Astrophotography

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

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.

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.

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.

 

 

Annies Dragon

September 28, 2024Richard WrightAstrophotography

A well known and often shot emission nebula in the constellation Cepheus is the “Elephant Trunk”. Cropped in on just the trunk people see all sorts of things. One day by chance my wife saw the image rotated in a such a way, that she said it looked like “Smaug the dragon” (from the Hobbit). I thought, it REALLY DOES. So, at least to me for now on, this object is forever more “Annies Dragon” (my wife’s name is LeeAnne).

Dragon shaped nebula
Annies Dragon is an emission nebula that is a part of IC 1396.

This particular image was just shy of two hours of hydrogen alpha exposures with a Player One Poseidon-M camera and Chroma 3nm Ha filters. Normally, these monochrome Ha images are grayscale but I did add just a tint of redish brownish to give it a sepia-tone type treatment. It’s a photo of a dragon after all, and one day it will be an old photo of a dragon šŸ˜‰

 

Solar Nirvana?

July 28, 2024Richard WrightAstrophotography, Solar Imaging

The weather for astrophotography in Florida is so dismal in the summer, or rainy season as I call it. Even when it’s bright and hot outside, there’s a haze of moisture and thin clouds most days, and the nights are quite opaque. We had a break the other morning and I had a chance to get out some new gear I’ve been curating. I think my solar rig is “almost” as good as I can hope for, and I captured a nice view of the Sun the other morning (7/26/2024) and Active Region 3762.

The Sun in Hydrogen Alpha light and my rig used to capture it.

I have a DayStar Quantum 0.5 Angstrom Ha filter. This is a very specialized filter for capturing light just from glowing Hydrogen in the Sun’s atmosphere. It reveals an amazing amount of surface details, and it works on the back of most any refractor as long as it isn’t too big. I will be honest, it’s an advanced piece of astro-gear, and I struggled a bit to get the tip top performance out of it for a while. Focal ratio matters, sort of. What really matters is nice parallel rays of light coming into it, and certain optics technically change the focal ratio, but don’t necessarily produce the most parallels rays. I also have found, despite my earlier confidence, that a front mounted energy rejection filter helps a great deal (ERF). I bought an 82mm Lunt ERF second hand in a custom 3D printed cell that fits my Astrophysics Stowaway telescope. I use a TeleVue Powermate or a Baader 4X Telecentric on the back to get the focal ratio/parallel light rays going.

Other luxuries in this photo. A Paramount MYT with absolute encoders, which is an absolute joy to use. Already aligned and ready to go, you just flip a switch and go. The scope is an Astro-Physics Stowaway refractor, there’s a waiting list and/or lottery to getĀ  these fine refractors. I really think Roland Christen is the modern Alvan Clark. There’s a top of the line Feather Touch focuser on the back, and an Optec QuickSync motor on it. Finally, a Player One Apollo Max on the back is taking the images. One further improvement is a cooled camera. There’s some debate as to if this really helps with solar imaging, but I do find that the fact that the temperature is regulated does make a big deal. Not so much that it’s “reducing noise” in the raw images, but calibration frames need to be at the same temperature if you you want the flat frames to work properly. Nine times out of ten, it doesn’t seem to matter, but occasionally, I’ll end up with flats that won’t work, and this is the reason why. Some helpful advice… “Just keep your optics clean”… makes me laugh.

I think this is just about as good as it gets for a high quality solar rig for myself. I might have to get a 3D printed cell for that ERF to fit my Esprit 150 though. It’s only taken some 30+ years of wheeling and trading up to get here. As Ferris Beuler says, “If you have the means“… maybe you won’t have to wait 30 years šŸ˜‰

Now… how about some clear skies?

 

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 lavaā€¦ wellā€¦ a sea of frozen lava is still a sea, isnā€™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 Sunā€™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.

