Photographs taken at the JATObservatory were obtained using various cameras. Each of the cameras has pros and cons, such as cost, quality, sensitivity or ease of use.
Most high resolution cameras designed for astrophotography generally use a CCD chip instead of a CMOS chip and electronic cooling known as Peltier Cooling. The cooler the operational temperature of CCD chip the better the Signal-to-Noise ratio (refered to as dark noise or dark current). But that doesn't mean a low cost cameras without a CCD chip or cooling can't produce high quality images. Inexpensive webcams and mid to low end consumer grade digital cameras have produced stunning images. Some of these images are of better quality than the images by professional observatories just 5 years ago.
CCD and CMOS chips in camera have signal to noise characteristics. Photon-shot noise, dark current and chip reading are all sources of noise. Peltier cooled cameras have greatly reduced thermal noise. You have a probably experienced dark noise if you have a standard digital camera and have ever taken a picture in a dark room without using a flash. If there were red, blue and green spots that looked like Christmas lights in your photo, that is dark noise.
The camera listed below are the cameras at the observatory. There are currently no film cameras in use.
The SBIG ST-2000XM camera is a quality Peltier Cooled astronomy CCD camera. The ST-2000XM uses a dual CCD chip. The main chip is used for imaging and the 2nd chip is used to autoguide the telescope. The ST-2000 version used by the observatory is a the black and white version and not the one shot color version. The B&W version was chosen of the color version because of the options to use filter with the camera. In order for the B&W version to take color pictures a filter wheel (CFW10A) is attached to the camera. The filter wheel has red, green and blue and other filters. The filter wheel is controlled by the CCD camera's imaging software. The software will automatically rotate the filter wheel, so a minimum of 3 exposures will be taken for each object photographed. In some cases the as many images of each color may be taken for extremely faint objects. The individual red, blue and green images are then to combined during an offline image processing procedure to create a composite color image of the nebula, galaxy or planet. To help the ST-2000XM guide, an active optics device is sometimes used. The AO-7 uses a tip/tilt mirror which adjusts the image seen by the telescope allowing guiding at 10 frames a second on a 10th magnitude star with a 10 inch (25cm) telescope!
The SBIG ST-402ME is a small light weight camera that is occasionally used for imaging, but it's primary duty is as an autoguiding camera. The ST-402ME uses a single CCD chip and has an optional internal filter wheel that contains fixed Red, Blue, Green and Clear parfocal filters, which allow it to capture color images. While the camera is Peltier Cooled its cooler is not as efficient as the cooler on the ST-200XM. When attached to the SV-102a the FOV on the ST-402ME is very close to the FOV of the ST-2000M when it is attached the 10" LX200GPS OTA @ F6.3.
The main chip is used for imaging and the 2nd chip is used to autoguide the telescope. The ST-2000 version used by the observatory is a the black and white version and not the one shot color version. The B&W version was chosen of the color version because of the options to use filter with the camera. In order for the B&W version to take color pictures a filter wheel (CFW10A) is attached to the camera. The filter wheel has red, green and blue and other filters. The filter wheel is controlled by the CCD camera's imaging software. The software will automatically rotate the filter wheel, so a minimum of 3 exposures will be taken for each object photographed. In some cases the as many images of each color may be taken for extremely faint objects. The individual red, blue and green images are then to combined during an offline image processing procedure to create a composite color image of the nebula, galaxy or planet. To help the ST-2000XM guide, an active optics device is sometimes used. The AO-7 uses a tip/tilt mirror which adjusts the image seen by the telescope allowing guiding at 10 frames a second on a 10th magnitude star with a 10 inch (25cm) telescope!
The SBIG All Sky & Meteor Cam is a specialty camera. The All Sky Cam was designed to look straight up at the night sky in order to capture meteors entering the atmosphere or passing satellites. The camera is based on the monochrome SBIG ST-402ME. The difference is there is a 2.6mm wide angle lens attached and the camera is enclosed within a weather proof lockable metal case. The camera uses a 12 volt DC power supply that is also enclosed within the case, but it is feed by a user supplied standard AC power. It also includes a pair of IRCON USB extenders which allow operation up to 150ft from the host computer. The software enables automatic captures of moving illuminated objects based on parameters to defined by the user. The camera can be ordered with a light pollution filter if installation will be in a light polluted area.
The Canon camera used at the observatory are standard off the shelf digital camera. They are digital SLR (Single Lens Reflex), cameras ranging from 6.3 to 18 mega pixels. The DSLRs are attached to the telescopes using an adapter known as a T-Mount. The T-Mount allows the telescope to function as the camera's lens. The benefits of using a standard digital camera is ease of use. No filter wheel is required to obtain color images as with the other systems described above. And because the camera is a SLR, focusing can be done in real time without having to download images to the PC to see if the telescope is focused correctly as with astrophotography cameras. This drastically speeds up setup time. DSLR Focus is PC controlled utility that can rapidly download images via the USB port to the PC and can be used to aid focusing. (Although the DSLR Focus utility downloads images to the PC it is still far faster than the method used by the Meade older 416XT.) The DLSRs is mainly used when imaging the Sun and moon. Warning never point any optical device at the Sun without using an approved solar filter! Doing so can result in permanent eye damage!
