Celestron StarSense Explorer dx 102az: Best Beginner Telescope?

What is the best beginner telescope? That's a question that all beginners ask . . . but it's also one that often crosses the minds of more experienced astronomers. In my case -- after more than 30 years of casual astronomy -- I still consider myself a beginner. Maybe I'm an advanced beginner, but still a beginner.

My opinion is that the best beginner telescope -- bar none -- is this one (if the price is under $400):

Celestron StarSense Explorer dx 102az

I'll go one step farther and say that this is the best grab-and-go scope on the market today. It has several very nice features: 

1. It's a refractor so there is no fussing with collimation. And you don't need to worry about your primary mirror collecting dust at the bottom of a deep tube. The 102 mm objective grabs enough light to see plenty of dim, fuzzy star-clusters and galaxies. The 660 mm focal length is just enough to allow magnification for planetary observing.
2. It has a simple alt-az mount. These mounts don't require counterweights so the entire scope can easily be lifted and carried to different locations in a suburban yard. Those pesky trees and neighborhood lights can be rendered less bothersome when a scope is so easily moved. The whole rig weighs less than 15 pounds.
3. The red-dot finder is a classic (fairly simple) system for locating objects in the night sky.
4. The included 25 mm Plossl eyepiece provides low 25x magnification with a wide field of view (2.3 degrees) and a pleasing 3.9 mm exit pupil. All of the Great Orion Nebula fits nicely into this field of view.
5. The included 10 mm Plossl eyepiece provides useful higher magnification (65x). This lets you enjoy Jupiter and its moons, knocking the brightness down enough so that you should be able to see some banding and the shadows of crossing moons.

But there are plenty of telescopes with those features (including my own grab-and-go). What sets the StarSense Explorer line of scopes apart is the "killer" phone app. Celestron has created a very clever mount to hold your cell phone on the altitude axis of the mount. A mirror directs of phone's camera lens toward the exact spot in the night sky that your scope sees. The StarSense app (which is similar to Celstron's classic SkySafari and SkyPortal app) uses arrows to guide you as you shove the main tube until it is aimed directly at any deep-sky object you select from a menu or from the star chart on the phone's display. Once you have selected something and pointed the scope at it, the app gives you an abundance of information, frequently including a brief audio lecture. One word of warning: you do need a modern phone (post-2016) that includes both an accelerometer and a gyro to get the directional pointing to work.

So that's great. For just $400 I could buy a brand-new grab-and-go scope with all the benefits and none of the drawbacks of a fully computerized scope. The thing is -- I already have a mighty nice grab-and-go scope:

That's a heavily modified Celestron NexStar 102SLT Computerized Telescope. I ripped the guts of the motorized drives out after knocking the whole rig over in the dark one night. I removed the red-dot finder and installed my foam finder. And, if you look closely, you'll see that I installed a mount for my phone right on top of the tube, as well as an inclinometer and setting circle. This means that the features of the SkyPortal app work just fine. Using the altitude and azimuth values provided by SkyPortal, I can aim at any deep sky object and be pretty sure I'll find it in my low-power field of view. The app also gives me a great star map to consult in the dark, and it gives me almost encyclopedic access to written and audio information. 

I still find my paper charts and printed notes are important to me and I'll still continue to get lost in space, . . . but the app, the inclinometer, and the setting circle can certainly help me find my way out again! 

DIY Telescope Finder Scope -- Better Than a Telrad?

All astronomers face one big problem: How do we find anything in that enormous night sky? It can be hard to find the full moon when just panning around at 25x magnification! Finder scopes are the answer, and I would say that the Rolls Royce of finders is the combination of a well-collimated laser along with a well-colliminated 10x50 right-angle monocular. But 10x50 finders are heavy and expensive. Lasers rely on battery power and present risks of causing eye damage to others if used inattentively.

Red-dot finders are a less expensive alternative, while Telrads cost a little more but are easier to use. Both rely on batteries. Both produce unmagnified direct views of the sky. The problem with the red-dot finder is that it is easy to knock out of alignment and it is sometimes surprisingly hard to actually see the red dot. Sometimes I have to crane my head around uncomfortably for quite some time at a very awkward angle. The Telrad pretty much solves those problems.

