Tuesday, May 26, 2020

#346 - Monday, May 25, 2020 - For Science!!

If you know me at all, you know I like science.  And you also know that the previous sentence was an understatement!  

For quite a while, I've meant to learn how to take scientific data, such as variable star observations, exoplanet transits, etc.  I got connected to the AAVSO (American Association of Variable Star Observers) by way of a friend of mine from my last astronomy club, Phil, who put me in touch with the Director of the AAVSO, Stella Kafka, because she's a female astrophysics PhD who he thought I might like to talk to for mentorship.  I resolved after our Skype call to look at adding observation runs to the beginning or end of my imaging runs, but it never happened, for one reason or another.


Since I currently have two rigs up in the backyard, but only one good monochrome camera that I quickly grew tired of swapping back and forth between the two platforms, I decided I ought to put the second rig to good use as a scientific data-taking rig!  Believe it or not, the gear requirements for taking useful observations for variable stars and exoplanets is less than for deep-sky astrophotography.  The exposures are generally shorter, your stars don't necessarily need to be round nor in focus (actually it can be helpful for them to be slightly de-focused, so as so spread the light across multiple pixels and get a more accurate reading), your camera doesn't have to be as good, and your tracking doesn't have to be as good.  As an example, on last night's The Astro Imaging Channel's presentation about amateur observing of exoplanets, NASA's Rob Zellem mentioned that he had a student who used a 6-inch reflector on a mount with such bad tracking that the star drifted 300 pixels over the course of the dataset!  

The second rig I have out in the backyard, aside from the Paramount MyT and Celestron C8 that is my pretty-picture imaging rig, is my Celestron AVX with a Vixen 8-inch f/4 Newtonian that a very generous member of my last astronomy club gave me.  I was going to use it for imaging, but I haven't yet gotten a configuration of coma corrector and the spacing between that and my camera sorted out to have the coma reduced enough to properly take pretty pictures with it.  So it's just been hangin' out in my backyard collecting pollen and spider webs underneath its Telegizmos 365 cover.

The thought occurred to me to make it a science rig a little while ago, but I couldn't decide what to do about a camera.  I definitely needed a monochrome camera.  On the upside, I still have my Starlight Xpress electronic filter wheel after swapping it out for the ZWO version that has more filter slots for the 2-inch size.  I got a carousel for it that holds 1.25" filters a while back, and I recently popped in my 1.25" Astronomik RGB filters and my Schuler BVRI photometric filters that another generous member of my last astro club gave me (I don't have the U filter, but it appears to be less important than the others) into it.  

I found a camera!

So I went a-hunting through my spare gear boxes -- all the stuff that I've acquired, usually by someone giving it to me, that I haven't put to use yet, or at least, am currently not using.  I figured there was a camera in there I had forgotten about.  And lo, there was such a camera -- an Orion Deep Space Monochrome Imager II.  

Internet image because I forgot to take my own

It's an old camera -- old enough that its manual references the fact that you have to use USB 2.0 instead of 1.1, says you need Windows 2000, XP, or Vista, and also actually says that a mouse is a requirement -- but to my delight, it has some key features for an astro camera, particularly one for doing scientific data-taking. 
  • It's a CCD chip rather than CMOS.  While CMOS is arguably more sensitive (at least, at the consumer level), CCD has a more linear performance, which is ideal for science.
  • It has big juicy pixels -- 8.6 microns!  Compared to my pretty-picture-taking CMOS camera, which has 3.8-micron pixels.  This might sound weird to the casual reader, since bigger pixels mean less resolution, right?  True -- the resolution is 2.2 arcsec/px on my Newtonian, which isn't ideal (something closer to 1 is better in most cases).  But!  Bigger pixels means more light-collecting area, and thus much higher sensitivity.  This means I can get more light in a shorter amount of time (particularly helpful considering how not-great the tracking is on my AVX).  
  • It's a cooled camera!  This one was a shocker.  I expected it to have larger pixels and to be CCD, but when I looked up its specs, I learned that it has a TEC (thermo-electric cooler) that can go down to 20 degrees C below ambient.  Woo hoo!  This is great news because it means I can have much less noisy images.  Hopefully.  I'll still have plenty of noise to deal with -- it has a ridiculously high read noise of 24 electrons/ADU, according to some guy who made the measurements and posted about it -- but it at least reduces one noise source.
  • It has a 16-bit ADC.  At least, I think it does, according to some posts I saw about it online.  Now, a lot of lower- and mid-level astro cameras have 12-bit or 14-bit ADCs (analog-to-digital converters -- basically, how many brightness levels you can encode into the saved image), which gets saved as a 16-bit number, but is really only converted to 12- or 14-bit.  Having a true 16-bit ADC is normally reserved for the higher-end cameras.  The higher the bit depth, the more brightness levels your software can discern between, which makes for a higher-contrast image, or better science data.
  • It has a small chip.  1/2" diagonal, 752x582 pixels.  Ordinarily this would be less than helpful, but since my particular problem with the Newtonian regards coma, which stretches out stars close to the edges of the field-of-view, this actually works in my favor by only imaging the "nice" center region of the FOV, which should have good-looking stars.  Also, the frames should download faster.  If Sequence Generator Pro downloaded frames in a reasonable amount of time, which it doesn't!  Even on my fast CMOS cameras, which can run 10 fps in SharpCap full-frame (or at least 2 when I'm in 16-bit mode), it takes like 5s to download the frame.  Hmph.  Anyway...
One weird thing about this camera is that the TEC runs on a 3V DC power source.  3V??  It came with a battery back that takes two D-cell batteries.  I have no idea how long those will run it for, but the manual says "it's a good idea to bring a spare set with you."  Also, I have no clue whether or not the TEC is running, since you can't turn it on/off, set the temperature, etc.  You just plug it in, and it cools to whatever 20C below ambient happens to be.  I don't want to be buying D-cell batteries all the time, so I've got an adjustable AC power converter coming in the mail from Amazon.

