Hodgepodge: The Mishmash Mount

I have previously published a description of Hodgepodge, the mish-mash mount I used for the solar eclipse. While I wrote about the mount, and posted some photos, I did not really cover the construction. Now for some details…

Hodgepodge and the Eclipse
Hodgepodge set up at Grant’s Spring to photograph a total solar eclipse

A few months back I rebuilt the drive unit of an old Celestron mount, installing a drive corrector into the base unit in the process. I have used this sidereal drive for time lapse, but it can also be used to mount a telescope again. Better yet, with a few minutes reconfiguration, it can do either.

With the solar eclipse looming on the calendar I realized I needed a tracking mount to allow photography. Tracking would allow me to keep the Sun and Moon in the field without wasting precious seconds framing the image during the eclipse. It would also enable longer exposures without motion blurring the image.

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In the end it is a Celestron C8 telescope drive and forks containing custom electronics, a Meade heavy duty wedge from an LX-90, a hand-made tripod, holding a Televue 76mm APO telescope, using a Vixen style dovetail base, with a Baader film solar filter.

It is tempting to call it Frankenscope after the similarities with the classic monster.

Hodgepodge setup on the side of Mauna Kea with the TV-76mm and Telrad on the plate

To further add the the Mary Shelley plot similarities, much of this was revived from the junk pile. I very nearly decided to toss the drive and fork, they were that bad, peeling paint and rusty bolts. A great deal of work was necessary to re-animate these components.

The wedge came from a telescope that was killed in an unfortunate incident with an aquarium heater. The heater was used to de-humidify the OTA and prevent fungus on the optics. Note: Aquarium heaters are not made to operate out of water.

The Hodgepodge mount assembled for the first time

Several new aluminum parts were machined from scraps, some of which were scavenged when the observatory shop was being cleaned out and a lot of metal stock was tossed.

Many of the electronic components used to build the drive corrector were also scavenged parts from dead electronics, this includes the 1.8432MHz crystal that forms it’s beating heart. This heartbeat keeps the mount turning at exactly sidereal rate.

Yeah, you could call it Frankenscope.

But I will call it Hodgepodge.

A Celestron FirstScope

I tend to end up with telescopes, they just appear on a semi-regular basis, given to me with the instructions to find a home for them. One of the latest additions to Andrew’s Home for Wayward Telescopes (AHWT) was a Celestron FirstScope. It was bequeathed to me by a co-worker moving to the mainland and thus dwelt for a time in my office, there being little room in my garage for yet another telescope.

Celestron FirstScope
A Celestron FirstScope in somewhat larger company
This telescope is now headed to a new home. With Christmas approaching another co-worker asked my opinion in buying a telescope for his eight year old daughter. She had expressed interest and he was wondering what to get. Quick to size an opportunity to divest myself of an unused telescope I let him know I had just the thing! One less mirror to clean. Rob of course was quick to seize on the idea of free.

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Refurbishing a TeleVue Renaissance Mount

I have already posted about the restoration of an orange tube C8. That was only part of the story, the telescope is paired with a TeleVue Renaissance mount that was in the same poor condition as the optical tube. The mount required the same treatment, a complete tear down and restoration to reverse the ravages that tropical humidity had wrought upon the metal parts.

RA and Declination Axis
The RA and declination axis removed from the mount for further disassembly and restoration

Corrosion was the issue. While the mount was mostly functional, it was looking horrible. The aluminum under the paint was corroding into a fine white powder. Most of the screws were quite rusted along with the counterweight shaft where the chrome was flaking away and the rust spreading. If allowed to continue the mount would soon be the piece of junk it looked like. There was something wrong with the clutches as well, they do not lock firmly and needed to be inspected.

The mount was sold by TeleVue in the 1980’s paired with their APO refractors. The mount is actually a re-labled unit manufactured by the Japanese firm Carton Optics as the model Super Nova or RSM2000. Well regarded by amateur astronomers you can find postings of well used and beloved mounts still in use thirty years later. Examining the mount I find I agree with those who like it. There is much to love in the solid smooth motion, this looks to be worth the effort of restoration.

Thus I set about the task of stripping down the mount into component pieces… Of the rusted hardware only one screw required drilling out, the hex drive head stripping when I tried to remove it. Fortunately I again had the proper tools, a set of easy outs to remove the remains of the screw after I had drilled the head off. I was able to remove the screw without any damage to the aluminum castings.

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Restoring an Orange Tube Celestron C8

It looked horrible! The paint was coming off everywhere with heavily corroded aluminum underneath. Most of the screw heads were small balls of rust, with hopefully enough remaining to fit a screwdriver to and remove. For a precision optical instrument this small telescope was not very encouraging.

Orange Tube Corrosion
Looking at what remains of the paint on an old Celestron C8 orange tube telescope
On the bright side the optics looked to be in decent shape. While there was some dirt and mold on the corrector, the primary looked almost perfect. Not bad considering the condition of the metal parts. Maybe, just maybe, this telescope is salvageable.

The telescope in question is an old orange tube Celestron C8. Thousands of these little telescopes were manufactured in the 70’s and 80’s. It was the C8 that set the standard for amateur telescopes at the time. The C8 is still in production forty years later, but the tubes are no longer painted orange as they were originally. Compact, yet offering decent performance, these telescopes were well regarded and hold a special place in the memories of many amateur astronomers. I have seen these little orange telescopes at dozens of star parties, even bolted to the side of huge professional telescopes for use as finders.

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Replacing the Celestron NextStar GPS Battery

When your Celestron GPS telescope will not get GPS fix for a long time, or the GPS will not work at all, it is time to replace the battery on the GPS receiver board. Another symtom is when the telescope may get a fix, but it is incorrect, the time or location no where close.

Celestron Telescope GPS Module
The Celestron GPS telescope GPS module with the original battery
Instructions for replacing the battery are posted elsewhere about the web. There are excellent instructions for battery replacement on the NexStar Resource Site. It was those instructions I was following when I was recently replacing the battery in our ‘scope.

The GPS board is found in the main section on the oldest telescopes, but located in the arm in later ‘scopes. Our is located in the arm, a small circuit card just under the inside plastic panel connected to an antenna by a cable. Simply remove the four screws holding the plastic panel and you have access. The antenna cable can be disconnected with some gentle tugging, two screws for the board, one more connector and the board comes out. The battery is found hidden on the underside of the PCB.

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The Celestron Cometron

I have only had three telescopes given to me this year. Telescopes in various states of disrepair. I usually fix them up, clean them up, and find a new home for them.

It was Julia who gave me this little bit of fun… A Celestron 62mm f/4.8 Cometron. A small refractor intended for low power viewing. Prefect for viewing comets or other wide field objects.

Celestron Cometron
A Celestron Cometron 62mm f/4.8 telescope.
These little refracting telescopes were sold in the 1980’s to capitalize on the comet Halley mania. Sold bearing the Celestron name, they were actually built by Vixen. They continued in production for many years as they proved relatively popular. The Cometron name has been used for a number of small telescopes over the years, but, as far as I know, this is the original.

The ‘scope I was given was in pretty good shape. Nothing broken or badly damaged. The optics dirty but free of coating damage or uncleanable grime. All that was require was disassembly and a good cleaning to remove dirt, spider webs, and a few cockroach egg cases.

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