But I think the DIY finder pictured above is even better. It weighs almost nothing, it costs next-to-nothing, and it is surprisingly easy to make. It's easy to align. You never have any problem pointing at the right patch of sky. And you never need batteries -- though a red flashlight can be handy and make it work exactly like a Telrad. Here are some pictures of the finder mounted on a short-tube 102mm refractor:

You can see, by the way, that I've got this scope "souped-up" with a DIY 10x50 finder that I made from a pair of cheap binoculars, some old mailing tubes, and plumbing parts. I'll probably leave the 10x50 on the scope as a convenient way to scan the sky at low power; but I don't need it at all as a finder scope!

I may make a YouTube video about constructing this foam&wire finder, but until I do so, here are some instructions that probably tell you all you need to know:

Instructions

1. Cut out and sand the edges of a 2" diameter cylinder of 1" closed-cell foam: One each for front and back sights. (Closed-cell foam is sold in sheets at most lumberyards. It is often pink or blue and sands much better than the white open-cell foam.)
2. Sand the bottom of each foam cylinder to the radius of the telescope tube. Wrap a sheet of 60-grit sandpaper around a cup, pitcher, or plastic container of the proper diameter.
3. Cut three 7" lengths of copper wire (18 gauge). Grab with vice-grips 1" from one end and right at the other end. Twist the three strands together. Do the same thing with 3 strands 6" long.
4. Bend the stranded wire over a 1" broomstick so that the inch of the untwisted end is free. Twist tightly around the broomstick to form the eyesight. Bend and twist the 6" strand around a 3/4" screwdriver handle or something similar.
5. Slightly spread the untwisted strands on the end of one eyesight. Then (while pushing the ends together slightly) shove them into the center of one of the foam pieces. The wire should spread as you push it in, thus holding the eyesight firmly in the foam. Repeat with the other eyesight.
6. Spread 1/8 teaspoon of baking soda onto the top of the foam and push it into any gaps where the wire enters the foam. Scrape off all the baking soda that cannot be pressed into the holes.
7. Put a couple of dabs of gel superglue onto the wire and baking soda where it enters the foam and spread it thoroughly and forcefully into any gaps.
8. Paint the foam with black enamel (or any other preferred color).
9. Put a piece of carpet tape onto the bottom of each eyesight. Stick the front eyesight onto the tube where wished. Focus the telescope on a distant object and attach the rear eyesight where it lines up. Collimate by bending the wire loops as necessary.
10. Now, enjoy the best finder scope that money can't buy!

The Great Escape -- Observing Notes for Andrew Johnson's Mag 7 Star Atlas

--click on image to download--

This free download features:

• Utility as a companion to Andrew Sullivan's Mag 7 Star Atlas or in conjunction with any other star atlas like the Sky and Telescope's Pocket Sky Atlas.

• An all-sky constellation map indexed to the various star charts in the Mag 7 Star Atlas.

• Quarterly maps of the night sky (Dec 15, March 15, June 15, September 15).

• Basic data about deep sky objects on the star maps.

• Links to wonderful astrophotographs of the best open clusters, globular clusters, galaxies, and nebulae.

• Lots of miscellaneous information -- historical anecdotes, HR-diagrams, measurement methods, etc.

• Links to Ian Ridpath’s Star Tales, which has delightful narrations of the myths associated with each constellation.

Increasingly, I have felt a desire to reduce my connections with the endless turmoil of politics. Not only do we have to put up with politics in elections, but also in medicine and even weather forecasting. Phrases like "the science is settled" drive me to distraction. Probably nothing in science is more "settled" than Einstein's Theory of General Relativity, but true physicists are all delighted by the slightest crack in the wall of evidence for the theory. The essence of science is skepticism and doubt.

I've always loved astronomy because it is such a foundational science and yet the scientists all seem very pleased with themselves if their data only turns out to be wrong by an order of magnitude or so. Things are always moving very fast. What we think we know today will probably be greatly modified within a decade.