But does the camera work?

One pitfall of older gear is that getting a given device to work on newer computer systems is dicey, as is finding drivers for it.  Fortunately, the Orion website still had both the camera and ASCOM drivers.  The ASCOM driver installed no problem, but the camera driver file just unzipped some system files and no executables or anything that looked helpful.

So I tried opening the camera in SharpCap just with the ASCOM driver (and it did show up there), but it said it couldn't connect.  I tried a couple other programs, but they all said the same thing.  So I hit up the internet and found out that you have to install the driver in a bit of a roundabout way: if you go to Device Manager (this is Windows 10 by the way), it'll show up in the Unknown Devices list.  Click Update Driver, and choose the "browse local files" option.  Then go to the folder where these driver files are located.  The wizard installed the driver from those files, and bingo, it worked!  I was able to open the camera in SharpCap, and it did show changes in light level when I took the cap on and off.  Success!  

Connecting things together

The next step was to get it installed on the telescope.  I currently had an M42-M48 converter ring on the focuser so I could connect the coma corrector, but I needed to take it off since my filter wheel has an M42 connector (M42 is the same as T2 or T-thread).  Unfortunately, it was pretty well stuck on there, and after many attempts, I was unable to remove it.  So I grabbed one of the spacers that came with my ZWO camera, a 16.5mm guy, which has M48 female on one side and M42 male on the other.  It effectively works as a converter.  I got it all put together, but the telescope is unfortunately too close to the fence to be able to see any of the things in the distance I could use to test focus.  So I had to wait for nightfall.

Once it was dark, I went outside into the blessedly cool night air -- my house had warmed up considerably in the sun to 85 degrees!  I had the windows open and fans running, but it took quite a while to cool down.  After getting my main rig hooked up and ready to go, I slewed the scope to Arcturus for focusing.  Luckily for me, the giant de-focused star appeared in the camera's tiny field-of-view, so I was able to center it before focusing.  Also luckily for me, it did come into focus!  Not a whole lot of backfocus on this scope.  I think if I'm going to put a motorized focuser on it in the future, I'm going to have to replace the whole focuser.  We shall see.  I still need to measure how parfocal my photometric filters are.

But, mount issues abound

If you've been following my blog, then you probably know that Celestron mounts have brought me little but woe.  While I did have this AVX mount working quite nicely last fall, it has again turned against me with a horrifically high amount of declination backlash.  Two months ago or so, I popped open the casing to see if I needed to adjust the gears again, but the gear meshing and tightness looked fine.  So I don't know what's causing the backlash now.  I didn't re-balance it after putting this gear on because I didn't want to have to re-do the alignment before I got it focused, so I'll do that in the morning.

First light!

I tried re-calibrating the autoguider, since it was really bad last time I tried, but it was just as bad this time.

As you can probably guess from that super-weird-looking calibration, guiding was nuts-crazy.  So was tracking -- plate solving to get the first target of the night centered just was not working.  Partly because sometimes the stars were streaked, although it still seemed to be finding those okay and not grabbing noise pixels.  But it still couldn't plate solve, and I'm not sure why.  Maybe it has to do with the other weird aspect of this camera -- the pixels aren't square.  They're slightly rectangular!  They're actually 8.6 x 8.3 microns.  SGP only has one dimension for pixel size in the plate solve settings that it feeds to the plate solve software (I'm using Planewave's PlateSolve2 software, which is free by the way!)

Target list

Earlier in the day, I worked on a target list.  The AAVSO has a target-selection tool that you can sort in a number of ways, including by how high-priority the target is.  So I scrolled through to find targets scattered throughout the night that I estimated had magnitudes within reach of my gear and were within the field-of-view I have between my house, my plum and lemon trees, and my neighbor's garage.  I put the targets and their info into a spreadsheet so I could keep track, since they each had different requirements.  For some stars, the primary researchers wanted specific channels, like just B or V.  For others, they want as much of a full set of photometry as you can take.  Some are known to be long-period variables and only need observations every week or month.  Some are changing fast and needed observations every minute for a couple hours throughout the night.  Some are currently super-dim, but are expected to erupt soon, so they only want your observations if the star gets above a specific magnitude.  So many different things!  And that's just variable stars -- I'd like to do exoplanet light curves as well here soon.  

