Sunday, November 6, 2016

#72 - Sunday, November 6, 2016 - The Mount Issues are Mounting

Another gorgeous night!  It was a little warmer, although I was still fighting dew, just not as much.  Because of the end of Daylight Savings, I got to get started at 6 instead of 7, which was awesome.  Also, Orion comes up an hour earlier now.  Since the first quarter moon was so high, I decided to grab a video on that before I got started, and I also grabbed a video of it on the guide scope with the QHY5, but it didn’t have good enough contrast to get a nice shot, even after messing with the gain, exposure, and gamma as much as I could.  I guess I could’ve thrown my neutral density filter on, and it wouldn’t have changed the focus because it screws onto the end of the extension tube, which just slides inside the guidescope, but oh well. 
Daylight Savings Time seemed to be causing issues with the telescope as well; it wasn’t quite getting on stars quite right.  So I replaced the alignment stars and calibration stars, and that seemed to work, so I started imaging Stephan’s Quintet.  I got two images in when I needed to do a meridian flip, so I did that, but then PHD started having fits.  During calibration, it was giving me non-orthogonality errors, so I ran the guiding assistant to see if it would help.  It didn’t, and the manual said it might be due to bad polar alignment.  RA was the main problem.  I figured maybe the time change would affect the polar alignment somehow, so I started re-doing the polar alignment, but then I accidentally touched the RA cable, which caused it to jump when it shorted.  So then I had to re-align completely.  I left the camera attached so that I could do fine alignment using BackyardNikon’s Frame & Focus feature, which uses live view.  At ISO-3200, I can see not only the stars I usually use for alignment, but even the precise goto stars show up no problem, since the D5300 will adjust the shutter speed & ISO to see something.  But its guesses as to where Vega and Altair were terrible; I actually had to go get the Telrad since it was not even close.  When this happens, it’ll usually correct itself out as I add stars, but it was consistently guessing terribly, which it shouldn’t have been because I was polar-aligned still from the previous nights.  So then I shut it down and restarted completely, and it was getting even worse, not even making it close to Vega.  I even tried putting it an hour ahead and back in Daylight time, but the result was the same.  Basically, it looked like RA wasn’t going far enough; dec was pretty close.  It was either stopping too soon, or not spinning the gears as fast as it thought it was.  It might have been my imagination, but sounded less aggressive than usual when it was moving.  After trying various things, power cycling, unplugging and replugging, changing the time, etc, it was still not working.  So I went inside to warm up and have some dinner (I brought leftovers, but Bob cooked some brats that he shared), and then I packed it up and left by 11:30.  It’s weird that it worked in the first part of the evening; it went to the moon from the home position, all the way in the south, with no issues, and also went to Stephan’s Quintet on the east side of the meridian with no issues.  It even went over to Fomalhaut, the polar alignment star I’m using, just fine.  It wasn’t until I hit the cable and made it jump.  The cable also got hit a few more times as I was re-situating it.  Oh, also, it seemed to take longer than normal to find the switch position in RA.  Bob suggested that maybe it’s time to send it out to get hypertuned, and maybe they can do the Bennett mod while they’re at it.  He said he knows someone who had their Celestron mount tuned with a guy named Dr. Clay.  It’ll cost some money, but will be cheaper than getting a new mount – the CGE mount’s original price is $3,000.  A quick look online shows a site called Deep Space Products that does it, including the Bennett mod (although you have to supply the kit), for $505 (so $855 total with the Bennett mod kit).  That sounds pretty good to me if it’ll save me the headache of the cabling issue and these other issues I’ve been having.  I can also get a dual Losmandy-Vixen ADM dovetail attachment put on there for another $110, which I was talking to Bob about last night – he thinks I should get a refractor sooner rather than later, like before I get a deep sky camera.  Seeing the results from just my guidescope, I’m inclined to agree.  There are a lot of issues shooting with the SCT, and another one is possibly cropping up – mirror shift.  It’s not a big deal to re-focus for each new target and after a meridian flip – it only takes a minute, especially now with BackyardNikon – but it might be the cause of the drift I still see.  Even with guiding, the image slowly moves across the frame, and that movement shows up in pretty much every other frame.  My RMS error isn’t too bad in PHD (about 2 arcsecs), although sometimes when I’m moving the scope at slow speed, it is a little sticky in dec, I think.  (Although, it’s my RA error that is the larger of the two – I do have some backlash).  I haven’t done the mental geometry, but it seems to be moving in the same direction each time – not the same camera direction, but the same sky direction.  This might indicate the mirror shifting as it tracks across the sky in RA.  There are two fixes I could do: use off-axis guiding (in which case, I’ll probably need to get a more sensitive CCD, but I might not, I’ll have to test), or send the scope off too for a hypertune (I could get a spring put behind the primary to keep it from shifting, since I can’t lock the mirror on this C11). 

So, a disappointing end to an otherwise spectacular weekend.  But it was a great weekend!  And I got some sleep last night.