Amateur astronomy is a way of stepping through a door into the enormity and delightful strangeness of the universe. When I haul out my telescope, I almost immediately find myself lost as I try to star-hop from the tiny dots on my sky maps through the teensy burning embers in my eyepiece. Sky maps are essential tools -- especially for those of us who prefer finding our own way to using a computer-guided telescope. Astronomy is a learning hobby. Learning to use the charts is one part of it. But then, too, learning about the nature of the stars, star clusters, nebulae, and galaxies is even more fascinating. 

I've got a whole shelf of different sky atlases that I have tried over the years, ranging from a home-made laminated Star Wheel, to The Sky Crew Star Atlas created by my friend Paul Qualtieri, to the hefty Jumbo Edition of Sky & Telescope's Pocket Sky Atlas. None were quite what I wanted. The star wheel is handy for naked-eye observing, but too small for use with a scope. The Jumbo Edition is too heavy and inconvenient.

Last winter I discovered Andrew L Johnson's Mag 7 Star Atlas, and it is just what I have always wanted. It prints out beautifully as 21 individual maps on 8.5" x 11" paper. On any given night I'm only going to need three or four of those maps. I can slide each of them into a separate plastic sleeve and have completely dew-proof charts to use for the evening. 

The only thing missing was the information -- the knowledge, the tiny bit of nightlore necessary to serve as a useful reminder or to ignite a burning need to go back to the books. I decided to create what I felt was needed. I've done so in a 19-page booklet crammed with data . . . and hopefully enlivened with the kinds of curious anecdotes that will add more depth to an evening of observing. The idea is to stuff one of these pages back-to-back with the associated chart into each of your three or four plastic sleeves. On one side you have a map of the stars and deep sky objects. On the other side you have information: stellar classifications, distances, magnitudes, angular size, and much more. In the on-line version there are links to beautiful images taken by amateur astrophotographers for most of the deep-sky objects. 

If you find the booklet useful or have ideas about how to improve it, please comment below.

Once again, you can download my free Observing Notes for Andrew Johnson's Mag 7 Star Atlas here -- or by clicking on the cover image at the top of this page.

Breeding Spotted Salamander (Ambystoma maculatum)

On Friday, February 7, 2020, I achieved a long-awaited personal "first"! I saw Yellow-Spotted Salamanders searching for mates in my pond. I had long known this must happen, but -- unlike frogs -- salamanders do not sing loudly while calling for companionship. They are silent searchers. Yet salamanders there must be. I had seen one on several occasions in a hole under the cabin, and my grandson Adam had once shown me a salamander tadpole he netted in the pond. So I was very excited to actually see them in the pond.

You might think that I have chosen a rather poor photograph for this blog page -- and in most respects you would be right. But if you use just a bit of imagination, you can see the large (7") yellow-spotted salamander crawling just over the top of the submerged lily pads. You can also see that some of the submerged lily pads have been scoured clean of the brown pond scum and show up lime green. That scouring was caused by the movements of multiple salamanders crawling around searching for mates. In future Februaries I will try to remain alert and look for salamanders whenever I see the tell-tale lime green leaves.

Here is an image from the web of a more clearly visible yellow-spotted salamander:

My Bike of Broken Pieces

I've been rough on bike frames lately. Every cyclist occasionally "drops the chain." This happens as one is shifting in or out of the chain-rings. If the chain drops to the inside, it's rarely much of a problem except that the cyclist has to stop, put the chain back on, and wipe his greasy hands on some inconspicuous part (usually the butt) of his black cycling shorts. If the cyclist drops the chain to the outside, it's usually even less of a problem. Shifting down -- from the 50-tooth ring back down to the 34 -- and slowly turning the pedals almost always succeeds in "pedaling the chain back on." It's a trick all avid cyclists learn.

But it doesn't always work. In some cases the chain gets wrapped around or snagged in the rear cassette and trying to pedal it back on can result in a broken derailleur hanger. No big deal, right? Replaceable derailleur hangers are designed to break so that other parts of the bike (the frame, the rear mech, etc.) are protected. But things don't always go as intended. Three times in the past couple of years, I have broken my hanger and had to replace a variety of other parts. The last time, my chain got so tangled in the rear cassette that the wheel locked up at 20 mph, sending me into a long skid down the blacktop. Fortunately I kept the bike up, but I later measured the skid mark at over 20 feet!

