Sunday, July 17, 2016

 

Issue 502: How Low Can You Go on the Messiers?


As in “How little aperture can an experienced observer use and still get rewarding views of the brighter objects from the backyard?” This is, friends, a follow on of sorts to last week’s edition. If you read that, you know one of the things that have concerned me of late is the size and weight of my telescopes and my ability to handle them comfortably and safely, not just years from now, but right now.

Last time, I mentioned, somewhat in passing, that I’ve been having back problems and that that might make my continued use of my Zhumell 10-inch Dobsonian problematical. That was brought home rather starkly the last dark of the Moon Saturday night when I transported the Dob, Zelda, to our club site for an evening—I thought—of relaxed deep sky cruising with a few good friends.

Zelda, a GSO scope with a solid, steel tube is not overly heavy. At least that was what I thought till that night. My backache had at least lessened, if not gone away, so I wasn’t overly concerned about loading Z into the 4Runner, setting her up at the dark site, and reloading her in the truck at the end of the evening (I can leave the scope and gear in the 4Runner overnight after I get home, unloading the next morning, unlike when I lived downtown). I was feeling good and looking forward to some nice views on a good if not perfect evening.

And Zelda did deliver those views:  spiral arms in M51, countless stars in M10 and M12, and even a little resolution of great Omega Centauri, which was descending and only barely above the tree line. No, conditions were not perfect. The Splinter Galaxy, NGC 5907, was not as prominent as it usually is in a 10-inch, but it was not much better in the 15-inch set up next to me. Finding that galaxy and anything else I wanted to look at was duck soup with the aid of my 50mm RACI finder, my Rigel Quick Finder, and SkySafari running on my ASUS tablet.

So, I was one happy little camper? Uh-huh. Until about two hours into the evening when my back began to let me know I was going to pay for loading and unloading the Dob. I considered sticking it out for a little while longer, but then the wind changed and the smoke from a nearby field that was being burned off blew over and settled onto the observing field. I reluctantly gave the evening’s run up as a bad business. Back home, I pondered what to do about my telescope/back problem. Not just at the dark site, but in the backyard.

While my backache has alleviated over the last week, I am still wary, and have decided that for now I’m only using reasonably light telescopes. Not just at the dark site, but in the backyard. Wary? I am at the moment afraid to lift the 10-incher’s tube. A pretty pass, doncha think? So, what shall I do?

The obvious candidate for use while I am on the DL, I decided, was Charity Hope Valentine, an ETX125, who I neglected to mention last time. I simply forgot about her. Maybe because she’s been squirreled away in the sunroom closet in her case almost since we moved to the suburbs. She is light, if not as light as an ETX90, and would, I thought, not be a challenge for suddenly decrepit me to move around, not even with the tube/drive base affixed to the tripod. Best of all, she is a complete little system with built in goto via the Autostar computer. The only ancillary item I’d need would be a battery or AC power supply and a dewshield.

She would have been almost perfect, but the poor little thing has gone to that big star party in the sky after being my faithful friend for a decade. I set her up in the backyard one night last week, hoping for passable if not exactly transparent skies when, suddenly, the rain began to fall. I threw a cover over Charity and scurried inside. “Maybe tomorrow,” I thought. Late the following afternoon, I thought I’d check to make sure Charity’s LNT real time clock was working—I’d replaced the battery the previous day. Hooked her to a jumpstart battery, threw the switch, and she beeped as normal, but the LED display on the Autostar controller did not illuminate. What the—?

Nothing I could do helped, so I shut her down, disconnected the Autostar, and took it into my shop, The Batcave, for examination. What the problem was was immediately evident when I opened the case:  a couple of chips had been turned to charcoal. How had that happened? There’d been a tremendous nearby lightning strike that morning. While the scope was not plugged into AC, she was close enough to the strike that the Autostar had been fried. But good.

What to do? My tests indicated there’d been some internal electronic damage to the scope, too. There’s not a lot of active circuitry in the PE, but there is some. I might try to repair the scope and replace the Autostar with one off eBay or something. Or I might put the scope on some sort of new mount—maybe a driven alt-azimuth mount like one of Celestron’s SE rigs.

But I am not going to do anything immediately. I have decided to see how it goes with my back. If my problems abate completely, I’ll go back to using the 10-inch. If not, I’ll either fix Charity or defork her. Having a light scope on a driven mount, a driven alt-azimuth mount, will be a good thing if I am not all better soon. But what do I do for now? What do I use at home and at the dark site while I am waiting for my back to tell me what to do?

