Operations Guide for Using SSON
Overview
After you register with us and we approve your registration you have greater access
to our system. You can then purchase credits, which you use to schedule the images
you want to take for an observing run. You have control over managing your account:
check which jobs you have scheduled, check what jobs are completed, and download
your completed images. In addition, you can set up “Affiliates” for your account.
Affiliates can use credits that you allocate to them and manage their accounts under
your primary account. This is a convenient tool for professors, teachers, astronomy
clubs, and individuals to manage an account among many people.
You can easily schedule to take
images of objects using our Observation Request
Form. This form contains an extensive list of catalogs with hundreds of thousands
of objects that you can choose and select for your observations. On the Observation
Request Form you can set up multiple exposures and sequences of your objects selecting
among the available filters.
Sierra Stars Observatory Network started operation with a single observatory: the Sierra Stars Observatory in Alpine County, California. In the fall of 2008 a new telescope joins operation with the Sierra Stars Observatory: the Rigel Telescope in Sonoita, Arizona. You have the option of selecting the Rigel Telescope as a backup for your observations scheduled on the Sierra Stars Observatory in the event it is down for weather or other reasons or scheduling jobs to run on the Rigel Telescope directly. If you select you use the Rigel telescope for a backup for schedules to run on the Sierra Stars Observatory telescope, then the exposure times on the Rigel telescope are increased to give you an equivalent signal to noise ratio (SNR) with a comparable image scale and a little large field of view (FOV). You schedule jobs and manage your account for using all telescopes through the Sierra Stars Observatory Network web site.
General Specifications of
Telescopes for Planning Observing Sessions
When planning your imaging sessions
you should be aware of the general specifications of our observatory systems to make the best
use of your time and to get the results you desire. You can quickly refer to the specifications
for each observatory below:
1. Sierra Stars Observatory
Telescope Specifications
- Primary mirror
diameter – 0.61 meter
- Focal ratio
– f/10
- Focal length
– 6,100 mm
Camera Specifications
- CCD chip –
Kodak KAF09000
- Chip dimension
– 36.7mm x 36.7mm
- Pixel matrix
– 3,056 x 3,056
- Pixel size
– 12 microns
- Pixel image
scale at prime focus – 0.4 arc seconds un-binned
- Operational
binning and image scale – 2x2 binning = 0.8 arc seconds/pixel
- Peak quantum
efficiency – ~ 70 percent in the V band
Filter Set
- Johnson – Cousins
B, V, R, I, and clear (no filter) positions
2. Rigel Telescope
Telescope Specifications
- Primary mirror
diameter – 0.37 meter
- Focal ratio
– f/14
- Focal length
– 5,180 mm
Camera Specifications
- CCD chip –
Kodak KAF09000
- Chip dimension
– 36.7mm x 36.7mm
- Pixel matrix
– 3,056 x 3,056
- Pixel size
– 12 microns
- Pixel image
scale at prime focus – 0.5 arc seconds un-binned
- Operational
binning and image scale – 2x2 binning = 1.0 arc seconds/pixel
- Peak quantum
efficiency – ~ 70 percent in the V band
Filter Set
- Red
- Green
- Blue
- H-Alpha
- Clear
3. Grove Creek Observatory Telescope
Telescope Specifications
- Primary mirror diameter – 0.36 meter
- Focal ratio – f/6.13
- Focal length – 2,182 mm
Camera Specifications
- CCD chip – Kodak KAF1608ME
- Pixel matrix – 1,530 x 1,020
- Pixel size – 9 microns
- Pixel image scale at prime focus – 0.84 arc seconds un-binned
- Operational binning and image scale – 2x2 binning = 1.69 arc seconds/pixel
- Peak quantum efficiency – ~ 85 percent in the V band
Filter Set - Red
- Green
- Blue
- Luminance (Clear with UV and IR band cutoff)
- H-Alpha
- OIII
- Sulfur II
Planning Imaging Sessions
To make the best use of your valuable
imaging time you should carefully and deliberately plan for the images you take.
The position of an object in the sky, the local time, and the date together determine
which objects are best placed for a specific observing run. Ideally you want to
image objects when they are as high in the sky as possible to look though the least
amount of atmosphere and attain the best seeing for that night. The highest point
in the sky an object can reach at any location is called a transit (when the object
crosses the meridian). After a transit
an object gradually gets lower again in the sky.
You also should concentrate on
objects that transit high enough in the sky at the latitude of the observatory site
to be reasonably placed for good imaging. For example, an object that never transits
higher than 25 degrees altitude above the horizon would not be a good choice for
imaging because the seeing for an object that low in the sky, looking through so
much atmosphere, would likely be very poor. The good news is that the SSO master
scheduling program automatically schedules your images to be taken during the most
optimal time possible for a selected night. In other words the scheduling program
sets your images to be taken as close to transit as possible.
