Author Topic: Daylight ISS pass  (Read 3215 times)

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Offline Jimmy Andrews

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Daylight ISS pass
« on: August 29, 2014, 08:52:21 AM »
August 28, 2014
11:07-11:15 CDT (UTC-5)

This was a daylight ISS pass with Sun to my left and behind in SE at 56 degrees
ISS approach was from SW
Maximum ISS altitude 88 degrees

Astro-Physics 900GTO mount
Minimize backlash in Dec and RA.
When the Center of Gravity COG moves across the Dec or RA axis you my loose the ISS if backlash movement is excessive.

10" (RFRoyce Conical back) Newtonian f/4.5 fl=1143
The primary mirror conical back eliminates primary mirror movement (flop).
Big Barlow
90 degree MaxBright Diagonal (adds 4.1'' behind Barlow for a 3.1x Barlow)
32mm FOV=70 Eyepiece
fl=3543
f/13.95

This setup gives me a 38 arc-min FOV at eyepiece.
I can see a complete full Moon in eyepiece but just barely.

Downloaded new ISS TLE
Set PC time to within a second.
Connected Joystick
Shutdown all programs so Satellite Tracker can have all the CPU percentage/power it needs.
Disabled Wifi internet connection.  Some download/installs use a lot of CPU percentage.
This will minimize ISS jitter in eyepiece.
Started Satellite Tracker version 2.5.1 (FreeWare)

Powered up Mount after a week and did a goto to Sirius
Sirius was so close to center on cross-hairs that I did not need to resync mount after being powered down for a week.
Polar alignment was very close.  Minimize drift.
From 30 to overhead and back to 30 = 120 degrees = 8 hours at sidereal
From 30 to overhead and back to 30 = 120 degrees = 4 minutes of ISS tracking
You will need to correct for 8 hours of drift in the 4 minute ISS pass so a good polar alignment is mandatory.

Did not have time to check/set mount time before pass.
Checked mount time after pass and was off 16 seconds. 15 arc-sec X 16 = 240 arc-sec = 4 arc-min

Started tracking before ISS was above the trees.  All I saw was green at first.
Found ISS and centered with Joystick.
This is the hard part and lucky part.  Finding the ISS in bright daylight.
Saw all 4 solar panels on a blue sky background (foreground?).
Solar panels had a bronze color to them.
One of the heat exchangers flared ( dim to bright to dim).
Mount did a meridian flip at zenith and ISS was still in 38 arc-min FOV at eyepiece after flip.
I had shimmed my front ring to minimize Orthogonality (Cone) error.
Re-centered ISS with Joystick.
Back to green leaves.  I am surrounded by trees.
Stopped tracking.
Happy Happy Happy!

Jimmy Andrews
33N, 88W

Offline John Eccles

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Re: Daylight ISS pass
« Reply #1 on: August 29, 2014, 10:31:38 AM »
Thank you so much for the excellent log and report on your field experience. I enjoyed reading it and am happy that you had a good experience tracking the ISS in daylight.

John
Regards, John Eccles, Owner of Satellite Tracker Application, the Satellite Tracker Forum, and the Yahoo Groups called Satellite Tracker

Offline Scott Gee

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Re: Daylight ISS pass
« Reply #2 on: September 01, 2014, 12:32:22 PM »
Nice one, Jimmy!  I am sure this will be an inspiration for all of us!


Scott