You might recognize the name of one of those stars -- KIC 846-bunch-of-numbers.  It's the famous Tabby's Star!  Named for the Louisiana State University professor who discovered its odd behavior, this is the one that was showing dramatic dimming and brightening cycles that spurred the discussion of the chance that an alien civilization was constructing a Dyson sphere.  The real explanation is probably less fantastical, but is still being investigated.  


As you might guess, with the mount issues, the sequence did not collect any data last night.  In fact, when I checked in the morning, it had apparently tracked past the meridian enough for the loose dec axis to do the thing where it falls a bit due to gravity, which causes the motors to go crazy.  It wound up on the wrong side of the mount and pointing at the ground.  Luckily, no harm was done, although I'm going to have to re-align it tonight.  I also re-balanced it, which might help?

And the primary rig?

My main imaging rig, the Paramount MyT with my Celestron C8 and ZWO mono camera with my other filter wheel and my fancy PrimaLuce Lab Esatto focuser, ran flawlessly.  I tweaked the aggressiveness values a bit more in PHD down to 40 in RA and 70 in Dec, which seemed to help even more with the problem of huge fluctuations for M51 and M13.  The M51 guide graph still showed huge spikes in dec as high as 4 arcseconds, but the images did not suffer as much weirdness.  I was able to keep the majority of the images. *sniffles* So beautiful!!

Sunday, May 24, 2020

#344 - Saturday, May 23, 2020 - More Success! And some useful diagnostic tools

After finally getting all of my gear working, I had several nights that were mostly clear, but had lots of passing thin, high clouds that kept wrecking things and causing my sequence to abort midway through the night.  So data has been coming in very slowly.  However, the last couple of nights have been crystal-clear!

Also, side-note: Google has finally updated the user interface for Blogger!  Thank goodness.  It really looked like it was still stuck in 2002.  They took away the option to re-size images, so sorry they're kind of small.

Context Camera

When using a long-focal-length telescope, it can be hard to tell when there are clouds or tree branches in your frames.  Many people use their guide camera to see this, but since I'm using an off-axis guider, it's pretty much impossible to see those things.  So two weeks ago, I finally implemented a plan I've had for a little while.

I scrounged through my box of extra gear I haven't put to good use yet -- lots of old cameras, lenses, and other stuff people have given me.  (I will find a use for them all!).  One of my friends from when I was living in the Midwest, Will, gave me a color Meade DSI when I bought his Orion ST-80 off him to use as a guide scope on my old setup.  It's not a very good camera by today's standards, but I don't need a good camera for this.  I also grabbed my shortest focal length CCTV lens that my friend John gave me, a little 25mm guy.  A while back, I bought a T-thread to C-mount converter so I could attach these kinds of lenses to my astro cameras, so I grabbed it too from my tool box, and assembled everything together.  After installing the Meade Autostar Envisage software to run the thing (Meade cameras don't do ASCOM :( ) and seeing what kind of spacing I needed to bring distant things into focus, I figured out that I didn't need any spacers at all -- the CCTV lens was designed to sit right in front of the sensor, I guess.  Woot!  

The next task was to figure out how to rig it up on my telescope.  Currently, I have my Celestron 8-inch Schmidt-Cassegrain on my new Paramount MyT mount.  I have a short Vixen-sized dovetail bolted to the telescope tube still from back when I was running my DSLR piggyback on it a while ago, so I grabbed one of the Vixen-sized clamps I have.  Unfortunately, neither the camera nor the lens has a tripod attachment or any other useful way of attaching it to something tripod-esque.  So I did what any good engineer does -- I used some Velcro to strap it to the clamp!  It sags a big under gravity, but I don't need it to be perfectly co-boresighted with the telescope, just pointing in the same general direction.  It won't fall off the way I've got it rigged up, and that's the main thing I care about.

I figured out on the second night using it that I could use the Meade software to take a timelapse, so I set it to save an image every 30s throughout the course of the night.  This would let me go through and see why the sequence aborted, and also throw out frames where thin clouds were rolling through (this can be hard to tell in the subframes).  

It's really been paying off -- now I can see if I got too close to a tree, or if the reason I can't get a guide star is because of clouds or something else.  

New Problems, New Solutions

When more parts of your system are working, smaller issues tend to present themselves where they were buried under other issues before.  Some of my targets have had no issues, such as galaxy M88 at the beginning of the night and the Ring Nebula (M57) at the end of the night, but the Whirlpool Galaxy (M51) and some of the Hercules Cluster (globular cluster M13) have been having some strange issues.  In many of the frames, the stars appear to form a diamond pattern.

