Sunday, May 31, 2015

 

The Zhumell Z10


As you know if you've been reading here lately, I’ve returned to my visual observing roots. The telescopes I’ve been using most for that have been my two Dobsonians, an 8-inch f/5 of Konus heritage, and Old Betsy my 12-inch truss tube telescope who was once, long ago, a Meade StarFinder. Both are good telescopes, but, frankly, the 8-inch is sometimes a little small for my compromised backyard and the 12-inch a bit of a pain to set up for my less formal observing runs. What about something in-between, I thought, like a nice 10-inch f/5?

Since we’ve moved to the suburbs, I’ve pretty successfully focused on selling/giving away telescopes rather than acquiring more (I still have an RV-6 I’d like to find a home for locally), so I didn’t feel guilty about bringing a new one into the house.

God knows there’s no shortage of bargain 10-inch Dobs. Synta and GSO, the two big Chinese telescope makers, have seen to that. If you want to keep the price down, both have 10-inchers to tempt you.  Synta selling under its own SkyWatcher brand and to their heretofore main outlet, Orion (Telescope and Binocular Center), where Syntas are sold under that company’s logo in a variety of configurations ranging from basic push-to scopes (what I had in mind), to Orion’s “Intelliscope” DSC rigs, to full goto.

Then there is GSO, who markets their Dobsonians under the Zhumell brand and to a few independents like Alabama’s Opticsmart, who tweak and tune the GSOs as the Apertura Dobs. Oklahoma's Astronomics also occasionally dispenses them under their Astro-Tech brand as well. Normally, however, Zhumell, is distributed by that Internet sales giant Hayneedle from their telescopes.com outlet (plural, singular is Orion’s website).

The Apertura Dobs were a natural, I thought, but had a couple of strikes against them. Opticsmart is in Alabama, so I’d have to pay sales tax. Also, while I admired the extras of the Aperturas, flocking and other such niceties, I wanted to keep the price as low as possible.

I liked the white tubes of the Astro-Tech Z10s, and Astronomics is an outfit I've bought from frequently over the last 20 years, but, as is common with their Astro-Tech brand lately, the Dobs were out of stock with the website mentioning a "waiting list," which didn't sound good to impatient me.

How about Orion? Certainly an OK choice but for two things. Their cheapest house-brand Synta 10-inch , the XT-10 Classic, is 600 bucks, 100 more than the comparable GSO and also a little plain Jane compared to the Zhumells.

There is no question you get more for your money with the GSO Dobsonians, beginning with adjustable tension altitude bearings that are considerably more sophisticated than the XT10’s spring-attached-to-the-bearings-trope balance aid. Said altitude bearings on the GSOs can also be moved forward or back with reasonable ease to cure most imbalance problems. One thing that may give prospective GSO purchasers pause is the fact that the Dobs use a lazy Susan bearing for azimuth rather than Teflon pads on Formica. More on this shortly.

It’s in the fittings and accessories that the GSO scopes really pull ahead. The two-speed Crayford of the GSOs is clearly superior to the single speed unit of the Orion. The Z10 10-inch features a 50mm RACI finder that’s quite a step up from the Orion’s red dot job. There’s a battery powered fan to speed cool down with the Zhumell—that’s an extra cost option on the Orions. There are two eyepieces shipped with the Z10 including a 2-inch 30mm that is not bad as a finding eyepiece I was given to understand (the Orion comes with a single cheap 25mm Plossl). Oh, and the GSOs even sport laser collimators, if that blows your skirt up.

Another alternative would have been Synta’s series of collapsible SkyWatcher Dobsonians. While these are rather nice instruments, they had one thing against them. Prices. 699 for the 10-inch while fair and all—the scopes are unarguably more attractive and better accessorized than the Orions—was at the limit of what I wanted to pay. I was also not convinced the collapsible nature of the scopes would add much value for me. An upper cage assembly that slides along three truss poles does make the 10-inch more compact, but a 10-inch f/5 just ain’t that big to begin with.

Synta/SkyWatcher has also introduced a line of traditional, non collapsible Dobbies. These were just coming on line however, and didn’t seem widely available. At at any rate, they didn’t seem to have features that would impel me to choose one over a GSO.

So a Zhumell Z10 it would be. When I’d made my mind up, there was really no drama involved in ordering. I got on the Telescopes.com website, turned over my credit card number and I was done. The scope was 499 with free shipping, but I elected to spend a little bit more for FedEx ground service. The final damage was just a smidge, and only a smidge, over 500.

The most significant thing about my order? The way Hayneedle just has its act down. I ordered the 10 on Thursday morning and it was on our porch Saturday afternoon. This is the third item I’ve bought from these people and their service is unparalleled no matter what you buy, whether a nice mid-century modern clock like the one over our mantelpiece, or the Happy Hand Grenade 100-degree AFOV eyepiece I got from them a couple of years ago.

