Sunday, October 11, 2020
#568 My Yearly M13: 2020
Now, I certainly try to and usually do get out and do
astrophotography more than once a freaking year. But long stretches do often separate
my sessions. The main reason for that being the weather. As I have oft-opined here, it seems to me imaging-worthy skies have been less common over the last 8
years or so than they used to be. I’d be the last to claim you can make any conclusions about weather trends from a mere 8 years of observations, but
that is the way it seems to me.
One thing I do know for sure? In the first decade of this new century
I had many mid-summer nights of imaging and observing fun down south in Florida at the Chiefland
Astronomy Village. That good summer observing began to dry up around 2012, and Chiefland
weather the rest of the year began to decline not long after. That is one of
the reasons I have not been back to the fabled CAV in nearly five years. Even
the still somewhat hardcore (well, a little) Uncle Rod can only stand so many
nights holed up in a cotton-picking Quality Inn under cloudy skies.
Unfortunately, it ain’t just Florida skies that now seem worse year-round; the same
is true up here on the northern Gulf Coast in Possum Swamp.
Be that as it may be. Resolving to shoot M13 once a year,
yeah, ensures I get out with a camera and a telescope at least once between late
spring and early autumn. The last time I
did some honest-to-God prime focus, long exposure, guided imaging? Wellllll...that was…I can’t
exactly remember, y’all, but maybe not since last year's M13.
So it was that once bad old Hurricane Sally had become just
an unpleasant memory, and the clouds that had followed in her wake had all
flown off, I prepared to shoot my annual portrait of the big glob. Two weeks after the storm,
we were enjoying a nice stretch of weather. Plenty of Sun and blue skies with highs
in the upper 70s and lows at night in the 50s. While “50s” is a little cool for
your aged Unk’s bones, I prefer being a chilled to having the sweat
dripping off me and onto the laptop as I try to take deep sky pictures in my bumbling
So, as October came in, I would be getting out into the
backyard with telescope and camera. But which telescope and which
camera? As I said last time, I’m lazy in these latter days. What is a pretty much guaranteed way to
get recognizable deep sky shots without much effort? Shoot them with a short –
medium focal length 80mm APO (color free) refractor. My beloved 80mm William
Optic Fluorite f/7.5, “Veronica Lodge,” would fill that bill.
Veronica is elegantly and sturdily built, but still light
enough not to challenge my Celestron Advanced VX GEM mount, so that was what I
would put her on. The only question in that regard? “Guided or unguided”? The
sky Friday before last was clear, but man was it hazy. Haze scatters
light, making the light pollution of my suburban backyard worse than it is on a
clear and dry evening. That meant I’d probably limit my exposures to two minutes.
Since I’d be doing a precise polar alignment, I probably could have gotten away
with no guiding at all for 120-second shots. But since I’d have the guide
camera with me to do a Sharpcap polar alignment, why not guide?
Scope, check. Mount, check. Camera? I thought that would be my
old Canon Rebel. It’s dependable, I have an AC power supply for it, and as
things are reckoned today, the 12-year-old camera has relatively large pixels.
That ain’t a bad thing in the deep sky imaging game, campers, since “larger
pixels” naturally means “more sensitive.”
All that remained was to decide on the software I’d be
using. As always, I’d be controlling the Canon and
acquiring images with Nebulosity. The program, by Craig Stark, author of
the original PHD Guiding, will do anything I need it to do and more
including acquiring, stacking, and processing DSLR images. While it was initially
intended for use with Canon DSLRs, it also works with many astronomical CCD
I dunno about you, but when I’m imaging I do not like
hanging out at the freaking telescope. I want to sit at the computer and run
the show from there. I could have used Celestron’s CPWI program, the successor
to NexRemote, which we talked about a couple of weeks back. That would have
allowed me to control everything from the laptop including the goto alignment.
I don’t have much experience with the program yet, though, and thought it best
to keep things a mite simpler.
|The new Cartes du Ciel beta.
Likely I’d be fussing with the other software, trying to remember what little I ever knew about it. So, instead of CPWI I thought I’d use a nice, friendly, simple planetarium program with an ASCOM driver. ASCOM would give me a little onscreen hand control useful for centering objects in the camera’s frame.
