 IMPORTANT NOTICE! Never use a telescope or spotting scope to look at the Sun! Observing the Sun, even for the shortest fraction of a second, will cause irreversible damage to your eye as well as physical damage to the telescope or spotting scope itself. |
For users who wish to convert from Pictor 2.0 FITS Files to NOST Standard( PictorView
XT 6.0) FITS files, do the following:
* Open the 2.0 FITS file using PictorView XT.
* Select Save As from the File Menu
* Type in the same file name as the original (or another name if you wish
to keep the 2.0 file)
* If you selected the same name, the software will ask if you want to replace
the file. Select Yes.
* The new file will be written in the correct FITS standard. Note that PictorView2.0 will still be able to read this file.
| Section 22: Standalone Autoguiding with the Pictor 208/216XT |
Introduction
This chapter is designed to lead you through autoguiding step-by-step. Please
read through this chapter completely and follow each step in sequence; the
text will explain everything thatís required to successfully use
the Pictor.
The Basics
While you're using the Pictor, the display will show various letters and
values, and the
Pictor's button will light.The messages on the display and the lighting of the button convey information;
for example, to prompt you to press the button, or to indicate that the
Pictor is busy with a particular function.
The display and button are discussed on the following page.
The Display
The display can show two characters (letters or numbers). The characters
on the display are used to indicate what the Pictor is about to do or is
currently doing; for example, the letters FF indicate that the Pictor is
about to find and focus the image.
Numeric Displays
Sometimes the Pictor will give a status indication using numbers. In some
cases, such as when the Pictor is reporting brightness, a two digit number
is displayed ranging from 00 through 99. Figure (below) indicates a brightness
value of 35:
When the Pictor is showing a location in the image, the two digits will
indicate a position. In this case, the left digit is the horizontal
location(sometimes called the x direction) and the right digit is the vertical
position(sometimes called the y direction.) Throughout this manual the position
display will be shown as in figure below. Figure shows the position 2, 7:
(X)
 (Y)
X, Y Location Chart
When the display is used to enter time values, the Pictor will use a
two digit display. If the left digit is displayed as 0, a decimal point
will be assumed to be between the first and second digit. The example below
shows how Pictor will display the number 0.5:
If the Pictor is displaying the number 5, the left digit will be unlit,
as shown below:
The Button
The button on the Pictor controls the operation of the autoguider. The button
contains an LED in its center. When the LED is flashing, the Pictor is idle
and waiting for you to enter a command. When the button is solidly lit,
the camera is performing some operation. You can still press the button,
but it may take a few seconds for the Pictor to respond. The Pictor will
interrupt the operation.
You can enter one of three commands with the button depending on how long
you hold the button down. A brief depression of the button (less than 1second), is called a
short press.
Short presses are
used for selecting parameters within a mode, or to initiate a pending operation.
The right digit of the display is turned off when the Pictor recognizes
a
short press.
If you hold the button for 1 to 2 seconds, you will notice that the right
digit of the display is replaced with an underscore as shown below:
Releasing the button while the underscore is displayed in the right digit
is called a
medium press. The
medium press is used
to move between the different operating modes of the Pictor.
If you hold the button down for more than 2 seconds, the right digit will
display the dash, as shown below:
Releasing the button while the dash is displayed in the right digit is
called a
long press. The
long press is used to command
the Pictor back to its initial Find and Focus mode. No matter what the camera
is doing, the
long press will bring you back to the Pictor's
initial mode.
Getting Started
Once you've assembled the Pictor, you're ready to get started autoguiding.
This chapter is designed to guide you step-by-step through the autoguiding
process. If this is the first time you're using the Pictor, be sure to follow
each step in sequence.
1. Attach an
off-axis guider or guide scope
to your telescope.
2. Attach your camera to the off-axis guider or guide scope. An example
of a 35mm camera attached to an off-axis guider is displayed below.
3. Look through the camera window and frame the desired image.
4. Focus the image.
5. Insert an
eyepiece into the eyepiece holderand locate a bright star (known as
guide star) for the Pictor to
guide from. Try rotating the off-axis guider rather than moving the telescope
so that the framed picture in the camera is not disturbed.
6. Look through the camera window to make sure the picture in the camera
is still framed correctly.
