 Project
Jupiter
 
VIII. Data Gathering
Methods
D. Astrometric Eyepiece Method
1. Accuracy
The basic techniques used here is the calibration of a reticle
eyepiece to enhance the capability to measure separations that are
normally only estimated.
2. Basics
The observer may use the Meade Corporation Astrometric eyepiece
15 or the Celestron
Micro-Guide Eyepiece 16 to
make the needed measurements. Rather than purchasing one of those
eyepieces, see if another member of your local astronomy club would be
willing to loan you one for this project.
The reticle markings in the Meade advanced eyepiece are:
Where Î is the
linear scale that, when calibrated, is used to measure separations of
objects, Ï is the
semicircular Position Angle Scale,
Ð is the 360°
Position Angle scale, and
Ñ is a Double Crossline/Concentric Circle area used for guiding.
During each observing session the observer takes measurements of the
distance between moons of Jupiter and the center of the Jupiter image.
Each measurement is then used as one data point in the Jupiter Project
data analysis.
3. Equipment Selection
Because the separation of the satellite in any given observation is
to be compared to other observations, there is a need to have a
consistent calibration from one observation to the next. The observer
needs to select equipment that as that enables the maximum separation of
the moon to be still in the FOV during subsequent observations without
having to change your equipment.
4. Reticle Scale
It is helpful if the field of the linear scale in your eyepiece is
determined before the observing sessions begin. This is a required step
before data submission to maximize the use of the calibrated eyepiece.
Provide the calibration ratio of the arc-seconds per Astro-Metric
Unit (AMU) on the data sheet. Also, provide as a separate attachment the
calibration effort (position of reference star & timings ) for the
eyepiece
( 17 ).
The use of a Barlow to make more accurate measurements when the Moons
are close to Jupiter is encouraged.
5. Data Logging
Measure the separation of the selected Moon from the center of
Jupiter on each on each observing session. It is recommended that the
scale units be recorded, as that "raw" data will be multiplied by the
scale factor within the EXCEL program. Avoid the tendency to "smooth"
the raw data at this stage. If on observation #3 the separation is 15
reticle units, on observation #4 it is 14 units, and on observation #5
it is 16 units, that is OK. Report the data as measured. For each
observation, record the separation measurement ( in scale units ) on a
separate line on the data sheet (Attachment A).
Also, on one session, record on Attachment A the diameter of Jupiter,
in reticle scale units.
If a Barlow lens is utilized for some observations, please annotate
Attachment A with the additional magnification used.
17 Mizar Consulting has generated a
spreadsheet for this purpose. The spreadsheet evaluates the declinations
and makes corrections, reviews the data for consistency, and produces a
statistical analysis of the calibration effort. Contact Mizar Consulting
to obtain a free copy.
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Project
Jupiter