Saturday, November 5, 2016

#71 - Saturday, November 5, 2016 - Andromeda mosaic attempt

Another fantastic night of imaging!  When I first got out there at 7, there were some thin, high clouds, so I got everything put back together and then waited till they cleared out.  I discovered that Photoshop has a mosaicking tool called Photomerge in the Automate menu, and I saw some evidence online that it will do oddly-oriented and oddly-paneled astroimages, so I decided to try a 6-panel mosaic on M31!  Since I still wanted to image nebulae in the Orion complex too when it came up, and because of the late start, I decided just to do 10x3 minute images for each panel, for a total of three hours.  I wound up having to do a meridian flip halfway through, but thankfully it happened to be just as I finished the top half of the image, so I didn’t have to think too hard to get it lined back up again on the other side.  Also, I’m glad it’s so bright – my test images to align it the way I wanted were only 15s long, just enough to see the core.  
Well, it almost worked...I seem to have a missing panel...
After that was done, I took a stack of 10x5 minute images on the Flame Nebula, up right next to the Horsehead Nebula, which is right next to the easternmost star of Orion’s Belt, Altinak.  I put the nebula up near the top of the frame so that Altinak wouldn’t just totally bloom and cause reflections and lens flare and stuff, so I just cropped out the emptiness as the bottom.  It came out pretty well, if still noisy.
           NGC 2024 Flame Nebula, Nikon D5300 on my C11, f/6.3 focal reducer, Orion Skyglow filter
Guiding: QHY5 on Orion ST-80
8x300s, ISO-3200

I left about 2:30 AM so that I wouldn’t have two completely sleep-deprived nights in a row!  Also it was cold.  Also club member Will and I were the only ones left, and Will had to leave at 2.  He collected RGB data for his awesome monochrome Andromeda image.

Daylight Savings Time ended that night, and I was worried that stuff might break, but the only thing that semi-broke was BackyardNikon; it was partway into a 300s exposure at 2 AM, and then it jumped back to -3600 seconds and was counting up from there instead.  So I just aborted it and re-started.  I’ll submit a bug report sometime this week.

Friday, November 4, 2016

#70 - Friday, November 4, 2016 - Allllllll the images

It was chilly, but boy was it a good night!  Completely clear, excellent seeing, stable atmosphere, no wind, and to top it all off, the telescope behaved very well.  My guided images are still drifting – I need to figure out why – but my stars are only a little bit smeared, so it’s livable.  I finally bought a USB thermometer so that I can record the temperature as I take my images and match lights to darks with more accuracy.  Alignment went super smoothly – its initial guesses for stars were very good, and even polar alignment was close.  I’ve been using Fomalhaut now that Altair is too high and Antares has set, or is at least behind the trees or something.  It’s just above the trees, but the C11 can see through trees pretty well.  Alignment took only 20 minutes; I arrived at 7 PM, and was imaging by 8:30.  It was awesome! 

I started with the Fireworks Galaxy, which was high in the north, but I lost a little less than half my exposures to dew.  I had to really crank up the dew heater, since we nearly hit the dew point.  I had to use the blow dryer three times as well.  Even the guide scope dewed up, so I had to crank up that dew heater as well.  I couldn’t see it with a 60s exposure, but I could make it out with 5m, so we’ll see how it comes out in stacking.

NGC 4946 Fireworks Galaxy, Nikon D5300 on my C11, f/6.3 focal reducer, Orion Skyglow filter
Guiding: QHY5 on my Orion ST-80
16x300s, ISO-3200
Well, you can see it, which is cool…the background came out pretty noisy, though.
Next, I did the Crab Nebula, since I think the last time I did it I only did 3m exposures because of light pollution.  It was high in the east.  The eastern sky at the observatory is the best, especially around 3 AM, when it is quite dark.
M1 Crab Nebula, Nikon D5300 on my C11, f/6.3 focal reducer, Orion Skyglow filter
Guiding; QHY5 on my Orion ST-80
19x300s, ISO-3200
It came out more or less like the first one – next, I’ll have to try not using the focal reducer so I can get more resolution on it.
Next, I finally did the Horsehead Nebula!  I could just make out its shape and some of the red color at 5m.  Hopefully it comes out well in stacking.  I lost a few of those to dew as well.
Horsehead Nebula, Nikon D5300 on my C11, f/6.3 focal reducer, Orion Skyglow filter
Guiding: QHY5 on my Orion ST-80
17x300s, ISO-3200

It came out a little noisy, and apparently Alnitak (easternmost star in Orion’s Belt) is a really bright star – you can see the reflections from it being just off the frame on the left.
Finally, I switched the camera over to the guidescope, and tried to fit the Flame, Horesehead, and Orion Nebulae into a single frame.  It was not to be.  I think I can get it if the Flame is at the very top of the frame and Orion is at the very bottom, but they might be cut off a bit, and I try not to have stuff too close to the edges because of coma and vignetting.  I think I’ll try a four-panel mosaic here instead.  So instead of doing the trio, I just did a wide field on Orion, which looks fantastic.  I did 1m exposures, about the limit of the guide scope unguided.  
M42 Great Nebula of Orion, Nikon D5300 on my Orion ST-80, unguided
12x60s, ISO-1600

Holy sweet goodness that came out awesome!!
I am curious to try guiding the guidescope using the main telescope…I can get like sub-pixel accuracy because the focal length of the C11 is soooo much longer than the guidescope, so little tiny movements in the guidescope will appear large and easily correctable in the C11.  I didn’t try it last night because it was already nearly 3 AM.  Perhaps later in the winter when it’s up earlier in the evening.  Right now, Orion’s not really up until about 12:30 AM.
Overall, a fantastic night!  It felt pretty cold due to the high humidity, but it was windless, which made a huge difference.  It was in the upper 30s.  Frost formed on top of my camera bag and other accessories.  It’s going to be clear Saturday night too, so I left the equipment set up.  The transparency is supposed to be not quite as good, but it looks like it’ll be another windless evening, and lower humidity, since the temperatures should be in the lower 40s instead.