Simple:  I use my good old SkyWatcher AZ-4 un-driven alt-az mounting. It’s very light and has a Vixen style dovetail saddle, so I can use any one of several scopes with it, and especially my refractors. Which refractors? The mount will happily accommodate either my C102 4-inch f/10 or my wife’s 4-inch f/6.5 Explore Scientific. Either of those should be bearable even if my backache returns. But only marginally bearable, and the C102 is approaching “Danger Will Robinson!” territory. I decided to start out smaller and lighter, with the 3-inch (80mm, actually) f/11.4 SkyWatcher OTA that came with the AZ-4.

I haven’t used this pretty OTA a whole lot, she was just lagniappe; I really only wanted the AZ-4. But from what little I’d used her five years ago, I knew she was more than sufficient for casual looks at the Moon and planets. The big question was whether she could also deliver at least somewhat satisfying Messiers while I am under the weather.

Yes, I could use my undeniably (much) better William Optics Megrez II 80mm instead, but I like the idea of the 910mm of focal length the SkyWatcher delivers. That makes her more effective on the planets—I can get higher magnifications without fooling with Barlows and very short f/l eyepieces. Having more power eyepiece for eyepiece also keeps the sky background darker in my somewhat light polluted backyard.

The weather—naturally—prevented me from answering the above question about the little scope’s efficacy for some time. Typical Mobile summer: thunderstorms every afternoon, often extending into the evening. Even if the clouds disperse they leave plenty of haze behind. And there are the bugs, of course. And walking into the night is like walking into an absolute steambath. Not the sort of environment that impels you to grab a telescope large or small.

Nevertheless, as the Allstar Game was winding down the other night (it had become obvious my National League team was gonna lose to the American League), I fetched the SkyWatcher 3-inch refractor, whose, name, by the way, is “Eloise,” out of the Batcave and sat her in the backyard to warm up—the Batcave’s air-conditioner was going full blast, and if I’d uncapped her objective immediately it would have promptly fogged up.

With the game over, I ventured back into the backyard to, first of all, reacquaint myself with what the telescope would do on the Solar System. Eyepieces? Nothing special, just my old Orion/Pro Optic wide-fields and a 6mm Celestron (Vixen made, I think) Orthoscopic that is at least 35 years old. The telescope is equipped with a 1.25-inch (only) focuser, but I hadn’t found that a limitation. Her aperture and focal length give a decent, wide field at 25mm.

Alright, onto Luna. The just before First Quarter Moon looked terrific. Of particular note was the Straight Wall, which was near the terminator. It was so sharp, like an obsidian knife lying on the lunar surface. I bumped the magnification up to close to 150x with the Ortho, and the image remained good, very good. Higher? I could have gone higher; the little scope takes magnification well, but at 150 the image is getting dim thanks to the small aperture.

Otherwise? Color, for example? What color? Yes, I know for the chromatic aberration in an 80mm achromat to be really well-controlled, it needs to be at a focal ratio of at least f/15, but no color did I see with this scope  at a smidge over f/11 (admittedly my eyes are not as sensitive to spurious color as they once were). Away from the terminator, the disk remained sharp, if maybe not quite as sharp as in an APO—still looked good, however. There is little doubt in my mind that a dedicated observer could do some fairly serious lunar exploring with this telescope.

By this time, Jupiter was getting low in the west, and was in fact behind a pine tree to the southwest. To get a look, I’d need to move the scope. That is one of the beauties of Eloise on her AZ-4. Light. No polar alignment or goto alignment. Need to move her? Just pick her up and freaking move her!

Which I did, lining up Jupe with the SkyWatcher’s red dot (“bb gun”) finder. While I have a 50mm RACI finder I can use on the telescope when needed, I don’t often need to. The Combination of the red dot and a 35mm – 40mm eyepiece makes it easy to get anything I want into the field. The verdict on Jupe? Sharp, particularly the Galilean moons despite the low altitude. There was no false color I could see other than that produced by differential refraction thanks to the altitude. The major cloud belts were easy and high in contrast. When the seeing would occasionally get really good, I could see some detail in those bands.

Saturn was nice and high by this time, so I headed that-a-way, figuring the altitude of the planet and the excellent seeing on this evening ought to allow Eloise to really strut her stuff. It did. At 150x, the ringed world was just lovely. Cassini’s Division was sharp, disk detail obvious, and a couple of Moons in addition to Titan were visible with the Ortho. Honestly, I can’t say the image was much worse than what I saw in a beautiful 4-inch Takahashi at the dark site a while back.

