Sunday, June 14, 2015

 

Zelda at the Dark Site


The only true test of a scope is under stars set in dark skies. I was enthusiastic about what little I’d already been able to accomplish with my bargain Zhumell (GSO) 10-inch Dobsonian, but now came time to see what she could really do. To that end, Z and me headed west to the Mobile Astronomical Society Dark Observing Site just 45-minutes away in the suburban - rural transition zone.

What did I expect of the telescope? I expected pretty great things. I could tell from what she’d shown me of Jupiter in the backyard that she had a decent primary mirror. And one thing we tend to forget these days is that a 10-inch is still a big scope capable of outstanding deep sky performance. 

A 10-inch Newtonian, after all, was the largest telescope regularly used by that dean of deep sky observers, Walter Scott Houston, and one is also the largest scope his successor, Sue French, usually writes about. If somebody tells you a 10-inch can’t deliver on the deep sky, they simply do not know what they are talking about. A 10-inch allows you to push well past the Messier but to do it with a comfortable, manageable scope.

Yeah, aperture always wins—in or out of light pollution—and a 12-inch is “better” than a 10-inch, and a 16-inch is better than that, and so on, but there are sweet spots. 10-inches at f/5 is one of those. A 10-inch f/5 delivers plenty of light for the deep sky and with a wide enough field to let the medium sized objects most of us concentrate on shine in common eyepiece focal lengths. A 10-inch f/5 just provides a nice balance of object brightness and field size.

I’ve been an ATB (Amateur Telescope Buyer) for long enough now to know when I’ve got my hands on a good one, and, yeah, I expected great things from Miss Z.—if we saw anything at all. Which seemed in doubt at first. It was sprinkling rain when we left home and the streets were wet almost all the way out, but as we neared the site, an airfield that is disused at night, the clouds that had been pouring in from the south began to scuttle off and a giant sucker hole began to encompass the entire sky.

The mosquitoes, as you’d expect after weeks of rain, were exceptionally fierce, but I managed to keep them mostly at bay with Deep Woods Off and a Thermacell bug repeller—for a while anyhow. I had the good sense to get the Thermacell going the instant I arrived—it takes about 15-minutes to begin to work its magic. Despite temperatures in the high 80s, I put on a long sleeve shirt until the T-cell began to clear the little vampires out . Better hot than bitten, I thought.

It’s been a while now since I’ve gotten spooked at our friendly and safe dark site; my current mindset ensures the Greys and Mothman are not even on the edge of my radar screen. Still, it was nice have some company, to be joined by two fellow club members, Max, who brought along a 6-inch Newtonian, and Taras, who had the intestinal fortitude assemble his 15-inch home built Dobbie on our observing field beside the runway.

While waiting for darkness I got Zelda settled in her rocker box, and I plugged in her cooling fan to acclimate her primary, which had been sitting in the 4Runner's blessed air conditioning all the way from home, natch.

The BCH Project

You gotta have a plan. If you don’t have an observing plan, you usually won’t make it through ten objects much less past twenty, “Hmm…seen M13, seen M57…guess I’ll pack it in.” Before departing for the dark site, I finalized the first of a series of new of observing projects, visual observing projects.

What I did was resurrect one I’d formulated when I completed the Herschel Project, my quest to view all 2500 (give or take) Herschel fuzzies. I was into doing big observing lists with deep sky video cameras at the time and thought for my next Feat of Strength I might observe all the objects in Burnham’s Celestial Handbook. After culling out all the double and variable stars and most of the deep sky objects I’d observed many times, I was left with a manageable list of about 800 faint fuzzies.

The list was quite doable. I could have knocked off 800 objects with the C11 and Mallincam Xtreme in a year or less, even given the horrible weather we've had lately. But I never got very far with it. Subtracting the bright and beautiful left me with a list that was much like the ground I’d already covered, the small, faint galaxies of the Herschel Project. I enjoyed doing that when I was doing it, but more nights of “small, round elliptical galaxy” just wasn’t appealing to me.

But what would I observe visually with the new scope? What if I reconstituted Project Burnham as The BCH Project? This time ignoring the object lists at the beginning of each constellation (chapter), and instead observing the wonderful objects,  the bright showpieces (mostly), that Robert Burnham provides “descriptive notes” for in the text of each constellation?

I fired up SkyTools 3, grabbed my “field” copy of Burnham’s from the bookshelf in the den, and began with Canes Venatici, building a list of objects from its Descriptive Notes. I did Hercules, Ursa Major, and Ophicuchus, too, and when I was done had a plan just shy of 40 DSOs, which I thought would be perfect for a relaxing evening with Miss Zelda.

