23 replies to this topic

[allen g]

I am pondering getting the 2.5 for use in my TV NP-101 (4" apo).  This would give 216x which I intend to use for splitting stars.  Currently, I have EPs which when barlowed take me down to 3mm.  Anyone have experience with or thoughts about this EP that they can share.  Thanks in advance. allen

[Starman1]

I've used the 2-4 zoom in that scope, but found the 2-3 range too high for my seeing conditions.

You will be able to use the 2.5, but you will need REALLY SUPERB seeing.

[Jon Isaacs]

I've used the 2-4 zoom in that scope, but found the 2-3 range too high for my seeing conditions.

You will be able to use the 2.5, but you will need REALLY SUPERB seeing.

 

For close double stars with my NP-101, I use the 3.5mm and the 5mm Naglers with a 2x Televue Barlow.   Close to the Dawes limit, high magnifications are helpful because the disks are overlapping.  

 

Jon

[Jim Romanski]

I have a Nagler 2.5mm that I used when I had an NP-101.  It's a very nice eyepiece and while not every night has seeing good enough for that much power many nights do. 

 

It's a great eyepiece for very small refractors with short focal lengths like my AT72 lots of power and fairly light.

[FirstSight]

I too am intermittently smitten with the notion of picking up a 2.5mm T6 for my NP-101 for use on both planets and double stars, and maybe a 3.5T6 as well to have a complete, compact, lightweight set (I already have the other five T6s).  What (so far) has repeatedly dampened such thoughts back to earth is the $225-250 cost of a used 2.5 T6 (or $300+ new), double that if I also add the 3.5 T6 for a complete set.  That, and the fact that I already have a 2x Powermate, a 5T6, a 7T6, a 3.7 Ethos and a 4.7 Ethos and can thus readily achieve the desired focal-lengths with my existing (not exactly cheap) investment in eyepieces - has restrained me from pursuing the idea more than occasionally scanning A-Mart eyepiece classifieds (I've already passed on the couple of infrequent opportunities for a used 2.5T6 I've come across).

 

OTOH, if Televue ever extended the Ethos line with a 2.5mm Ethos - which would cost in the near ballpark of a new 2.5 AND new 3.5T6 combined, I would be sorely tempted.  But that is unlikely to happen for the same reason used 2.5T6s don't come up for sale very often - there just isn't enough demand for expensive glass in that short a focal-length to be worth their while.

[penguinx64]

I too am intermittently smitten with the notion of ...

 

Intermittently smitten?

[allen g]

Chris, how does your 5t6 and ethos 4.7 when barlowed work on your np-101? 

[FirstSight]

Chris, how does your 5t6 and ethos 4.7 when barlowed work on your np-101? 

 

Both work really well optically - the only issue is the extra overhead of installing both PM and EP, plus the extra rebalancing necessitated by the PM.  And yes, it changes the EP height for viewing as well, but my adjustable observing chair mostly negates any issues with that factor.

[FirstSight]

 

I too am intermittently smitten with the notion of ...

 

Intermittently smitten?

 

 

As in, the idea sometimes seems seductively attractive to actually execute until I start thinking about parting with the amount of money it will cost, and whether it's really worth spending on adding more eyepieces to the seventeen Naglers and Ethos and two PMs I already have.

[John F]

I have a 2.5mm T6 Nagler that I use with an NP-127 scope which is similar to your NP-101 in that they both have rather short focal lengths for their respective aperture sizes.  On the NP-127 the 2.5N provides 264x but I don't use very often (other than during the summer months) because of atmospheric turbulence.  The main reason I got the eyepiece was so that I could use it for splitting double stars and when conditions permit its use, it works quite well.

 

When working at very high powers and very small fields it is much easier to just use individual eyepieces than it is to use eyepieces in combination with a Barlow.  This is especially true if you don't have a motor driven mount to keep the object in the center of the field while you're switching between eyepieces.  Its also nice that the 2.5N provides such a large field for its short focal length  and the very high powers that you have to use it at.   

 

Because of the very high powers it yields this isn't an eyepiece that will probably work well with most telescopes.  However, my NP-127 is one that it does work well with and I'm pretty sure that it will also work very well with your NP-101 (provided that you don't have to wear eyeglasses while observing because the eye relief of this eyepiece is only 12mm). 

