EP for widest tfov in 12" LX90

[Paul-F]

What ep will give me the widest practical tfov with good contrast in my 12" LX90 without vignetting or showing other issues.

[John]

The Vixen NLVW 42mm has the largest AFoV of any 2" eyepiece I believe - 72 degrees. The Nagler 31mm delivers 82 degrees so nearly as much sky and the additional magnification over the 42mm NLVW would would increase the contrast of faint objects in many scopes - not sure if that applies to a 12" F/10 though.

[michael.h.f.wilkinson]

As it is the exit pupil that determines the brightness of the background, eyepieces will perform much the same in the Mr. Spock's C9.25 (who waxes lyrical about the Vixen 42), my C8 and the Meade 12" SCT, because all are F/10. The Vixen LVW 42 has a 72 deg aFOV, at a 4.2 mm exit pupil (still very usable). As I said in another thread, I tend to use the Nagler 31T5 more than my 40mm Paragon, simply because the 3.1mm exit pupil gives a darker background. Only for a few objects do I prefer the 40mm. I must really consider selling the 40mm, but for now I am keeping it.

[Merlin66]

I find the 32mm the most used eyepiece. Your choice of make, model, brand....

[michael.h.f.wilkinson]

The ES 30mm 82 deg has a good rep as well. I was planning to buy that when the Nagler 31T5 popped up secondhand.

[ollypenrice]

Although the 31 Nagler has an awesome field I found it slightly tricky to use, with blackout effects arising for me in the 10 inch SCT. I found the 35 Panoptic more comfortable on balance. This probably varies person to person though. I now have a 26 Nagler which obviously doesn't compete on field but is very easy on the eye. (Well, mine...)

Olly

[michael.h.f.wilkinson]

I personally have no black-out problems with my 31T5 in my 8" SCT (although I was worried about that after Olly's words of warning). In a faster reflector the central obstruction can cause trouble in all long EPs, but the F/10s seem pretty immune. Best thing may be to check these EPs out before buying.

[damnut]

The easiest on my eye in my 10"Lx is a Moonfish 30mm.

[Mr Spock]

The LVW 42mm is certainly a strong performer, great for open clusters. No blackout problems like a Nagler, though if you try to get your eye too close you can start to see the baffle tube. Like all LVWs it's really comfortable to use.

[Paul-F]

I do have a 2" 38mm 70 degree Adler as my widefield (relatively speaking of course ) but the images are not the best with bad edge correction and bad contrast on bright nights specially with the moon like it is now - this gives a tfov of .87 by my reckoning. If I can get an ep for near on 1 degree (eg .99 for the 42mm) and improve contrast then I will buy it and flog the 38mm ...

The LVW 42mm has my interest right now ...

[cs1cjc]

It is the field stop that limits the true field of view. You are not going to get much wider than your current 38mm, but I am sure you can better edge correction. At F/10, exit pupil is not going to be an issue, so a long focal length is fine. Some wide field contenders and their field stop diameters (with source) include:

35mm Panoptic 38.7mm (Tele Vue)

31mm Nagler 42.0mm (Tele Vue)

36mm Hyperion 44.0mm (David Knisely)

38mm Adler Skarp 45.2mm (my direct measurement)

40mm Aero 45.7mm (TMB Paragon figure, TS say 47mm)

41mm Panoptic 46.0mm (Tele Vue)

40mm Pentax XW 46.5mm (Pentax)

42mm Vixen NLVW 47mm (*Revised* thanks to michael.h.f.wilkinson below, from njopsahl.no - Vixen LVW 42mm 2")

[michael.h.f.wilkinson]

It is the field stop that limits the true field of view. You are not going to get much wider than your current 38mm but I am sure you can better edge correction. At F/10 the exit pupil is not going to be an issue so a long focal length is fine. Some contenders and their field stop diameters include:

35mm Panoptic 38.7mm (Tele Vue)

31mm Nagler 42.0mm (Tele Vue)

36mm Hyperion 44.0mm (David Knisely)

38mm Adler Skarp 45.2mm (my direct measurement)

40mm Aero 45.7mm (TMB Paragon figure, TS say 47mm)

41mm Panoptic 46.0mm (Tele Vue)

40mm Pentax XW 46.5mm (Pentax)

42mm Vixen 50mm?? (based on the review on First Light Optics site)

I got a figure of 47mm for the Vixen 42 LVW on a Norwegian site.

njopsahl.no - Vixen LVW 42mm 2"

This may or may not be accurate. What may be the case is that pincushion distortion leads to a difference between apparent field of view (AFOV) and true apparent FOV (TAFOV). For more details see

http://stargazerslounge.com/discussions-eyepieces/166605-aparent-fov-vs-true-aparent-fov-max-true-fov-sct.html

[cs1cjc]

I got a figure of 47mm for the Vixen 42 LVW on a Norwegian site.

njopsahl.no - Vixen LVW 42mm 2"

...

