A Tale of Two Filters

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

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

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. “The Ring of Fire” 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 “explaining” 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. Here’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 “narrowband” or “Line” filter. It only let’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 Sun’s surface. I’ve heard various explanations about genetics, and “old people”. 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 it’s lost. I don’t think it’s so much “detecting” the wavelength (which is very far towards the violet), as your eye loses the ability to focus on it. Maybe that’s the same thing. We’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 it’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 here’s the thing about glass lenses… light passes through them. They don’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 Sun’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. I’m just your average mad scientist working in his driveway…

Clear skies, day or night friends!

A Celestial Dolphin

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

You can now find me on SkySafari Pro!

Featured Story image of M13
SkySafari "Tonight"
Click “Tonight” from the toolbar to see featured items.

I’m three months late with this post, but I’ve started writing a monthly feature/blog for SkySafari that is available to their premium subscribers! Each month, I’ll be calling out an astrophotography target for that month and talking a little bit about the object itself and some general tips for astrophotographers. SkySafari is available for both iOS and Android and is one of the most popular (if not the most popular) mobile astronomy apps. You can use it to find or identify objects in the sky, get notifications about astronomical events, and configure your telescope/eyepieces/cameras to plan viewing or imaging sessions. It also controls a great number of telescopes and has a huge database of objects you can search.

This month I’m talking about my favorite target visually, which also makes a pretty nice astrophotography target, M13 (Messier 13), or the great globular cluster in Hercules. Past articles are also available. Last month was the large galaxy M101, and before that the Leo Triplet of Galaxies. It is “Galaxy Season” after all. Each month, I’ll focus on a target that is ready to go at evening astronomical twilight (when it’s dark enough to image deep sky targets). It’s going to be a very long time before I run out of targets to talk about, and I hope you will check it out and enjoy!

If you have SkySafari 7 Pro and already have a subscription to the premium features, just click “Tonight” on the bottom toolbar on your mobile phone or tablet.



Winter Star Party 2023

WSP Welcome Image

The annual Winter Star Party in the Florida Keys is my favorite annual event, always held in February or occasionally in very late January or early March. It’s almost a religious pilgrimage for me, and I’ve only missed once in 20 years since I started attending, and that was due to a death in the family (I was already packed and loaded when I got the worst phone call of my life… but that’s another story).

Morning Milky Way
Earth clouds on star clouds. The Summer Milky Way makes an appearance just before dawn.

What’s so special about the Winter Star Party, or WSP? I think it’s the location and of course the people. A star party is after all a social event, and I have met many lifelong friends at WSP. It’s currently held at adjacent girl scout and boy scout campgrounds on “Scout Key”, south of Marathon, but sill 40 miles from Key West. The girl scout side has been ravaged by hurricanes and is a bit more of a primitive camping experience. The boy scout side however is well manicured, has power, a clean and modern bath/shower facility, and even “glamping” tents with AC. Yes, both sides have been hit by the same hurricanes, but the boy scouts have built back. It’s never too late to teach our children that the boys have all the money and get the nicer things… (that’s sarcasm btw… or an indictment, take your pick).

Omega Centauri Image
Hands down, my favorite WSP image visually or photographically is the great globular cluster Omega Centauri.

There is light pollution from the keys of course, so it’s not “Okey-Tex” dark skies, but the view to the South is dark, and only with a long exposure (with a camera on a tripod) can you see a small light dome on the horizon… from Havana Cuba! The southern sky is a treat, among my favorites, there’s Omega Centauri, the king of globular clusters, Centaurus A, an amazing irregular galaxy, and if the weather gods show favor — the great Eta Carina nebula will make an appearance, no more than 6 degrees above the ocean’s most southerly view.

Centaurus A Image
Centaurus A is a peculiar galaxy and one of my favorite WSP targets.

The keys are a special place too. I live in Florida, but I live near Orlando and the “attractions” are only an hour away. The Florida Keys are almost like another state entirely. Tropical beaches, the vibrant blues and green of the ocean, tiki huts, and seafood galore. People from all over the world come to my part of Florida on vacation. If you live here, going to the Keys is where we go on vacation. There’s plenty to do in the keys too for your non-astro-nut family members. Key West is also a whole other world in itself. You can rent a boat, go snorkeling, kayaking, fishing, the list is endless.

