Planetary

[Greenswale]

Do I really need to try and find a Pentax XO5mm for planetary and double star work in a 120mm APO? Perhaps there is a viable alternative?

[MortonH]

How fussy are you? What eyepieces do you have already?

[Allan]

There is a much better alternative for planetary observing, binoviewing. I have a 5 XO, great eyepiece, but I see more using my Abbe Orthos and Denk bino viewer.

I only took up bino viewing about 3 years ago, but I've been converted. Everything in the Solar System just looks so much better. For deep sky, I still prefer single eyepieces.

If you are looking for a good quality, cheaper alternative to the 5 XO, then the Fujiyama Ortho is value for money.

[Greenswale]

Gentlemen,

Thank you for the prompt responses. In answer, I am really picky, and have a set of Fujiyama HD Orthos.

Allan, I have sent you an email regarding binoviewers.

[Wavytone]

I'm using Vixen SLV's with my 130!mm triplet APO which is f/7 .. these are very very nice imho especially the 4 and 6 mm. They are an improvement on the older LVs - not a hint of colour, and sharp to the edge with 20mm eye relief. Also very comfortable to use, which orthos aren't.

[ausastronomer]

Hi Wren,

Just be aware that binoviewers aren't for everyone. Some people love them, some people don't. It's maybe 50/50.

About 8 years ago Scott Mitchell (WavelandScott) very kindly loaned me his binoviewers and several pairs of premium eyepieces for me to trial, with a view to buying a pair for myself. The pair he loaned me were the top of the line Denkmeier model at the time and the eyepieces were all premium pairs, including 14mm and 21mm Denkmeiers. I also had access to pairs of 24mm Panoptics, 13mm Nagler T6's and 8mm Radians, which were the eyepiece pairs that went with the 12" 3RF binocular telescope I was custodian for at the time. I spent hours and hours and hours trying to like those binoviewers; and as hard as I tried to like them I just never at any time preferred the view through the binoviewers over the single eyepiece view, on the moon, planets or anything for that matter. I tried them in my 10", 14" and 18" Newtonians on multiple occasions over many hours and at no time did they ever float my boat. I wanted to like them because I enjoy 2 eye viewing and have over many years spent a lot of time observing with premium binocular style optics including a 12" binocular telescope and a pair of 25 x 150 Fujinon Binoculars. Unfortunately, a binoviewer isn't quite the same and just didn't cut it for me.

I can only suggest you try (like I did) before you run headlong down the binoviewer path. You may well fall in love with them. On the other hand you may not. It's an expensive road not to like them.

Cheers,
John B

[ausastronomer]

Hi Wren,

The 5mm XO is a really good eyepiece optically, one of the very best. It's eye relief is very short and it isn't a comfortable eye piece to use for long periods IMO. I find that I can see just as much observing with an eyepiece like a 5mm Pentax XW because I am a lot more comfortable and relaxed, whereas observing with the 5mm Pentax XO is an effort, particularly for longer periods. If you're striving for the very best then a top class simple eyepiece like the 5mm Pentax XO, or TMB Supermono, or Astrophysics SPL, or Zeiss Abbe will give up a fraction more in moments of steady seeing than a high class long eye relief widefield, but there isn't a huge difference either.

I would rather be comfortable and relaxed with good detail, than straining to use the eyepiece, notwithstanding it may show a fraction more. The way I look at it is that a 5mm Pentax XW in my 10" or 14" Newtonians is going to show me a heck of a lot more than a 5mm Pentax XO in a 120mm APO, so I am not missing anything compared to owners of 5mm XO's and the like.

Cheers,
John B

[SkyWatch]

Hi Wren,
I find my 3-6mm Nagler is a great eyepiece for planetary and doubles. Very sharp and good contrast, and ideal for nights of variable seeing, plus 10mm eye-relief makes it very comfortable.
Maybe the purists might be able to pick a slightly better view with a top of the range fixed eyepiece- but I'll leave it up to them to comment... I find the ability to find the ideal power for the conditions a real bonus (and it holds focus across the magnification range).
I have seen them advertised second-hand here occasionally.
All the best,

Dean

[Greenswale]

Thank you for the many replies.