7. Use the telescope to position the star in the center of the eyepiece.
Check back to make sure the picture in the camera is still framed correctly.
Continue cycling through steps 5-7 until both the framed image and the guide
star are centered.
Centering the star in the off-axis eyepiece is an important step; the entire
area seen through the off-axis eyepiece will not be seen by the Pictor.
The Pictor will see a very small section in the center of the off-axis eyepiece's
field of view.
The area seen by the Pictor will be seen in a small upper section of what
is seen by the primary eyepiece. For example, if an eyepiece 10mm in diameter
is used as the primary eyepiece, the
Pictor
will see the following area.
8. If this is the first time you have used the Pictor you will want to find
the rough focus point where the star will be focused on the Pictor's CCD
chip. A detailed description is given in Appendix D for finding Pictor focus
and creating a parfocal eyepiece for use in locating guide stars.
9. Insert the Pictor into the off-axis guider or guide scope. Attach the
power cable to the Pictor. Initially it will cycle the LED display and then
display PI, short for power up initialization. It will then display FF with
the button flashing. The FF display is the initial prompt for the Pictor.
It stands for Find and Focus.
You can get to this prompt from any mode the Pictor is in by entering a
long press.
10. Cover your telescope with its dust cap and enter a
medium press.The Pictor will display dr (dark ready) indicating it is ready to
make a dark reference exposure. A
medium press will cause
the Pictor to take a dark frame. The Pictor will display df while exposing
the dark frame. A
short or
long press will abort
this operation.
The Pictor will make a reference exposure with the completely darkened CCD
chip. This reference frame will be used while guiding to completely calibrate
the star images for maximum sensitivity. If you are guiding a bright star,
this step may be skipped. When the dark frame is completed, the FF prompt
will appear again. Uncover your telescope.
11. Press the button for a
short press. The Pictor will cycle
through the sequence of displays br, vv, at, and xy. The prompts are describing
the brightness of the star that the CCD chip is seeing. br is short for
brightness, and vv is the brightness of the star on a scale from 00 to 99.The at display precedes the location of the star on the at display shown
as xy. If your camera shows br, 22, at, 55, it is telling you that you have
a moderately bright star in the very center of the display.
12. Loosen the set screw on your guider and slide the Pictor in and out
of the draw tube a millimeter at a time. Observe how the brightness changes.
You will need to wait a few display cycles for the numbers to settle down
after you have touched the telescope. Locate the position where the brightness
is at its maximum, this is the point of perfect focus. Adjust the draw tube
clamp so you can easily find this location.
If you cannot get a brightness number larger than 10, your star is too dim.
You will need to customize the exposure setting in the Pictor to increase
the exposure time.
If your star brightness exceeds 95, your star is too bright and is overexposing the CCD chip. You will need to customize the exposure setting in
the Pictor to decrease the exposure time.
13. While the Pictor is cycling through the brightness/location displays,
enter a
medium press. The Pictor will display CA short for
calibration. During calibration the Pictor will move the telescope to determine
the guiding speeds of your telescope. The display will show you what is
happening. The following messages will appear during calibration:
FS Find Star - The Pictor is locating the brightest star in
the display field.
rt Right - The Pictor is moving your scope to the right.
LF Left - The Pictor is moving your scope to the left.
UP Up - The Pictor is moving your scope up.
dn Down - The Pictor is moving your scope down.
When the Pictor has completed calibrating your telescope, you will see the
prompt gd, short for guide. If calibration fails, the display will show
Er, short for error. A
short press will clear the error and
return you to the FF display. Calibration can fail if you have forgotten
to connect the cable from the Pictor to the CCD input of your telescope.
Additionally, calibration may fail if the star was not centered, or the
calibration moves were too small or too large.
If calibration fails, remove the Pictor from the guider and insert a 10mm eyepiece in its place. Re-center the guide star. Remove the eyepiece and
re-insert the Pictor. Attempt to calibrate again. If calibration fails again,
you may need to customize the calibration times. When calibration is complete,
gd will be displayed.
14. You are now ready to begin autoguiding. From the gd display enter a
short press. The display will go blank for several seconds.
This dead time allows you time to trigger the shutter of your camera and
let the vibration dampen before the guider begins to track. The default
delay is 5 seconds. You can change this value.