The only thing I was a little worried about was whether they’d get the big 10-inch to me in one piece. There was a hole in the OTA’s box when it showed up Saturday just before 4 p.m., but the inner carton had not been penetrated and all was well. With Dorothy’s help, I got the two boxes (one obviously containing the mount) into the Sunroom, the usual site of my equipment assembly.

How difficult was the procedure? Not difficult at all if you’ve assembled Ikea furniture or similar. I did make one mistake with the front board of the rocker box and had to back up a little at the very end, flipping that board around so the handle mounted there was secure, but, mostly, the way to proceed was clear once I downloaded the scope’s manual. Yep, there isn’t one in the box, you need to download and print a .pdf. There’s also an assembly video which is really all you need to ensure success.

Actually, there’s not a lot to do nor a lot to go wrong when assembling the mount. Rocker box sides and front go together with long screws in pre-drilled holes. Three feet go on the ground board. Rocker box and ground board go together with a pivot bolt.

There is one thing about the mount you may or may not like, which I hinted at above. The Synta Dobs still rely on the traditional Teflon and Formica for the azimuth bearings of the scopes. The GSOs, on the other hand, use large lazy Susan bearings. How much you will like this arrangement depends on you. I’ve always preferred super easy azimuth motion, but some folks will not like it. This is both a point in favor of and against the GSOs depending on your perspective, as all their Dobsonians use this bearing system for azimuth.  

Time to get to the good stuff, the big OTA and its accessories. I assembled the tube with the side bearings at their mid positions (zero on the provided scale) as a starting point. You must remove tube from rocker to adjust the bearing positions, but that isn't a big deal.  I then horsed OTA into rocker. Make no mistake, yes, this is just a 10, but a 10-inch solid tube (steel tube) Dobsonian is no lightweight. Make sure you want to handle one or back off to an 8-incher.

Minor complaint? Like my old friend Pat, I've come to believe after all these years that white is the best color for a telescope tube. Thermally cooperative. Doesn't show fingerprints easily. Looks clean and elegant. Nevertheless, all cats, and even Newtonians, are, like the Z10, black in the dark, so I guess black is OK too.

Naturally I needed to collimate, to align the optics of this f/5 telescope so it could perform its best. I had heard tales about the accuracy or lack thereof of the included laser, so decided to leave that for later, and used my good old Chershire/Sight tube to dial the scope in.

The secondary (adjusted with Phillips head screws, unlike the Synta scopes, which use Allen head screws) needed minor tweaking, which was also all the primary required. The bolts for the primary are serviceable and consist of three knob headed and spring loaded adjustment bolts and three knob-headed locking bolts. Naturally, as with the old push-pull cells, the lock bolts have to be tightened sequentially and by the same amounts or you change the collimation set by the adjustment bolts. I ruled the collimation of the scope very easy. Surprisingly so.

Bob’s Knobs are available for both secondary and primary and I may take advantage of that option depending on how the telescope holds collimation. Stronger springs are another option that Scopestuff and other sell, but I thought the springs worked OK. The primary is center-dotted with a small paper reinforcer, and its position looked OK to me, contrary to what some buyers have reported in the past. I didn't remove the primary cell to check the mirror restraining clips to make sure they are not too tight—another problem some buyers have reported—but the star test didn't reveal signs of that, so they are apparently OK.

Once my Z was together and collimated, Dorothy and I spent a little while admiring her. Again, the big deal was how much a little money gets you these days. I had quite a pile of STUFF—eyepieces, mirror cooling fan battery holder, laser collimator, Moon filter—on the table next to the Z10. However, the only true test of a Dob is under the stars, naturally. Amazingly it appeared I’d get first light on this first night. The storms that have been plaguing us had abated. Sometimes I do get lucky.

And lucky I was on this night. The new telescope mostly cooperated. I always expect a commissioning period, a time of getting the kinks out of a new instrument. Usually, my first experience with a new scope is more frustrating than exhilarating. There didn't seem to be too many kinks to get out of the Z10, however. For the most part, it just worked.

There wasn't that much eye candy on display thanks to a large and gibbous Moon, but Jupiter was a spectacle, with the Great Red Spot sharp and clear. Luna was also beautiful as she always is. I scanned around a little for some DSOs, but the mosquitoes were terribly fierce after the rain and the lack of a zero power finder meant I didn't turn up much. Still, I've had more aggravating first lights for far more expensive telescopes.

How about a star test? The seeing sucked despite high humidity, but from what I could tell on Arcturus, the optics are fine and my rather casual approach to collimation was sufficient. Jupiter was probably a better test, anyway. I've observed the King enough over the years to know how he should look in a good 10 - 12-inch scope, and when the seeing settled once in a while, man did he look good. Mucho detail. I also took a gander at  Venus, who was her usual mysterious veiled self, but sharp nevertheless.

There will always be a few problems at first light for any telescope. The Z10's focuser is fine, but my Ethoses wouldn't come to focus without the 1.25-inch adapter that came with the scope. There just wasn't quite enough out travel. A couple of other 2-inch eyepieces were on the hairy edge, too. Not unusual for a store-bought Newtonian, but a little trying. I hate having to pull an eyepiece out for it to focus. I will collimate again this morning, pulling the primary as far back as possible. If the 13 and 8 Es still won't come to focus without the adapter,  I'll buy a 2-inch extension tube for the focuser, I reckon.  Otherwise, the focuser's action and the 2-speed feature worked well. This is a long way from the Chinese rack and pinion focusers of yore, y'all.

I was happy with the azimuth motion once I cranked down the knob on he pivot bolt. Some of you would still think it is too easy, however. I was more impressed by the azimuth setup. With the knobs on both bearings tightened down, any eyepiece I tried balanced with the scope. This is much better than springs or beanbags or welding magnets, folks.

Biggest impediment on this evening, however was the  lack of an easy to use finder. I've got a Rigel Quickfinder mounting base on order. A 50mm finder, even a RACI finder, is difficult for me to use, heavy moonlight or not. I need that zero power reticle floating before the stars I can see with my naked eye, not the confusing groups of suns revealed in an optical finder. Most of you will likewise want a Telrad or Quickfinder base. One more mosquito bite and I'd had enough, covering the Z with one of my Desert Storm covers and heading for the Den, where I turned on Netflix and ended my evening in appropriate fashion with Season One of the History Channel's Universe.

It was a good experience rather than a stressful one, as beginning to use a new telescope sometimes (or maybe often) is. Thank you Dorothy for not telling me I was crazy for wanting another Dobsonian. Rarely has a new telescope been easier to get going than the Z10, who has yet to tell me her name, but I am sure eventually will. Stay tuned.



Comments:
I agree Rod that a 10" is a sweet spot - not too big, not too small. Globulars really come alive at that aperture. The best view I have had of M31 has been with a 10".....Dwight
 
Excellent article, Rod. I have a GSO 8" here in New Zealand, as you say they are a lot of 'scope for the money!
 
Hey Uncle Rod,
I have a 2" University Optics 20 mm eyepiece I use with my Meade 12" Light bridge. I found that a 2" PVC coupling worked great as a spacer.

Dewey Barker
 
Rod, I have had my Z10 for about 3 years now. I decided on it for mainy of the same reasons you listed here. It has made a nice companion to my C8 on those times when I just want to observe without all the tech hassles. Enjoy.
 
It would be interesting to hear your views on the 10" GSO versus your C8. I had both at one point and chose the C8 over the 10" due to portability, and also how close the 8" was in brightness and resolution to the 10".
 
Thank you for this timely and informative post. I am trying to make a decision on my first telescope purchase; the only scope I've used is my inherited ETX-90 that I've had for nearly 15 years. From what's available right now, the Zhumell Dobs seem like a no-brainer from a value proposition. The main decision now is 8" or 10". Cost is swaying me towards the 8", but aperture fever compels me towards the 10". And I am trying to convince myself that the larger dob would not be an issue considering I'm in my 30's, healthy, and have only a few steps to contend with to get the scope to my backyard. But my only telescope experience being with the light and portable ETX makes me nervous about the larger instrument. I'm also keeping my eyes peeled on the second hand market since I have a tight budget to work with, but I'm the kind of person who prefers to buy new so I know how my stuff has been treated during its lifetime. But buying new probably means that I'm stuck with the supplied accessories for a while, in addition to the 8mm TV plossl and 1.25" ES focal extender that I have for my ETX-90. I would really appreciate any advice you might have to offer. -Ryan
 
Hi. what are the dimensions for the two boxes it came in? Thanks.
 
The boxes have long since gone to the curb. The long box with the OTA inside was slightly longer than the tube itself...maybe about 57-inches or so. You may be able to get an idea from the video...
 
Ryan, if you can afford it and move it about you may as well get the 10".

One thing, I have not taken mine on any road trips yet. It is going to be close fitting it into either my MarkVIII or my Aurora. If it doesn't fit I'll have to use the wife's van!
 
I got mine second-hand. After a few years the stock primary support springs go soft, so it's either: 1) keep the lock screws snug, or 2) replace the springs.

Other than that, this scope has been a GREAT performer.
 
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