I already knew the 3-inch could deliver the goods on the Solar System, however. Her objective is of excellent quality, and prior to the SCT explosion of the 1970s a good 3-inch refractor was the chosen tool of many a Solar System observer. The question was would the views she’d give of the Messiers and other brighter DSOs be good enough to lure  me into the backyard with her on a regular basis while waiting for my back to decide whether it wants to punish my faux pas further?

To find out, I began with an easy one, M57, the Ring Nebula in Lyra. It’s bright and small and easy. Which doesn’t mean it’s always terrific in a small scope in light pollution. I’ve often struggled to make out the “donut hole” with a 4-inch Newtonian in light polluted areas. I inserted a 20mm Expanse eyepiece and positioned the scope on the Ring’s well remembered spot.

And there it was. It was too small at 45x to make out much, but, yes, there it was, easy to see and shining bravely amongst the dim field stars. Upping the magnification to 182x with a 5mm SkyWatcher wide-field eyepiece made the ring shape and the fact that the nebula is elongated rather than perfectly round reasonably easy.

How would Eloise stack up against other similar aperture scopes in similar conditions? The C102 would have done a better job, but only a bit better. However, the ring shape of the nebula was easier to make out than in a 4-inch reflector in comparably punk conditions. I would say the view was pretty much equal to what we had in a friend’s StarBlast (4.5-inch rich-field Newtonian) from the dark site a couple of weeks back.

In other words? Not bad. Back in the 60s, people liked to say that a 3-inch refractor is the equivalent of a 6-inch reflector. That’s not true now and wasn’t true then. In a 6-inch, the Ring is more sharply defined and it’s elongated shape far easier. There’s just no way to get around the 6-incher’s 400% increase in light gathering power. Still, a 3-inch will show the same details, just in slightly subtler fashion.

M13 was, I realized, riding high. Almost too high, nearing culmination. Where has this summer gone? Hercules’ Great Globular was OK. I did not note any resolution on this night, but the cluster looked grainy, as if it wanted to resolve. I can achieve some resolution with my 80nn APO on good nights, and certainly I can with the C102 4-inch refractor under clearer skies, so it’s not out of the question that Eloise might pull out a few suns from M13 on a superior evening, even in the backyard. Anyhow, I thought the cluster looked better in the 3-inch refractor than she does in the average 4-inch reflector.

M92, Hercules’ other globular star cluster is a good target for medium aperture telescopes under reasonable skies. It is in no way a rival of M13 for appearance, but it is good nevertheless. For a little scope peering up through humid haze? Not so much. M92 looked pretty good, all things considered, and did appear somewhat grainy, but I didn’t see any stars. As with M13, however, the Megrez will pick out a few on an OK backyard night, so I expect Miss Eloise might be able to do the same.

I thought I’d look for M51, and look I did, but no M51 did I see. That was not overly surprising considering the sky and the fact that it was getting worse as the night grew older. I was somewhat disappointed at first, but recalled that in the past, even years ago when my eyesight was no doubt more acute, I have had a very difficult time making out the two blobs that are M51 and NGC 5195 with a 6-inch Newtonians on nights such as this one.

M27 wasn’t exactly at its best, but it was there. If I’d waited for it to get a little higher, it would no doubt have been better, but despite Deep Woods Off and a citronella candle, I was literally being eaten alive by mosquitoes. As it was, the Dumbbell was a not too bad fuzzy oval at medium power.

Do you like double stars? I always have, even though I’ve gone through periods when I haven’t observed them much. One thing I know is that a longer focal length 3-inch refractor can be a powerful portable tool for viewing double stars within the limits of its resolving power. Stars are quite tight in Eloise, and she can frankly best somewhat larger reflectors on binaries. How about Polaris, then?

Uh-uh, no joy. Polaris can occasionally be a challenge for a 4-inch, so I wasn't too disappointed not to pick out the companion. I don't think the problem was resolving power, but more the dimness of the comes in the hazy, transparency-challenged skies.

The three inch proved herself, mostly,  and I think will serve admirably while I wait to see what the story is with my current infirmity. If my back goes back to normal, out comes the 10-inch. If not, if I have to baby it and seek treatment, the 3-inch, maybe supplemented by the ETX, perhaps on a new mount, will be it for a while I fear. No, 3-inches or even 5-inches is not in the same performance league as 10-inches, but I’d rather see something than nothing, and seeing what you can pull out with a wee scope is, I must reluctantly admit, challenging fun!

