18mm Ortho + Barlow vs 9mm Vixen NLV

[MortonH]

I'm looking for an eyepiece around 8-9mm with very good contrast, throughput and neutral colour. I want it to be lightweight so it can be used in my small refractors, which rules out Delos, LVW, etc. It also needs to be reasonably low cost and have minimum 50° AFOV.

Based on a lot of research I'd like to try an ortho, but I'm not comfortable with eye relief less than 12-13mm. Therefore I've been wondering about an 18mm Ortho with a 2x Tele Vue Barlow. However, I'm not sure to what extent the extra elements in the Barlow will negate the ortho advantage, in which case a Vixen NLV or SLV might be a better choice.

Any thoughts?

[Allan]

Hi Morton. I just arrived home after 4 nights observing where I was comparing a number of new eyepieces, mainly looking for best lunar and planetary performance in my bino viewer. I also spent some time comparing them to my Delos on faint planetary nebula and galaxy clusters at the limit of visibility to see if I could observe a difference.

All the minimum glass type eyepieces were between 15 mm and 18 mm so I had to use a Powermate, which has even more elements than a Barlow. The coatings are so good that any reduction in transmission wouldn't be visually detectable.

I found the minimum glass types with the Powermate performed equally as well as the Delos. I know Alvin Huey in the US uses a TV Barlow with his Zeiss Abbe Orthos in very big Dobs to hunt really faint galaxies. So that's good enough for me.

Bare in mind an Abbe Ortho has a FOV around 44 degrees. You would need to go to a Plossl to get your 50 degrees, but they have even less eye relief than Abbe's. Based on what I have seen over the last few nights I prefer the new Takahashi Abbe Ortho more than the TeleVue Plossl. The 18 mm Tak Abbe has all the qualities you are looking for and 15 mm eye relief makes it very easy to use.

[MortonH]

Thanks Allan.

I'm considering the Baader Classic Ortho which has a 52° field. I've read that the edges may not be perfect but I'd still prefer the "less claustrophobic" feel than 44°.

[Camelopardalis]

Morton have you considered the Baader Classic Ortho? They're decent, reasonably priced and the 18mm should give you sufficient eye relief.

[MortonH]

Must have posted my last message while you were typing!

I found a review of the BCOs and the guy said that the useable eye relief on the 18mm is only 6mm from the top of the eye cup. That's put me off a bit unless owners here can comment?

[Allan]

The eye relief of an ortho runs at about 80% of its focal length. So the 18 should have an eye relief of about 15mm. The beauty of using the Barlow is it will increase that a bit as well as tidying up the edge of field softness that the BCO's have as well.

As far as the 6mm ER in the review, maybe that's measured from the top of the winged eye guard, which sits above the eye lens. You could take the eye guard off to get the full ER.

[MortonH]

Yes, after re-reading the review the 6mm is from the top of the eye guard, so not bad.

[dannat]

i agree with what allan said, a good barlow is hardly noticeable the BCO orthos are good value, ive used the 6 & 10mm

[MortonH]

Thanks, guys. I've placed a Wanted ad for something in the 15-18mm range to give me enough eye relief. I'll even try one of the narrower FOV models just to see what the views are like. :D

[Kunama]

Pentax XF8.5 would be my pick

[MortonH]

I have the XF 8.5 and 12mm. It was actually an old Cloudy Nights comparison of the XF 12mm and a 12mm Radian that made me think about an ortho. In the review an ortho was used as a reference eyepiece against the other two. I was very interested in the different level of detail seen in galaxies across the three eyepieces.

Since orthos are relatively cheap I thought I might like to try one for myself. But the XF is going nowhere! ;)

[MattT]

I have had a 9mm NLV and and a nice eyepiece it is too. But in the end I went for a pair of 18mm orthos in bino's for me. The Vixen was so close to a Pentax XW 10mm that apart from the TFOV there was next to no difference...but the ortho and 2X TV barlow has a slightly more 'live view' even in mono...not sure how to put it! In music terms it's a 'present' sound, more natural.... know what I mean?
The added bonus is you get two eyepieces FL's too. The difference in the AFOV at the eyepiece is probably not worth a consideration....they are both narrow.
Ortho and barlow (has to be a TV barlow) wins ...IMHO
Matt

[MortonH]

My wanted ad has only generated one offer and it was an older 0.965" model that doesn't suit.

I guess the Ortho owners around here know when to hold on to a good thing! :lol:

[Profiler]

Hi Morton

I recently acquired a 9mm Vixen NLV and I am extremely impressed with it. In optical performance it is identical to a XW10mm (only a 3rd of the size) and better than 10mm Radian and 9mm Nagler T6

I haven't compared with Pentax XF8.5 but suspect it will identical but at near half the cost

[MortonH]

That's good to hear that the NLV performs so well. I'm very happy with my XF8.5.

[Profiler]

I have the XF too but haven't had a chance to compare with all the rain - the NLV is however about 2/3rds the size so already a good option for portability given its price in case of any accidents.

[Camelopardalis]

Must say I've been impressed with both XF in my baby cat, great grab and go set with a 24 Pan ;)