HAND TRACKING THE ISS!!!

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Rotorhead
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HAND TRACKING THE ISS!!!

Unread post by Rotorhead »

Last night looked like a good one for the ISS making an almost straight-up pass over my house at about -2.2 magnitude, and I decided to make an attempt to find and track it with my dob. :?: I know, fools rush in where angels fear to tread... :roll: I set up in the clearest area of my neighbor's yard (he has almost no trees) and prefocused the telescope on Orion's stars, using my favorite old Antares W70 34mm ep as a good trade-off of magnification (56x) and FOV (1.5 degrees).

As the ISS came into view, I tried to lead it with the Telrad, and quickly switch to the ep. Man, that thing is really moving when you try to do something like that! After three unsuccessful attempts, I found that I had to lead the target by almost two degrees to get to the ep in time. On the fourth attempt, I found it! Tracking it was a bit awkward (that's an understatement!!!) but I could keep it dancing in the FOV while trying to see some details. At first, nothing, just an oblong bright object. I had no time to refocus while chasing it, so I trusted that the existing focus would become clearer as it got closer. I lost the ISS twice, but by jumping out to that two degree lead, I found that I could relocate it fairly easily. As any dob owner knows, when the dob is pointing almost straight up, turning it becomes a bit harder, since there is nothing to push on, and in the case of a tall dob like mine, I was rotating it in azimuth by hugging it and pulling on the light shroud with both hands while trying to keep my eye at the eyepiece. It suddenly occured to me that I might fall over on the scope as my body position became extreme (remember, I was on my stepladder!!). As the ISS came to its highest point, it began to resolve. Suddenly, I was seeing two distinct rectangles connected by a small bright bridge. There was some irregularity along the bridge, but the wobbly view prevented me from seeing it in too much detail. However, I am positive that I was seeing the two solar arrays and the central module, with good focus as the distance to the ISS came down to minimum. The edges of both arrays were sharp and the light was not as overwhelming as I thought it might be.

The main difficulty in hand tracking is that the apparent tracking line changes as the object gets closer. At first, with the scope at a fairly 'normal' altitude, I could easily push the dob to keep the track going. As it got higher and closer, the apparent speed increased (something that you don't notice when you're not restricted to a 1.5 degree viewing area!) and I had to twist the scope to keep it on azimuth. At the longer ranges, altitude is the main tracking element, as the ISS passed overhead, the azimuth was paramount. I had to jump off of my stepladder twice, kick it a couple of feet, reaquire the ISS with the Telrad, jump on the ladder and begin tracking again. I must have looked like a circus clown, but it worked, and I have finally done something that I was curious about for a long time. It was certainly not something that had a purpose, except to see the ISS realtime in some detail. It gave me a real chuckle to have pulled it off. :D
Bob M
15" f5 Starsplitter Dob/80mm Finder
5" Explore Scientific triplet APO on a Vixen Sphinx GEM
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Bruce D
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Unread post by Bruce D »

Bob that is so cool. I wonder if the refractor might have been easier to manage?
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Mark G
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Unread post by Mark G »

Cool Bob :!: :D & you didn't blow out your back :!: :lol:
Clear skies,

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Rotorhead
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Unread post by Rotorhead »

It was kind of a fun thing to do. But I was yelling 'holy crap' at myself a couple of times jumping on and off the ladder. :roll: It felt a little bit like an episode of 'Stupid Astronomer Tricks' or something...

Bruce, the refractor would be easier to track with most of the time, but not when the ISS was at zenith. I would have to be on all fours pushing the scope!!!
Bob M
15" f5 Starsplitter Dob/80mm Finder
5" Explore Scientific triplet APO on a Vixen Sphinx GEM
________
"He numbers all the stars, and calls each one by name." Ps 147:4
Bruce D
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Unread post by Bruce D »

yup, good point. We should try it with my sct, might be easiest
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Galactus
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Unread post by Galactus »

Bob, having tried this serveral dozen times with my small SCT, I can only tip my cap! Wow! Especially with that huge scope of yours at zenith!

If we get a period of night-time passes in May like we did last year, I intend on trying this little program I have that takes the Meade satellite tracking software and allows you to tweak it using a joystick...the most daunting thing--especially at Zenith, as you know--is tracking and focussing simultaneously...maybe this May... 8) Well done, Colonel! :wink:
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Rotorhead
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Unread post by Rotorhead »

Bruce, the only thing that I would say about hand tracking with the sct is that the narrow FOV would probably defeat you. Even with a full 1.5 degrees, I had a drunk sailor's view of the ISS. It was all over the FOV most of the time, and when I was able to keep it near the center, I'm still talking a half degree zig-zag. This was purely for fun and there's no way I could have positively identified any of the irregularities that I saw on the main module, and what looked like another part of the ISS poking out from the front array. I'm surprised that somebody didn't challenge this post as an April Fools Day joke, which it really sounds like, as I re-read it.

George, as to focus, I think that pre-focusing on a star or planet is going to be the best you can do. At the beginning of the pass, if you think about it, the ISS is about 750-1,000 miles away from you (it traveled over 1,400 miles during the other night's pass, then allow for altitude in your calculation). Even at high magnification, there is no way you could resolve anything at that distance, so your focus would look 'fuzzy' at best. The other night, I calculated that the ISS never came closer to me than about 250 miles, maybe 300. At 56x, that equals a naked-eye view at 4.6 and 5.3 miles respectively. You will not get too good a view at that distance, only a profile.
Bob M
15" f5 Starsplitter Dob/80mm Finder
5" Explore Scientific triplet APO on a Vixen Sphinx GEM
________
"He numbers all the stars, and calls each one by name." Ps 147:4
Bruce D
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Unread post by Bruce D »

I'd definately want to use a focal reducer, and the widest FOV EP I can find. On the plus side, the joystick on the handbox, combined with mis-spent hours of my youth playing 'asteroids' might give me an advantage.

I could piggyback the 66mm and try that if all else fails :idea:

I'm just finishing my set of 'Pete's Pipes' which I got for the 66mm as much as the binos - that might work well too
Bruce D
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WCGucfa
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Unread post by WCGucfa »

A great feat accomplished Bob! I used to practice spotting/tracking satellites by spotting airplanes during the day. :shock:
If you could see detail in your eyepiece, you can photograph that detail.
I'm thinking attaching a video camera at the correct fps's and capturing the best frames post shooting. Difficult yes, frustrating yes, possible YES, eventually.

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Pete
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Unread post by Pete »

I've gotten good separation of the ISS solar panels with my 28X binocular, so Bob must have had some pretty good glimpses at 50+ magnification. Using a webcam is the way to go on this. The problem is providing the magnification to the webcam in a form that can track.

Pete
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