Tuesday, December 26, 2023

Celestron First Scope Find

I'm using the three eyepieces I've had since the early 1980s when I bought my first 'scope, the rich-field 8" aperture, F/2.9 Sky Research Dobsonian, which are 28mm, 20mm and 7mm. The longer eyepieces give a nice image in this little 'scope, but the 7mm one is a bit cloudy. I'm thinking of getting a better eyepiece to replace it.

The First Scope also has screw mounts for a finder, but with the 28mm eyepiece in place it has a wide enough field of view to serve as its own finder, given the primary mirror's 76mm diameter and 300mm focal length.

It didn't come with a cover cap for the front of the body tube, so I figured I could 3D print one. I printed it in red PETG filament instead of the more usual PLA, since I wanted to print it in red and I had a spare roll of PETG from Ethan. Print time was a bit over an hour, because I'd over-designed it, making it thicker than it needed to be.

I printed the cap with a 4mm center hole, which I ended up drilling out to receive a 10/24 machine screw to afix the knob to, a part I found in my spare parts bin.

I'm pretty happy with the way the red body cap turned out. I intend on designing and printing a holder for the three eyepieces next, perhaps also in matching red.

I've only been able to look through the kitchen window at distant trees across the road, it's been a bit cool (!) lately (tonight will be down into the teens farenheit) but soon I'll get it outside for a proper view of stellar objects. It's a modest little 'scope, but is extremely easy to carry around and use. However, since it lacks a proper tripod bushing under its base, I intend on using my Bruneau's Pneumatic Tripod (an archaic photography tripod from long ago, that I use for the ABQ Box Camera) with a sizable wooden base to serve as a tabletop surface upon which to support the little 'scope.

Here's a phone shot taken on the day I brought home the little 'scope from the thrift store:

With a regular eyepiece in place, the image is full-sized and looks much better than the phone shot.

As I wrote in the piece above, I haven't been doing much stargazing these last few years, mainly because the convenience of back- or frontyard viewing has been negated by mature trees and neighbors' security lighting, which implies I've been a "fair-weather astronomer" all these years, not desiring to go to the trouble of heading out to some other location. So I wasn't in the market for another telescope that I wouldn't get much use out of, but for $11 this little 'scope was hard to pass up. Maybe it'll get me out more often, since I can essentially keep it in my car, as it's so easy to tote around. It'll even work well on the hood of my car if need be, no tripod necessary.

Friday, December 08, 2023

Wrangling Some Hermes's

This older-style H3K I got from a local collector, while the most recent find that I worked on earlier this week, the middle-era H3K, I got from my friend Bill. They're very similar mechanically. The curvy, first generation version has metal carriage end-cap plates, while the 2nd and 3rd generation versions are plastic. The 2nd and 3rd generation also don't have the sliding feet brackets like the first one does, so they're a bit less intricate to disassemble. I think if you're comfortable working on any of the three versions, the others shouldn't be a problem.

Besides working on these two Hermes's, I did a repair job on the Olivetti Praxis 48, also acquired from Bill. Besides needing a good clean, the main problem was the clutch mechanism for the powered carriage return was slipping and making a horrendous noise. It turned out the ring-shaped cork surface on the inside face of the plastic pulley was slipping. I made a corresponding ring of fine sandpaper and double-sided-taped it to the corresponding face of the metal clutch disc, rendering it functional once again.

I really like the Praxis 48, not only for its style but functionality. The owners manual states it's capable of 160 words per minute. I can't type that fast but I appreciate that it can keep up with whatever I throw at it. The machine sports some interlocks that prevents two type bars from overtyping the same space. It has a nifty paper centering scale that many machines from this era lacked, and the margins are set electrically. Here's a glamour shot of the Praxis 48:

Olivetti Praxis 48

Here's a video about the Praxis 48: