Short Wavelength compositional
analysis with UV / IR filters
with the Orion 10" f/3.9 Newtonian Astrograph
June 13, 2016
Note: Conventional usage of South is up in all images, more info below.
color variations on the moon are so subtle as to be nearly invisible
to the naked eye, we can differentiate rock and lava colors with
CCD cameras with suitable filters. Materials that are brighter
in the shorter - hence bluer wavelengths are higher in metals
in their composition, and more silicate based rocks are brighter
in longer - thus redder wavelengths. For this experiment,
I used an Orion UV and IR pass filters to differentiate the rock
types. By imaging the lunar surface with all reflective
optics to ensure sharp focus at both wavelengths - and
looking at the difference between the images by subtraction,
I can enhance the more UV reflective materials and identify the
areas on the moon that are more metal rich, or have had a more
recent impact which are bluer - and stand out over the more weathered
darker rock on the surface.
The results of
this differentiation were surprising! It is widely known
that Mare Tranquillitatis is rich in blues from metals like titanium
in the lavas, however other areas have peculiar shadings that
do not seem to have any visible light equivalent structures.
Here are some of the results in review from this exercise.
Raw Infra Red image at prime focus with the 10".
Note that the "lake" inside Mare Serenitatis is
Raw Ultra Violet image - the "lake" is now invisible at
Here is the full field (quarter of a degree), I can get about a quarter of the
of the full disk of the moon with the 10 inch with its 1000mm FL.
The upper image is a conventional white light shot, and the lower is UV-IR to
accentuate bluer regions as white, the equally reflective areas are grays,
and the blacks are the areas that reflect more of the longer redder wavelengths.
Many of the craters are completely gone! However, quite a few bright spots
that remain are fresher craters that have UV bright ejecta or have
exposed new material from underneath. We will now zoom in on
various sectors of this high resolution image and take a closer look.
Select size for enlarged view:
1400 x 1200
I find this to be one of the most amazing images in the set! Ive
highlighted in each image some areas of interest. Lets take a look
at each one in turn. Again, Im merely showing the color contrasts between
UV and IR here, the interpretation of the significance of such color
variations is beyond the scope of this write up.
A. The comparison
between the ejecta patterns of Autolycus and Aristillus are interesting.
while the upper crater - Autolycus is essentially sitting in
a dark sea of redder material, Aristillus has an impressive apron
of high UV reflective spray around it.
B. Archimedes is
essentially featureless with a dark interior, however two banks
of materials that are UV reflective are on the north and south
sides just outside the crater.
C. Timocharis crater
- locally bright ejecta very near the crater walls. Compare to
D. The most fascinating
area of all here, the sharp edged zones in the UV/IR reflectivity
seem to show the boundaries of lava flows. But why do the edges
of the zones become more intense in difference between UV/IR?
E. Really wild
differences here! Leverrier is the crater on the right side of
this zone, note the sharp boundaries with dark edges seen here
marking the edges of layered lava flows.
F. Lambert Crater
- sits in a zone of dark silicate lava. Just north (below) several
zones in the lava fields are seen.
These two zones
mark a very complex region around Mare Fecunditatis on the left
and Mare Nectaris on the right. Well cover Mare Tranquillitatis
in another panel.
The left most zone
is an isolated area of enhanced UV reflectivity in Mare Feconditatis.
Just above it to the south the rest of the sea is dark and more
reflective in IR. The right side of the sea is a mix of both
But look the central
zone! Messier A&B sit in a lighter zone of enhanced UV, but
the rays that point to the right - the dual ejecta from their
impacts is jet black. This shows that material from perhaps deep
down had been scattered by the impact over the UV brighter lava
flows on top.
Finally, the third
right most zone is the sea Mare Nectaris. Look at the beautiful
fan of UV bright material spraying up wards from the crater Madler.
To its right is the ring of high sun lit crater Theophilus. A
complex mix of light and dark material here.
The most intense
region on the moon of high UV reflectivity is Mare Tranquillitatis.
This entire sea is very bright in the UV and contains few zones
of darker redder material.
A. The northern
end of Mare Fecunditatis is uniformly bright in UV, covered in
B. Messier A&B
- The ejecta from this set of craters is black against a bright
C. Centered on
the very peculiar crater Dionysius, the only crater on the nearside
with black ejecta rays- has a significant area of UV brilliant
D. The area of
the moon with the brightest UV reflectivity is Mare Tranqullitatis.
This must be a geologists and perhaps ore miners dream, so much
metal rich lava has been found here, highlighted by some bright
areas that are very extensive.
Another very complex
A. Mare Tranquillitatis,
covered in previous panel.
B. Lalande crater
has a large amount of UV reflective ejecta.
C. Copernicus ejecta
spray apron. The rays of this great crater are very bright in
UV, and considering that the crater itself is bright inside,
this makes sense.
D. Copernicus crater.
Look at this dichotomy in UV reflectivity! the lower right quarter
of this crater is like a dark pie wedge shape of low reflectivity.
What would cause this? A mystery!
The entire inner basin is lighter in UV than the edges. Many
observers have indeed reported a ruddy color to the basalts here,
very much like what I have seen on Mauna Kea in Hawaii.
A. Bright patch
on shore of the sea near Litrow B crater.
B. Menelaus crater
is VERY bright in UV and would seem to indicate its recent excavation.
C. Bessel crater,
in the mid section of Serenitatis, with bright ejecta wrap.
D. Just below Bessel
is this odd cone shaped zone of high UV reflectivity.
E. The range of
mountains on the north end of Serenitatis shows a contrasting
brighter more gray colored area but just to its south is a dark
UV absorbing zone.
F. Aristillus crater
with a fantastic UV bright ejecta pattern!
Color mapped full image showing bright zones are more blue/UV reflective
Select size for enlarged view:
1400 x 1200
Instrument: Orion (GSO) 10" f/3.9
Platform: Astrophysics AP1200
CCD Camera: Image Source DMK 51
Filter: Orion IR Pass/UV
Exposure: 1/30 sec 12fps
Location: Payson, Arizona
Elevation: 5150 ft.
Sky: Seeing 2/5, Transparency 7/10
Outside Temperature: 75F
25/1200 best frames, alignment in Autostakkert, USM, Levels and
Contrast Masking In Photoshop CS2 and Image J.|