Rick Evans' Amateur Lunar Photoclinometry, Spectroscopy, and Astrophotography -- Studies of the Moon and some General Astroimaging

Rick Evans' Amateur Lunar Photoclinometry, Spectroscopy, and Astrophotography
Studies of the Moon and some General Astroimaging

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Rick Evans' Amateur Lunar Photoclinometry, Spectroscopy, and Astrophotography

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INTRODUCTION

Welcome!

I am an amateur astronomer interested in the moon. A few years ago I joined the Geological Lunar Research Group (see http://www.glrgroup.eu/old/home.htm and also http://digilander.libero.it/glrgroup/) and continue to be an active member. Some may think that amateurs can contribute little to lunar studies or that "everything has already been done", but this is not true. In fact the moon remains a very accessible research subject for the interested amateur astronomer. I am particularly interested in lunar topography, geology and spectral mapping. This website will hopefully serve as a guide to other interested amateurs. I use photoclinometry, spectroscopy, and multispectral and hyperspectral imaging as tools to study the geology of lunar features. Although this website also includes some solar system and deep sky astroimaging, the emphasis is on the moon.

The average seeing at my observing site at 42.35 N, 71.5 W is about 2.5 arc seconds based on FWHM measurements of stars and only exceptional nights approach 1 arc second seeing. It is a difficult location for high resolution imaging. Most of the time the Canadian/Northern US jet stream sits squarely over my small state of Massachusetts in New England. And, from my mid-northern latitude, the ecliptic is much lower in the sky than at the equator. This means that I have to image through a lot more atmospheric air mass. I am reconciled to my mostly poor seeing conditions and just do the best I can. A very few times a year I can attempt the imaging miracles that amateurs in Brazil and the Phillapines perform weekly and those in the Canary Islands and Florida perform almost as often. My main imaging scope is a Mewlon 250 on an EM-200 mount. My sharpest images so far show 1.0 - 1.4 km crater resolution and for fine linear structures I've managed to image most of the extent of the Hadley Rille and the more difficult Alpine Valley rille. I use a Celestron 9.25" scope on a Meade LXD75 mount for filter imaging and spectral work because it has lots of available backfocus. My other imaging scopes are an OMC300 subaperture maksutov cassegrain (Orion Optics, England) and a Gladius 315 Dall Kirkham scope (Lazzarotti Optics, Italy). I recently finished a small roll-out type observatory for the Gladius 315 on a Losmandy G11 Gemini mount. The Gladius has a focal length of 7875 mm, has 20% central obstruction, and weighs 11.6 kg. This setup could become my primary lunar imaging platform on nights of exceptional seeing. It is an F25 scope and it isn't really designed to image at shorter focal lengths which are often necessary on nights of average or below average seeing. So, at my location in New England, the Mewlon may remain my most used imaging scope after all...

Gladius 315/Losmandy G11G Mewlon 250/Takahashi EM-200 OMC300/Takahashi EM-200

The OMC300 can produce very good lunar images but achieving focus at the best focal length using standard accessories can be a bit tricky and frustrating, especially if the camera or barlow are changed or a filter wheel is added. The handmade OMC300 is not nearly as forgiving to use for imaging as more common mass-produced Schmidt-Cassegrain scopes of comparable aperture. I generally prefer to use the Mewlon 250 for imaging and it seems well suited to my local seeing conditions. My Celestron 9.25 inch (235 mm) F10 scope can also be used for imaging, but while it is the easiest of all of my scopes to focus, mirror shift is inherent in the design and is really annoying at high power. I also have a 5 inch Meade ED doublet "semi-apochromatic" refractor, but it excels mainly at visual work and can't really compete with my other scopes for imaging.

I usually use a Lumenera 075M camera (640 x 480 pixels, 7.4 micron pixels, 60 fps) but sometimes also use DMK cameras (i.e. DMK 31 at 1024 x 768 pixels, 30 fps and the DMK 41 at 1280 x 960 pixels, 15 fps... both with 4.65 x 4.65 micron pixels). Each area of lunar study that I have been involved with is listed below. My personal imaging protocol is available for download below. If you would like to know more about one of the topics, choose it from the menu on the left hand side of this page. Image albums have recently been consolidated into the Photo Gallery menu. If you want to leave a comment, feel free to sign the Guestbook, join the newly created Forum or contact me at revans_01420 (at) yahoo (dot) com.

