ICEINSPACE
Most Read Articles
Moon Phase
CURRENT MOON Waxing Crescent
22%
The Sun Now
Time Zones
Sydney*
1:44 am
Perth
10:44 pm
Auckland*
3:44 am
New York
9:44 am
Paris
3:44 pm
GMT
2:44 pm




Go Back   IceInSpace > Equipment > Eyepieces, Barlows and Filters

Reply
 
Thread Tools Rate Thread
  #1  
Old 16-11-2016, 01:28 PM
Profiler (Profiler)
Registered User

Profiler is offline
 
Join Date: Feb 2009
Location: Sydney
Posts: 1,172
Pentax XW 14mm vs. Televue Delos 14mm - Design Flaw?

I am hoping this is a fairly easy question to answer.

From what I have read the 14mm Pentax XW eyepiece seems to suffer from one reasonably significant design flaw in terms of FC when it is used in a fast Newt (f5 or less) without some type of corrector such as a Televue Parracor etc.

Consequently, my question is (which I hope is simple to answer):-

Does the 14mm Televue Delos also feature the same problems with FC??

OR

Did the folks at Televue utilise some type of different design so the 14mm Delos does not demonstrate the same problems with FC akin to the 14mm Pentax XW

My thanks in advance to whomever can offer some answers on this point.
Reply With Quote
  #2  
Old 16-11-2016, 03:02 PM
AG Hybrid's Avatar
AG Hybrid (Adrian)
A Friendly Nyctophiliac

AG Hybrid is offline
 
Join Date: Nov 2009
Location: Toongabbie, NSW
Posts: 1,440
No it doesn't. The Delos is corrected in my F5 12" with a beautiful flat field that has pin point to the very edge. IIRC the 14mm> were designed to be used in Pentax Spotting scopes for day time use, thus making and FC either void due to the spotting scopes lense design and/or you cant see it evidently during the day.
Reply With Quote
  #3  
Old 16-11-2016, 10:10 PM
Wavytone
Fringe Lunatic

Wavytone is offline
 
Join Date: Jul 2008
Location: Killara, Sydney
Posts: 2,516
In short:

- if you are using a fast dob, buy Televue.

- if you are using an SCT, Mak or refractor, Pentax, Nikon or Vixen eyepieces may be better.

- if you have a real flat-field scope (i.e. quadruplet ED APO or other esoteric expensive beast) then yes, you should buy flat-field eyepieces if you intend to use this visually.

As for the ES, GSO or cheapie clone eyepieces don't ask I have no idea and you will be taking pot luck IMHO.

Unfortunately eyepiece manufacturers won't state is the field curvature of the eyepiece, and whether it has a modest amount of coma built-in. However, over the years a few points have become abundantly clear:

Most japanese eyepieces (including Pentax, Vixen, Nikon, Masuyama and circle-V) are designed to match refractors, the most popular scopes sold in Japan being around 100mm f/7 give or take 20mm aperture. This means the eyepieces have curved focal planes around 1-2m radius, CONCAVE towards the sky.

Televue officially sits on the fence and says nothing either way. But personal testing suggests all Televue eyepieces include field curvature and some degree of modest coma correction to suit fast newtonians f/4...f/5 typical of the big dobsonians popular in the USA.

Note that the field curvature of refractors is opposite to that of newtonians. Hence eyepieces that suit one won't be a great match for the other.

A few eyepieces appear to have some compensation for coma by design (i.e. negative coma). Vixen has used careful wording which indicates some of its recent eyepieces have some form of compensation for coma, and the behaviour of their LVW eyepieces in fast newtonians does indicate the LVWs certainly do.

There is one exception to the above: The recent advent of fast flat-field refractors used for "imaging" (dreadful word, the correct word is "photography", I suggest) has resulted in the production of a a few flat-field eyepieces to match. These are invariably very clearly marked FLAT FIELD to distinguish them from the rest (which aren't). And yes, I am an owner of a flat-field APO scope.

Last edited by Wavytone; 16-11-2016 at 10:42 PM.
Reply With Quote
  #4  
Old 17-11-2016, 10:17 AM
ausastronomer (John Bambury)
Registered User

ausastronomer is offline
 
Join Date: Mar 2005
Location: Shoalhaven Heads, NSW
Posts: 2,397
Quote:
Originally Posted by Wavytone View Post
In short:

- if you are using a fast dob, buy Televue.

- if you are using an SCT, Mak or refractor, Pentax, Nikon or Vixen eyepieces may be better.