Epic Dew
Soaking wet dew graced us the last clear night of the star party.

This past year was my first year in nearly two decades that I did not attend as a vendor representative, and the first held in three years due to cancelations over the Pandemic. The weather was clear, but windy most of the week, and the smart astrophotographers found places in the lee of the wind. I managed to get some good deep sky data, and even did some lunar and solar lucky imaging.

The last clear night was Friday, and the air was still, and heavy with dew, the worst dew event I recall at this event. I had not prepared for this, and my scope dewed over immediately after dark. I put on a dew strap, cranked it up, and used an alcohol wipe to repeatedly remove the moisture. It took about 45 minutes, but finally I was back in business and got my best image data of the week that night. In fact, I hit the celestial jackpot that night.

Eta Carina Image
Not too bad for only 40 minutes worth of time between 4 and 6 degrees above the horizon!

Early in the morning a friend behind me was “observing” Eta Carina, only about 4 degrees above the horizon. I thought, “well, why not”, and I tried a slew and a single exposure. I expected it to be behind a tree, or below the berm between me and the beach. Surprise! It was not well centered, but it was there, and it was bright! I carefully centered it and found tracking was not that great so close to the horizon, but I could take decent enough 15 second exposures. So, I took 156 of them before a tree did in fact obscure my view! I alternated between red, green, and blue with my monochrome Player One Poseidon-M camera and managed to pull off a decent enough image. One day… I MUST travel south of the Equator to do this target justice.

In the meantime, I’m counting down the weeks until my next “Latitude Adjustment” in February of 2024. See you there? Stop by and say hello!

First Light with a Player One Poseidon-M

Image of Player One camera
Image of Player One camera
I think we are going to make beautiful music together….

I plan to do a longer and more thorough report on the Player One Poseidon-M camera at a later date, I’ve only just received it recently and have had a spotty few nights out with it, but I’m pretty impressed so far. I ordered a full set of Chroma filters for it, and my first clear night the only filter that had arrived was a 3nm Ha (Hydrogen Alpha) narrowband filter. The Moon was up and well, Ha is great in the moonlight, and I could not wait to try the new toy out.

Well, who doesn’t shoot M42 when they get a new camera? It’s bright, it’s pretty, and it’s loaded with glowing hydrogen gas — I have a shiny new camera and high quality 3nm hydrogen filter. I wanted to see how much detail I could get out of the trapezium, which is the very bright core of M42, so I experimented to see how long I could go without saturating that region. I was shooting at high conversion gain (HCG), but could go a full minute and still make out the four stars of the trapezium. The screen stretch showed glorious detail already and so I decided one minute was enough.

Hydrogen Alpha image of M42 region
Who doesn’t shoot M42 when they get a new camera?

Orion passes between two trees from my backyard each night, and I only got 104 of these one minute exposures over two nights, but it was quite enough for an impressive image non-the-less of the entire region. I would have liked to get more to reduce the noise in the outer areas, but it is definitely good enough for the internet as is. One minute narrowband subs (oh, this was at f/7 by the way) is pretty impressive, but I have to admit, M42 is a pretty bright target, so I tried a few others also at shorter exposures.

Tadpoles in Ha
Tadpoles are a must image with narrowband filters.

I did some one and two minute exposures on the Rosette and the Tadpoles and stacked equivalent spans of time for each. The one minute stacks did not suffer from what I could tell from a qualitative inspection vs. the stack of two minute subs (both stacks of about half an hour).

I also did 162 x 60 seconds on the Cone nebula region. The screen stretch of the individual subs was very faint on this region, but the stacked result was quite spectacular I thought. The fox fur region is just loaded with detail and subjectively I’d say it’s every bit as good as what I used to do with CCD’s and longer (individual exposures).

Rosetta nebula in Ha
A very popular target in Ha, the Rosetta nebula does not disappoint.

