G3 CCD Camera - Moravian Instruments

G3 CCD Camera - Moravian Instruments
G3 CCD Camera
User's Guide
Version 3.1
Modified on March 11th, 2016
All information furnished by Moravian Instruments is believed to be
accurate. Moravian Instruments reserves the right to change any information
contained herein without notice.
G3 CCD cameras are not authorized for and should not be used within Life
Support Systems without the specific written consent of the Moravian
Instruments. Product warranty is limited to repair or replacement of
defective components and does not cover injury or property or other
consequential damages.
Copyright © 2000-2016, Moravian Instruments
Moravian Instruments
Masarykova 1148
763 02 Zlín
Czech Republic
tel./fax: +420 577 107 171
www:
http://www.gxccd.com/
e-mail: [email protected]
Table of Contents
Introduction...............................................................................................4
G3 Camera Overview...............................................................................6
CCD and Camera Electronics...................................................................9
CCD Chip..........................................................................................12
Model G3-1000...........................................................................12
Model G3-11000.........................................................................13
Model G3-11000C.......................................................................13
Model G3-16200.........................................................................13
Model G3-16200C.......................................................................14
Camera Electronics...........................................................................14
Model G3-1000...........................................................................15
Model G3-11000.........................................................................15
Model G3-16200.........................................................................15
Cooling and power supply......................................................................16
Power Supply....................................................................................17
Mechanical Specifications......................................................................19
Camera head dimensions..................................................................20
Telescope adapters............................................................................22
Camera Maintenance..............................................................................24
Desiccant exchange...........................................................................24
Changing the silica-gel................................................................25
Changing Filters................................................................................27
Changing the Whole Filter Wheel....................................................29
Changing the Telescope Adapter......................................................30
Power Supply Fuse............................................................................30
Introduction
Thank you for choosing the Moravian Instruments CCD camera. G3 series of
CCD cameras were developed for imaging under extremely low-light
conditions in astronomy, microscopy and similar areas. Design of this series
inherits from G2 cameras, with which they share precise electronics providing
uniform frames without artifacts and extremely low read noise limited only by
CCD detector itself. Also the robust construction, rich software support and
easy manipulation are the same. However, G3 camera head is large enough to
contain detector up to 24×36 mm.
G3 cameras can contain also filter wheel with 5 positions for 2 inch (50 mm)
diameter filters.
G3 cameras can be equipped with external filter wheel, but it is not possible to
combine internal and external wheels on single camera. G3 camera mus be
made without internal filter wheel to be compatible with external filter wheels.
The G3 cameras are designed to work in cooperation with a host Personal
Computer (PC). As opposite to digital still cameras, which are operated
independently on the computer, the scientific slow-scan, cooled cameras
usually require computer for operation control, image download, processing
and storage etc. To operate the camera, you need a computer which:
1.
Is compatible with a PC standard.
2.
Runs a modern 32 or 64-bit Windows operating system.
Drivers for 32-bit and 64-bit Linux systems are also provided, but
camera control and image processing software, supplied with the
camera, requires Windows operating system.
3.
Provides at last one free USB port.
G3 and G4 cameras are designed to operate with USB 2.0 high-speed
(480 Mbps) hosts. Although they are fully backward compatible with
USB 1.1 full-speed (12 Mbps) hosts, image download time can be
somewhat longer if USB 1.1 connection is used.
4
A simple and cheap device called USB hub can expand number of
available USB port. Typical USB hub occupies one computer USB
port and offers four free ports. Make sure the USB hub is USB 2.0
high-speed compatible.
But keep on mind that if more USB devices connected to one hub need
to communicate with a host PC, USB hub shares its single up link line
to the host PC. Although G3 and G4 cameras can operate through a
USB hub, it can negatively affect the camera performance, like
download time etc. It is recommended to connect other USB devices
through USB hub (e.g. the mouse) and to provide the camera a direct
USB connection to the host PC.
4.