You can easily avoid these pitfalls
with a little planning before submitting your observation requests. Using online
or computer planetarium programs you can quickly check that an object will be reasonably
placed during a given date and observatory location for imaging.
Also check out the
SNR and Exposure Times section of our web site for
more information to help you plan your imaging sessions.
Other Things to Consider
The Sierra Stars Observatory and
Rigel Telescopes are powerful scientific
astronomical imaging systems designed to provide a relatively wide field
of view, excellent quantum efficiency, low noise and excellent photometric capabilities.
These characteristics open up many observing possibilities to our clients. It also
places a few constraints that you should be aware of.
- The maximum shutter
speed of the FLI Proline camera is 0.01 seconds. This exposure time is too short
for imaging very bright objects such as the major planets, the brightest stars,
and the moon.
- When doing photometry
work determine what signal to noise ratio (SNR) is needed for your project and set
your exposure times accordingly. Keep in mind that exposure times to attain a desired
SNR vary for each filter. High precision photometry typically requires a SNR of
100 or more, while accurate astrometry can be performed at much lower SNRs (as low
as 10 to 20). Most software packages with photometry capabilities will calculate
the SNR of objects in your images. For planning purposes you can use some of the
CCD SNR calculators found online beforehand.
- The maximum exposure
time you can set for images is 300 seconds (5 minutes). To attain greater integration
times you can stack your images using one of the many available commercial or free
software packages. You can stack as many images as you want to create total exposure
times of an hour or longer. Our CCD
camera cools up to 65 degrees below the ambient temperature and typically operates
at -45 C. The CCD chip and camera generate very low noise. Thus stacking images
greatly increases the SNR while adding very little additional noise. Finally stacking
images with shorter exposure times produces better FWHM (full width at half maximum)
star images and helps keep brighter objects from “blooming” (filling the pixel wells
and overflowing) enabling better photometry of brighter objects.
- For doing photometry
work we offer a set of Johnson-Cousins B, V, R, and I research-grade filters. These
are widely used filters for doing broadband scientific photometry. The letters stand
for the band of light that they let pass while cutting off light from other parts
of the spectrum: B = Blue, V = Visual (Green), R = Red, and I = Infrared. There
is also a Clear setting with no filter to get the most photons through the entire
range of the CCD chips sensitivity.
- Calibration frames
(images) are critical for getting the best quality, least noisy, data from your
images and for creating the best esthetically appealing images for show as well.
By default we apply the calibration frames to your images saving you a great deal
of time and bandwidth. This service greatly streamlines your image taking process
and saves you steps that can introduce errors if you make mistakes.
Alternately you may choose to receive your images as “raw” (un-calibrated) and download
the calibration frames. This entails more work on your part but might be important
for some people doing research that requires access to the raw data only. However,
we highly recommend that you take advantage of our auto-calibration feature as this
will greatly reduce the amount of work you will have to do for your image processing.
Calibration frames consist of bias, thermal, and flat field frames. The calibration
frames are date stamped and located in directories which are also date stamped so
you can always find the correct calibration frames corresponding to the dates of
your images. The frames are actually a sequence of steps culminating in quality
flat field frames for each filter. Bias frames are subtracted from the thermal frames
and then the resulting thermal frames are subtracted from the flat field frames.
Therefore, if you choose to do so yourself, you can calibrate your images by applying
the appropriate flat field frame for the corresponding filter used to each of your
images.
Taking Color Images
If your main interest is creating
high quality color images of objects, you can do so using our B, V, R, I and Clear
filters on the Sierra Stars Observatory. On the Rigel Telescope you can choose the
standard RGB and Clear filters for color imaging projects. Many of the best high-quality color images you see in Astronomy magazine,
Sky and Telescope magazine and online, are created using filtered images and combining
them with one of the many available image processing software programs. One of the
most popular and effective color image processing techniques is called LRGB for
Luminance, Red, Green, and Blue color processing in which unfiltered, red filter,
green filter, and blue filter images are combined together to produce a color image. The B, V, and R filters on the SSO
telescope approximate well with B, G, and R filters respectively and
together with using our Clear (no filter) setting produce excellent LRGB color processing
results. You will find many examples of this color processing technique on our web
site.
Doing Science
For many of us doing science is
a means and an end in itself. It can be very fulfilling and rewarding. You can discover
new things, analyze existing systems, and simply experiment and explore using the
SSO system. There are many potential projects that come to mind. For example:
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