Sunday, February 01, 2015

Takahashi EM-11 Temma 2 Jr. Review

I have had the misfortune of going through very many mounts through the years: two EQ-1's (one Orion and one Barska), two Vixen Polaris, one Vixen GP, a Celestron CGEM, Astro-Physics 600E QMD, Astro-Physics Mach1, Sky Watcher Star Adventurer, and now the subject of this review - the Takahashi EM-11 Temma 2 Jr.

And the one takeaway from these years of experience (and wasted money) is to buy the very best mount you can afford.  To that  I will now add the caveat: that you can afford and can carry.

To cut a long story short: the EM-11 is very smooth mechanically, is not sensitive to balance so far as I can tell, the polar scope is perfectly aligned, and it can turn out 10-minute guided subs like clockwork.  I can tell from the guiding graphs that it is not as smooth as the Mach1, and it definitely has much less capacity, but I can't carry the Mach1 and tripod with one hand.

The EM-11 has an amazingly low periodic error of about 7" peak-to-peak, which is quite an achievement given the small diameter of its worm wheel (Takahashi only guarantees 20" peak-to-peak).  Of course this isn't so amazing compared to the 3" peak-to-peak (< 1" with PEM) of my Mach1 - but the EM-11 is in the same capacity class as the Celestron AVX or Vixen GP, which normally have around 30" peak-to-peak periodic error.



This periodic error is of the same level as my Astro-Physics 600E QMD, but the EM-11 does not have periodic error correction.  However, the EM-11 has lots of ball bearings, which means its declination guiding behavior is good. Again - not as good as the Mach1, but good enough that I don't lose subs. Which is more than I could say for the AP600 (or the CGEM, but that goes without saying).

To repeat: this particular EM-11 performs better than my old AP600E QMD, albeit with a much lower payload.

I'm using the EM-11 with an old Gitzo G1340 Mark 2 Systematics tripod, which is rated for 20 lb.  Strictly speaking, the tripod is overloaded with the EM-11, about 10 lb of counterweight, and the William-Optics Lomo 80mm APO triplet, but the system is still stable.  Much more stable than the Star Adventurer on the same tripod: hence as an aside, it is the Star Adventurer wedge which is the weak point of that system.

A useful fact: this particular EM-11 has the low-latitude base.  It still cannot reach 1 degree latitude, but by slightly extending the two south legs of the tripod, I was able to get it down to 1 degree without need of a wedge. The additional tilt required is slight, and does not seriously compromise the stability of the tripod.

Another useful insight: the Gitzo tripod is overloaded with everything on it, but settling times are still under 2 seconds.  I tried removing the rubber tips on the feet and use the spikes, but settling times actually got worse.  The rubber feet act like Celestron vibration suppression pads, so should be left on.

Overall, the EM-11 meets my expectations of what a premium mount should be, i.e. it performs very well within its limits and does not require tweaking. It is not quite as refined as the Mach1, but there are no major concerns.

Note that all of my observations thus far are in using the EM-11 for imaging.  When imaging, you generally point it at one or two targets a night, and hammer away with a camera.  In fact, at this time, I have been using the EM-11 with its setting circles to find things (because I can't get the Temma 2 GoTo system working just yet). There's a bit of a retro feel to using the setting circles (kind of like using a film camera or manual-focus lens) but these circles work surprisingly well, so I'm happy.   This is OK, because you can spend five minutes finding an object if you will be spending the next four hours imaging it.

However, as a visual mount, to show the wonders of the night sky to people, the EM-11 is a terrible choice. When I moved from the Celestron Nexstar hand controller to the Astro-Physics GTO, it was like going from the 20th century to the medieval period.  The AP hand controller has a reputation for being built like a Russian tank - sturdy, but primitive.  The Takahashi hand controller is like the Stone Age.  There is no way to command GoTo from the hand controller.

I do have a Roving Networks Bluetooth serial adapter, and a SkyWire, so I can command GoTo's on the EM-11 using an Android or iOS device, but the mount as-is is incapable of GoTo unless you connect it to a computer or smart phone somehow.

My motivation for acquiring this mount is because the Mach1, for all its mechanical and electronic perfection, is a bit too heavy to be set up and taken down on a regular basis.  I would really like to expand the scope of my observation activities and the Mach1 is simply too heavy for casual observing.  I wanted a mount that weighed as little as possible, had GoTo (I have the Star Adventurer, and finding anything with that mount is a headache), and would be as nice as possible.

Of course in the lightweight mount category there is the Celestron AVX and iOptron ZEQ25, as well as the more upmarket Vixen Sphinx SXP and SX2.  I did try the ZEQ25 for some time, but it proved to be extremely sensitive to balance and I never liked the strange worm tension adjustment mechanism that also served as the clutch. I could never get the tension just right.

