Tag: Stars at Home

My First Wide Field Astrophotos

After the encounter with the Pretty Good Comet of 2020, F3 NEOWISE, and not getting any good pictures of it, I got it in my head to get DSLR camera so I could do wide field astrophotography. That means wide shots of the sky that look sort of like what you see with your eyes, not a closeup through a telescope. The idea wouldn’t go away, even though the comet did. So I set out to find something used and useable that I could afford, something that would be good for a beginner and with enough capacity to grow with me for a while. After a few weeks of research and shopping online, I found a Nikon D3100 body in great condition for what seemed to be a reasonable price. After a misfire, I found an AF-S 18-55mm DX f/3.5-5.4 zoom lens, also in great shape, to go with it, and again for not too much money. So off we go.

My Photographer Cred

My dad used to do a lot of photography as a hobby. He even had his own darkroom, developing his own film and printing his own pictures in black and white. My brother was something of a photographer, too, having got in pretty early on the digital revolution with a Canon Rebel, which my daughter now has. While I’ve never owned an SLR before, being around a couple good photographers gave me a general conceptual knowledge of how they work. Plus, I have used plenty of point-and-shoots and have developed a pretty good eye, I’d like to think. Still, actually using a DSLR, and for a specialized brand of night photography, presents a pretty steep learning curve.

Not Gonna Do It

For one thing, on my first attempt, I found that my camera is finicky and stubborn in low light conditions. Even having figured how to set the aperture wide and the shutter speed long in manual mode, I couldn’t convince the D3100 to actually take a picture it was sure would be bad. This led to a great deal of frustration on my part, causing me to question whether I had made a terrible mistake. I managed not to rage quit and instead resigned myself to discover through further study how to be smarter than my camera. Reading the owner’s manual seemed a good first step, but before too long I got bored and did an interweb search for my problem.

It turns out the “AF” in the AF-S lens stands for “auto-focus,” which the D3100 takes very seriously. This line of cameras performs auto-focusing with motors in the lens rather than in the camera itself as the lens and camera discuss the shot you are trying to take. Consequently, there is a switch on the side of the lens to go between automatic focus and manual focus. When in auto mode, the camera tries to give the lens all the information it can in order to get a sharp focus. If the camera can’t see well enough to know if the shot will be in focus, it won’t flip the shutter. Putting the lens in manual focus mode solves this problem. The camera still boldly announces that the shot is too dark, but assured by the now-manual lens saying, “I got this,” it allows the picture to go ahead, even though you clearly don’t know what you are doing, in its not so humble opinion. Thanks, internet photography forums! You saved me from having to slog through the boring owner’s manual!

And so it was that, having switched to manual focus, I accidentally took a 20 second exposure of the inside of my lens cap. At first I was confused, because, as noted, the camera was still declaring the shot to be invalid. But having heard the shutter flip, I realized I had broken the code. Actually, taking a “dark frame” is an important part of astrophotograph processing, as it reveals any hot pixels and biases and stuff that the camera and lens may have that can then be subtracted from the final product, or so I’m told. I’m nowhere near ready for that level of postproduction yet. Nevertheless, that first unintentional black picture was the start of something wonderful. I hurried outside with my camera and tripod, found a mostly clear sky (not sure how this was allowed, but I’ll take it), and started taking long, dark pictures of the night sky at 1:00 in the morning.

The Pictures

You can see the whole collection except the dark frame >here< (plus all of what you just read), and I’ll put a few in here directly below. I’m pretty pleased with how they came out straight from the camera. Obviously there is so much more that can be done that I intend to learn, but for the first run, this is pretty cool.

Technical

Most of these shots are 25 seconds long, with a couple at 20 seconds. If you zoom in you can tell there is just a bit of a trail on the 25 second stars, but not so much that you notice it much when zoomed out. As expected, the 20 second exposures have less of that effect, but they are significantly darker. I suppose about 20-25% darker. The 20-25 second figure is a product of what is called the “500 rule” that I read about on a number of websites. Divide 500 by the lens focal length to get the max shutter speed without trailing. For certain types of digital sensors, such as the one in the D3100, you have to adjust for the architecture by using 1.5 x the lens focal length. So I was shooting at 18mm zoom, times 1.5 is 27, and 500 / 27 = 18.5. So I was really going too long at 25 seconds by that calculus. Some folks I read recommended more like 8 seconds, take lots of images, and stack them in processing. That’s a lot of work for a beginner. The other option is to get a tracking mount of some sort that would essentially remove the limit altogether. By following the stars as the earth turns under them, you never get any trails. Well, we may get there eventually, but for now I’ll play with the math.

