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Review of XT10 with Zambuto Mirror

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#1 JayinUT


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Posted 15 May 2011 - 11:28 PM

This is my review of my XT10 using a 10 inch re-figured(?) Zambuto mirror. Please see this thread for details:

Zambuto Mirror Thread


I was at home, and everyone was gone to activities or such and so I plugged down to Cloudy Nights and began reading in the reflecting forum. I had been reading about how Carl Zambuto was offering replacement mirrors for Chinese made dobs, mainly the Orion series of scopes. That got my interest because I have an Orion XT10 along with an Orion XX14i and a 20” Obsession that was purchased used.
I followed this thread for a several days and then watched as Carl himself signed on and offered to send out a test mirror for people to try and that it would be a ten inch mirror. Well, I had followed the thread, but life had gotten in the way between work, family and other obligations. I thought about putting my name on the list for viewing the 10 inch mirror and putting it in the XT10. Then I noticed that there were four or five people ahead of me and I thought I had better rethink it as it may be fall before I see it.

Carl then mentioned that Steve Dodds of Nova Optical was doing the coating and Steve lives only ten minutes from the house so a thought occurred to me. Why not offer to test it out this weekend and then send it to Phil on Monday, who is first on the list. I posted that, and Carl agreed it was a good ideal as long as everyone on the list in front of me agreed. Graciously they did so I picked up the mirror on Wednesday, May 11th, 2011 from Steve at his shop. Now the weather had better cooperate, though the forecast was for beautiful weather.

NOTE: I sketch and I do not claim to be a terrific sketcher or to capture everything perfectly. Errors are mine and mine alone in terms of star placement or any other error. I use them as a visual reminder of my experience. All sketches here are not corrected except for the background. I used GIMP and the curves feature to try and capture what I was seeing in terms of the background. Everything else remains as sketched.

When referring to the XT10 in this article, I mean the XT10 with the Zambuto ten-inch mirror in it.


On Thursday, May 12th, 2011, I have to admit that I anxiously waited the last bell of school in order to get down with my work obligations and to exit. By 4:00p.m. I was completed my teaching duties and was out the door on the way home. At 5:00p.m. I had the XT10 tube out, and was undoing the base screws. I have to say, that I had replaced the Orion stock screws about two years ago because I found they stripped far to easily. I put in steel screws instead that work much better. Anyway, the mirror cell came out quick enough, and it was on to the clip screws. There are two screws in the clips and you have to remove them to get the mirror out. Watch out for flaking of the black paint as you take the screws out. Not a major issue though, just thought I would just point that out.

The XT10 stock mirror came out easily enough and then I opened up the box that hold the 10inch Zambuto mirror. The mirror has a cover and it is held in place by blue painters tape to protect the mirror. To remove it simply undo the tape carefully and then the top will just lift right off. Installing the Zambuto 10 inch mirror was a breeze and within ten minutes the scope was back together and ready to go.

I used my backyard for this task since the moon was a nice 66% plus waxing gibbous moon and I figured a dark site wasn’t going to help in those conditions. Plus there is that thing called work the next day and using the backyard this night meant more time viewing at the scope with the mirror.

The Scopes: Night 1

Orion XT10
Zambuto 10 inch mirror (refigured)
9x50 RACI Finder; Telrad:
Stock Focuser;

Orion XX14i
9x50 RACI Finder; Telrad; Shroud;

27mm TV Panoptic, 22mm Panoptic; 14mm, 10mm, 7mm Pentax XW; 6mm TV Radian;
Filter: Orion Ultrablock Filter , 13% Neutral Density Filter (for the moon);

Breakdown of Eyepiece magnification by Scope: See the attachment for this. Magnification and FOV were kept as close as possible.

May 12th, 2011
Location: Herriman, Utah
Time: 03:00 UT / 09:00p.m. MDT
Seeing: Antoniadi II
I used the XX14i first and used the 14mm Pentax XW. The images were sharp, clear and the seeing tonight was wonderful. It is the second day after a storm and in the fall, winter and spring in northern Utah that means very good to excellent conditions for seeing. Tonight, for the whole night, seeing conditions were excellent and transparency was very good. My friend and fellow observing companion Mat Hutchings was with me. Mat has made his own mirrors and dobs now for sometime having learned the craft from Jeff Baldwin over in the Stockton CA Astronomical Society.

