16 June 2020

I’m still here, no virus, though I did have a nasty 24-hr flu that shares many symptoms. Just been working from home, and with the 1.5 hours saved everyday from commuting, the time’s been spent getting the 16″ f/4.3 telescope done, and it nearly is.

The design is commonly called a “hexapod”, and consists of six tubes assembled into three truss assemblies 120­° apart. There are several reasons to go this way over the more traditional 4-truss 8-tube design:

1. The telescope is collimated (aligned) solely by adjusting tube length. The tube assemblies are just like the toe control links in Midlana, with each using a left and right-hand rod end to set its length. What’s interesting is, once fully assembled, turning just the upper ends of the truss ends adjusts the upper assembly tilt, and turning just the lower ends adjust its location relative to the main mirror.

2. #1 means that the main mirror cell and secondary holder do not have to be adjustable, which lowers weight, increase stiffness, reduces cost, and make the assemblies simpler—sound familiar?

3. To some extent, focusing range can be adjusted by altering the upper-to-lower assembly distance.

The last point has consumed the most time. Every primary mirror has a unique focal length, this one is 68.7″. This means that from the main mirror, to the secondary diagonal mirror, and out to the focuser has to be 68.7″ inches, sort of. The catch is that the value gets modified if a “coma corrector” lens is present. Anyway, if it ends up being wrong (outside the range of the focuser’s travel limits), the strut tube lengths can be adjusted if it’s slight, or different length threaded Delrin tube inserts may become necessary. I started with one set and found that focus was off by about 2″, so a second set was made that was 2″ longer. What’s left me scratching my head is that it didn’t correct the situation by the expected 2″. The catch is that I may or may not have had the coma corrector in place, and probably didn’t use the same eyepiece. That’s another issue, that different types and brands of eyepieces all have different focal points. This means that before the scope can really be considered finished, all the eyepieces have to be checked to confirm whether they all come to focus… and one eyepiece (one said to have a strong focus offset) is currently back ordered.

In the meantime, servo drivers for tracking start targets are being installed. Some people consider such a thing a waste, but I find it annoying having a planet or star under high magnification drift fast from the field of view, and then the scope is pushed to follow it, only to then lose it. Anyway, that system will take a bit to learn.

Even with composite construction for the upper assembly, carbon tubes, and low-profile lower assembly, the overall assembly is around 65 lbs, enough that I don’t want to carry it, so wheels and handles are being added as well. After it’s fully operational and checked out, it all has to come apart for paint. While part of me would like a furniture-grade varnish-like finish, nope, paint it will be. I don’t want to deal with the time, mess, and smell that beautiful wood finishes entail, especially all the sanding. Been there done that with Kimini, no more sanding!

The little voice in my head did ask though, “A scope, that’s nice, so how does someone who has to be in bed by 9:30-10pm in order to get up at 5am for work planning to spend hours out under the stars?” Good question, but this project and other going-ons in the garage are about planning ahead about how I’ll spend my time in retirement, someday. Anyway, through dumb luck, it turns out that Mars is going to be the closest in its orbit to Earth this Fall, so I’m really looking forward to that.

Stay safe!

04 May 2020

I’m still here but haven’t been working on Midlana. Builders, on the other hand, are pushing ahead on their builds, and you can check that out on the Midlana forum. Locally, car events keep getting cancelled, and who knows when we’ll start risking ourselves in the name of fun again. Here in Southern California, activity and travel restrictions have lessened slightly, but it seems almost certain that by the end of all this, we’ll have all been exposed to the virus, it’s just a matter of when.

Our American culture is such that we sometimes don’t like being told what to do, and often involves mention of freedom and Constitutional rights. What protesters (including anti-vaxers!) don’t understand however, is that we’re dealing with a virus that simply doesn’t care. Wanting things to go back to normal is understandable, but that’s in conflict with a virus that only cares about finding its next host. What bothers me most  is how some people figure that because they’re young and don’t have symptoms (and even if they do), what do they care? Wow.

On the other hand, the damage to the economy is dire, and I heard a pretty good analogy that went something like: “We currently have a speed limit on most freeways of 65 mph, but we could save a lot more lives if we lowered it to 20 mph.” The reality is that there’s a balance between lives lost and the economy. If you ask the protesters, we passed that point long ago. On the other hand, if you ask a mom how much should be spent treating her critically-ill child, she’ll say whatever it takes. Where the balancing point?

Anyway, I’m fortunate to be able to work from home, which has brought to light a new situation, where it’s sort of like being retired,  but not. That is, everyday feels very much like the day before, and sometimes I have to remind myself what day of the week it is. Midi, our dog, is confused because he sees me sitting for hours staring at a laptop, when I should obviously be giving him walks or tummy rubs. He’s getting old and has really slowed down lately, not helped by him hurting his foot while running around barking at the increased number of people walking by. He’s sleeping a lot more recently, to the point that sometimes I watch him to see if he’s still breathing. Yeah, I fear that he’s getting close to the end of his adventure, and I really don’t like to think about that.

To end on some positive news, I am working in the garage, just not on the car. The new workbench has been put to good use, supporting construction of the new telescope that’s been in the works for a couple years now. In other news, the wooden gear clock project has been shelved, as cutting the gears and finishing the teeth is more work than I want to do. A CNC router was tried, but even it left a lot of chipped and frayed plywood. What I’d really like is to have it cut via laser, but the only place that returned a quote wanted $600. So, it sits.

9 April 2020

Between working from home, light but long term rain, and the virus, Midlana is safe in the garage on a trickle charger. If you’ve ever driven an open wheel car in the wet, well, you’re missing out. Perhaps you remember riding a bike without fenders through a puddle, and the sudden realization that you now have a muddy racing strip down the middle of your back. Only takes once to learn that lesson. As far as driving in the wet, anything off straight-ahead results in a shower, and even after the car is dried off with a towel, everything that can rust, does.

When weather allows, work continues in the backyard, replacing our 25+ year-old railroad ties with retaining blocks. When it’s rainy, I’m in the garage working on the new telescope 🙂