Alternatively it is possible to use the Gx Camera Ethernet Adapter.
This device can connect up to four Gx cameras of any type (not only
G3, but also G0, G1, G2 and G4) and offers 1 Gbps and 10/100 Mbps
Ethernet interface for direct connection to the host PC. Because the PC
then uses TCP/IP protocol to communicate with the cameras, it is
possible to insert e.g. WiFi bridge or other networking device to the
communication path.
The G3 cameras need an external power supply to operate. It is not possible to
run the camera from the power lines provided by the USB cable, which is
common for webcams or very simple imagers. G3 cameras integrate highly
efficient CCD chip cooling, shutter and possibly filter wheel, so their power
requirements significantly exceed USB line power capabilities. On the other
side separate power source eliminates problems with voltage drop on long USB
cables or with drawing of laptop batteries etc.
Also note the camera must be connected to some optical system (e.g. the
telescope) to capture images. The camera is designed for long exposures,
necessary to acquire the light from faint objects. If you plan to use the camera
with the telescope, make sure the whole telescope/mount setup is capable to
track the target object smoothly during the exposure.
5
G3 Camera Overview
G3 camera head is designed to be easily used with a set of accessories to fulfill
various observing needs. Camera head itself is manufactured in two different
variants:
●
Camera with internal filter wheel with 5 positions for 2” or D50 mm
filters.
●
Camera with control port for external filter wheel. This model allows
attachment of an external filter wheels with with 7 positions for 2” or
D50 mm filters.
The whole system comprises of various telescope adapters, which can be
attached to all variants of camera heads – without filter wheel, with internal
filter wheel or with external filter wheel.
Let us note that it is not possible to combine both internal and external filter
wheels. The external filter wheel reuses the control electronics, which stays idle
if the camera is not equipped with internal filter wheel. This solution eliminates
separate power and control cables for the external filter wheel, as it is attached
to the camera head. It also brings full software compatibility, as the software
does not distinguishes internal and external filter wheels, only the number of
available filters is different.
All telescope adapters, which preserve defined back focal distance (BFD –
typically bayonet adapters for photographic lenses but also the OAG adapter),
are designed for the external filter wheel BFD. If they are used on the camera
with internal filter wheel or without a filter wheel at all, it is necessary to use
spacers. Thin spacer compensates BFD difference between external and
internal filter wheel and thick spacer adds the thickness of the external filter
wheel housing to keep the BFD on camera without filter wheel.
6
Illustration 1: Schematic diagram of G3 camera system components
7
Components of G3 Camera system include:
1.
G3 camera head with internal filter wheel.
2.
G3 camera head without internal filter wheel, ready for attaching of
external filter wheel.
3.
G0 Guider camera.
4.
G1 Guider camera.
G0 and G1 cameras are completely independent devices with their
own USB connection to the host PC. They can be used on G2 OAG,
on standalone guiding telescope or for any other imaging purpose, like
Moon or planetary imaging etc.
Both G0 and G1 camera can share the Gx Camera Ethernet Adapter
with up to 3 other Gx cameras to be accessed over network.
5.
External filter wheel.
6.
Off-axis guider adapter with M68×1 thread.
7.
Thin spacer. Camera with internal filter wheel and this spacer has the
same back focal distance as camera with external filter wheel.
8.
Thick spacer. Camera without internal filter wheel and this spacer has
the same back focal distance as camera with external filter wheel.
9.
M68×1 thread adapter for large focusers.
10. Nikon bayonet adapter for Nikon compatible lenses.
11. Canon EOS bayonet adapter for Canon compatible lenses.
12. T-thread (M42×0.75) adapter.
13. 2-inch barrel adapter.
14. Gx Camera Ethernet Adapter allows connection of up to 4 Gx cameras
of any type on the one side and 1 Gbps Ethernet on the other side. This
adapter allows access to connected Gx cameras using routable TCP/IP
protocol over practically unlimited distance.
