Further Helpful Hints Concerning Cometary Photometry
- Visual photometry of comets
-
Note that there are a few different
acceptable
methods
for properly obtaining a total visual magnitude estimate of a comet.
-
Ideally, observers should strive to make total visual (or CCD) magnitude
estimates of comets once every possible night (and only once per night,
particular in the case of visual observations, unless the comet is observable
all night long and very close to the earth, when a real brightness change
may be noticeable in several hours' time).
- Observers should always use comparison stars with visual or V magnitudes
from acceptable professional catalogues, and a
minimum of 2-3 stars should
be used for each estimate that are within 0.5 magnitude of the comet's
brightness; use of deep-sky objects (galaxies, nebulae) are NOT acceptable
for deriving comet brightnesses. Observers using V comparison-star
magnitudes should be careful to avoid red stars (that is, those with
B-V > +0.7 or so, especially K, M, and later-type stars, because they
will appear 0.1-0.4 mag fainter to the human eye than their V values
suggest).
- Observers of comets making total visual magnitude estimates should
always use the smallest instrument needed to easily see the comet, due to
large instrumental effects that can again cause values to be too faint.
- When
comets are less than 20° or 25° from the horizon, the observer should
usually correct for atmospheric extinction.
- CCD photometry of comets
- All photometry of comets: The description of the
ICQ format for
contributing photometry of comets explains the sorts of data that are
important to astronomers for archiving such observations. Please read
this carefully, noting that much more information is required of CCD
photometrists (bottom of webpage).
Recent
comet magnitude estimates
ICQ