Uncle Rod's Astro Blog

Power

I was originally gonna say that if you are the proud owner of a new Dobbie, you can skip this. Dobs don’t need electricity, right? No, they don’t (unless you’ve got a go-to motorized Dobsonian or one on a tracking platform), but the 12-volt hair drier you use to keep the wet stuff off the eyepieces and finder will need power. So will the secondary heater if you’ve gone high-tech on me. If you’ve got digital setting circles, it may be desirable to operate ‘em off an external 12vdc source. But, yeah, you can get out in the backyard and use your Dobster pretty well without a battery.

Computerized SCTs and go-to GEMs need power, often a lot of power. Don’t automatically assume that because you got an economically priced medium-light mount, it don’t need plenty of electrons, either. My humble Celestron CG5, for example, is considerably more power hungry than my NexStar 11 GPS or my Atlas mount. Do more than a little slewing and she will run down a 7 amp-hour battery in a hurry. So why not operate off AC/mains? You can do that. But, in my experience, many go-tos do not operate well off cheap wall-wart supplies. Last time I used one on my NS11, it told me Alpha Centauri would be a good alignment star. Even if you use a high-capacity regulated power supply, there’s the hassle of long extension cords and the lack of any AC at the dark site. I stick with batteries; they are reliable, convenient, and safe.

Choosing a battery is a balancing act. You want something with enough capacity to run the scope all night long (if you go all night long), but which is still light enough to be convenient. How much battery do you need? Depends on your mount and how you use it. A go-to mount may consume 2 or 3 amps (that’s a lot) when slewing at full speed, but far less when tracking. If you don’t normally jump all over the sky, it’s possible to opt for a battery that’s small and (I like this), cheap. But how do you tell if a given battery has enough oomph?

Batteries are rated in amp-hours. One rated for 7 amp-hours can theoretically put out 1 amp of current for seven hours or 2 amps for 3.5 hours. Theoretically. In the real world, you might get 75% of that at best—less in cold weather, which diminishes any battery’s capacity. Tote up roughly how much current you’ll consume on a given evening, allowing not just for draw when tracking, but when slewing and aligning as well (you can usually get your mount’s power consumption specs off its manufacturer’s website; if not, ask on the Yahoogroup devoted to your outfit). If you intend to plug a dew heater or anything else into the same battery the scope uses, you must, of course, allow for that too.

For most of us, it comes down to two choices: jump starters and trolling motor batteries. The what and the who? “Jump starters” are the battery packs sold in automotive and discount stores. They are intended to allow you to crank vehicles with dead batteries, but often include other features in addition to a pair of permanently attached jumper cables—like lights, air compressors, even radios. What is important to us astro-junkies, though, is that they all have 12vdc cigarette lighter receptacles. The DC power cord for your scope will plug right into one. Also nice is the fact that these battery packs come with self contained chargers. The “Powertanks” sold by astro manufacturers/dealers like Celestron and Orion are, by the way, nothing more than jump starters.

What’s good? I don’t give a hoot ‘n holler about the lights and other gee-gaws; what I want out of a jump starter is amp-hours. 7 or 8 is too little. 17 is about right. More is better. Hokay, where do you get a nice 17ah jump start battery? If you simply must have an “Orion” or “Celestron” badge, go for it. It might be better to investigate the local Wal-Mart, however. Not only will you pay less for a 17 amp-hour model, you will often find higher capacity units in the 20 amp-hour range for about the same as the 17ah Celestron and Orion units.

Trolling motor batteries are a step up. It’s easy to find ‘em in capacities of 50, or 75, or more amp-hours. The catch? These “deep cycle marine batteries” are heavy. Their lead plates are thick, which allows ‘em to survive near total discharge without damage (good), but makes ‘em heavy indeed (not good for broken-down hillbillies). You’ll have to supply a charger, too, and an alligator clip-to cigarette lighter receptacle adapter.

What do I use? I currently have a 17ah unit I bought from Wal-Mart going on 8 years ago. It works fine for all my gear, with the only time I’ve ever run it down being the night I went slewing crazy with the CG5 at a public star party. I used to run both the telescope/mount and the DewBuster heater system off this pack via a splitter, but some years ago I added a second unit, a 20ah model, again from Wally-World, just for the heaters in the interest of guaranteeing plenty of observing time. If I’m running a laptop or a CCD camera, I pull out my 75ah trolling motor battery (and I really need another one or one with more amp-hours).