Another benefit of the DSLR is that standard 35mm type lenses can be attached to the camera. This also allows the DSLR to be used as a wide angle camera. The camera can be mounted on a standard tripod and a wide angle lens such as the Zenitar-M 16mm can be used to photograph the sky. The DSLR can also be piggy backed on the OTA of the LX200GPS. In this configuration a Rubinar 300mm lens is mounted to the 10D (the lens is configured for manual mode when used for astrophotography). Both the telescope or standard lens configuration of the digital camera are capable of producing high resolution astronomy images.
The cons of the DSLR as an astrophotography camera is the CCD chip is not cooled as are most other special purpose astronomy cameras. This limits the effective duration of the exposures (cooler CCD chips provide better results). To get around this multiple short duration exposures are taken and then "stacked". In same cases this will give similar results as a long duration exposure. For exposures longer the 30 seconds the DSLR requires that a remote controlled shutter device know as a intervalometer is used. The observatory uses Canon's TC-80N3 which allows the duration, number and delay between exposures to be set by the user. The drawback the TC-80N3 is it is a manually operated device. Using it is not an option on cold winter nights. Instead the DSLR is connected to a specially modified parallel port ot USB cable and controlled via software such as Canon's EOS Utility. This allows the camera to be remotely controlled via any computer on the local network during long exposures. The EOS Utility adds much more remote functionality than just the TC-80N3.
It should be noted that the Canon cameras used at the observatory do not use a full frame sensor, i.e. the sensor does not see the full area of the lens as a 35mm camera would using the same lens. This has the unfortunate effect of making the focal length marked on the lens incorrect. When 35mm lens is used on a non-full frame sensor on the focal length marked on the lens must be multiplied by 1.6. In the case of a wide angle lens such as the Zenitar-M 16mm above, that lens is really a 25.6mm lens when used on a non-full frame camera. As you can see this can make finding a fully auto ,wide angle lens, that would allow a non-full frame DSLR to take photos in the 16-19mm range rather expensive.
The Starlight Express system is the MX7-C. The MXC-7 is purpose built astrophotography CCD camera. It is what is known as a One-shot color camera. That means it doesn't require a filter wheel in order the capture color images. For astrophotography this cuts down the time required to image in color. This is similar to a standard digital camera with the difference being the CCD is much more sensitive than the CCD in the DSLRs. Another difference is because it was designed specifically for astrophotography the MX7-C is electronically cooled similar the Meade 416XT CCD camera. This allows for much longer duration exposures than you could achieve with the 10D. The constant regulated Peltier Cooling circuitry, cools the MX7-C to approximately -20 degrees C. The MX7-C is available in either a parallel connection or a USB connection. The USB option was used because of the higher image download speed offered by the USB connection.
The MX7-C also has the added benefit of functioning as an autoguider. Autoguiding can also be done at the same time as imaging (although this does result in lower imaging resolution). The auto guiding is accomplished by use of an interface box called the STAR2000. The STAR2000 connects between the serial port of the PC and autoguider port of the telescope. The STAR2000 will allow automatic correction inputs to the telescope at 1 second intervals when a magnitude 11 (rather dim) star within the imaging field of view is used as the guide star. This does a remarkable job of keeping the telescope accurately pointed at the intended target.
The Meade LPI is also a purpose built, one shot color, astrophotography camera and uses a USB interface. But unlike other purpose built astro-cameras the LPI is a CMOS based camera not a CCD based one. This limits the LPI to mainly bright objects. The LPI fits in the a standard 1/4 inch eyepiece and supports up to a 16 second exposure. For a CMOS based camera the LPI actually does a very good job on the Moon, and planets. It can also image some bright deep space objects such as M42. With a solar filter in place of course the LPI can also be used to image the Sun.
The LPI software allows the user to combine and stack individual images in order to bring out details of fainter objects as well as use the LPI as a autoguider when the telescope is configured in polar mode. Windows will recognized the LPI as a standard imaging device. Because of this the LPI can be used by 3rd party software.
The Meade DSI There are 2 versions of this camera, a one shot color and the Pro version. The Pro version uses a monochrome CCD chip. It is more sensitive than the color version, The Pro version is now used mostly as a guide camera. As with the LPI the DSI's software allows the user to combine and stack images. Both the color and Pro version are used at the observatory.
The Mallincam Hyper
This camera is a very sensitive color video camera. It uses a Class 1 CCD sensor
Peltier Cooled so
it has low low dark current noise and a very good signal to noise ratio.
Like the rest of the equipment in the observatory the camera is controlled
remotely. An RS-485 to RS232 converter is used to connect it to the PC. This allows the camera's
function to be remotely controlled except for the cooling and image integration,
(those functions are controlled by toggle switches on the side of the camera).