15. The whole system is controlled from a host PC.
8
CCD and Camera Electronics
G3 series of CCD cameras are manufactured with two kinds of OnSemi
(formerly Kodak) CCD detectors:
●
G3 cameras with OnSemi KAF Full Frame (FF) CCD
architecture. Almost all Full Frame CCD detector area is exposed to
light. This is why these detectors provide very high quantum
efficiency. FF CCD detectors, intended for research applications, are
not equipped with so-called Anti Blooming Gate (ABG – a gate,
which prohibits blooming of the charge to neighboring pixels when
image is over-exposed) to ensure linear response to light. FF CCD
detectors used for astrophotography are equipped with ABG to
eliminate disrupting blooming streaks within field of view.
Cameras with Full Frame detectors are suitable for scientific
applications, where linear response is necessary for photometric
applications in astronomy, microscopy etc. High quantum efficiency
could be used also for narrow-band imaging, where overexposure is a
rare exception, and for imaging of small objects without a bright star
in the field of view.
Illustration 2: “Full Frame” CCD schematic diagram
9
●
G3 cameras with OnSemi KAI Interline Transfer (IT)
architecture. There is a shielded column of pixels just beside each
column of active pixels on these detectors. The shielded columns are
called Vertical registers. One pulse moves charge from exposed pixels
to shielded pixels on the end of each exposure. The the charge is
moved from vertical registers to horizontal register and digitized in
the same way like in the case of Full Frame detectors. This mechanism
is also known as “electronic shuttering”, because it allows very short
exposures and also digitization of the image without mechanically
shielding of the detector from incoming light.
Also cameras with IT CCDs are equipped with mechanical shutter,
because electronic shutter does not allow dark-frame exposures,
necessary for proper image calibration etc.
The price for electronic shutter if lower quantum efficiency
(sensitivity) of IT detectors compared to FF ones. Also all IT detectors
are equipped with ABG, so they can acquire images of very bright
objects without charge blooming to neighboring pixels.
Illustration 3: “Interline Transfer” CCD schematic diagram
10
G3 camera models with FF CCD architecture:
Model
G3-1000
G3-16200
G3-16200C
CCD chip
KAF-1001E
KAF-16200
KAF-16200
Resolution
1024×1024
4540×3640
4540×3640
Pixel size
24×24 µm
6×6 µm
6×6 µm
CCD area
24.6×24.6 mm
27.2×21.8 mm
27.2×21.8 mm
ABG
No
Yes
Yes
Color mask
No
No
Yes
G3 camera models with IT CCD architecture:
Model
G3-11000
G3-11000C
CCD chip
KAI-11002
KAI-11002
Resolution
4032×2688
4032×2688
Pixel size
9×9 µm
9×9 µm
CCD area
36.3×24.2 mm
36.3×24.2 mm
ABG
Yes
Yes
Color mask
No
Yes
Cameras with “C” suffix contains CCD detector covered with so-called Bayer
mask. Color filters of three basic colors (red, green, blue) cover all pixels, so
every pixels detects only light of particular color.
11
These cameras are able to acquire color image in single exposure, without the
necessity to change color filters. On the other side color mask brings lower
sensitivity and limits the capability to perform exposures using narrow-band
filters etc.
Because each pixel is covered by one of three basic color filters, it is necessary
to compute (interpolate) remaining two colors for each pixel, which of course
limits resolution of color image. Imaging using color detectors is described in
the “Color images” chapter.
CCD Chip
Quantum efficiency (sensitivity) of CCD detectors used in G3 and G4 cameras
depends on the particular camera model.
Illustration 4: Quantum efficiency of CCD detectors used in G3
Inherent dark current of these detectors is quite low compared to other CCD
detectors, suitable for scientific applications, which results into very good
signal/noise ratio.
Model G3-1000
G3-01000 model uses 1 MPx OnSemi KAF-1001E Class 1 or 2 CCD chip.