C/2104 Q2, Comet Lovejoy

Yes, last winter’s great comet (I thought so), everybody’s little pet, Lovejoy, C/2014 Q2, is still with us. Of course the visitor, who is now on his way out and high above the plane of the ecliptic, ain’t what he was last winter when every amateur who could get their hands on a camera was comet picture crazy. But he’s still observable in 8-inch and larger telescopes with fair ease and even maybe in binoculars from very dark sites.

Lovejoy was the evening’s first target. I thought the comet would provide a good warmup for my no doubt atrophied object-finding muscles. While it wouldn’t be that dim at magnitude 8.5 and about 5’ in size, the comet wouldn’t exactly be obvious anymore. It did indeed take me a couple of tries to correctly position Zelda on Lovejoy’s spot in the midst of a field of anonymous 8th and 9th magnitude Ursa Minor stars about about 5-degrees north of Polaris.

From what I’d read about the comet recently I’d expected it to be visible in my 50mm finder, but I couldn’t see a trace of it in there. I hadn’t taken our heavy haze into account nor, I suppose, some folks' ideas of what is easily visible  in a 50mm finder. When I was on the correct position, though, Lovejoy wasn’t that hard in the main scope, showing up as a strongly elongated fuzzy that (maybe) even showed a hint of a tail stretching off to the northeast.

How atrophied were my finding muscles. Not as much, gratifyingly, as I thought they might be. In just a few minutes I was getting back into the swing of it again. The combination of a zero power sight and a 50mm correct image finder is a powerful object locating tool when coupled with the tailored finder charts you can produce with modern software like SkyTools 3. With a 3-pane chart on the laptop showing a naked eye view, a 50mm finder view, and an eyepiece field for the scope’s current eyepiece, finding stuff wasn’t even that time consuming.

And I did try to keep up a decent pace since an old Moon would rise at 11:30. Twenty or so objects over the course of the two hours before Moonrise seemed about right. I felt like I saw a lot, but I didn’t feel pressured and there was never a time when I missed goto or DSCs.

M81 and M82

Comet in the bag, it was time to begin touring Mr. Burnham’s best of the best starting with these two favorites in Ursa Major.  I love both galaxies, but usually it’s M82 with its dark lane crossed near edge-on disk that lights my fire. Tonight, though, it was M81 that was the standout.

Oh, M82 was grand, showing considerable detail despite its decreasing altitude, but what blew me away was M81’s size. This intermediate inclination spiral was huge and wanted to show me at least a hint of its two loosely wrapped arms. They are normally a challenge for the darkest nights and clearest skies, but Zelda was at least giving me a taste of their beauty. Bob Burnham called M81 “magnificent” and he was right as usual.

The 30mm Zhumell eyepiece that came with the telescope endeared itself to me on these objects, easily fitting both (they are 36’ apart) in its generous field with room to spare and providing surprisingly good contrast. The pair was also great in my 35mm Panoptic, but I thought a little more power, just a little more, made them even better. 

NGC 3077

I’ve often gauged the quality of a given night by the visibility of the third member of the M81 group, little NGC 3077. The verdict on this night was that at astronomical twilight the sky was considerably better than it had been at sundown. While it was damp, a drier wind had begun to blow through, a strangely warm wind, and while the seeing wasn’t anything to brag about (Jupiter was just OK), transparency seemed to be improving.

NGC 3077, a near-face-on irregular galaxy that really looks more like an elliptical, lies 46’ southeast of M81 and glows rather weakly at magnitude 10.6 and 5’ x 4’ in size. On this night, the galaxy quite frankly looked a lot like a dimmer version of Comet Lovejoy. Nevertheless, it was readily visible in the 10-inch and was surprisingly good in the 16mm Happy Hand Grenade 100-degree eyepiece (78x).

While NGC 3077 is just a little oval of light in most scopes and not something most observers linger over, it does get its picture in the Handbook, and Burnham notes that it, in images, appears disturbed. No doubt it’s undergone interactions with the group’s bully, M81, in the past just as the Cigar Galaxy, M82, has.

M51

It was amazing what darker skies, two more inches of aperture, and a 50mm finder did for me when it came time to track down the Whirlpool galaxy and its companion, NGC 5195. Last time out, I’d tried to locate the pair with the 8-inch using only the Rigel Quick Finder and failed. I didn’t try very hard;  the lack of the guide stars in the area—M51 and NGC 5195 were well within the Airport Boulevard light dome—didn’t encourage me to keep hunting.

