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New Moon Telescopes 20”F/3.3 Review

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#26 ilan_shapira

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Posted 28 October 2020 - 02:44 AM

I have the baby brother to Ilan's scope:  a NMT 12.5" f4.5.  I've been very happy with it, and frequently take it up to Skyline Drive here in Virginia.

 

With respect to JimV's comment, I had Ryan place the focuser further towards the tube's top side.  But while looking down is easier on my neck, it comes with a price:  I have to engage the focuser lock screw a bit more than I'd like.

 

With respect to Ilan's special box to transport the top ring in, I too, made up a box to do this at first.  But then I had Ryan make up some mounting brackets to hold the ring in place about 7" above the mirror box using the truss frame bolts on both the mirror box and the ring.  This saves room in the car while keeping the ring rigidly mounted above the mirror box and out of harm's way.

I stopped using that special box... took a small bucket, big enough to accommodate the entire secondary mirror with an inch to spare, did four notches for the spider limbs, placed it on top and tied gently with a string.

This way I put it on top of the mirror box during drive - bucketed mirror pointing up. saves huge amount of space and very secure.

 

The mounting brackets sounds like a good idea, care to share an image?

 

Regarding the focuser position, when considering the forward placement of tablet stalk which is the one I prefer, having the focuser backwards would have prevented me from using it properly, so all in all, it does its job :)



#27 jcastarz

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Posted 29 October 2020 - 04:48 PM

Mirror Box w/top ring mounted on brackets for travel.
 
Mirror Box w/top ring mounting brackets for travel.

 

Ilan asks:  The mounting brackets sounds like a good idea, care to share an image?

 

*** Your bucket idea is probably just as good, if not better. ***

 

I tried to attach some pictures... I had to load them into my albums first.  Top picture shows ring mounted above mirror box for travel; lower image shows the brackets themselves next to the scope.


Edited by jcastarz, 29 October 2020 - 05:03 PM.

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#28 ilan_shapira

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Posted 31 October 2020 - 12:41 AM



 

 
 
 

 

Ilan asks:  The mounting brackets sounds like a good idea, care to share an image?

 

*** Your bucket idea is probably just as good, if not better. ***

 

I tried to attach some pictures... I had to load them into my albums first.  Top picture shows ring mounted above mirror box for travel; lower image shows the brackets themselves next to the scope.

 

The brackets is a nice idea Keeps the entire UTA stable.

Here is an image of my bucket:

gallery_299831_14856_600120.jpg

 

 

While it keeps the secondary protected, I do have to tie it to the mirror box and put something soft between them to prevent noises and slippage during drive.

 

Thanks for sharing


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#29 jcastarz

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Posted 01 November 2020 - 11:36 AM

Hmmm... I can see better what you were getting at with the "bucket"; I wasn't scaling up the image of my little scope - I envisioned your entire ring wedged inside the bucket!  But you would probably need the sawed-off bottom of a plastic garbage can to fit your ring in.

 

But a problem with the brackets - and indeed, with all scopes that users dismantle at the end of a long night's observing session - is developing good *technique* by which the scope is transitioned to its travel configuration w/o damage.  While the ring is well supported by the brackets once you get it mounted, doing so while you are sleepy, cold, and in the dark can be problematic (as I have noticed).  And a ring as large as yours might be difficult to mount single-handed.

 

It has since occurred to me that a traditional dob scope top could be built - to a much cheaper standard, of course - for the sole purpose of suspending the ring in transit over the mirror box.  The down-side of this approach would be that you'd have this large cylinder to store in the vehicle while the scope is in use, vice a handful of brackets that can be stashed out of the way.  Anyhow, just some thoughts!


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#30 ilan_shapira

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Posted 01 November 2020 - 01:24 PM

Hmmm... I can see better what you were getting at with the "bucket"; I wasn't scaling up the image of my little scope - I envisioned your entire ring wedged inside the bucket!  But you would probably need the sawed-off bottom of a plastic garbage can to fit your ring in.

 

But a problem with the brackets - and indeed, with all scopes that users dismantle at the end of a long night's observing session - is developing good *technique* by which the scope is transitioned to its travel configuration w/o damage.  While the ring is well supported by the brackets once you get it mounted, doing so while you are sleepy, cold, and in the dark can be problematic (as I have noticed).  And a ring as large as yours might be difficult to mount single-handed.

 

It has since occurred to me that a traditional dob scope top could be built - to a much cheaper standard, of course - for the sole purpose of suspending the ring in transit over the mirror box.  The down-side of this approach would be that you'd have this large cylinder to store in the vehicle while the scope is in use, vice a handful of brackets that can be stashed out of the way.  Anyhow, just some thoughts!

