Saturday, October 26, 2024
Issue #609: HOP, HOP, Astro-Hop!
Well, well, well, muchachos… November is almost here, and it looks as if we in Possum Swamp may have dodged a bullet hurricane-wise this season. The skies had been improving since the thunderstorms of summer diminished, and that had got me to thinking it might be time to do some visual deep sky observing in the ol’ backyard. Maybe even with my “big” telescope in these latter days, Zelda, a Zhumell (GSO) 10-inch Dobsonian.
Maybe.
While clearer and drier as September came in, the sky could still be hazy, and
there is considerable light pollution here at the suburban Chaos Manor South.
Not horrible like downtown, no, but enough to make locating objects with
a finder scope, much less a zero-power red-dot finder, a right good pain in the
rear. I got to thinking I might want to put digital setting circles on
Zelda.
If you’re a
long-time fan of the Little Ol’ AstroBlog from Possum Swamp, you know I had
DSCs on my long-gone truss tube Dob, Old Betsy. Sky Commanders they was, and
they worked a treat. I think I saw more with Bets in the first year or
two I had the ‘Commanders than I’d seen with her the previous decade. So,
I started shopping. But it turned out ordering circles for the Dob wouldn't be so easy this time.
The problem, it
appeared, would be mounting the encoders, the widgets that tell
the DSC computer where the scope is pointed, to Zelda’s somewhat different
altitude and azimuth axes. She is nicely equipped with smooth bearings and large
tension knobs for altitude and a lazy-Susan-style azimuth bearing system, but
those things make encoder mounting more complicated than with a simpler “Teflon
on Ebony Star” Dobbie.
I did find a set
of DSCs available with an encoder hardware kit for my GSO, but it was
expensive, would have to be ordered from overseas, and it appeared I’d have to
ship them one of the mount’s altitude trunnions for modification. All the way
to Australia. That seemed like a deal-breaker to moi. I kept looking and
found a digital circle vendor stateside who could provide encoders and encoder
mountings for Z, but still…more than I was comfortable paying given—to be
honest—the limited number of nights I observe with the Z-girl. If only
there were another way…
Then, I ran
across a YouTube video about that “another way.” It seemed there was a (free) program
for smartphones, both iOS and Android smartphones, AstroHopper,
that used a phone to replace digital setting circles. Unk was mighty skeptical,
however.
Folks tried that
years ago when smartphone astronomy apps that could find sky objects with the
aid of a phone’s compass became popular. Oh, they worked well enough to point
the way to naked eye objects but weren’t nearly accurate enough for use
with a telescope. I didn’t imagine anything had changed, but I watched some more
YouTube videos on AstroHopper anyhow.
Surprisingly, the
consensus seemed to be AstroHopper does work with a telescope and
delivers accuracy similar to DSCs. I did
note video posters seemed to have a range of results from “works great” to
“well, sorta works.” Sounded to me like I should at least have a look-see
at AstroHopper’s website, which I did: AstroHopper - Web Application for Sky
Navigation Manual.
AstroHopper
(formerly known as SkyHopper) is a free and open-source web application
developed by Artyom Beilis that helps to find objects across the night sky. It
does this by allowing an accurate hop from a well-known and easily identifiable
star to other fainter stars or DSO by measuring changes in pointing angles of
the cell phone using built in gyroscope and gravity sensors. It is similar to
Digital Setting Circles implemented in a smart phone.
Then came
the hard part, figuring out how to mount the phone on the telescope’s tube. It needs to be secure and needs to be
pointing along the scope’s optical axis. I had a couple of ideas how I might do
that if ‘Hopper worked, but I certainly wasn’t going to go drillin’ holes in
poor Zelda’s OTA without being convinced this was for real. The
solution, then?
What came to
mind was a smartphone camera mount for telescopes I’d bought some time back to
take afocal Moon pictures for an S&T Test Report. Maybe I could use the
phone-holder part of it to affix Siri to Zelda’s tube temporarily? I taped the holder to Z with blue painters’
tape (to avoid damaging Zelda’s finish) using enough tape to ensure the iPhone
would be held as securely as possible. I inserted my iPhone 14 Pro Max into the
taped-down camera mount and called that “good enough.”
It looked
wacky and Rube Goldberg-ish,
and as a mild September evening came in, I didn’t have much hope. Hell, I felt
a little silly, y’all. Nevertheless, I got Miss Z into the
backyard, inserted a reasonably low power (50x), reasonably wide-field (70⁰)
Bresser 25mm ocular into Zelda’s focuser, and got started.
I hadn’t
installed the app on the phone yet. You don’t have to; you can just run
it as a web page. Obviously, you have to have an internet connection, though,
so if you plan to go to a dark site somewheres without a cell tower signal, you
need to install AstroHopper on the phone (full instructions are on the
‘Hopper website). Anyhoo, with the web page up (it was in red-screen mode from
the get-go), I set out to put it to the acid test.
When you have
the app onscreen, you’ll get step by step instructions as to how to align AstroHopper,
but in truth there ain’t much to it. Find a bright star near the object of your
desire, center it in the eyepiece, tap “align” on the app, and touch the alignment
star (or planet) on the displayed star chart.
