Jump to content

  •  

CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.

Photo

New Moon Telescopes 20”F/3.3 Review

  • Please log in to reply
21 replies to this topic

#1 ilan_shapira

ilan_shapira

    Explorer 1

  • *****
  • topic starter
  • Posts: 94
  • Joined: 06 Sep 2018
  • Loc: Israel

Posted 29 August 2020 - 12:22 PM

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.

Click here to view the article
  • The Ardent, ShaulaB, stargazer193857 and 2 others like this

#2 Guydive

Guydive

    Vostok 1

  • *****
  • Posts: 161
  • Joined: 29 Jun 2019
  • Loc: NYC/TLV

Posted 31 August 2020 - 03:16 AM

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

#3 Starman81

Starman81

    Soyuz

  • *****
  • Posts: 3,808
  • Joined: 06 Mar 2008
  • Loc: Metro Detroit, MI, USA

Posted 31 August 2020 - 08:21 AM

Great review, well-balanced and detailed.


  • ilan_shapira likes this

#4 Stellar1

Stellar1

    Viking 1

  • -----
  • Posts: 581
  • Joined: 08 Dec 2018
  • Loc: Ontario, Canada

Posted 31 August 2020 - 08:08 PM

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



#5 ilan_shapira

ilan_shapira

    Explorer 1

  • *****
  • topic starter
  • Posts: 94
  • Joined: 06 Sep 2018
  • Loc: Israel

Posted 01 September 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.



#6 CrazyPanda

CrazyPanda

    Vanguard

  • *****
  • Posts: 2,386
  • Joined: 30 Sep 2012

Posted 01 September 2020 - 12:20 PM

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

#7 stargazer193857

stargazer193857

    Cosmos

  • *****
  • Posts: 9,790
  • Joined: 01 Dec 2013
  • Loc: Southern Idaho

Posted 01 September 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

#8 slavicek

slavicek

    Ranger 4

  • *****
  • Posts: 369
  • Joined: 01 Aug 2017
  • Loc: Massachusetts

Posted 01 September 2020 - 07:37 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


  • ilan_shapira likes this

#9 stargazer193857

stargazer193857

    Cosmos

  • *****
  • Posts: 9,790
  • Joined: 01 Dec 2013
  • Loc: Southern Idaho

Posted 02 September 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.

Edited by stargazer193857, 02 September 2020 - 08:12 AM.


#10 stargazer193857

stargazer193857

    Cosmos

  • *****
  • Posts: 9,790
  • Joined: 01 Dec 2013
  • Loc: Southern Idaho

Posted 02 September 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?

#11 ilan_shapira

ilan_shapira

    Explorer 1

  • *****
  • topic starter
  • Posts: 94
  • Joined: 06 Sep 2018
  • Loc: Israel

Posted 02 September 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.



#12 ilan_shapira

ilan_shapira

    Explorer 1

  • *****
  • topic starter
  • Posts: 94
  • Joined: 06 Sep 2018
  • Loc: Israel

Posted 02 September 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.



#13 spacedoutbob

spacedoutbob

    Explorer 1

  • *****
  • Posts: 63
  • Joined: 26 Mar 2008
  • Loc: California

Posted 03 September 2020 - 08:31 AM

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



#14 ilan_shapira

ilan_shapira

    Explorer 1

  • *****
  • topic starter
  • Posts: 94
  • Joined: 06 Sep 2018
  • Loc: Israel

Posted 03 September 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

#15 spacedoutbob

spacedoutbob

    Explorer 1

  • *****
  • Posts: 63
  • Joined: 26 Mar 2008
  • Loc: California

Posted 03 September 2020 - 03:38 PM

Thank you, Bob



#16 slavicek

slavicek

    Ranger 4

  • *****
  • Posts: 369
  • Joined: 01 Aug 2017
  • Loc: Massachusetts

Posted 03 September 2020 - 08:31 PM

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

#17 stargazer193857

stargazer193857

    Cosmos

  • *****
  • Posts: 9,790
  • Joined: 01 Dec 2013
  • Loc: Southern Idaho

Posted 04 September 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.

#18 Sagiflarius

Sagiflarius

    Sputnik

  • -----
  • Posts: 29
  • Joined: 16 Jan 2020
  • Loc: Bristol, United Kingdom

Posted 13 September 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.



#19 George N

George N

    Fly Me to the Moon

  • *****
  • Posts: 5,851
  • Joined: 19 May 2006
  • Loc: Binghamton & Indian Lake NY

Posted 14 September 2020 - 10:11 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.


  • rowdy388, stargazer193857 and ilan_shapira like this

#20 ilan_shapira

ilan_shapira

    Explorer 1

  • *****
  • topic starter
  • Posts: 94
  • Joined: 06 Sep 2018
  • Loc: Israel

Posted 15 September 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

#21 ilan_shapira

ilan_shapira

    Explorer 1

  • *****
  • topic starter
  • Posts: 94
  • Joined: 06 Sep 2018
  • Loc: Israel

Posted 15 September 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

#22 JimV

JimV

    Viking 1

  • *****
  • Posts: 575
  • Joined: 06 Nov 2013
  • Loc: Austin, TX

Posted 21 September 2020 - 03:16 AM

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.




CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.


Recent Topics






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics