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.  :)

No comments:

Post a Comment