Eyepieces

Talk about a field wide open for speculation, preaching, and sometimes nearly fisticuffs. Wander over to one of the Internet astro-forums and have a stroll through the eyepiece board and you will see what I am talking about. Back in my day, kiddies, we knew a good eyepiece from a poor one, but we didn’t obsess about ‘em day and night. You bought what you could afford—be that a Ramsden or an Orthoscopic—and moved on. Today? For some boys ‘n girls eyepieces are a religion. Not that that’s a completely bad thing; quality eyepieces are important if you want quality performance from your scope. Which eyepieces do you get, then, when you want More Better Gooder—or even just “more” than the one or two oculars that came with the telescope?

This is a question that deserves its own blog entry, and I have done that in the past. Keepin’ things simple today, let’s just say there are three paths, Grasshopper. You can stick with the sort of eyepieces your scope came with, Plössls, most like. You might even kick it up a notch, buying something better than a Chinese import. Maybe a nice TeleVue Plössl. Plössls are not bad eyepieces; they can be very good eyepieces, and are all some observers will ever need.

OR…you can follow that time honored advice: “Buy the best eyepiece possible. You will never regret it.” And that can be good advice. Yeah, something like a Nagler or Pentax or (shudder) Ethos will not be cheap. You will howl. But once you compare the dead sharpness and spacewalk-style apparent fields of view of one o’ these to your 12mm GTO Plössl, you will find it difficult not to decide to buy one or at least save up for one. Even if, like me, you do a lot of Lunar and planetary work with a driven scope, you may still find you prefer a spaceship porthole to a soda straw.

Howsomeever, I do remember, believe it or no, what it was like to be a poverty stricken youngun. What if you have the yen for spacewalking but not the budget for it? You are a lucky duck. There are many, many wide and ultrawide (Chinese, usually) eyepieces in the astro-market square these days that will let you feed your fancy without breaking your back (or your marriage). Some of these eyepieces, like the William Optics Uwans, will perform very well in almost any telescope, including fast Dobsonians. Other, cheaper ultrawides won’t normally deliver sharp stars at the field edge unless they are used in SCTs or other relatively high focal ratio instruments. Only you can determine what’s acceptable. My advice is to look through some of the Chinese wonders at the next star party. For some specifics as far as individual ocular lines, see my aforementioned blog entry.

Dew Busting

If you live in a spot with heavy dew “falls” like your Uncle does, and don’t take steps to keep moisture off your optical surfaces, you won’t observe for long. A refractor or an SCT or an MCT, in particular, must be provided with a means to keep their big lenses dry. You can spend a few dollars on one of the 12vdc hair driers the astro merchants sell as “dew zappers” (and the truck stops sell as window defoggers), but that won’t keep you happy for long. When conditions are bad, you’ll need to keep zapping the derned corrector every ten or fifteen minutes.

The real solution is a set of dew heater strips. The first ones I saw were being sold by Orion near about twenty-five years ago. A little later, Jim Kendrick kicked it up a notch with his famous Dew Removal System, which included an adjustable controller. The ultimate in this old boy’s opinion, though, is Ron Keating’s DewBuster. Its control box is also adjustable, yeah, but unlike the original Kendrick, what you are adjusting is temperature rather than just the time power is applied to the heating elements. To that end, the ‘Buster comes with a temperature probe that’s affixed to the dew shield end of the scope. Temperature control saves batteries and makes it far easier to find the dew-banishing sweet spot. These days, Kendrick also sells temperature regulated outfits.

Barlows

Many beginners are both (naturally) uninformed about and (naturally) suspicious of the expensive widgets the astro-peddlers push. At first blush, a Barlow lens seems too good to be true. I mean, how ridiculous does this sound: “Yaaaas, my boy, just get yourself one of our Acme Ultra Barlows and it will not only increase the magnification of any or your eyepieces, doublin’ your collection, it will actually make your eyepieces better, yaaas.” Uh-huh.

The surprise for newbies? This is mostly true. Not only will a Barlow magically expand your eyepiece array, doubling it depending on the array of focal lengths you start with, the way one works, by making the light cone coming out of the scope longer and narrower—effectively slowing down a fast instrument—can indeed make many eyepieces perform better, banishing at least some edge-of-field gremlins. That’s assuming, of course, that the Barlow in use is a quality one. The good news here is that almost all the Barlows I’ve used recently, from Chinese no-names to the TeleVue Big Barlow, have performed remarkably similarly. My Orion Shorty is an absolute GEM, as a matter of fact.

Frankly, differences among Barlows are usually mechanical rather than optical. Better units are blessed with barrel threads and blackening to reduce light scatter, and compression rings rather than set-screws to hold eyepieces in place. Yes, more expensive Barlow optics have better coatings, no doubt, but derned if I can tell the difference. As with most things astronomical, you can kick things up with more $$$. TeleVue’s Powermates are equipped with additional corrective optics, and may do a better job in critical applications like high power planetary imaging. For most beginners, a nice Chinese Barlow from Orion or Owl or whomever is more than good enough.

Reducers

“If only,” Jane Novice muses, “there were such a thing as a reverse Barlow. Something to speed up my scope instead of slow it down. That would give me wider fields and lower magnifications without usin’ those doggone uncomfortable long focal length eyepieces.” Guess what? There is. Focal reducers have been around for years in their simplest form as a doublet lens screwed onto an eyepiece. Trouble was, they didn’t work well for visual use. The edge of the field usually went to pot. Astrophotographers did like ‘em, since the truly ugly part of the field was often outside the 35mm frame, and a little cropping in the darkroom could fix what remained. Visual observers? Not so much.

Until telescope guru Jim Riffle addressed the reducer problem, that is. Nearly two decades ago, Celestron enlisted him to help come up with a special reducer for their SCTs to allow the company to compete with Meade’s then-trendy f/6.3 OTAs without having to design and produce new CATs. The result was the Celestron f/6.3 reducer/corrector, which not only fattens up the old light cone, but flattens the SCT’s curved field. Just as with a Barlow, most eyepieces deliver better looking results in a CAT equipped with an r/c than in one without.

If you own an SCT of any make or model, you need an r/c, maybe even more than you need a Barlow. I rarely remove the 6.3 from the rear cell of my C8. If you don’t have an SCT? Folks have used the r/c on other designs, from Maksutovs to refractors, with sometimes good results. Don’t count on that, though. If you are considering this, try before you buy. Other options for y’all non-SCT troops? Baader has made a decent on-the-eyepiece focal reducer for years.

One caveat concerning SCT reducer/correctors: stick with Celestron’s (or Antares’) r/c. After Celestron’s success, Meade began cloning ‘em. Rather successfully—until lately. They changed the design of their unit some time back—by accident or intentionally—and many rear-cell setups, particularly those involving 2-inch diagonals, will not come to focus with one of the newer Meades in place.

Filters

Working our way down the list from “a must” to “a maybe,” we come to filters. Where these go on your shopping list depends on the where and what of your observing. If you have only a passing interest in the Moon and planets, for example, you might never get around to buying color filters. If, on the other hand, you observe the deep sky from places where the sky is not perfect, an LPR, “Light Pollution Reduction,” filter might come right after “eyepieces.”

I used to use color filters frequently when observing Mars, Jupiter, Saturn, and Venus. Threading one onto an eyepiece can, in certain circumstances, increase the contrast between the details you seek and the planet’s disk. A light blue filter can enhance Jupiter’s belts. A peach-colored one can make Mars’ mysterious dark features easier to pick out. A violet one might allow a glimpse of Venus’ incredibly subtle atmospheric features.

If you are a Solar System hound, I will certainly not council against you buying a few filters; they are inexpensive enough, with Orion’s models, for example, going for a mere 50 bucks for a set of four. Before you donate dineros to ‘em, though, I urge you to try a buddy’s filter on your fave planet and see whether you like the results or not. If you do, you might start with an 80A model (filter colors are described using the Wratten System, with “80A” being light blue). This color will do well on both Jupiter and Saturn, the two planets most of us watch the most. Me? I used to be a big filter fan. I find I don’t use ‘em much of late, though. That’s likely because I tend to do most of my Solar System “observing” with a webcam now.

Howsabout Moon filters? Forget ‘em. Whether as neutral density filters or the traditional green things, Moon filters do nothing to enhance your view of the Luna. All they do is attenuate her light. If the Moon is too bright for ya (the Moon at its brightest doesn’t e’en come close to being able to damage your vision), increase the magnification a little. Still want a filter? Use a color filter or a polarizing filter. One o’ these may at least enhance some detail as well as dimming down Selene.