At some point I ordered a huge padded box, 24" X 24" (cant remember the height) that keeps the mirror floating and keeps the entire ring stable - it would be the only thing to survive a car crash.

While not heavy it is big and bulky and takes hell lot of space in the car.

 

I usually load the rocker + mirror boxes using a ramp, place one of the mats I carry to the field. On top of it I place the bucketed ring and secure it.

On the field, fellow observers help to load/unload.

I do mount the ring single-handedly, its not difficult - this is one of the things I love about this scope.

However, If I am left the last one standing, I will cover the scope and load it in the morning.

 

I think that the bucket approach is the simplest and easiest to use, but the brackets are excellent for securing the thing in place.



#31 SkywatcherBob

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Posted 01 December 2020 - 01:05 AM

Ilan, Great review and comments.  I just picked up my 22" from Ryan a few weeks ago and still on learning curve.  Previous was 30+ year old C8 and didn't know collimation from column making.  After 1 night in backyard with first quarter moon (fantastic !) went to dark sky, but Full Moon meant not dark and also found planets too bright and Mars with 9mm and Paracoor still just too bright.  Like to know more about masks. What eyepieces are you finding best for galaxies?  Using the 3-6 Nagler 1.25" zoom? Still experimenting and waiting for Moon and clouds to leave.  Thanks for feedback and help.

Ryan 22%22 Dob

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#32 ilan_shapira

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Posted 01 December 2020 - 08:20 AM

Ilan, Great review and comments.  I just picked up my 22" from Ryan a few weeks ago and still on learning curve.  Previous was 30+ year old C8 and didn't know collimation from column making.  After 1 night in backyard with first quarter moon (fantastic !) went to dark sky, but Full Moon meant not dark and also found planets too bright and Mars with 9mm and Paracoor still just too bright.  Like to know more about masks. What eyepieces are you finding best for galaxies?  Using the 3-6 Nagler 1.25" zoom? Still experimenting and waiting for Moon and clouds to leave.  Thanks for feedback and help.

Congrats! that's an amazing scope and a huge jump from C8! 

 

Planets are tough - as I found as well. I did not try masks, but used a neutral density filter to observe Mars and a #80A blue filter for Jupiter. Saturn was fine without a filter but required a perfect conditions - very stable and clear air (got one or two of those per year).

 

What collimation tools do you have? collimation should be accurate as you can with these sizes and focal rations.

 

As for eyepieces, I like the Ethos 8mm for galaxies. It provides good magnification with a wide enough field for navigating galaxy clusters.

 

I once used the Nagler zoom 3-6 a friend brought to a session, used it on M51 & Ring nebula and the views was just amazing. I do plan to get me one of these.

 

My most used eyepiece is the Ethos 21mm. a wonderful all around, wide field. I usually switch between 21 and the 8. For bigger targets - Nagler 31mm is my preferred eyepiece.

 

Once you get a clear and dark skies, you are in for a treat, even more as you have tracking :)

 

I have a new FB group for NMT owners, very few of us so far as its not a common scope, you are more than welcome to it - https://www.facebook...055422524562329


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#33 emastroianni

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Posted 17 February 2021 - 06:42 AM

Nice, comprehensive review. It must have been great under a sky free of light pollution. What is a UTA?


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#34 ilan_shapira

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Posted 18 February 2021 - 04:12 AM

Nice, comprehensive review. It must have been great under a sky free of light pollution. What is a UTA?

Thank you.

A UTA is a abbreviation for Upper Tube Assembly. Its the upper part that holds the secondary mirror.

 

This scope is fantastic under dark skies and I use it as frequently as I possibly can under such skies.

Last week I was lucky to travel to such places twice for my winter galaxy hunt:

https://www.cloudyni...ion-feb-7-2021/



#35 Stevencbradley

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Posted 19 February 2021 - 01:09 AM

While I may never own one of these fine scopes, I would always like to see the owner standing next to it, in order to determine the size of the scope next to a human...



#36 ilan_shapira

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Posted 19 February 2021 - 02:57 AM



While I may never own one of these fine scopes, I would always like to see the owner standing next to it, in order to determine the size of the scope next to a human...

There you go

50958710292_ba08202e11_b.jpg


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#37 Stevencbradley

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Posted 19 February 2021 - 01:40 PM

There you go

50958710292_ba08202e11_b.jpg

Thank you! That's not much different than my memory of my Starmaster 12.5" 



#38 BionicDan

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Posted 06 March 2021 - 01:01 PM

You could do reviews for a living. I just retired. I bought a 5” EQ reflector last month and a 10” dob this month.  Is a 20 next?  Likely not but after how you’ve described your views I look forward to finding a star party with something similar.  Thanks for writing such a clear, detailed review. 


