I was able to boot up FocusMax tonight and just go directly to “find star” and then “focus” and then “run 10 V-curves”. It had no problem finding a star, getting it into the bounding box, and then focusing in on it.

I set the exposure time back to 5s. That is working great. Given how bright the star it found is at even 500 steps out-of-focus, I might even move it down to 3s. Probably 1s would be fine near focus, but it would do a lot of thrashing out near the ends. There is probably a happy medium exposure length where the thrashing at the ends is minimal but the focus run goes faster.

For the first time, I got FocusMax to actually focus using the Focus button. That was really cool. It took 283s to make it happen. That was with 8s exposures. I bet with 5s, it would be about halve that, and with 3s, even faster.

Nice. Things are starting to come together. Maybe. (:

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.

ASCOM driver: EasyFocus
Min steps: 0
Max steps: 30000
Speed: 250/Full

Pumpkin + 300d + FF/FR + no Ha + IDAS LPS = position 23456

I had a bunch of stuff on my TODO list after last night.

So I took care of some of it while the sun was up today.

I recharged the deep-cycle battery.

I figured out how to get the FocusMax windows back (thanks to some help from a friend).

I got the COM ports for the ST-4 and G-11 figured out, so both can connect to MaxIM.

I upgraded to the latest version of ASCOM (5.5.1) and the latest Gemini ASCOM driver (Gemini .NET).

I moved the laptop into the docking station and the ST-4 on top of the docking station.

I re-soldered the flat box and the polar scope illuminator (which I also wrapped in heatshrink, which will hopefully make it stronger).

I hooked up a 12v power supply near the flat box so it won’t overvolt (and has a nice power switch).

I found the Gizmo (still need to make sure it’s working).

I worked on Velcroing the cables a bit (still needs work).

I cleaned up the observatory somewhat.

In short, with the focusing that happened yesterday, I am just about ready to get shooting as soon as the sun goes down. w00t!

Clear Sky Clock said it would be cloudy all night, so of course it stayed 90% clear until about midnight, when it socked in. But I’m getting ahead of myself…

I decided to get the autoguider up and running tonight. I wanted everything focused and aligned so that I can get started shooting again for real.

On top of this desire, my new clip-in Ha filter showed up today, and I really wanted to try it out!

So I hooked up the autoguider, got it all focused and balanced the rig. I booted up the scope, which wanted to cold-start again. No problem. Quick slew to Betelgeuse… and that’s where the problems started.

For some reason, the main scope and its finder (which were aligned as recently as 2 days ago, and have not been touched) are no longer in alignment. No problem; I see the star in the finder, I’ll just sweep the scope around until I find it.

No dice.

I don’t know what my problem was, but I tried everything I could think of, including sweeping the scope by hand, and I could not find *anything*. It took me 40 minutes to finally stumble over Rigel and then get the finder and scope aligned. While that was in the vicinity, I set up the guide scope to be roughly aligned, too.

As part of this fun, I figured out that the reticle is not centered in the guiding eyepiece. Again. That is a silly feature. But I figured out how to get it centered, so now the guide finder, guide scope, and reticle eyepiece all agree about the center of the field. Which is nice.

So after losing about 45 minutes of clear sky, I got the scope turned on and started an alignment run… the deep cycle battery died. argh. OK, set up the 15v power supply — deal with the battery later. Now I’m working the alignment (oh, I had mis-calculated GMT earlier in the evening, too — I was having a bit of a day), and the polar alignment is way off compared to a few days ago. Pulled out the polar alignment scope illuminator, and it’s got a busted power cable. Again. That is the worst design ever. I decided to just go forward with it; I’ll deal with polar alignment later. I need to be using my Gizmo anyway. Where is that thing? hmm…

OK, so I’m aligned. I boot up the computer, and shoot a test image of Betelgeuse through the Ha filter. It is of course not in focus. No problem. Fire up FocusMax (nothing can go wrong with the focuser — it’s on COM1), and …

all of the FocusMax windows show up offscreen. I have no idea why. I even tried to Regedit them into place; no dice. Meanwhile, tick, tick, tick, clear sky still, but I can see clouds moving in. Also, Orion is now well past meridian. grr!

Fine. I fire up the focuser in MaxIM (I tried to get the ST-4 and mount working in MaxIM, too, but needed to reinstall the USB-to-Serial drivers for reasons passing understanding, and never got that working right — you guessed it, deal with it later), did an autofocus run in MaxIM for the first time ever.

Let me say at this point that I really like the new MaxIM focus routine. It brings up a V-curve just like FocusMax, and while it seems to converge on a solution a little more slowly, it does seem to get there pretty well, as evidenced by the fact that in just a few minutes, I had autofocused the Ha filter on Betelgeuse! (FWHM of ~5.5, high winds and encroaching clouds and sketchy collimation, so give me a break, this is about what I usually get)

So I fired a 40sec exposure of Betelgeuse, so I could see some diffraction spikes, and got a bright fuzzy ball with lots of stars in the background. I looked up, and couldn’t even see the star through the cloud cover. OK, I get it. So I slewed over to M42 anyway, because I was going to make sure I was in focus.

A couple of 40sec and then 2min frames of M42 looked pretty good given they were clearly destroyed by clouds.

I tried to set up the ST-4, but it spent a lot of time losing the star and giving me “E E” followed by “-E -E” type corrections, so I turned it off. I only like guiding in MaxIM if I can help it.

At this point, it was about midnight, and we get to where I started this post… socked in solid with clouds, and no images to show for it.

And a longer todo list.

But a few more things are set up again, including of all things, the autofocus routine in MaxIM! Cool.

Fingers crossed for a clear night this weekend. Next one won’t be wasted.