Resolution
12
1024×1024 pixels
Pixel size
24×24 µm
Imaging area
24.6×24.6 mm
Full well capacity
Approx. 220 000 e-
Output node capacity
Approx. 650 000 e-
Dark current
17 e-/s/pixel at 0°C
Dark signal doubling
5.5 °C
Model G3-11000
G3-11000 uses 11 MPx CCD OnSemi KAI-11002 Class 1 or 2.
Resolution
4032×2688 pixels
Pixel size
9×9 µm
Imaging area
36,3×24,2 mm
Full well capacity
Approx. 60 000 e-
Dark current
12 e-/s/pixel at 0°C
Dark signal doubling
7 °C
ABG
>1000×
Model G3-11000C
G3-11000C uses 11 MPx CCD OnSemi KAI-11002 Class 1 or 2 with color
(Bayer) mask.
Model G3-16200
G3-16200 uses 16 MPx CCD OnSemi KAF-16200.
Resolution
4540×3640 pixels
Pixel size
6×6 µm
Imaging area
27.2×21.8 mm
Full well capacity
approx. 41 000 e-
Dark current
0,08 e-/s/pixel at 0°C
Dark signal doubling
5.7 °C
ABG
2800×
13
Model G3-16200C
G3-16200C uses 16 MPx CCD OnSemi KAF-16200 with color (Bayer) mask.
Camera Electronics
16-bit A/D converter with correlated double sampling ensures high dynamic
range and CCD chip-limited readout noise. Fast USB interface ensures image
download time within seconds.
Maximum length of single USB cable is 5 m. This length can be extended to
10 m by using single USB hub or active USB extender cable. Up to 5 hubs or
active extenders can be used in one connection.
Gx Camera Ethernet Adapter device allows connection of up to four Gx
cameras of any type through Ethernet interface and TCP/IP network. Because
TCP/IP protocol can be routed, the distance between camera and host PC can
be virtually unlimited.
ADC resolution
16 bits
Sampling method
Correlated double sampling
Read modes
Preview
Low-noise
Horizontal binning
1 to 4 pixels
Vertical binning
1 to 4 pixels
Sub-frame readout
Arbitrary sub-frame
Computer interface
USB 2.0 high-speed
USB 1.1 full-speed compatible
Binning can be combined independently on both axes.
Image download time and system read noise depends on the CCD chip used in
particular camera model.
14
Model G3-1000
Gain
3 e-/ADU (1×1 binning)
5 e-/ADU (other binnings)
System read noise
12 e- (Low noise)
15 e- (Preview)
Full frame download
2.0 s (Low noise)
1.7 s (Preview)
Model G3-11000
Gain
0.8 e-/ADU (1×1 binning)
1.6 e-/ADU (other binnings)
System read noise
11,5 e- (Low noise)
13 e- (Preview)
Full frame download
16.9 s (Low noise)
14.1 s (Preview)
Model G3-16200
Gain
0.6 e-/ADU (1×1 binning)
1.0 e-/ADU (other binnings)
System read noise
10 e- (Low noise)
11 e- (Preview)
Full frame download
24.5 s (Low noise)
18.8 s (Preview)
15
Cooling and power supply
Regulated two-stage thermo-electric cooling is capable to cool the CCD chip up
to 45 °C below ambient temperature. The Peltier hot side is cooled by a fans.
The CCD chip temperature is regulated with ±0.1 °C precision. High
temperature drop and precision regulation ensure very low dark current for long
exposures and allow image proper calibration.
The camera head contains two temperature sensors – the first sensor measures
directly the temperature of the CCD chip. The second one measures the
temperature of the air cooling the Peltier hot side.
The cooling performance depends on the environmental conditions and also on
the power supply. If the power supply voltage drops below 12 V, the maximum
temperature drop is lower.