At first, I thought this was a result of diffraction around a tree branch.  But since I have added the context camera, I could go to the timestamp of when those weird subframes were taken and check and see what was going on.  No tree branches in sight.  So I wondered what the guide graphs looked like, and wished there was a way to see the whole night's guide graph.

I was poking around through the PHD2 software settings and decided to see what all the log file had in it that might be useful.  Well, as it turns out, every data point from the whole night is contained in it!  Every correction, guide star SNR, RMS error, etc.  So I decided I'd write up some code to plot the points so I could look at the whole night.

Well, before I was about to start writing the code, I did a Google search to see if anyone else had already done it.  I should have known -- of course other people have done it.  There's a nicely-packaged executable that shows you everything from the file -- it can be found here.  It will show you the calibration run as well, the data plotted in frequency-space so you can look at drive harmonics, the guide graph shows when the guide star was lost, the star's SNR, and a bunch of other useful statistics.  It's available for Windows, Mac, and Linux.  Thanks Andy Galasso!  

So I went to the portion of the night where I was imaging M51.  And the source of the diamond pattern was very obvious!

M88 guide graph -- looks good

M51 guide graph -- what the heck???

So clearly there is something weird going on with my mount in that part of the sky.  
My other two targets for the night -- M13 and M57 -- had some troubles too though.

M13 guide graph

M57 guide graph

Hmm.  Most strange.  Two thoughts:
1) My calibration isn't great -- it's not terrible, but it's not orthogonal either.  I've had this issue a lot with the off-axis guider.  I had a good calibration earlier this month, but after M88 wound up having to sit in a not-ideal place in the image in order to get a guide star in the guider's field-of-view, I rotated the off-axis guider and had to re-calibrate.  I'll try re-calibrating again tonight to see if it helps.

2) Since it's springtime, there's a lot of pollen, spiders, and spiderwebs on various parts out of the mount.  Might need to do some cleaning.  I cover it with a Telegizmos 365 cover during the day, but plenty of stuff gets on it during the night.  The gear boxes seemed sealed pretty tight, but I'll run through with a duster and air-duster and see what I can do.


Despite these issues, I'm so happy to be finally honing in on perfection.  Or, at least, as good as I can do with all of this light pollution and air pollution!  When I have good data to work with, then I can focus more on my image processing.  

There is nothing quite like waking up in the morning, going out and powering down the telescope, and seeing that the sequence completed successfully!!

Lots and lots of hard work are, at last, paying off. :D

Saturday, May 9, 2020

#334 - Wednesday, May 6, 2020 - IT'S WORKINGGGGG

As with many complex mechanical and digital systems, fixing one thing often causes two more problems. (Or more!)  Thus has been the case with all of my recent equipment upgrades.  Luckily, I love troubleshooting (big reason why I became and experimental physicist), so I've spent the last couple nights attacking some new problems.

Focus offsets

I got my new PrimaLuce Lab Esatto focuser installed on Saturday!  The SCT-threaded connection on it slides into the focuser, and you tighten three set screws into a groove on the adapter.  That way, I could set it to the exact angle I wanted, and it's a nice stable connection.  On the camera side, I got the 2-inch eyepeice-type adapter because that's the only way to connect my Lumicon off-axis guider, but this one, unlike my previous JMI EV-1 focuser, has a compression ring with three set screws rather than one.  So hopefully that will hold things in place much more firmly.

From the scope: Meade 0.63x focal reducer, PrimaLuce Lab Esatto focuser, Lumicon off-axis guider (set for ZWO camera backfocus), QHY5L-II guide camera, ZWO 7-position 2-inch electronic filter wheel, and ZWO ASI1600MM Pro camera.

I am now using two different brands of filters -- Astromonik CLS-CCD (light pollution) and RGB filters, and Chroma narrowband filters.  They have different thicknesses, so due to the difference indices of refraction, the focus points are shifted between the two filter brands.  Since I have an electronic focuser, I can measure the different focus points, program them into Sequence Generator Pro, and it will automatically move the focuser to the difference between the two when I switch filters.

The first step was to measure those offsets.  I set the CLS-CCD filter, and then ran the autofocus utility in Sequence Generator Pro four times.  (For the new PrimaLuce Lab Esatto focuser I have, I set the step size to 7,000 steps -- this is how far it will move between focus test points.  I didn't want it to move too much, or the more out-of-focus points would be too out of focus for SGP to get accurate star size measurements).  I recorded the focus position and HFR (half-flux radius, or measurement of the average size of the stars across the image), and then had it autofocus again.  I repeated this for the Ha and OIII filters.  

Then I took the average and standard deviation of those measurements, and set those as the focus positions in Sequence Generator Pro.

I don't actually have an SII filter -- it's just a filler until I get one later on.  Right now, that slot is empty.

Lastly, I needed to get the order of things ironed out in SGP.  This has been kind of tough, since I can't just say "do this, then that, then that;" SGP has its methods, and I kind of have to mess with different combinations of settings to bend it to my will.