 

 

 

  

[areyoukiddingme]

I agree with the superb seeing sentiment. . . I have the older scope, the non-NP plain vanilla 101. I have barlowed my 4.7 ethos to good effect. I have also barlowed my 3-6 zoom and was delighted to find that even at crazy high mags the scope still gave useful views of the moon on a really, REALLY good night. But I have yet to replicate the experience and suspect if/when it comes around again I will use a bigger scope. . . 

[Jon Isaacs]

Eyepieces like these are mostly useful for double stars.  Besides the NP-101, I use my 3.5 mm with a 2x Barlow in my 10 inch Dob. With the Paracorr, it provides 821x, useful for splitting doubles.  Last night I was using my 10 inch with my TMB Planetary eyepieces.  Lambda Cygni is currently at 0.92 arc-seconds and I was able to get a beautiful split complete with the unique diffraction pattern a close double provides using the 4mm with a 2x barlow, that was 621x, the split was visible at 300x and lower but it was so perfect at 600x... 

 

Just my two cents.

 

Jon

[Max Power]

2.5mm Nagler type 6, bought one to try to keep Mars in view as it moved away.  Worked good at 400x in my 8" f/5 dob.  The extra field of view is nice at extreme powers, much better than Nagler 2-4 zoom, but about the same optical quality.

 

Worth having if you got room in your eyepiece case, though little used.

[Sarkikos]

I have a 2.5 T6 that I bought used.  Is there any other eyepiece out there at 2.5mm, TeleVue quality and with an 82 degree AFOV?  I've used it to view planets through my 10" f/4.8 Dob. 480x, 49x per inch, 0.5mm exit pupil.  Nice view, especially for scopes that don't track. I don't think I'll be selling this one.

 

Mike

[allen g]

thanks for feedback it has been helpful but I another thought.  This pertains to use in my TV NP-101 (4" apo - visual use only).  I have the 10 ethos, 8 & 6 delos so when barlowed (2x) I then have 5, 4, 3mm.  Instead of the 2.5mm what about a 4.5 delos and then with a barlow could end up with 240x. Does this make any sense as the 4.5 would be used quite a bit but I wonder if 240x is of any use with this scope (it is the upper limit).  What are your thoughts about the eye relief on the 2.5 has that been an issue.  again your feedback is appreciated.  

[Max Power]

The extra lenses of a barlow degrade the images slightly.

 

Stay with the higher priced ones, celestron ultima at a minimum.

 

I have the Baader 2.25x that I use with zooms, seems to be ok.

[Jon Isaacs]

thanks for feedback it has been helpful but I another thought.  This pertains to use in my TV NP-101 (4" apo - visual use only).  I have the 10 ethos, 8 & 6 delos so when barlowed (2x) I then have 5, 4, 3mm.  Instead of the 2.5mm what about a 4.5 delos and then with a barlow could end up with 240x. Does this make any sense as the 4.5 would be used quite a bit but I wonder if 240x is of any use with this scope (it is the upper limit).  What are your thoughts about the eye relief on the 2.5 has that been an issue.  again your feedback is appreciated.  

 

Whether or not 240x is worthwhile depends on you, the objects you choose and the conditions you face.  Me, I like splitting close double stars, the seeing here is quite good and often allows me to split sub-arcsecond doubles (in larger scopes) so I find a Barlowed 3.5 Nagler at about 310X quite useful.  

 

Jon

[allen g]

I have the tele Vue 2x barlow which is of good quality like all their equipment. Think I have decided on the 2.5 as I will get more use from it relative to using a barlow on a 4.5 delos and it delivers a larger field. I don't use a motorized mount - I have theNP-101 on the DM4 DiscMount which is truly exceptional. The purpose of the 2.5 would just be for splitting stars and viewing planets on a good eve. thanks for the helpful feedback. allen

[John F]

thanks for feedback it has been helpful but I another thought.  This pertains to use in my TV NP-101 (4" apo - visual use only).  I have the 10 ethos, 8 & 6 delos so when barlowed (2x) I then have 5, 4, 3mm.  Instead of the 2.5mm what about a 4.5 delos and then with a barlow could end up with 240x. Does this make any sense as the 4.5 would be used quite a bit but I wonder if 240x is of any use with this scope (it is the upper limit).  What are your thoughts about the eye relief on the 2.5 has that been an issue.  again your feedback is appreciated.  

