Astrel Instruments AST-8300-A User manual

Astrel Instruments AST-8300-A
Astrel Instruments
AST-8300-A
AUTOGUIDER MANUAL
rev A
Autoguider M nu l 1/14 rev A

Astrel Instruments AST-8300-A
Description
Lin_guider is a simple autoguider program for Linux operating system.It is designed to help
you get quality astroimages with long exposure. Once connected to your astro hardware
and properly configured, Lin_guider will compensate for the periodic tracking errors of your
telescope mount during the exposure time. This will help get images without blurred stars.
In addition, the program allows for the examination of the periodic error of your mount due
to the ability to write de iational plots. If you like taking planetary images, Lin_guider can
record ideo without compression in the AVI format.
Supported H rdw re
The ideo capture equipment and the link to your telescope mount are needed for the
operation of the autoguider. The autoguider ST-4 port is used for the connection to the
telescope mount.
Supported video h rdw re:
•QHY5 / 5II / 5LII
•QHY6
•Starlight Express (Lodestar, ...)
•ZWO ASI
•Generic ATIK
•DSI2PRO
•UVC compatible cams
•Philips webcams (PWC)
Supported webc m colour video form ts:
•YVU420, YUV420, JPEG, MJPEG, YUYV.
Webcams, that do not support any of these formats, are not yet supported.
Autoguider M nu l 2/14 rev A

Astrel Instruments AST-8300-A
Supported ctu tors (ST-4):
•QHY5 / 5II / 5LII
•QHY6
•Starligth Express (Lodestar, ...)
•ZWO ASI
•Generic Atik
•FTDI compatible
•GPIO interface
•GPUSB
•LPT interface
•NEXSTAR compatible
SETTING UP THE HARDWARE
Before starting to work with the program, make sure your ideoequipment and the mount
actuator are properly identified and operational.
Video h rdw re setup
From the menu, select 'Setup' -> 'Guider setup' and choose the 'Video Settings' tab.
Autoguider M nu l 3/14 rev A

Astrel Instruments AST-8300-A
It is necessary to specify the guider de ice you will work with. To do this, you should
choose it from the 'De ice' list. E ery time you change guider it is necessary to restart the
program for the connection to the specified de ice to occur.
The image from the ideo de ice must appear after the restart.
You could also need to specify the required frequency of frames per second (FPS) and the
size of the captured image. You should know that the exposure time of one frame is
calculated as 1/fps, i.e. if fps is set to 5 (fps = 5), the exposure time of one frame will be
1/5 = 200 milliseconds. This time doesn't account for the time required for the data transfer
and its post-processing. That's why real FPS is somewhat smaller, than the chosen one.
This difference doesn't influence substantially the guiding quality. You should test such
parameters, as 'Autogain', 'Gain', 'Expo' (if they are a ailable), on the image and watch
how it will change.
The 'BW' parameter makes the screen layout monochromatic for se eral graphics formats,
thus slightly decreasing the CPU usage.
The 'half fps' parameter makes the screen layout of e ery second frame. It affects only the
screen layout and decreases the CPU usage, all frames are objecti ely captured and
processed by the autoguider.
You can switch the 'use calibration' parameter on, if you are planning to calibrate the
camera with a dark frame.
Autoguider M nu l 4/14 rev A

Astrel Instruments AST-8300-A
Actu tor setup
Open 'Setup' -> 'Dri er setup' in the menu.
You should choose the de ice to work with from the 'de ice' dropdown list in the first place.
It is necessary to restart the program for the connection to the specified de ice to occur. If
all went right, the program would start without pulse dri er error messages.
If the launch is successful, connect the de ice to the autoguider port and check that the
guiding de ice functions properly.
That's all that is needed for autoguiders with the ST-4 output connector, while the other
parameters are used for interfacing directly to the mount (send an email to info@astrel-
instruments.com for support)
Autoguider M nu l 5/14 rev A

Astrel Instruments AST-8300-A
SETTING UP THE PHYSICAL PARAMETERS OF THE
GUIDER
From the menu, select 'Setup' -> 'Guider setup' and choose the 'Guider physical
parameters' tab.
When the ideo de ice and the telescope mount control de ice are connected and working
in the program, you must specify se eral parameters before the guiding can be started:
1. Aperture - the diameter of the guide objecti e, mm.
2. Focal length - the focal length of your guide, mm.
3. Matrix width - the amount of matrix pixels in horizontal direction, pixs.
4. Matrix height - the amount of matrix pixels in ertical direction, pixs.
5. Pixel width - the width of a pixel, um.
6. Pixel height - the height of a pixel, um.
!!! WARNING !!!
Some camera types, including webcams, allow for more than one resolution, for example
320x240 and 640x480. In this case you should set up the pixel size ery attenti ely. For
example, let's consider Philips SPC 900 NC camera, that has matrix with 640x480 pixels,
Autoguider M nu l 6/14 rev A