While the Pictor is guiding it will cycle through the following displays:
gb, vv, gc and xy. The gb stands for guide brightness, the next display
will be the brightness of the guide star on scale of 00 to 99. The gc display
stands for guide correction, it is followed by an xy display that gives
the magnitude of the x and y corrections. On an 8" f10 telescope these
numbers are approximately arc seconds.
Watching this display will give you an indication of how well the Pictor
is guiding. If the Pictor loses the guide star, it will display . This can
occur if the scope is jarred by the wind or careless movement. It can also
occur if the guide star is obscured by a passing cloud. The Pictor will
guide until you interrupt it, or it cannot find the guide star for 30 consecutive
seconds. If the Pictor quits guiding, gE (guiding error) is displayed.
If a cloud has passed in front of the object you are photographing causing
a guiding error, you may be able to cover your telescope and continue when
the cloud has passed. When gE is displayed, a
short press willcause the Pictor to attempt to resume guiding. Usually, you will want to
start another exposure when a guiding error has occurred. After a guiding
error a
medium or
long press will put the Pictor
into the FF mode.
During normal guiding, when you are finished exposing your image, release
the shutter then give the Pictor a
short, medium or
longpress. The Pictor will go into the FF mode at the end of the next
guide cycle.
Guiding Tips
Experienced astrophotographers have all but given up hand guiding pictures.
The Pictor can let you take longer, more precise pictures than you ever
thought possible. Here are some tips from the pros to help you get the best
results.
Let the Pictor Warm Up
The sensitivity of the Pictor is affected by its operating temperature.
The dark frame is used to eliminate background noise from the guide star's
image. Give the Pictor 10 to 15 minutes to reach its normal operating temperature
before you begin using it.
Recalibrate Only as Required
The Pictor remembers its last calibration setting, even if the power is
removed. If you use the same guiding setup night after night, you will only
need to recalibrate if you are guiding with a declination very different
from the one you calibrated for. For example, if you calibrate your Pictor
on a star at 30 degrees declination. You can probably guide quite well on
anything from -60 to +60 degrees declination.
Insert the Pictor Parallel to the RA Circles
While the Pictor will guide when inserted and calibrated at virtually any
orientation, make it a practice to always insert the Pictor so that it's
long axis is parallel to the RA motion of the stars. Doing this will achieve
several key advantages:
1) You can skip recalibration between shots.
2) You can easily center the guide star with the slow motion controls of
your telescope. If you don't put the Pictor in square, you will find that
either slow motion control will affect both the X and Y position of the
star.
Select Your Guide Star Carefully
The Pictor guides by repeatedly reading out a small portion of its image
and finding the brightest star in that field and centering it in the guiding
box, much the way a person manually guides with a reticle. If a star of
similar brightness drifts into the guide box, the Pictor will simply lock
on the brighter of the two stars. As a result, it may jump to the wrong
star (something you would never do). During the course of the exposure it
may jump back and forth between these stars several times. This will make
your picture look almost like a double exposure.
On an f/10 8" telescope, the guide box is 36 arc seconds square. To
be safe, a good guide star should have no bright companions within a 1 arc-minute radius.
Maintain a Good Guide Ratio
If you are using a separate guide scope, you should make sure that the focal
length of the guiding system is no less than one half of the focal length
of the photographic optical system.
If you are guiding CCD images with a Pictor we recommend that the guiding
ratio be at least equal to the focal length of imaging systems and preferably
twice that of the imaging system. This can be achieved with off axis systems
by inserting a Barlow lens into the off axis guide tube.
Be Sensitive to Conditions
While the auto guider can work through some difficult seeing and wind conditions,
the prudent astrophotographer knows when to put away the cameras and look
through the scope. If the seeing is poor and the stars are dancing in the
reticle or the wind is buffeting your scope. You may get Pictor to track,
but the resulting picture will be disappointing.
Making Customizations
Autoguiding with the Pictor can be customized to meet your individual needs.
The following areas can be customized:
- Exposure time for the CCD
- Duration of the delay before autoguiding
- Seeing compensation control
- Duration of movements during RA calibration
- Duration of movements during DEC calibration
To make customizations, complete the following steps.
1. If the Pictor is not already at the FF prompt, enter a
long press.
