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New Moon Telescopes 20”F/3.3 Review

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#51 ilan_shapira


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Posted 01 May 2021 - 11:53 AM

I was wondering if you start seeing a shadow of the secondary at low magnification (large exit pupil) when using low power, for example the 30mm Nagler.  I notice this sometimes when observing the moon with my f4.5 telescope, but of course, my eye's pupil is greatly reduced under those circumstances.  I would imagine at some point, with increasing exit pupil, it could become an issue even looking at DSOs, but I'm not sure from a practical point fo view at what point this would happen, if ever. 

My most used eyepiece is the Ethos 21mm - good EP, wide field and decent magnification for medium objects.

I do use the Nagler 31 - some objects are just viewed best with it. I do not see the secondary shadow when using it.


When a friend brought his Explore Scientific 40mm/62 degrees the secondary shadow was apparent and it was hard to observe with it.

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#52 sanbai



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Posted 01 May 2021 - 11:02 PM

There's something that makes the 31T5 be worth in fast scopes: one can see the whole field when using glasses or Dioptrx.

Those that have negligible astigmatism can go for a Ethos 21. Otherwise, the 100° cannot be enjoyed. Next eyepiece with a field stop close to the maximum is the 31T5. With astigmatism + Dioptrx or glasses + f/3.x it's a compromise: 31T5 for widest true field with wasted exit pupil, or a 22T4 with a smaller field. If one is lucky and astigmatism is very low the Ethos 17 without correction is another option. Next option is ES92 17 with glasses.

My NMT on order will be f/4.5 (5.15 with PC2). Perfect for 31T5 with Dioptrx. I should be able to use the Ethos 17 without it, just OK. If my astigmatism goes a bit higher, the Nagler 22 and 17 T4 are ready.

I'm glad to hear that shadow of the secondary is not disturbing with the Nagler 31 and a faster scope.

Anyway, despite astigmatism being more evident, a f/3.x class has still the huge advantage of keeping your feet on the ground. And a larger f/# won't solve the issue of largest true field possible with pin point stars at your maximum pupil. We have to live with that! (Glad that mine is mild... actually my *non* observing eye has zero! But cannot change the habit)

Edited by sanbai, 01 May 2021 - 11:05 PM.

#53 George N

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Posted 09 May 2021 - 09:48 AM

NMT has up-dated their website - nice pictures!


They seem to be still tinkering with it - here's the link: https://www.newmoontelescopes.com/


...and since this thread is about the NMT 20 - here's the 'shop' page for the 20-inch: https://www.newmoont...s.com/shop/p/20


It is interesting that this page does not list the single ring UTA that the review telescope has (and Ryan's personal 20-inch, that I have used ) -- Only "Choice of Traditional UTA or Carbon Fiber/Aluminum Sandwich Ring (Upgrade)" Perhaps Ryan will build what you want, but this is just a concession to what people are now ordering?


The website is a little conflicting on projected delivery times. In one place it says "6 to 9 months" - which is what I was advised ( but not promised ). in the FAQ section it says "Our wait time has slowly creeped up and is now up to 12 months for a New Moon Telescope.  Orders are still coming in, so if you’re interested in a custom hardwood telescope, we suggest you do so soon, as we may have to increase our lead time again, once a threshold is met."


Meanwhile -- on FaceBook NMT posted that - with the nearly 300% increase in wood prices, and increases in Aluminum and carbon fiber tubing prices - the telescope prices may have to go up soon. I didn't compare the current to the recent past - but I guess it is only to be expected.


I'm not holding my breath -- but if everything comes together -- just maybe I'll get a picture of me, Ryan, and Normand Fullum standing next to my new NMT 20 at Stellafane 2021 -- on top of Breezy Hill. -- 2022 is a more likely time for this to happen.

Edited by George N, 09 May 2021 - 09:50 AM.

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