My NJP is future-proofed.

According to Texas Nautical, nobody but me has yet requested the new, updated polar scope reticle for the NJP. The old one is good until 2015, so I suppose it will be a little while before people really start getting desperate.

But this means, of course, that I’m (possibly? probably?) the first person in the Western Hemisphere (North America, certainly) to have one of these. w00t!

Here’s a photo of the thing:

Yes, the image is a little ghetto. But, eat your heart out, Tak owners! 04026 is some good.

Now I just need to get an updated version of TakAlign, and I’m golden…

It is hard to describe how much fun I had shooting widefields from the tripod. A lot of the shots came up out of focus, and several more came up with star trails, but it was just a blast.

Our campsite under the Sagittarius Milky Way.

I really need to build a panorama out of these three, covering the sky from The Summer Triangle in the East to Sagittarius in the West:

Later in the evening, I caught an even further reach of the Milky Way, and an old friend, The Great Andromeda Galaxy, M31 in this shot of Casseiopeia and Perseus:

And finally, in a stroke of luck, I caught this meteor (or perhaps a satellite) tumbling through the frame of this photo:

All images were shot with the Canon 350D, 18-55mm kit lens set to 18mm @ f/5.6, with exposures around 1 minute (some a little longer, some a little shorter; I was timing them by listening to the iPod — “just up to the next chorus”).

After getting the mount “close” last night but then moving the pier topper and redoing, I took a couple of runs at polar alignment tonight, too.
One thing I definitely learned is that my polar scope is misaligned in some way. Put the star on the “2010″ hash mark, run the mount in RA, and the star drifts up to 1985 and down past 2015. Maybe there’s a way to fix that without sending the mount in for repair. Maybe I’ll just ignore the polar scope for awhile…

I spent a lot of time thrashing in WCS. I seem to remember that when I was doing this with the G-11, I ended up writing down each correction I did.

I figured out that I had 2 settings incorrect. First, I had “RA star” set to “in the north” instead of “in the south”. grr. Also, much more important, I figured out that I have to set “Inverted” corrections when running on Veronica. I kept doing Elevation changes and getting back larger errors. Once I set “invert”, it converged within 3 iterations.

The mount is now at (according to my feeble understanding of WCS) about +90 in azimuth, and about -70 in elevation. I’m not sure what units the “correction factor” numbers are in WCS, but I think this is pretty close.

Before I shut down for the night, I’ll give the polar scope one last peek. But I am certain that the star won’t be “where it’s supposed to”.

I think I can get the polar alignment to a “no correction” in each axis, rather than a “really small correction”. ~90 is correctable. ~70 somewhat less so. I am shooting for <40. One more set of iterations tomorrow, then some more unguided testing. I need to recall which way is “north” in the camera, also.

Polar alignment still sucks.

Once I get the mount aligned, everything will be fine. Until then, it’s a bunch of hooey.

I need to get the mount level, because, as usual, it’s causing me no end of grief.

My assumptions about polar alignment haven’t changed with the lessons I learned tonight:
1) Once you nail the elevation setting, the azimuth is very easy to set.
2) If the mount isn’t level, you can get close, but not nearly close enough to do any useful imaging.
3) Polar scopes are great for visual work, but for imaging, you still need to get closer. Corollary: see 1). I think that a polar scope could get you *real* close if you were 100% sure about your elevation setting. More on this later.
4) Good polar alignment software is like a good mechanic — if you find one you like, hang onto it.
5) If you dial in azimuth, then dial in elevation, and you find that azimuth has changed significantly, quit messing with the axes and get the mount level. You are officially wasting time if you don’t.

I have never had a good gut feeling about polar scopes. I admit that the Takahashi one made me feel like I was really doing something. And I admit that for visual use, once I used the polar scope, I was ready to roll for the night. And I know from past experience that once you get a really solid polar alignment once, future alignments at the same site are way easier. Because then the problem is constrained to a single mount axis, and so the push-me, pull-you interaction between the axes is totally gone. It’s getting that first alignment nailed that’s key.

I might even take the mount off of the pier and polar align it from the tripod to start. Then I don’t have to worry about “is it level?”. There’s work to be done on the alignment. It always goes like this. I spend a couple of nights and a bit of a day working on the alignment, and then it’s all gravy once I get it dialed in.

While the software was gathering alignment information in Dec, I had a hint of how the RA tracking on the mount works. I got no feeling for magnitude. But wow, it sure looks pretty smooth. I didn’t see any jumps as large as 1″. Tantalizing.

I spent the night polar aligning the NJP.
Man, I love the sound of the mount as it slews. It’s… hard to describe.

The polar scope (and its attendant app) got me close enough for visual work, but when I started running unguided images of varying lengths, I noted that I was getting a *lot* of drift in Dec.

So I pulled up PemPro (my trial still has 13 days left on it), and started a software polar alignment routine. PemPro’s routine is slick, but I don’t know that it’s worth $150, given that I can’t use many of the other features.

I will have to find a polar alignment program. I’ll get to that later.

The strange thing is that I hooked up several programs (PemPro, MaxIM, and Cartes du Ciel) to the Temma all at once via ASCOM, and things got really confused. In particular, someone in the setup has north and south switched. I will hold down the “north” button on the hand controller, and watch as the scope points poleward, and in the planetarium program, the pointer is moving south. Also, I keep needing to set Dec to “-30″ in order to get the scope to point to +30 Dec.

Something that needs figuring out. I don’t know where the mistake is, but I’ll find it.

Good news is that the slews were working well. I dropped several clusters right in the FOV, with a single star alignment. Nice.

Ah, maintenance.
Things you do on sunny days and cloudy nights.

I spent some time getting Trixie in collimation today.

It came together pretty well with the Catseye.

It’s clear that the collimation shifts as the rig changes its “down” vector. I am not sure how to keep this from happening, but I think it stays pretty close at this point. Worth rebuilding.

The secondary is oversized. When all is collimated, I can see part of the focuser board in the secondary.

I stuck a post-it triangle onto the primary. That helped the center spot and the Catseye worked a lot better.

I am looking forward to trying out Trixie on the stars again. I will be interested to see how much the collimation shifts; will it affect pointing? I am thinking probably not. It’s real close.

I spent a long time collimating Veronica the other day, with the new autocollimator I bought. That experience convinced me to buy Bob’s Knobs for Veronica and Cassie.

I knew I would have to recollimate afterwards, but I was ready, at least in the case of Veronica, because I knew she was in collimation before I started, so I knew that I would only have to adjust the secondary to get her back in collimation.

Cassie is a different story, but that’s OK, too. I’m out of the night sky business for awhile, so I have plenty of time to get everything fixed up.

I was worried that collimation would take a lot of time after the install. Starting from a good base, it was really quick. Took maybe 20 minutes from the time I removed the first screw to the time I declared Veronica back in collimation and put her back outside.

Not bad. And the new Knobs really make adjustment easy.

Totally worth it.

PemPro needed some calibration before things would work today. Nothing major. I got it a little more dialed in. I finally figured out what it was complaining about — it thought it was supposed to do dark frame calibration in Max and I hadn’t set Max up with any darks. No biggie; it’s cool out tonight and the camera hasn’t been on long so I turned calibration off.

It’s in the middle of a 1 hour “Acquire Data” run. Looks like the worm without PEC is doing about +12/-8 in RA. We’ll see what PEC does to that.

Again, things are getting dialed in. The polar alignment seems pretty good, the autofocus is working, now I have the PEC thing in process.

I am just about ready for spring.

Things have changed a lot since the last time that I ran Focusmax. Among other things, I have built up a whole new astro-PC, and I never really understood FM well enough to just make it work out of the box, so I was essentially starting from scratch last night.

It was a gorgeous evening, dark sky because the moon is 3 days past full, and clear as a bell until midnight. I’ll get to that later.

I had characterized my focuser before sunset, so I knew that Pumpkin was near focus, and that the ends of the focus run were set properly.

As an aside, I also discovered “Configurations” in MaxIM. Very cool. It remembers which cameras, which exposure type, etc. were up so you can swap from “guider only = PEC” to “main cam only = Focusmax” to “main/guider = DSO”… nifty!

So I needed to set several parameters very carefully in Focusmax. I figured out several of them, but it took hours, and a lot of experimentation.

Here is how the night went.

I tried a “first light wizard”, which is supposed to “characterize” the focuser. The problem was, I couldn’t get it to stop scrolling out. It kept defocusing the star more and more until either the star was too big for the subframe, or the star was too dim for FM to detect.

I learned some things.

First, a 100×100 box is more than large enough for FM to work with a fairly out-of-focus star (anything that’s less than 1500 steps out of focus should fit, on Pumpkin). 50×50 is actually a pretty good size; it keeps “double stars” from creeping in, but you have to have the focuser in a pretty thin band of focus (within about +/- 500 steps), or you end up doing a lot of “it’s out of the box, increasing the size” stuff at the ends of the V-curves. Works, just twice or 3x slower.

You want to set a exposure length that is long enough to get a hit even when you’re at max defocus. I started with 3sec, went to 5sec and then 8sec. I think that 4 or 5 is probably the right answer now that I can restrict FM to the area near focus. Maybe lower, but again, you run into “can’t find a star, increasing exposure time” stuff, which just eats time.

I never got a first-light to complete. The “characterization” of the focuser never finished, because FM ran the star until it was bloated beyond belief and kept going until it lost the star. Here’s what I think was happening. According to something I read on the ‘net, there is a “max increment” or something like that, it’s in the focuser driver settings. I always thought this had to do with the “jog” function; ie “don’t jog more than ‘max increment’ in one go”. Something to do with overheating the motor or some such. I am now led to believe that this is “how many steps out of focus will FM go during the first light run”. So I need to change this from 10,000 (current setting; focuser never jogs more than 3500 anyway) down to about 1,500 or so. That might get the first light wizard going.

OK. So. I never got First Light working, so I just decided to force a V-curve. I did the “set the beginning, set the end, set the step size” type first, got a so-so curve, then swapped to the “set the middle, set the half-width, set the # of steps” type and ran off 3 good V-curves. With these 3 curves alone, the differential thingy (PI?) is at 26 (steps?) or so, about 50µm apart. Doing a quick calculation of focus tolerance:

Focus tolerance (depth of field) = 2 * f * d
where f is the f-ratio of the scope and d is the Airy Disk diameter, which is:
d = 2.44 * lambda * f
where 2.44 is a constant (why), lambda is the wavelength of light (bluer light has less tolerance than redder, so Ha at 656nm is easier than “white light”, which peaks near 555nm), and f is again the f-ratio.

Focus tolerance for Pumpkin in “white” (really “green”) light is 63µm. Veronica is about the same, 65µm.

So 26 steps (I already calculated the focuser to be doing ~2µm steps) is enough to hit the focus band, but getting it a little more dialed in would make me feel better. More V-curves next time out.

Now that I kind of understand what I’m doing, I need to start running lots and lots of V-curves. I’ll need curves for every setup; Each combination of scope, camera, and filter needs work. At some point, I will be able to figure out how much offset to use when the Ha filter is in; that will save time. But there is a lot of work ahead on Focusmax.

For Pumpkin, with the IDAS LPS and no Ha filter, I used exposure time of 8s, bounding box of 100, half width of 500, and step size of 25 (for 40 steps on the curves), and had pretty good success.

That’s a good starting point for V-curves for future scopes. I can crank it down to 3-5s exposures once I’m comfortable with the focuser.

I played around with different star fields. The area near M44 (but not the cluster itself; too many stars) is pretty rich with medium-brightness stars that FM seems to like.

I had to shut things down when the scope hit its safety limit and the clouds rolled in, both within a few minutes of each other, near midnight.

I had a bunch of maintenance piling up in the obvservatory, so I decided to do some of it since it’s raining all weekend.

I spent a little time getting the mount more level, and adjusting the elevation on the polar alignment. I still don’t think it’s perfect, but I think I’m closer.

The polar alignment still needs adjustment in azimuth, and a final check in elevation.

I installed the new EEPROM (v1.04; apparently 1.05 is only from Goerlich) and a new battery in the mount. I also hooked up the GPS and got the time and location correct.

I mounted up the new autoguider and tried to take a couple of daytime shots to test it out, but the observatory computer fried, so I spent the time to rebuild the observatory machine from the ground up. That took longer than I expected, but I think it’s up and running now. I was having an awful time trying to get VNC to work properly. It was running really slowly on a fresh install of Win XP SP3. After much gnashing of teeth and tearing of hair, I rebooted all the elements of the LAN (modem, router, etc), tweaked the firewall on the new machine, and installed several Windows and Dell updates. Something in there “clicked”, and now it’s up again and fast as ever.

I took the C9.25 to a local park and set up the artificial star about 75yd away. That was more than enough to get me in focus, and with a few tweaks of the collimation knobs, I saw, for the first time, *perfect* Airy disks! I was collimating at 700x, so gorgeous. The C9.25 is ready for… something. It’s back in its (new) case for now, but ready to rock.

Buoyed by that success, I decided to try to collimate Veronica, too. This was not as successful. I will have to read up on collimation, because the closest I could get to Airy disks was seeing little tiny “crosses” (even on the dimmest light), which merged “vertical” if I went one way out of focus, and “horizontal” if I went the other way. There is a ton of light being thrown off outside of the 4 main diffraction spikes, too. I think I’m closer, but I will be using the C9.25 or Pumpkin to do polar alignment and pointing models for awhile…

A very productive weekend, despite only having 90 minutes of clear sky.