Just One Hour

May 5, 2024Richard WrightAstrophotography, Basic Photography

The August, 2024 issue of Sky & Telescope has an article by me about shooting star trail images. It’s too bad I didn’t have this shot before because it’s my favorite star trails image to date. I setup my camera behind an equatorial mount (I was shooting M106 at the time), and set my canon EOS Ra to take 30 second exposures repeatedly. Then, as I describe in my afore mentioned article, I loaded all the images as layers in Photoshop and set the blend mode to “Lighten”. I did paint out a few airplane trails in the individual layers, but otherwise the image is accurate. There are even a few short meteor bursts if you look carefully for them.

Star trails over a telescope
One hours worth of star trails show just how much the stars appear to move in such a short amount of time.

This image shows why we use an equatorial mount for long exposure astrophotography. As the Earth spins, the stars move considerably, and in this case you can see exactly how much in only an hours time. An equatorial mount works by aligning it’s axis of rotation with the Earth’s, and then rotating in the opposite direction of the Earth’s motion. It’s like being on a merry-go-round, and you have to turn your head to keep looking at someone or something off in the distance. Without an equatorial mount, objects zip by in the eyepiece or camera pretty quickly. There are also alt-az mounts that track objects in the sky without having to do much alignment work, however, because of the way they move, objects in the camera will rotate in place as you track them across the sky. This makes long exposures a bit more challenging šŸ˜‰

For context, I’ve added just a single 30 second frame as well. As a stand alone image, it’s not too bad either IMHO.

Richard

A telescope against a starry sky
Here’s just one of the 120 frames used to create the star trails image.

Totality at Last!

April 23, 2024Richard WrightAstrophotography, Eclipses

Total Eclipse SequenceYouā€™d think given my years of astrophotography (if not just my age!) that by now Iā€™d have seen a total eclipse. The total eclipse of April 2024 that crossed North America was not my first attempt at a total eclipse, but it was my first successful attempt at witnessing a total eclipse! I can now tell you; the hype is real.

The Diamond Ring Effect
The Diamond Ring at the beginning of totality during the 2024 total solar eclipse.

I went to the Texas Star Party, which was moved both in location and time to coincide with totality and we were nearly right on the center line for nearly four and a half minutes of totality. That was the fastest four and a half minutes of my life. I can now understand why people tell you that you should not ā€œfocusā€ on astrophotography at your first totality. Of course, that advice is lost on me (and probably some of you) because photography is in our DNA. I did not however completely ignore the advice. My photography rig was 99% automated. All I had to do was remove the front white light filter at totality and put it back on after totality.

My gear choice was pretty much ideal. I used an equatorial mount to keep the Sunā€™s orientation constant throughout the eclipse (Sky-Watcher Az-EQ6 in EQ mode). I polar aligned it on a previous evening using the integrated polar scope. For optics, I used an Astrophysics Stowaway 92mm refractor with the f/7 flattener. I had made a front mounted white light solar filter from Baader solar film for the 2017 eclipse that I reused this year. I

Total Eclipse
The Sun and Moon during totality. Note that bright prominence at the bottom just peeking through low areas on the lunar limb.

removed it during totality, and thus got nice safe images of the partial phases, and when it was safe (for the camera) I got Baileys Beads, the Diamond Ring, and some great prominence and corona images during totality. The camera was a Canon EOS Ra mirrorless full frame camera. The ā€œaā€ means astronomical as it is slightly more sensitive to the hydrogen alpha wavelengths of emission nebulaā€¦ and as it turns out, solar prominences!

Finally, the software the drove the sequence on my MacBook Pro was ā€œCapture Eclipseā€, which is a great program I canā€™t recommend enough. I rehearsed at home of course, and I focused using the @focus3 algorithm in TheSkyX Professional (which I wrote btw) on the sunspots right before the eclipse started. The telescope was already at equilibrium, so there was no focus drift during the eclipse.

