Lunar Observing and Imaging

A narrowband Moon

September 30, 2024Richard WrightAstrophotography, Lunar Observing and Imaging

Deep sky astrophotographers often resort to a “narrowband” filter (or line filter) to image deep sky objects when the Moon is up. This is because Moonlight scattered in the sky often washes out most color filters. However, when imaging emission nebula, we often will use a special filter that is sensitive only to a particular wavelength of light that is emitted by these narrowband targets. The most common is called “Hydrogen Alpha”, and it gives many nebula a bright pink/red appearance when photographed. This wavelength is not scattered in the sky by Moonlight and so you can do perfectly good “deep sky imaging” when the Moon is out. In fact, this particular wavelength is also great for light polluted areas.

I love the Moon too though, and every time I find myself using one of these filters because the Moon is up, I also turn the camera towards the Moon for a shot. These kinds of filters produce a monochrome image, but that’s fine for the Moon. In addition, they are very much in the red end of the spectrum and these wavelengths are slightly less perturbed by a turbulent atmosphere, which can result in a sharper image.

Big Gibbous Moon

The “Seeing” (amount of turbulence) was very good this evening (very still air), and I rather think I got an exceptionally sharp image of the Moon here. The only processing I did of this image off the camera was curves for tonal adjustments. I did no sharpening at all. The optic was a Sky-Watcher USA Esprit 150 with their 0.77 reducer. This is one of my top scopes and on this evening it did some of it’s best work under exceptionally good skies. The camera was a monochrome Player One Poseidon-M, and the filter was a Chroma 3nm Ha filter. The exposure time was 0.1 second.

Yes, I have some deep sky images from this evening too, but I’m still collecting light for those images before they are finalized.

Montes Apenninus

May 18, 2024Richard WrightAstrophotography, Lunar Observing and Imaging

The Apennes Mountains on the Moon — Montes Apennius bisects Mare Imbrium and Serenitatus

As a child, my family would visit the Great Smoky Mountains in Tennessee, often multiple times a year. I imagine future lunar citizens might vacation in the Apenninus mountains, a beautiful chain of mountains that curves along the edge of Mare Imbrium on the left side of this image. Named after a mountain range in Italy, it has a small gap (perhaps analogous to the Cumberland gap of my childhood home) that opens the way from Imbrium to the sea of Serenity to the right. Were the lunar maria actual oceans, there would for sure be a vibrant trading city located here as the most practical passage between these two great seas.

Alas, this is the Moon, and the Maria are indeed not waterways, but vast plains of cooled lava… well… a sea of frozen lava is still a sea, isn’t it?

Taken on the night of May 16, 2024, the lighting here is really quite outstanding for great views of a number of prominent features in this area of the Moon. At the upper left we see the crater Plato, which often looks quite shallow and flat. Due to the Sun’s angle at this time however you can see the highly detailed walls of the crater rising high above the smooth surface of Mare Imbrium. To the upper left of Plato, you can see a small ring of light that is the crater Fontenelle. Through the eyepiece this night, that ring was glowing in the darkness of the terminator like the lights of a great city in the night.

Midway down and to the left of the Apenninus mountains is another flat and smooth crater Aristarchus. Like Plato this crater appears to be older than the Mare Imbrium as its floor is flooded with the same cooled lava that surrounds it. A younger crater at the southern tip of the mountain range is Eratosthenes. There is no smooth floor here, and in the center, you can see a tiny dot of light that is the central peak of a mountain of material that was rebounded when the impact crater was formed.

While the Moon is not quite as dynamic as the Sun, it is different every night, and even every hour you can see changes in the surface as the light and shadows dance across the lunar day. Even the smallest telescope or binoculars will reveal this world to you, and I encourage you to go take a look as often as you can.

The Aristarchus Plateau

January 8, 2023Richard WrightLunar Observing and Imaging

On the evening of January 5th 2023, the Sun’s angle on the Moon was just right for what I think is a spectacular view of the crater Aristarchus and the Aristarchus plateau. The Plateau is a distinctive squarish region about 200km across with an offset color from the surrounding lunar mare, from which it rises in places 2km above the Oceanus Procellarum. The crater itself is the brightest crater on the Moon and can be spotted naked eye, and will stand out even in Earthshine.

Image of Aristarchus Plateau — The Aristarchus Plateau is a very distinctive square looking feature with the brightest and youngest large crater on the Moon.

Equally spectacular to me was the far limb showing numerous craters and ridges illuminated by what to them was the rising morning Sun. Often imagers will keep their cameras oriented so that North is up for their astronomical images, and this includes the Moon. I tilted the camera purposely here as I liked the more dramatic view as if flying over the Moon and viewing the landscape personally. There are plenty of atlas’s with topographically accurate orientations to their reference images. I wanted something that made me feel like I was there, because to me at the time, I was — and I snapped a photo to remind me of the visit.

Fly me to the Moon

December 10, 2022Richard WrightAstrophotography, Lunar Observing and Imaging

The Moon and Mars — From Central Florida, the Moon only got “close” to the planet Mars.

The evening of December 7th, 2022 was a Full Moon and for many of my US friends the Moon occulted Mars for a short time. In Florida and most of the east coast, it was only a near miss and yes I photographed it like everyone else. But this post is not about that event, but rather the show the Moon was putting on at it’s South Pole. When the Moon is full the Sun is bearing down straight on it, more or less, from our vantage point. The Moon though is a sphere (okay, sphere-ish), and it’s not a smooth sphere, it has bumps, valleys, hills, etc. We often love observing the lunar terminator when these features are in stark relief, but still we are seeing these features from directly overhead. If only we could fly to the Moon, and look at them from a low elevation to see them in the distance rising from the lunar surface. Well… we can!

This is exactly the view we have when the Sun is grazing along the edges of the Moon. On the night of the occultation, the southern edge was putting on quite a show and I just had to take some video for later processing (a technique we call “Lucky Imaging“).

The image below was taken through a Sky-Watcher 180mm Maksutov-Cassegrain telescope and a Player One Neptune C II high speed camera. Many thousands of frames were taken, but the atmosphere is turbulent, so a computer program helps search through all the individual frames to find the ones with the most stillness to them. They are combined to make a clean smooth image, and then I apply a little sharpening to clear up any blur remaining. I also rotated the original image 180 degrees to give the sensation of flying over the Moon rather than under it.

Southern region of the Moon — Near the South Pole, the grazing light of the Sun brings the rugged lunar terrain into stark relief.

The conditions were excellent, so I decided to try doubling the magnification with a 2x Televue Powermate. This brought my total focal length to 5,500mm and with my cameras small pixels, an astonishing 0.11 arc-seconds per pixel resolution. For most deep sky objects (galaxies and nebula) you can only achieve this much resolution/magnification with long exposures by putting your telescope in space where there is no atmosphere. Doing this from Earth requires very fast frame rates to capture the stillness, and a great number of frames to choose from. That’s why we call it LUCKY imaging!

This second image is the left most area from the image above, but taken at twice the focal length. The camera rotation doesn’t match if you can forgive me for that, but it still captures the feeling of really “being there”, at least it does to me.

Finally, for the selenophiles out there (of whom I count myself), I’ve also labeled some of the more prominent craters in this image. Who say’s the full Moon isn’t interesting to photograph?!? Definitely not me.