The EM-11 is way too expensive if purchased new (70% of the price of a Mach1, with one-third the payload) but I was able to acquire this one for a significant discount off the price of a new one.  It still is a rather expensive, low-payload mount, and I would not recommend it as a first (or only) mount, but for someone who already has that "perfect" mount and just wants more portability, it is a good choice.

My main concern was that no mount could ever match up to the performance of the Mach1, and I would be annoyed at the degraded user experience. Well, the EM-11 doesn't match up to the Mach1, but within its payload limits, it comes close, and the significantly lower weight is priceless.

Highly recommended! But not to beginning users.  The combination of the steep price, extremely user-unfriendly hand control, and low payload make the EM-11 a good choice for second or third mount. It's the Lotus Elise of mounts, small, finely-engineered, does what it does very well, but not terribly practical.

Now if only Takahashi would bundle the EM-11 with an actual intelligent hand controller, lower the price to $3000, and include a PEC recording capability, it would be more approachable - the Mazda Miata of mounts, as it were.

Saturday, November 01, 2014

Dell Inspiron 13 7347 Review

UPDATE 21 November:

Sadly, I can no longer recommend this particular model.  It has a severe design flaw in the touch screen that causes "ghost touches" - and based on my research and the reports of others on the Dell support forums, this is not an isolated issue.  Unit replacement most often does not address the issue, hence my unit is not a lemon unit.  Since Dell makes refunds very difficult and my feeling is repair or replacement won't help, I am keeping the notebook (but disable the touch screen when it acts up).

http://en.community.dell.com/support-forums/laptop/f/3518/t/19607216



I recently found myself in need of a notebook.  I haven't bought any such thing in over five years (the employer-supplied notebooks - a variety of Dell Latitudes and Toshiba Porteges - have proved more than useful).  However my office notebook isn't due for refresh yet, and I was getting tired of hauling its magnesium-skinned bulk around.

As my wife had recently gotten a Toshiba Portege Z30, which weighs an amazing 2.65 pounds - I decided that weight would be my major selection criterion.  But I also wanted a full HD (or higher) IPS screen, and a backlit keyboard.  And the notebook would also need to be cheap.

The above set of criteria are very, very hard to meet (even the Portege Z30 and ThinkPad X240 do not meet all of them, and these laptops cost a lot more money than I was willing to pay).

In the $1000 range, the notebooks which meet most or all of the above criteria are the Lenovo Flex 2 13 (which weighs about 4 lb), the Asus ZenBook UX303LN and recently-discontinued ZenBook UX32LN (the UX32LA and UX303LA don't have IPS screens), the Dell Inspiron 13 7000, and of course the Macbook Pro Retina 13.

I am no Apple fanboy (I have a lot of Android devices) but let's get this clear - the Macbook Pro Retina 13 is overall the best choice. It has the highest-resolution display (although not the highest-contrast); the fastest SSD (that isn't field-upgradable); the fastest processor (a special model i5 that only Apple gets); the best build quality; and by far the longest battery life. However, the 128GB SSD model (the lowest-end one) was at the high end of what I was willing to pay, and the 128GB SSD is small.

On paper, the ASUS UX303LN comes very, very close to the MacBook Pro Retina 13 in terms of specifications, and the ASUS has an Nvidia discrete graphics solution.  However it costs more than the 128GB SSD MacBook Pro Retina 13 (and a bit less than the 256GB SSD model) and doesn't come with an SSD.

The recently-discontinued UX32LN costs less than the base MacBook Pro Retina 13, also has discrete graphics, but no SSD.  Both ASUS devices weigh about 3.2 lb, slightly less than the Apple, but when you heft them in your hand, the difference in build quality is obvious (even though the ASUS notebooks also have aluminium chassis). The ASUS notebooks have decent battery life as well, but they can't match the Apple.

The Lenovo Flex 2 14 is probably the cheapest option you can get at this time (October - November 2014) with a full HD IPS screen.  It is a pentile screen and not as good as the other FHD screens. The large downside with the Lenovo is its 4 lb weight.  Battery life is acceptable.

My fourth option was the Dell Inspiron 13 7000.  It is available in two models, a 1366x768 IPS, and a full HD IPS. The latter model costs more (about the same as the ASUS UX32LN) and has the downside of not having a discrete graphics solution (it uses the Intel 4400).

I made a handy comparison guide of these notebook candidates:


The last parameter is how long (in hours:minutes) each notebook could loop the "Big Buck Bunny" movie before running out of charge.  It is obvious from this comparison that the MacBook Pro Retina 13 is the best overall choice, but also the most expensive, and this is the base model only with a 128GB SSD. Prices are in SGD, but the other ratings are from notebookcheck.net.

