The Self-Guiding Spectrograph is designed to be used with an ST-7E camera. Although it can also be used with an ST-8E, there is no advantage in bandwidth when using the larger format camera.  The spectrometer and ST-7/8 are coupled and mounted as a unit onto the telescope (See Figure 1).  The system is quite handy for collecting spectra since both the object of interest and the spectrometer entrance slit are simultaneously imaged onto the tracking CCD, allowing the object to be viewed and accurately placed onto the slit.  The slit is backlit by an LED during the setup so it clearly shows on the tracking CCD.  Once the object is maneuvered onto the slit, self guiding will then hold the object on the slit.

SBIG's Self-Guided Spectrograph Capabilities   

Measure Stellar Spectra:
     - Determine spectral class
     - Measure radial velocities

Measure Emission Nebula:
     - Determine spectral lines
     - Measure relative line strengths

Measure Galactic Objects:
     - Measure radial velocity (red shift) of brighter galaxies
     - Distinguish quasars from other objects

 Optical Specifications

General Specifications

SBIG Spectrograph shown attached to an ST-7E

2. ADAPTIVE OPTICS SYSTEM - SBIG’s AO-L HIGH SPEED GUIDER

AO-L with MOAG attached to an STL camera
equipped witwith the new 8 position 50mm filter wheel for the STL.

SBIG’s previous high speed guider, the AO-7, is unable to be used with the large CCDs of the STL cameras due to vignetting by the 50 mm diameter mirror it uses. At the 45 degree angle the mirror is used at it foreshortens to only 35 mm. It also had an issue with image rotation at large deflections which becomes serious for large CCDs, but is not a problem for the smaller CCDs of the ST series. For these reasons SBIG has designed a new Adaptive Optic device for high speed beam steering called the AO-L (Active Optic – Large Format). It does not have the range and speed of the old AO-7, but can cover the larger CCDs. It is shown in an exploded view below.

Exploded view of AO-L

The light passes through a 6 mm thick plane parallel plate that can be tilted by the action of two linear stepper motors in conjunction with a Delrin pivot point. The total amount of tilt in each direction is about +/- 4.6 degrees. The light beam is deviated by 36 microns per degree of tilt, so the maximum deviation is +/- 165 microns, or +/-18 pixels with an STL-6303. We have done careful raytracing to convince ourselves that no focal shift or significant aberration occurs as the plate is tilted over these small angles, nor is there any distortion, rotation, or change in magnification. Our testing has verified these results. The window is AR coated with the same coating on our STL chamber window, and has less than 1% reflection per surface from 400 to 900 nm wavelength. Our assumption is that this device is being used with long focus telescopes where bright stars in the field of view are unlikely, and is not used with short focus refractors. Short refracters should not need a fast steering device like the AO-L.

The main advantage of the new technique is that it is thin, only using up 1.483 inches (38 mm) of back focus distance, whereas a mirror-based technique would

probably require 6 inches (150 mm) of back focus. It is somewhat slower, since the motor can only tip the motor at 11.7 degrees per second, or 47 pixels per second. In this design moves are slew-rate limited. What this means to the user is that the user should use a focal length that does not produce too large of a star image. For example, if the seeing is bad and the star is 9 pixels across, it is probably jumping around by 4 pixels or so with each look, which would take 85 milliseconds to move. If under such conditions you reduced your focal length to where the star was only three pixels across, only 28 milliseconds are spent making the move, and you can achieve a higher update rate with the AO-L. The total overhead in the software for an AO-L move is 45 milliseconds. If, for example, you are taking 50 millisecond exposures with an optimized focal length (3 pixel Full Width Half Maximum stars), the total cycle time is 45 + 50 + 28 ms, or 123 ms (8 updates per second). The AO-7 advantage is that a move of any length is 20 milliseconds, but the exposure and overhead times were similar. Based on our experience and knowledge, AO-L and AO-7 rates help only slightly with reducing ground layer atmospheric turbulence, but are quite effective in reducing guide errors and wind buffeting.

3. ADAPTIVE OPTICS SYSTEM - AO-7 ADAPTIVE OPTICS

SBIG’s adaptive optics package is designed to enable users of SBIG Dual CCD cameras1 (like the ST-7) to achieve the ultimate in resolution when imaging deep sky objects. The package consists of two components: a high speed tip-tilt mirror capable of correcting the telescope pointing at rates up to 50 times a second, and a software package that implements the Lucy-Richardson deconvolution technique for image sharpening. Both items were developed by SBIG in concert with Benoit Schillings and Brad Wallis, two advanced amateurs well known in the

film and CCD imaging field. This package can produce a 2X improvement in resolution over normal self guided images, where corrections are applied only to the telescope drive. This package truly advances the capability of the amateur astronomer, considering that most professional observatories do not have comparable systems.

4. STV – VIDEO CAMERA AND AUTOGUIDER

STV Digital Video Camera and Autoguider

The STV is a unique and versatile instrument. It is a highly sensitive, cooled, digital video camera with exceptional abilities including the ability to autoguide and image without the need of a computer. The STV will take and store digital images on board for download to a computer at a later time. This makes the STV ideally suited for field use.

STV Features

• TC237 CCD with 656 x 480 Pixels and various binning modes
• Single Stage Thermoelectric Cooling
• Integral Filter/Shutter Wheel with Open, Closed and Filter positions
• Video Output to Internal and External Video Monitors
• Advanced 2 line x 24 Character Alphanumeric Display
• Fast Frame Rates (up to 10 frames per second)
• Built In Track & Accumulate (SBIG patent 5,365,269)
• 2 MB Flash memory for saving 14 images
• Remote Operation with STV REMOTE Software
• Digital Signal Processor (DSP) Powered for Highest Performance
• Standard T-Thread Front End (with screw in 1.25" nose piece)
• Telescope Port for Stand Alone (No Computer Required) Auto Guiding
• RS-232 Port for Remote Control and Image Download
• Optional 2 position Focal Reducer for 2X and 3X Reduction
• Optional C-Mount and Tripod Mount Accessories
• Optional Mini 4" Focal Length Telescope Tube for eFinder Operation
• Optional built-in 5" LCD Video Screen

What Can You Do With An STV?

• Rapidly Focus the System at Video Rates with the Focus Mode
• Adjust Focus Sensitivity with a Single Knob
• Take High Quality Images with Image Mode
• Continuous
• Snap shots
• Track & Accumulate
• Mosaics
• Auto Grab
• Save Images to Flash Memory with the File Ops Mode
• Download Images to PC for Offline Viewing and Processing
• Measure Images with the Display Mode
• Stellar Magnitudes
• Stellar Separations
• Autoguide Your Telescope with the Calibrate and Track Modes
• Measure Critical Seeing Parameters with the Monitor Modes
• Telescope PEC
• Optical System Quality
• Atmospheric Seeing
• Electronic Finder (eFinder)

Camera Specifications

Video Output:

NTSC Standard - 525 horizontal lines with 720 pixels / line

PAL Standard available as a menu option

Image Modes:

Normal = 640 x 400 binned 2x2

Wide = 656 x 480 binned 3x3

Zoom = 320 x 200 binned 1x1

Image bit depth:

10 bits for 1x1 binning mode

Up to 16 bits for other binning modes and Track and Accumulate images

Exposure times:

0.001 to 600 seconds

Cooling:

Single stage thermoelectric -25 degrees C from ambient