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Refurbishing the HST Calver Telescope



When we moved the massive HST  to Chipping from Thame the dismantled mount was heaved in its component parts into the re-erected Fry observatory, the optical tube which weighs in at around 250lbs without the cell and mirror(they take it to over 300lbs) was left in my van for immediate delivery to a local sand & shot blasters yard.


They had it for a couple of weeks and charged £150 to remove all of the layers of paint back to bare metal. The sand blasting revealed that the 2 adjustable counter weights which I had assumed were iron were actually brass as were the hinges and latch to the mirror inspection door. Had I known this beforehand I wouldn’t have avoided the sand blasting on these softer metal areas and stripped by hand which would have allowed for polishing of the brass area to enhance the look of the instrument. The sand blasting has left the brass very matt and rough to the touch, polishing to a smooth and bright surface will now be very difficult!


Apart from the removal of the paint layers the stripping also revealed the amazing workmanship that the Victorian engineers had employed in forming the tube. The joining edges the sheet had been ‘dovetailed’ for a stitched join when the tube was rolled this was then flushed off with braze giving a really amazing join which can just be seen in the image below and more clearly in the smaller detailed picture.

Dick and the sandblasted tube prior to painting

Detail on the mirror inspection hatch

Close up of tube stitched joint

From the sand blasters I took the tube directly to my friend and master paint sprayer Dick Griffin, Dick has spent his life applying paint to numerous different types of surfaces & objects and now specialises in painting coaches and helicopters.


Dick painted the tube that day and I collected it late evening, it was a 2 man lift as a minimum. The cell cover and rotating secondary cage were also sprayed at the same time.


I had hand stripped the outside of the cell with a heat gun, this enabled layers of the original green paint to be identified, this along with a discussion with the North Norfolk Astronomy Society who also have a 12.5” Calver up on the Norfolk coast at Wiverton who  gave a very accurate indication of the original colour for matching purposes. Dick then had a batch of paint mixed up to match. I am delighted with the finish.

Partially stripped cell showing original Calver paint      

Mirror cell after hand stripping

Freshly painted tube and secondary mirror cage


Emergency roof repairs

With Winter fast approaching the heavily  patched nature of larger of the 2 sections of the Fry observatory roof that resulted from numerous holes sustained  when removing it from Dr Paterson’s Thame garden in June 2010 coupled with the aging original felt and wind damage meant that some re-felting was required.

The day before Halloween the stalwarts of the ‘HST support group’ Mike Atkins, Simon Kidd and Tom Moss Davies once again pitched in to help out. After stripping off the old felt, standard heavy duty cap sheet felt was used to lie over the timber frame which is covered with chicken netting which quite ingeniously supports the felt and is much lighter than plywood sheeting.

Cold Bitumen glue, messy stuff, was used as much as possible to fix the felt down, clout nails only used along the edges etc. The holes caused by using nails weaken the felt and lead to water getting in after a number of years.

Mike warns Tom (holding the can of tar) to be careful as the felt tears easily!

Unfortunately Tom didn’t listen! So new roof, new patch.

Of course as is traditional on such occasions the job was concluded with beer at the Countryman Inn across the road


A surprise gets things going again


The work on refurbishing the HST had pretty much come to a standstill after the initial flurry of activity following the move from Thame, the re-erection of the Fry observatory and the stripping and painting of the tube. This fact weighed heavily on my mind and was frequently brought to the fore by my youngest Son, Aubrey’s great interest in this historical telescope and for want of a better word his ‘nagging’ to get it useable again.

The HST is a beast of a telescope trying to do any major reassembly work alone is practically impossible due to the weight of individual components. I didn’t want to ask friends after all the help I had already received to keep coming back to give up more of their precious time. Both Aubrey and my wife Tracey new the lack of progress was playing on my mind and unbeknown to me had arranged a group of close astronomer friends to spend a day working on the HST as part of my extended 50th birthday celebrations. This resulted in Mike Atkins, Simon Kidd, Tom Moss Davies and Es Reid turning up on my door step at 9am on April 9th 2011, just as I was about to leave to go to a gardening job! All involved in the ‘conspiracy’ appeared delighted in my surprise and luckily the day was a warm and gloriously sunny one, not to mention most productive.

The team which also included Aubrey and me got the massive pier roughly aligned and the concrete broken out where the securing fitting were to be concreted in place.

Mike cuts out a section of the concrete floor

Cast iron pivot anchor point in place prior to concreting

A very rapid setting concrete mixture was used to achieve the anchorage and by noon we were able to get final and precise alignment for the mount from the shadow cast by the noon day sun thanks to the brains of Es & Simon and exact timing via Stellarium astronomical software. Having ascertained this alignment position the concrete on the north of the mount could be broken out to allow the concreting into position of the precise polar alignment adjustment mechanism.

The mount was then moved into its final position using steel rods as rollers and large steel crow bars to force it to move by leverage. With the pier bolted down to the floor and levelled precisely we started to assemble the mount. Bearing surfaces we gently cleaned and re-greased as each component was heaved into place. Everybody commented on the quality of design and engineering from the master Victorian telescope maker George Calver. As the afternoon drew into evening things progressed to the point where we were able to fix the tube once again, OK first time we put it on upside down which caused some cursing when we realised as it is a heavy 4 man lift to do so. Generally however the engineering of the mount is such that things only go together in one position and many of the components are marked or numbered, some of the markings require layers of paint to be scraped away to reveal them however.

As some of the team reassembled the scope other gently cleared up the concrete floor and hovered up the never ending dust, not good for telescopes. To stop this dust the floor was painted with several coats of concrete sealer applied with a paint roller. This binds the surface of the concrete to prevent dust formation; it also provided a more stable surface for the concrete floor paint that was to come later.

Tom shows his passion for domestic chores

Dale starts getting the first coat of sealer down

Simon (at the back), in heavy disguise makes a rare appearance in front of the camera whilst assisting Es during  the mount assembly.

Back together and it feels so good (the telescope that is)


The team from left to right Mike Atkins, Es Reid, Dale Holt, Tom Moss Davies at the mount, Aubrey Holt, behind the camera as usual, Simon Kidd and still in the kitchen cooking and tea making for the crew Tracey Holt)

So that was about it for this long and productive day once again the HST looked like a telescope and the beer in the Countryman Inn across the road was well deserved by all.

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