Astrel Instruments AST-8300-A
their size being 5.6x5.6 um. If we choose the default camera resolution of 640x480 in the
list of a ailable resolutions, the pixel size will be defined as 5.6x5.6 um, just as in the
camera specification. If we choose the resolution 320x240, the pixel size must be defined
as 11.2x11.2 um otherwise, the scale of all displayed and calculated alues will be wrong.
SETTING UP DITHERING AND REMOTE SERVER INFO
From the menu, select 'Setup' -> 'Settings'.
The application has an internal UDP ser er which can send guiding information to a
remote ser er. The IP and port can be specified along with the kind of data transmitted.
Moreo er here you can insert the 'Dithering range' in pixels. The software calculates the
time needed to get to the dithered position automatically but you can also add an extra
time using the 'Dithering rest timeout' in seconds. Dithering is automatically added by the
camera exposure scheduler at the end of e ery exposure.
'debug erbosity' and 'show Helper toolbar' are not implemented.
Autoguider M nu l 7/14 rev A

Astrel Instruments AST-8300-A
CALIBRATION
It is necessary to calibrate the autoguide before the start of the guiding. To do this you
ha e to complete at least one procedure - determination of the orientation of the celestial
reference frame in the image, taken from the camera. In addition, it is ad isable to perform
camera calibration with the dark frame.
Determin tion of the orient ion of the celesti l reference fr me
Direct your guide to the star you'd like to use for guiding. Make sure that the star isn't near
the image edge. Focus the image. Make sure that all mountings are tightened and the
wires do not hang freely.
Open 'Processing' -> 'Calibration' from the main menu. The Calibration window is opened
and can be mo ed if needed for monitoring the guide star.
Use the 'two axes' parameter to choose the two-axes or one-axis calibration. If the polar
axis is aligned, it is recommended to use the automatic mode of calibration - parameter
'auto mode'.
Autoguider M nu l 8/14 rev A

Astrel Instruments AST-8300-A
Autom tic c libr tion
Set time in seconds during which the drift along axes will be performed, making sure it is
long enough that the star mo es but always remains in the field. Use 'Find' to let the
software automatically choose a suitable star in the field or grab the green square and
drag it o er the guiding star you prefer. Make sure that the square follows the star. Press
the button 'Start'. The program will start to shift the star along one or two axes afterwards.
The result will be shown at the end of calibration. 'Status: DONE' will be shown in the case
of successful termination and the axes of reference will take the new position. In case of
an error, the window with an error message will be shown. If the polar axis is poorly
aligned, the automatic calibration may be terminated with an error. In this case, it is not
recommended to perform the photographic sur eying. Try to align the polar axis more
precisely.
M nu l c libr tion
If the automatic calibration doesn't suit for any reason or terminates with an error, you can
perform manual calibration. To do this, grab the green square by the mouse pointer and
drag it o er the guiding star.p Make sure that the square follows the star. Press the button
'Start'. Next use the mount control panel to shift the star position in RA+ direction and
press 'Stop'. If the two-axes mode is engaged, use the control panel to shift the star in the
DEC+ direction and press 'Stop' right after the end of the drift along RA. It is important to
understand that the longer the shift ector is, the more precise the determination of the
celestial coordinates' axes will be.
!!! WARNING !!!
It is recommended, that the square, following the star, doesn't touch the image edges
during the calibration.
Autoguider M nu l 9/14 rev A

Astrel Instruments AST-8300-A
C libr tion with the d rk fr me
In order to calibrate the camera with a dark frame, define the amount of frames to
accumulate in the field 'Frame count'. Co er the guide objecti e to pre ent light from
penetrating the camera and press the 'Start' button. At the end of the process the dark
frame will be formed, that will be substracted from e ery new frame, taken from the
camera, if the 'use calibration' parameter is chosen in the dialogue box of the guide setup.
GUIDING
You can start guiding after the celestial reference frame is determined.
Open 'Processing' -> 'Guiding' from the main menu and choose the 'Info/Configuration' tab.
Set the appropriate size of the square, following the star - 'Square size'. The square area
shouldn't be too small or too large, compared to the isible size of the star.
Choose the threshold algorithm, used to calculate the star position, 'Threshold alg.' The
alue 'Smart' is the more precise dynamic threshold calculation, compared to 'Auto'. The
alue 'Auto' is the dynamic threshold calculation. The alue 'No thresh.' - threshold
calculation is disabled.
You can also sa e guiding logs in text files. To do this, you ha e to set the checkbox 'sa e
Autoguider M nu l 10/14 rev A