I tried first to have it adjust the focus position per filter, and then focus with that filter (by turning off the "Auto focus with filter" option in the auto focus options).  With the variances in the offset measurements, I wasn't sure just setting the offset would be enough. 

Note: SGP doesn't use these offsets as absolute positions; rather, it will look at the last time you focused and which filter you used, and calculate the difference between that focus point and what you have set in the offset.  For example, if I have the CLS-CCD filter set at 200,000 in the filter wheel data, and the Ha filter at 210,000, and I just ran autofocus with the CLS-CCD filter and it found focus at 190,000, then it will take the difference between the actual focus (190,000) and the value in the filter list (200,000), and adjust accordingly, so that the Ha focus position is set to 200,000.  Make sense?

So I tried having it autofocus with the CLS-CCD filter, then change to the Ha filter and offset the focuser to get it close, and then autofocus with Ha to make sure it's in focus.  However, autofocusing with 3nm-wide narrowband filters doesn't work very well.  Even with 20s exposure times, I had several stars when it was near focus, but not enough for it to make accurate measurements when it was far from focus.  Plus, it took forever to run that way -- 9 focus test points, times 20s exposure time each, plus the time it takes to download and measure the stars in the image.  

So what I did instead tonight was to have it focus always with the CLS-CCD filter (a setting in the Autofocus options), and then it sets the filter offset when it changes filters.  Hopefully, this focuser would prove to be good enough that focus would be close enough just using the offsets.

Guide camera

The focus offsets caused another problem: my guide camera wasn't really in focus anymore.  I'm using an off-axis guider, and it's before the filter wheel in the optics train because trying to get a guide star through a narrowband filter would be basically impossible.  However, its focus is fixed, and moves with the camera, so when I drop in the narrowband filter, and the main camera focuses with the index of refraction difference of that filter, my guide camera is then out-of-focus.  Enough so that when I tried running things on Sunday, PHD couldn't hold onto any guide stars, and I didn't get any frames that night.  

Then I got a piece of advice from my astro-buddy Tolga: put the guide camera in focus with the main camera when the focuser is set for halfway in between the Astronomik and Chroma filters.  That way, it'll be a little out of focus for both, but not super out of focus for one or the other.  Smart!  (Of course, the real solution would be to get Chroma filters for my LRGB as well, but that's going to run me like another thousand dollars, and I'm not ready for that yet).  So on Monday night, I set the focus for halfway between the two, focused the guide camera, and then PHD was better able to hold onto the guide stars.  So that worked!

Dialing in polar alignment

I was curious about how well the mount performs unguided, so on Monday night, I opened up PHD and unticked the "Enable guide output" option in the brain dialog box.  This allowed me to see how the guide star moved around without actually sending guide commands to the mount.

It didn't exactly go running off, but it wasn't very good either.  Doing this reminded me of a tool in PHD that I've only tried one other time: drift align.  It's a way to fine-tune polar alignment by looking at how a star drifts due south and due east or west near the horizon, and then you adjust the altitude and azimuth knobs in an iterative process.  I don't have screenshots, but basically you first slew to a star at the meridian and 0 declination for the azimuth adjustment, hit Drift and watch the direction of a plotted trendline for enough samples to even out the noise, and then adjust the azimuth knobs until that trendline is mostly flat.  Then you do the same for altitude, but for a star that is due east or west, near the horizon.  There's a helpful document for this here.  I found that instead of moving the star all the way to the magenta circle, I needed to move it only like halfway to the circle -- all the way would far overshoot.  Drift alignment is a real pain and a slow process, but I've been told that it can have a real benefit for permanently-mounted scopes.  I'm not mounted on a pier, but I also don't take my gear down, so it stays pretty steady.  (Until the next earthquake, of course...)

After this, I checked whether I needed to update my T-Point model or not after this adjustment -- I slewed to a star, and while it didn't land in the middle, it wasn't super far off, and they already weren't landing in the middle before.  So I didn't touch the model.  I did re-calibrate PHD, and it looked pretty good.

A different autoguider?

Because my guide stars are so ugly -- partly because the off-axis guider is, well, off-axis, and deep in the coma of my Schmidt-Cassgrain, and partly because the stars aren't quite focused -- I decided I'd give another piece of guiding software a try, just for yucks: Metaguide.  I've used it recently for collimation, and I thought it'd be interesting to try out guiding with it.  It uses a different principle than every other method of autoguiding out there: Instead of doing long integrations (3-10s) to avoid "chasing the seeing," it sends corrections many times per second to the mount, sort of acting like a slow adpative optics-type thing.  It totally turns the thinking on its head, but the author (who spoke about it on TAIC recently) swears by it.  My hope was that it would be better able to grab oddly-shaped stars.  The interface looks a bit messy at first, but it has a lot of options and tools built in that are really handy.  