Yes, that sounds much more likely!

[michael.h.f.wilkinson]

I am actually pondering selling my Paragon 40mm. I just seem to be using the 31T5 which is an amazing EP.

[Paul-F]

It is the field stop that limits the true field of view. You are not going to get much wider than your current 38mm, but I am sure you can better edge correction. At F/10, exit pupil is not going to be an issue, so a long focal length is fine. Some wide field contenders and their field stop diameters (with source) include:

35mm Panoptic 38.7mm (Tele Vue)

31mm Nagler 42.0mm (Tele Vue)

36mm Hyperion 44.0mm (David Knisely)

38mm Adler Skarp 45.2mm (my direct measurement)

40mm Aero 45.7mm (TMB Paragon figure, TS say 47mm)

41mm Panoptic 46.0mm (Tele Vue)

40mm Pentax XW 46.5mm (Pentax)

42mm Vixen NLVW 47mm (*Revised* thanks to michael.h.f.wilkinson below, from njopsahl.no - Vixen LVW 42mm 2")

OK - so that is the real limiting attribute then. I don't use the 38mm much as the stars get to be unstarlike towards the edge ... not what I want to see in a 'wider field'!

Does the 42mm Vixen NLVW hold up well throughout the field?

[Mr Spock]

The only thing limiting the 42mm LVW is the abberations in your scope. With a SCT that will be coma

[Paul-F]

The only thing limiting the 42mm LVW is the abberations in your scope. With a SCT that will be coma

You make it sound like there is no point in going for that ep in order to 'improve' the view as it will be **** anyway! Well, is there really any point?

[Nexus 6]

I think the views are a are personnel thing Paul, I speak from the experience of the comments made by members of our astronomy society as well as those given here on SGL.

For me I always intended to use mine in a small frac for observing as well as the 925, still no small frac but I have tested them on a few and the views given were majestic.

Any astro society's nearby so you can try out a few before you commit to buying?

[Paul-F]

I think the views are a are personnel thing Paul, I speak from the experience of the comments made by members of our astronomy society as well as those given here on SGL.

For me I always intended to use mine in a small frac for observing as well as the 925, still no small frac but I have tested them on a few and the views given were majestic.

Any astro society's nearby so you can try out a few before you commit to buying?

I understand the personal thing - if the coma (which is possibly what I am already seeing with the 38mm) hampers performance I am wondering if I should not bother to widen the field with the LX90 at all tbh! Thinking of getting a small refractor for widefield anyway so might hold off getting a new expensive ep.

There is a club - I'll see see about trying stuff in my scope.

[Nexus 6]

There is a club - I'll see see about trying stuff in my scope.

Well I hope you get the chance to try some other options.

let us know how it goes.

[Mr Spock]

I think you misunderstand. The only limiting factor with a LVW or Nagler is the scope - they both have excellent edge correction. The eyepiece you have is a basic 5 element erfle type which has poor edge correction. Chalk and cheese.

[cs1cjc]

Is an Erfle really so bad at f/10?

[michael.h.f.wilkinson]

My Paragon 40 gives excellent views. Stars absolutely pinpoint up to 90%, with just a touch of bloat at the edges. Refocusing removes that, so it is some form of field curvature (very slight).

[kirkster501]

What about the Panoptic 41mm guys? One on ABS at the moment I was lookign at..... I am most impressed with my Pan 35....

Steve

[John]

What about the Panoptic 41mm guys? One on ABS at the moment I was lookign at..... I am most impressed with my Pan 35....

Steve

Same as the Pan 35 in terms of sharpness etc, just with a longer focal length and more bulk / weight. "Tack Sharp" was Tele Vue's promotional tag line for the Panoptics, and they are