Note that the usual suspect high-end notebooks (Lenovo ThinkPad X1 Carbon, Lenovo ThinkPad X240, Lenovo Yoga 2, Toshiba Portege Z30) are not on this list, for the simple reason that they cost far more than I am willing to pay.  It was quite a shock to learn that high-end notebooks actually cost more than their Apple competition.

What the above spreadsheet does not show is the level of build quality of these notebooks, something you can't see unless you physically handle them.  As I have already mentioned, the MacBook Pro has the best build quality, the best trackpad, and the best keyboard.  It's the most solidly put-together.  The Lenovo Flex 2 14 is also pretty solid, but its weight goes against it.

From the spreadsheet, it looks like if you can't or don't want to spend money on the Apple, the ASUS is the next best choice, and on paper it is.  However, it doesn't feel as well put-together.  The reason I ended up with the Dell is because the Dell simply feels more solid in the hand, for the same price, in spite of the weak integrated Intel Graphics.

I used to have an ASUS with Radeon graphics, and - it's not all it's cracked up to be.  Certainly you can play most modern games, but the battery life with the discrete graphics enabled is a dismal one hour or so.

Now that I've put a reasonable amount of time into the Dell, these are the conclusions I can make:
  • The screen is very good; certainly the Retina is better, but having used 1366x768 matte TN panels for almost a decade, this screen is an eye-opener.
  • The build quality is above average; as the notebookcheck review points out, the build quality is more Latitude-level than Inspiron-level and is the main reason I chose this model over the ASUS UX32LN which has a better spec and significantly longer battery life.
  • The Yoga-like 360 degree rotation (that turns it into a huge ungainly tablet) is actually a useful gimmick.
  • However, Windows 8.1 on this device doesn't quite cut it as a tablet OS. In spite of the vastly more powerful processor, my Nexus 7 2 works better and is more responsive as a tablet than the Inspiron. However the Nexus 7 2 can't run Microsoft Word, so there is that.
  • The touch screen is less responsive than that on the Nexus 7 2 (which also is a Full HD IPS touch screen). It is sometimes necessary to press harder or multiple times (particularly with the included passive stylus) to get click registration.
  • The track pad on the Inspiron 13 7000 is of mediocre quality, particularly the click-over feel is rough and the actual feel as you move your finger over the trackpad is also rough. The track pad on my employer-issued Dell Latitude E6320 is far, far better, and the glass pad on the MacBook Pro is beyond comparison that it's not even funny.
  • The keyboard is also only acceptable, my employer-issued Latitude E6320 is also better. However the Inspiron keyboard is illuminated (only two illumination levels however). The notebookcheck review noted the excessively-small backspace key.  Another niggle is the absence of Page Up and Page Down keys; you need to press Fn-Up Arrow and Fn-Down Arrow. I can still type at a reasonable speed on this keyboard, so it's acceptable. It is important to point out that the Dell Latitudes are a higher grade of notebook and generally cost much more.
  • Of all my candidate notebooks, the Dell has the worst battery life (four hours on Big Buck Bunny).
  • However the Dell Inspiron 13 7000 is reasonably light, practically the same as the MacBook Pro Retina 13.
In conclusion, the selection of (approximately) 3 lb notebooks is rather thin, particularly if your budget is limited to around $1000.  You can't get perfection in this price class, unless you're willing to pay a bit more and live with a small SSD in the MacBook Pro Retina.

Another conclusion I've come to - if you are spending $1500 and up on a flagship notebook, forget the so-called premium notebooks from Lenovo, ASUS, HP, etc.  Just get an Apple device, they actually provide better bang for the buck and unsurpassed battery life and build quality. That's assuming your applications run on MacOS X.

So the Dell Inspiron 13 7000 is a good compromise, but a ways off from perfect.  It was the least compromised choice for myself, but someone who wanted longer battery life and a discrete graphics solution would probably find the ASUS UX303LN or UX32LN to be a better choice overall.

UltraBookReview has a good review comparing the ASUS UX303LN to the MacBook Pro Retina 13. The mere fact that the ASUS is favorably compared to the Apple device is already quite a big vote in favor of the ASUS. The UX303LN simply was a bit too much money (about $300 more than the Inspiron 13 7000) for me, and the UX303LA while about $300 less than the Dell, didn't come with an FHD IPS screen.

Saturday, October 11, 2014

Skywatcher Star Adventurer Tripod

I wanted to find a more suitable tripod than the flimsy Benro A350EX, and less clumsy than the Vixen Polaris tripod.  I initially purchased a Sirui N2204X, carbon fibre, with detachable leg, etc. It was not terribly stable (about 4-5 seconds damping time) in spite of its alleged 33lb rating.