CCD chip cooling
Thermoelectric (Peltier modules)
TEC modules
Two stages
Maximal ∆T
48 °C below ambient
Regulated ∆T
45 °C below ambient (~85% cooling)
Regulation precision
±0.1 °C
Hot side cooling
Forced air cooling (two fans)
Optional heat exchanger for liquid coolant
Maximum temperature difference between CCD and ambient air may exceed
45 °C when the cooling runs at 100% power. However, temperature cannot be
regulated in such case, camera has no room for lowering the CCD temperature
when the ambient temperature rises. The 45 °C temperature drop can be
achieved with cooling running at approx. 85% power, which provides enough
room for regulation.
16
Power Supply
The 12 V DC power supply enables camera operation from arbitrary power
source including batteries, wall adapters etc. Universal 100-240 V AC/5060 Hz, 60 W “brick” adapter is supplied with the camera. Although the camera
power consumption does not exceed 55 W, the 60 W power supply ensures
noise-free operation.
Camera head supply
12 V DC
Camera head power consumption 14 W without cooling
52 W maximum cooling
Adapter input voltage
100-240 V AC/50-60 Hz
Adapter output voltage
12 V DC/5 A
Adapter maximum power
60 W
Power supply connector
5.5 / 2.5 mm
1.
Power consumption is measured on the AC side of the supplied 12 V
AC/DC power supply. Camera consumes less energy from 12 V power
supply than state here.
2.
The camera contains its own power supplies inside, so it can be
powered by unregulated 12 V DC power source – the input voltage
can be anywhere between 10 and 14 V. However, some parameters
(like cooling efficiency) can degrade if the supply drops below 12 V.
3.
G3 camera measures its input voltage and provides it to the control
software. Input voltage is displayed in the Cooling tab of the CCD
Camera control tool in the SIPS. This feature is important especially if
you power the camera from batteries.
17
Illustration 5: 12 V DC/5 A power supply adapter for
G3 and G4 CCD Camera
Warning:
The power connector on the camera head uses center-plus pin. Although all
modern power supplies use this configuration, always make sure the polarity is
correct if you use own power source.
18
Mechanical Specifications
Compact and robust camera head measures only 154×154×65 mm (approx.
6×6×2.6 inches). The head is CNC-machined from high-quality aluminum and
black anodized. The head itself contains USB-B (device) connector and
12 V DC power plug, no other parts (CPU box, USB interface, etc.), except a
“brick” power supply, are necessary. Integrated mechanical shutter allows
streak-free image readout, as well as automatic dark frame exposures, which
are necessary for unattended, robotic setups. Integrated filter wheel contains
5 positions for standard 2-inch filter cells with M48×0.75 thread. There are
three M3 threaded holes around each filter position, which allow fixing of
filters without cells (only a glass) up to 51 mm diameter.
Mechanical shutter
Yes, blade shutter
Shortest exposure time
0.2 s
Longest exposure time
Limited by chip saturation only
Internal filter wheel
5 positions 2" threaded filter cells or glass filters up to
51 mm diameter
Head dimensions
154×154×65 mm (G3 without filter wheel)
154×154×77.5 mm (G3 with internal filter wheel)
Back focal distance
16,5 mm (G3 without filter wheel)
29 mm (G3 with internal filter wheel)
33.5 mm (G3 with external filter wheel)
Camera head weight
1.6 kg (G3 without filter wheel)
1.9 kg (G3 with internal filter wheel)
2.5 kg (G3 with “S” external filter wheel)
19
Camera head dimensions
Illustration 6: G3 camera head front view
20
Illustration 7: G3 camera with internal filter wheel side view
Illustration 8: G3 camera with external filter wheel side view
21
Telescope adapters
The G3 cameras are supplied with standard 2" barrel adapter by default, but the
user can choose any other adapter he/she prefers. Another adapters can be
ordered separately.
It is possible to choose among various telescope/lens adapters:
22
2" barrel adapter
Adapter for 2" focusers.
T-thread short
M42×0.75 mm inner thread,
7.5 mm thick.
T-thread with
55 mm BFD
M42×0.75 mm inner thread,
preserves 55 mm back focal
distance.