Observing from Home – October 1, 2018

I let three good, warm, clear nights slip by me this weekend. Each night right around sundown, the clouds made a strong appearance, so I occupied myself with other trivial endeavors rather than haul out the astro gear. Later in the evening, each evening, as I took a look outside I found the skies to be clear and inviting, but it was too late to set up. There was also a lot of moon on a couple of those nights, but still. So having missed three good chances to get out under the sky, I was determined for last night. Consequently, I was convinced the clouds would close in. That’s the usual pattern. But I lucked out or was given grace, depending on your theology, and the sky remained clear.

I set up the Celestron Nexstar Evolution 8″ on the pool patio. It’s the first time I’ve had it out since Green Bank in July, so it took some work remembering how to get it all put together right and to attach a few doodads that had been taken off for travel. I got it set up as the stars were coming out, so I was able to get it aligned. Then I got the call in for supper (we eat late around here), so I parked it and went to eat. I got back out at about 8:35, and the sky was still clear! Amazing! Also, it was warm enough that a long sleeve shirt was all I needed for my whole time out. That and my Palomar beanie.

What I saw:

Summary:

My primary targets were the planets, especially Mars. I spent a good bit of time bouncing back and forth between Mars, half way up the SE sky, and Saturn getting low in the SSW. More on them in a minute. From there, a quick circuit of the summer glories near Sagittarius, then on to the ice giants, Neptune and Uranus. After that, Andromeda seemed the logical next target. Then, I employed the “Sky Tour” feature of my telescope, letting it suggest nearby goodies. This was cool, because otherwise I might never have seen a couple of these, and I didn’t have a plan, either. I finished the night with three favorite targets around the Summer Triangle, which was still about half way up in the western sky. As I started packing up the gear, a very bright, green fireball crossed the sky in the SW, lasting a couple seconds! Great way to end the night! I was out from 8:30 – 11:45 p.m. EDT.

Conditions:

Weather: Warm! in the upper 60s, maybe over 70. Humid. No wind to speak of. No moon until after midnight (@20 days old).

Seeing: 4/10 – pretty wobbly, based on [magnification/in. aperture]

Transparency: 5/10 – high humidity, maybe a thin layer of cloud even

Observations:

Mars

I’ve been waiting to see Mars all summer. As it was heading for its nearest approach in July, it was blanketed by a global dust storm that obscured any surface markings. I did get a chance to see it at the Lowell Observatory in Flagstaff, AZ, in August, and the dust was starting to settle. Some markings were present to the patient observer at that point. As for this night, the seeing was pretty poor and the transparency didn’t help, but I managed to push the magnification to 222x with the 9mm Plossl eyepiece. That’s well below the minimum to resolve much (312x for 8″ aperture), but I was able to discern some surface markings in the better moments. According to Sky&Telescope (S&T), the disk was 16″ (arcseconds). There was a band of darkness along the northern hemisphere, and it seemed to double back on itself about halfway along the equator. What was more striking was that the disk was only 89% illuminated (according to S&T) and showed as a gibbous section, like the moon a couple days after full. That doesn’t happen very often with the outer planets, but there it was. There was a slight hint of the southern polar ice cap, but I wouldn’t say I really saw it.

I tried a few different filters with varying results. Red definitely made the dark area stand out more, but it overwhelmed anything else. The yellow filter did almost as much to increase the surface contrast without being as overbearing. Blue should have helped bring out the polar cap, but it seemed just to wash everything out. Just not good enough conditions for much detail.

Saturn

I went back and forth several times between Mars and Saturn for comparison and because Saturn was heading for the trees, but I wanted to see if there was any movement on the surface features of Mars. Any way, Saturn looked a great as the conditions would allow, which is to say, “meh.” Saturn’s disk was about the same size as Mars, but that’s not counting the rings. Using the same 222x magnification as on Mars, I couldn’t really make out the Cassini division in the rings, as the outer ring appeared unusually dark. I attribute this to the poor transparency. With patience, I could see some shadow on the rings near the eastern limb in the rear and some darkening around the north pole. The disk is covering much but not all of the rings. Usually I can make out some color differences on the disk, but there wasn’t much to be seen this night.

