AUTOSTAR INFORMATION Last updated: 22 June 2000

Autostar Comet Eccentricity Patch

this is valid for both v2.0h and v2.0i for a  #497 (ETX) Autostar.

This patch changes the "valid range" of Eccentricities for Comets
from its current: zero to (Not quite) 1.0 
to: zero to 1.5
Thus allowing Meade's TLE data for comet Linear S4 to be entered and
tracked. 

Three locations must be changed:
 loc     old      new
3F851    80       C0
3F8A4    80       C0
59190    80       C0

That changes a "ldd #x3F80" to "ldd #x3FC0"
3F80 is binary floating point for 1.0000
3FC0 is binary floating point for 1.5000

As noted in previous patches, I use FRHED,
a freeware hex editor from http://www.tu-darmstadt.de/~rkibria

You just 
(a) make a BACKUP COPY of autostar.rom (found in the Ephemerides
directory)
(b) start frhed and use its File>Open dialog to open the Ephemerides'
autostar.rom
(c) use control-G to get the "goto" window
(d) enter  x3F851  into that, click [ok]
(e) the cursor will be on the byte that wants to be changed.
(f) type a "C"  to change the "8" to "C"
(g) repeat steps d-e-f for x3f8a4  and x59190
(h) use frhed's  File>Save to save the changes
(i) exit frhed
(j) fire up the Autostar Updater and click the [new software] button.

have fun
--dick

From:	rseymour@wolfenet.com (richard seymour)
I am pleased to report that the patch i sent about the 497 autostar also
works  for the 495 Autostar, version 2.0i (and probably 2.0h).

But: there is one additional operation when patching the 495 Autostar.
Meade uses a "checksum" during the uploading, so a value has to be added
to the file to correct for the change.

In the satellite-to-the-second patch (STTS, see below), the new values
were smaller than the originals, so we only had to add the difference.

In this patch, the new values are larger, so the extra byte becomes a
puzzle.
*I* do not have a 495.  So i cannot test various values.

If they do a signed byte-sum, then the extra value will probably be 40
(hexadecimal).
Also, the STTS patch bytes were all on even locations, so they lined up
during a 16-bit summation.
The Eccentric patch falls on both even and odd bytes.  That may also
affect the checksum.
Only testing (or Meade telling us what to do) will yield an answer.
(the test is benign... the Autostar Updater complains about the file,
rather than downloading it).

So: to allow your Autostar to accept (from the keypad) and track Comets
with eccentricities greater than or equal to one, change the following
four locations: (the first three match the 497)(all numbers are Hex)

Location    old   new
3f851       80     c0
3f8a4       80     c0
59190       80     c0
a0000    (empty)   40   (?)

An alternate approach would be to subtract the extra value from an
unneeded byte.
In that case, i'd suggest changing   9ffd0  from ff  to   3f

Good luck... if you try this, please let me know which fourth-byte
method worked!
--dick
rseymour@wolfenet.com

p.s. STTS: in case you missed it, you can get the Autostar to report
Satellite AOS times to the second.
Since pushing [select] multiple times for the same pass of the same
satellite can get different results,
this helps choose the best AOS for your situation. 
(all numbers are Hex, works for 2.0g/h/i)

For a 495:
Loc      old     new
59510    84       6f
59524    84       6f
a0000  (empty)    2a   

For a 497:
Loc      old      new
594fc    4c       37
59510    4c       37

p.p.s.  If you want to do -both- patches on a 495, make one of the
"extra" bytes be at A0001, or sum them (hence 2a+40=6a)

Return to the top of this page.

Go back to the Autostar Information page.

Go back to the ETX Home Page.