But, due to a 20% discount promotion at KEH, I was able to purchase a beat-up Gitzo G1340 Pro Studex tripod, without centre column.  That last part is important, because the centre column induces instability. Coupled with the rubber bungs on the Gitzo's feet, damping time is now 2-3 seconds. The Gitzo is actually more stable than the larger aluminium tripod from my Vixen Polaris. This is a tripod that's rated 20lb.  The total weight of this setup (Stellarvue SV80ED, diagonal, eyepiece, mount, and tripod) is just a hair under 20lb, and can easily be lifted and carried around.

Of course, Gitzo tripods are eye-wateringly expensive new; a major drawback.  A new 2-series Gitzo carbon tripod and the Star Adventurer would cost very close to an Atlas or EQ6, so definitely not cost-effective anymore.


I guess we all can derate Chinese tripod weight ratings by 50% now..

Sunday, September 21, 2014

Sirui R2004 Tripod for Astronomy

I was looking for a lightweight tripod that would fit in carry-on baggage and be useful for my Star Adventurer.  The Sirui R2004 tripod seemed like the perfect fit: it is 520mm collapsed (will fit diagonally into a carry-on suitcase), weighs about 1.8kg, and is rated for 15kg.

It also only costs S$85 ($68 US) which is mind-bogglingly cheap.

All of the Sirui 2-series tripods (R2xxx, N2xxx, T2xxx) have 28mm thick legs, only differing in the number of leg segments, whether one leg can be detached to form a monopod, and the material of the legs - aluminium or carbon fibre.  The R2004 is the most basic model, and hence the cheapest.

As payload I used a Sky Watcher Star Adventurer, APM Lomo 80mm apochromatic triplet in a William Optics tube, 2" Televue diagonal, and a 4mm Vixen LV eyepiece giving 120X magnification.  The total weight of all this is 8 kg, well below the alleged 15 kg capacity of the Sirui tripod.

The long and the short of it: at 120X, it takes a mind-boggling 8 seconds for vibrations to damp out after touching the focuser. Hence this tripod is wholly incapable of carrying the mentioned load.

As a control, I used the short aluminium tripod from a Vixen Polaris; this has the benefit of much larger legs, is much shorter, and has a tray to reinforce the legs.  With this tripod and the same mount and telescope, damping time is reduced to 4 seconds, which in my opinion is still excessive.

In short, the Star Adventurer is overloaded with the Lomo 80mm, and the Sirui tripod is also overloaded with an 8 kg load. Of course 120X is equivalent to 6000mm focal length.  So the Sirui tripod and Star Adventurer may still prove useful for astrophotography.  But as a visual setup for planetary, this combination is unusable.

Friday, July 25, 2014

Sky Watcher Star Adventurer, Part II

I had an old counterweight shaft and counterweight for an EQ1 mount lying around (the EQ1 had already broken some years back and I had thrown it away).  The shaft has a large-pitch thread on one side, and an M6 tapped hole for the toe saver on the other side.

I drilled out the M6 tapped hole with an 8mm bit, then epoxied an M8 bolt into the hole.  I then cut off the head of the bolt leaving the M8 threaded portion exposed.  A more robust solution would have been to drill out the M6 hole with a 6.5mm or 7mm bit, then use an M8 tap to cut threads into the hole.  The M8 bolt would then screw into the threaded hole, a more secure fastening than just epoxy.  But I did not have an M8 tap handy.   The epoxied bolt seems secure enough (I used Araldite brand epoxy) and hasn't wobbled through a 2-hour plus testing session.



With the stock EQ1 counterweight, the Stellarvue SV80ED still would not balance; however the result is much more in balance than having no counterweight at all.




However, the counterweight did not really improve the guided performance, or reduce the periodic error to in any meaningful way (and I did not expect it to).  Guided performance is still around 2" RMS, which I believe is the best this mount is capable of.  Hence it should be used at a pixel scale of 4" to 6" per pixel, or 200mm to 300mm focal length.


A longer sampling period has confirmed that the worm fundamental is 10 minutes, hence the worm wheel has 144 teeth (like the Vixen Polaris, Great Polaris, and CG-5).  This was confirmed by a poster on Stargazers Lounge who tore down the Star Adventurer.  The fundamental is about 30" peak-to-peak.



I got a better polar alignment this time (as shown in the minimal DEC drift in the graph above) and in the process noticed that the polar scope is pretty well-aligned - better than my PASILL3.  It's not perfect, but it's good enough that I'm not going to mess with it.