exposure I did really made an impression on me. I doubt I will start up making my own telescopes any time soon, but the experience of seeing how it is done and taking part in the process was very cool!
It turns out Jason was on his way over to Perkins Observatory in Deleware. He is a member of the Columbus Astronomical Society and was going up there to work on some telescopes and invited me along.
I have wanted to get up there for a while now. Jason has invited me to their star parties before but I have never been able to make it out. I have also never been to Perkins Observatory in general, either, so it was a two-for-one deal. Since I didn't have anything to do the rest of the day I figured this was too good of an opportunity to pass up!
So I met up with Jason just north of Columbus and followed him over to Perkins.
The purpose of Jason's visit there was to work on a mirror he is making for a 6 inch telescope. The process is pretty straight forward - you take a thick disk of glass, grind a concave in to it, and then perfect the curvature of the concave and conform it to very tight specifications manually. It is a very precise, time consuming art requiring some very interesting processes.
This is the mirror glass and a "tool" used for shaping/polishing.
You may be asking yourself "why is the mirror clear? Aren't mirrors opaque and highly reflective?" Yes. I will get to that.
We actually didn't end up using this tool. Jason made a new one. The symmetry of the tool doesn't matter too much.
The black stuff you see there is called Pitch and is a liquid - an extremely viscous liquid. The tool is made by using a stone or plaster disk and pouring a 1/4"-3/8" or so layer of hot pitch over it (with a dam around the disk to let the pitch build up). Then the channels are cut with a blade or knife.
The reason pitch is used for this tool is because it has the ability to conform to the shape of the mirror. By warming it up the conforming process takes less time. It is done by setting the tool on the mirror and placing weights on top so the pitch can flow (ever so slowly) and match the curvature of the mirror. The channels allow for the pitch flowing and also provide a space for the abrasive fluid to flow, which is used to do the real figuring and polishing work.
The new tool we made had a more clear yellowish color to it, but the process of making it and use of it is identical.
The process of figuring and polishing the mirror is by making a cerium oxide fluid and dripping it on to the mirror. The tool is then pressed on to the mirror to make sure the shape is perfectly conformed to the mirror. This takes a bit of time - about 15 minutes. Then the tool is rubbed back and forth across the surface of the mirror and then rotated and rubbed back and forth across at a slightly different angle. By walking all the way around the mirror the tool covers the whole mirror - more in the center and less on the edges (which helps to shape the mirror). This is also why the tool doesn't have to be perfectly symmetric - the tool is moved around the entire mirror anyway so it isn't that important.
I was put to work polishing the mirror a few times so I had my hands full and wasn't able to snag any good pictures of that process.
Here is where technology comes in to play on the process. The shape of the mirror is crucial. It is an incredibly tedious process requiring, in some cases, over 100 hours of work. To ensure that the mirror is being shaped properly a Foucault test can be done using a light source and camera placed at the Radius of Curvature. Here is a picture of what the testing looks like:
The image on the screen to the left is the reflection of the mirror. If you look close at the edges the lines hook inward. The object of the figuring and polishing of the mirror is to essentially get the reflection as flawless as possible.
By identifying "zones" (the holes cut in the template) of the mirror you can focus the work in certain areas. The box holding the camera here is on a precision XY table. Note the indicator dial - that is used to record measurements in .001" increments (which is a VERY large increment in the grand scheme of telescopes - measurements in Microns become quite significant).
Note the image below of the reflection.
By adjusting the XY coordinates of the camera stand to focus the device the zones will appear as dark or light. The dimensional difference between the zones (recorded with the indicator dial) are entered in to a computer program to calculate and graph other parameters.
We didn't get too far on the mirror work this trip. The new tool for the mirror was made and the parameters of the mirror were entered in to the computer to see where it stands. Outside of that, very little polishing/figuring was done - only a few rounds. As I said before, the process is very time consuming. At the present time Jason estimates having about 80 hours of work in this particular mirror. The good part - you really can't screw up a mirror! Unless the mirror is broken it can be worked on and fixed - it is just a matter of how much effort you put in to it. The more effort and care to get it "just right" the better the picture!
After the mirror is figured and polished to the right specifications it goes through a vacuum chamber to be condensation plated with aluminum oxide. This is what makes the mirror a "mirror", the glass is just the form that holds the aluminum oxide. Also, unlike the mirror in your bathroom, these have the aluminum coating on the front surface of the mirror. The reason for this is that the glass in front of your bathroom mirror gives a double-image, a single surface is a true reflection.
Aside from the mirror work, I was able to get around and document a few other neat attractions.
Being as much of a radio nut as I am (and, I'll admit - the ultimate geek in that I joined SETI a few years back) I found this pretty exciting. Perkins Observatory is home to the original receiver and recording gear used on The Big Ear, which most notably decoded the historical WOW! signal (see third photo below).
Apparently, there is a current project at Perkins Observatory to put a radio telescope on the air at the hydrogen line (around 1420mHz). Note this is the same frequency range the WOW! signal was recorded on. There are three dishes on the property already wired for use. The transverter, receiver, and other components are yet to be on-line. The setup, as far as I know, will not be using any of the original Big Ear gear.
OK, so one can not go to Perkins Observatory without knowing about "the big telescope." After all, that is what sits under the big dome, right?
This actually isn't the original telescope. The observatory was built in the 20's and the original telescope was replaced in the 60's with this one here. The old telescope somehow used this large concrete structure as a base/mount.
The rest of the workings of the observatory are also pretty interesting. I will let most of these last few pictures do the talking.
These next few pictures are of the drive and tension systems for the dome.
Jason wasn't exactly sure what this was used for.
This is the original telescope mirror glass. This is one HEAVY chunk! Also, the glass is not perfect - it has lots of bubbles in it if you look close. However, the consistency of the glass is not important - only the surface. This could very well be polished up, plated, and put back in service.
So that sums up most of my day! I was out for an extra 5+ hours that I didn't expect, however I really learned a lot and got a very unique experience. I have had an interest in astronomy for many years, I have a couple of telescopes myself, however I have never been too serious about it. Going to Perkins Observatory and having the exposure I did really made an impression on me. I doubt I will start up making my own telescopes any time soon, but the experience of seeing how it is done and taking part in the process was very cool!
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