2. From the FF prompt, enter a
long press. Et, short for Exposure
time will appear on the display. Enter a
short press. The
current exposure time will appear. Each successive
short presswill cycle to the next exposure time. Exposure times vary from 0.1 seconds
to 25 seconds. When the desired exposure time is displayed, a
longpress will store your exposure time and return to the FF display.
A
medium press will move you to the next custom option. All
of your customizations are stored in permanent memory in the Pictor. The
settings will be remembered even if the Pictor is powered off and on again.
3. Every time you change the Exposure Time of the Pictor you must take anew dark frame before focusing, calibrating or guiding.
4. The next custom option displays dt, short for Delay Time. This value
specifies how long the Pictor will be between the
short press that
initiates guiding and the actual start of tracking. The delay gives you
time to release the shutter on your camera and to let vibrations settle
out of your telescope before the Pictor starts tracking. From the dt display
enter a
short press. The current delay time will appear. Each
successive
short press will cycle to the next delay time.
Delay times vary from 0.1 seconds to 25 seconds.
When the desired delay time is displayed, a
long press will
store your delay time and return to the FF display. A
medium presswill move you to the next custom option.
5. The next custom option displays Sc, short for Seeing compensation. This
controls how aggressively the
guider tries to correct small star movements. If seeing is poor and stars
are jumping around, it is best to enable seeing compensation. This will
keep the guider from chasing the seeing. If seeing is good, disable seeing
compensation for the best guiding performance. A
short press toggles
the seeing compensation on and off. If the Pictor displays 1, seeing compensation
is enabled. If the Pictor displays 0, seeing compensation is off. Entering
a
medium press will move you to the next custom option. Entering
a
long press will return to the FF prompt.
6. The next custom option displays Cr, short for Calibrate RA Time. This
value specifies how long to move the telescope in RA when calibrating. The
default value is 2 seconds. Ideally, the duration of movement in RA should
be enough to move the guide star 1/10th of the way across the CCD chip.
To determine this time, you can use the find and focus mode. While in find
and focus, manually press your slow motion controls. Time how long you must
hold down the motion control to get a one unit change on the XY display.
If your telescope only has an RA drive motor, be sure to read step 8 below,
as it contains information on how to disable the Dec calibration.
7. From the Cr display, enter a
short press. The current calibration
time will appear. Each successive
short press will cycle to
the next calibration time. Delay times vary from 0.1 seconds to 25 seconds.
When the desired calibration time is displayed, a
medium presswill store your calibration time and move you to the next custom option.
8. The next custom option displays Cd, short for Calibrate Declination Time.
This value specifies how long to move the telescope in Declination when
calibrating. The default value is 2 seconds. Ideally, the duration of movement
in DEC should be enough to move the guide star 1/10th of the way across
the CCD chip. To determine this time, you can use the find and focus mode.
While in find and focus, manually press your slow motion controls. Time
how long you must depress the control to get a one unit change on the XY
display. If you have a telescope with no Dec motor, enter 0 for the time;
this will disable the declination and allow the Pictor to guide in RA only.
9. From the Cd display, enter a
short press. The current calibration
time will appear. Each successive
short press will cycle to
the next calibration time. Calibration times vary from 0.1 seconds to 25seconds.
When the desired calibration time is displayed, a
medium or
long press will store your calibration time and return to
the FF display.
Restoring Factory Defaults
The Pictor is initialized and calibrated at the factory prior to being shipped
to you. During typical usage you should not normally need to recalibrate
your Pictor. If you should find it necessary to restore the factory defaults
to your Pictor, use the following procedure:
1. Apply power to your camera. Allow 5 minutes for the camera to idle while
its temperature stabilizes.
2. Cover the nose piece with an opaque lens cap to insure no light reaches
the CCD chip.
3. Remove power and re-apply power to reset the Pictor. After the LED display
cycles, the Pictor will display PI, short for power on initialization.
4. During the first second of the PI display, give the button a
shortpress. The Pictor will display FI, short for factory initialization.
5. The camera will work for a minute or so calibrating the CCD and restoring
the factory defaults. When initialization is complete the camera will display
the standard FF prompt.
6. After restoring factory defaults be sure to recalibrate the Pictor before
attempting to guide.
Pictor Mode Diagram
Go to Pictor Manual Appendices
Related Topics:
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