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[ATM] 16" Binos 1st light, an after action report.
Greetings All,
Having no idea how to start this thread, I'm just going to say "Wow, what an
experience!" Only two things could have made it better:
A) The weather for Chiefland during our stay was mostly cloudy, with periods of
fair to good, and moments of very good skies.
B) I failed to properly engineer the altitude drive. I'll comment on this now
as it should help anyone else trying to motorize Mel's Tri-Dob mount.
The short answer is if your going to motorize a Tri-Dob, you either
drive it in altitude from the center altitude sector OR from BOTH of the outward
altitude sectors. If, like I did, you attempt to drive it from only one of the
outward altitude sectors, your in for a surprise.
The problem with a single outward altitude sector drive is, as the motor
starts to move the scope in altitude, it creates an unbalanced torque. As a
result of this torque, before any motion in altitude occurs, the altitude
sectors shift laterally on the two un-driven altitude rollers, creating a small
azimuth motion. While all of my altitude rollers had a groove for the altitude
sectors to ride in, it doesn't take much room to cause a fairly large azimuth
shift in the field of view thru the eyepieces.
Since I could not come up with a quick and simple field repair to solve
this problem, both altitude and azimuth motors were disengaged and the scope was
pushed around for the remainder of our stay at Chiefland. Asides from the
weather and the altitude engineering failure, everything else worked great.
With the problems out of the way, here are a few links to some pictures,
followed by a short time line, and finally some observing reports.
http://lerch.no-ip.com/atm/Projects/DF_Optics_16_Bino_misc/page_01.htm
A) Stepper motor fly wheels / worm couplings
B) Azimuth ground ring
C) The "Christian Cross" as a certain name was used in vain frequently
during its fabrication
D) Rocker Box w/ skirts
E) Inter-Optical collimation joints and supports
http://lerch.no-ip.com/atm/Projects/DF_Optics_16-Bino_1st_Light/page_01.htm
Pictures from the day after first light.
Time Line:
Monday, 11-8-04
09:00 work on completing the "to do" list, which I inappropriately assume
won't take long. All I had to do was create some light shields to attach to the
upper rings, sew up some skirts for the rocker cage, create cover's for the
optics, and pack for the trip on Tuesday. Simple, I thought
Tuesday, 11-9-04
15:00 Finally on the road to Chiefland, did I mention I haven't been to
bed yet?
17:40 Arrive at Chiefland, thankful I made it before they closed the field
to vehicular traffic, did I mention it rained most of trip there?
19:00 Van's unloaded, camp site setup, start assembling the scope. Did I
mention the scope has NEVER been fully assembled? Did I mention its REALLY DARK
and the skies are clear? :)
Scope assembly goes like this:
A) Place azimuth ground ring on a somewhat level spot
B) Put the cross on top of the Az ring
C) Put the rocker box on top of the cross
D) Attach the 8 pairs of truss tubes
E) Slip the upper rotating rings on to the tops of the truss tubes.
F) Connect the drive to the computer
The whole assembly process took at most 30 minutes, where we proceeded to
collimate it for the first time. Surprisingly, this too goes very smoothly. I
had already made sure the secondaries were centered and properly offset, and
that the primaries were centered in their cells. At this point we slip the
laser collimator in, and start collimating each half of the bino.
A) Adjust tip tilt of tertiary, so that the holographic grid is centered on
the secondary.
B) Adjust tip tilt of secondary, so that the grid is centered on the primary
C) Adjust tip tilt of Primary, so the beam returns back on itself
D) Repeat for the other half of the scope.
E) Slip some eyepieces in, focus each side, and merge the images with the
inter optical collimation knobs.
While this collimation method isn't the best, its good enough for first
light. At this point, we don't know about the altitude drive problem yet, so we
blissfully slew over to the Pleiades to attempt and align the finder. In
blissful ignorance I grab the hand pad and start searching for our target.
First I hit the Left / Right buttons on the handpad, and I seem to have very
fluid azimuth motion. Then I hit the Up button, and instead of going UP, it
slews left a full field of view THEN starts going up. When I release the
button, it stops going up, and slews back to the right another field of view.
Somewhat confused I push the down button, and get the opposite effect (slew
right, then down, release button, stops going down, then slews back left).
At this point I'm pretty confused, and I'm thinking I must have screwed up
and put some type of really strange backlash compensation values into the config
file. After about an hour of screwing around, Ron suggests I just disengage the
motors and push it around for the rest of the night. After another 30 minutes
of screwing around, I concede, and disengage the motors. Fortunately, the
alt/az system seems to work fine in push around mode.
I can't say exactly what time first light was, as I was rapidly approaching
40 hours with no sleep. On top of that I'd been working all out on this scope
for the last two weeks, and the entire OTA and mount was built in less than 30
days (the creation date on the first cad file is 10-8-04). In any event, the
Pleiades were the first objects viewed, and I recall thinking we must have a dew
problem as the stars were surrounded by nebulosity! The rest of the night was
pretty much a blur for me, fortunately Ron and the crowd that gathered were
still sharp. I recall someone showing up with a magnificent pair of 24mm
Panoptics to replace my El-Cheapo 25mm plossels.
For the rest of the night, I recall I looked at stuff, and thinking "Yea,
that looks pretty good". But what I remember most, while melting into my chair
as a blob with a silly grin, was hearing observers say things like:
"I've never seen so much contrast and color in Orion!"
"I've never seen it so large and with so much detail, it fills the
eyepiece!" (referring to NGC-253)
"You don't just see the arms of M33, you can see structure, and that there
are gaps in the arms, and look at that nebula IN the tip of the arm!"
"M110 is huge, and I easily see two dark lanes in Andromeda"
"I've only seen photographs of that cluster in the outer rim of Andromeda
before!"
"My God, You gotta come look at the Crab!"
All in All, it was a great experience. All that's left is a short to do list:
1) Fix the alt drive by extending it over to the other outward sector
2) Replace the wooden cross with an aluminum version for additional stiffness
3) Powder coat the bare aluminum
4) Add Dew Heaters!!!!!!
5) Create a cloth shroud for less than dark observing sites
Take Care,
James Lerch
http://lerch.no-ip.com/atm (My telescope construction,testing, and coating site)
"Anything that can happen, will happen" -Stephen Pollock from:
"Particle Physics for Non-Physicists: A Tour of the Microcosmos"
" Press on: nothing in the world can take the place of perseverance.
Talent will not; nothing is more common than unsuccessful men with talent.
Genius will not; unrewarded genius is almost a proverb.
Education will not; the world is full of educated derelicts.
Persistence and determination alone are omnipotent. "
Calvin Coolidge
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