Epiphany is a wonderful thing.

You thrash around for a long time, trying to figure out the solution to a wooly problem, and then all of a sudden, it comes to you.

Trixie’s Dob bearings were jumping off the rails of the rocker.

And I finally hit upon the solution. And it was dead simple.

A few minutes with a miter box, and Trixie suddenly had new sideboards to keep the bearings from sliding off-track. I added the furniture glides as well, and suddenly, Trixie’s altitude motion problem was solved. It was exhilarating.

The altitude motion was so easy that I immediately discovered that, as I suspected, the scope is a little nose-heavy. So I Velcroed a counterweight to the back of the mirror cell, and that solved the problem.
The movement in altitude is just smooth. In fact, it’s smooth enough that the azimuth movement now feels a little jerky. I’ll have to loosen the pivot bolt a little and see if I can fix that.

At this point, the complaints about scope performance turned into quibbles. Yes, I could add felt here to stop some rubbing, the poles could use insulation because they get cold, that kind of stuff. But the scope. just. works.

I spent a little time cruising around with the new rig. I visited a few new sites from the Winter and Spring sections of _Star_Watch_. I visited M36/37/38, M78, M65/M66, M51, and split Beta Monocerotis at 47x. Star hopping is still a bit unnatural to me. I like being able to find things by seeing where lines between major stars cross near the object. Maybe I’ll write my own book. I did not find M101, M97, M63, M94, M3, or NGC 2903.

The spring galaxies are *dim* compared to the winter nebulae, even when they are high in the sky. It took a *long* time to find M65/66, but once I did, I was able to find M51, which I’d spent a lot of time hunting for, but hadn’t found on the first try.

The light pollution is horrid around my house. Between neighbor’s lights and the unshielded mirror, I really took a beating trying to find fuzzies. I am certain that if I hadn’t moved on to photography, I would have stopped doing astronomy very quickly. Carting off to a dark-sky site on a random Tuesday would not really happen with small kids, and there’s not a lot to see from my backyard, even with a big yard cannon like Trixie. Sure, we’ll see how she does once the shroud gets built, and there’s a lot to be said for dark adaptation and, frankly, becoming a better observer. But I continue to be convinced that photography is the way to go as a suburban astronomer.

I’m looking forward to getting the NJP back to see how Trixie performs under duress. But I’ll keep using the Dob mount until it does. There’s cool stuff up there.

And it’s very nice to have a scope that just… works. Very cool.

As with any other Beta test, taking Trixie out under the stars revealed a few things that still need a little tweaking.

In particular, the altitude movement is garbage.

So, I spent a little time troubleshooting today. I carefully measured the rocker box and the bearings, and I found:

- the rocker box is about 1/8″ out of square. I am letting it go. That should be insignificant across 3/4″ plywood.
- The focuser-side bearing is non-vertical,
- The bearings are not angled the same amount (one bearing is rotated “clockwise” relative to the other)
- the bearings are “toe-out” (closer at the back than at the front), and
- the bearings, when parallel (I know, I’m skipping ahead, work with me), are 1/2″ wider than the rocker.

First things first.

If the bearings are off in rotation, no other measurements are really valid, so I fixed that first. The ring-side bearing looked like it was the worse offender as far as being attached incorrectly, so I moved that one.

Once I’d fixed that, I noticed that the ring-side bearing was touching a truss pole, so I filed away some wood from the bearing until it doesn’t touch the truss anymore, and voila! all of a sudden the bearings are parallel to each other, and the focuser-side bearing is vertical! w00t!

This was when I noticed the 1/2″ discrepancy (see, skipping ahead). Turns out I just simply cut the rocker box the wrong dimension. So, I had several choices on how to fix it:
1) move the rocker sides out by 1/4″ each. This would exacerbate already-bad balance problems between the rocker and ground board, and would look funny, and would be weaker than the current build. No thanks.
2) buy more wood and cut out a new rocker bottom. While this would work, it is really a gnarly and “done”-killing method. I may do this later, but not yet.
3) trim the bearing spacers. I can’t trim the non-focuser-side bearing spacer at all, as it’s barely doing the job of keeping the scope from scraping the side of the rocker. Trimming the focuser-side bearing spacer is doable, but I would have to do more modification of the bearing (as in, cut a huge chunk out of it). This was the second best idea.
4) add another layer of ply to the outside of the focuser side of the rocker box. That would give the focuser-side bearing somewhere to ride, and neatly solve the problem. Not to mention I already had chunks of wood with more or less the right arc cut into them sitting around. This is the method I chose. I looks ghetto as hell, but it works. At least enough to move on.

A little sawing, a little sanding, and now both bearings are riding in a section of wood more than large enough to handle them. Sweet!

I didn’t get a lot of chance to test tonight; I had other stuff going on. But it feels like the Dob base is nearly complete.

I still have to put in the furniture slides on the altitude axis, and I am still thinking that I will probably put in “bearing keepers”, little chunks of wood that keep the scope from sliding left and right out of the altitude bearing seats in the rocker box. I have dozens of little chunks of wood lying around waiting for just such an occasion.

And I think, barring any unforeseen, that will be that. Once I get the whole scope up and running, it’s time to take everything apart and varnish.

Well, maybe I’ll wait for warmer weather…

Well, nobody can say I didn’t pay my dues on this one. Between weeks of rain and countless trips to the hardware store, I think I earned myself a little starlight.