I had previously got it set up on my mount and guide camera when I was collimating my C11, so the tricky bits with doing that were already taken care of.  Calibrating ran quickly and without issue on a bright star.  Then I just needed to play with gain and exposure settings to see how short of an exposure time I could get away with.  Unfortunately, I had to do 2s exposures in order to get the guide star some of the time, so it more or less defeated the purpose.  It also didn't talk to SGP as smoothly as PHD2 does: it would frequently not "hear" the pause or stop commands, so that when SGP tried to resume, it was still already running, and SGP just sat there until its timeout ended and it's like "sure I'll just go ahead and continue the sequence anyway, assuming it's running."  

So the first frame came down, and oof.  It wasn't great.  It didn't like run away or do anything crazy, but the guiding was kind of all over the place.

Cropped image of some stars near M100, 10m exposure in OIII

The next frame was no better.

Are there some settings I could may adjust?  Perhaps.  But with 2s exposure times, when M100 has a pretty bright star right inside my guide camera, I don't think it's going to work out.  Not with an off-axis guider at least!  Might work better with a guide scope with brighter stars. 

So I switched back to PHD.

At last, success

After all these tweaks over the past couple of nights, I finally, finally had a great night.  The forecast called for an exceptionally clear sky.  The Moon was full, so I swapped out some of my wideband targets for narrowband ones.  The sequence had Ghost of Jupiter Nebula, M100, M51, and M57 Ring Nebula.  I did H-alpha on the two galaxies, and Ha and OIII on the two nebulae.  I ran out of time on the Ghost of Jupiter, so I didn't get any frames there (it goes behind my lemon tree at about 10 PM, leaving little time after astro-dark), but the rest of my M100 images and my M51 and M57 images came out really, really well.  Nice, tight, well-focused and well-guided stars, I could see signal in all the frames, no clouds, everything was great.  I didn't get a great number of frames because all my narrowband frames are 10 minutes long, but it did run all night without issue.  Yayyyyy!!!!

I settled on the following autofocus options:

Note: Step size depends entirely on your focuser.  My new focuser has a full range of some 400,000 steps.  My last focuser had a full range of only 8,000 steps, so the step size was very different.

I am also doing all plate solving with the CLS-CCD filter as well.

There's not much to see on the galaxy narrowband images, but here's a zoomed-in image of the Ring Nebula, a single 10-minute frame in Ha:

I can't see the dim halo around the Ring that I've seen in other images, but it may yet appear on stacking.  We shall see :)

Seeing in the morning that the sequence had run flawlessly the whole night and got a bunch of great images put me in a really, really good mood for the whole rest of the day.  A little bit of starshine in these difficult days.

Sunday, May 3, 2020

#331 - Friday, May 1, 2020 - A Night of Problems

Apologies for the recent long absence of blog posts!  I've been keeping log notes every night I run the scopes, but haven't had the time and/or energy lately to write up the blog posts.  Because I'm imaging nearly every night these days, I've decided I'm not going to write up every log entry as a blog post anymore -- just the ones where something interesting happens.

My sister Mary has been running a Dungeons and Dragons campaign back in Spokane, WA, my hometown, with her husband, my parents, and my other sister Melody and her husband.  Once the shelter-in-place orders started going into effect, however, they started playing online.  And they figured, if we're playing online, why don't we invite Molly??  So I hopped into their campaign at 7th level, and created a dwarf paladin character, the first time I've played a magic-wielding character in a tabletop.  (I've only played a few other times with friends and family, usually doing some kind of human rogue Katniss-esque character who's handy with a bow).  We play on Thursdays and Fridays now.  During a break, I scurried outside around 8:30 PM to set up the scope.

Gear loadout

What I've got set up now is my Paramount MyT mount, but I finally caved and swapped out my Celestron 11-inch Schmidt-Cassegrain for my Celestron 8-inch Schmidt-Cassegrain.  The C11 and its big, unwieldy, floppy mirror have been making life difficult.  I've been having trouble getting a good calibration model for autoguiding using PHD, I have to re-focus all the time (using autofocus with my JMI EV-1 focuser, but it takes several minutes every hour to do), and because of the long focal length (even with my 0.63x focal reducer, it's 1763mm), I can't always get a star in my off-axis guider, and when I do, it's deep in the coma'd outer edge of the image field, and PHD seems to have a hard time locking onto these cigar-shaped stars.  It's been working okay, but I haven't been getting as much data as I could when sequences would abort or the guiding was bad enough that I had to dump quite a few frames.

The Paramount looks kind of comical with the much-smaller scope attached, especially with the clashing colors.