Light Pollution Reduction filters are another story. If your skies ain’t all they oughta be, think seriously about gettin’ one or two. Even if the skies are good, LPRs can improve the appearance of DSOs. Before gettin’ down to cases, though, let’s dispense with a couple of newbie misconceptions. First, LPR filters do not make deep sky objects brighter. All they do is increase the contrast between the object of choice and the background sky. They do that by blocking wavelengths of light that come from bad, man-made sources while letting good deep sky light through. How? These filters have layers of special coatings that work together to reflect the bad light away while letting the good light through and into the eyepiece (most LPR filters screw onto the threads at the end of an ocular’s barrel).

Misconception Two is that LPR filters work on all deep sky objects. Unfortunately, they do not work on galaxies, star clusters, or anything else that glows via starlight (like reflection nebulae). The sad thing, y’all, is that the light of stars falls in the same range of wavelengths—the same “passband”—as the light from streetlights. A filter that is effective at reducing light pollution must also dim the light from stars.

Which filter is for you is easily the topic for a ‘nother whole blog. In the most general terms, though, most of you cats ‘n kittens should start with a UHC-type filter (Orion calls its filter of this type the “Ultrablock”). Like the original Lumicon UHC, these are medium strong filters that work on a wide array of objects—diffuse nebulae, planetary nebulae, supernova remnants. When you are ready for filter number two, think “OIII,” a narrowband filter that mainly admits the light from doubly ionized oxygen, the light of planetary nebulae. Many nebulae of other types also radiate in OIII, so these high-contrast filters can do a great job on much more than just planetaries. Stay away from mild filters. The Lumicon Deep Sky and Orion Sky Glow, for example, are too mild to do much for visual workers. They may be of interest to astrophotographers, however.

Yeah, yeah, I know, Skeezix. At least one company has been advertising a galaxy filter. Take it from me, there are no galaxy filters for the reason given above. Some folks are of the opinion that a sufficiently mild filter may reduce background skyglow enough without dimming star light too much to make island universes look better. Me? I’ve never seen it. Not even a little bit. Save your money.

Flashlights

You wouldn’t think a simple thing like a dadgummed torch would be so important. But in our game it is. If you don’t have a red light, or a red light that’s dim enough, you’ll ruin your night vision, your dark adaptation, and not see much of the deep sky (you don’t need a red light for the Moon or planets). Worse, show a white light or a bright red light at a star party and you may at best find yourself embarrassedly on the receivin’ end of a multitude of screams of “Douse that light!” At worst, you may find yourself escorted off the field.

What’s best? I used the prototypical astronomer’s light for many years. A 90 degree GI style flash that came with a red filter. As soon as LED lights began to proliferate, though, I got one in a real quick hurry. My light wasn’t very red. LEDs, in contrast, emit pure red light. I couldn’t adjust the brightness of my light. Most LEDs have variable brightness controls that allow you to keep ‘em at low brightness for most tasks, but crank ‘em up a bit for things like huntin’ that damned setscrew you dropped in the grass.

Specifically? Mostly, I’ve used a succession of Chinese-made LED flashlights. I especially like the ones that are equipped with both red and white (blue) LEDs. Once you are off the field, you can switch to white to keep from trippin’ over yourself on the way back to the bunkhouse. Just be sure you can easily tell which switch is for red and which for blue, or you may be hearin’ them screams again.

More specifically, I used a Celestron-branded light for years till it was melted when a Cyalume light-stick leaked in my equipment case. Amazin’ what hydrogen peroxide will do to plastic. When I went to replace it, I decided I should buy American this time, and picked up one of Rigel’s Starlite Minis at a star party dealer’s table. I felt good about supporting a U.S. firm—for all of ten minutes. I hung the thing around my neck and walked back across the observing field. When I got back to my scope, I reached for my new light and found out the cotton-pickin’ thing had fallen apart on the walk back. I located the guts by retracing my steps, but I wasn’t very happy; it wasn’t anything I did, it fell apart because it was cheaply made. The Mini was only twenty bucks, sure, but y’all know how I am. I replaced it with a SkyWatcher branded light I got from Jim Henson’s legendary Scopestuff.com.