The red and blue filters didn’t do much for Saturn other than make the outer ring almost completely invisible. The yellow filter helped with the contrast a little bit, making the shadow effects more noticeable but not much more.

I’ve seen Saturn this summer in my scope, the Yerkes 40″ Clark refractor, the Lowell 24″ Clark refractor, and the Griffith Zeiss 12″ refractor. This night ranked somewhere in the lower half, although my scope at Green Bank ranked near the top. Conditions make a huge impact, regardless of how awesome the equipment. Of course, my 8″ is 80 years newer than the newest of the rest in the list.

M20

The Trifid forgot to show up for work tonight. It’s fairly faint to start with and the poor transparency made it essentially invisible. I know I was on it because of the two stars that sit in its midst.

M8

The Lagoon is always a pleasure with its large open cluster and broad nebulosity. I’ve noticed that the Nexstar doesn’t pick up the nebulosity as much as my Newts, and again, with the poor transparency, only the brightest areas were clearly visible. I admit I didn’t study the view for very long, as I had other things in mind. I think a nebula filter might be a worthwhile investment, though.

M22

The great Sagittarius globular cluster is a real showpiece. It stands up to a good bit of magnification. At 222x the stars were resolving in a layer across the surface, although the underlying multitude were less forthcoming. The cluster filled most of the field of view with dozens of brighter stars in that top layer. The whole this is sort of tick-shaped, but apart from that, it’s a beauty.

Neptune

I’ve been tracking Neptune for about 10 years. By tracking, I mean I try to find it every year or two when it’s in a favorable place. Well, now is the season. Back in 2008 it was near the point of Capricornus and easily visible in binoculars. It has made its way into easter Aquarius, between Lambda and Phi, and I had a hard time knowing which object was the planet. Part of the problem is my tracking was off a bit because of parking the scope during dinner, but Neptune is also really small (S&T: 2.4″) and faint now. I finally found it, I think. At 333x magnification it showed itself to be a slightly nonstellar disk, just barely. I’ll have to go back and try it again.

Uranus

Same thing with Uranus. That is, I’ve been following it for as long as Neptune, and it’s harder to find than it was when I started. It has traveled from under the Circlet of Pisces to just east of o Piscium moving into Aries. Uranus is an easier find than Neptune, being 3.7″ (S&T). It was clearly nonstellar and a very small disk at 333x. I might even have seen a little bit of color? A hint of blue maybe? Maybe.

M31, 32, 110

The Great Andromeda Galaxy is always a treat. Enormous and bright, it extends past the field of view in my 40mm e.p. at 50x, so it’s over a degree (twice a full moon). The conditions cut it down some, but it’s still huge. The western edge has a dark dust lane running along it, so it’s more defined than the eastern. (I think I have my directions right). There is a bright, small core surrounded by this extended “nebulosity” that is a 100 million suns. Other than the hard edge I didn’t notice much structure.

M32 is an elliptical galaxy just off the side of the M31. It’s tiny by comparison, but still pretty good size as visible galaxies go. It has a bright core surrounded by an oval of rich haze. It didn’t appear to be over or in M31 but pretty close.

M110 is another elliptical galaxy to the NW of M31. It appears larger than M32 but looks similar with bright core and surrounding oval. It’s edges don’t look as well defined as M32. It is very impressive as compared with other Messier galaxies, just small compared to M31.

M33

The Triangulum or Pinwheel Galaxy is a large, face-on spiral, but tonight it looked like a large, faint fuzz. I’ve found it easily in binoculars many nights and occasionally seen it naked eye (maybe?), but the conditions were not favorable this time, and it didn’t have much to offer. Hey, we all have off days.

Eta Cassiopeiae

This was the first of the items suggested by my telescope’s computer that I looked at. It’s a double star with two yellow white stars, one significantly brighter than the other. I haven’t done much with double stars, but this was pretty to look at.

M103

Scope called this the Triangle Cluster, I think. It’s an open cluster with several brighter stars that make up an isosceles or maybe right triangle with fainter stars laced back and forth across it. I’m not a huge fan of open clusters, but this one is pretty interesting.

