Jump to content

  •  

CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.

Photo

What are the actual specs of the 16mm Flat Field eyepiece sold under various brands?

  • Please log in to reply
13 replies to this topic

#1 CrazyPanda

CrazyPanda

    Fly Me to the Moon

  • *****
  • topic starter
  • Posts: 5,736
  • Joined: 30 Sep 2012

Posted 24 June 2024 - 08:02 PM

I'm looking for a higher power eyepiece for my finder scope that offers roughly a 4.2 degree field of view, enough eye relief for wearing glasses, relatively light weight, and might be able to handle an F/3.75 light cone in a short achromat.

 

A contender is the 16mm Orion EF / 16mm BST Flat Field / 16mm Angeleyes / 16mm Lunt Solar Flat Field / 16mm TS Optics Flat Field. Near as I can tell, these are all the same eyepiece. However, the specifications are all over the map and I don't know what to believe.

 

16mm Orion EF: https://www.telescop...ce/p/130565.uts

  • Apparent field: 65 degrees
  • Field stop: unlisted
  • Eye relief: 18mm
  • Weight: 5 oz
  • Elements: 6

16mm BST Flat Field: https://agenaastro.c...d-eyepiece.html

  • Apparent field: 65 degrees
  • Field stop: 16.5mm
  • Eye relief: 19mm
  • Weight: 3.5 oz
  • Elements: 6

16mm Lunt Solar Flat Field: https://www.highpoin...yepiece-ls12e-1

  • Apparent Field: 60 degrees
  • Field stop: unlisted
  • Eye relief: 15mm
  • Weight: 3.7 oz
  • Elements: 5

16mm TS Optics Flat Field: https://www.astrosho...m-1-25-/p,63397

  • Apparent Field: 60 degrees
  • Field stop: 20mm
  • Eye relief: 15mm
  • Weight: 4.2 oz
  • Elements: 6

16mm Omegon Flat Field: https://www.omegon.e...#specifications

  • Apparent Field: 60 degrees
  • Field stop: unlisted
  • Eye relief: 9mm ( confused1.gif confused1.gif confused1.gif confused1.gif )
  • Weight: unlisted
  • Elements: "5 or 6"

16mm Angeleyes SWA: https://www.aliexpre...2825898530.html

  • Apparent field: 70 + 72 degrees
  • Field stop: 16.5mm ??? (listed as "distance of exit pupil" if we are to believe the 16.5mm figure from the BST Flat Field above)
  • Eye relief: unlisted (unless this really is "distance of exit pupil")
  • Weight: unlisted
  • Elements: 6

16mm Alstar Premium Flat Field: https://www.amazon.c...s/dp/B0748FN1TN

  • No useful information listed. Just lists the range of specs for the whole line.

 

Chaos. None of these agree with each other. Are there different versions of this eyepiece or something?


Edited by CrazyPanda, 24 June 2024 - 08:06 PM.


#2 CrazyPanda

CrazyPanda

    Fly Me to the Moon

  • *****
  • topic starter
  • Posts: 5,736
  • Joined: 30 Sep 2012

Posted 24 June 2024 - 08:15 PM

Sorry mods, please move to eyepieces. Was in the wrong forum when I posted this!



#3 SporadicGazer

SporadicGazer

    Viking 1

  • -----
  • Posts: 984
  • Joined: 04 Feb 2023
  • Loc: SF Bay Area, CA, USA

Posted 24 June 2024 - 08:17 PM

Have you looked them up in the Eypiece Guide Don Pensack (Starman1) so generously creates and shares with us?:

 

https://www.cloudyni...e-buyers-guide/



#4 CrazyPanda

CrazyPanda

    Fly Me to the Moon

  • *****
  • topic starter
  • Posts: 5,736
  • Joined: 30 Sep 2012

Posted 24 June 2024 - 08:40 PM

Have you looked them up in the Eypiece Guide Don Pensack (Starman1) so generously creates and shares with us?:

 

https://www.cloudyni...e-buyers-guide/

Yes. Don's information is sourced from the same listings I'm looking at and has similar discrepancies, though he seems to have transposed the specs of some variants onto the others.

 

16-flat-field.JPG

 

But since the manufacturer specs seem to be all over the place in the various listings for this eyepiece, it's hard to know if the specs Don has picked are the right ones.

 

I'm wondering if anyone has actually measured these values.


Edited by CrazyPanda, 24 June 2024 - 08:58 PM.