Spectral Parameter Mapping:

I recently wrote a VBA program for Excel 2007 that will analyze Clementine UVVIS/NIR data and map mineral absorption trough band center minima, and band depth for orthopyroxene (890-945 nm), clinopyroxene (950-1000 nm) and olivine (1005-1095 nm) as well as mapping the FWHM (full width at half maximum wavelength), and the optical maturity index (OMAT) for any area of the lunar surface imaged by the Clementine probe between 415 nm and 2000 nm. The program is fully automated and produces the eight maps described above after inputting the nine Clementine band images from 415 nm to 2000 nm in txt format. A full description of the methodology should appear in the free online journal Selenology Today issue #14 scheduled for the spring of 2009 if all goes well. The maps are generated in txt format that is readily converted to 32 bit tiff format so that the spectral parameter values can be read from any map pixel using the free program ImageJ. The maps for Bullialdus below are only in jpg format. Over the next couple of months I hope to find the time to add Spectral Mapping to the website menu and provide additional details of this very interesting technique. Please note that this method is EXTREMELY sensitive and that trace amounts of pyroxines and olivine are detected. You MUST refer to the band depth to know if a trace amount or a concentrated amount of a mineral class is being identified ! !

Photoclinometry:

Alpha Arago Dome* Heightmap (DEM) Dome Model Topographic map

* image by Paolo Lazzarotti (GLR Group)

Deep Sky Astrophotography:

When the moon isn't out or seeing is a problem I sometimes do deep sky imaging with my own equipment or using a rented remote-control telescope over the internet. Some of the deep sky images I've taken are shown in the PhotoGallery, Deep Sky submenu.

Whirlpool Galaxy (M51) Ring Nebula (M57) North American Nebula

Solar System Astrophotography:

Saturn Lunar Craters Jupiter

High Resolution Lunar Imaging: (see lunar album)

My image processing protocol requires Registax 4.0 and Photoshop CS2 with Magic Focus plug-in. It has been updated as of May 16, 2009.

Download Image Processing Protocol: http://www.freewebs.com/revans_01420/ImagingProtocol-2.pdf

Lunar Terrain Maps:

Terrain Map of Theophilus & Cyrillus

Spectroscopy:

Lunar Broadband Multispectral Imaging:

Processing of Calibrated Clementine UVVIS Images:

Ratio Image (Tycho Rim) False Color Image (Tycho Rim)

Principal Component Analysis of Lunar Features:

Red=1st Principal Component, Green=2nd Principal Component, Blue=3rd Principal Component

Imaging Spectrography (Multi & Hyperspectral)

500-1000 nm AOTF Camera Adapter Spectral match for Olivine

Study of Dionysius West Rim Spectra Using a 9.25" SCT and Multiple UVVIS/NIR Interference Filters:

Mixture Deconvolution:

Extended SWIR (Short Wave Infrared) Imaging:

Note that olivine is darkest (shows maximum absorption) at 1000 nm.

Imager: SU320MX Indium Gallium Arsenide Camera

(900-1700 nm range)

Apodizing Masks:

An apodizing mask improves seeing in conditions of high frequency atmospheric turbulence, increases the contrast of subtle details like lunar rilles and planetary banding, and decreases the size of the stellar PSF by removing the outer diffraction bands from the Airy disk. On the other hand, it increases the size of the center of the Airy disk and decreases the theoretical resolution of the telescope. But, this theoretical resolution limit will not be attainable in average seeing conditions for most medium sized telescopes regardless. Apodizing masks are used over telescope objectives and consist of concentric layers of an apodizing filter material surrounding a central clear area several inches in diameter. If screen material is used, then doctrine says that the apodizing filter can only be used on planets or stars because of rainbow diffraction patterns peripheral to the image. However, my experience has been that it can in fact also be used on the moon without spectra appearing in the camera image. I had thought that a neutral density (ND) gel sheeting filter material might be more suitable for the moon since there would be no possibility of spectra produced, but unfortunately my tests with it indicate that it blurs the image and cannot be used. A comparison of Saturn images taken only a couple of minutes apart with the same telescope using an aluminum window screen apodizing filter is shown below:

I find that use of a window screen apodizing mask improves seeing at least about 1 point on a scale of 1 to 10 when looking at stars or planets and maybe a little more. It produced a definite improvement in hi resolution images of Saturn using my Mewlon 250 (see images above). My experience so far, in spite of doctrine to the contrary, is that it also does work on the moon without spectra appearing in the webcam image.

My Simple but Practical Shed Design Roll-Out Observatory:

The advantages of a roll-out design are 1) it is inexpensive 2) remote telescope control is possible via an umbilical thereby protecting the observer from mosquitos in summer and cold in winter 3) better sky view without viewing restrictions imposed by being inside a building 4) the tripod is placed on the brick patio which is a vibration free surface superior to a wooden building floor. The disadvantages are 1) need to roll or carry the telescope/mount in and out for each use 2) need to polar align before each use (but made easier by marking the pavement). In addition to this roll-out observatory I also use a large second floor observing deck attached to the house (shown below) which has the best sky view of all. The main problem here is that the deck floor is rubber coated wood, and so there is some vibration (roughly equivalent to a lite breeze) noticible in high power views of the moon and planets caused by the observer's movements on the deck. For a completely still image at high power, I have to literally hold my breath during high resolution imaging unless imaging is done remotely using an umbilical running from the deck to inside the house...Also, the dark floor radiates heat for several hours after sunset on warm days causing some image destabilization.