New gear

On the back of the C8 is my 0.63x focal reducer still (it's also a field flattener), my ZWO ASI1600MM Pro camera, and my new ZWO 7-position 2-inch filter wheel.  I really liked my Starlight Xpress filter wheel, but it only had 5 slots at the 2-inch size, and I recently purchased Chroma 3nm Ha and OIII filters.  I'll eventually get an SII filter as well, but have plenty to do with bicolor narrowband and LRGB+narrowband enhancement.  The ZWO is working pretty well, and it accepts both M48 mounted filters as well as 50mm-ish unmounted filters, which is very handy.  I'm still going to use the Starlight Xpress filter wheel -- I got a 7-position 1.25" carousel for it (one of the things I love about it is how easy it is to swap out carousels, and the fact that you can), and I loaded it up with my Schuler Johnson-Cousins photometric filters and my Astronomik 1.25" RGB filters I bought a while back before I realized that the 1.25" size was too small for the 4/3 chip size of my ASI1600.  This way, I'll have a filter wheel handy for doing planetary imaging (using the IR photometric filter as a luminance channel, which I've had a lot of success with in the past), as well as the photometry and variable star observing I want to get into once I get a stable setup on my other mount, the Celestron AVX.  Right now the AVX has an 8-inch f/4 Vixen Newtonian that a member of my last astronomy club generously gave me, but I'm having trouble getting the coma corrector to work, and the mount's been having some backlash issues that don't appear to be connected to the meshing of the motor drive gear with the worm drive gear, which is how I usually fix that problem.

Happily, the ZWO 7-position filter wheel is nearly the same size as the Starlight Xpress filter wheel.  I was not expecting that.  (Image is on the C11)
Also, you can see one of my kitties, Nova, in the background :)

Speaking of new gear, I also recently ordered a new autofocuser.  I've been using a JMI EV-1 that my uncle gave me, which is a Crayford-style focuser that can be used manually or motorized with a hand paddle.  It doesn't have a USB connection (it's an older model), but Shoestring Astronomy sells an FCUSB adapter that's been working flawlessly.  (It has one of those 3.5mm jacks, which can plug directly into the Paramount MyT and be run from TheSkyX, but I needed one I could talk to via ASCOM so I could use it with Sequence Generator Pro).  The JMI focuser worked decently well for me with just my parfocal Astronomik LRGB filters, although since it's relative and not absolute as far as its position, it would often hit one limit or the other while SGP was focusing it if there were clouds and stuff like that, so I had to reset it fairly often.  But it did a decent job.  

Until I got the Chroma narrowband filters.  They're not parfocal with my Astronomik filters, so I needed to set filter offsets.  I ran autofocus 5x each and recorded the focus value in a spreadsheet, and then took the average value for each filter -- luminance, Ha, and OIII (since I decided to base the offset from the L filter).  The variance in the focal point varied pretty widely though -- hundreds of steps on a total length of only 8,000 steps.  But, since Schmidt-Cassegrains and their long focal lengths have a pretty wide focus point, I blamed the variance on this, and set the average value as the filter offset, but had autofocus run again after the filter change and just used the offset as a starting point.  This took a lot longer, of course, since I had to take longer exposures with the narrowband filters, but I was okay with that.  

The first night I tried running the narrowband filters was a disaster.  The filter offsets still left the image pretty out of focus, and the SGP autofocuser really needs to start with the scope close to focus, or else it has issues measuring the HFRs of the giant donut stars and things get very messy.  Confused as to why this was happening, I did a quick test: I slewed to a bright star and set the luminance filter, focused, and then racked the focuser out and then back in to the exact same place that was in focus.  Except, now, it was far from focus!  I don't think it's backlash though -- I think the tube, being Crayford style, is slipping.  My camera, off-axis guider, and filter wheel are quite heavy all together, and I don't think it can quite handle it.  So for a while, I just used my LRGB filters and no narrowband. :(

Then I finally decided to go ahead and just buy a new focuser.  I went with the PrimaLuce Lab Esatto focuser, which is a modified Crayford style but is fully motorized, no manual control.  It has a payload capacity of 11 lbs, and has a much smaller step size -- only 0.04 microns!  It has something like 400,000+ steps, haha.  But the modified Crayford style promises not to slip, so we shall see.  I got the 2-inch version, and got an SCT adapter for one side, and a 2-inch eyepiece adapter on the other side, since that's the only way my OAG can connect.  

The Esatto connects via USB-C, and requires 1A of power.  If you're using USB 2.0, that only supplies 0.5A, so you have to use the 12V DC connection to power it.  But, if you're using USB 3.0, or have a powered USB hub like I have (or using the USB hub on the back of the ZWO camera, which supplies 1A), then you don't have to use the external power.  I tested it inside (where I had to use the 12V power -- apparently my tablet's USB 3.0 port doesn't do 1A), and after upgrading the ASCOM platform from 6.3 to 6.4 SP1 in order for the PrimaLuce ASCOM driver to work, I got it moving!  Very exciting.  

I didn't have time to install it today, and I knew I wasn't going to be able to get it tested and configured before D&D started, so I will do that tomorrow.  

Tonight's imaging

Weird problems

After I got the scope uncovered and my laptop connected, I went back inside and controlled things from my desktop while we played D&D using TeamViewer.  First, I wanted to re-calibrate PHD because the guiding last night was baaaaaaad.  However, I tried like four different times on two different spots in the sky, and each had a nice, round, bright star to use, but the calibrations were garbage.  And more garbage than usual!

