24 replies to this topic

[Olivier Biot]

Zhumell Z10 10" Dobsonian Review

By Cathy James.

[Bonco]

I thought Cathy did an excellent review of the Z10. I certainly agree that a Cheshire is the way to go for collimation on any Newtonian. For me the finder works perfectly and is easy to use so I've not purchased a Telrad. My short review is this: For the price the Z10 is one of the best bargains out there. The quality of the OTA componets is excellent. The mirror, cell, spider, diagonal, and focuser are functional and well made. The optical performance on mine is excellent and exceeded my expectations. The mount is simplicity at its best and while not sophisticated it is adequate. The 9mm eyepiece that came with it has become one of my favorites and used in my other scopes. The 30mm is good for low power views and is about what I'd expect for the package price...It's ok but not great mainly due to curvature toward the edge of view. Everytime I use my Z10 I'm amazed at what it delivers for such a low price. Bill

[Jon Isaacs]

Cathy:

Well done, I thought it was a good review and accurately characterized the Z-10, I have had a 10 inch GSO Dob for 8 or 9 years and every time I use it I am quite pleased with its performance.

It's a nice balance between size and manageability. I think you hit the nail on the head about the size difference between the 10 inch and the 12 inch...

Good job.

Jon

[RocketScientist]

Thanks. I appreciate the compliments on the review. Now if all this winter humidity would just clear away...

Cathy

[David E]

Cathy, nice review! It looks like you have had to tweak things here and there, but I think you'll have a scope you can enjoy for many years to come. The balance adjustment looks interesting, but I think I would agree with you that it is not very practical. It would be better IMHO to design the scope with a fixed balance point and the user can use magnets or other items to help with unruly balance problems.

[Mike B]

Hi Cathy-

At the end of your review you stated:

Readers of this review may feel that I've been unduly negative.

Maybe because i'm more that "old hand" you'd mentioned earlier, i didn't find the review to be negative at all... seems to me the primary glitch in the whole deal was the lack of clear instructions. If the PDF info you linked covers issues re: scope assembly, the 1-1/4" adapter, collimation, focuser adjustments, etc. then all should be well- even for most "beginners".

Overall it seemed to me your review was very frank & straight-forward, and as such was a good PSA (public service announcement) to the Dob-buying community.

And congrats on your recent move- you've managed to land in a very beautiful area of the state! Are there darker skies east of you, out 580 & up Altamont? Where do the local astro-types & clubs go to view, locally?
mike b

[dwright]

Very nice review; clearly written.

Re: Zhumell vendors, there is currently at least one other: Great Red Spot Astronomy Products.

[Ed D]

Cathy, I enjoyed reading your review of the Z10 very much. It is very well written and provides the type of information prospective buyers are looking for. Reading your article makes me want to pick up the phone and order one.

Ed D

[RocketScientist]

Hi Cathy-

At the end of your review you stated:

Readers of this review may feel that I've been unduly negative.

Maybe because i'm more that "old hand" you'd mentioned earlier, i didn't find the review to be negative at all... seems to me the primary glitch in the whole deal was the lack of clear instructions.
Overall it seemed to me your review was very frank & straight-forward, and as such was a good PSA (public service announcement) to the Dob-buying community.

Thank you. I suppose I've read too many reviews that are unduly positive. I suspect that these types of reviews tend to come from less-experienced observers. It's great to see that they are happy with their scopes, but a review that isn't constructively critical may not be of much real value to prospective buyers.

Key issues with my Z10 fall into 3 areas:

-- Lack of included directions or pointer to same
-- Adjustable OTA/axis connection is not well thought-out
-- Secondary mirror was incredibly far out of adjustment as shipped

And congrats on your recent move- you've managed to land in a very beautiful area of the state! Are there darker skies east of you, out 580 & up Altamont? Where do the local astro-types & clubs go to view, locally?
mike b

Yes, skies get darker quickly once you pass Livermore heading east. My local club has a dark sky site somewhere southeast, in the hills east of Lick Observatory, which is not far away (and which I visited recently, albeit in the daytime). I haven't been there yet because the winter wet season is not a great time to go up secondary roads or to fight the high humidity. (I managed to forget to put the dew shield on my SCT a few nights ago, and it ended up looking like the whole OTA had been dipped into a pond.)

[Darron Spohn]

Cathy,

Your review pretty much tracks with my experience. I had a Zhumell 10-inch for a while, and recently sold it in favor of a Teeter 8-inch solid tube Dob. The Zhumell is a decent telescope, especially for the money, but that altitude bearing adjustment "feature" is a real head scratcher. I'd bet the price of a cheap Plossl the person who designed that never tested it in the field.

Another thing that annoyed me about the Zhumell was the time it took to settle after focusing, especially when pointed at objects 30 degrees above the horizon, which includes the planets at my location. I guess I'm spoiled by my friends' Dobs that are rock solid and do not vibrate when focusing.

Other than that, the optics in the Zhumell at fairly good. Even with perfect collimation I found the images getting soft at 250x on nights when the premium Dobs could go to 350x.

But the Zhumell is easy to use, holds collimation well, and the price is certainly unbeatable. Just don't expect too much. You're paying for an economy telescope, not a premium model. Enjoy what it does and go peek through the more expensive telescopes when you get hungry for high-power views.

[Bonco]

Still have my Z10 and expect to keep it forever. Mine is the older model without alt bearing adjustment. Despite its very low price and its basic mount I've successfully used it with a 4mm Nagler and 2X barlow for magnifications of approx 600X for double star observations. Really busts up Porrima. I've owned massive old style equitorials that weren't up to that task. The Z10 is certainly a basic Dob but one that continues to surprise me with its abilities.
Bill

[seisner01]

I had to laugh when I read Cathy's debacle with the 1.25" adapter being seated incorrectly in that I did the exact same thing, reacted in the exact same way and created/fixed the problem in the same manner (my Cheshire).


I went with the package which included a 100deg FOV 16mm eyepiece. It's no TeleVue, but definitely workable. It also included a TelRad. Initially, with the spotter & the TelRad, I experienced some balance and settling problems, but you do have the ability to adjust the center of gravity and I eventually got it working pretty well.

Love the Telrad! I aligned the spotter, the TelRad and the scope using a 12.5mm reticle to a very exact degree. Using the Telrad in conjunction with the spotter, I have relatively little work to find things in the main scope.

All in all, I believe it's one of the top 3 or 4 bargains currently available in the middle-end "bang-for-the-buck" category for astronomers on a budget.

[Waxing Gibbous]

Cathy,
Thanks for a really good review. Your experience dovetails pretty well with mine - especially the base 'problems'.
I also found that neither the ALt nor Az bearings could be sufficiently tightened to hold the scope steady in a 5kt wind. I wound up selling it for this reason.
Fortunately these scopes are optically very good and easy to modify. The first thing I did was swap the focuser for a Moonlite. Nothing else will make as big a difference as this. Well, you could trade-in a Zambutto primay I suppose, but you get the idea. The Moonlite fit perfectly and was much easier to use.

I found the springs and knobs on my primary to be perfectly adequate, but did replace the secondary adjusters with Bob's Knob's. Thay share the same supports (and optics)with Meade's Lightbridges so simply getting the correct size is all that's needed.

Thanks again articulating the so well the pros and cons of this scope.
CS
Peter

[RocketScientist]

Cathy,
I also found that neither the Alt nor Az bearings could be sufficiently tightened to hold the scope steady in a 5kt wind.
Peter

I've since found this out myself. I tighten down the altitude bearing as much as I can, given that they are round knobs that don't allow any finger leverage, but there really isn't enough friction to hold the OTA at a given elevation.

At some point, I'm going to have to work out a modification that lets me add additional altitude-bearing friction. I haven't had any problems with the azimuth yet.

Cathy

[Jim Rosenstock]

Just wanted to pile on....excellent review!

Z10s have a big fan base here on CN....and lots of threads on "home improvement" of these scopes, as well.

That kinds says it all....excellent value, but best for an amateur with a litle bit of prior experience, or at least the tinkering gene...

The less-adventurous newbie might be better off buying through businesses like Astronomics, Orion, OPT, that tend to have better tech support and product quality control.

Again, geat review, and right on the mney!

Jim

[akadros]

This was an excellent review. I recently purchased the Z8 and I was scared because of all the reviews had talked about the lack of instructions. Before I got my scope, however, not only did I find the pdf you referred to, but I had also found the following video: http://www.youtube.c.../0/VVBRDCS_qsI. I was a complete newb when putting the scope together but the video made it a cinch.

[tinrinnie]

Really appreciated your review. I've always wanted to get a dob, but collimation intimidates me. After reading your review, I see it is not trivial for the newbie but it is do-able. Reading the good, the bad, and the ugly helped me take the plunge and order a Z10 myself. Can hardly wait.

[cpsTN]

They also make the Aperture 10" f/5 version and it is even less $$$, about $450 including shiping in most places. opticsmart.com.

[spaceydee]

Tinrinnie, I'm glad you didn't let the worry of collimation keep you from ordering a dob. You'll get used to it fast

[Seattle Brian]

I've got the old Z10 with the springs, which KILLS my hands when I try to assemble and disassemble the telescope. I'm glad they have done away with those.

[RocketScientist]

tinrinnie,

So tell us about your experiences with your Z10! How is it working out for you?

Cathy

[Angie]

I just found this thread, and the superb review by Cathy James of the Z10....
Hi Cathy,
I just happened across your excellent 1/19/11 review of your Z10. Wow, having bought the identical telescope last summer in 2012 (under the name Apertura,and called the A10),
every word of your review reflects my own experiences exactly.
Thanks for writing it.
I had the same sinking feeling you describe so well when looking through a Cheshire! What a mess of non-concentric confusion. No one in the local astronomy club could figure it out either, and these guys are all into telescope making and optics. I gave up trying to sort it out, concluding that the secondary may not be set precisely in the center of the tube, or maybe it is not in a precise 90 degree relationship to the axis of the focuser. I wasn't sure if the focuser was even set at a 90 degree angle to the tube's geometric axis. Then I thought, well maybe the geometric axis is different from the optical axis of the primary...which would make the problem even more complicated.
My brain shorted out at that point, and I just did the 'collimation' with the laser included with the scope, according to the simplistic instructions included in the very sketchy user's manual, and some comments made by the people who sold me the telescope when I called them for help.
Now, despite this ongoing nonconcentricity of the profiles of the mirrors as seen through the Cheshire, when I just collimate with the simple red dot procedure, and get it really precise, the telescope performs quite well optically, at least on axis, though I wonder if it could be even better if the job were done 'right' by eliminating subtle angular distortions in the mechanical alignments of the telescope tube that must surely result in off-axis optical distortions of the light cone, such that while the red dot might well be lined up, the surrounding light cones are somewhat askew, leading to coma, astigmatism etc just beyond the center of the FOV. As an anecdotal example, last winter I could see the E and F stars in the Trapezium on nights when other, bigger and more expensive telescopes failed. That seems so unlikely if the wonky alignments of the tube components really impact performance significantly, don't you think?
So I'm wondering if you have learned any more about this issue of collimation, how important is it, and why does the Cheshire differ from the laser collimator and which one should we believe.
Thanks...and clear skies to you
Angie
Santa Barbara

[AstroTatDad]

I just found this thread, and the superb review by Cathy James of the Z10....
Hi Cathy,
I just happened across your excellent 1/19/11 review of your Z10. Wow, having bought the identical telescope last summer in 2012 (under the name Apertura,and called the A10),
every word of your review reflects my own experiences exactly.
Thanks for writing it.
I had the same sinking feeling you describe so well when looking through a Cheshire! What a mess of non-concentric confusion. No one in the local astronomy club could figure it out either, and these guys are all into telescope making and optics. I gave up trying to sort it out, concluding that the secondary may not be set precisely in the center of the tube, or maybe it is not in a precise 90 degree relationship to the axis of the focuser. I wasn't sure if the focuser was even set at a 90 degree angle to the tube's geometric axis. Then I thought, well maybe the geometric axis is different from the optical axis of the primary...which would make the problem even more complicated.
My brain shorted out at that point, and I just did the 'collimation' with the laser included with the scope, according to the simplistic instructions included in the very sketchy user's manual, and some comments made by the people who sold me the telescope when I called them for help.
Now, despite this ongoing nonconcentricity of the profiles of the mirrors as seen through the Cheshire, when I just collimate with the simple red dot procedure, and get it really precise, the telescope performs quite well optically, at least on axis, though I wonder if it could be even better if the job were done 'right' by eliminating subtle angular distortions in the mechanical alignments of the telescope tube that must surely result in off-axis optical distortions of the light cone, such that while the red dot might well be lined up, the surrounding light cones are somewhat askew, leading to coma, astigmatism etc just beyond the center of the FOV. As an anecdotal example, last winter I could see the E and F stars in the Trapezium on nights when other, bigger and more expensive telescopes failed. That seems so unlikely if the wonky alignments of the tube components really impact performance significantly, don't you think?
So I'm wondering if you have learned any more about this issue of collimation, how important is it, and why does the Cheshire differ from the laser collimator and which one should we believe.
Thanks...and clear skies to you
Angie
Santa Barbara

Hi Angie,
I have the Z8 and like it very much, I have been using the "laser/collimater" that came supplied with the Z8. I haven't upgraded yet, it seems to do the job for me. I did collimate the laser and that helped out a lot, also upgrading to stiffer springs on the primary mirror was another plus.

If a Z12 or AD12 would fit in my car I would definitely get one of them.

Clear Skies.

[Mainuh]

Thanks. I appreciate the compliments on the review. Now if all this winter humidity would just clear away...

Cathy

Hi Cathy,

 

Very nice review. Near the end you hinted at "come back in a year" for an update.  Did you ever post an update? I'm looking at selling my Williams Optics Z73 and just going visual with the Z10.

 

Thanks!

Don

[RocketScientist]

I never wrote an update, but I still have and use the Z10. It continues to be my largest light bucket, and complements the other 3 lighter scopes used for other purposes.

I would still recommend it.