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New Moon Telescopes 20”F/3.3 Review


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New Moon Telescopes 20”F/3.3 Review

 

It's been just over six months of usage of the NMT 20"F/3.3 telescope and I feel it’s about time I share my experience with it.

 

The scope and a NMT observation chair are waiting for dark skies in the Israeli desert

 

I have been hooked on astronomy ever since childhood, but life always pulled me in different directions, until two years ago. At that time I got an achromatic refractor and from there the sky stopped being the limit. After that I moved to a Sky Watcher 12" Dob and quickly understood that I loved dobs, and wanted a bigger one.

 

How big? As big as I can handle.

 

Currently owned scopes:

NMT 20"F/3.3

Celestron 8" Evolution

 

 

On my future list:

A sun scope for visual use

An Apo refractor for wide field views

 

I have set the following requirements for a big dob:

- No need for a stool/ladder

- Fits in my car

- Secure during drive

- Secure in the field

- Easy to assemble/disassemble

- Good optics

- Collimation hold

- Last but not least - Mechanics

 

The option of a 20" was not on the table - I didn't know that such big and fast scopes are available to amateurs and once I did, the price was a bit of a blocker. However, doing some math (more with my heart than with my head) made me realize that compromising on an expensive instrument will only cause me regrets and eventually, I decided to buy the one I really want.

 

After some research and discussions with a few vendors and Ryan from NMT, I realized that this is the instrument that answers my needs.

 

I ordered the 20"F/3.3 with Fullum Optics Mirror, Feathertouch ultralight focuser, Secondary dew heater, Thousand oak dew controller, Telrad, mount for optical finder, wheelbarrow handles and a custom Tablet & 2” eye pieces stalk and with the selected type of woods - you get to choose which type each part is made - full customization.

 

Build process images were shared constantly.

 

The scope arrived on time.

 

After six months of usage I am ready to share my experience and double check how the scope answered my requirements:

 

No need for a stool/ladder:

The focuser in zenith is at the correct position - flat feet and no stretching the neck is required

 

Fits into my car:

Fits. This was known of course, but the first time I loaded it was a bit scary. The scope is not light weighted - its mirror box (with mirror included) is 61 pounds. I managed to lift it alone on a few occasions, But I prefer a pair of aluminum ramps for loading. The wheelbarrow comes with big wheels, making the process of loading easy.

 

Folding Loading Ramps

 

Secure during drive:

The mirror box is solid and there is a wooden cover to protect it, no flexible plastic covers here. Very secure

 

Secure in the field:

Again, the mirror is within a solid box and is well protected. There is a very small opening in the back,  but it exposes the bottom of the mirror, not its surface.

 

Easy to assemble/disassemble:

Assembly is a breeze. I remember attending an outreach in which a specific 18" truss scope was assembled - by 4 people. Out of the box, Assembling the NMT was easy - and it was the first time I assembled a Truss scope myself. disassembling is easy as well. The only thing that might be considered hard is loading/offloading from the car. Again, with the ramps, I can do it alone.

 

Collimation hold:

I did not notice a worsening in views during a full night. I tested it at the end of the night once as using a cheshire requires light. It was still collimated. Many warned that a scope that fast requires extra precise collimation. So it's a laser for rough collimation and a cheshire for the final tuning. Works like a charm.

 

Mechanics:

I can't stress enough how important the mechanics are in a scope. My 12" had a slight backlash when moving, the movement was not very smooth, it had freedom that could suffer from wind (actually moved) and its balance was terrible - using ES 24mm/82 eyepiece caused it to sag when pointing below 30 degrees.

 

The NMT does all of this differently. First of all, although there is the option to mount counterweights, there is no need. The altitude bearings are big and provide extraordinary balance. The scope stays balanced with a Nagler 31mm + Paracorr type 2 + optical finder or without any accessory!

 

Horizontal movement is also smooth but with a bit firmness, preventing the scope from moving from stray wind gusts.

 

Replacing eyepieces leaves the scope right on target.