M48×0.75 thread
short
Adapter with inner thread
M48×0.75, 7.5mm thick
M48×0.75 thread
with 55 mm BFD
Adapter with inner thread
M48×0.75, preserves
55 mm back focal distance.
Pentax (Praktica)
lens adapter
M42×1 mm inner thread,
preserves 45.5 mm back
focal distance.
M68×1 thread
adapter
Adapter with inner thread
M68×1
Canon EOS lens
adapter
Standard Canon EOS
bayonet adapter.
Canon EOS clip lens
adapter
Canon EOS bayonet adapter
with the possibility to insert
“clip” filter. Can be used on
cameras with internal filter
wheel only.
Nikon F lens
adapter
Standard Nikon F bayonet
adapter.
T-thread (M42×0.75) adapter or M42×1 adapter cause vignetting when used
with G3-11000. Also common coma correctors (often equipped with T-thread)
cause vignetting with this large chip. Cameras with KAI-11000 CCD require
using of M68×1 adapter.
If the mounting standard defines also back focal distance (distance from adapter
front plane to detector), the particular adapter is constructed to preserve defined
distance (for instance T-thread defines back focal distance to 55 mm, but
certain distance is defined also for Pentax (Praktica) thread, for Canon EOS and
Nikon bayonets etc.).
Adapters are attached to the camera body using four M3 (3 mm metric) screws.
These threaded holes are placed on the corners of 44 mm square. Custom
adapters can be made upon request.
23
Camera Maintenance
The G3 camera is a precision optical and mechanical instrument, so it should be
handled with care. Camera should be protected from moisture and dust. Always
cover the telescope adapter when the camera is removed from the telescope or
put the whole camera into protective plastic bag.
Desiccant exchange
The G3 camera cooling is designed to be resistant to humidity inside the CCD
chamber. When the temperature decreases, the copper cold finger crosses
freezing point earlier than the CCD chip itself, so the water vapor inside the
CCD chamber freezes on the cold finger surface first. Although this mechanism
works very reliably in majority of cases, it has some limitations, especially
when the humidity level inside the CCD chamber is high or the chip is cooled
to very low temperatures.
This is why a cylindrical container, filled with silica-gel desiccant, is placed
inside the camera head. This cylindrical chamber is attached to the insulated
cooled CCD chamber itself.
Warning:
High level of moisture in the CCD chip chamber can cause camera malfunction
or even damage to the CCD chip. Even if the frost does not create on the
detector when the CCD is cooled below freezing point, the moisture can be still
present. It is necessary to keep the CCD chamber interior dry by the regular
exchange of the silica-gel. The frequency of necessary silica-gel exchanges
depends on the camera usage. If the camera is used regularly, it is necessary to
dry the CCD chamber every few months.
It is possible dry the wet silica-gel by baking it in the oven (not the microwave
one!) to dry it again. Dry the silica-gel for at last one or two hours at 120 °C.
Exceeding the 120 °C limit can damage the silica-gel and limit its ability to
absorb moisture.
24
Warning:
The 120 °C limit is valid for large-grain (3 to 5 mm) silica-gel, supplied with
revision 2 cameras. Silica-gel supplied with earlier revisions could be dried at
160 °C. But such high temperature can damage the large-grain silica-gel.
The silica-gel used in G3 cameras changes its color according to amount of
water absorbed – it is bright yellow or orange when it is dry and turns to
transparent without any color hue when it becomes wet.
Note:
The silica-gel ability to absorb moisture depends on the ambient temperature. If
the camera is located in the environment with below freezing point
temperatures, drying of the CCD cold chamber can take up to several days.
Illustration 9: Silica-gel container is accessible from the camera back side
Changing the silica-gel
The desiccant container design depends on the camera revision:
●
G3 cameras revision 1 have the container accessible from the back
side of the camera head. The slotted desiccant chamber cap can be
unscrewed e.g. by a coin. Pour out wet silica-gel and fill the chamber
with a dry one. The desiccant chamber can be filled with a hot silicagel without a danger of damaging of the container.
