ATM, or Victorian professional newt?

[alocky (Andrew lockwood)]

I've acquired a fairly interesting telescope, a 7" f10 newtonian, which dates from the era of silvered mirrors. There's no doubt some of the components came from a professional instrument maker of the day, but the mirror cell and mirror suggest that a replacement mirror with a different focal length was added at some point. I'm not even convinced the spider belongs in this tube either, as it all looks a bit of a mix, but the fabrication of the brass tube is quite impressive.
Anyway - I've attached some pictures and would be interested if anyone can positively identify any of the components. The finderscope looks similar to ones found on Calvers and Brownings of the era, and the focuser looks like the one on our Calver at Perth Observatory, but the mount is completely different to anything I've turned up in searches.

[Wavytone]

Impressive, and if restored optically this could be a real planet-killer.

Are the eyepieces complete with glass elements ? If so take care of these as they add significantly to the value of it, even if you choose to use modern eyepieces for observing. What’s more, while the fields of view will be very limited and the eye relief more or less nil, if they were well made they could be very good on-axis.

Are there any marks on the eyepieces to suggest their origin ? It could be as small as a single “makers mark” like a letter stamped in the metal somewhere.

The pieces in the third photo ... the yoke and a gear wheel... two questions for you:

- does the tube fit between the arms of the yoke ?
- is the rectangular object at the bottom of photo 3 some sort of counterweight ?

The reason I suggest this is that in photo #4 the OTA has two bars sticking out sideways and I’d expect these sat across the arms of the yoke, providing an altitude adjustment. In In this arrangement the tube is usually a bit unbalanced and some means of restraining it was used to control the altitude - could have been anything from a piece of string on a roller (like a fishing reel) or a long rod with an adjusting screw, so keep your eyes open for bits that don’t seem to fit at first.

I’d also guess the gear wheel was for azimuth adjustment and there was a pinion for driving that, manually operated.

If so then I think it was mounted altaz with the yoke sitting flat on top of a pier or tripod, and the tube cantilevered out on one side, rather like the Berrmount for refractors.

See http://ejamison.net/refractordobmounts.html for example.

This predates Berry by many decades which just goes to show some ideas are not entirely new.

[alocky (Andrew lockwood)]

Hi Wavy - yes, all the eyepieces have nice clear glass in good shape still in them. The eyepieces and finderscope are identical to those I've seen on Watson and Sons and Broadhurst Clarkson refractors, which were commercially available in Australia at the time. However, given the style of knurling and tooling on the secondary holder matches perfectly with the focuser, I think those parts at least came from a commercial newtonian of the era, which is a lot harder to find examples of. The only makers I've seen example of so far are Browning (later bought by Watson and Sons), Calver and Grubb and of these the closest match to the mount is the Browning - but there's a lot of differences.
Most of the old alt-az mounts you mention didn't need a counterweight, which is why I wonder if this one may have been an equatorial yoke mount, the arms are long enough for it to work in this manner. The large brass gear doesn't look like a worm wheel - these were already being made properly in this era and this has a very coarse pitch for an RA drive, so maybe there was a smaller spur gear that drove it. Most of the scopes of this era had sector drives for fine adjustment and whatever was on the other axis was probably a typical threaded rod with a sliding collar.
Before I go nuts and polish the tube up within in inch of its life I'd definitely like to find out more about the history of this thing.

Originally Posted by Wavytone

Impressive, and if restored optically this could be a real planet-killer.

Are the eyepieces complete with glass elements ? If so take care of these as they add significantly to the value of it, even if you choose to use modern eyepieces for observing. What’s more, while the fields of view will be very limited and the eye relief more or less nil, if they were well made they could be very good on-axis.

Are there any marks on the eyepieces to suggest their origin ? It could be as small as a single “makers mark” like a letter stamped in the metal somewhere.

The pieces in the third photo ... the yoke and a gear wheel... two questions for you:

- does the tube fit between the arms of the yoke ?
- is the rectangular object at the bottom of photo 3 some sort of counterweight ?

The reason I suggest this is that in photo #4 the OTA has two bars sticking out sideways and I’d expect these sat across the arms of the yoke, providing an altitude adjustment. In In this arrangement the tube is usually a bit unbalanced and some means of restraining it was used to control the altitude - could have been anything from a piece of string on a roller (like a fishing reel) or a long rod with an adjusting screw, so keep your eyes open for bits that don’t seem to fit at first.

I’d also guess the gear wheel was for azimuth adjustment and there was a pinion for driving that, manually operated.

If so then I think it was mounted altaz with the yoke sitting flat on top of a pier or tripod, and the tube cantilevered out on one side, rather like the Berrmount for refractors.

See http://ejamison.net/refractordobmounts.html for example.

This predates Berry by many decades which just goes to show some ideas are not entirely new.

[torana68 (Roger)]

Very nice