Once ‘Hopper says it is aligned, enter your target's designation in a search box and you
will be given onscreen directions—a line pointing the way and azimuth and
altitude distance figures—to your object. Then, yep, just move the scope to the
indicated spot and there you are. That’s what the app said, but, yeah, your
skeptical old Uncle was skeptical.
Hokay, alignment star… I was after M13 as a first object, and while Herc was purty high on the September evening when I first gave AstroHopper a go, we were still experiencing some of the humidity and haze of summer, and I thought a brighter star than one of Hercules’ suns would be easier. Alkaid in Ursa Major, the end star of the dipper’s handle, was still well above the horizon. A bit far from the Great Globular, but, well, I was after an acid test. If (more like “when,” I thought) it didn’t work, I’d find a star closer to M13.
Alkaid in the
center of the 25mm Bresser’s field (could have rounded up a crosshair eyepiece,
but didn’t), I clicked “align,” and chose Alkaid on the map. StarHopper
claimed it was aligned, so I typed M13 in the little box and followed the app’s directions to the
Great Glob. When it indicated we was there, I put my eye to the eyepiece,
expecting absolutely nothing…
Damn! There
was M13! Not
centered, no, but not on the field edge, either. Howsabout M92? Boom! M57?
There was the little smoke ring. M56? Looked better than I thought it would. I
was frankly amazed. I can only suppose cell phone compasses and accelerometers
have improved a lot over the years. And obviously Mr. Beilis is a talented
programmer.
Takeaways?
Having an alignment star reasonably close to the target object helps, but it
doesn’t have to be right next door. As with many alt-az DSC and goto systems,
avoid alignment stars that are near zenith. Also, if you let your phone go to
sleep, you will have to realign. It will claim to still be
aligned, but it won’t be. Finally, yes, AstroHopper worked. It
worked as well as many DSCs and better than some I’ve used. Only aligning on
one star and using a compass and accelerometers rather than inherently more
accurate encoders means it doesn’t yield the horizon-to-horizon alignment of
the Sky Commanders, but for my purposes it is good enough.
Convinced
AstroHopper at least worked, the next step for your old Uncle was
ginning up some kind o’ more elegant mounting for the iPhone than fricking
masking tape. That was easy enough to
do. The camera mount came with a knob-headed bolt that screws into the back of
the phone-holder portion. I hated to take an electric drill to Zelda’s
beautiful black steel tube, but if AstroHopper worked consistently, I judged doing
surgery on the girl would be worth it as it might impel me to get Z under the
stars more frequently.
I drilled an
appropriate hole in Zeldas’s tube, and after I was done spent a little time
cleaning up that hole with a file. Done, I inserted that knob-head bolt through
the hole and fastened the phone-holder down. The result looked purty darned
good, I must say. Now to see if my original success had been a fluke. Why not
undertake “A Trio of Fall Globulars” from The Urban Astronomer’s
Guide? The sky was clear, and all were riding high…
To cut to the chase? AstroHopper’s performance the first time out was not a fluke; it did every bit as well on this evening. Casually aligning on a star (no high-power crosshair eyepiece) again yielded good accuracy. I didn’t try to quantify it, but it appeared I could hit targets at least 20⁰ from alignment stars. Most objects were near the center of the field, some were centered, and none was “out.” I was happy with my phone mount, and had remembered to set “lock screen” to “never” so the iPhone didn’t go to sleep and ruin my alignment, so this run went considerably more smoothly than the first one.
So, me and
Zelda hopped from globular to globular under (once again) humid and hazy October skies. How
did those globs look in the 10-inch? That, muchachos, is a story for
next time. While it seemed I’d only been out under the stars a few minutes, the
falling dew and the wheeling vault of heaven that had sent old Hercules into
the horizon told me Z and I had been voyaging the sky for hours, not minutes. I
reluctantly covered the girl and headed inside for TV and Yell with the felines
(well, catnip for them). Need I say it? It was a good night, y’all.
The
Comet…
Of course, your lazy old Unk saw the comet, but being
lazy, waited till Tsuchinshan-ATLAS had rounded the Sun and got into the
evening sky before hunting her up. A good buddy of mine and a longtime friend
of this here blog, astrophotographer Max Harrell, got some lovely
pictures from our local dark site. Alas, the evening he and some other fellers
headed out there was my teaching day (and night) at the University. So, I had
to be content with the front yard of Chaos Manor South, which offers a view low
enough in the west to allow me to spot the visitor.
And spot her visually
was about all I did. I scanned around in the correct area with my
much-loved Burgess 15x70 binoculars, and finally saw…well…a slightly
fuzzy star. My SeeStar, Suzie, laughed at me and told me to go back in
the house and have some Rebel Yell while she fetched the comet. Which
she did in rather impressive fashion (above) given the sky quality and the
comet’s low altitude.
Next
Time: A Trio of Fall Globulars with
Zelda and Suzie…
Very nice review. And I must say indeed the phone sensors have vastly improved thanks to VR/AR trend.
Good thing I'm such terrible star hopper :-)
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