25
The desiccant container can be left open without the fear from
contamination of CCD chamber interior by dust. There is a very faint
stainless steel grid between the CCD chamber and the desiccant
container, so dust particles cannot enter the chamber itself. It is even
recommended to keep the desiccant container cap off for a couple of
hours when the camera is in the room with low humidity. This helps
drying the CCD chamber interior and prolongs the silica-gel exchange
interval.
●
G3 revision 2 cameras cameras supplied in 2016 and later are
equipped with a redesigned desiccant containers. New containers are
no longer a fixed part of the camera body with only a removable cap,
but the whole container can be unscrewed. The main advantage of this
design is the ability to exchange silica-gel without the necessity to
remove the camera from the telescope, which was necessary to be able
to pour-out the silica-gel and then to pour it in.
Silica-gel is held inside the container with a perforated cap. This cap is
also screwed into the container body, so it is easy to exchange the
silica-gel inside the container after it is worn out or damaged e.g. by
too high temperature etc.
The container itself does not contain any sealing (the sealing remains
attached to the CCD cold chamber inside the camera head), it consists
of aluminum parts only. So it is possible to heat the whole container to
desired temperature without risking of the temperature-induced sealing
damage.
This design also allows usage of some optional parts. First it is a
threaded hermetic cap, which allows sealing of the dried container
when it is not immediately attached to the camera head. And the
second one is an alternate (somewhat longer) desiccant container,
modified to be able to be screw in and tightened (as well as released
and screwed out) without any tool.
The sealed cap as well as the tool-less container are not supplied with
the camera, the are supplied only as optional accessory.
●
26
The G3 cameras with Enhanced Cooling are equipped with a bigger
heat sink and thus also thicker back shell. This requires usage of the
longer desiccant containers. Both container variants (the standard one
and also the tool-less variant) are supplied in two lengths. Shortened
containers for standard cameras and longer ones for Enhanced Cooling
cameras.
Illustration 10: Optional cap, containers with a slot and containers for toolless manipulation, versions for the standard and Enhanced Cooling cameras
Changing Filters
It is necessary to open the camera head to change filters or the whole filter
wheel of the G3 camera. Opening the head is quite simple – it is just necessary
to unscrew she eight bolts, which holds the camera head together.
Warning:
The blade shutter rotates 180° between individual snapshots. Camera cover
could be opened only when the shutter is closed. If for instance the camera is
unplugged from power adapter while exposing and the shutter remains open, it
can be damaged while removing the camera cover.
27
Illustration 11: Filters can be changed after opening the camera case front shell
After removing the screws carefully turn the camera head by the telescope
adapter upward. Gently pull the front part of the case. Notice there are two
cables, connecting the filter wheel motor and the filter position optical bar,
plugged into the electronics board. It is not necessary to unplug these cables to
change filters, but if you unplug them, take care to connect them again in the
proper orientation!
28
Illustration 12: Filter positions in the G3 filter wheel
Filter numbering is always engraved into the wheel, as illustrated by the image
above.
Changing the Whole Filter Wheel
The whole filter wheel can be changed at once. It is necessary to remove the
front part of the camera case the same way as in the case of changing filters.
The filter wheel can be removed when you unscrew the bolt on the center of the
front part of camera case. Take care not to damage the horseshoe-shaped
optical bar when replacing the filter wheel.
29
Changing the Telescope Adapter
The camera head contains bolt square. The telescope adapter is attached by four
bolts. If you want to change the adapter, simply unscrew these bolts and replace
the adapter with the new one.
Power Supply Fuse
The power supply inside the camera is protected against connecting of invertedpolarity power plug or against connecting of too-high DC voltage (above 15 V)
by a fuse. If such event happens and the cooling fans on the back side of the
camera do not work when the camera is connected to proper power supply,
return the camera to the service center for repair.
30
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