Following discussion with Alan, and from advice here, binoviewers are not for me. Astigmatism in one eye, and 120mm aperture rule them out.

Until recently, I enjoyed a full range of Pentax XW in a variety of Newtonians. With the physical effects of age, and reducing aperture, I found that eyepiece image was better for me on reduction of the amount of glass between me and the object. Thus the move to Orthos, and the departure of the quite brilliant XWs.

While recognising the convenience advantage of a zoom type eyepiece, a search suggests that use of individual focal lengths will present better views.

I still have one excellent eyeball and wish to take advantage of it while it lasts! Tight eye relief is not an issue, my 4mm has a quoted 3.4mm eye relief, thus the thought of a the XO.

Summarising, advice given and my preference suggests a minimal glass, fixed focal length type eyepiece. So, what eyepiece offers direct competition to an XO?

[Allan]

At 5mm, the only comparable eyepieces to the XO would be the TMB SMC and AP SPL.

I've had the SMC's and the eye relief is more generous than the XO. They don't work well in fast dobs, but will be nice in your refractor. The tiny 30 degree field of view did eventually get to me.

The AP SPL's are exceedingly hard to get hold of, and that fact alone virtually rules them out. They also have better eye relief, but the XO generally gets more favourable reviews.

I chose the 5 XO because it was easy to acquire and works well in all my scopes and I preferred it to my 5 TMB SMC.

So, I think you're back to where you started from. :)

[Greenswale]

Thanks Allan, time for me to work the 'Wanted' ads.

I really do appreciate the learned responses to my question, thanks people!

[ausastronomer]

Hi Wren

As Allan mentioned, at "exactly 5mm" your choices are limited to the Pentax XO, Astrophysics SPL or the TMB Supermono. The 30 degree AFOV of the Supermonos doesn't work for me and neither does their poor off axis performance in faster telescopes. The 5mm Astrophysics SPL is extremely hard to obtain, so as Allan mentioned you're back to where you started and the 5mm Pentax XO is likely to be your best option.

If you're striving for the very best optically and you move away from "exactly 5mm" your options expand to include the 4mm and 6mm Zeiss Abbes (version 1 or Version 2 are both exceptional) and the 3.8mm Pentax XP. The 3.8mm Pentax XP has a .965" barrell and about 2.8mm of eye relief, but it's an exceptional performer optically. It is normally sourced with the adapter supplied as well, either in Aluminium or Delrin. The 4mm and 6mm Zeiss Abbe's and the 3.8mm Pentax XP would likely be marginally better performers optically, than whatever else you might currently be using at these focal lengths.

Cheers
John B

[Greenswale]

Thanks John. Should my search for the XO fail, Zeiss will certainly Become a target.

I have had another thought. Going to have a look at the Baader BBHS diagonal, certainly some gains for me there.

[N1]

G'day Wren, good idea to look at the diagonal. Not sure if this works for you (physique or preference may mean it doesn't), but leaving the diagonal out altogether whenever you can might result in a greater improvement than going from KK5 to XO5 or SMC5. Cost: nil. I don't use mine for anything below about 70° anymore.

I expect an XO will be cheaper and/or easier to obtain than a ZAO.

[Greenswale]

Thanks Mirko. My preference would be no diagonal, however, being over 70 means that it can only remain a preference!

Might take up yoga.........

[N1]

G'day John, sorry for the diversion but I'm quite interested in your observations with the binoviewers vs monocular vision. I've been thinking about binoviewers myself but never did go down that path but still kept wondering. Are you able to say what the main reason might have been, for you not liking them over single EP viewing? From your comments I'm assuming it wasn't to do with the usual focusing/weight/cost issues but the actual viewing? Cheers

[Don Pensack]

A planetary eyepiece you might consider, because the spot diagram indicates it's the sharpest eyepiece they've ever produced, is the TeleVue DeLite.
It's 62°, so it could be a "general use" eyepiece as well.
And it's no accident the focal lengths start at 3mm, then 4mm, 5mm, 7mm, 9mm, etc.

