BGO 7mm & 9mm available

[Stargazer_00]

Didn't know that, cheers Alan. I'll go read it now

[russ.will]

Woo hoo!

[Qualia]

Gorgeous little buddies those BGOs. They've still got the 18mm on sale here in Spain (I think) for around €99, if anyone was interested.

I think I just about read everything there was written on the Delos line and Alan's review is worth more than just a little read.

Alan, I can't imagine the Delos being better in any manner except, perhaps, if size was a serious issue.

[John]

EDIT: I did a mock up of a photo of Plato at about the same moon phase as last night versus the sketch i did. The red circle is a match. the blue circle I saw as one but is actually two. the green area is where I saw a white line crossing the crater, barely visible in the photo though and the yellow circle was where I suspected there was another but couldn't say for sure. turns out it was one so I think that counts.

I now believe the real challenge here lies in visibly splitting the pair in the blue circle

My 12" F/5.3 was showing 4 plato craterlets last night including the close pair. The best I've done with the scope so far was 6.

The seeing could have been better last night - by the time Saturn rose high enough to be worth viewing things had gone quite mushy at anything more than 200x. Managed to see Enceladus and Iapetus though.

[alan potts]

Qualia,

Thank-you for the kind words, it is nice to know that people read them and enjoy them, I like to try to get as much of a mix in there as possible because we all have different tastes when it comes to what we look at. Myself I am not a big faint a fuzzy fan but on some of the other Delos reviews I have written (4.5mm and 6mm) I have included a couple of galaxies, half the time I don't know where they are from memory. When I am taking notes at the scope I am not very organised with star maps.

The one thing that is a bit of a concern with the Delos is smaller dob users, there no reason why they would not want to use quality eyepieces but sometimes maybe the size and weight of some of these newer eyepieces is a bit off putting. This is of course not a thing we see with the BGO and Hutechs most are very small and even the 18mm versions are not heavy, not that I have ever seen one.

Alan

I have ordered a Kasai version of the 18mm which John reckons it half decent if it is the same as anyone which I believe was Universal Optics. I will have to wait and see.

[Stargazer_00]

i really enjoyed it too Alan. A good mix of controlled test, a range of scopes and some good humor was a good read, cheers

[Stargazer_00]

My 12" F/5.3 was showing 4 plato craterlets last night including the close pair. The best I've done with the scope so far was 6.

The seeing could have been better last night - by the time Saturn rose high enough to be worth viewing things had gone quite mushy at anything more than 200x. Managed to see Enceladus and Iapetus though.

That's awesome John. I can only get 200x with ortho and 255x is my max mag. I don't use a barlow. though I have a poopy SW one and a 2" ED 2x revelation one.

I am considering getting a TV barlow 2x or a ES telex 2x to get more juice out of the BGO for rare occasions, it could sub as a 3mm. I dont think I'm going to get more from Plato at 200x. That yellow ringed one is probable as I thought i saw it a few times just nothing constant due to seeing and now I know that the blue ring is a pair Im sure a bit of wishful thinking will allow me to resolve them quicker. That why i wanted to sketch it because if I had fore knowledge of what to look for it makes it all a little easier. What I sketched there was exactly what I saw, I had no idea how many I was looking for, where they were or anything which made it kind of fun

I'm sure when I get a 14" it'll make things alot easier, the mirror quality is likely to be similar though as I doubt I'll score a high PV s/h OO 14" before I've saved for the SW flex 14". Going to go lunar tonight and try to work out whats going on with the BGO. I had just put it out and looked at the moon and im certain it isnt field curvature now as adjusting focus near field stop does nothing but worsen things. There is absolutely no way that edge performance is equal to on axis. sure I can see details but it's mushy by comparison to the on axis detail. Am I expecting too much, being too critical?

I mean im not unhappy with it, it just doesnt deliver on axis performance on the field stop and does degrade leading up to it. I've never known an eyepiece not to do that though. I've got pretty good eyes, spent a few grand ensuring they work well!

[Stargazer_00]

Small updates, been testing this BGO solidly in both scopes for the last hour.

It does definitely degrade to field stop, without a doubt.

Let me quantify what I'm saying here though. At 125x in the explorer 150p I am able to see the craterlet I circled in the mock up above in red, this is the easiest of them all to see. I struggle to see the others on axis but this one is no problem. I can track this from centre to edge and still resolve it on the field stop. However it simply is not as sharp or defined as it is on axis.

Perhaps the mere fact that is able to be resolved on the field stop quantifies what some people described as 'razor sharp to the edge' and in fairness what I'm calling degrading from centre to edge is probably a 10% drop in performance. It certainly isn't horrific, i mean I can resolve craterlets in the field stop, my lunar 100 guide describes these features as "on the limit of detection" so that's something to measure my perception by perhaps.

This is a small scope as well, really.

In the 10" at 200x I can resolve the craterlets to the field stop as well, but here the drop off seems a little worse. And I mean just a little, maybe 12% difference to on axis at field stop.

Now here is the corker, wrap your head around this one. I went and fetched my old, crusty, cheap 2x skywatcher 1.25" barlow. Unscrewed the element and screwed it onto the BGO. This, gives a 50% increase I read. So the explorer 150p gets 187.5 x and the 10" gets 300x. It's hard to say if the on axis performance dropped significantly because the magnification boosted alot in both scopes. It was still good on axis though. I noticed the barlow element introduced a slightly brown tinge to the entire view which I guess is poor colour control and just poop lense quality. The notable thing here was the on axis to edge performance was nearly identical, what i mean was i witnessed almost no difference in on axis to field stop.

!!

That really left me scratching me head... any ideas?