 

The combination of smoothness, firmness and no need for counterweights makes this instrument mechanically perfect.

 

(balanced perfectly with everything mounted on top)

 

Optics and View:

I am no expert in this area and my eyes are not perfect, I will share my experience with it and stuff that friends noted.

 

- Nebulae - The views are amazing and exceeding anything I expected. Lots and lots of details. From Orion to California, to Veil to the summer Nebulae all look fantastic. It was the first time I saw the Horse head. no need for averted imagination.

 

- Globular clusters - spectacular, stars can be seen very deep within them

 

- Open clusters - with this scope, open clusters jumped in priority for me as they are visible in their full glory. The double cluster, fitting in the field of view is just wonderful

 

-  Galaxies - Here comes the true power of the 20". More details than expected in the smaller galaxies, galaxies that were not there before suddenly pops out and the big ones - M51 for example - are full of details. Arms are distinguishable, details between them are clearly visible, swirls of dust and the arm that slaps NGC 5194. Viewed it with the 3-6 Nagler zoom and could discern so many details.

 

- Double stars - There are better scopes for splitting multiple stars. While stars are as pinpoint as possible in a F/3.3, it requires the best of conditions to view the bright ones in high magnification.

 

- Planets - I have mixed feelings about observing planets with this scope. The secondary mirror is huge and as such, the contrast suffers. In addition, such bright objects suffer greatly from bad atmospheric conditions. If it shakes, the image shakes. I did however manage to have one exceptionally good and stable night where the planets shone (shone and harmed my night vision) with many details visible such as Encke Gap on Saturn and On Jupiter, swirling clouds could be visible.

 

- Moon - Here, even with the huge central obstruction, the moon, even going to the limit of my manual tracking and atmospheric disruptions is very vivid and full of details. One can lose himself in lunar views.

 

Comments from friends and colleagues:

One friend indicated an astigmatism that is noticeable in high magnifications, others, not less experienced than him, viewed in x450 & x600 and did not notice any issue.

 

A friend with an 18" noted that he could see more details in M51, and others with many years of observation experience indicated that they had the best views using this scope.

 

Our astronomy club elder noted the excellent quality of the mirror, He was amazed that an F/3.3 could provide such performance.

 

Any one that observed through the scope noted the superb mechanics and fun of handling it.

 

Improvements?

Maybe getting the scope with a full UTA could have been better - secondary mirror more protected during drive and without a special case I ordered for it, could even take less space in the car. In addition, the Focuser position could have been placed a bit higher and not leveled with the ground which could have made viewing very low objects a bit easier (usually I don’t go that low).

 

- Full UTA might handle dew better?

 

- Removable altitude bearings can dramatically reduce the scopes footprint inside the car and is well to be considered (it would however complicate assembly/disassembly).

 

These issues have zero effect on my experience with the scope.

 

To sum things up

This instrument answers to all my requirements from a big dob and is mostly used during my dark site trips.

 

While double stars and planets are not the specialty of this scope, it handles them fairly well, but requires extra good conditions - backyard usage is not optimal as atmospheric disturbances dramatically affect the views.

DSOs is where this instrument excels and provides the best performance under dark skies, especially with faint galaxies.

 

During my last dark site session, after the COVID-19 restrictions lifted, I had barely time to observe myself as others lined up to view instead.

 

Bottom line:

For usage under dark skies, this is the best instrument I could get for myself. You buy such a scope once and you get a device for a lifetime!


  • Mark Strollo, George N, Neptune and 11 others like this


21 Comments

Amazing telescope. got to use Ilan's NMT on few occasions. 

 

Mechanics - smooth as butter. it's unbelievable how smooth a 20" monster can be.

Optics - again, wow. Details on nebula like no other. M42 reviles so many details. faintest galaxies show clear structures.

    • ilan_shapira likes this

Great review, well-balanced and detailed.

    • ilan_shapira likes this

Great scope! nebulae must be awesome in that thing, averted imagination?

