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AutoStar: Adding the Sun

Posted: 27 January 2005

Mike here: The following is not endorsed by Meade Instruments Corporation. Neither Meade, myself, my service provider, nor the submitter of this tip can be held liable for any damage to people or property that may occur from following this tip. Use proper solar filters and other appropriate protection when attempting to view the Sun. BLINDNESS can and has happened when improperly viewing the Sun. DAMAGE to telescopes can and has happened when pointing improperly protected telescopes at the Sun. Use this tip at your own risk.

Subject:	Additional data for the sun-as-asteroid page
Sent:	Tuesday, January 25, 2005 20:59:21
From:	Richard Seymour (
Many people ask for a "TLE file" which can be dragged-and-dropped into
the Autostar Updater to add the Sun-as-Asteroid as described below. 

Here it is.  The line (for those who wish to edit their own files) is:

Sun|2005 01 1.500|0.01671|1.0|-0.0001|168.7394|114.2078|2000|357.5172|-12.0|1.00|1.0

Or, if you'd like it as a "file", it's also "attached"

have fun

This tip updates the earlier ones from 2001 that follow it. --Mike

Subject:	Sun as Asteroid... Improved!
Sent:	Saturday, September 11, 2004 18:18:49
From:	Richard Seymour (
A few years ago a student who worked with me came up with a
simple set of orbital elements to allow Autostars to GoTo the Sun.
Unfortunately they were -too- simple, and had quite  a bit of periodic error.

So i posted a note on the Astroprogramming Yahoo group 
( )
requesting better Keplerian elements for the Sun.

Juan Lacruz responded with a set of numbers derived from a JPL site
( ), specifically the Earth's elements:
( ), adjusted to create
an asteroid on "the other side of the sun". 

Converting from JPL's notation to the terms requested by the Autostar,
and rounded to match its input fields, we get the following "Asteroid" elements:

Name: Sun
epoch:  1.5 jan 2000
eccentricity:  0.016710
semi major axis:  1
inclination:  -0.0001
long asc node:  168.7394
arg of peri:  114.2078
mean anomaly:  357.5172
abs mag:  -12
mag slope: 0

At the moment, they're yielding a 2 arcminute prediction error
when compared to StarryNightPro.

have fun

From 2001:

Subject:	 if the moon's a balloon, does that make the Sun an Asteroid?
From: (Dick Seymour)
A couple of months ago Mike's site was full of questions about "how to
point an ETX at the Sun?", primarily driven by the November transit of
Mercury.  Meade, as a safety measure, doesn't provide the Sun as an
object in their database.

But they -do- provide the ability to add Satellites, Comets and
Asteroids... so I wondered, what could we call the Sun given those

Not a Satellite... the Autostar just thinks those circle the earth. Not
a comet... too weird parameters (he says without looking). But an
Asteroid... they're Sun-related... maybe one with a zero orbital radius?
So I tried that: Name: Sun,  zero for a semi-major axis, zero for
everything else, 21-Mar-1999 for Epoch (see below). Then tell the
Autostar it's 3pm, and Select/Enter/GoTo... ...the word "Calculating..."
appears.... and stays, and stays.. and stays... "Mode" fails to gain its
attention.  Finally the "Power" switch breaks the spell... (for those of
you over 45, this brings to mind the old Freiden electro-mechanical
calculators... set them to divide-by-zero and you were in for an
infinite spell of noisily spinning gears and digits...) So a
zero-orbital-radius asteroid won't work.

So I started asking friends of an astronomical (and calculational) bent:
what -would- serve as orbital parameters for the Sun (as an
asteroid)(and zero won't work)?  The responses were unanimous: "I'll get
back to you on that..." And then one of them did: a young physics
student tried to model it with an old version of Voyager on her
Macintosh.  When she gave it "zero" for a radius, it wouldn't allow it.
So she thought a little more, asking "What else could the telescope be
looking at to see the Sun?"