Astrel Instruments AST-8300-A
drift' to checked and specify the file name in the 'Configuration block'. The file format is a
plain text with two columns with numbers - de iations along RA and DEC.
Next you ha e to specify parameters in the 'Control' tab. All parameters are defined
separately for each axis RA and DEC.
These parameters are:
1. Enable directions - enables or disables the use of calculated axis corrections. All is
enabled by default.
2. Accumulate frames - enables the a eraging of the coordinate alues, using N frames,
and the transfer of corrections at the end of the a eraging. Set to 1 by default, could be
changed when using ery long guiding focal lengths.
3. Proportional gain - is the coefficient of the proportional term in the PID control. May be
precalculated in the 'Info' block by default.
4. Integral gain - is the coefficient of the integral term in the PID control. Set to 0 by default.
5. Deri ati e gain - is the coefficient of the differential term in the PID control. Set to 0 by
default. Disabled in this ersion.
6. Maximum pulse - the maximum duration of the correction pulse. Limited by the specific
type of the actuator. Set to 5000 ms by default.
7. Minimum pulse - the minimum duration of the correction pulse. Set to 100 ms by default.
8. A g.frm. - disabled.
Autoguider M nu l 11/14 rev A

Astrel Instruments AST-8300-A
PID control coefficients adjustment should by performed empirically, using the specific
equipment and with full load. The idea of the adjustment is to find coefficients that don't
lead to 'under-guiding' (corrections are too slow) or 'o er-guiding' (sinusoidal oscillations
with increasing amplitude).
It is recommended to choose the range of alues from 10 to slightly more than the
recommended alue during the selection of the proportional coefficient (see 'Info' block)
and mo e through this region with the step of 10, looking attenti ely, how the result of the
guiding will change.
The selection of the integral coefficient is recommended to perform, if there is constant
impact in one direction. This coefficient will allow for the faster correction of the impact,
because it takes into account the pre ious guiding history.
The differential coefficient, as has been said abo e, is disabled at the moment.
!!! WARNING !!!
You should bear in mind during the selection of the coefficients, that their alues may ary
for different axes.
If the polar axis is well aligned, then the guiding alond the DEC axis can be performed
more rarely, e ery 2-4 frames. This will allow to a oid excessi e acti ity along the axis and
unnecessary ibrations. In addition, it is recommended to induce small imbalance
(o erweight) against the diurnal motion for the RA axis in order to mo e with constant
tension and remo e the play. It is recommended to induce a small shift of the polar axis
( for details see the drift method) from the ideal position for the DEC axis in order to make
a constant shift in one side and the guiding go in only one direction. This will allow to
reduce turbulence in the region of 0.
The alue of 'Maximum pulse' is usually chosen more or less equal to the period of the
working cycle (time between two successi e camera data captures). Usually there is no
Autoguider M nu l 12/14 rev A

Astrel Instruments AST-8300-A
need to change this alue. The 'Minimum pulse' alue is of more improtance. This
parameter defines the threshold of the correction duration. If the calculated correction is
more or equal to 'Minimum pulse', it is transfered to the mount, otherwise the correction is
discarded. If the threshold is too large, then the non-adjustable band of de iations around
the zero alue will be too wide and the quality of guiding will be too low. If the threshold is
too small, then the amount of corrections around the zero alue will be ery large, leading
to constant axis twitching in opposite directions and, as a consequence, badly controlled
antidamping. This fact is particularly important for high load setups with low mechanical
stiffness.
To start guiding and monitor guiding drift graph and statistics, select the 'Drift' tab.
Press 'Start' to begin guiding. The drift graph, current alues of corrections and statistics
are updated at e ery new image from the guider. When ready, you can close the guiding
application by pressing 'Done'. Of course guiding will continue in background and you can
get back to the 'Drift' tab by simply clicking on the autoguider icon on the camera desktop.
When guiding is no more required, press the 'Stop' button, the 'Drift' tab will be closed and
the main lin_guider window is showed.
GENERAL RECOMMENDATIONS
Autoguider M nu l 13/14 rev A

Astrel Instruments AST-8300-A
1. E erything on the photographic setup should be tightened: focusers, camera mounts,
mounting of the optical tubes to each other and to the telescope mount, mounting of the
mount head to the tripod/column, etc. The camera wires shouldn't dangle. The floppy
cable parts should be as short as possible.
2. It is recommened to induce small imbalance along RA in the direction opposite to the
diurnal rotation.
3. If the guiding star is too bright, It is recommended to adjust camera (if the hardware
allows) to eliminate o erluminance.
4. The change in camera parameters (Gain, FPS, etc.) requires the obligatory recalibration
of the camera with the dark frame, if it is used.
5. It is recommended to use the two-axes calibration method in the near-polar regions,
where the drift along RA is ery short during the calibration.
AUTHOR
Andrew Stepanenko (Galaxy Master) <galaxy[email protected]>
AST8300 CCD camera ersion porting: Andrea Ricciardi <[email protected]>
PROJECT PAGE
http://sourceforge.net/projects/linguider/
SUPPORT
<[email protected]>
Autoguider M nu l 14/14 rev A