What I’ve used most over the last few years when it comes to
PC planetariums is the excellent Stellarium. However, a sentimental favorite,
Cartes du Ciel, was, I heard, in a new (beta) version, 4.3. That being
the case, I thought I’d give the latest CdC a whirl. I’ve noted quite a bit of
traffic on the program’s mailing list of late, so Cartes is obviously more than
just still alive.
Guiding? I ain’t used anything but PHD2 since it came out.
And I hadn’t used anything before that but the original PHD Guiding
since the dark ages when I was photographing the skies with my old self-guiding
SBIG black and white astro-CCD. It would be PHD2 Guiding all the way. I
had to get it going on a new laptop about a year ago, and was quite not sure I
had all the settings correct—I hadn’t used it since then—but I figgered it
wouldn’t much matter with short focal length Veronica.
Anything else? Well, I was darned sure glad I checked out Sharpcap
the day before my M13 expedition to make sure all was well with it. It turned out my
subscription had expired. You see, I use the Pro version (the one with
the polar alignment tool). It ain’t freeware, being offered on a yearly
subscription basis. Seemed like I had just renewed the program for the very
reasonable fee of 15 dollars a year, but, yes, another year had flown by.
Anyhoo, it took but a few minutes to get a new subscription and a license in
place. Glad I wasn’t blindsided by that in the dark backyard, though.
So, into that backyard I went, setting up in my usual
fashion with the scope beside the deck and me and the laptop on the deck. It’s
like an observatory for somebody who doesn’t want an observatory: I can leave
the telescope set up in my secure backyard for as long as the weather stays
nice. Sitting at the patio table under a big umbrella, I’m out of the dew and
so is the PC. And I’m just steps from my den where I spend my time while the
exposures are clicking off. Oh, I check things once in a while, but watching The
Mandalorian on TV while drinking a…uh… “sarsaparilla” is a lot more fun than
watching the PHD2 guide graph, friends.
While I hadn’t used Veronica in a long while, she went
together smoothly: plunked her into the
mount’s Vixen saddle, attached her tube extension to the focuser, put my (excellent)
Hotech field flattener into that, and mounted the camera via a, natch, Canon format
|Nebulosity doing its thing.
Whoooeee. I was close to sweating even in the cooling air as
the stars winked on. Next order of bidness was polar alignment. I temporarily placed the laptop
on a little tray-table next to the scope, plugged the guide scope into
the computer’s USB port, and fired up Sharpcap.
How long does a Sharpcap polar alignment take? Maybe
10 minutes first time out. Five minutes or less after that. The process is
simple. Set the mount in home position pointing north in declination with the
counterweight down. Click in the Tools menu to start the polar alignment.
Sharpcap will expose a few frames and will shortly
tell you to rotate 90 degrees in RA. That done, you’ll use the mount’s altitude
and azimuth controls to point at the North Celestial pole with the aid of
onscreen graphics and text directions (“Move up 12’…”). How accurate is it? Now that
it takes refraction into account, I have faith that when it tells me I’m just seconds
from the pole that’s just where I am. And my results indicate it is telling
the truth. If you have a guide camera, Sharpcap is the obvious cure for
the polar alignment blues.
Polar alignment done (the somewhat course altitude/azimuth
controls on the AVX make the process more difficult on that mount than on my
Losmandy—but it’s not bad), it was time to essay a goto alignment via the StarSense
auto-align camera. I’ve never had a problem with the StarSense; it’s always
produced an alignment as good as what I can do with the normal hand control.
But there are a couple of gotchas to watch out for—one of which your hapless raconteur
encountered on this very evening.
|Full sized image.
‘Twas not to be muchachos. The StarSense did the goto
alignment successfully as always, going to four star-fields and plate solving.
When it was done, I sent the mount to Vega, which I thought would be a good
target for rough focusing. Fired up Nebulosity, started clicking off focus frames
and…no Vega did I see. Tried slewing around a little. Nope. No Vega. Sighted
along the tube and did some more slewing. Nope, sorry, Charlie.
There was nothing for it. I’d just have to calibrate the
StarSense. That is easy if you, unlike your silly Uncle, remember how to do that.