There are many fine "planetary-oriented" eyepieces out there now. Some have long eye reliefs, some short, but you can find just about anything you want in a focal length from 1.6mm to whatever. It's a great time to look for short focal length ultra-sharp eyepieces.

[Don Pensack]

One thing you have to be aware of with binoviewers is that if the field is wide enough, you will not see either the right or left side of the field with direct vision--peripheral vision, yes, but not direct vision. You can raise and lower both eyes and see the top and bottom of the field at the edge, but rolling the head, even a little, to look at either the right or left edge of the field takes one of your eyes away from the exit pupil.
As a result, many hardcore binoviewer users prefer 40-60° fields, for that reason.

Another issue is substantial light loss and/or chromatic issues somewhere in the field, too. Maybe they're great for planets in a tracking scope, but I am like John B. and never really took to them like many. I always preferred the single eye view.

Now, my dominant eye has image resolution problems, so binoviewers don't even help planets. I can see the appeal, though, given it is often more comfortable to view with both eyes.

[ausastronomer]

Hi Mirko,

The problems were all to do with the viewing experience. Cost wasn't an issue, at the time; and weight wasn't a concern either. All my scopes were medium to larger scopes (10" to 18") and were all fitted with Feathertouch Focusers and Servocat tracking. At the time I had Scott's bino's Saturn was very well placed (at Zenith just before midnight) so I spent a lot of time on it and I also spent a lot of time on the moon, when it was around.

Don has pretty much hit the nail on the head.

With some of the wider eyepieces I kept losing the exit pupil trying to take in the full field of view. This was further compounded by the fact that I wear high quality multifocals when I observe and I often found I was looking outside the fully corrected area of my glasses trying to take in more of the FOV. I had observing with multifocals down pat with single eyepieces in learning exactly how to observe with them and not suffer any loss of image quality. The funny thing is I have no problem using binoculars with long eye relief combined with my multifocals, but both of my binoculars have a fairly narrow FOV for their size and aperture.

The other thing I really didn't like was the drop in image brightness on Saturn. Having observed with large aperture scopes for a long time I guess my brain was just accustomed to expecting Saturn to be at a certain brightness level. It was a bit the same on the moon. I observe the moon unfiltered in all my scopes including the 18", as I get more detail unfiltered. Again I guess I am accustomed to perceiving it should be brighter than what I was seeing. The moon in binoviewers would work for a lot of people because they can't cope with a really bright image and dimming it without the use of a filter would help them, but it wasn't for me.

The other thing was that I had spent quite a bit of time using a 12" binocular telescope and it just wasn't remotely close to the same experience in regard to the 3D effect on DSO targets like Eta Carina, 47 Tuc and the like. Maybe I had been spoilt somewhat in this regard and my expectations on DSO's were too high. I still have ready access to the 12" binocular telescope, so not much point in me buying a binoviewer.

Cheers,
John B

[Kunama]

I find that being comfortable at the eyepiece with decent eyepieces is more important when viewing planets. To me this usually means a 130mm apochromat on a tracking mount with binoviewers and a pair of NaglerT6 or Tak LE eyepieces while seated comfortably at just the right height.

This allows me to see detail that is only revealed in those moments of perfect seeing. If I am mono viewing I find that covering my non-viewing eye while keeping it open is better than closing it but for me binoviewers are a far more relaxing way to view planets.

I haven't tested the binovues in the big scope yet.....

[wavelandscott]

I will jump in here to add a few comments on the binoviewers...mine are okay but as John and Don suggested, I never fell in love with them. I really wanted to love them but was not "wowed" in my dobsonian reflectors. I like them better in my refractor but still not as much as I like my recently purchased big binoculars. I do enjoy the two eye vision aspect versus mono.

There was/is not anything wrong with them they just did not generate the same passion...not sure how to describe it better. I think John and Don are on to it in their description.

[N1]

Thanks John and Don for your comments on the bino viewing. Knowing my own observing priorities there is a good chance I might have similar problems, except perhaps for the eye relief. It appears that using 2 separate OTAs makes a huge difference over splitting up the light cone provided by a single one. I will now definitely try them elsewhere at some point before even thinking about buying anything. In the meantime, I'll stick with regular binoculars for low power sweeps.