Prominences on East side
Prominence’s on the Eastern limb of the Sun. Note the rather large triangular prominence at the bottom. This was visible to the naked eye during the eclipse.

I must say, I really lucked out. Sure being prepared helps, trying repeatedly helps, but the weather forecast shifted from seasonal norms to mostly cloudy for eclipse day. We got fortunate that the clouds parted for us and although we had a few thin clouds and the occasional thick cloud, we were rewarded with a glorious view of totality. While Iā€™m very pleased with my images, there is absolutely no comparison to the view naked eye. If you can possibly make it to center line for a total eclipse, I highly recommend you make the effort. I know my passport will be ready for some future eclipsesā€¦

Additional and larger versions of these photos are available in the Sun gallery. My favorite shot of Baileys Beads is below!

 

Baileys Beads just before totality ends. These are caused by sunlight filtering through gaps in the lunar terrain like mountains, valleys, and craters.

A Tale of Two Filters

March 2, 2024Richard WrightAstrophotography, Solar Imaging

Like a lot of photographers in North America, I’ve been making preparations for the total eclipse coming up in slightly over a month now from the time of this writing. I’m planning to take an arsenal of solar gear and spend a couple of days doing solar imaging with a variety of gear and techniques, and fleshing out some software I’m working on for lucky imaging to boot. This means I’ve been doing a lot of solar viewing and imaging in my back yard, and cycling through gear to make sure I have all the right adapters, spacing, etc. There was a very active region on the Sun (AR 3590) on the clear afternoon of February 27th and I had a chance to image it in white light and then just a few minutes later in Hydrogen Alpha. The difference is quite stark and I thought very illustrative.

Two images of AR 3590
Active Region 3590 in Ha and white light.

The telescope was a Sky-Watcher Esprit 150 (still my favorite optic for just about anything), which I had on my Paramount MX+. The Paramount’s have the smoothest motion of any mount I’ve ever used for any kind of high resolution Solar or Lunar work, but back to topic. The top panel at right was taken with a 4x Powermate to get the image scale and focal ratio higher for the Daystar Quantum hydrogen alpha filter. I used a Player One ERF (Energy Rejection Filter) in front of the PowerMate. I don’t use a big ERF in front of the 6″ objective, but 6″ is about as large a refractor as anyone should dare use for solar without a larger ERF in front of the aperture. The camera on the back was Player One Apollo Max, and I shot about 5,000 frames, of which I used 20% for the final stack. The original image was monochrome, but I colorized it as most people (my wife especially) prefer to see a nice color image. The mad truth is the single wavelength of Ha is an electric pink, but the convention is to make these images yellow to conform with the public’s perception of what color the Sun should be.

Ha images are stunning. They show in stark relief how the gasses are flowing along magnetic field lines on the Sun’s surface. The darker areas are still quite hot and blindingly bright, but they are just ever so cooler than the surrounding areas, and the white areas are as you’d expect super hot and bright.

The bottom image was taken with a Starfield Herschel Wedge. A Herschel Wedge is a lot like a normal star diagonal you see on many telescopes, but it let’s the majority of the Sun’s light pass through it out the back. A tiny portion is reflected up towards an eyepiece or camera for viewing. It simply dims the Sun, so you see the Sun as it actually appears, just a lot less bright and hot. Not using a filter like this would blind you instantly, or melt your poor camera before you could hope to get a shot off.

I still used a 4x PowerMate and the monochrome Player One camera, but replaced the Player One ERF (which is tuned for Ha imaging) with a standard UV/IR filter. The Herschel Wedge does not need this normally for visual work, but when doing photography, it eliminates some of the stray light that would be out of focus. The result is a “White Light” image of the same region. You can still see some of the same overall structure of the region, but you are not seeing the effects of the magnetic field lines that are more pronounced in the hydrogen bandpass.