With the 10-inches of aperture I had on this night and a 50mm finder to lend aid to the Rigel, landing on M51’s spot three and a half degrees west of Eta, the “end” star of the Dipper’s/Plough's handle, was easy enough. There’s a trio of seventh magnitude suns that help you find your way and which are easy to spot in a real finder scope.

Once I was on the interacting pair (NGC 5195 is, contrary to the way it looks, actually receding into the distance), I switched the 30mm Zhumell out for the 16mm HHG and had a good long look. One thing about old fashioned finding:  the time spent on the hunt encourages you to stop and rest a while, taking a good long look instead of immediately pushing the buttons to take you to the next one.

In my eyepiece, the two galaxies were a treat. At first they were just a big blob (M51) and a smaller blob (NGC 5195) nearly in contact, but a little staring soon turned up the bar shaped center of the smaller galaxy and, best of all, the outlines of one of M51’s spiral arms, the westernmost one.

NGC 4631, the Whale Galaxy

One of my fonder visual observing memories is from about seven years ago on a similarly damp spring night when Taras and I braved the bugs to observe as many spring galaxies as we could. The standout was, no doubt about it, NGC 4631, the Whale Galaxy, whose wedge-shaped disk makes it look amazingly like a swimming cetacean. 

Even better, this whale is accompanied by a “calf,” little NGC 4627 (magnitude 13, 2.2’ x 3.7’). The Whale’s child was only intermittently visible in the 10-inch on this night, but it was also only intermittently visible in Taras’ 15-inch, so I guess Zelda did pretty good.

By the way, there is a dim star just to the southeast of the Calf that is not shown on the SkyTools charts. Sorry, that is not a supernova (it is on the POSS plate of the galaxy).

M94, The Croc’s Eye Galaxy

M94 was one of the first objects I visited for my book, The Urban Astronomer’s Guide, and I will get back to it from the backyard when I move on to my SECOND visual project, revisiting the Urban objects, but I wanted to observe it from a dark site on to have a basis for comparison later. As usual, the main impression was, “Like a medium-sized unresolved globular star cluster.” More staring, though, and the 8mm Ethos brought out hints of the tightly wrapped spiral arms just outside its interior disk. I was impressed enough that I essayed the second sketch of the evening.

M63

It took me a while to get on the Sunflower Galaxy. Somehow I got bum-fuzzled and started looking for it on the wrong “end” of Canes Venatici, on the northeastern instead of the southwestern end. At first I thought I had it, but I soon noticed a second galaxy in contact with "M63." And I’d already noted that the Sunflower seemed to be missing its normal small, bright center. Turned out I was looking at the Cocoon Galaxy, NGC 4490 and its companion, NGC 4480, by mistake. Not that they were not nice and all.

Switching to the opposite end of Canes, I was soon at the Sunflower, which was about twice the size of the Cocoon, 12’ across, but didn't look a bit dimmer despite that larger size. There was also that bright center, and signs, strong hints, of the Sunflower’s multiple dusty, patchy spiral arms.

M97

I normally look for M97, the Owl planetary nebula, with an OIII filter screwed onto the eyepiece, but I began without one this time. Not a problem. Old Owly was holding court bright and bold unfiltered in the 16mm ocular.

Adding a filter was almost like gilding the lily. I will say the UHC (that’s what came to hand first) did make this round nebula a little bigger and the dark spots that are its “eyes” a little easier to see, but the difference was not night and day. It would have been hard to make the Owl much better than he was. Only problem? The seeing, which was getting worse, was making the owl’s eyes swim in and out of view.

M108

A mere 48’ west of M97 is one of Ursa Major’s premier galaxies, M108, a magnitude 10.7, 5.4’ long intermediate inclination beauty. It is a barred spiral with loose, dusty arms and a look that, at low power, reminds you of M82. It is not disturbed, though; just patchy and dusty. I had no problem finding M108  when I looked at a chart instead of relying on memory.

M101

And then there is the Catherine Wheel Galaxy, M101, a massive face-on 22’ across giant. While its magnitude is a bright-sounding 8.4, that is what you’d get if you squished it down to the size of a star. If you want to know how dim it is, defocus a magnitude 8.4 sun until it nearly fills your field. That dim; Taras thought I was wasting my time.

I wasn’t. At times, this one can surprise, and this was one of those times. It was immediately obvious when I landed on it, and, as I stared, began to fill the field of the 30mm eyepiece. Then it began showing off spiral arm detail. I do get lucky sometimes.