- if you have a real flat-field scope (i.e. quadruplet ED APO or other esoteric expensive beast) then yes, you should buy flat-field eyepieces if you intend to use this visually.

As for the ES, GSO or cheapie clone eyepieces don't ask I have no idea and you will be taking pot luck IMHO.

Unfortunately eyepiece manufacturers won't state is the field curvature of the eyepiece, and whether it has a modest amount of coma built-in. However, over the years a few points have become abundantly clear:

Most japanese eyepieces (including Pentax, Vixen, Nikon, Masuyama and circle-V) are designed to match refractors, the most popular scopes sold in Japan being around 100mm f/7 give or take 20mm aperture. This means the eyepieces have curved focal planes around 1-2m radius, CONCAVE towards the sky.

Televue officially sits on the fence and says nothing either way. But personal testing suggests all Televue eyepieces include field curvature and some degree of modest coma correction to suit fast newtonians f/4...f/5 typical of the big dobsonians popular in the USA.

Note that the field curvature of refractors is opposite to that of newtonians. Hence eyepieces that suit one won't be a great match for the other.

A few eyepieces appear to have some compensation for coma by design (i.e. negative coma). Vixen has used careful wording which indicates some of its recent eyepieces have some form of compensation for coma, and the behaviour of their LVW eyepieces in fast newtonians does indicate the LVWs certainly do.

There is one exception to the above: The recent advent of fast flat-field refractors used for "imaging" (dreadful word, the correct word is "photography", I suggest) has resulted in the production of a a few flat-field eyepieces to match. These are invariably very clearly marked FLAT FIELD to distinguish them from the rest (which aren't). And yes, I am an owner of a flat-field APO scope.

Quote:
Originally Posted by Wavytone View Post
In short:

- if you are using a fast dob, buy Televue.
That's not necessarily correct. I have been using large fast newtonians for a very long time and there are a lot of eyepieces that perform exceptionally well in these scopes besides Televue. For instance the 3.5mm, 5mm, 7mm and 10mm Pentax XW's. These all have inherent negative field curvature which off sets the very small amount of positive field curvature of a large fast newtonian telescope.

The 12.5mm Docter and all of the Nikon NAV HW's work very well in large fast Newtonians. There are plenty of other eyepieces that also work very well, including the 14mm Denkmeier.

The field curvature in a large fast newtonian (from the telescope itself) is very minimal and it's almost flat field, as the field curvature is a function of the radius of curvature (focal length) of the primary optic which is long. Usually much longer than the radius of curvature of a refractor, or catadioptic scope. Irrespective of the sign of the field curvature with a newtonian it doesn't matter all that much because it's small. Where it can matter is when the field curvature of the eyepiece is the same sign and compounds the observed field curvature, as is the case with the 14mm and 20mm Pentax XW's. Both of which I own. Both of which work beautifully in a fast newtonian when used with a paracorr, which is what you should be doing in any newtonian faster than F5.

The field curvature of the telescope is not related to the F-ratio of the telescope. Coma is directly related to the F-ratio of the telescope. For newtonians F5 and faster and maybe even F5.5 and faster, you should use a paracorr. A lot of people don't notice coma with F5.5 to F5 telescopes when not using a Paracorr and think the view is great. However, as soon as you insert a paracorr, the improvement becomes blatantly obvious. In many cases dim threshhold stars near the edge of the field become much more visible due to the reduction in spot size and the fact the light is concentrated into a smaller point.

Quote:
Originally Posted by Wavytone View Post
Unfortunately eyepiece manufacturers won't state is the field curvature of the eyepiece
The field curvature and astigmatism graphs and data have been readily available for all of the Pentax XW eyepieces for well over a decade. As have the lens configuration diagrams and the light transmission data. See attachments below. You just need to know where to look.

Quote:
Originally Posted by Wavytone View Post
Most japanese eyepieces (including Pentax, Vixen, Nikon, Masuyama and circle-V) are designed to match refractors
If this statement was true then all of the Pentax XW eyepieces would have field curvature of the same sign. But they don't. As per the graph below 4 of the Pentax XW's 3.5mm, 5mm, 7mm and 10mm all have negative field curvature and the other four, 14mm, 20mm, 30mm and 40mm have positive field curvature.

Quote:
Originally Posted by Wavytone View Post
Televue officially sits on the fence and says nothing either way. But personal testing suggests all Televue eyepieces include field curvature and some degree of modest coma correction to suit fast newtonians f/4...f/5 typical of the big dobsonians popular in the USA.
If this statement was correct from what you have alluded to right throughout your entire post, then Televue eyepieces wouldn't work well in their own refractors. But the truth is all of their eyepieces work very well in their own refractors. Do you seriously think Televue are going to design and sell eyepieces that don't work well in their own telescopes?