M77

This is allegedly a face-on spiral galaxy. I’ll believe it when I see it. It wasn’t a good night for galaxies, or at least for the faint ones. I can’t swear that I even identified this. There was a ghost in the field of view, just kind of a faint slash, that moved with the field, so I guess that was it.

M34

Another of those open clusters I don’t care much for, except I spent a long time on this one. If I were going to name it, I’d call it the Atlas Cluster. I imagined a bulky figure standing with arms stretching out and up (toward NW I think), legs locked, and a globe on its back. It started with two close stars that serve as eyes and three down the middle for abs. Strands running up and out in curves that define the limbs. It’s a sizable cluster with a couple dozen brighter components shaping the titan character and dimmer stars surrounding for the globe and environment. I enjoyed it!

Double Cluster

This pair of open clusters leaning against each other between Cassiopeia and Perseus are beautiful in binoculars. You need a pretty wide field of view to take it all in. Even with the 40mm e.p. I could only fit about one and a half of them at a time. Dozens and dozens of stars, mostly bright white or blue with one or two red ones toward the middle of the two.

Kite Cluster

Described as a diamond of stars with a string of five or more for a tail. I think I saw it, now that I’ve seen pictures of it, but it didn’t look like a kite to me.

M76

This planetary nebula (poorly named, having nothing to do with planets other than sort of looking like one) is fairly compact, maybe 15″? and appears kind of pine tree shaped, so it’s doubly badly named as Little Dumbbell. Maybe with better conditions and/or more patience it looks like the Dumbbell. I think I saw mostly the core. It varied in consistency from top to bottom, being kind of patchy. It sits next to one or two field stars to the west.

Gamma Andromeda (Almaach)

This is a beautiful double star out on the tip of Andromeda with the two stars varying in magnitude and color. The brighter partner is several orders of magnitude brighter than the fainter companion. The brighter is a golden yellow tone, while the partner is a bright blue. Very pleasing pairing.

M27

The Dumbbell (planetary) Nebula appears vastly larger than the Little Dumbbell! A large round object with mottled appearance, M27 filled about half the field of view at 222x.  It’s an easy target and impressive to look at. Imagine, that’s what our sun may look like in 5 billion years.

M57

Unless it looks like this. The Ring and the Dumbbell are both remnants of sun-like stars. It’s thought that they appear at 90-degrees rotation to us, so that we are looking at the side of M27 and down the throat of M57. The Ring is farther away and appears smaller. Nevertheless, at 222x it was clearly a ring of nebulosity. I didn’t see anything in the middle, although sometimes material or a star can be seen.

Epsilon Lyrae

The Double Double is a pair of binary stars that orbit each other. With binocs you can split the one star into two, and at 222x the two split into pairs. The two pairs run perpendicular to each other, so that one pair appears up and down while the other appears side to side. Very cool, and a good end point for the night.

Fireball!

While I was starting to tear down, a bright green light lit up the sky, casting reflections from the telescope tripod legs and shadows on the ground. I looked up to see the end of the fireball, a very bright meteor. It was bright green. A remnant tail about a degree wide and 15 degrees long stretched from the endpoint up the sky. It seems to have run a track that appeared almost straight up and down, maybe from Delphinus down past Altair through Aquila, ending about 15 degrees above the horizon. The tail faded out quickly.

In the end…

Although the conditions weren’t ideal, it was still a very fruitful night out under the sky, which always does my heart and soul good. So glory to God who set all things in their courses and gave some of us eyes to see and souls to thrill at the beauty of it all.

Observing, 8 July 2018

21:45-01:00 EDT
68º-58º F clear, calm, humid!
No moon (26 days)
Transparency very good
Seeing bubbly
Celestron 8” Nexstar Evolution
Eyepieces: 40mm, 32mm, 13mm, 9mm, 8.8mm, 6mm

First real observing session with the new C8. It performed very well. I started by playing with the collimation (mirror alignment) a little, but it was really pretty good, even at 500x. Nice job, Celestron!