NGC 5139, Omega Centauri

The first good look I ever got of Omega was from our old club site in Hurley, Mississippi with my homemade 6-inch f/8 Dobbie. The view was stupendous, so I always hunt up NGC 5139 whenever it is over the horizon at our current dark site. Which it was at mid-evening, if only barely, and well past culmination. It was mostly just a huge milky globe, and it took the magnification delivered by my 13mm Ethos to begin resolution. Still, how can you go wrong with freaking Omega?

M106

Like many of you, I suppose, I don’t view M106 very often. The question is, why don’t I visit it more? It is bright at magnitude 9.1 despite a size of nearly 16’ across. It shows plenty of detail including a strongly elongated disk and an oval nucleus. On this evening, it even gave hints of its two spiky spiral arms. Maybe it is because it is located in a rather star poor area of Canes Venatici? Well, most of you are using goto or digital setting circles so that doesn’t mean much anymore. You all tell me why this beauty isn’t more popular, huh?

M13

With Hercules not just on the rise at 10 p.m., but riding high, it was time to desert the spring skies for the summer heavens. The Great Globular (magnitude 5.8, 20’) certainly lived up to its name with oodles of tiny resolved stars. It was best with a little power in the 13mm Ethos, 96x. I should have looked for nearby galaxy NGC 6207, but I forgot. Oh, well.

M92

As I pointed out in my observing article in the July Issue of Sky & Telescope, “The Backyard Sky:  Summer,” M92 isn’t close to being a rival of nearby M13. At magnitude 6.5 and 14’ across, it is considerably smaller and dimmer. It is still great, sure; it is a Messier object after all, but it needed the 8mm Ethos (156x) to make it really good.

M4 and the Ghost Glob (NGC 6144)

Also in my S&T article was a stop at M4 and its much dimmer (magnitude 9) and even looser companion, globular cluster NGC 6144. This wasn’t on the evening's observing list, but I wanted to see how good NGC 6144 would look from skies slightly better than the average suburban backyard (but only slightly better; the pair was well down in the Mobile light dome). The Ghost was easy enough to see with the 8mm Ethos when I kept nearby Antares out of the field, but it was obvious how it got its name. It looks a lot like a faint reflection of the bright and pretty Cat’s Eye (globular) Cluster M4, one degree to the west.

M57

Last summer we got lucky. Taras and another friend, Kenny, and I were able to see M57’s central star with Kenny’s 10-inch Synta Dobsonian. I didn’t think I’d be able to duplicate that feat with my 10-inch on this night—the steady seeing which is required just wasn’t there—but the surest way to not see something is not to look. No central star did I see, but the Ring Nebula was beautiful in the 8mm Ethos, easily showing the dim stars around the periphery of the ring and the milky, filled center of the donut.

Just after I finished admiring the Ring, the humidity spiked back up noticeably. Way up, bringing fresh clouds of skeeters with it. I sprayed myself all over with Off, but still they bit me—through my darned T-shirt. I hadn't yet got to the wonders of Ophiuchus, but the Moon was over the horizon now and the mosquitoes ensured I had reached my infamous I Have Had Enough stage. One last look at M57 and I was done. The biggest benefit of a 10-inch solid tube Dobsonian then made itself evident. I was packed and on the road in 10-minutes—tops.

Back home, I continued with Netflix and Star Wars: Clone Wars into the wee hours, but it was hard to concentrate. My mind was too full of the real wonders I’d viewed on a suprisingly magical night with my wonderful new telescope. “I think this is the beginning of a beautiful friendship.”

Comments:
As John Bambury says, a 10-inch is the smallest of the big telescopes. I was surprised moving up from 8-inches at how much more I could see, particularly in the structure of DSOs. I've tested the Canadian equivalent of the Zhumell, and found it outstanding optically. As soon as I go to anything much bigger, it becomes too bulky to move and it's hard to get to the eyepiece. My perfect size.
 
Hi Rod, I was out Sat night with some of my buds at Stellar Skies. We had clear skies for about 90 minutes. Looked at many of the objects from your ST article like M4 and 6144 in my 18. Always enjoy your blog.

 
Hi Rod,

A solid tube scope around 10" aperture is indeed a good combination of light grasp and convenience. Over 10", I want a truss. It's nice to be able to set up and tear down in less than 10 minutes. I'm sure you'll use this scope frequently.

Best,
John O'Hara
 
I got a 10" GSO dob because I realized at 61 I could use it until well into my next decade and it was still large enough to see a lot of DSOs. I put two Strap-a-handles on it to facilitate moving it around securely without back strain.

Steve Hanna aka audioaficionado
 
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