Quote:
Originally Posted by Wavytone View Post
Note that the field curvature of refractors is opposite to that of newtonians. Hence eyepieces that suit one won't be a great match for the other.
This is not correct. The short focal length Pentax XW's (3.5mm, 5mm, 7mm and 10mm) and just about every single Televue eyepiece and a large number of others including the 12.5mm Docter and both of the Nikon NAV HW's (17mm/14mm and the 12.5mm/10mm) work very well in both fast newtonians and fast refractors. You can also add the 14mm Denkmeier to that list. There are also plenty of others.

To be honest I think you have it wrong in your assessment of the design objectives and parameters of the eyepiece manufacturers. For certain if your assumption was correct all of the Pentax XW's would have field curvature of the same sign and they don't. Half have +ve field curvature and half have -ve field curvature.

Cheers,
John B
Attached Thumbnails
Click for full-size image (Pentax XW field curavture and astigmatism graphs.gif)
15.3 KB48 views
Click for full-size image (Pentax XW lens configuration diagrams.gif)
33.0 KB49 views
Click for full-size image (Pentax light transmission graphs.gif)
16.5 KB42 views
Reply With Quote
  #5  
Old 17-11-2016, 10:41 AM
ausastronomer (John Bambury)
Registered User

ausastronomer is offline
 
Join Date: Mar 2005
Location: Shoalhaven Heads, NSW
Posts: 2,397
Quote:
Originally Posted by Profiler View Post
I am hoping this is a fairly easy question to answer.

From what I have read the 14mm Pentax XW eyepiece seems to suffer from one reasonably significant design flaw in terms of FC when it is used in a fast Newt (f5 or less) without some type of corrector such as a Televue Parracor etc.

Consequently, my question is (which I hope is simple to answer):-

Does the 14mm Televue Delos also feature the same problems with FC??

OR

Did the folks at Televue utilise some type of different design so the 14mm Delos does not demonstrate the same problems with FC akin to the 14mm Pentax XW

My thanks in advance to whomever can offer some answers on this point.
Hi Profiler,

It's not a design flaw. It is simply not possible to correct for all aberrations at the same time with any eyepiece design and it comes back to what aberrations the eyepiece designer has chosen to correct best and which aberrations he has compromised. In other words you can't correct for eyepiece coma (different to coma from the telescope), field curvature, astigmatism, angular magnification distortion and rectilinear distortion at the same time. What becomes more difficult to correct and how bad it is then becomes a balancing act and this is further affected by the eyepiece focal length and the desired eye relief. Generally Televue eyepieces are generally well corrected for angular magnification distortion and not so well corrected for rectilinear distortion (the Nagler type 4's are the exception). Pentax eyepieces because of their intended use in spotting scopes are well corrected for rectilinear distortion. If you use a Televue eyepiece (not a type 4) in a spotting scope you will find that the walls of buildings are curved not straight and the waterline of a ship at sea has a significant "bow" in it. Pentax XW's on the other hand will give straight walls and a straight waterline.

The truth is and the easy answer is in any fast newtonian you should be using a paracorr. When combined with a paracorr in a fast newtonian the 14mm and 20mm Pentax XW's perform beautifully and give excellent flat field views. The type 4 Naglers because of their design paramaters also benefit immensely by being used with a paracorr in any newtonian faster than F6.

In answer to your question the 14mm Delos will give a flatter field view than the 14mm Pentax XW when used in a newtonian faster than F5.5 or so. However you should be using a paracorr in that telescope as the view in both eyepieces will be noticeable improved by its use. When used with a paracorr both eyepieces perform as well as each other.
Note that the 14mm Delos "may" require a special adaptor to reach focus, as it needs a lot of focuser in travel, as does the 17mm Delos.

Cheers,
John B
Reply With Quote
  #6  
Old 17-11-2016, 12:36 PM
Profiler (Profiler)
Registered User

Profiler is offline
 
Join Date: Feb 2009
Location: Sydney
Posts: 1,172
Thank you Wavytone and Ausastronomer

You have both provided me with a wealth of information.

From my perspective I am trying to pick a good eyepiece that will work well in my 80mm refractor AND - hopefully - won't be too shabby in a Dob as well.