  • SporadicGazer likes this

#5 Ernest_SPB

Ernest_SPB

    Vanguard

  • *****
  • Posts: 2,005
  • Joined: 13 Nov 2010
  • Loc: St.-Petersburg, Russia

Posted 25 June 2024 - 12:19 AM

It looks like Flat-Field from Kunming United Optics 

See my review of the line: http://astro-talks.r...32&t=865#p10676

 

 

Actual (measured) parameters of the 16 mm

 

Apparent field: 60 degrees
Field stop (open): 16.8 mm
Eye relief: 15.5 mm
Weight: 99 gram
Components/Elements: 3/6

 

Central part FOV looks nice, over field I observed appearance astigmatism and curvature typical for Erfle design. I would not recommend it for fast optics.


Edited by Ernest_SPB, 25 June 2024 - 12:23 AM.

  • CrazyPanda likes this

#6 T1R2

T1R2

    Soyuz

  • -----
  • Posts: 3,700
  • Joined: 11 Jun 2013
  • Loc: Little Rock, Arkansas

Posted 25 June 2024 - 01:32 AM

Going from Ernest specs for the ER (15.5mm)  its still gonna be tight, I would not be happy with that with my glasses, My lowest is 17.8mm but I prefer 18mm+. ymmv 



#7 CrazyPanda

CrazyPanda

    Fly Me to the Moon

  • *****
  • topic starter
  • Posts: 5,736
  • Joined: 30 Sep 2012

Posted 25 June 2024 - 06:32 AM

It looks like Flat-Field from Kunming United Optics 

See my review of the line: http://astro-talks.r...32&t=865#p10676

 

 

Actual (measured) parameters of the 16 mm

 

Apparent field: 60 degrees
Field stop (open): 16.8 mm
Eye relief: 15.5 mm
Weight: 99 gram
Components/Elements: 3/6

 

Central part FOV looks nice, over field I observed appearance astigmatism and curvature typical for Erfle design. I would not recommend it for fast optics.

Thank you Ernest, that's exactly what I was looking for. Eye relief is indeed too tight for my application. Back the drawing board for me!
 



#8 BrushPilot

BrushPilot

    Ranger 4

  • *****
  • Posts: 318
  • Joined: 01 Jul 2021
  • Loc: North Star, Alberta

Posted 26 June 2024 - 04:36 PM

Screw-on Barlow to a 22-24 mm? More ER that way?



#9 Starman1

Starman1

    Stargeezer

  • *****
  • Posts: 66,226
  • Joined: 23 Jun 2003
  • Loc: Los Angeles

Posted 26 June 2024 - 05:39 PM

Better performance, similar focal length, long eye relief for glasses?

17.5mm (17.2mm) Baader Morpheus.

Rated excellent by Ernest.

Specs:

72.2° AF

17.2mm FL

19mm eye relief from glass

21.6mm FS

 

If 17.2mm will suffice, it will be very hard to do better without spending over twice as much.



#10 Starman1

Starman1

    Stargeezer

  • *****
  • Posts: 66,226
  • Joined: 23 Jun 2003
  • Loc: Los Angeles

Posted 26 June 2024 - 05:49 PM

It looks like Flat-Field from Kunming United Optics 

See my review of the line: http://astro-talks.r...32&t=865#p10676

 

 

Actual (measured) parameters of the 16 mm

 

Apparent field: 60 degrees
Field stop (open): 16.8 mm
Eye relief: 15.5 mm
Weight: 99 gram
Components/Elements: 3/6

 

Central part FOV looks nice, over field I observed appearance astigmatism and curvature typical for Erfle design. I would not recommend it for fast optics.

Ernest,

I believe that series (8/12/16/19/27) is made by Barsta.

I think the new series of eyepieces known as "Premium Flat Field" eyepieces are made by KUO.



#11 CrazyPanda

CrazyPanda

    Fly Me to the Moon

  • *****
  • topic starter
  • Posts: 5,736
  • Joined: 30 Sep 2012

Posted 26 June 2024 - 05:49 PM

Weight is an issue that rules out the Morph. This is for a 60mm finder scope on a dob. Trying to keep the weight around 6oz if possible, under 10 for sure.

#12 Starman1

Starman1

    Stargeezer

  • *****
  • Posts: 66,226
  • Joined: 23 Jun 2003
  • Loc: Los Angeles

Posted 26 June 2024 - 07:05 PM

66°/68° 15mm (part of the ubiquitous set of four from many sources: 6-9-15-20) 13ER

65° Sky Rover (KUO) Ultra Flat Field 15mm   16ER

68° GSO Superview 15mm    13ER

60° Sky Rover (KUO) 15.5mm Premium Flat Field (aka PF)   16ER

 

Alas, none of them has an eye relief over 16mm.

16x68 ES--nope.

16mm KUO 82°--nope

15-16mm Plössl--nope.

 

Ah, Vixen SLV 15mm--20ER, 50°, 4.93oz.


  • T1R2 likes this

#13 T1R2

T1R2

    Soyuz

  • -----
  • Posts: 3,700
  • Joined: 11 Jun 2013
  • Loc: Little Rock, Arkansas

Posted 26 June 2024 - 07:20 PM

The only other options I think would be to settle for a 25mm plossl which has the ER you need with glasses (but not the magnification you're looking for) . or a 20mm plossl which may be right on the verge of usable and close to the mag you want, I'm  not for sure that a 15-16mm plossl will not be usable with glasses. The AT 15mm Paradigms is at 15mm ER , the AT PF 15.5mm is at 16mm er (still not good enough)  

 

My 20mm Orion Sirius plossl is close to being usable with glasses and at my cut off for comfort, I prefer the 25mm plossl

 

however the Paradigm 18mm may be ok with glasses, I have one and can use it with glasses but I do have to press a bit to see the field stop, find it more comfortable to take the rubber guard off and make one with craft foam that just has about 1mm height above the plastic twist-up portion of the EP and I can see the whole fov 

 

 

 

Attached Thumbnails

  • IMG_20240626_191404.jpg


#14 CrazyPanda

CrazyPanda

    Fly Me to the Moon

  • *****
  • topic starter
  • Posts: 5,736
  • Joined: 30 Sep 2012

Posted 26 June 2024 - 09:38 PM

Ah, Vixen SLV 15mm--20ER, 50°, 4.93oz.

 

This was one of the contenders, but I figured if I'm going to spend $150-175 on this eyepiece, I might as well just spend $269 on a 15mm DeLite and get a wider TFOV and better edge correction for an F/3.75 finder scope. I tested one of my existing 15mm DeLites out on the finder and it handles it very well.

 

But on the flip side, I'm looking for more TFOV than the 15 DeLite gives if possible. 15 DeLite field stop is 16mm. Clear aperture of the amici prism in the finder seems to be about 19mm.

 

So my unicorn eyepiece is this:

  • 14-16x magnification (finder focal length is 225mm - current 23mm eyepiece gives 10x and I'd like more)
  • 19mm field stop to maximize TFOV while minimizing vignetting
  • Weight under 10oz, ideally under 6oz
  • Nearly perfect edge correction
  • Enough eye relief to use it with glasses
  • Bonus - ability to easily crack it open and add some wires to create crosshairs on the field stop

My main contenders are these:

  1. 14mm Nikon NAV-SW - 8.6 oz (decloaked), 16x magnification, ~18mm field stop / 4.5 degree TFOV, 18mm eye relief
  2. 15mm DeLite - 5.3 oz (decloaked), 15x magnification, 16mm field stop / 4 degree TFOV, 20mm eye relief
  3. 18.2 DeLite - 5.3 oz (decloaked), 12.36x magnification, 19.1mm field stop / 4.86 degree TFOV, 20mm eye relief
  4. 15mm Seibert Ultra - unknown weight, 15x magnification, 18mm field stop (guessing) / 4.5 degree TFOV, 19mm eye relief

The Nikon and the DeLites are going to offer the best edge correction at F/3.75 - certainly much better than the stock eyepiece and better than most other choices, so the whole field of view will render good stars and thus be more functional. I much prefer the 15mm focal length over the 18mm focal length for magnification.

 

Just hate spending that kind of money on a finder eyepiece if I can avoid it, especially since if I got an 18.2 DeLite, it would be my FOURTH one tongue2.gif

 

I tried out the 15mm Celestron spotting scope eyepiece that I got from AliExpress for $12. Total bargain, but the edge of the field falls apart at F/3.75. Also tried my 18mm Orion Epic ED2 and while better than the spotting scope eyepiece, it doesn't touch the DeLite and has a narrower TFOV.


Edited by CrazyPanda, 26 June 2024 - 10:05 PM.

  • T1R2 likes this


CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.


Recent Topics






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics