Oddie II Refractor

The original 9 inch Oddie Telescope was manufactured by Thomas Grubb in around 1890 and gifted to the Commonwealth by James Oddie, a wealthy Victorian businessman and philanthropist. It was the first telescope to be installed on Mount Stromlo in 1911 and its dome was first Commonwealth Structure to be built in the Australian Capital Territory. The Oddie was initially used to test the atmospheric conditions on Mount Stromlo with view to establishing a Commonwealth Observatory there.

After many years work as a research instrument, the Oddie spent the last 30 years of it's life as a much loved outreach telescope. The mystique of a large brass refractor drew many visitors to Stromlo and doubtless kindled many a kid's interest in astronomy and science in general. Unfortunately, the Oddie refractor was destroyed along with many other telescopes at Stromlo, during the devastating 2003 bushfires although the original cast iron Grubb equatorial mount survived largely intact.

A friend from Mt Strmlo Observatory who'd seen the Victorian style telescope I'd built for myself, asked me if I'd be prepaired to create a similar OTA as a replacement for the Oddie, so that it could one day resume its outreach work. I'm not a commercial telescope builder, but since this was a special "one-off" case, I agreed to do it :) It should be emphasised that this replacement OTA is not be a museum style replica of the original Oddie which would be neither feasible nor desirable given it’s intended outreach function. It's a working modern telescope with a historic look and feel.

The arrival of the new Oddie refractor on the mountain was celebrated with a Heritage Day, complete with antique vehicles and period costumes.

Oddie refractor

Oddie refractor

Oddie refractor

Building the Oddie Refractor II

Oddie refractor Ironically the very first job in building the telescope didn't involve the telescope, it involved the fire damaged antique Grubb mount on which it would ultimately sit. I had to design the tube so that it would exactly fit the cast iron saddle and the only way to get that just right was to remove the saddle from the mount and take it back to my workshop. That way the telescope could be built around it.

Oddie refractor Removing the saddle turned out to be quite a difficult task. It required a special "infinite force tool" capable of supplying enough torque to release the lock nut from the heavily rusted and fire damaged shaft. The tool griped the lock nut by all six of its lug holes so it couldn't slip and the force was uniformly distributed. Since there's no limit to how long a bar you can attach to the tool, there's no limit to the force you can apply with this tool. But the key thing here is that it's gentle force with no impacts that could crack the cast iron. In the end, the nut saw the futility of continued resistence and unscrewed remarkably easily considering how rusted the shaft threads were.

Oddie refractor In this image of the newly completed OTA centre segment, the strange looking centre indent is necessary to accomodate that huge lock nut.

Oddie refractor Three completed sections of the OTA on the workshop floor. Notice how the tube tapers significantly towards the eyepiece end as the original Oddie telescope did

Oddie refractor The all important process of making sure the tube axis is straight using a Howie Glatter laser collimator which is a beautifully aligned and accurate tool. Initially, I tried to save the cost and ordered a cheap laser gun sight on ebay. The beam was 18° out of true. That's right 18 degrees! I sure wouldn't want to be anywhere near the guy with this on his gun. The target would be the safest place on the range :) The moral of the story, you get what you pay for!

Oddie refractor Getting closer. All five sections of the OTA completed and bolted together to form the complete telescope and the large brass steering/counterbalance ring on the back. The six pads on the end facing the camera were designed to hold a massive focusser which was custom made by starlight Instruments.

Oddie refractor This is the finder scope being constructed. The finder is an 11 x 75mm with a field of view of 7°. It's quite a nice rich field telescope in its own right yielding pin point stars right across the extreemly wide field. The reason it has to be mounted so far above the tube is that its field of view is so wide that you'd see the end of the main OTA were it any lower! In the background you can see Thomas Grubb's cast iron saddle cleaned, restored and looking much happier than it does in the photos above.

Oddie refractor Here the Oddie II can be seen in the ANU Research School of Physics and Engineering workshop where I was helped with some of the more high tech aspects of the construction such as the CNC engraving of the nameplate.

Oddie refractor

Oddie refractor

This is the beautifully CNC engraved brass nameplate for the refractor with credit and thanks to Tom and Craig (ANU Research School of Physics and Engineering workshop)

Oddie refractor

This is the custom made 3.5" long travel focuser built by starlight Instruments fitted to the now painted OTA end section. Notice the big 3" eyepiece compression collar that will hold the massive daigonal once it's completed.

Oddie refractor This is the completed dew shield section with the lens cap that will keep dust and dirt from the objective once the scope is installed in the observatory. The lens cap is backed with a foam plug that provides a friction fit into the end of the scope and is covered in silknot for luxury, but because it has low friction and abrasion on the paint. Given that the scope will ultimately be housed in an observatory a dew shield may not be 100% necessary but it serves the double purpose of being long enough to ensure that if the cap is replaced carelessley, it can't hit the glass surface of the lens.

That magnificent spun brass section at the base was manufactured in Australia by Whitehorse Industries. It defies belief that one can achieve the necessary ±0.2mm accuracy for a friction fit on the cap by spinning against an MDF formbut achieve it they did!

Oddie refractor And at last, here is a complete kit of parts for the Oddie refractor waiting for the paint to fully harden before it was assembled.

Oddie refractor

Assembling the big refractor in the common room up at Stromlo Observatory

Oddie refractor This is the ISTAR objective lens installed in the scopea very beautiful piece of glass. Our initial testing shows that this lens works extremely well yielding sharp contrasty images up to about 500x magnification. The chromatic aberration also seems well controlled for a large achromat, you just don't notice it at all at lower magnifications. One thing that one really notices with a long refractor like this is how big the depth of focus is. They really are very forgiving of focus error. We're very much looking forward to getting the Grubb mount restored so that we can point this beastie skyward!

Oddie refractor This is the completed refractor after collomation and testing ready for Stromlo's Heritage day.

Contact: timwetherell@gmail.com

Mount restoration

The original mount for the Oddie refractor is being undertaken in the workshops of the ANU Research School of Astronomy and Astrophysics, primarily by Colin Vest who's being assisted by a number of volunteers including myself. One of my jobs was to restore the clockdrive to working order from what was far from working order! It's been an interesting insight into how they used to build em :)

Oddie refractor

Oddie refractor

Two views of the clockdrive, after the fires and now

Heritage Day celebrates the arrival of the Oddie II on Mount Stromlo

Oddie refractor Exactly 100 years after the oddie refractor 1 arrived at Stromlo, here we have the oddie 2 rolling up at the Commonwealth Solar Observatory.Sure looks convincing in sepia doesn't it :)

Oddie refractor Perhaps a little more true to life in colour. Special thanks to Ron and Annette for bringing Poly (their beautiful 1926 International truck) to haul the telescope up the mountain in style.

Oddie refractor Checking that the telescope worksand it does!

Oddie refractor Enjoying the day with suitably attired friends.

Oddie refractor

Distinguished company, even Professor Einstein dropped by courtesy of Questacon.

Oddie refractor Something for everyone. We provided a step for those too small to reach the eyepiece though even that didn't work for everyone.

Oddie refractor Finally a bit of abstraction. The Oddie objective amongst some of the domes on the mountain.