Photo
ilan_shapira
Sep 01 2020 02:17 AM

Great scope! nebulae must be awesome in that thing, averted imagination?

Thanks,

No averted vision is required. Nebulae, are magnificent with this scope, so many details that previously did not exist at all.

Great review. I'm right there with you on mechanics. My 12" Lightbridge has terrible mechanics. Not just from balance, but from backlash and a bad lazy susan that squealed like a pig being murdered when it got cold out.

 

When I built my 15" I set out with the goal to make it as stiff as possible with just the right amount of friction to provide balance for my equipment without unnecessary force to move the scope (which makes dealing with backlash harder).

Nothing more frustrating than trying to track an object at high power and fighting backlash.

    • ilan_shapira likes this
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stargazer193857
Sep 01 2020 05:00 PM
Backlash, what you get from too much resistance combined with a flexing structure. Yes, NMT has this area figured out.
    • George N and ilan_shapira like this

I had the same problem with planets when using my 22" F/3.3 Teeter. I got much better views of planets in my 4"Tak.

a) big Dob is not "planetary" scope

b) I made aperture mask to mitigate the problem - relatively cheap solution.

 

See elsewhere here on CN for mask designs

    • ilan_shapira likes this
Photo
stargazer193857
Sep 02 2020 08:09 AM

I had the same problem with planets when using my 22" F/3.3 Teeter. I got much better views of planets in my 4"Tak.
a) big Dob is not "planetary" scope
b) I made aperture mask to mitigate the problem - relatively cheap solution.

See elsewhere here on CN for mask designs

Very informative data point.
Was this an off axis mask you tried on all 4 quadrants? Or just cutting off the edge, which might have reduced turned down edge?

If a big aperture performed worse on planets at the same magnification when aperture drastically reduced, that supports some theory about eye accommodation or even atmospheric cells.


Some claim that bigger is always at least as good as smaller, and just looks worse because it operates at higher mag, or can resolve turbulence better. They also say cooling of the big mirror is the issue. But if you tested with and without a quadrant mask on all 4 quadrants, that would refute those theories.
Photo
stargazer193857
Sep 02 2020 08:14 AM

Thanks,
No averted vision is required. Nebulae, are magnificent with this scope, so many details that previously did not exist at all.


What aperture was your previous scope?
Photo
ilan_shapira
Sep 02 2020 02:34 PM

I had the same problem with planets when using my 22" F/3.3 Teeter. I got much better views of planets in my 4"Tak.

a) big Dob is not "planetary" scope

b) I made aperture mask to mitigate the problem - relatively cheap solution.

 

See elsewhere here on CN for mask designs

Thanks.

I totally agree on 'a', size (planets too bright, with filters) + F ration are against them.

As for the suggestion for a mask, I will check it out, its interesting.

I do however have a grab and go SCT that is perfect for the planets and has tracking - easier to view at high magnification and easier to deploy quickly.

Photo
ilan_shapira
Sep 02 2020 02:37 PM

What aperture was your previous scope?

Had a 12", but had more than one chance to observe via 14", 15" & 18"

Nothing in a 20" that didn't exist in the 18", but comparing to the 12" its a huge jump.

Photo
spacedoutbob
Sep 03 2020 08:31 AM

Very nice scope, About how much does such a instrument like yours cost?

Photo
ilan_shapira
Sep 03 2020 11:05 AM

Very nice scope, About how much does such a instrument like yours cost?

You can see the prices on New Moon Telescopes website.

Each depends on optics, extras and more

    • George N likes this
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spacedoutbob
Sep 03 2020 03:38 PM

Thank you, Bob

Very informative data point.
Was this an off axis mask you tried on all 4 quadrants? Or just cutting off the edge, which might have reduced turned down edge?

If a big aperture performed worse on planets at the same magnification when aperture drastically reduced, that supports some theory about eye accommodation or even atmospheric cells.


Some claim that bigger is always at least as good as smaller, and just looks worse because it operates at higher mag, or can resolve turbulence better. They also say cooling of the big mirror is the issue. But if you tested with and without a quadrant mask on all 4 quadrants, that would refute those theories.

