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Best 18mm Orthoscopic EP for Binoviewing


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I use my binoviewers to view the Moon and Planets with my 4" Astro Tech APO and 180mm Mak/Cass.

I recently bought a pair of Pentax 6.5mm-19.5mm zooms but to be honest its not easy to get comfortable viewing - nose too big maybe!!

I have decided to buy a pair of 18mm Orthoscopic EPs and clearly there are 3 possible candidates - Baader BCO, Astro Hutech and Fuijyama. From the various reviews that I have read the view is very similar but I am concerned about inward travel especially with my frac which is nearly at the buffers when I use binoviewers even with a barlow.

For members that have used any of these Orthoscopics is focusing tight on any particular model?

Any recommendations on any of these - the focal ratio is f6.95 on the frac and f15 on the Mak/Cass

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Mark,


I hope John can chim in for best detail, he's the one of few who has used all these three orthos.


FWIW, I've measure all my EP's focus travel, with the info I got from CN where Tami has measured many of his EPs focus travel, we have following info: if we take Pentax XWs/Nikon SW as reference point, BCO 18mm needs about 4mm more outwards travel. 8mm ETHOS 5.5mm inwards in 1.25" mode, 32 TV plossl 4.5mm outwards, 24mm and 19mm Pan 5.5mm outwards. TV 11mm & 15mm plossl 6mm outwards.


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The Baader Classic orthos and Fujiyama orthos reach focus around 8mm further outwards than the Baader GO's and most of the Astro Hutech orthos if thats any help Mark. The Tele Vue "B" parfocal point (plossls, Radians, most Delos etc) is a bit further outwards again. Baader GO's / Astro Hutech orthos require more inward focuser movement than most of the other eyepieces I use.

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PS: The Baader Classic 18mm Orthos are very good optically - for deep sky observation I reckon their light throughput exceeds even the 18mm Baader GO / Fujiyama / Astro Hutech orthos just a wee bit. They are all excellent though :smiley:

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Thanks for the information. Because of the tight inward travel on my 4" Astro Tech it seems that the best option is the Baader or Fujiyama. The Fujiyama looks nicer but the Baader has the rubber eye cup so stops your eye socket freezing to the bare metal. In addition the Baader is £49 from FLO and the Fujiyama is £79 from Lyra Optic.

I have not dismissed the 20mm TV Plossl but the Baader seems the best option for my binoviewers.

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I use the Baader bco's 18mm with my William optics bino's and they are excellent, the eyecups realy help keep the light out and they have a kind of volcano top instead of been flat which I realy like and they are small and light weight.

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I use the Baader bco's 18mm with my William optics bino's and they are excellent, the eyecups realy help keep the light out and they have a kind of volcano top instead of been flat which I realy like and they are small and light weight.

Thanks for that - Baader 18mm BCO it will be :smiley:

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If the BCOs have rubber eyecups, that would be my choice as well. Part of the benefit of binoviewing is comfort and time at the eyepiece(s). Soft rubber eyecups help. Is it a coincidence that binoculars are often fitted with soft rubber eyecups, and they are generally comfortable to use.

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I think 18mm is a real sweet spot for binoviewing, whatever brand you use. My Takahashi LE 18mm pair give 105x in my 5" 1905mm fl refractor ( I don't need a Barlow as I had my tube shortened) and the views of M42 etc are stunning.

Even with a 1.6x Barlow the 18mm EPs will effectively operate at c11.25mm so on say an 800mm fl scope you'll still get a nice c70x or so..

Plus nice eye relief for comfortable viewing:-)

Dave

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I think 18mm is a real sweet spot for binoviewing, whatever brand you use. My Takahashi LE 18mm pair give 105x in my 5" 1905mm fl refractor ( I don't need a Barlow as I had my tube shortened) and the views of M42 etc are stunning.

Even with a 1.6x Barlow the 18mm EPs will effectively operate at c11.25mm so on say an 800mm fl scope you'll still get a nice c70x or so..

Plus nice eye relief for comfortable viewing:-)

Dave

Thanks Dave I was not aware of the Takahashi LE - will give it a look.

Currently the view using my 25mm Plossls in my 4" Astro Tech APO is stunning. I just felt that the 18mm would be perfect EP both in the 4" frac and the 180mm Mak/Cass.

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Hi Mark

The Tak LE's offer superb build and contrast but are not cheap-£200+ new!

They also offer a 52deg field but to be honest if you can get a pair of BCO's new for c£100 with a similar FOV I think that would give you best bang for your buck.

And in my book most Baader stuff is top class optically :-)

Cheers

Dave

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Yes thanks again Dave. I have used lots Baader equipment over the years (Hyperioin EPs, zooms, Witty mount etc) and have always been satisfied. I currently use the Hyperion zoom 2.25x barlow with my 13mm and 8mm Ethos EPs and get fantastic results. The barlow screws nicely into the base of the Ethos only slightly incresing the overall length.

Clearly everyone seems to recommend the Baader BCO and the extra FOV will help because I don't use a motorised mount.

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Just received a used 18mm BCO. Very impressed. Easy to look through, very clear. Thought gave slightly darker background and a cleaner image than my ES 20mm 100*, and thats no slouch. Like it, like it a lot.

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Congratulations Bart!

I bought BCO18 after reading many reviews of EPs, John's excellent review on BCOs amongst others,  John was the first one here warmly recommended BCO18 with his review, I can only second him, the 18mm BCO is the most outstanding EP considering performance vs price. Glad to see more and more happy owners. :smiley:

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  • 2 weeks later...

Well, you have convinced me :grin: .

I can't really afford the luxury of the cash tied up in Tak LE's at the moment so I've let them go very reluctantly and am replacing them with BCO 18mms...

I'm not expecting them to be better than the Taks, but if they are as good optically or very close to it I'll be delighted. Will post my impressions when I have them and we get rid of the Moon and clouds!

Dave

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Well I decided in the end to buy the 18mm Fujiyama Orthos. I did this mainly because Glen at Lyra Optics dropped the price by £10 to £69 because of the Yen + free postage.

I used them last night on my 180mm Mak/Cass to view the Moon and Jupiter - all I can say is 'wow'. Although the FOV is narrower than the BCO I had no problem keeping track using the slow motion controls on the SkyTee 2.

The EPs provided a crisp and very sharp view across the whole FOV - no light scatter - just a fantastic view. I have no doubt that the BCO would be the same but in the end I just liked the Fujiyama. One further point the whole range is parfocal and I easily obtained focus in the Mak/Cass (to be expected) but I also had no problem in my 4" frac when I viewed the Sun in the morning.

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