Send the mount to a bright star (Vega in my case). Get the star in the field of
an eyepiece or camera (I did that by replacing the StarSense with a red dot
finder temporarily). Press Align, and use the hand control’s direction buttons
to precisely center the star.
That sounds easy. And it is easy if you, unlike Rod, remember
to press Align, not Enter. Pressing Enter sent the mount
back to where it was in the beginning; where it thought the star oughta be. So,
Unk got to start all over from the beginning after biting the bullet and digging
out the StarSense manual.
Got ‘er done, and all should have been well. But wouldn’t
you know it? Uncle Rod did some assuming, and you know what they say
about that word. Once the calibration is done, the HC tells you you need
to do another alignment. That’s easy, just press enter and it will be executed
automatically. Silly old Rod, however, thought he should set the mount back to
home position first—which you do not need to do. You will not be
surprised to learn the AVX pointed the scope to the Earth for the first plate
solve. Power down, start over from scratch one more time.
|Zoomed in with a crop.
OK! We was rollin’ now. That’s what Unk thought, anyhow,
but the gremlins weren’t quite done with his sorry self. Time to engage Cartes
du Ciel. Started the program, connected the ASCOM driver to the mount,
clicked M13, and then the slew button, and off we went for the globular. The
mount was about halfway there when the computer went fitified with a
blue screen of death. I don’t know I’ve ever had that happen with Windows
10, but it sure did happen on this evening.
Luckily, the mount continued to M13 unaffected, I restarted
the computer, reconnected all the software, and the laptop was OK from then on.
What was the problem? Despite the fact that I was using a beta version of
Cartes, I’m guessing the culprit was actually the older ASCOM version I was
running, 6.1. By the light of day, I investigated and found some people had had
problems with that one. So, I updated to the current v6.5, even though I had had
no further problems with Cartes for the remainder of the evening.
Cartes du Ciel? Other than that hiccup, it was
wonderful. No, it does not have the pretty sky of Stellarium, but it
makes up for that with the legibility of its display in the field, and has many
more features for observers than Stellarium, despite me loving that
program very much. Go out and get the new CdC; it is another winning version in
a long string of winning versions.
The rest of the evening was frankly pedestrian in the extreme.
I got PHD2 Guiding doing its thing without a hitch. While the seeing, never
good, was degrading as time went by, my errors were just a little worse than 1”
with PPEC not turned on. Well, till M13 began to get lower on the horizon after
about an hour, and I began to approach 2”. Unfortunately, in October there ain’t
much time before the glob begins to get low; especially if, like your fumbling Uncle,
you waste at least half an hour before taking your first sub-frame. But the higher guide
error toward the end of my sequence was not a problem. Again, an 80mm scope is very
forgiving. You almost have to work not to get round stars.
|And...the clouds are back.
The denouement? Early Saturday evening, I shot a series of
T-shirt flats using the sky at dusk as illumination. As I was doing so, I witnessed
the darned old clouds begin to flow back in after giving me almost a week’s respite. Not just that...another big storm was shortly threatening the Gulf. So, I was glad I’d got out, full Moon or no (did I mention shortly after my imaging
sequence began, a fat Moon began to rise in the east?). That done, I went through the usual
processing steps with Neb: debayer both
lights and flats. Stack lights and flats into single images and combine master
flat and master light into one photo, process using Nebulosity, and do final
touchup with Photoshop.
“But what about darks, Unk? You gotta shoot darks, doncha?”
I did, Skeezix, but I did that as I was shooting the lights, automatically. I
set the Canon Rebel to subtract a dark after every image. It takes twice as
long to get through your sequence, but I find doing it that way yields better
results. With an uncooled camera like a
DSLR, it’s always best to shoot a dark immediately after the light so the
sensor is at a similar temperature.
My results? Not so bad. While something like this would never
appear in the magazine’s Gallery section (!), I’ve done worse on a hazy night in
the suburbs with big Moon rising. Frankly, this year’s shot is at least
as good as what I got in 2019 with an LX85 mount
and a Meade 8-inch ACF under similar conditions (in late 2019; the blog article didn't appear till January 2020). But you know what? This
exercise ain't about results, anyway; it’s about Unk getting his silly old self out under
the night sky with a camera and getting back to work, muchachos.
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