It's a single hole off axis mask. One mask has 4" diameter hole (to compare it with my 4" refractor). The other mask has 7" hole to maximize the off axes = no spikes = refractor like experience. Side by side, tested in my back yard, 4" dia mask performed as well as my refractor (at similar magnifications). So, when I travel to dark site I only bring my DOB (which is quite a lot by itself) I do not need to bring another telescope.  The 7" mask on my DOB gives me roughly F/10 which is nice for the planets.

I believe the problem with the bigger aperture is the atmospheric cells. Under ideal conditions the bigger aperture would naturally perform better. This is my experience, others may have different results.

    • ilan_shapira likes this
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stargazer193857
Sep 04 2020 06:09 PM

You can see the prices on New Moon Telescopes website.
Each depends on optics, extras and more


If it is from NMT, that means the mask did not just hide a bad zone. So testing just one sector was good enough.
Photo
Sagiflarius
Sep 13 2020 02:53 PM

Thanks for a great review and very helpful comments.  I've been thinking a lot in the last few months and I now think a high-end, big aperture Dob is the right direction for me in the long run.

 

I have a Meade 8" SCT (an old one from a friend but seems fine).  I was wondering about a 16" Orion truss Dob or a Sky Watcher 16" collapsible for fixed use, but I think it makes sense to start with a cheap 12" Dob, take advantage of the portability and save up in the longer term for a serious big Dob to be installed in an observatory I plan on building at my new place in the next 18 months.

 

This has helped firm up my thinking that a big high-end Dob is my end goal. I've read a bit about masking, but I only thought of it in the sense of dealing with big aperture in turbulent seeing and had missed the idea of making a big fast dob work better with planets.  Almost like having two or more scopes in one, to suit viewing conditions and what you're viewing.

Great review!

 

First: I've been an owner of an Obsession 20" F/5 for 18 years, and I've known Ryan for at least 8 years - going back to the days he was 'just' making a few scopes for good friends. Three friends own NMT Dobs - of the earlier "classic" design, but built to the same standard of perfection as the current Hybrid design. I've seen, but never observed thru the big 27" and 36" "classics" that he made in prior years. I'm a member at Kopernik Observatory & Science Center, Vestal, NY - which owns a specially commissioned 12.5" Dob by NMT designed for use by folks in a wheel chair. It is a very fine instrument.

 

I've set up next to Ryan at several star parties (CSSP, Black Forest, Stellafane) over the years and had the opportunity to use his personal telescope - pretty much identical to the one reviewed. I had already come to the same conclusions as this review! On one lazy afternoon Ryan and I played around with a laser collimator - moving the scope around to various positions, and we saw no drift in the laser position at all. At night - I saw only superb views completely comparable to my 20" F/5 with an excellent mirror.

 

The "down sides" mentioned are - to me - "normal" for a 20-inch Dob of any "brand" or ATM origin. On those few excellent seeing nights we have in the Northeast - you can't beat one - but on most nights the big Dobs are best used on faint fuzzies. I did note with Ryan's scope (one of the first Hybrids) that the movement was a little stiff compared to my Obsession 20 - something he said could be improved. Oh -- and I had to bend down to view thru the eyepiece even near the zenith - a three step up the ladder climb for my Obsession 20! I would think for a 6 footer like me, most viewing would require a stool with this scope.

 

Finally - at age 72 I'm pretty close to no longer wanting to view perched on a frosted-up ladder wearing winter gear. It is getting close to the time to pass on my excellent 20-inch F/5 to a lucky younger person who can take advantage of it for another 18 years. I am very likely to order a 20 or 22 NMT of similar design as my next 'no ladder' big Dob.

    • rowdy388, stargazer193857 and ilan_shapira like this
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ilan_shapira
Sep 15 2020 03:43 AM

Thanks for a great review and very helpful comments.  I've been thinking a lot in the last few months and I now think a high-end, big aperture Dob is the right direction for me in the long run.