That lock-up caused a broken derailleur hanger, seriously bent front and rear mechs, a chain bent in multiple places, and a cracked seat-stay on my carbon CR4. My initial reaction to all that damage was to declare the frame a total loss and to use the salvageable parts (shifters, handlebars, brakes, pedals, bar tape) to upgrade the components on my ancient Giant OCR3 (22 pounds when new in 2001, 20.5 after the upgrades).

With all the parts stripped from my CR4 crankset-frame-and-fork, I was able to appreciate how incredibly light it was. And I got to thinking. I've been making stuff with fiberglass for over 40 years -- most recently my CLC Shearwater Sport Sectional and my Northeaster Dory. How different could it be to repair a fairly trivial crack in a carbon fiber frame-set. The seat-stay was still very stiff. Wrapping it with a couple layers of carbon fiber cloth and soaking that cloth with epoxy resin should make that seat-stay as strong as new. I spent $30 on Amazon and got a small roll of carbon fiber cloth and and some small bottles of resin and hardener.

The epoxy repair went very well. I could have done a lot of sanding and some additional epoxy work to make the repair look pretty, but the sanding would have weakened the area by cutting into some of the carbon fiber, and the additional epoxy would have added weight with no increase in strength. So my repair looks like a repair. Big deal!

Here is a picture of the cracked area before the repair:

To begin riding the bike again, I needed to replace multiple links on the bent chain, throw away a badly bent front derailleur, straighten the bent rear derailleur cage, piece together some bar tape, and salvage a pair of old SPD pedals. The pedals should look like this:

But the bolt holding on the spring mechanism of one pedal had snapped.  Even though I couldn't figure out a way to repair the pedal, I thought it just might work without the rear portion, functioning like an old-fashioned toe-clip. 

Sliding the tip of the cleat under the metal toe-retainer should hold one's foot in position fairly well, as long as the force of the pedal stroke is forward and down. Sad fact is, I'm not a sprinter and I generally don't pull up on my pedals.

So I built the bike up.

Because there is no front derailleur, it's a 10-speed bike with a 34-tooth chain-ring and an 11x28 cassette. How big a deal is it to have only a 34 up front? In hill country it's not a big deal at all. At a cadence of 90 rpm, the bike will go about 21.8 mph on flat ground. But 20 mph is the fastest time trial speed I've ever been able to maintain. I'm sure I'd like a 50-tooth chain-ring if I spent a lot of time "sucking wheel" on group rides. I don't.  I almost always ride alone or side-by-side with a single friend. I really don't like holding the wheel and staring at someone else's butt for long periods of time! When the road slopes downhill, I now stop pedaling and get into an aero tuck; the bike accelerates to nearly the same speed I could maintain by pedaling in the 50-tooth chain-ring.

So here are my three conclusions from this experimental effort:

1. A modern road bike can be changed to a 10-speed with almost no loss in its capability. In fact, the single chain-ring means lighter weight, greater simplicity, and more reliability. Dropping a chain is now almost impossible, as is breaking a derailleur hanger. Fussy front derailleur adjustments are a thing of the past.

2. Carbon fiber frames can be repaired easily -- at least if the cracks are minor and the frame is still intact and strong. Even so, I would not attempt to repair a cracked fork; if that repair failed, the crash would send me sailing into a forward endo.

3. Modern clipless pedals should be adjusted so that they release very easily. Hardly anyone pulls up hard on the pedals. There is no need for those embarrassing falls when one can't unclip quickly enough to put a foot on the ground. 

Update 5/31/202: With a couple of minor changes, my bike of broken parts has once again become my main ride. First, I put on a different set of clipless pedals to improve my connection to the bike. But I do have the springs on the pedals adjusted so that they release very easily. Second, I replaced the 34-tooth chainring with a 39-tooth ring. This will allow me to crank it up to 25 mph on the flats. I'm also using the superlight American Classic Sprint 350 front wheel that originally came with my Motobecane Le Champion SL. If I remove the unnecessary 50-tooth chainring, I'll save another ounce or two on what now seems to me to be a very sweet setup!