Triton Watch Observing procedures
The following procedures are the observing plan that we request all our
observers follow each time they observe Triton. If you have any questions
about these procedures, please contact us at TritonWatch@boulder.swri.edu.
- General
- If you are not yet a registered observer, you must sign up on the Registration Form.
- The only format for CCD imges is FITS (Flexible Image Transport System)
- Image file names must follow the format:
YYYYMMDD_TFXX_IIII.fits
(the filename format is described here).
- Observing Constraints:
- Moon must be more than 45 degrees away from Triton
- Triton's airmass must be less than 2.0, or, if that is not possible
from your observing site, observations must be made
within ±0.5 hour of Triton's meridian crossing.
- Ephemerides are available.
- Finder charts are available.
- Obtain two images of Neptune/Triton in each filter (all or any of
UBVRI)
- Center Neptune in the CCD field and note approximate X,Y coordinates
- In one set of images (in each filter), Triton should be
well-exposed but not saturated. (Neptune will likely be overexposed in
this case.) For maximum S/N, an ideal exposure would be the longest
one possible where no pixels in Triton are over-exposed
(saturated or in the non-linear regime of your CCD). Please note that
if Neptune is over-exposed and causes bleeding into the image of
Triton, then if it is possible, rotate your CCD so that Triton is
not affected by any bad/bleeding rows or columns.
- In the other set of images, Neptune should be well-exposed
(i.e., no pixels saturated or in the non-linear regime of your CCD).
- Obtain calibration images
- A well-exposed flat field for each filter used to observed Triton.
- A bias (``zero'') frame.
- Two dark frames with exposure times equal to the shortest and the
longest exposure times used for the Neptune and Triton data images
if your detector has a significant dark current.
- We recommend that multiple calibration images be obtained and
combined (e.g., that the final flat field for each filter is the
median average of five such images), to remove cosmic rays.
- Optionally perform initial CCD reductions on data images. The observer
has the choice of either:
- Reducing the Triton CCD images
- Bias and/or dark subtraction.
- Flat field correction.
or,
- Uploading to us the calibration images (flats and bias) as well as the
Triton images, and we will perform the reductions.
The advantage of the first case is that the observer has fewer images to
upload (which is more efficient for slower data connections). The advantage
of the second case is that the observer does not have to perform the
reductions (possibly more efficient for oservers with fast data
connections).
- Upload your data using our Submission Form.
Note that we do not require you to observe and submit standard calibration star
fields. We will be using on-chip secondary standards that we have pre-observed
and calibrated. For this reason, we request that you do not clip your
images (e.g., to extract just the area around Neptune), since we need all the
stars on your CCD frame for calibration.
Triton Watch Project
(TritonWatch@boulder.swri.edu)