The video output from the camera is either in the form of S-Video or composite
video via a BNC connector. In order to get the video from the camera the
S-video output is routed to a
Singbox AV. This allows access to the
from any computer that has a connection to the observatory
network. Still images are captured using a external program. The
images can then be captured at user defined intervals in BMP
format. The composite video output is connected to a
The GStar-Ex This is similar the Mallincam except it is Black & White. It is connected the Slingbox AV unit via a RCA composite video cable. The main purpose of the GStar-Ex camera is to monitor the position of the dome's slit. The camera allows the remote user to see the exactly where the scope is pointing.
The Meade 416XT system is a digital camera designed specifically for astrophotography. The 416XT camera utilizes a Peltier cooled CCD chip to capture the low level light that radiates from deep space objects. In order for the CCD camera to acquire color images a Meade 616 Color Filter Wheel is attached to the front of CCD imager. (This camera is no longer used)
The Phillips ToUcam is Webcam that uses a CCD chip for imaging and connects to the PC via the USB interface. This allows the ToUcam to image fainter objects than CMOS based cameras. The factory lens has been removed and replaced with an adapter so the ToUcam can be attached to a standard 1/4 inch eyepiece. It takes color images and can be used to autoguide when coupled with 3rd party software. The ToUcam also lends itself to modifications that allow it to take longer exposures than the unmodified camera from the factory. (This camera is no longer used)
The Orion Video Eyepiece is a CMOS based camera. The main drawback of the the Orion Video Eyepiece is it requires connection to a device capable of displaying signals from it 's composite video RCA jacks. it was designed to be used with a TV or a video monitor So unless your computer has a video capture card you will have to use some other interface to get the images into the PC. I use an X-10 interface which plugs into the USB port of the PC. The RCA video plug from the Orion Video Eyepiece then plugs into the X-10. Another draw back of the Orion unit is it requires a 9 volt DC external power supply. The plus side is when connected to the X-10 interface Windows will recognize it as standard imaging device. (This camera is no longer used)
Autoguiding: During long exposures, minor telescope misalignment and inherent tracking errors will have an adverse affect on the quality of the image. To over come this the telescope must be guided to insure it stays accurately pointed at the object being photographed. While the telescope can be guided manually, this can be a tedious chore. A lapse in concentration by the observer can lead to a blurred image. The most efficient way to guide a scope is by letting a computer perform the task. This is known as "autoguiding". To perform autoguiding, a CCD camera is connect to the telescope and linked to the Autoguide or RS-232 port on the main telescope. When the guide star begins to move away from the center of the autoguider's CCD chip, because of either tracking errors or misalignment, the autoguider sends position information to the main telescopes microprocessor. The computer in the main telescope will use that information to command the drive motors to make periodic corrections to keep the guide star located within the center of the autoguider's CCD chip. This in turn keeps the main telescope's CCD imaging camera accurately pointed at the object being photographed. This time lapse image of the asteroid Vesta required the telescope to track a nearby star for the 8 hours requires to acquire the image. During that time the background star as well as the asteroid moved from one side of the sky to the other. Without autoguiding this image would have required a human being sit at the telescope making corrections to its pointing for 8 straight hours!
The observatory can perform autoguiding using a number of different methods. One method uses the SBIG Active Optics AO-7 system attached to the ST-2000XM described above. The 2 benefits of the AO-7 system is no setup of a 2nd CCD camera is required and the speed at which the AO-7's active optics can made adjustments. This results in images with nice round stars. The downside is the AO-7 system limits the area of the sky the 10" LX200GPS scope can image when it's attached. This is because of its size it won't clear the telescope's base, so imaging near Polaris with the AO7 attached is not possible. The ST-2000XM can autoguide without the AO7 attached, This removes the near Polaris imaging restriction but the images are not
The 2nd method known as "off-axis" guiding, employs a device called an "off-axis guider" which contains a prism to split the image the telescope is receiving. The off-axis guider is placed between the focuser and the main CCD camera. Most of the image (approx 85~90%) is directed to the CCD camera. The remaining 10~15% is directed to either a 2nd CCD camera or an eyepiece. If a 2nd CCD camera is used the computer will make the adjustments to the telescope's pointing. If an eyepiece is connected the pointing adjustments must be manually carried out by the observer. There are a few downsides to off-axis guiding. One a 2nd CCD camera is required which raises the cost of imaging. Second a bright star is generally required to achieve good guide results. And third the guide star must be within the same FOV as the object being imaged.
The last method uses a 2nd telescope mounted or "piggy-backed" on the main telescope. Like off-axis guiding a 2nd CCD camera or an eyepiece is required to be attached to the piggy-backed telescope. The big difference here is the guiding is performed by a guide star within the FOV of the piggy-backed scope. For piggy-backed guiding a Short Tube 80mm refractor telescope that is "piggy-backed" on the main Optical Tube Assembly (OTA). A mount between the main OTA and the smaller ST80 guide scope allows precise alignment to a guider star. The main benefit of piggy-backed guiding is the piggy-backed guider scope can be positioned to use a guide star elsewhere in the sky when one is not within the FOV of the main scope and the object being imaged. For this method the ST-402ME or Meade Deep Space Imager is used as the guide camera.
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