After causing the first snowstorm in San Francisco since 1976 (hey, I was here for that one, too… hmm…), I finished up the Dobsonian mount today, just in time for the only clear night we’re going to have for awhile. Nice!

I was shoring up the rocker box right up until dinnertime, and took everything outside after dinner to find gorgeous clear sky from horizon to horizon.

First, an observing report. Then, a report card on the scope and mount. Before I get started, here’s a pretty goofy photo of scope and builder, best I could do outside in the dark.

On with the show.

Well, I finally completed the Dobsonian mount for Trixie. The idea is that I wanted to have a backup scope for use while the NJP is in use doing photography.
I learned a lot from doing the build, and there are still a few things that need finishing up, but I’m pleased with how the mount turned out.

Here’s a look from the front of the scope:

Now for some clear sky!

I know that there is going to be a moment in the not-too-distant future where my pile of Dob base parts will suddenly take shape. I feel like I’m almost there, but there is definitely some work left to be done.

OK, part by part breakdown:
Altitude bearings:
- bearing surfaces need to be sanded flat
- Edging material needs to be attached
- Mounting holes need to be drilled
- spacers between bearing and DA need to be figured out (and do I have enough width on the base to support spacers?) I decided that it’s OK to have one pole clamp that requires a screwdriver in Dob mode. That should make the spacers work on both sides of the OTA so that the DAs will each have space between them and the bearing. I still need to check it against the actual rocker box, but I am confident that I did the math (and the cuts) right. I measured the OTA against the rocker box, and I need 2-1/2″ of spacer on one side, and 1″ of spacer on the other. I think that I can get these widths by ripping a 2×4. If so, then I can cut 2 lengths of 2×4 (>2.5″ long), rip them, and attach to DAs using 1-1/4″ (or 2-1/2″, as appropriate) screws. Then I can attach the bearings using more 1-1/4″ screws (ditto on the longer ones).
- I may need to make cutouts in the bearings for the poles to go past (can I make them strong enough with the cutouts taken out?) I don’t think I’ll need a cutout with a 1″ spacer, but I still have to figure that part out.

Rocker sides:
- slider things need to be installed (must be done after the bearings are mounted)
- mounting holes need to be drilled in lower edge

Rocker bottom: DONE 2/25 5pm
- mounting holes need to be drilled in side edges
- slider stuff needs to be trimmed to length

Ground Board:
- still needs to be cut and drilled (but I have a working CNC pattern for it)
- sliders need to be installed
- feet need to be designed and attached – I have enough hardwood 1×2 (really 3/4″ x 1-1/2″) to make 3 (1-1/2″ square) feet for the ground board. I also have enough furniture sliders to make covers for the wooden feet.
- pivot bolt needs to be installed and checked for balance, etc.

Front and back end boards:
- need to be sized (I think these need to be 25.5″ long) and cut out of remaining plywood
- how tall does the front one need to be?

I don’t know if the balance point is calculated to any accuracy at the moment; I need to check it. There will be sort of a minimum height required, or else the mirror box will scrape the rocker.

OK, work the todo list, and I’m almost there. A few focused hours when the kids are awake and I can do most of the “noisy” stuff.

Veronica is now a Dob/Equatorial Newtonian!

I have been wanting to do this for years. I am forever sitting around on a nice night, camera cranking away on the mount shooting something, and wanting to spend a little time poking around at visual astronomy.

But, since I have pared everything down to just a photography rig, I only have one mount, so while the camera is using the mount, all I have are a pair of binoculars and a pair of Mark II eyeballs.

I had this idea in my head a while ago; since Veronica has top and bottom plates anyway, what if I just threw some Dob bearings onto the plates, and used, say, a 10″ Dob base? That would give me a working scope even when the photo mount is in use, and of course, since I’d just bolted the bearings onto the mounting plates, it would be easy to pop them back off and go back to using Veronica as an astrograph.

I had even figured out that maybe I could use Losmandy DA’s to make it really easy to get the bearings on and off.

I bought (or scrounged) a 10″ Orion Dob base several years ago, but never got around to working out the details.

Until today.

With my success last weekend at carving concentric circles with the CNC machine, I knew that I was on to something. Then I ran across the scrap circles that I’d created while trying to make a mirror cell for Betty all those years ago, and I had my answer.

A quick measurement of the altitude bearing seats on the Orion Dob mount (they’re 5″, by the way), a nail to hold down the 8″ plywood circles, and about 10 minutes in CamBam, and I was ready to roll.

I put some blue painter’s tape around the edge of the bearings, so they would slide better over the “furniture slide” material of the bearing seats. Someday I can replace with better material, but it’s working for now.

A little fiddling around with spacers ensued; it turns out that about 5 flat washers is the required spacing. I have all 5 on the same side of the scope, to make my life easier, but it would work just as well with 2 on one side and 3 on the other.

I spent a little more time fiddling with the balance point, but because of the DA’s, it was very easy to make sure that both bearings were in the same spot, once I found the perfect position. It’s very repeatable, and oh, so easy to remove the bearings when I want to put Veronica back on the NJP.

And it fits together very well, if I do say so myself.

I’ve been an astronomer for 7 years now, but this is my very first “definitely visual-only” scope. Welcome, welcome, Veronica-the-Dob. Don’t worry, you’re going to spend even *more* time under the stars now!