 

I have a Meade 8" SCT (an old one from a friend but seems fine).  I was wondering about a 16" Orion truss Dob or a Sky Watcher 16" collapsible for fixed use, but I think it makes sense to start with a cheap 12" Dob, take advantage of the portability and save up in the longer term for a serious big Dob to be installed in an observatory I plan on building at my new place in the next 18 months.

 

This has helped firm up my thinking that a big high-end Dob is my end goal. I've read a bit about masking, but I only thought of it in the sense of dealing with big aperture in turbulent seeing and had missed the idea of making a big fast dob work better with planets.  Almost like having two or more scopes in one, to suit viewing conditions and what you're viewing.

Thanks!

I also have an 8" SCT as my grab and go setup and for planets and moon views - with tracking.

I did however, viewed Mars last Friday (Sep 11 2020) from a dark site in the desert. The air stabilized close to midnight and the view of the red planet through the 20" blew me away, so many details that you can actually sit down with a map of Mars and mark some items down.

But yes, when the air is less stable, these big guys tend to collect the instability as well as the light.

 

I will try the masking, it is indeed interesting option.

 

I am happy the review helped you. a 12" will do you lots and lots of good while you save for your end goal.

Clear Skies

    • cmas likes this
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ilan_shapira
Sep 15 2020 07:22 AM

Great review!

 

First: I've been an owner of an Obsession 20" F/5 for 18 years, and I've known Ryan for at least 8 years - going back to the days he was 'just' making a few scopes for good friends. Three friends own NMT Dobs - of the earlier "classic" design, but built to the same standard of perfection as the current Hybrid design. I've seen, but never observed thru the big 27" and 36" "classics" that he made in prior years. I'm a member at Kopernik Observatory & Science Center, Vestal, NY - which owns a specially commissioned 12.5" Dob by NMT designed for use by folks in a wheel chair. It is a very fine instrument.

 

I've set up next to Ryan at several star parties (CSSP, Black Forest, Stellafane) over the years and had the opportunity to use his personal telescope - pretty much identical to the one reviewed. I had already come to the same conclusions as this review! On one lazy afternoon Ryan and I played around with a laser collimator - moving the scope around to various positions, and we saw no drift in the laser position at all. At night - I saw only superb views completely comparable to my 20" F/5 with an excellent mirror.

 

The "down sides" mentioned are - to me - "normal" for a 20-inch Dob of any "brand" or ATM origin. On those few excellent seeing nights we have in the Northeast - you can't beat one - but on most nights the big Dobs are best used on faint fuzzies. I did note with Ryan's scope (one of the first Hybrids) that the movement was a little stiff compared to my Obsession 20 - something he said could be improved. Oh -- and I had to bend down to view thru the eyepiece even near the zenith - a three step up the ladder climb for my Obsession 20! I would think for a 6 footer like me, most viewing would require a stool with this scope.

 

Finally - at age 72 I'm pretty close to no longer wanting to view perched on a frosted-up ladder wearing winter gear. It is getting close to the time to pass on my excellent 20-inch F/5 to a lucky younger person who can take advantage of it for another 18 years. I am very likely to order a 20 or 22 NMT of similar design as my next 'no ladder' big Dob.

I wish I could have met with Ryan to raise a toast for his excellent craftsmanship. This scope has brought me nothing but excellent observations beyond my expectations - and this Friday, Sep 11, I have been to the desert on a dark skies and had a huge fun tracking down faint galaxies in Andromeda.

As I told Sagiflarius, at midnight that night, the air was so still, and Mars was just amazing.

 

Its a full package here, optics, height & mechanics that makes this a superb instrument for DSO.

Planets I can view from home, with a smaller scope and tracking, but under dark skies - the NMT shines

    • George N likes this

My homemade 17.5" f/4.4 has the focuser at 30 degrees rather than horizontal.  Makes for much less neck stress.  It's easier to look downwards than get on your knees and look upwards.

I don't know why Obsession, Webster, and NMT make this design mistake.



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