Astro Optical? What have I got here?

[Malcolm]

This gear has been donated to my astro group, apparently 25 years old and only used once.

Image gallery: https://imgur.com/a/CorVD

1. Control box with socket at rear.
2. Drive assy, where does this fit? Working.
3. Drive assy, view 2.
4. Speed controller. Blue buttons?
5. Unknown?
6. Lock ring and a handle.
7. Primary mirror, needs replacing.
8. OTA cradle, missing rings or straps of some sort.
9. Mount.
10. Mount. Handle fits here?
11. Mount.
12. Mount. Set Latitude?
13. Mount. ?
14. Mount. ?

Missing counterweight, tube holders and possibly more.
Secondary not yet checked, likely damaged. OTA undamaged.
1.25 focuser has small damage, can be fixed.

[Merlin66]

Malcolm,
Looks like an interesting project.
I'd say it used a frequency controller (240V, 50 Hz +/- 20%) for the RA motor (seen behind the worm gear in the drive image)
The unknown part seems to be the RA Setting circle from the polar axis.

[doppler]

It's a Samson mount, if you search the iceinspace archives there have been a few mentioned there. There was a engineer in Qld (I think) that manufactured them for AOS aka astro optical supplies. There was a web page somewhere about the mount and the engineer.

http://www.turbofast.com.au/astrotel/index.html

http://www.iceinspace.com.au/forum/showthread.php?t=163906&highlight=aos

[Wavytone]

Hi Malcolm, it’s from Astro-Optical, and it’s a later version of their “Samson” or “Goliath” mount.

It had bush bearings for each axis, the RA circle is the white disk with numbers like a big protractor - slides onto the end of the polar axis, which should have a worm wheel and worm drive driven by a 240VAC synchronous motor for tracking.

The mount say on a pier which it appears you have, with three metal legs that bolted on the bottom of the pier. These legs had screwed feet at the ends for fine adjustments.

Adjusting latitude was crude - use a spanner to roughly adjust the tilt. Then the tripod feet are screened up/down to make fine adjustments.

Adjusting azimuth ... looks like you have that part on the top of the pier.

On the dec axis there was a large metal plate with cradle to hold OTA. Originally it came with a metal strap to go over the OTA but I found this was not very satisfactory and on mine I used a length of seatbelt webbing with loops sewn in the ends - this was far more satisfactory and kinder to the OTA - mine was a 10” Sonotube cardboard thing.

The motor was driven by a mains powered “drive corrector” (box of electronics) which typically puts out a variable frequency 240VAC output for the RA motor, such that the frequency can be altered between about 45 to 60 HZ to achieve slow-motion in RA (mainly for photographers).

The little box with the buttons is the handset to operate the RA drive corrector.

I see yours has the dec drive, consisting of a tangent arm under the cradle driven by a screw thread to move the arm. Most of us had a manual flexible cable to turn that shaft manually, in that era very few ever had motorised the dec axis.

As for the OTA ... I see you have a mirror, that can be recoated. Keep an eye out for a three vane diagonal holder, and a 0.965” focusser (probably Unitron or Polarex), though I guess you’ll replace that anyway with a modern one.

Before powering this up I’d strongly suggest get it checked by an electrician - if the insulation on the wiring has gone stiff with age and broken, or there are wires hanging out it could make the whole mount dangerously live with mains.

If you wanted to get it going again it’s usually not hard to find stepping motors and gearboxes that will work nicely from 12 VDC.

[croweater]

Hi Malcolm. I have had this mount for over 25yrs. Here is a pic. Cheers Richard

[UniPol]

Some info from Astro-Optical's 1983 catalogue may help you Malcolm.

[croweater]

Some more photos Malcolm. The "unknown part" is the drive wheel that has rubber insert to act as a clutch. It is slid on polar shaft to be turned by the worm drive.After the drive wheel/ cog is on a locking clamp with rubber clutch is slid on and clamped there with a collar. When the clutch is tightened it pushes against the drive wheel to drive the polar axis. This works well as the worm and cog are left driving all the time. Hope it makes sense. Cheers Richard ps The graduated circle screwed on the face of the drive wheel is the RA setting circle

[Malcolm]

Thanks to all for the valuable info, much appreciated. :-) M.

[doppler]

I have an 8"f6 AOS dob from that era and it would seem the primary mirrors were not overcoated, the original coating on mine came of pretty easily before re silvering.

[Malcolm]

The catalogue that UniPol posted shows that what I have is likely an E10 which has an F6 mirror. I can only find F5 replacements and I'm not sure what if anything would occur if I replaced the mirror with an F5 from say Bintel. I'm asked for a re-coat quote from Palmway Optical in Tuncurry, regardless it's not likely to happen anytime soon as I asked in my group for donations towards restoring a 114/900 scope that was donated a while back and the response was tumbleweed. Fortunately the secondary is in good condition.

[doppler]

You would have to move the primary mirror up the tube closer to the secondary to achieve focus. This would require drilling some holes in the tube, not hard to do but hard to workout the correct distance required. Newer primary cell designs require cutting the tube to shorten it. The balance point would change, this would only be an issue with a dob but not with an EQ mounted scope.

Rick

[leon]

Well that brings back memories I got my first 8'' mirror from Astro Optical in Melbourne.:)

Gee that was some time ago.

If I recall they were situated in a Arcade somewhere not sure of the street though :shrug:

Leon :thumbsup:

[UniPol]

Midcity Arcade, 200 Bourke St.

[torana68]

you may think recoating is not worth it but that mirrior could well be better than a new replacement, depends on how much you have to spend I guess.

[leon]

Midcity Arcade, yep that's the one, and Bourke st, thanks for that.

Leon

[croweater]

Email sent with photos as requested. :)

[sketchism]

thanks for this thread, i actually got quite a bit of information on it!

it turns out my dec control knob had been installed incorreclt in the past, and had a spacer under it leading to me being unable to use the knob to control dec

now a huge issue but i am restoring it back to its former glory


i am now running the 240V control box from 12v, does anyone have any tips on polar aligning other than point, pray, wait haha

[Malcolm]

Matt, sent you a PM. :-)