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#39 sanbai

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Posted 06 March 2021 - 02:42 PM

You could do reviews for a living. I just retired. I bought a 5” EQ reflector last month and a 10” dob this month. Is a 20 next? Likely not but after how you’ve described your views I look forward to finding a star party with something similar. Thanks for writing such a clear, detailed review.

When talking about "light buckets", a reasonable next step is gaining 1 magnitude. This is accomplished by multiplying the diameter by 1.58.

(1 magnitude is, 100^0.2 brightness fold difference, the number I gave is the square root, so 100^0.1)

Said that, a NMT 20" is probably a good limit for a dob that a single person can transport and setup easily.

Edited by sanbai, 06 March 2021 - 02:43 PM.


#40 ilan_shapira

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Posted 07 March 2021 - 01:41 AM

You could do reviews for a living. I just retired. I bought a 5” EQ reflector last month and a 10” dob this month.  Is a 20 next?  Likely not but after how you’ve described your views I look forward to finding a star party with something similar.  Thanks for writing such a clear, detailed review. 

If only I could live out of reviewing, sounds like a dream.

You jump in aperture sounds very much like my own. I went from 4" --> 12" --> 20".

In terms of magnitude, I could have made a smaller leap, but selling a 16"/18" as second hand was a waste of money. I knew I would not be satisfied by anything than the maximum I an handle - that there would always be that ting that I could go a bit bigger.

 

I have this scope for a year and a half, I am using it constantly and it fits me like a glove. I am very glad I made that decision.

 

I am glad you enjoyed the review and I hope that you get the chance to observe through a bigger scope.

 

Clear skies


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#41 ilan_shapira

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Posted 08 March 2021 - 02:54 AM

When talking about "light buckets", a reasonable next step is gaining 1 magnitude. This is accomplished by multiplying the diameter by 1.58.

(1 magnitude is, 100^0.2 brightness fold difference, the number I gave is the square root, so 100^0.1)

Said that, a NMT 20" is probably a good limit for a dob that a single person can transport and setup easily.

The 20" can be handled single handedly.

I use a ramp to load it and on the field, another person gives a hand to lower it from the car (both rocker box and mirror box together). If I go alone which is rare, I take the ramp with me.

Separating the mirror box from the rocker box makes it possible to load it by hand to the car.

Yes, its my limit. Another 2" and it will be beyond my abilities.

 

As for setting it up once offloaded, its very easy and takes ~10 minutes:

https://youtu.be/iRjflyrce-s


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#42 bcloud

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Posted 17 March 2021 - 10:13 AM

Thanks for the great review. Wish i was younger and lived in a darker skies area. I have always like the big light buckets for viewing
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#43 George N

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Posted 17 March 2021 - 10:23 AM

The 20" can be handled single handedly.

I use a ramp to load it and on the field, another person gives a hand to lower it from the car (both rocker box and mirror box together). If I go alone which is rare, I take the ramp with me.

Separating the mirror box from the rocker box makes it possible to load it by hand to the car.

Yes, its my limit. Another 2" and it will be beyond my abilities.

.....

Ryan Goodson of NMT has been a friend for at least 10 years. His current personal telescope (at least as of 2 years ago) - is pretty much identical to yours. Prior to that he had a 27" 'Classic Design' - but I never got to look thru that before he sold it - and it really needed 2 people to set up, and a 7 or 8 foot ladder.

 

About 3 years ago - at a major star party - I was already set up with my Obsession 20 ( next to a friend with an ATM 36" F/4 ) when Ryan pulled in and parked on the far side of my truck - where I could not see him. I was amazed to see him appear around my truck *carrying* the entire bottom part of his 20-inch, which he set down about 15 feet from my scope. On a 2nd 'trip' he had the ring UTA and poles - and assembled the scope in like 3 minutes! Third trip brought 'everything else' = chair, table, eyepieces, etc. While he is a healthy young guy who runs marathons - just that quick easy set-up convinced me "if it works, he is on to something with these Hybrid-design scopes!"

 

For me - the 20" F/3.3 requires me to bend down to look thru even when pointed at the Zenith! Ryan has tried to convince me that I need a similar 22-inch - which I might be able to handle - but when I recently ordered one of his scopes my "wallet" said "20-inch F/3.5". I added the new 'narrow' double-ring UTA and carbon fiber poles - and I will probably need a stool or very short ladder for at least other shorter visitors.

