Imaging Planet X: Is It Possible?

The news is that there may be a ninth planet. It's being called "Planet X" for historical reasons, with the X designating "unknown" rather than the number 10. It gets a planet designation because even though this inferred object probably resembles a trans-Neptunian object it's thought to be be bigger than Earth.  (Please don't confuse it with the utterly fictional "Planet X" known to some as Nibiru.)

The ex-planet Pluto is easy to image as are many of the other dwarf planets; what about this new denizen?

Factors that dictate a planet's total brightness (as opposed to its surface brightness) are its distance from the Sun and from us, its average albedo, its size, and its phase. In the case of these distant objects phase is essentially always full and can be ignored; likewise the 2 AU annual change in the distance from Earth is neglected. To keep this simple I'll make a comparison between X and Pluto to estimate the former's relative brightness and magnitude.

Lets's start with some simplifying assumptions and say that X and Pluto have the same albedo and that X lacks a moon that contributes significantly to its brightness. (Charon represents about 1/5 of the Plutonian system brightness--if Pluto were to become invisible Charon would be easily imaged!)

So what are the speculated physical characteristics of X?

Size: Larger than Earth, smaller than Neptune. If it's simply a scaled up version of Pluto with 4500 times the mass, it should be about 16 times the size of Pluto. this puts it about 2.8 times the size of Earth and about 73% the size of Neptune. Close enough. This gives X a reflecting cross section about 256 times that of Pluto; we'll knock that down to 200 to account for its assumed lack of a bright moon.

Orbit: There's a lot of uncertainty here; the suggestion is that as X's orbit caries it between 200 to 1200 AU from the Sun. Unfortunately no one knows it's present distance, so we'll make estimates for both the extremes. At present Pluto's distance to the Sun is about 33 AU and it's magnitude 14.2. The distance factors are (33/200) to the fourth power and (33/1200) to the fourth power for perihelion and aphelion, respectively, using the assumption that X will resemble a point source such as a star.

Perihelion: 0.148 the brightness of Pluto, giving it a magnitude of about 16.3. This is easily within the range of amateur imaging.

Aphelion:  0.000114 the brightness of Pluto, with a magnitude of about 24.1. This is probably beyond amateurs. The deepest stars I've ever imaged are near magnitude 20; X would require a total exposure time about 40 times greater than that for a 20th magnitude star to image at its most distant point.

That perihelion magnitude is encouraging, but there are complications. Not much is known about X's orbit, so even if X is near perihelion we don't know were to look for it. Given that its orbit is probably fairly eccentric it will usually be found closer to aphelion, and therefore is usually very, very dim. And don't even think about waiting for the next perihelion, the orbital period is many times a human lifetime.

My recommendation is to leave X to the professional deep sky surveys. On the other hand, if you're feeling really lucky and have a whole lot of time, you could be the next Clyde Tombaugh.


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It's been a miserably cloudy winter here. I've had only one night out to image, and that was to try to catch Barnard's Loop. Overhead power lines and a neighbor's lights really degraded the image.

Barnard's Loop (in hydrogen alpha)

 As you can see, above and left of center there are diagonal artifacts thanks to the power lines and at lower right, air traffic. Too much signal was lost trying to reject the obstructions. If the weather improves I might get another chance this winter.

November 2015, A Great Month for Imaging

Pleasant fall weather and clear nights are the dream for every autumn, and occasionally that's exactly what happens. This year's September, October and November allowed me to image on 15 nights (or more, I may have missed a counting a few). And that's not counting a few clear nights during full moons when lunar observers were probably having fun. I did some work on the Arp and planetary nebula observing programs, and made time for a pretty objects as well. Here are a few of this autumn's images:

Messier 33, Canon T2i and AT65EDQ

Messier 45, SBIG ST-8300M LRGB and AT65EDQ

NGC 246, SBIG ST-8300M RGB and C 9.25

I really like the way the Canon and AT65 work together to make for light-weight, large field imaging. The previous (and only) deep image I'd done with the T2i made me wonder about how noisy the camera was, but the M33 image background came out nice and smooth, probably aided by the temperature being in the 40s F.

Winter's here now it appears. Temperatures are in the teens at night and there's an inch or two of snow on the ground with several more inches in the forecast.

My winter goals this year are modest compared to last year when I was in a mad rush to complete the bright nebula program. A nice narrowband image of Barnard's loop would be nice, and perhaps if the conditions cooperate one or two of the big winter nebulae with the Canon/AT65.

Two little wiring projects are planned, too. I want to replace the cord on my CGEM's handset with a longer flat cable and make a 12V to 7.4V power supply for the Canon.

Plans are afoot for club members to gather for an imaging SIG meeting and mirror making seminar in January or February. I hope to attend both.

I'm Still Learning How to Process Images

One of my friends is getting back into imaging after a few years doing other things during which he forgot a lot about processing. To help him get back up to speed I've been building a rather terse guide to processing.

I know, I know. It seems like every imager eventually ends up putting together a tutorial or guide. It's not like I'm a keeper of the Secrets of Imaging. I'm stretching credulity to call myself an intermediate skill level imager; it's a joke to use my name and APOD in the same sentence. You get the idea.

There's nothing like writing things down to demystify them and perhaps once and for all learn them. I started by outlining my usual slap-dash processing workflow, and now I'm improving it with some better processing methods and tools I've found roaming the web. This is a proverbial work in progress, so it will grow in time. So far I've only worked on one-shot color and RGB three-channel imaging, but I hope to add some LRGB information shortly.

To give you a look at what some simple processing can do for an image, compare this image of M51 processed in April with an improved version making use of a few of the things I've learned.

Left, as processed in April. Right, with a few improvements

Lots of excuses: The data here are poor, there were only dark and bias frames for calibration, the telescope was very badly collimated. The left image gives you an idea of where I was at only six months ago--it was the best I could do. The right image employs a synthetic flat created by applying median filtering, Gaussian blurring, and masks in Photoshop CS5. Also applied is a high-pass filter, but it doesn't add much because I had already mucked up the image with an Unsharp Mask. Lastly, flatting out that icky background has allowed me bring out the colors that had been hidden. That was done with curves in lab mode.

It's far from perfect--that strange magenta star to the left of the galaxy vexes me--but it's a light year or two better than it was.

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What I lack in processing skills I counter with determination: I've finally bested the Astronomical League's Bright Nebula Observing Program (imaging option) and have been awarded certificate #9 (advanced). I ended up imaging 103 objects. Some of those images are going to get reprocessed in light of my improving skills.

A Big Night for Arps / A No-Show Star Party.

Tuesday night (10/6-7) was a nice night for piling up some Arp objects. Nothing really pretty here as I went for quantity over quality. Each object was given about a half hour of luminance using my C 9.25 operating at f/6.0. Here are the results:

These are presented cropped and scaled by 0.5X.

Tonight is the MAS's Fall Mini-Messier Marathon. It will probably be clouded out, but the alternate night (tomorrow) looks like it will be nice and clear. I plan on attending, not to do the marathon but to take a pretty picture of the Helix with the C 9.25 again at f/6.

I'm running at f/6.0 instead of the f/6.3 because after playing around with the focal reducer / sensor separation, I prefer how the images have come out at the slightly faster setting.

The No-Show Star Party of the title is the Eastern Iowa Star Party. I had planned on attending, but was unable to get any information from the hosting club other than the date and location. It's nice to know about things like amenities (AC Power, facilities, and fees are a few that come to mind.) before driving 5+ hours to attend. I strongly suggest to the QCAS (the Quad Cities astronomy club) that they post some information useful to potential attendees a few months before next year's EISP. So far as I was able to tell, they didn't post the party's date until less than a week before the event. If they want the party to maintain itself they need to get more information about it into public view in a more timely way.

Moonlight Imaging (broadband version)

Two months ago I wrote about how one could narrowband image under moonlight. Actually, you don't have to use narrowband filters to image with a full moon in the sky. But you do need to choose your targets with a thought to where the moon is. And it helps to have a haze-free sky that's otherwise fairly dark--yellow zone at least.

Here was the situation the night of the 26th: One night before the "supermoon" total lunar eclipse. The moon's magnitude was a brilliant -12.6 and at meridian crossing reached an altitude of about
42 degrees here in Minneapolis:

The Moon on the night of 9/26/15 at meridian crossing

This shows the part of the sky with an altitude of over 30 degrees. It's not going to be good imaging in Pegasus, but going further north things get better. Polaris is about 48 degrees from the moon, and if we can find something between that and the northern horizon it might be worth a shot.