I’ve been speaking about the new age of shorter exposures for a while now, but I’ll abbreviate my thesis in that shorter individual exposures are becoming more usable due to camera improvements, but the total integration time for a quality image has only diminished very slightly due to increases in QE (Quantum Efficiency). There is still only so much light coming from astronomical objects, and it still takes hours of total integration time to create a very high quality image. These images look great on the web, but if I were to print them or display higher resolution versions, I’d want a little more integration time to better smoothen them out (from shot noise).

I plan to push on this camera pretty hard, do a lot more experiments (both qualitative and quantitative), write some software, and take some pretty pictures. Stay tuned…

Cone nebula region
One minute Ha subs at f/7. Individual subs were pretty faint, but 162 of them turned out quite nice!

Oh, and if you can, be sure and catch my talk on “The Future of Astrophotography” at the upcoming Winter Star Party, or you can read a reprint of my August 2022 Sky & Telescope article “The Next Big Thing” here.


Our daytime star

I’m continuing my exploration of “lucky imaging” of the solar system objects, this time with the Sun. A special filter made by DayStar allows only a very narrow wavelength of light through when observing the Sun that is emitted by hydrogen gas. You can see in this image how the gas is swirling around on the Sun, cooler areas (not COOL, just cool-ER) manifesting as sunspots, and of course a few prominences on the edge of the Sun proper. The Suns surface was taken with very short exposures, and the prominences were taken at a slightly longer exposure that causes the surface to just appear solid white. So the two were merged to show the entire view. This is a good example of what we space photography nerds call dynamic range. The full range of brightness in this image can’t be captured by a single exposure length as the camera doesn’t have that much range. Well, truth is, many people do pull that off, and with more practice I may too. For now, two exposures worked well enough for me<g>. Please be sure, this was a very special (and expensive) solar filter. If you turn your Christmas scope to the Sun, you will likely damage the scope, blind yourself, and yes, potentially set something on fire (perhaps your shirt!). Don’t try this at home kiddies, I’m a professional… well, sorta.

Hydrogen alpha Sun
Our daytime star, the Sun in Hydrogen Alpha light.

For some technical details, the camera (a Player One Apollo Max) is monochrome, or black and white. The image was colorized after the fact for aesthetic reasons. I’ve looked through this filter, and Hydrogen Alpha light is a bright electric pink. It’s only a single wavelength of light, and there’s no point in using a color camera. I matched it in Photoshop… but, man it makes for an ugly picture! Other details… Sky-Watcher USA Esprit 150 refractor with a Televue 4x Powermate to get the focal ratio where it needs to be for the special filter I used (rays of light to the filter need to be pretty direct on and not slanted like at faster focal ratios).

As far as processing goes, I’m getting traction, but I can critique several things about this image. Truth is though, I’ve reworked it a few times already and am ready to apply what I’ve learned now to my next image. Rest assured…. there is ALWAYS a next image.

Fly me to the Moon

A closer view still
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.

A closer view still
A closer view by two of the lunar southern highlands.

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.

Southern region labeled
The craters Moretus, Newton, and Casatus.

To the MOON!!

Read with Sean Connery’s accident, “You call this astrophotography?”

Happens to me all the time… on the space coast. I am quite fortunate to live an hour away from the Kennedy Space Center, and I can see most launches from my yard when the weather is good. Sometimes though, you just have to drive over, and not since the last time I drove over for a night Shuttle launch have I seen something so spectacular as the launch of Artemis 1. The Moon has always been my first love of the celestial realm, and since I was a boy I dreamt of walking there one day. I still remember my mother getting me out of bed just shy of four years old to see the broadcast of Armstrong on the Moon. My father acted like it was the greatest thing ever, and it left an impression on me to this day. I plan to be there too when mankind (and this time a more diverse crew) again launches to the Moon. Godspeed Artemis 1, the precursor to our return to crewed flights to the Moon!!

Oh… and I got an extra bonus. I caught what I’m pretty sure is a NASA helicopter monitoring the launch, or it’s silhouette in the bring light of the launch. It had no running lights, but it’s as plan as day when you spot it in this photo! It’s astonishing how recently even a helicopter would be considered a fantasy, and here we are going to the Moon AGAIN!

Artemis 1 Launch
Back to the Moon! And watching nearby, see if you can spot a helicopter monitoring the launch.