And the answer was elegantly simple: an asteroid... in the Earth's
orbit, but on the other side of the sun. Any attempt to see it would
have an "inconvenient" sun in the way. Bingo!  True out-of-the-box

She ran the Voyager simulation ahead a dozen years or so, viewed from
both above the sun and from the earth's surface. The "asteroid"
dutifully remained hidden behind the sun. She reported the numbers to
me, and I tried them in the Autostar... they seem to work.

They are:  Name: Sun, Epoch: 21-Mar-1999 (see below), Semi-major axis:
1.0  (that's one Astronomical Unit, the earth's orbital radius). We
cheated and called the eccentricity zero, decreeing the asteroid to
having a circular orbit.  The earth's eccentricity is 0.016, but for the
purposes, zero is probably accurate enough...

When you're entering a satellite, comet or asteroid, part of what you're
telling the Autostar is: "on -this- date we saw it -there-, and the rest
of the numbers tell you how to forecast where it'll be with -that- as a
starting point".  That date is the "Epoch". By choosing the Vernal
Equinox (the date the "body" crosses the celestial equator headed north)
(21-Mar-1999 in Greenwich) as the Epoch , the rest of the orbital
angular parameters all fall to zero... because (by definition) spring
starts when the Sun crosses the celestial equator as it moves along the
ecliptic. *And* that point is where 0 degrees (or Hours) of Right
Ascension is located.  Likewise the Mean Anomaly is zero, since that's
the measure from that crossing point to where the object is at the time
of the Epoch.  For a "magnitude" (brightness) I just said "12" and gave
it a slope of zero.

And that seems to work... if I set the Autostar's idea of "time" to a
few minutes on either side of sunrise and sunset, it either reports
"below horizon" or GoTo's the appropriate zone of the sky. Unfortunately
for my testing, I live in Seattle, and the Sun isn't forecast for
visibility anywhere in the next ten days. So I haven't been able to
verify its pointing accuracy.

Now some notes:  DO NOT TRY THIS  ... unless you have **real
astronomical grade** Solar Filters for your telescope.  You -will-
damage things, including your eyes. (Want to see -my- 35-year old
retinal scars?)  Don't even let the scope point that way with the cover
on... unless you've *also* covered the viewfinder.

My testing and analysis of how the Autostar "thinks" reveal that it only
calculates the "asteroid's" position when you first Select it.  After
that it assumes it's motionless against the background of stars.  It's
not.  The Sun moves about a degree a day (ok, ok: 0.98561 (thanks,
Tami!)) as it makes its yearly journey around the ecliptic/zodiac. That
means about a half-degree between sunrise and sunset.  You can check the
Autostar's idea on this: set the time to a bit after sunrise (use Event
to get the time), tell the Autostar to locate the Asteroid/Sun. Write
down the R.A. and Dec result.  Then reset the Autostar's clock to just
before sunset and, again, Select the Asteroid/Sun.  Note the different
numbers.  That's how far the Autostar calculates that the sun will have
moved during that day cycle.

So (very) long-period solar photography won't currently work using the
Autostar. However, that day-long half-degree shift is only a half of the
26mm eyepiece's field of view, so visual work should have no problems.

Other fun notes: The Autostar won't GoTo something "below the horizon"
(i.e. Altitude less than zero)... but it will happily -track- something
-to- below the horizon... it doesn't -stop- tracking when the Altitude
drops below zero... so don't leave your telescope unattended with low
western objects.

When playing with different numbers for the orbital parameters, I was
surprised that the Autostar didn't allow 1.0 as an eccentricity
("Invalid Number"), but that it did allow the obviously problematical
0.0 as an orbital radius.

I repeat:  DO NOT TRY SUN POINTING  ... unless you have **real
astronomical grade** Solar Filters for your telescope.  You -will-
damage things, including your eyes. You'll damage the inside of the
telescope too. Don't even let the scope point that way with the main
cover or filter on... unless you've *also* covered the front (sky) end
of the viewfinder.