So I chose objects that were on the northern side of the zenith well away from the moon and close enough to the celestial pole that they'd be available all night. And I imaged from a darker site than my backyard in the inner red zone. Here's how it turned out:

NGC 2276 (Arp 25) and NGC 2300 (Arp 114)

NGC 0040

Not too bad, really. I imaged at f/10 because these are small targets and partly in the hopes it would help contrast. The galaxies were imaged in the time before midnight and the planetary after followed by dark frames. As it ended up I was out there until after 4 A.M., but a clear night is not exactly a common event this year and I wanted to take full advantage of it.

Note that exposure times were kept short because of the moonlight. Unbinned luminance frames were only 180s and 2x2 binned RGB frames were a brief 90 seconds. As it was I got about two hour total exposure time for each image.

After three hours of sleep I went home the next day, to bed at 7 P.M. and slept right through the lunar eclipse. Imaging has a  price!

When To Go Off-List

It's possible to get caught up in an observing list and work on it to the exclusion of everything else. That's pretty much what I did while working on the Bright Nebula list, particularly when I got to the point of having a dozen or so items to go. Everything was dedicated to completing the list to the point that it dictated what gear would be used at star parties and how my time would be spent.

Perhaps a saner approach is to slow down and mix in non-list items for imaging along the way. That's what I did the other night, and it worked out well.

Lately I've been traveling to a friend's home north of the Twin Cities and we've been observing and imaging together. His sky (suburban-rural transition) is much darker than mine (inner red zone urban) and his gear is definitely better than mine and mounted in an observatory. I set up just as if I'm at a star party, polar align, and get to imaging. Then I'm free to help him while he works on reacquainting himself with the process of imaging--he's been inactive for several years--or hunts down deep sky objects with his 16" go-to Dob. It's the best of both worlds for me to have the benefit of his sky and telescope.

And just as at any star party, it's nice to have someone else around to talk to.

Plus at 4 A.M., I have a nice soft sofa to crash on instead of a tent!

Last Sunday was my latest trip to his place for imaging, and we succeeded in getting his imaging system working for the most part. His autoguiding wasn't working, but he's implemented a fix for next time based on what I use.

I had no specific plans for the evening other than imaging Arp galaxies for that Astronomical League list and maybe during the A.M. of switching to a planetary. My friend had his own list of favorites he was eager to observe using his big Dob and we looked at some of those. About the time I was wrapping up with my second Arp he mentioned NGC 891 and showed my his first light frame. In case you don't know 891, it's a large edge-on galaxy in Andromeda. It's cut in half by a dark dust lane dotted with bright knots and has a rather large and distinct nuclear bulge. In other words, it's pretty.

To some extent imaging is all about pretty, and after all the "bright nebula" imaging in monochrome I decided I wanted to make an image in color. My friend's suggestion of 891 is all I needed to drop my list plans for the rest of the evening and try to make something pretty. Here's the result:

NGC 891

(Details here at Astrobin.) Not a perfect image, but I'm happy with it, and glad I opted to give it a try instead of doing more list imaging!

The early imaging was mundane Luminance only. The target galaxies were so small that color was basically a waste of time. Here's what I mean:

NGC 7550 (Arp 99, Hickson 93)

NGC 7578 (Arp 170, Hickson 94; Note the plate solving error)

These two bring my Arp count up to 12 compared to my planetary at 13. I'll probably add a couple more monochrome Arps next time out to make the lists even in terms of percent completed and then go off-list again!

Celestron Field Flattener Follow-Up

This is a follow-up of a previous post.

I was able to image the other night with the short nosepiece. Recall that my goal was to get the system to match the presumed optimal f/6.3. It was f/6.0 with a long nosepiece/adapter in place, and by switching to a simpler nosepiece it allowed me to trim about 8mm off the FR/CCD separation. While the image is not very good, it's good enough to allow astrometry.net to plate solve it and calculate the pixel scale.

Here's the image:

NGC 7625 (small galaxy at center)

This was based on 30 minutes total exposure for each RGB channel, under near-urban sky. It could be a lot better, but sometimes one must take what the sky and gear gives.

The pixel scale is reported to be 1.51 arcseconds per pixel. This is really close to the value of 1.50 that corresponds to a focal ratio of 6.3--the error is only about 2/3 of one percent.