1.25" restrictions ?

[spaceboy]

In the interest of keeping the weight down and retaining the flexibility 1.25" eyepieces offer I kept hold of most of my ES 82° eyepieces when I upgraded to 2" ES 100° eyepieces. It got me thinking......... now I'm aware the 24mm 68° eyepieces offer the maximum FOV that can be attained in 1.25"" format but would a 2" eyepiece offer more FOV over a 24mm 1.25" ep if that too was 68° AFOV ?? Sorry if this is a dumb question as I understand the field stop of the 2" ep is larger but if the AFOV of both ep's are the same would the larger field stop actually allow for a larger FOV over the smaller 1.25" ep ??

[John]

If the AFoV is 68 degrees then the true field is the same regardless of the barrel size. If the field stop is larger the AFoV will get larger and it won't be a 68 degree eyepiece any more.

24mm / 68 degrees is about as wide as the 1.25" format will allow as is 18mm / 82 degrees and 32mm / 50 degrees. All these eyepieces would have close to the maximum field stop size that you can squeeze into the 1.25" format.

[spaceboy]

Thanks John. Another stupid question but, I don't suppose you know of an 18mm 82° 1.25" eyepiece do you ??

[Peter Drew]

A Speers Waler zoom eyepiece has a 82 degree AFOV at the 18mm setting AFAIK. 

[John]

Meade did an 18mm 82 degree in their Series 5000 UWA range. That was in the 1.25" fitting.

[spaceboy]

Thanks again for your help guys.

[Ruud]

There's a Maxvision 82° 18mm. It costs €109 new. I have no idea how good it is. It is identical to the Meade 5K UWA (when that was still made by JOC).

[bingevader]

Are they still around? I haven't seen one for a while. I can vouch for the ES 18 mm, but it's 2".

[alan potts]

Ben,

 The ExSc 18mm is a 2 inch fitting, I read some believe the optices to be the same in different clothes, me I have seen neither.

It may be nice to see a few words on the 18mm UWA as not much seems to have been said anywhere about htis eyepiece, it was the one that got away for me.

Alan.

[nicoscy]

The below eyepieces are from Don Pensack's EXCEL sheet. All 1.25" and 18mm. Hope this helps:

Brand Model Type FL AF           Agena Starguide Dual ED Planetary 18.00 60 Arcturus ED LER 18.00 55 Astro Hutech HC Orthoscopic Orthoscopic 18.00 42 Astro Professional Long Eye Relief LER 18.00 55 Astro Tech Paradigm Planetary 18.00 60 Baader Planetarium Classic Ortho Orthoscopic 18.00 55 Barsta (aka BST) ED Planetary 18.00 60 BST (see Barsta) Starguider ED General Use 18.00 60 Celestron X-CEL LX LER 18.00 60 Coronado CeMax Plossl 18.00 52 Deep Sky (only in Russia) Plano ? 18.00 60 Desert Scopes Extreme View ED LER 18.00 55 Edmund Optics Orthoscopic Orthoscopic 18.00 46 Explore Scientific 82 Series UltraWideField 18.00 82 Fujiyama HD Orthoscopic Orthoscopic 18.00 42 Harry Siebert Optics Performance + ? 18.00 60 Harry Siebert Optics Ultra Wide-Field 18.00 70 Harry Siebert Optics Ultra Wide-Field 18.00 70 Levenhuk Ra ER20 Wide-Field 18.00 68 Levenhuk Ra LER long eye relief 18.00 55 Meade Series 5000 HD-60  Planetary 18.00 60 Olivon  High Definition Planetary 18.00 58 Omegon Flatfield ED General Use 18.00 60 Omegon LE Planetary LER 18.00 55 Omegon Super LE   LER 18.00 68 Russell Optics Research Grade Konig Konig 18.00 67 Russell Optics Research Grade Konig Konig 18.00 70 Smart Astronomy Solar System Long Eye Relief LER 18.00 55 Takahashi Abbe Orthoscopic Orthoscopic 18.00 44 Takahashi LE Masuyama? 18.00 52 Telescope Service ED   LER 18.00 60 Telescope Service Paragon ED General Use 18.00 50 Zhumell Z Series Planetary Planetary 18.00 55

[nicoscy]

And although in preview mode it looked well, it doesn't when posted.

Use Dropbox Link to the actual EXCEL (properly filtered for 18mm 1.25")

[spaceboy]

Thanks for the replies. I have had a look for a Maxvision 82° 18mm and can't find anything anywhere. As for the Meade 82° 18mm I think those who own them are going to be reluctant to part with them anyway so I think I will have to stick with the idea of a 68° 24mm.

Thanks for the links Nicos but it was specifically the 82° 18mm in 1.25" inch I was interested in.

[gbarnett]

Hi, there's this site www.robtics.nl/index.php?cPath=28_46_794 (is there any easy way to show a link here or to edit a hyperlink?... I'm not sure if this link will actually work  ) This shows the 18mm 82 degree MV as available. I'm sure I saw these in 1.25" fitting elsewhere a while ago but this site doesn't make it clear if it is 1.25" but you could always contact them to check.

Graham.

[spaceboy]

Thanks Graham

[bingevader]

Alan, I have the ES version and it's fab. I can remember a previous discussion about it being a 1.25" Ep in 2" clothing and would have to agree. I can't find an 18 mm 1.25" Maxvision anywhere either though.

[Ruud]

The MV 18mm 82° may be getting scarce. Robtics still lists it, but as Graham suggests, it is a good idea to check first if they still have it.

The MV 24mm 68° seems to be available still. I bought it to replace a 32mm 50° Plössl. The 24mm also gives a maximised true field of view in a 1.25" fit. It is a well corrected eyepiece with a very comfortable exit pupil and works nicely at focal ratios down to F/5. (I can't test it below that for lack of a faster  telescope.) It costs €79, a true bargain.

--

@Graham To make a nice link, first select a word in your sentence, then click the 9th button in the second row of the toolbox and paste the url.

[gbarnett]

Thanks Ruud!