I am not sold on the Pentax/Delos/LVW EPs as I prefer to avoid their big ergonomics (i.e. I like my EPs smaller where possible) but I do indeed like the ER they all offer.

I am really trying to decide what might be the best option amongst

Nagler T5 16mm

Nagler T6 13mm

Vixen SSW 14mm

Initially, the 16mm T5 Nagler seems to tick all boxes with one main fault - it has very limited ER of only 10mm

The 13mm T6 is about the same but the fov is little smaller but this is offset with 2mm extra of ER - so hopefully a bit more comfortable

The 14mm Vixen SSW seems perfect in terms of 13mm ER, good fov, great japanese glass from Vixen etc but no one seems to be able comment on how well they perform in Dobs etc. Indeed, I read one discouraging review which indicated that the outer 10% has significant astigmatisim.

So - in summary - I am stuck and really not certain what is the best option which led me full circle to consider the 14mm Delos but then I remembered the issues with the Pentax 14mm XW and hence why I started this thread with my question about the Delos

PS
DeLites seem to lack fov which I crave

Last edited by Profiler; 17-11-2016 at 08:59 PM.
Reply With Quote
  #7  
Old 17-11-2016, 01:00 PM
Profiler (Profiler)
Registered User

Profiler is offline
 
Join Date: Feb 2009
Location: Sydney
Posts: 1,172
On a perhaps unrelated point - can anyone explain what is/are the design/performance differences/purpose between the Televue Nagler T5 range and the Televue T6 range of Nagler eyepieces?

Asides from the obvious size differences between a 31mm T5 Terminagler and a tiny 13mm T6 Nagler - is there anything else specific to these differing designs?

I suppose I am really trying to understand what is the differences (other than 3mm) between the 1.25 13mm T6 Nagler and the 16mm T5 Nagler
Reply With Quote
  #8  
Old 18-11-2016, 02:55 PM
Don Pensack's Avatar
Don Pensack
Registered User

Don Pensack is offline
 
Join Date: Aug 2006
Location: Los Angeles
Posts: 337
I cannot speak for every single brand and model of eyepiece, but I can state that *nearly* every modern eyepiece (including all brands mentioned on this thread) is completely corrected for inherent coma (which does not mean you will not see coma, merely that it will not come from the eyepiece), and the only commonly marketed coma-correcting eyepieces that were sold were the Praetorias, and they haven't been produced for decades.
Understand that any such eyepiece would be unusable in any scope except a newtonian, so no manufacturer is going to do that.

As for field curvature, that is a "horse of a different color", i.e. there are significant field curvatures to be found in many eyepieces. And it is entirely possible that that field curvature could be of the same sign as the telescope, and therefore additive, making a field curvature visible that might be, on its own for each, far less visible.

The Nagler T5 line was scaled. That means that eye relief was a set percentage of the focal length, and also making the eyepieces scale in size. Ergo, the 16mm has 16/31 the eye relief of the 31mm and represents about the smallest eyepiece possible in that series.

To create a line of shorter focal length Naglers required keeping eye relief long enough all the way down to a 2.5mm focal length,which meant a design with constant eye relief in all focal lengths was the easiest way to design a series. They are small to be usable in small scopes and to allow easy binoviewing.
Ironically, the 16mm T5 Nagler has less eye relief (by 2mm) than the T6 Series.

Current production Naglers are the:
31mm T5--long enough eye relief for glasses
22mm T4 Nagler--ditto
17mm T4 Nagler--ditto
16mm T5 Nagler--very short eye relief
13mm T6 Nagler--small form, medium short eye relief (not glasses friendly)
12mm T4 Nagler--longer eye relief like the 17mm
11mm, 9mm, 7mm, 5mm, 3.5mm, 2.5mm T6 Naglers--identical form and eye relief to the 13mm

The 26mm T5 and 20mm T5 are no longer in production.
Reply With Quote
  #9  
Old 19-11-2016, 10:02 AM
ausastronomer (John Bambury)
Registered User

ausastronomer is offline
 
Join Date: Mar 2005
Location: Shoalhaven Heads, NSW
Posts: 2,397
Quote:
Originally Posted by Profiler View Post
Thank you Wavytone and Ausastronomer

You have both provided me with a wealth of information.

From my perspective I am trying to pick a good eyepiece that will work well in my 80mm refractor AND - hopefully - won't be too shabby in a Dob as well.

I am not sold on the Pentax/Delos/LVW EPs as I prefer to avoid their big ergonomics (i.e. I like my EPs smaller where possible) but I do indeed like the ER they all offer.