Copernicus was wonderful, and I enjoyed viewing Reinhold and Lansberg as well. The craters showed a nice contrast between the light and shadows. I then went over to the XT10 with the Zambuto mirror and it was an interesting contrast. On my audio I did give the contrasts available on the Zambuto refurbished mirror a big wow. At this time Mat showed up and asked what I was doing. I told him to look in the XX14i and then in the XT10 and compare.
We both felt that XT10 with the Zambuto mirror had just wonderful contrast between the shades of white, gray and black. The rays from the ejecta from craters actually seemed to show a variation to their coloring and it was just terrific to see the black shadows transit through a grey to a white color. The XX14i performed quite well here but the edge definitely went to the Zambuto mirror.

Now that Mat was here we decided to do a star test using Regulas and a 6mm Radian. The star test shows, to quote Mat, “A phenomenal mirror with phenomenal smoothness.” Mat stated that the smoothness of the mirror is perhaps the best he has seen, and he has done an eight-inch and sixteen inch mirror that are just outstanding.

Messier 51 /NGC 5194& NGC 5195 Sketches

We next decided to let our eyes undo from the moon and waited for about twenty minutes. I did a sky hop on both scopes to go and check out Messier 51 in a very moon dominated sky. Here the XX14i showed a bright inner, some fuzziness around the core with some brightening toward NGC 5195. The XX14i was also not near as dark in its background contrast, but some of that would have to be accounted for from the increased aperture and the increase amount of sky glow from being in an LP area and especially with the moon being so bright. NGC 5195 showed a bright inner core with a hint of fuzziness around it and was relatively small.

Having said that, the XT10 had a very dark, a black background that allowed the galaxy to really stick out. There was definitely a hint of structure here that both Mat and I observed to the point we want to say that we could distinguish a spiral arm. NGC 5195 was much larger, the core brighter and the shape was easily distinguished. The XT10 here had the advantage I would state over the XX14i in the conditions and more importantly in the contrast. That contrast allowed more details to be viewed. Eyepieces used were the 14mm Pentax XW in the XX14i and the 10mm Pentax XW in the XT10, and the 10mm Pentax XW in the XX14i and the 7mm Pentax XW in the XT10.
In my sketches here, I attempted to show a darker sky with the XT10 versus the XX14i and the details that reveals. You can decide if they enhance or detract from my observation. I have tried to show the distinction in detail.

M51 XT10 Zambuto

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M51 XX14i (galaxy is brighter to show more of the fuzziness around the core)
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By now Hercules was well up in to the eastern sky, and the night was pretty steady. So we star hopped over to M13 to take a look. In the XX14i we used the 14mm Pentax XW and the 10mm Pentax XW (best views with the 10mm) and the XT10 used the 10mm Pentax XW and then the 7mm Pentax XW.
The XX14i showed a wonderful view of easily defined tendrils and stars showing up through the FOV. The contrast here was terrific and for being such a star light night, the globular looked reasonable. In the XT10 the background again was darker but it was harder for some reason to view as many stars as in the XX14i and the detail seen in the tendrils was not as much as in the XX14i. Here both Mat and I felt that the XX14i won. Perhaps aperture was deciding factor here.

Epsilion Lyra The Double Double No Sketch

We decided to take a look up in Lyra now since it had arisen and was well up in the night sky by 12:30a.m. MDT on May 13th, 2011. The star hope is easy using the Telrad on each scope and we used the 10mm Pentax XW on the XX14i, the 7mm Pentax XW on the XT10 and then for fun we used the 6mm Radian on each scope. Both scopes split the Double Double easily enough and did so nicely, but the XT10 with the Zambuto mirror had nice dark edge and the black in between the doubles was cleaner. Edge on this one to the XT10 with the Zambuto.

SATURN Sketch done not shred (I’m not a good planetary sketcher at all).
We now went to Saturn and took a gander at a planet. Saturn showed a wonderful view in both scopes. We used the 7mm Pentax XW on the XX14i and the 6mm Radian on the XT10. Both scopes showed the first northern band and one southern band. The Cassini division was visible as was the A and B ring. The XT10 performed wonderfully here but so did the XX14i. Perhaps fatigue was beginning to set in as we observed here for about an hour to capture as much detail as possible.

NGC 6207 Sketch

We now just took a break and had fun observing what we could under the moon. Around 3:00a.m. as the moon was setting behind the mountains to the west, and not a real issue anymore I went back to Hercules to NGC 6207 to push a mag. 11.7 galaxy in the conditions. This is an easy star hop, and hard to see in the conditions. To observe this took some averted vision and some breathing. Remember, I am observing at 5200 feet elevation. The XT10 brought the core of the galaxy in very bright and showed a hint of its elongated shape. The XX14i also brought out the core, but not as bright as the XT10 and though showing the elongation, it took experience to really bring it out. Here the contrast of the Zambuto mirror showed its wonders.