Clear (night) skies...
Mike here: I remember the Freiden machines. We used them when I was an undergrad working in the Astronomy Department's Minor Planet Center.

Added later:

Quicky follow-up... due to a local weather amusement called the Puget
Sound Convergence Zone, the Sun just shown on my smidge of Seattle long
enough to test the 'scope's new Asteroid.

Result: (working from alignment marks magic-markered on masking tape to
allow instant "home" alignment for "setup")  it worked!  The scope's
shadow became a circle, and the sun ended up well within the viewfinder.
(I -don't- yet have a proper solar filter for the main lens, so that
remained closed...but I do have eclipse filters suitable for the

The Autostar's beeping of the completed tracking was quickly followed by
the sound of my arm breaking as it patted my back...

Subject:	RE: Tracking the sun
Sent:	Sunday, February 11, 2001 09:12:28
From: (Mike Hadey)
Hi Mike,

I just read the following on your Site this morning:

> Subject:	 Tracking the sun
> Sent:	Thursday, February 8, 2001 22:43:14
> From: (Frederic Hawley Jr.)
> I have 2.1ek loaded on my Autostar and I'm trying to add the SUN into
> the user objects.  I've tried to follow the instructions listed on the
> Autostar Info page ("Adding the Sun"), but I think things in the
> Autostar may have changed since these instructions were written. ........
> Mike here: Yes, that old trick won't work with 2.1ek.
> However, you can still track the Sun by just having the RA
> tracking start (see the "Quick "Align" with the Autostar on
> the Autostar Information page) and then manually slewing to
> the Sun's position (using the shadow technique).

Using the A2.4 uploader with 2.1Ek FW, I just now added the Sun per
Dick's instructions on Autostar Info page.  I think that there was (is)
a problem when Using the A2.3 SW version to upload 2.1Ek FW that went
away when I uploaded 2.1Ek with A2.4.  This also seems to have solved
the "Lunar Eclipse" bug I mentioned earlier.

Initially I just added "Sun as Asteroid"  instructions manually in the
Autostar and it seemed to work.  I thought I would try to add the Sun
Asteroid as TLE data.  I made up two .txt files (see attached) in the
appropriate format.  One for 1999 Epoch and one for 2001 Epoch.  By
using TLE format you can enter fractional information for the time of
the Vernal Equinox crossing.  I haven't a clue whether or not the
Autostar uses the fractional data.

To get the TLE data in the Autostar, I fired up the A2.4 uploader and
quickly got the main screen.  By making the Windows Explorer Folder that
contain the .txt files visible at the same time as the uploader main
screen, you can just drag and drop the two files on to the Asteroid
button.  This effectively adds the TLE data to the LibAseroid.ROM file
in the Ephemerides folder and marks them as <selected for Hndbox>.

Next you need to click on each of the Asteroid, Comet, Satellite, Tours,
etc. buttons, one at a time, and select <Send all to Autostar> (or
whatever selection you want).  Otherwise when you click on the "Send To"
button the only thing that goes up is the two Sun Asteroids.

Although the Sun is not really out over here today (as usual) I set up
in front of the patio sliders where I could see the bright spot in the
clouds with roughly the correct polar alignment.   Turned the scope on,
did and Easy align (just hit enter when it got through slewing to the
two chosen stars).  Selected 1st "Sun Asteroid" (1999 Epoch) hit
[Enter]../..\.Autostar displayed RA and date, hit [GO To]... and sure
'nuff the scope pointed pretty close to the bright spot in the clouds. 
I then selected the 2nd (2001 Epoch), repeated above, and when I hit [GO
TO] it slewed a small amount and carried merrily on tracking.  I
compared the RA and Dec values against a Freeware Astro program I have
(Adastra) and here are the results:

                    RA               Dec
Adastra             21hr 42.5m       -13deg 51'
0 Sun (1999 Ep.)    21hr 42.0m       -13deg 47'
Sun   (2001 Ep.)    21hr 43.0m       -13deg 42'

Should be good enough to get you real close. I'll find out for sure if
the Sun comes out in the near future.

I can't remember if it was Rick or Dick (Rick I think) that was having
trouble with "Sun as Asteroid".  Have any of you guys tried this after
uploading 2.1Ek with A2.4?  I don't remember reading anything about
success if you have.

I have worked this new A2.4/2.1Ek combo pretty hard for a while now and
I am pretty happy.  I know Clay has been waiting for the rest of the
results to come in (sorry to hear about your cat accident, Clay).  Other
than the scope pointing 180 deg. away from where it should have (twice,
could have been operator error, but I'm not sure), the pointing accuracy
in Polar mode seem much better than with A2.3. In Polar mode there seems
to be no "snap back" (but maybe a slow "creep after beep").  By not
downloading the astronomical data as soon as it starts A2.4 made a big
difference for me in the "user hos tility" rating. Other than the fact
that you can't download the Tour data from the handbox and the TJ tour
doesn't work at all (even with no error message on uploading) I can
definitely live with this combo (so far).  Now that I've reduced the
Read Wait value in the registry I can easily make data changes quickly
("although not as quickly as I originally thought" he says choking down
the stale crow and wiping the egg off his face).

Mike H.
Click to download (337 bytes).


I did a cut and paste of the data above into a file called Sun.ast on
which I did a drag and drop into AU A2.4.  There were no problems with
AU and no problems with 2.1Ek.  I also have Dick's original hack, using
an eccentricity of 0, in my handbox.  Not too surprisingly, there's a
slight difference of opinion between it and your two data sets. 
However, put to the test this afternoon, comparing Sun (RS) and 2001
Sun, the difference was perhaps 20% of the FOV of my 8x25 finder.
Comparing 1999 Sun against 2001 Sun, the difference wasn't worth
worrying about.  I'm sure there was a slight difference but it simply
didn't matter.  Please bear in mind that my scope alignment was very
much a seat of the pants guess which may have contributed to the small
error seen.  FWIW, after tracking the Sun for a while, I turned to
Venus.  The error seen in going from the Sun to Venus was on the order
of the same distance as Dick's initial "Sun as asteriod" versus your
work.  BTW, I was working in equitorial mode.


Subject:	Adding the Sun as an Asteroid
Sent:	Tuesday, February 13, 2001 06:19:40
From: (Autostar Software Review Project)

Clip the enclosed to a text file, call it something clever like
"Sun.ast", drag and drop it on the AU's Asteroid button, and upload the
ephemeris.  You can compare the results of using the two different

1999 Sun |1999 03 21.072|0.016|1.0| 0.0|0.0 |0.0 | 1999| 0.0 | 12.0 | 0.0| 0.00
2001 Sun |2001 03 20.056|0.016|1.0| 0.0|0.0 |0.0 | 2001| 0.0 | 12.0 | 0.0| 0.00

From: (richard seymour)
Rick sent the numbers, so i'll just send the commentary.

What they are are the parameters for an object orbiting in the
Earth's orbit, 180 degrees away from us.

They were originally developed by a physics student who works at
my lab... i was asking everybody there "what would be the orbital
parameters of the sun, if it were viewed as a satellite of the earth?".
Blank stares.... but she took it home and thunk about it, and came
up with the out-of-the-box answer... which she then tested on her
Mac with the program Voyager.

Then, since an asteroid's parameters are:
Epoch Date: WHEN   and
RA of Ascending Node: WHERE  the object crosses the celestial
 equator into the northern hemisphere, the date is Vernal Equinox,
and everything else becomes Zero. (by definition of RA).
Eccentricity and radius matches us.  I still wonder about inclination.

Something i haven't checked is: from the Keypad, you can only enter
 Epoch day-number, not fractional.  I don't know if shuffling it in
with the Updater improves upon that by truly getting the fractional
component into the Autostar.  (it won't show on a keypad editing

And that's the story behind the story...

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