 

Another option would be to get a 5mm Nagler instead of a 2.5mm Nagler.  With your 2x Barlow the 5mm Nagler would give you 216x and without the Barlow.  When used alone it would also enable you to get the 5mm Focal length without having to use any Barlow at all.  However, as I stated in my previous post, when observing at really high powers (and consequently with very small true fields) it makes observing easier if you don't have to use a Barlow at all in conjunction with your eyepiece and the 2.5mm Nagler nicely covers that base for owners for fast/short focal length refractors like the NP101 & NP127.  Also, because seeing conditions are rarely perfect you will probably find that you can use the scope at 216x and still get a good image on more nights that you'll be able to use it at 240x. 

 

I'd go with the 2.5mm Nagler now and later when you've got some money to burn and urge to further upgrade your scope system I'd add a 4.5mm Delos, a 3.5mm Delos, and a 3mm Radian eyepiece and sell the 2x Barlow.  Then the 6mm Delos would give you 90x, the 4.5mm 120x, the 3.5mm 154x, the 3mm Radian 180x and the 2.5mm Nagler 216x. 

 

John Finnan

[Sarkikos]

... or just get a nice zoom and a Barlow! Or maybe the Nag 3-6 and 2-4 Zooms.

 

Mike

Edited by Sarkikos, 03 October 2014 - 07:24 AM.

[FirstSight]

... or just get a nice zoom and a Barlow! Or maybe the Nag 3-6 and 2-4 Zooms.

 

Mike

 

It's a good thing to mention this option for the OP to consider.  However, while Zoom EPs (including the aforementioned Televue Nagler zooms) are to some observers versatile magic to have in their EP collection, to many others, they are not attractively suitable to their taste.  For one thing, the TV Nagler zooms are 50 deg AFOV EPs rather than 70 or 82 and the view can seem soda-straw constricted to those who prefer a wider-field (I'm in this camp).  This divide over the suitability of zooms is analogous to the divide that exists in different people's tastes regarding 70 deg AFOV EPs vs ultra-wides (the 82s and 100 deg AFOV EPSs) - as someone who enthusiastically appreciates both the objective benefits of 100 deg AFOV EPs (objects stay in FOV longer in untracked scopes, more TFOV/smaller exit pupil at any given magnification etc) and their subjective sense of nearly unbounded "spacewalk immersiveness", the complaints of folks who find more discomfort than benefit past 70 deg AFOV seem frankly baffling (unless they walk around all day with blinders restricting them to 70 degrees) - but in the end I simply have to respect the principle "different strokes for different folks", accept that ultra-widefield EPs simply don't work well for everyone's tastes, and leave it at that.

 

Maybe the OP is among those susceptible to the charms of Nagler zooms, or maybe he isn't at all.  Nevertheless, it's an option worth laying out on the table.

[allen g]

Well I purchased the 2.5 nagler on Saturday and had a chance to use it last night in my TV NP-101. Wow, what an EP. I put it on Epsilon in Lyra and the split was magnificent. The contrast was excellent - the background coal black - all 4 stars were vividly seen better than ever - 4 perfect white circles. With 82 degrees can see all four close up at 216x. I also viewed the double star WZ Cassiopeia (one is a carbon) and that was also a beautiful sight as the carbon is red which looked terrific against the high contrast background. Wonderful first light with this EP.

[lionel]

My 2.5T6 comes in handy when the seeing is above average. I use it mostly for splitting close doubles and viewing Mars and Saturn at 360x in my 5" refractor.  It also performs well in my 16" dob on those rare nights when I can use 785x to examine the shell structure of a planetary nebula.

 

Lionel

[allen g]

If conditions and the scope can handle high power EPs, they are certainly worth owning. My first light with it was very satisfying and I am very happy it made the purchase. It is perfect for splitting stars.