After this, Thursday/Friday nights observing was over. We broke down the scopes, took them inside and left them protected in their blue covers (I have an Orion bag for the XT10 so the tube stays in that when not in use).

FRIDAY MAY 13, 2011
Herriman, Utah
Antoniadi IV to III

XT10 with Zambuto Optics
ATM 8 inch Dob
ATM 8 inch Dob

Conditions tonight were not as good as Thursday night. Antoniadi IV to III (started as a IV and moved to a III). Clouds all around when we started not rain clouds, just clouds. Seems to be the story of this winter and spring. Let me state up front that Mat and I and a couple of others got some observing in but my 17 year old son came out (he uses the 10inch a lot) and so did my 18 year old daughter. She spent a lot time using the XX14i so lunar observing.

Tonight Mat brought over two eight inch scopes he built. The F3.6 (I believe) 8 inch he just finished a few months ago and coated by Steve Dodds has an excellent mirror on it. So we decided to use that and the XX14i to test tonight. My friend with a Z10 was sick unfortunately. We did a lot of moon observing and observing of Saturn for the first two hours as the clouds just came flying in. Clear Sky Clock stated that the clouds would go away around 11:00p.m. and they did.

I will state that my 17 year old son who has been observing for about 3 years now told me quite frankly after viewing the Moon and Saturn that “This mirror is much better than the one I had in there normally.” I asked why and he stated you can see more details. Leave it to a younger eye I guess.

Gamma Virginis

After the clouds cleared out we decided to go and split Porrima or Gamma Virginis. This is a tight split of around 1.7 seconds I believe right now and a good test. We used the 6mm Radian in the XT10 and the 7mm Pentax XW in the XX14i. Both scopes split the pair, but the XT10 again had a finer split and showed more of a gap in the split. This to me was due to the contrast again. We next compared the XT10 with the 8-inch that Mat had made. Again the Zambuto mirror in the XT10 won, but it was closer here. The 8-inch gave the 10-inch a run, but the smoothness and contrast here won out. The Zambuto mirror won out.

In the sketch the stars are farther apart because I wanted to show them as clearly split in the XT10:

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Split in the XX14i. This is closer to what both images looked like:

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NGC 3242 The Ghost of Jupiter Sketch

I wanted to observe a planetary nebula, one of my favorite objects to view and I knew that The Ghost of Jupiter was still up. So both the XX14i and the XT10 star hopped over to the Ghost, which was relatively easy. Without a filter the planetary stood out, even in the poor conditions. The XT10 showed perhaps a little more detail in the planetary but the color was better in the XX14i without the filter. Here there are parts that seem to favor the XT10, but the XX14i seemed to do quite well with this object.

The Ghost with the XT10

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The Ghost with the XX14i

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We observed a little more and did so for the enjoyment and let others have a go now that the weather had cleared. I spent some time with my two teens observing and going through the sky with them. Saturday the weather was just horrible until around 3:00a.m. and I was too tired to stay up that late.


So what is my conclusion after spending two nights with a XT10 with a Zambuto mirror? It was a wonderful experience. The biggest takeaway for me is the amount of contrast in the mirror. That contrast, allows an experience observer to see more detail and thus gleam more from their experience. No one will go wrong buying this mirror or one like it. Is it a momentous WOW? No, don't expect Hubble clarity or images, but I wouldn't regret owning one in my XT10 and will at some point soon. My only regret is I would have loved to have it for a dark sky trip down to Notch Peak (one of the darkest areas in the continental U.S.) for a two night observing trip there with no moon. I am really looking forward to what others have to say after using it and using it in dark skies, and I'm envious.

I want to thank Carl for the opportunity, Phil/City Kid for letting me go before him and the others on the list for the same. There were two others besides Mat and my son who used the mirror and they walked away basically wanting to see if they could convince their wives of parting with $800. I am not sure if this is what is wanted, and it is probably too long. Any errors are mine, feel free to correct me but I basically just tried to cover the observing experience of two nights in a nutshell.

#2 pstarr



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Posted 16 May 2011 - 07:56 AM

Great report Jay.

#3 94bamf



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Posted 16 May 2011 - 08:14 AM

Great report Jay! Sounds like Mr Zambuto is going to be even busier soon! It would be great if he did this for 14" mirrors too, but I don't imagine there is as much demand.


#4 UmaDog



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Posted 16 May 2011 - 08:19 AM

Thanks for the detailed report. It certainly sounds encouraging and the 10" obviously more than holds its own compared to the 14". I like the fact that you also try an 8", since I'd imagine the darker sky background in the 10" compared to the 14" is due to the former's smaller aperture.

#5 Vondragonnoggin


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Posted 16 May 2011 - 08:25 AM

Very nice report and very interesting that the 10" held it's own so well in comparison to something with a whopping 4 more inches of aperture. Too bad you didn't have another 10" to do a side by side. Hopefully someone will. Now the seed has been planted...

#6 pstarr



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Posted 16 May 2011 - 08:26 AM

I'd imagine the darker sky background in the 10" compared to the 14" is due to the former's smaller aperture.

I would say it's due to the better polish on the glass and therefore reduced scatter. Blacker backgroud is one thing you get with these mirrors and the reduced scatter is one reason the contrast is so good.

#7 cliff mygatt

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Posted 16 May 2011 - 08:41 AM

Great report and gets me itching to get our and test my XT12i with new Zambuto mirror but alas the Pacific Northwest is cursed with rain and clouds and it is my fault for such a big telescope purchase. Soon, the coulds will part and I will take mine for a spin.

#8 JayinUT


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Posted 16 May 2011 - 08:52 AM

Thanks everyone. To clarify and I believe it is in the post, I believe the 10 inch did better on contrast because of the difference in size and the smoothness of the mirror. However, both Mat and I, and a couple of others were very happy though with the performance of the XX14i and it really did quite well. It's a keeper and has a very good mirror in it. Ken, yep, if he did a 14 inch I would upgrade in a heartbeat as I enjoy my XX14i and his mirror would provide an wonderful view in it. I would love to have compared both at a dark site and to have compared the 10 with another XT10, XTi10 or a Z10. I have a friend with a Z12 but he never got back to me about coming over. He is not a big observer during large moon periods.

To conclude, my son's car broke down about a half hour after I got the mirror and that has eaten a hole in my savings that I have to replenish before I can buy a mirror from Carl. I will state that if that hadn't happen, the mirror would have been purchased and Phil would be getting a new mirror and not this one from Mr. Zambuto. It isn't huge, but it is enough for an experience observer to see a difference. I tried to post some more on this on my blog, but am having issues and I am late for work so I have to go. I'll fix the blog post later today.

#9 dvb


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Posted 16 May 2011 - 10:48 AM

Excellent report! It sounds like the secondary was up to the task of working with the ZOC primary, although one wonders whether a different 2* might also contribute to an improvement.

#10 Maverick199


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Posted 16 May 2011 - 11:20 AM

Excellent report and sketches Jay. Congratulations on your new Zambuto mirror.

If you don't mind me asking, what does that bit of contrast cost in terms of a normal XT10 mirror compared to Zambuto? Obviously in your case, money is not an issue but more to do with perfection and attaining the best views possible and I understand that. ( I sometimes buy a higher end component just to get 2-4 frames more for my comp ).

#11 mountain monk

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Posted 16 May 2011 - 11:21 AM

Thanks, Jay. Interesting report, as usual.

Dark skies.


#12 City Kid

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Posted 16 May 2011 - 03:39 PM

Great report, Jay. As I was reading it two thoughts came to mind. One, I can't wait to get this mirror in my scope and two, my report has to follow this? :lol: I can only hope my report is half as good as yours.

#13 Bowmoreman


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Posted 16 May 2011 - 09:31 PM

plus one, guys...

I mean, just how do I follow Jay's review... ???

Maybe my schtick will be my east coast orange zone skies?

That said, cannot wait to try it out... my XT10i is my default visual scope now for almost 4 years now, and it is my road trip one as well... so if I like it, it will likely take a place here...

Just hope I can get some skies...

#14 davidpitre



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Posted 16 May 2011 - 10:13 PM

That was a nice review. You put some effort into it, and did some interesting comparisons. Well done sketches.
A couple of thoughts:
The comparisons were interesting , but it was unclear if the comparisons of the two views were done at the same magnifications or exit pupils. It sounds like they were done at somewhat similar magnifications.

That M13 showed more stars and detail in the 14" is certainly no surprise. A mediocre 14" should show fainter stars than even a perfect 10".

Interesting and encouraging that the Zambuto 10" provided a better split of Porrima. Do you think the 14" was well cooled? It likely has close to 2x the mass of the Zambuto. A small quibble: You said the difference could be attributed to the better contrast of the Zambuto. I guess it might be more accurate to say the better figured Zambuto puts more energy into the airy disk rather than the diffraction rings. It is not really a matter of contrast between the stars and the background sky. The 14" was viewing at 235x vs 195x with the 10" . With not so good seeing this could make a difference.
I'm not trying to nit pick, just adding context to your data. Your observations were well done. Comparing two scopes of different apertures is difficult. Bravo.
We should keep in mind the variability of secondary mirrors. I received a relatively well figured sock primary mirror with my Orion 10". My secondary mirror was poor. Replacing it helped a lot.

#15 JayinUT


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Posted 16 May 2011 - 11:31 PM


Great points and context, it's appreciated.

The observations were done at similar magnifications and the exit pupil did differ, unless we used the same eyepiece in both scopes which we usually did also. I just focused my report on the magnification. I'll try to attach the info but here is the info. Hopefully it comes out ok.

Pentax XW in XT10 f4.7

7mm TFOV 0.410 degrees, Exit Pupil 1.489mm
10mm TFOV 0.586 degrees Exit Pupil 2.127mm

TV Radian 6mm TFOV 0.301 degrees Exit Pupil 1.276mm

XX14i f 4.6

Pentax XW
7mm TFOV 0.299 degrees Exit Pupil 1.521mm
10mm TFOV 0.427 degrees Exit Pupil 2.173mm
14mm TFOV 0.599 degrees Exit Pupil 3.043mm

TV Radian 6mm
TFOV 0.220 degrees Exit Pupil 1.304mm

Some comparisons:
When using the 10mm Pentax XW in the 14 in the report we used the 7mm. We then often used the same eyepiece to view also.

10mm Exit Pupil XX14i 2.173mm
7mm Exit Pupil XT10 1.489mm
10mm Exit Pupil XT10 2.127mm

With the numbers above someone can match them up. The 14 was well cooled that night. It sat out cooling with its fan from about 7:00p.m. until we started using it around 9:30p.m. Same with the XT10. Prior to that they were in a room with no heat. It is possible that the 14 hadn't cooled but we both felt that it was as the moon showed up very nicely.

Didn't take your post to nick pick. It pointed out some useful context and that is good. Thanks for the input.

The file is too big to upload so here is an image of the scan. It is in my photobucket account.

#16 UmaDog



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Posted 16 May 2011 - 11:34 PM

Carl has an extensive post on the other thread, in which he discusses the sky brightness (amongst other things).

#17 sabir


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Posted 17 May 2011 - 03:00 PM

Thanks Jay for the awesome report!!....very comprehensive and accompanied by great sketches! :waytogo:

I assume that when you stated - "10 inch re-figured(?) Zambuto mirror" - in your review, it was meant as a question?

These mirrors are actually not refigured mirrors. The stock mirrors received by ZOC as a trade in are precision annealed in-house. This makes them equivalent to just raw material/blanks as the entire mirror making process has to be carried out from scratch. Hence, the work put into making these mirrors is equivalent to a custom made Zambuto mirror made from the ground-up including a precision anneal :)

Also, as Rob(UmaDog) mentioned, Carl has posted some great information in the vendors forum in which he beautifully explains the differences in comparing views between two scopes using the same magnification Vs same exit pupil. Also the part in which he covers the inherent contrast of a system is brilliant!... a must read IMHO! For your convenience, here's the link: Carl's Post :)


#18 JayinUT


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Posted 17 May 2011 - 04:32 PM

Yes, Carl's post is a must read and I did that last night. I copied and pasted it to save it unless it gets stickies.

#19 turtle86


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Posted 17 May 2011 - 05:18 PM

Excellent detailed report!

#20 Al Miller

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Posted 17 May 2011 - 05:36 PM

Thanks Jay for the very detailed and well written report. This is of informative interest to me as I am discussing this very thing in another thread on this forum; the XX14g, and upgrading it with premium optics. Your report actually shows promise for the XX14 by itself if the mirrors I'd get are decent from the start.

#21 GeneT


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Posted 17 May 2011 - 09:58 PM

These kinds of comparative posts are extremely helpful. Thanks so much!

#22 uniondrone


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Posted 18 May 2011 - 06:07 PM

I just spoke with Carl today. My 10" ZOC mirror will ship to the coater today. :jump: The mirror is labeled as Z-250-001. :woohoo:

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