Celestron 8 Nexstar Evolution out of the box
Then it was off to the races. Having GOTO and tracking is AWESOME! I was out to do more survey work than studying anything in detail, just seeing how the scope performed on different objects. So I looked at planets, globular clusters, nebulae, open clusters, and galaxies. The seeing (measure of atmospheric disturbance) made the planets a little challenging, but I was pleased nevertheless.
Jupiter was super bright, but it was hard to get much detail due to the poor seeing. The two equatorial bands were obvious, kind of thin; a few blue-gray spots under the (… oh dear, which way does an SCT turn things?… ah! Here we are. With a diagonal, it’s right side up, but mirrored left to right.) NEB; a few fainter bands visible; blah blah blah. What was especially interesting was that little black dot right about the meridian and half way up the northern hemisphere. It was visible at low power (62x), but I wasn’t convinced at first it wasn’t an artifact. At higher magnification (222x was best), it remained, so yes, a moon shadow I think! One of the moons appeared just west of the planet, so was it that one? I thought there might be a hint of something emerging from the disk in the NW, but didn’t give it much time or thought. Going back to low power, there were only three moons visible, so something was transiting or eclipsed. Upon research after the fact, it was Io that was transiting and was emerging at about 22:38, which is about when I was there. The shadow was also of Io, which exited the disk at about 23:45. This is consistent with what I saw. I returned to Jupiter later, sometime after midnight, and at 222x there were two moons hanging out west of the disk. So the one I had seen which was westerly of Io was Europa. Ganymede was to the east, and Callisto was way west.
Saturn was better behaved, being not so obnoxiously bright as Jupiter, but still wobbly. Always just such a remarkable sight, though. Even at low power I could see the Cassini Division popping in and out. The rings are still wide open, but now are encroaching on the planet disk. It is still close to opposition, so there isn’t much in the way of disk shadow on the rings, and with the seeing as poor as it was, not much ring shadow on the disk, either. The northern hemisphere change in color was visible, going from yellow near the equator to greenish over the pole. The rings outside Cassini Div. were noticeably darker than those inside. That’s about it for detail that I remember. I did push up to 333x without much benefit or cost.
Went on a tour of globular clusters after that: M4, M3, M5, M10, M12, M80. I was surprised at M4 (in Scorpius) that it was as dim as it was. I remember struggling with it with the 8” Newtonian because it seemed low contrast against the background. I guess it’s just so! There was no bright core to it, just a grainy patch surrounded by a broad ring of resolvable stars. There is a band of stars that stands out running N to S over the center. This is the defining characteristic I remember from previous views. M3 (in Canes Venatici) isn’t where I thought it was, which is over near Ophiuchus, but more on that later. It is a big, bright globular; bright center covered with grainy, resolvable stars at 154x. This is where all these globs start sounding the same, but it is really an impressive object. M5, which is closer to what I thought was M3, but still not where I thought that was either (it’s actually in Serpens Caput), is another really lovely glob. Tight bright core surrounded with a mantle of bright stars. Should have written about it on the scene, as now it’s escaping me, but I just kept saying, “Wow, that’s gorgeous!” M10 is also very pretty in much the same way, just a little less so. M12 is tiny by comparison to all these others, but also very pretty. (10 and 12 are in Ophiuchus.) The other night I was looking around with binocs and saw a big, lovely glob in Ophiuchus, which I thought was either M3 or 5, but now I know it wasn’t either, so I think it must have been M10, except that isn’t where I thought I was looking. The closest to where I thought I was looking is actually M107, but that is really small, so it probably wasn’t. Oh, well. Let’s move on.
By now the Milky Way was well up, and Sagittarius had cleared the trees, with the Teapot sitting nice and level. So I made a run up the galactic core nebulae. Starting with M8, I was astonished that it filled the field of view at 154x (13mm). The nebulosity was visible but not super obvious. I backed off to 62x and maybe that’s when I broke out the 40mm for 50x, even. M8 is just huge! Two bright stars stacked N-S just W of center, then a cascade of smaller stars to the east. Nebulosity most noticeable around the two bright ones with a dust lane cutting between them and the cascade. A small brighter patch of neb just W of the southern of the two stars. Does that make sense? Might need darker skies or a filter to enhance the contrast and bring out the nebula some more.