I am really trying to decide what might be the best option amongst

Nagler T5 16mm

Nagler T6 13mm

Vixen SSW 14mm

Initially, the 16mm T5 Nagler seems to tick all boxes with one main fault - it has very limited ER of only 10mm

The 13mm T6 is about the same but the fov is little smaller but this is offset with 2mm extra of ER - so hopefully a bit more comfortable

The 14mm Vixen SSW seems perfect in terms of 13mm ER, good fov, great japanese glass from Vixen etc but no one seems to be able comment on how well they perform in Dobs etc. Indeed, I read one discouraging review which indicated that the outer 10% has significant astigmatisim.

So - in summary - I am stuck and really not certain what is the best option which led me full circle to consider the 14mm Delos but then I remembered the issues with the Pentax 14mm XW and hence why I started this thread with my question about the Delos

PS
DeLites seem to lack fov which I crave
I would avoid the 16mm Nagler T5 at all costs. While the specifications state it's eye relief at 10mm, the "useable" eye relief is somewhat less than this. It isn't a comfortable eyepiece to use in any way shape or form, notwithstanding that it is pretty good optically.

The 13mm Nagler T6 is a pretty bulletproof eyepiece, if you can handle the eye relief, which is too short for me and to use with glasses on, but noticeably better than the 16mm T5. The eye relief on Televue eyepieces is measured from the top of the eye lens. This means that depending on the design of the housing and the eyecup the "useable" eye relief on a lot of the Televue eyepieces can be somewhat less than the stated eye relief. Just be aware of this. With eyepieces having a wide eye lens and a screw down eyeguard (eg Pentax XW, TV Radian and TV Delos) you get to use all of the 20mm of stated eye relief.

The 13mm Nagler T6 will work very well in both your dob and your refractor. Optically it is very good but I rate it marginally behind both the 14mm Pentax XW and the 14mm Delos in terms of sharpness, contrast and light throughput, but it is high quality. It also has a very nice compact form factor.

Also consider the 14mm Denkmeier. It's stated FOV is 65 degrees but it is actually closer to 70 degrees, possibly due to the AFOV being 67 or 68 degrees and the true focal length being 14 and a fraction. It is a very high quality eyepiece in every respect and it will give an excellent flat field view in both your newtonian and your refractor. It has 20mm of eye relief and a slightly smaller form factor than the 14mm Delos and Pentax XW's, but it is still somewhat larger than the 13mm Nagler T6.

Knowing what I know and having used all the contenders on numerous occasions if you want a slightly smaller form factor than the Delos and XW's with good eye relief and high quality optics I would be looking really long and hard at the 14mm Denkmeier.

Here is a review worth reading

Of course for $1,000 plus, the 12.5mm Docter will solve all your problems It gets no better than the Docter.

Cheers,
John B
Reply With Quote
  #10  
Old 19-11-2016, 12:33 PM
Profiler (Profiler)
Registered User

Profiler is offline
 
Join Date: Feb 2009
Location: Sydney
Posts: 1,172
Thank you for the excellent advice!!!

Alas, I am probably old fashioned but I can't seem to justify an eyepiece such as the Docter which is worth more than the whole telescope

I am glad to get some feedback about the 16mm Nagler and I now know it is not the eyepiece I need.

The Denk sounds good!

Last edited by Profiler; 19-11-2016 at 05:38 PM.
Reply With Quote
  #11  
Old 19-11-2016, 09:26 PM
MortonH's Avatar
MortonH
Deprived of starlight

MortonH is offline
 
Join Date: Nov 2006
Location: Sydney
Posts: 2,940
The 14mm Delos is the best eyepiece I've owned around that focal length. When I say "best" I'm not talking about rigorous testing but it gave awesome views in all my scopes and was very comfortable to use. It's like a Pentax XW 14mm without the FC.
Reply With Quote
  #12  
Old 20-11-2016, 06:21 AM
Larryp's Avatar
Larryp (Laurie)
Registered User

Larryp is offline
 
Join Date: Apr 2012
Location: Sydney
Posts: 5,244
I guess we all have different tastes, but the 16mm Nagler type 5 is my very favourite eyepiece. But I never have liked eyepieces with long eye relief.
Reply With Quote
  #13  
Old 20-11-2016, 05:42 PM
Allan's Avatar
Allan
Registered User

Allan is offline
 
Join Date: Feb 2013
Location: Newcastle
Posts: 776
Quote:
Originally Posted by Profiler View Post
Alas, I am probably old fashioned but I can't seem to justify an eyepiece such as the Docter which is worth more than the whole telescope
Well, I can see where you're going wrong then, you need to buy more expensive telescopes.

