2015/10/26 : new objects for tracking : Moon, Sun Halpha !

SGE - Star Guiding Emulator

SGE provides an artificial star (with synchronized DSO images) for astrophotographers to test autoguiding, periodic error, etc. indoors or in the shop !

A free star emulator software from Gilbert Grillot and Sylvain Weiller

Download latest version !

Many parameters (speed, size, seeing) are available. Speed can be adjusted either manually or automatically with a laser beam.
You can also place an image anywhere around which moves at the same speed as the guiding star.

On the right autoguiding is done with PHP guiding with a webcam and a serial link PC-mount.
The result shown at the top of this page are done with
a defiltered Canon 300D, Orion 80ED with reduced aperture, Neutral filters (2x for 30s and 2x+4x for 2 min exposures), 100 ISO !
4x 30s pictures coregistered in Registax5 and 7x 2min pictures coregistered (with large "sky" rotation) with DSS (Deep Sky Stacker)


The complete setup occupies 2 rooms because the refractor is at about 5m from the PC screens !

User distances can vary from about 1.5m to 10 meters !
Keep in mind that for the same screen size, the further the mount is, the shorter the working time !
(with above distances and a 17" 1024*768 screen it goes from about 30min to about 5min)

It appears now - thanks to an interesting question of Tim I. - that to test the easiest way the AD periodic errors, the polar axis of the mount should be vertical, pointing towards the zenith
because then the AD motor creates a pure horizontal aiming trajectory.
PHP guiding has no DEC corrections to do to follow the dot on the screen and calculations are optimized !
If a vertical direction is not possible with a type of mount then the nearest to it is best ...
(See below 3D pictures posted in free wieving L-R-L and also anaglyph)

Menus and explanations

Note : texts replaced by easy to use icons in new version Hints giving the same info as below ...

1) Quit SGE
2) Protect the star position on the screen from any unwanted clicks ! Commands do operate still. Use deprotect if you want to change the position of the star manually.
3) draw a fixed pattern on screen for setup purposes. Does not restart the star in V version.
4) clears screen
5) Parameters can be set on this window
6) Star size can be choosen either large 3*3 (A & C) or punctual (B & D)
7) With the force set in parameters, you can mimic a fluctuent star
8) With a left click you can add a small star cluster (A). With a right click... a "real" DSO like the given Orion's images of different sizes and intensities, or you own BMPs ! Move it also around with a right click.
9) If you don't have 2 different screens, you can split the single one horizontally to allow space for your guiding software (See E)
11) Instructions will be found there
12) Presentation of authors, version and copyrights
13 ) Hit this button to start the sideral movement of the emulated star
14) Stops star movement
15) Restarts star movement from where it had been placed previously
16) Fix the position of future restarts
17) Hit this button when the laser beams touches the left physical screen limit (G) or the left laser start line (J)*
18) Hit this button when the laser beams touches the right laser finished line (K)*
19) Hit this button when the laser beams touches the right physical screen limit (G') - to far to be shown...
20) Left click moves the star leftwards of 1 pixel, right click moves the star leftwards of 10 pixels
21) Left click moves the star rightwards of 1 pixel, right click moves the star rightwards of 10 pixels
22) Left click moves the star upwards of 1 pixel, right click moves the star upwards of 10 pixels
23) Left click moves the star downwards of 1 pixel, right click moves the star downwards of 10 pixels

Only on new version (with icon menu)
24) Left click reduce the speed of the star (1ms delay), right click reduce the speed of the star (10ms delay)
25) Left click accelerate the speed of the star (1ms less delay), right click accelerate the speed of the star (10ms less delay)
26) Change in ms of the star delay, click on number to reset to zero.

F) center of screen or split screen. To be pointed as reference by the instrument at setup.
H) position of star after a mouse click I) Orbit of the star visible

* will also start the star movement.


Example of single images without autoguiding and after a good training with PHPGuiding...

First attempt to do a P.E. study indoors !
Pc screen at about 5 metters from LXD-75 mount,
300mm refractor, Toucam pro, Astrosnap, PEAS (you can choose english !)

Download latest Version (with DSO, Moon, Sun Brightness adjustments)

Either with the new SGE-Installer
(and copy new Sun and Moon bitmaps from the zip below into DSO floder, but in that case
they maybe stored by Windows only in C:\Users\YourName\AppData\Local\VirtualStore\Program Files (x86)\SGE\dso\Sun.bmp etc.)

or download SGE.zip,
extract to the same dir C:\Users\YourName\ then use the software there or copy (admin. rights) all content of SGE folder into a new folder like C:\Program Files (x86)\SGE\

Hint :
If you can use 2 different PCs (one exclusiveley for SGE, one for the other program) raise SGE priority to hign (or even real time) with Windows task manager, fluidity will much improve at high star speed !

To do work for the next versions :
New star formula (3*3) with subpixel progressive gravity center move for better fluidity at low distance from screen
Definition of starting and ending points,
Elliptical orbite to be even closer to reality,
Setting task priority from inside SGE.

***ATTENTION : Take care as you may find yourself, from now on, doing autoguiding setups during much more nights than before ...
I will not be responsible for your companion anger :)

2009/09/17 new hints !

As you can see here this is the setup !

Computers : one PC for SGE and one (EEEPC-1000H with Ascom5a+LXD75 drivers for PHP-Guiding) are not shown.
To reach easily focus on the Canon EOS, a 90° miroir has been used behing the Orion 80ED.
The refractor for guiding is a cheap 70/300mm, the webcam is a BW modified VestaPro.

As you can see, the Orion image has been positioned rather far from the guiding star (above and right)
in order to be able to center them both on their respective cameras as there is a strong parallax between the two refractors at 4m distance !!

The 40D in live view mode allows easy framing/focusing on the PC screen !

I found that a rotating polarizing filter is the best way to attenuate at will the - also polarized - light from the PC screen
to allow for exposures of 1 min or more on the Canon 40D at 100 ISO without overexposure !


© 2009 Sylvain Weiller. All right reserved