Like, what?????

After seeing these, I decided to do another full calibration of the mount (I had just done one last night to account for the offset in position between the C11 and the C8, as well as the fact that the C8 has less mirror flop and should give me a better calibration).  I started the automated T-Point procedure in TheSkyX, but absolutely none of the images were plate-solving.  I checked the pixel scale, and ran outside to see if clouds had rolled in -- nope, all was good.  So I connected the camera to SharpCap instead, and the image was weirdly dim.  So I shut down all the software and rebooted the computer.  SequenceGenerator Pro wouldn't open, so I rebooted it again.  Still no dice.  So I did a little Googling, and saw that sometimes it can be an ASCOM corruption issue.  And, seeing as the only change I'd made recently was upgrading the ASCOM platform, I decided to uninstall and reinstall it.  When I went to uninstall it, I chose the Repair option instead.  This worked!  SGP finally opened.  (I needed it to control the focuser, since my stars were suddenly out of focus).  

Once I had SGP up and running again, I racked the focuser in to try and bring it back into focus, but I hit 0 before it came into focus.  That was weird.  So I went outside to reset it -- put it back in the center-ish and then focus the primary mirror.  I also checked the scope to make sure everything was okay there -- and saw the cause of the problem: the OAG had partially slipped out of the JMI focuser, again.  It is a compression-ring-style connection, but with only one screw.  It slips out all the time and it's really annoying.  So I pushed it back in and tightened the screw as hard as I could, re-focused the primary, and then ran back inside (we were still playing D&D and were engaged in a tough battle).  

Finally, I started running T-Point again, and I also changed the binning from 2x2 to 1x1, since it was calculating the pixel scale with it at 1x1 I think, and not 2x2.  Once I made that fix (plus all the other stuff), plate solving was working again!  The majority of the 48 sample points solved, and the ones that didn't were likely blocked by my trees or something (I have a rough horizon model loaded, so in some places it's not quite accurate).  

Once that was complete, and I ran Super Model and re-did the polar alignment (when I swapped out telescopes, I also adjusted the position of the mount a bit, since one of the tripod feet had slipped into a crack on my concrete pad, and I didn't trust the polar alignment I did last night with the possibly-messed-up T-Point model), I then re-did my PHD autoguiding calibration.  This one came out much better -- actually, it's the best I've yet gotten with this mount!

Very exciting.

Imaging, finally

Once that was all done, it was about 11 PM, and I could finally start imaging.  (And we finally wiped out all the enemies in the dungeon chamber).  Clouds were due to roll in around 1 AM, but I figured I'd squeeze in those two hours anyway.  (Benefit of having a backyard setup!)  By this point, the target of the moment was M100, a nice spiral galaxy.  Plate solving to center it was having issues for some reason, but it eventually figured out where it was pointing and started the imaging run.  Guiding was a nice 0.69 arcsec RMS.  Aaaaaaand then the clouds rolled in early, but after I went to bed.

More fail

I went outside in the morning, and for the second time this week, the mount had run itself into the tripod leg, and instead of stopping tracking like it had earlier in the week, the mount was instead alarming and TSX said "Unable to move."  This is the first time the alarm has gone off, and luckily it was quiet-ish -- hopefully it didn't disturb my neighbors, because according to Sequence Generator Pro, it'd probably been going off since about 2 AM.  I quickly parked the mount and made sure all the camera connections were still straight.

So usually when it clouds out, SGP will try and plate solve or focus or something, it will fail, and it will keep trying until it's time to meridian flip or the sequence end time is hit, at which point it will abort the sequence, park the mount, and disconnect equipment.  However, occasionally the failure mode is the fault of Planewave's PlateSolve2 plat solver that I'm using, and sometimes when it's cloudy, it'll get an error saying something like "Instance of object does not exist" or something like that.  In that case, SGP has no idea about the error, and it's waiting on PlateSolve2 to send it the solution.  Since it's waiting, it doesn't check for sequence end time or meridian flip time, and just keeps tracking.  And tracking, and tracking....until the scope hits the pier, when TSX takes over and stops the tracking, thank goodness.  (On other mounts, this can actually mess up the gears, since not all mounts are "smart" enough to detect a blockage, and will keep trying to push).  I should eventually just get a cloud monitor, haha.  But usually the failure happens before PlateSolve2 runs, like a lost guide star or inability to focus.  I should probably report this bug to Planewave.

Anyway, very long story short, no images were acquired tonight. :(  But I'm installing the new focuser tomorrow, and now I have a solid T-Point model and PHD calibration, so once I characterize the focuser, set the autofocus settings, and measure the filter offsets, I'll be ready to go!  It's supposed to be cloudy tomorrow night, but clear on Sunday night, all night.  So I'll work on the focuser after The Astro Imaging Channel broadcast has ended.  :)