 

I have friends with 16, 18, and 22 inchers - and I have had a 20" for 18 years. For me - going from a 16 to a 20 provides a noticeable boost in brightness, but the 16 provides a bigger field of view. Going from an 18 to a 20 or a 20 to a 22 -- you really need to closely compare the views, scopes side-by-side, to see the improvement - which is there - especially if observing the dimmest of galaxies, or looking for small contrast differences - but nothing to get too excited about.

 

As for the 36" -- it takes 4 people to set up (3 in a pinch). The views are fantastic - but even at F/4 -- that's a long way up a ladder in the dark wearing a heavy coat. It also provides lots of sun shade to sit in during the daytime!  cool.gif


Edited by George N, 17 March 2021 - 10:25 AM.

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#44 George N

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Posted 17 March 2021 - 10:35 AM

Thanks for the great review. Wish i was younger and lived in a darker skies area. I have always like the big light buckets for viewing

I can't help you with darker skies -- but the NMT Hybrid is the ideal larger Dob for the senior set. Ryan has told me - "80% of my customers are age 70 and older". ( Most of the NMT owners I know are younger )

 

I would think a reasonably healthy 80 year old could handle a NMT 20" F/3.3 - no ladder, just 3 "parts" to set up - the 'extra stuff', like table, chair, eyepieces, etc - might be more of an effort to move. The newer carbon fiber poles weigh less and add stiffness.

 

When I was sitting next to Ryan's very similar personal 20" F/3.3 at two star parties - people walking by kept asking if it was a 16-inch -- it is that relatively small.


Edited by George N, 17 March 2021 - 10:40 AM.


#45 ilan_shapira

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Posted 17 March 2021 - 01:29 PM

Ryan Goodson of NMT has been a friend for at least 10 years. His current personal telescope (at least as of 2 years ago) - is pretty much identical to yours. Prior to that he had a 27" 'Classic Design' - but I never got to look thru that before he sold it - and it really needed 2 people to set up, and a 7 or 8 foot ladder.

 

About 3 years ago - at a major star party - I was already set up with my Obsession 20 ( next to a friend with an ATM 36" F/4 ) when Ryan pulled in and parked on the far side of my truck - where I could not see him. I was amazed to see him appear around my truck *carrying* the entire bottom part of his 20-inch, which he set down about 15 feet from my scope. On a 2nd 'trip' he had the ring UTA and poles - and assembled the scope in like 3 minutes! Third trip brought 'everything else' = chair, table, eyepieces, etc. While he is a healthy young guy who runs marathons - just that quick easy set-up convinced me "if it works, he is on to something with these Hybrid-design scopes!"

 

For me - the 20" F/3.3 requires me to bend down to look thru even when pointed at the Zenith! Ryan has tried to convince me that I need a similar 22-inch - which I might be able to handle - but when I recently ordered one of his scopes my "wallet" said "20-inch F/3.5". I added the new 'narrow' double-ring UTA and carbon fiber poles - and I will probably need a stool or very short ladder for at least other shorter visitors.

 

I have friends with 16, 18, and 22 inchers - and I have had a 20" for 18 years. For me - going from a 16 to a 20 provides a noticeable boost in brightness, but the 16 provides a bigger field of view. Going from an 18 to a 20 or a 20 to a 22 -- you really need to closely compare the views, scopes side-by-side, to see the improvement - which is there - especially if observing the dimmest of galaxies, or looking for small contrast differences - but nothing to get too excited about.

 

As for the 36" -- it takes 4 people to set up (3 in a pinch). The views are fantastic - but even at F/4 -- that's a long way up a ladder in the dark wearing a heavy coat. It also provides lots of sun shade to sit in during the daytime!  cool.gif

Yes, the scope can be lifted by a single person if needed, that's for sure.

For the sake of my poor back, I use the wheels and ramp - they are available, so why not take advantage of them. The setup itself is extremely easy.

 

Have a fellow astronomer with an 18" Obsession. It's too high for me and required a stool. The feeling of standing on a stool in the dark, leaning toward the eyepiece made me very uncomfortable.

We compared the views and my friend indicated that the view is slightly better with the 20. I also thought there is some improvement but I had hard time to put my finger on the differences.