I had moved the ST-4 to the main scope to do some periodic error testing on the mount at higher magnification. This helped me to see the errors more clearly, but also left me unable to do any DSO photography.

Also, I hadn’t rebalanced the mount since swapping in the 3/8-to-1/4 adapter, and I hadn’t rebuilt the pointing model since tweaking the polar alignment.

So I decided to do some maintenance tonight so that I can get some photography in before the moon is bright again.

While the D70 was off the mount, I popped the MPCC onto it. This required refocusing the scope, which meant some head-scratching with FocusMax before I got a good V-curve. That took over an hour. grr.

I hooked up the power cable and the shutter cable to the 300D (they run in the opposite direction from the rest of the cables, which makes things a little odd, but DSLRFocus wouldn’t find the camera. Took me a couple of minutes to figure out that I forgot to hook up the USB (image download) cable, too; I need a USB extension cable (and a free USB port — yikes). I used the parallel shutter release cable — I was worried that the 300D DSUSB would conflict with the D70 DSUSB, plus I’m out of free USB ports. At the moment, I’m using 4 USB ports + RS232 port + parallel port. That all works with the docking station so that I can just pull the laptop whenever I want. Adding the image download cable too will mean that I have to remember to unplug each time (or I need to use a USB hub).

I tabled the idea of using the 300D until I get it all hooked up. But it was good to try to start it up so that I can see what I’m working with.

Building the pointing model went fast; I’m pretty good at it. There are a very skimpy number of bright stars overhead right now. I pointed at every one I could, and only got 6 or 7. The polar alignment is improved in Az: 13′ -> 7′. El is about the same, 5′. Polar alignment is a very iterative process.

The new model put M57 (my target for the night) smack dab in the middle of the D70’s sensor (so close to the center, in fact, that the image-tweaking thumbnail in MaxIM bracketed the object — nice!).

Finding a guidestar and calibrating went easily tonight.

Because the focusing run took so long, I ended up grabbing an hour of data on M57 yet didn’t get to bed until 2am. ouch.

The rig is ready to roll now, though, with the exception of the 300D USB cable and the still-misaligned polar alignment.

I’ve decided to leave PE concerns for another day and concentrate on imaging. The autoguider is able to keep up with the errors at 2350mm, so I’m going to spend less time worrying about it.

Once I get the source of noise in the mount figured out (might be a faulty motor), I think the PE in the system is really low.

This is the second clear night I’ve had since Valentine’s Day. It was clear all night, but obviously it wasn’t really a night for deep sky photography.

I used the time to get Focusmax autofocusing working. I ran off 12 V-curves, and decided to take a shot of the moon while I was at it.

1) rack focuser all the way in, set this to 30,000 (pos1)
2) drive focuser out until it stops, see what FM says the focuser pos is
(pos2)
3) set one end to 0 and the other end to pos1-pos2

4) set max increment to same as step size in FM (100)

see the LazyFocus manual

Art Morton wrote:

>
> On Jan 31, 2009, at 12:04 PM, Jimbo S. Harris wrote:
>
>> Let me screw around with that and see if I can get MaxIm and FM to do
>> 1×1 binning.
> Check the Pixel size in Max. It will quite clear if they are binned.
The really irritating thing is that sometimes FM tells Max to bin and

sometimes it doesn’t. It’s like it says “use these parms and shoot a
pic” but the parms it chooses are not directly editable from with FM or
Max.Because it changes stuff midstream. sigh.

I got FM to work once or twice, and it did produce good focus. But I’m
not comfy with it yet; it still goes haywire a lot.

J

Art Morton wrote:
> With a couple more moon nights you will have a perfectly calibrated G-11

I hope so; It really is a lot of new stuff to learn. Someday I’m going
to have to throw the Canon 300D into the mix, too. If I had enough
scopes to do it, I could in theory shoot 2 main images at once. I’ve
been wanting to do some piggybacked constellation shots…
> and the Newt is throwing stars that are in the ~ 1.72 4.x range for
> FWHM, or at least that is what I can get from the image you have sent me.
I’m not sure how good the FWHM in the original images are; The JPG is

stretched, unsharp masked, and most importantly resized (down) from the
original.
> That seems to be a fantastic improvement in focus …. at least the
> numbers are lower.
The focus distance between what FM came up with and my Mark II eyeball
was ~20 focuser step units. Effective.
> What size are the pixels on the Bayer matrix? It has to be large,

> 56 microns or so?
I think we’re both agreeing that the pixels are all 7.6mu, but that
since they come from a 2×2 square array and get interpolated, I’m
effectively using 15.2mu pixels.
> I am back to plotting angular resolution, point spread function,
> resolution….. and total madness.

I spent some time carefully measuring the focal distance from the MPCC
(and the WO FF/FR I got for the 66) to the CCD. Both flatteners are set
up for ~55mm (+/- 5%), and this is within tolerance of where I’m at with
both. I’m a little peeved at the curved field that I’m still getting
with the WO reducer; I might try adding a short spacer to see if that
helps. But the MPCC is really cooking. The field is *flat*.
> Why, a corrected newt 8” may be in order. I am quite excited to see

> that the stars in the corners of your images are quite round.
Did I send you the PNG? M51 is a tiny object; the corners of the JPG are
nowhere near the corners of the full frame. The stars at the corners of
the full frame are round, too, though. (:
> It is way to early in the season to have a scope so close to perfect
> for the new season…………… Don’t you need some more struggle.

More struggle, he says. 3 nights of fighting FM, trying to learn Max 5,
guider logs with 1” and 2” errors, building a lightbox for flats after
spending the afternoon cleaning optics, collimating in the middle of a
session… more struggle, he says. (:

So when are you coming down?

J