Comments:
Our club has an annual member event we call the "Small Scope Star Party" where max aperture allowed is 6.0 inches; no cameras, binoculars or stopped-down scopes allowed. We encourage people to bring more than one if they have them, and we set up about 90 minutes before it gets dark so everyone can look at the scopes before they look through them. It's proven to be a popular event :)
 
I hear you - need both knees replaced. 20 pounds is my maximum carry for say less than 10 yards. So here is what I use now -

1. quick looks, Starmasters Binocs 20 x 80mm on a very tall CF tripod and 501 video head.

2. My C90 on SLT - 8-9 pounds? (with or without the .63 focal reducer for wide field (try it Rod, you might find that combination useful)). Can carry the entire setup including battery on one trip. Great Spotter and good little scope when cooled.

3. My "serious" scope - the C8 you advised me to buy a long time ago on the used LXD75. If I could only have one setup it would be the C8 on a small GEM - most versatile scope you can own. Light enough for even an old person (I am older than you) but the best jack of all trades (remember when that was your line:0) Each component less than 20 lbs.

As we age we really do have to be mindful of what can hurt us and how long it takes to recover.
 
Hi Rod,

Thanks again for another great Sunday afternoon. I pray your back heals completely and you can go back to your larger scopes, but it's encouraging to know that these smaller scopes can still satisfy.

John O'Hara
Oil City, PA
 
Uncle Rod, I have been a fan of your blog for several years now, and I wanted to thank you for your kind words about 80mm refractors. You and I are about the same age, and like you I started observing when I was in my early teens. Because of my demanding work schedule, most of my observing has been with an 80mm refractor. Your statement that "I would rather observe something rather than nothing" pretty much sums up my amateur astronomy "career". Thanks to the 80mm refractor I was seeing something, when otherwise I would have been seeing nothing for a number of years. BTW, you might not want to post on Cloudy Nights the comment about the image of Saturn being "not much worse" than in a 4 inch Takahashi. That one might draw some fire, LOL. Thanks again for the excellent post, and I hope your back is feeling better soon.
Lewis Cason
Kiawah Island, SC
 
Always a pleasure to read your blog Rod! I hope your back gets better quickly. I sympathise. I've just put my back out laying some paving slabs to put my new AVX mount on (determined not to have my new pride-and-joy standing in muddy field!). All the best, Phil, UK.

 
I know where you are coming from, Unk.

Now-a-days I am reaching more and more for the Orion 127mm Mak-Cass and StarSeeker mount instead of the C8 and AVX.

Soon I will be back to my first scope, a Gilbert 3" reflector that I had back in the early 1960's. Well, it was certainly light enough, lol !!!
 
You and me both, George, you and me both. LOL
 
I am heading for surgery here soon, and can't lift much, but the astro bug has gotten strong again. So, I head out for the 40 minute drive to a state park and an impromptu club viewing session with just my 20 x 80's and a CF tripod/head - each piece maybe 5 or 6 pounds.

I watched folks struggle with the 12" and even the 5" APO's. I was amazed what could see (a younger man and I got stars in M12) and M31 in the 3.7 fov was amazing.

The fluid head move's the 80's like butter, and no finder needed:) But most important was just being with some folks who love the same thing you do. My very inexpensive Starmaster (which I went through 3 pairs on Amazon to get one, and learned the secret to collimnate them) got rave reviews even from folks with larger scopes, actually had a line a couple of times:)

I am strongly thinking about getting a Desert Storm best cover (have the lessor one) and leaving my LXD75 setup in the yard for long periods of time, the C8 weighs so little and I've begun to like using my m43 camera that shows time exposures as they develop so I can see things at home. Rod, you might consider leaving you AVX setup under a cover if you have a good viewing location.

Have you talk to a Dr. about a back brace for lifting?
 
Hi uncle Rod,

I like reading your blog and enjoy also the pictures of your scopes. I underwent a back surgery some time ago (disc herniation)so I have to care of my back. I found on my C6 a good friend of my back and my eyes. You can also consider using back support when lifting any weight and between observations do some stretching exercises.

I also have my 15x70 Binos and from a Bortle 5 sky I have seen more than 90 Messiers. Of course it is just a glimpse to light but there they were.

Greetings!
 
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