[ausastronomer]

Hi Mirko,

To try and put that in to some form of perspective:-

1) A 12" Binocular telescope has about the same total light grasp as a 16" to 18" telescope, albeit shared between 2 eyes.

2) An 18" Telescope with a binoviewer gives about the same image brightness as a 12" to 13" telescope, albeit to 2 eyes.

The big thing to me is that binoviewers don't give you the same 3D effect and depth of perspective that you get with a true binocular telescope, or a pair of large aperture high quality binoculars. I am very fortunate in having access to both a very good 12" binocular telescope (Suchting mirrors) and a pair of 25 x 150 Fujinon Binoculars. It doesn't really got much better than those two instruments, for 2 eye viewing. The 12" binoscope is great because you still keep both feet on the ground and the views are stunning. I have used up to a 22" binocular telescope and while the views were exceptional when it all "clicked", they are pretty hard to handle and get right.

I have used high quality refractors to 15" aperture and newtonians to 36" aperture and the two single best telescopic views I have ever had, in over 40 years of observing, were M51 in Larry Mitchell's 36" Obsession and Eta Carina in the 12" binocular telescope, using a pair of 13mm Nagler T6's. The effect of the binocular telescope on the ETA Carina view made you feel like you were James T Kirk flying the Enterprise through the dust lanes as they gave the view so much "depth". Targets like ETA Carina, M42, The Tarantula, Omega Centauri and 47 Tuc just come to life in a binocular telescope and take on a whole new dimension.

Looking through a good quality medium to larger aperture binocular telescope (8" plus) is something every visual amateur astronomer should have on their bucket list.

Cheers,
John B

[N1]

Hi John, thanks for your review, appreciated. To me 1) and 2) mean that I should probably stick with monocular observing unless it's a true binocular telescope. Hopefully I'll get to try both options at some stage to see the difference for myself. I too am likely to find the light loss too much of a trade off, especially with the amount of small aperture observing I do.

[Greenswale]

I am in receipt of the Baader BBHS 2" diagonal. First impressions from light polluted home are excellent. Colours are more pronounced, scatter is way down, brightness and definition are improved.

Definitely a keeper, looking forward to dark sky use.

This one change has enhanced the visual experience over all of my eyepieces. Hmmmmm, do I really need that XO 5, he, he!!!

[Greenswale]

Final outcome. Had quite a few hours under a dark sky, with the new diagonal.

The improvement over all my eyepieces, 1.25" Fujiyama Orthos, and 2" UO SWA has me concluding that my overall system is just about maximised. The clincher was being able to make out some detail on a very tiny Mars, the extraordinary red of Hind's Crimson Star, the ease of six stars in the trapesium, plus the fun of splitting doubles, including Sirius.

Might all change if I end up with a special OTA, but.........!

Thank you to all who provided opinion. The move to a cracker diagonal was out of left field, but is absolutely worth it.

[doug mc]

One thing I found using binoviewers is that the brain seems to do a summation of the incoming images of both eyes and selects the best possible image. I have astigmatism in my right eye, which is my dominant eye. When looking at anything with my glasses on, by looking with my right eye i see remaining astigmatism. When looking with my left eye, the astigmatism is no longer apparent. With both eyes open, my brain gives me a view with the best(left) eye image. So with binoviewing i get the comfort of using both eyes with the astigmatic correction of my left eye. It's a winner for me. So astigmatism in one eye worse than the other should not put you off binos.

[Waxing_Gibbous]

Can highly recommend Takahashi LEs and Hi-LEs for planetary/ Lunar work.
No scatter that I can see. Sharp, sharp, sharp edge to edge and great contrast. They are expensive, true, but at the moment they are priced almost exactly the same as in the US. Bargain! I think they are available only from AEC.
IIRC the Pentax XO line is discontinued ( chime in if I'm wrong anyone ) so it might be a bit of a fag getting one, as owner's hang on to them for dear life!