M20, the Triffid, is tiny and faint by comparison. Also centering on two N-S stars, but much smaller and closer together. (I should learn how to talk about these in terms of magnitude some day.) If averted my gaze, I could sort of see the nebula and the dust lane that divides its lobes. I don’t think it was just constructed from memory. Again, more contrast would help here.
M21 is a small open cluster. Next to these other show pieces, it’s no wonder no-one pays attention to it. Including me. Next….
M24 is the galactic star cloud, which would be a good name for a 70s pop band. It is so big that even with the 40mm, it just looks like a lot of stars. Which of course is what it is, but it isn’t identifiable here as an “object.” Really need binoculars for this one. Just saw something about it, though, pointing out it is actually a hole in the galactic dust lane that allows us to see these stars that are near the heart of the galaxy. It’s not really a cluster of any sort. So that’s cool.
M17, the Swan Nebula, is always a favorite of mine. Here it appears to be on its head. The loop of its neck, as it were, concave to the west with two stars on the curve. The body runs from west to east, pretty large and obvious. (I should learn how to talk about these things in terms of arc minutes and arc seconds some day.) Will always remember how it appeared in the 25” scope in New Mexico. Ohh baby.
M16, the Eagle Nebula, appears as a small open cluster without much in the way of nebula. Again, with some averted vision I could pretend there was some nebula, but I wouldn’t swear to it.
Mars had now made its way up to a reasonable height, for all the good it did me. Poor seeing, still a relatively low altitude, and the planet-wide dust storm it is undergoing all conspire to make the current appearance of Mars, just 3 weeks from the closest approach in 15 years, a mess to look at. Basically no detail at all, just a salmon-colored ball. Not so much as a polar cap. I think I went up to 222x. At some points with a little averted vision, I thought I could make out some faint surface markings, but I wouldn’t swear to it. I tried a couple filters. What I think turned out to be a green filter had the interesting effect of making the disk essentially white. Wasn’t expecting that! Again, some impression of faint surface markings. Tried a red filter, which was really, really RED and made everything RED! Not very helpful, but interesting. Tried it on Saturn, too, with much the same effect. Upon further research, it appears that Syrtis Major should have been about on the meridian at midnight, so it is possible I was seeing some of its outline.
By this time things were getting damp. I mean, there was water standing on things on the table. I had my dew shield on the scope, but when I checked, there was some dew on the corrector. I pressed on a little more to catch a few galaxies.
M51, just south of the tip of the Big Dipper’s handle, is always a favorite. It appeared as two bright blobs, the cores of the two galaxies, surrounded to the SW especially by nebulous fuzz. No real sense of structure at all. I think I was running at 154x? Or maybe it was the 32mm at 63x.
Popped over to M81, Bode’s galaxy, a large elliptical that looked kind of an oblong blob. I think I was using either the 32mm or the 40mm and expected to find M82 right next door. I didn’t. So I didn’t spend much time with 81 and went to 82, but again its neighbor was not in sight anywhere. I thought they should both appear in the same field of view at low power, as they are less than a degree apart, but couldn’t find both at the same time after some searching. M82 appeared as a long, bright slash running SW to NE.
By now I had serious dew on the scope. I also had not set the scope up high enough that I could just stand, so I was doing a lot of half bends or high squats, and I was getting tired. All in all, the scope performed admirably. The goto worked really well, and the tracking was quite steady, and these were the things I really wanted in a computerized mount. The tracking motor buzzes in cycles, which may have been enough to send a vibration through the image, which I noticed especially on Saturn. It’s possible, though, that it was just the rippling of the atmosphere keeping time with the mount. I hope for a bit better experience on planets with better seeing conditions. Deep sky will also need some getting used to, trying to find the right magnifications for the various types of objects. The globs and open clusters were the winners of the night. After taking the scope off line, I just spent some time looking, as it was still a really beautiful night, and it felt good to sit down for a few minutes. As usual, I thank God for the beauty of the night sky, the eyes, time, and equipment to behold it, and for all peace I feel in the process.
Stuff I looked at:
Jupiter – with moon shadow
Saturn – Cassini division w/ 32mm
Mars – totally washed out with dust, but maybe a few surface features
M3 – very nice
M4 – oddly dim
M5 – absolutely gorgeous
M8 – enormous
M10 – beautiful
M12 – adorable
M16 – hint of neb
M17 – lovely
M20 – pretend it’s there
M21 – meh
M24 – better in binocs
M51 – getting dewed, dude; two cores and some fuzz
M80 – very pretty
M81 – visible blob
M82 – long, thin, bright