Zhumell Z8 Deluxe Dobsonian Reflector Telescope

Zhumell Z8 Telescope + a 3mm Eyepiece

Sorry in advance for being so long-winded, but I appreciated all the reviews here while researching and wanted return the favor.

First off: I'm a beginner. I had an astronomy cla...Read complete review

Sorry in advance for being so long-winded, but I appreciated all the reviews here while researching and wanted return the favor.

First off: I'm a beginner. I had an astronomy class in high school where we learned to 'star hop' using charts-although most of the classes took place indoors in our school's planetarium. I have a few other telescopes and one of my degrees is in Fine Art Photography so I have some background in optics, digital imaging and darkroom experience.

I use the "afocal astrophotography" method: which is a fancy term for just holding (or mounting) a camera right up to the eyepieces. For my equatorial mount 4.5" Meade reflector I built a camera mount and shutter trip-wire out of scrap wood and photographed Jupiter, Mars, the phases of Venus, our Moon and Sun. I would eventually like to get another scope with a motorized-mount and tracking for proper astrophotography; but I've only recently finished grad school and my part-time librarian's salary isn't going to allow that just yet.

WHY NOT THE 10 or 12?
I didn't like the fact that to get the most out of the 10" and 12" models which were less than f/5 focal ratio I would, according to many reviews online, "benefit greatly" by buying a parracor to reduce coma. Many of the positive reviews were from first-time telescope users, but the few experienced users tended to mention the spherical aberration and coma one would experience in the faster scopes.

I got nervous as I read that up to 30% of the outer area of the included low-power eyepiece would be greatly affected by distortion without correction via a parracor. Without a parracor stars would 'look like seagulls' and watching the Moon move through the eyepiece would look like it was going through a funhouse mirror at the edges. Unfortunately as many of you probably know, a Televue parracor/coma corrector would cost almost as much as the telescope I would be correcting.

Since I enjoy planetary viewing and have a feeling I'd be bothered with noticeable edge coma/distortion I figured I go with the biggest focal ratio available, which was f/5.9 in the 8". Yes, I know, aperture rules—but the 8" would certainly bring in more light than my 4.5" for nebulae, and for planets that would be more than enough of an upgrade to keep me happy.

Also, at 8" the Dawes Resolution of this telescope would theoretically be 0.57arc seconds—and I've read that with normal atmospheric conditions 0.50 is about as good as it gets; so in my light polluted (5 minutes from Detroit) erratic Michigan-weather I'm willing to give up that 7-hundredths-of-an-arc second.

ORDERING
I ordered around 2PM on a Tuesday. I also ordered a Zhumell 3mm Z Planetary eyepiece for an insane 400x magnification with this scope. I planned to buy a 4mm eyepiece that cost over twice as much; but I knew I'd still want to try the 3mm for fun—so I just went straight to the 3mm, and if it worked out well I might not bother with the 4mm.

I immediately received a confirmation email with a tracking link, which also stated it should arrive in two days: Thursday. At 6:51am the very next morning I received another email indicating that everything had been handed over to FedEx for shipment. In less than 48 hours I had the scope in my home and assembled!

THE BOXES
The telescope comes in two boxes. The first box has the OTA (Optical Tube Assembly) that has the mirror and fan installed; plus a ton of boxes and baggies with parts. Open it carefully because you'll need to use it as a work bench (see below) and storage unit. The second box is the flat-packed Dobsonian base, and a few more baggies of parts.

Take the front cover off the telescope and look down at the mirror: is it shattered? Mine was perfectly fine. Joy! Going from a 4.5" to an 8" telescope was quite a shock. Unpacking the main bearings was a surprise to: heavy, machined metal disks about the size of a softball! Lots of big, beefy metal parts overall.

ASSEMBLY
The manual is available as a 36 page PDF download only. That ticks some people off immensely—I on the other hand don't mind. If you need to, you may print off a copy before the scope arrives. It's on the page where the telescope is offered for sale, near the top: go to the 'Details and Dimensions" tab and scroll all the way down, there is a large title heading 'Documentation' and the link is there. The manual is slightly outdated in some spots, on page 6 where it says it doesn't come with a collimator—don't worry, it does.

First: LOOSEN all the screws/clips on the primary mirror. GSO scopes are all notorious for shipping with mirror clips that are tightened too much, mine was no different. The knobs were so tight I was afraid I'd need a wrench to loosen them. This is probably a safety measure so the mirror doesn't rattle around during shipping, loosen them anyway: it's possible to collimate the scope by further tightening—but I think you'd be warping the mirror instead of tilting it, and risking cracking it.

There are 6 foam blocks (really 3 that are split in half) in the OTA (Optical Tube Assembly) box to hold the big tube. If you take the top ones off, remove the tube and then put those blocks on top of their counterparts—only facing upward you'll have a nice 'work bench' to do the other things you need to do to the tube for assembly.
You'll also want to keep the big tube box and foam block work bench, because every time you move this telescope you need to take the tube off the mount and set it down somewhere (the box is great for that). Also, because the mirror knobs stick out at the bottom of the tube do not set the tube on the floor on end: you'll mess up the collimation and if you do it hard enough possibly break your mirror. I have to admit though: Saturn was behind a tree and I did lift the entire telescope, tube in mount, all at once and carried it about 10 feet. Dangerous and foolish—especially in the dark.

ISSUES/ERRORS IN THE MANUAL (PDF)
Have a knife (lots of boxes, bags, tape) and an medium Phillips head screwdriver ready.

Page 10, Step 1: it never says which screws to use throughout most of the manual. To put the handle on use the only 2 silver, little Allen Screws.

Page 10, Step 3: use the big black Allen Screws.

Page 11, Step 5: The disk with the brass center hole, they say use the side w/brass showing to put the feet on. Well, both sides have brass showing, but they mean put the feet on the side of the bass with the hexagon-hole of brass showing (more brass than other side).

Page 11, Step 6: When they say use the plate with 6 holes, they mean the one with 4 big holes around edge.

Page 12, Step 12: Use 4 long black Allen Screws, not 6.

Page 14: When you put the big bearings/knobs into the side of the tube, try putting them in the center. Each slot has numbered gradations; if you center it to '0' on each side then the telescope is almost perfectly balanced. If you have it all the way down—then the tube (standing straight up in the mount) is too 'tall' and thus top-heavy. It will want to crash front to the ground, just adjust beforehand you'll be a lot closer to balance.

Page 15: Step 2: When you put the tube in—don't let go until you tighten the big knob on either side, or else the whole thing will smash to the floor or forward.

No mention is made of the fan: it's at the bottom, exterior of the tube. If you put 8AA batteries into the battery pack you can plug it into the bottom of the tube. This will cool the mirror faster.

I chose to leave the eyepiece bracket off. It's really heavy steel. It's also basically a thin piece of metal and could cut into car upholstery (and your kneecap if you're not careful). It also would clunk into doorways. Just a personal choice. I may add it back on later—there's easy access so you don't have to decide right away.

COLLIMATION
Included is a laser collimator, which is a huge help. Collimation is the aligning of both mirrors to each other and to the eyepiece/drawtube. It should be done on virtually all Newtonian reflector telescopes. Although I can collimate just fine without a laser on my smaller scope—I can do so because its shorter tube allows me to stare into the eyepiece while making adjustments with a screwdriver. Once you have to run to the front and rear of a larger telescope to make adjustments, and then walk back to the eyepiece you quickly discover that a laser collimator is a real benefit.

Collimating with the included laser:
1) Pop the laser into the eyepiece holder/drawtube;
2) Adjust the front (secondary) mirror so the laser hits the center dot on the rear (primary) mirror;
3) Adjust the rear (primary) mirror until the laser dot hits the target on the actual collimator.

About 25 seconds and you're dead-on collimated: laser goes in eyepiece holder, bounces around mirrors, and comes back out eyepiece holder. NOTES: the small screws you adjust on the little front (secondary) mirror: make sure not to loosen the center screw—that keeps the mirror from falling into the tube, it's supposed to be tight. Leave it alone. Also, have the scope pointed level with the ground when you do this, so in case you drop the screwdriver it won't roll down the inside of the tube and smash the main mirror at the bottom. You loosen the white locking knobs a lot, then adjust with the black knobs until the laser goes into the target on the collimator. Then you lock the white knobs down, which may skew the laser a little, causing you to fiddle with all the knobs. It's simple though.

If this is your first telescope, you might not realize there are finer points of collimating: name, The Star Test, where you blur focus on a bright star and examine the rings produced—hopefully they're concentric (sharing a center point—like the perfectly spaced rings around the bull's-eye on a dartboard).

FOCUSER & EYEPIECES
The focuser (with the 1.25" adapter in) has five identical silver knobs! One locks the focuser—make sure it's loosened, the other seems to make it totally disengaged from the gears—make sure that one is tightened. So if you're turning the focusing knobs and it's not moving, try loosening and/or tightening these knobs. The other two lock the adapter into the focuser, and then another locks the eyepiece into the adapter.

A little trick: align the eyepiece locking knob at a diagonal to all the others; that way you can find it easily in the dark among all its identical friends.

The closer something is (the Moon versus Pluto) the farther out you have to rack-out the eyepiece holder/focuser. The provided 30mm eyepiece is great, but if you seat it all the way into the holder (like a normal person) than it doesn't have enough back-focus to focus on the Moon. Rack all the way out towards your face, then loosen the eyepiece locking know and pull the 30mm eyepiece out a little (about 2mm) and re-lock it. You can see it focus right away. No big deal, works great with that trick.

I suppose you could put a huge, thin washer or thin rubber band around the base of the 30mm eyepiece to compensate, but the trick works easily enough.

You only need to do this with the Moon, everything else is far enough away that you don't have to rack-out the focuser that far. It's a great eyepiece, I was able to see the 'Earth-Shine' lighting up the 'dark' Moon, in addition to about a half-a-Moon normally lit up.

The provided 'Moon Filter' turns the Moon green and dims it a little. It screws onto the end of the eyepieces that you stick into the telescope (not the part you put your eye against).

The 9mm eyepiece is great and sharp and I didn't see any coma/distortion while looking at a half-Moon. I was very happy. Nice contrast. Venus was painfully bright at about half-phase. Nice!

I also purchased a Zhumell 3MM Z Planetary eyepiece, which gives an insane 400x with this scope. I was surprised how nice it was. Yes, it's not as sharp as the other two—and it's way dimmer; but looking at Saturn proved that it was bright enough; in fact it was a little washed out it was so bright, so I'll be buying a color filter for it. It actually was FANTASTIC and highly recommended—it's also about half the price of a 4MM (which would give a more sensible 300x magnification).

FINDER ALIGNMENT & HOW TO FOCUS THE FINDER VIEW
The finder doesn't have 3 to 6 alignment knobs like many finders: only 2 and a spring. The setup is very nice and makes it super easy to fine tune the alignment in the dark. If the main telescope has a star centered just twiddle the two knobs to make it dead-center.

Getting the finder in focus: this was the only really confusing thing about the telescope. What I mean here is when you look through the finder to aim, you don't want the star or Moon or planet to be blurry. Towards the front (that you aim at the sky) is a knurled ring. Turn that ring so it travels back towards the rear (where you stick your eye). Turn it a lot so it travels far back. This then frees the big front part so you can turn it and focus. Look at Moon/Star when you do this. Once you have a good focus; turn the knurled ring back the other way so it travels toward the front and locks against the big front lens thing you just turned to focus. No diagram of it in the manual and not easy to figure out what they wanted you to do—but that's it.

THE ONLY THING I HATE
Other than the fact that I should have bought sooner, the only thing I don't like is that it's actually pretty short. I had a back ache after hunching down (and I'm only 5'8" !!!!) looking at Saturn low on the horizon, but not that low. My Meade 114 equatorial at its lowest on the tripod never hurt my back. So, you might want to bring a lawn-chair to your viewing sessions. All-in-all I'm shocked at how happy I am with this scope.

Also, do yourself a favor and download the free Stellarium dot Org software—it's awesome. And since June 5/6, 2012 Venus will pass in front of the Sun, maybe pick up some cheap Baader Solar film and watch, it's good for looking at sunspots too.

Of course there's an equation that telescope owners should know: T x E = R; The Time (T) you put into researching a telescope multiplied by the how Excited (E) you are about using it equals the days of Rain (R) you will have once it arrives on your doorstep.

So I'm out of commission for the next few days because of rain. I focused mainly on planets and the Moon when briefly testing out the scope—but I did see a lot of stars I didn't recognize: the light-grasp of the scope is amazing, you can point to an area of sky that's 'empty' visually (or through a 4.5" scope) and see tons of stars you couldn't before.

Cheers and clear skies to you,
Mike from Detroit