Observing Table

Naturally, you gotta have someplace to set all the stuff you are accumulatin’. If you are just observing from the backyard, or don’t have much gear yet, a TV tray-table or one o’ them small folding aluminum camp tables (TV tray sized) Wal-Mart sells will do. Once you’ve got as much junk as I do, you will need MORE SPACE. What I’ve been using for quite a few years is one of the full-size camp tables you’ll find in most outdoor stores (and Wally-World, too). They fold in the middle to something card table sized, but when set up give you twice as much space as that.

Eyepiece Cases

Do you need an eypiece case? You need somewhere safe to store your oculars, but in the beginning that can be a two buck Rubbermaid box. Eventually, you will want something nicer, though. In cases, as in most things, I GO CHEAP. Yeah, these days you can buy fancy-dan wooden eyepiece boxes that cost two-hundred George Washingtons or more. Not my cuppa, but if you want one, go ahead, you ain’t gonna hurt my feelins. What may give you as much, or probably more, protection for your beloved oculars at a fraction of the price, though, is one of Orion’s aluminum cases (yeah, I know I keep sayin’ “Orion;” they really are the kings of accessories).

Just as good, and even cheaper, are the aluminum “tool attaches” from Lowes or Home Depot and the aluminum pistol cases from Academy and other sporting goods merchants. If you can locate one that comes with "pluckable" foam (so you can customize it for your oculars), you are good to go. I hear folks occasionally obsess over the smelly foam that these cases come with. Yeah, it smells funky, but there is no evidence of this doing pea-turkey to harm optics. Still worried? Air it out for a week, then.

Atlases

Finally, you’ll need something to help you find interesting things to look at. Even if you have a go-to scope. What else is interesting in the area of M51? Is there much in Aquila? What was that galaxy next to that star cluster in northern Cygnus? Your hand control computer won’t be much help with these questions; a star atlas will. What kind of atlas? The main question is computer or no computer?

If the answer is no-way-Jose, the time honored beginner’s choice is Wil Tirion’s Sky Atlas 2000 Plenty of stars to help you hop if you don’t have go-to, and plenty of objects to keep you interested whether you do or not. SA2000, as us oldsters like to call it, is available in several editions. I use the Deluxe. Its charts are a little bigger, and they are in color. You can go both brighter/shallower and dimmer/deeper than Sky Atlas 2000, but I don’t know that’s a good idea. A “mag 6” atlas like Norton’s don’t have many DSOs, and has too few stars plotted on too small a scale to be very helpful for star hoppin’. The deeper atlases like Uranometria 2000 and Millennium have too much everything. They are thick and annoying (for me) to use in the field. If you want More Better Gooder, it’s best to go to a computer program you can customize easily to fit your needs and tastes.

With the coming of cheap, light, power-sipping netbook computers, there ain’t much reason to eschew laptops in the field anymore. What do you need? In addition to the PC and maybe an external power source for it (you may be able to get an evening’s observing out of a netbook’s internal battery; don’t expect that from a full-sized laptop), you’ll need a red filter to put over the screen, since you can’t dim a PC’s screen enough or make it red enough to serve in the middle of a dark observing field. Yeah, I know most programs have night vision modes, but that ain’t good enough. Get some of the cheap Rubylith red film Mr. Henson sells. Finally, you’ll need a program, of course. I suggest you get your feet wet with a free one, Cartes du Ciel 3.0. It does everything (sometimes more) the expensive spreads do, and you may never need anything else. Yeah, I know it’s still in beta, but it is really ready to go now.

I could keep on, y’all, but we are out of space and time (sorry, Professor Einstein). If you want more/deeper discussion on accessories, may I be so bold as to suggest you glom onto a copy of my last book, Choosing and Using a New CAT? You’ll find, in addition to more words about more stuff, some ideas about homebrewing some of the accessories you need. Hey! The Christmas season is comin’; pick up an extra copy or three for your buddies (I’m joshin’, y’all…sorta).

Today at Chaos Manor South? It’s Saturday morning as I hunt and peck these words. I’m all ready to head out to the dark site with the 8-inch f/5 and get started on the observing features I’ve promised y’all. The weather seems to have other ideas, alas. If it don’t work out, guess I’ll just go back to Quake 4 on the consarned Xbox 360. Sigh.