The Docter is very good, I have one for each eye. They are a great size, and ergonomically suited to Bino viewing. The Ethos and Delos perform equally as well, but the Delos is the finest range of eyepieces TV have ever produced.

Having owned or used all the eyepiece's you're considering I would steer you toward the 14 Delos, but the 13 Nagler is a good option if you are really that concerned about the size factor of the Delos.
Reply With Quote
  #14  
Old 08-01-2017, 04:45 PM
GrahamL's Avatar
GrahamL
pro lumen

GrahamL is offline
 
Join Date: Jun 2006
Location: ballina
Posts: 2,840
I've owned the 16 t6,13t6,14 xw

The 16 is /was a great eyepiece really flat in my 12"5 but the eye relief is very tight sold it at a fair loss as I rarely reached for it in time ,The 13 t6
is a nice piece of glass ,small ,compact and that wide view .Not long after I bought the 13 I had the opportunity to compare it to a 14 xw , no paracor , I had owned a pretoria for a number of years then , I guess its down to personal preferences a lot of the time and for me at that time I instantly thought the 14 was the better of the two , still remember that sinking feeling I'd backed the wrong horse


what did u buy ?
Reply With Quote
  #15  
Old 09-01-2017, 01:15 AM
Don Pensack's Avatar
Don Pensack
Registered User

Don Pensack is offline
 
Join Date: Aug 2006
Location: Los Angeles
Posts: 337
A wider apparent field will always show more coma. If you had used both with a coma corrector, you might have had a different comment.
Both are excellent, but one has a considerably narrower apparent field.
On the other hand, if eye relief made a difference, finding a long eye relief 82 eyepiece would have proved difficult.
Reply With Quote
  #16  
Old 09-01-2017, 05:15 AM
wavelandscott's Avatar
wavelandscott (Scott)
Plays well with others!

wavelandscott is offline
 
Join Date: Nov 2004
Location: Ridgefield CT USA
Posts: 3,183
Quote:
Originally Posted by Larryp View Post
I guess we all have different tastes, but the 16mm Nagler type 5 is my very favourite eyepiece. But I never have liked eyepieces with long eye relief.
I agree...while it is not everyone's cup of tea because of the very short eye relief (and I do find I must "jam my eye into it") I find the views spectacular and it is one of my favorites...very short eye relief being acceptable.

I also enjoy the Pentax 7 and 10 mm and the Denkmeier 14 and 21...which all have long eye relief. The Denks are a hidden gem.
Reply With Quote
  #17  
Old 31-03-2017, 04:21 AM
Waxing_Gibbous's Avatar
Waxing_Gibbous (Peter)
Grumpy Old Man-Child

Waxing_Gibbous is offline
 
Join Date: Jul 2009
Location: South Gippsland
Posts: 1,754
Quote:
Originally Posted by Larryp View Post
I guess we all have different tastes, but the 16mm Nagler type 5 is my very favourite eyepiece. But I never have liked eyepieces with long eye relief.
Couldn't agree more.
A top performer in any scope. Also consider the 19mm Panoptic. Same FoV as the 16 Nag. but shows nebulosity better. My fave for M45, it also seems to suffer no FC at all!
Reply With Quote
  #18  
Old 31-03-2017, 08:41 AM
astro744
Registered User

astro744 is offline
 
Join Date: Apr 2007
Posts: 670
I use a 16mm T5 Nagler a lot in mono and bino mode. I don't find the eye relief to be a problem at all but I also tend to observe with eye cups folded down on all my eyepieces; just prefer it that way and as my viewing surrounds are quite dark I can do without the eye guard.

Note the volcano top form factor of the 16NT5 does allow you to get your eye closer.
Reply With Quote
Reply

Bookmarks

Thread Tools
Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT +10. The time is now 12:44 AM.

Powered by vBulletin Version 3.8.7 | Copyright ©2000 - 2017, Jelsoft Enterprises Ltd.
Advertisement
Lunatico Astronomical
Advertisement
SkyWatcher Star Discovery
Advertisement
Bintel
Advertisement
OzScopes Authorised Dealer
Advertisement
Tasco Australia
Advertisement
FLI Cameras and Imaging Accessories
Advertisement
Atik 16200
Advertisement
Meade Instruments
Advertisement
NexDome Observatories
Advertisement
Astronomy and Electronics Centre
Advertisement