I wish I had the chance to observe through a 36. Alas, there are no such monsters here :(


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#46 sanbai

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Posted 17 March 2021 - 01:39 PM



I can't help you with darker skies -- but the NMT Hybrid is the ideal larger Dob for the senior set. Ryan has told me - "80% of my customers are age 70 and older". ( Most of the NMT owners I know are younger )


I'm happily sitting in the other 20%. Probably even the 10% younger :)

But what I have on order is "only" a 12.5". The bottleneck are not my mussels, mostly my wallet. True is that that size makes the investment more profitable. A 20" can be transportable, but wouldn't be used as much. I need now something more flexible and light, and that fits in the truck during family vacations. The next step will be a 20", though (I hope).
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#47 ecorm

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Posted 03 April 2021 - 04:17 AM

A few questions regarding your 20" f/3.3 NMT:

  • What is the eyepiece height when pointed at zenith?
  • What size is the secondary mirror?
  • What is the interior diameter of the UTA?


#48 ilan_shapira

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Posted 07 April 2021 - 03:40 PM

 

A few questions regarding your 20" f/3.3 NMT:

  • What is the eyepiece height when pointed at zenith?
  • What size is the secondary mirror?
  • What is the interior diameter of the UTA?

 

Eyepiece max height - 160cm

Secondary size - 11.5cm diameter (as seen from above)

Interior UTA diameter - 53cm


Edited by ilan_shapira, 07 April 2021 - 03:41 PM.

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#49 MikeTahtib

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Posted 01 May 2021 - 07:33 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. 



#50 George N

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Posted 01 May 2021 - 11:01 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. 

Interesting question!

 

While I'm not the owner of this telescope ( I do have a NMT 20" F/3.5 on order - a little longer FL for significant $$ and time-to-produce savings ) -- I have observed thru a few other F/4 and faster Dobs (F/4 32", 36", and F/3.8 22" ) - including NMT owner Ryan Goodson's personal 20" F/3.3 on about 6 nights -- with Paracoor = F/3.8. It was only under very dark sky ( SQM = 21.7+ ). Ryan himself had a 31mm Nagler and, being a 'star hopper' with no electronics on his scope - he regularly used the N 31 at least for hunting down targets.

 

The Televue 'eyepiece calculator' says N31 + Paracoor + 20" F/3.3 = 61.2 power, 1.3 degree true field of view, and 8.2mm exit pupil == that would be - in theory, way too big of an exit pupil that would certainly show the secondary shadow. Televue recommends not going larger than 7.5mm EP and my own eyes only open up to 6.5mm. Yet -- I remember quite pleasing views thru Ryan's 20" F/3.3 using his Paracoor and N31. I would guess that the shadow could be seen under brighter light polluted skies. Using a N31 with a scope this fast is probably a compromise - but usable at times - especially if looking for a target, or maybe with an O-III filter at something like M-42 or the Veil. For everyone but the 18 year old Jolly Green Giant - you would be thro'ing away a significant part of the light gathered by that 20" primary - but for certain targets - it might not be an issue.

 

Looking at Televue's 'eyepiece calculator' the widest field of view that can meet their recommendations of 7.5mm exit pupil is -- a 21mm Ethos = 90.4 power, 1.1 degree field, 5.5mm exit pupil. This is probably the widest true field that will use all of this telescope's collected light, with no 'secondary shadow' for most people. "Close enough" other TV eyepieces include the discontinued 26mm Nagler ( I own one and like it ), the 22mm Nagler ( I don't own one, but friends do - excellent ep ) and the 27mm Pan ( never looked thru one ).

 

BTW - I have observed thru a friend's 36" F/4 and an Explore Scientific 30mm 100 degree 3-inch eyepiece -- which probably violates all 'the rules' -- but scanning over M-31 looked like a CCD image -- and could keep me happy all night -- or until I fell off the ladder!  wink.gif

 

Bottom line - in my opinion: Owning a telescope like this - 'premium' 20+ incher faster than F/4 -- will mean living with some compromises - but still fantastic views from a telescope that does not require a ladder and most adults would find very easy to move and assemble and use - with only minor to no difference compared to a 'classic' 20" at F/5 or F/6 ( something that I've owned for 18+ years ). A scope like this NMT *will* require very high end eyepieces (but you could live with only 3), some extra precision with collimation, and a desire to buy a neat little APO refractor for wide-field views - or in my case, 20x80 binoculars. After being convinced by the views I've seen, and realizing at age 73 my 'ladder days' are coming to an end - I ordered a NMT 20" F/3.5 -- and would have gotten a 22" if not for the $$ increase. If -- you can 'live easy' with ladders, more than twice the weight, and longer more complicated to assemble structure - at a considerable $$ savings (probably used only today) -- then a 20" F/5 'Classic' Dob could be a better choice.


Edited by George N, 01 May 2021 - 11:12 AM.

  • MikeTahtib likes this


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