The true color of the bottom image is actually… white. The Sun appears white in space, and even on Earth when directly overhead. It’s hard to tell of course because well, looking at it long enough to study it’s color would of course blind you! Still, I chose to colorize it for aesthetic purposes to match the image above. Scientifically, the images represent the structures accurately (even the limb darkening at upper left is real), but the colors are for taste alone.

I hope you can forgive my creative license (or shameless conformity), and enjoy seeing the difference between these two common ways to filter and view or photograph the Sun.

Bernard’s Merope Nebula

January 1, 2024Richard WrightAstrophotography
Merope Nebula image
Bernard’s Merope Nebula

This was a challenge target for me. Last month I was writing my monthly astrophotography target of the month column for Sky Safari (you will need a subscription to see it in Sky Safari Pro), I realized I did not actually have a good image of the Pleiades that featured this tiny jewel (cataloged as IC 349). I love to shoot the larger reflection nebula with a newtonian reflector because it makes beautiful diffraction spikes, but the spikes would obliterate this tiny little interloper to M45. Same with other refractors (or my Officina Stellare RH-200) I had used with longer exposures – the star Merope would swell up and swallow this nearby nebula, which physically is only 0.06 light years from the star!!

The Pleiades are a relatively bright group of stars and nebulosity, so I went for a short run under somewhat light polluted skies. I used 111 good 30 second exposures stacked for this image, and stretched VERY gently with the histogram and curves tools. The seeing was not super great that night with my Espirt 150 refractor and a Player One Ares-C Pro cooled color camera, so I confess as well I used the very nice Blur Exterminator to tighten the stars a little bit.

An interesting personal experience about this image. This is the first time since I’ve started wearing glasses (none of us are getting younger!), and just like a star test is a good way to test optical flatness, I found that when judging my star field on the computer screen, I could see… and DISTRACTINGLY SO… distortions in the star field that aren’t actually there. This can make it very hard to judge an astro image, and I now have TWO pairs of glasses. One for “most of the time”, and one for when I’m using my computer or working… um… well, truthfully that IS most of the time – LOL.

P.S. Happy New Year and Clear Skies!

Purple Haze

October 15, 2023Richard WrightAstrophotography, Solar Imaging

The great annular eclipse of 2023 has come and gone. The internet and social media are flooded with amazing shots of the Sun. Most are red or orange, and there are a few white light images taken with white light filters or solar wedges. ā€œThe Ring of Fireā€ was not in the cards for me this year, and I had to be content to observe and image the event from my driveway in Central Florida. I shared the event with neighbors and gave away some solar glasses from DayStar filters. No eyepieces though, I had a camera on the back of the telescope (oh, did this require some ā€œexplainingā€ and warnings), and a black and white image of the Sun was displayed on my laptop, cleverly shielded from the hot bright sun by a cardboard moving box.

Solar Eclipse in Calcium Light
Maximum Eclipse from Central Florida in Calcium-H light

My processed images though are Purple. Whaaat?!

I used a Daystar Calcium Quark, specifically the Calcium-H line. Some of you know this, but many people do not know that much of what we know about the Universe and what things that are far away are made of, is done by studying the light we receive from them. Hereā€™s a great article on the Hubble Space Telescope web site that explains some of how this works: What is Spectroscopy.

So, back to the Wright Earth Telescope(s). The filter I used on the eclipse is what we call a ā€œnarrowbandā€ or ā€œLineā€ filter. It only letā€™s through a very specific wavelength of light, and this filter is tuned for the H line of Calcium (396.9nm), which if you had looked at it through an eyepiece, would have been a deep purple! I once had a similar dedicated telescope that was for the Calcium-K band, which also appears Purple, but is so deep that many people cannot actually see the details on the Sunā€™s surface. Iā€™ve heard various explanations about genetics, and ā€œold peopleā€. My own experience is that I could see it years ago, and now when I first look all I see is a smooth purple disk. Then as I fish around, my eye will suddenly focus and I can see it for a few seconds, and then itā€™s lost. I donā€™t think itā€™s so much ā€œdetectingā€ the wavelength (which is very far towards the violet), as your eye loses the ability to focus on it. Maybe thatā€™s the same thing. Weā€™ll see if in another few years if I can ever catch the surface details any longer.

But this is why the Calcium-H line is very popular for visual solar observing. It reveals a very similarly detailed image and can be more easily seen visually in an eyepiece. Since itā€™s monochromatic light (just a single wavelength), typically what imagers do is use a more sensitive monochrome camera, and then colorize the image after they are done processing the image for sharpness and contrast.

The Gear

Telescope pointed at the Sun
Driveway Solar Astronomy. Be sure and share with your neighbors

I used a Sky-Watcher AZ-EQ6 mount in Alt-AZ mode. That was more mount than needed for my tiny Takahashi FS60-CB telescope. It has a fluorite lens, and many people worry about damaging fluorite with solar observing. It is true, fluorite lenses can be damaged by sudden temperature shifts, but hereā€™s the thing about glass lensesā€¦ light passes through them. They donā€™t really absorb much heat. If your optic however gets too far off the Sun, and the concentrated light starts hitting your baffles or the edge of the tube, you can superheat the inside of the OTA, and bad things can happen. Bad things. I do understand some older oil space lenses can be problematic for solar though, so check with your manufacturer before you start tinkering with hot sunlight.

Inside the tube, I had an IR/UV filter, which reflects a great deal of the Sunā€™s invisible, but heat bearing wavelengths right back out the front of the telescope. Behind that was an Astrophysics 2X barlow. I love this barlow because it also acts as a flattener. If you are doing full disk solar work, or even high resolution solar or lunar work, it annoys me terribly when I use a large sensor and only the middle of the image is really in focus. The solar filter was the Daystar Calcium-H Quark and the camera was Player One Ares-M (IMX 533 monochrome) that I ran cooled to zero degrees C. This was a lot of fun to explain to the neighbors. Concentrated sunlight is going through a filter heated to a specific temperature, that then reaches a camera that is cooled and kept at 0 degrees Celsius. Iā€™m just your average mad scientist working in his drivewayā€¦

Clear skies, day or night friends!

A Celestial Dolphin

July 28, 2023Richard WrightAstrophotography

Here’s a “cool” looking image for all the hot summer days we are having right now! A really amazing object in the southern sky in the constellation Canis Major (the Big Dog), is a big gas bubble cataloged as Sharpless 308. It has a popular (but unofficial) name of the Dolphin Nebula. It’s in the Sharpless catalog because of it’s Hydrogen Beta emissions, but it is especially bright in ionized Oxygen III. This image is about two hours of exposure time through a 3nm Chroma OIII narrowband filter. It’s amazing that we can photographically identify elements this way, but the OIII atoms emit a very specific wavelength of light, and this filter let’s only that wavelength through (well, plus or minus 1.5 nanometers!).

The Dolphin Nebula
Sharpless 308, or the Dolphin Head Nebula

The central star is pre-supernova and is responsible for blowing off all this gas, and is about 4,530 light years from Earth.

Artistically, this was a tough image for me. I took it back in February of 2023 at the Winter Star Party and only now (late July) am I satisfied to publish it. I did take about 1/2 hour of RGB data to give the stars color, but this is basically just an Oxygen emission image of this target. I went back and forth on the coloring. OIII is Cyan (blue/green), but of course the light is far too dim to see. What color is something that’s invisible? I settled on this, and finally even decided I liked the smoky background oxygen that is glowing around/behind the main focus of the image.

Gear used:
Sky-Watcher Esprit 150 refractor
Night Crawler Focuser
Player One Poseidon-M Camera w/Phoenix Filter Wheel
Chroma 3nm OIII narrowband filter
Software Bisque Paramount MYT
30 minutes RGB exposure time
2 Hours OIII exposure time