Oh and update on the Plato craterlets. Maybe its just illuminated slightly better tonight for observing but I nailed the blue rings pair without any problem, the yellow ringed on was blatent and I even got that one in the diagram near the crater rim to the direct right of the yellow ringed one. All as plain as day. Got them all in the 4.7mm ES as well, perhaps even easier in this tonight than the BGO...got me thinking some more.

The seeing was very variable tonight so it's difficult to say anything for sure but I repeated the above tests over and over and over again. I had to be sure what I was observing was not just variable seeing but a repeatable behaviour, which i am satisfied i did.

[John]

Generally it's when the seeing is at it's best that the best optics show their slight edge. When it's not quite there the differences are either not apparent or much harder to perceive.

When I was comparing a 5mm University HD ortho and a TMB Supermonocentric last year I had about 7 or 8 sessions with them. 2 of these were under excellent conditions and on those evenings the TMB Supermono was just that little bit better at showing subtle planetary features and controlling light scatter. The rest of the time I could not see any differences between them.

[Stargazer_00]

That's fair then. neither evening has been perfect, only showing moments of perfection. I'm certainly not unhappy with the purchase, at all. Nor am I in any way in happy with the ESs to which im comparing it against. All these EPs are keepers.

[andrew63]

I can't compare with your telescope as i use a refractor. But what you describe as the view with the barlow is what i see with a 6 BGO - no real difference in sharpness right across the field.

It could be that your primary mirror has a bit of a turned edge - which could give that slight softening you mention - which would be a factor irrespective of eyepiece used. With the barlow in the equation you could be lessening the defect?

andrew

[username]

I don't observe with fast reflectors but I get a little bit of this in my mak, could the softening be a bit of coma on the edge? At high mags you may not notice it in dim stars but on the moon it could be more noticable.

Like I said though I don't observe with fast reflectors so it could be absolute twaddle

[John]

Where the 6mm BGO made a particular impact on me recently was in splitting Sirius. I've 2 examples at the moment and both perform identically in this respect, controlling the light scatter from Sirius A slightly better than the BCO, Pentax XW 5mm and my 6mm Ethos. I can see "the Pup" with the other eyepieces but the BGO 6mm makes it just that little bit easier.

The above characteristic is also useful for picking out E & F Trapezium and Saturns moon Enceladus from the glare of brighter nearby objects.

[Qualia]

I've just come in from a session with the Moon. Conditions were around 8ºC, with very light breeze and a seeing level of about 2 of 5, that is, quite poor. The scope used was a 10" f/5 truss-dob which had been allowed to cool for a little over two hours prior to the session.

For the observation, I used the BGO 5mm, 6mm, 7mm & 9mm and by way of having some kind of benchmark, I 'compared' each EP to the Delos 10mm.

With the Moon I figured I'd be able to closely evaluate edge sharpness - and in my eyes, both the Delos and BGO EPs performed equally well. Crisp across the entire image and excellent color rendition. Probably due to lesser magnification, a significantly greater FOV, more comfort and optimal 2mm exit pupil - I did find the Delos offering a more contrasty, brighter and aesthetically pleasing image, and to be honest with the entire moon housed within the EP at a useful 125x, I could have spent the whole night just viewing the Moon through the Delos. But when solely comparing the 5mm to the 6mm BGO, or the 6mm to the 7mm, I could find no difference in sharpness or edge performance, other than a slight dimming of the image as I upped the magnification.

I appreciate that there are many factors that contribute to what an individual will see when at the eyepiece and that the eyepiece alone does not determine the quality of the image. Everything must be taken into account not least the entire light path from the upper atmosphere right down to the little nerves in our eyes and the neurons in our brain. Viewing conditons, telescope, our disposition all contribute to what we will see and this evening I couldn't find anything to downstep the BGOs and still consider them fantastic performers for their price.

[alan potts]

Generally it's when the seeing is at it's best that the best optics show their slight edge. When it's not quite there the differences are either not apparent or much harder to perceive.

When I was comparing a 5mm University HD ortho and a TMB Supermonocentric last year I had about 7 or 8 sessions with them. 2 of these were under excellent conditions and on those evenings the TMB Supermono was just that little bit better at showing subtle planetary features and controlling light scatter. The rest of the time I could not see any differences between them.

John,

You had 7-8 sessions by what I read from most of the members it has been difficult to get out that many times all this winter. BTW I Powermated the 8mm E in the Mac/Newt last night for the first time on the Moon, very impressed, I will be doing that again. Sharp as I have ever seen everywhere, even the wife liked it, some eyepiece.

Alan

[John]

John,

You had 7-8 sessions by what I read from most of the members it has been difficult to get out that many times all this winter. BTW I Powermated the 8mm E in the Mac/Newt last night for the first time on the Moon, very impressed, I will be doing that again. Sharp as I have ever seen everywhere, even the wife liked it, some eyepiece.

Alan

Thats true - the lack of good observing nights makes it very difficult to compare items carefully and it's easy to jump to a conclusion about something on the basis of very limited experience.

I was Powermating my 8mm and 6mm Ethos last night on Saturn with my ED120. Very nice views even at 300x. How do Tele Vue make all that glass so invisible ?

[Stargazer_00]

That's impressive. I'm often amazed by what you guys seem to be able to eek out of smaller aperture refractors and good eyepieces.

[alan potts]

John, Graham,

I have no idea how thet work but I am pleased they do. I find it difficult to see how anyone could improve on the Powermate. I see adverts for very fancy offerings from Baader with all sorts of exotic glass at big ticket prices but the Powermate to me is a reasonable price once you know what it is able to do. I almost let mine go due to the fact I was not using it and it was only your reports of the Ethos double up that stopped me in my tracks. I well pleased you did, thanks.

Graham you have got to get one, they work just as well with the ExSc 82's.

Alan

[Stargazer_00]

Too tempted...I'll save that for a year's time after I've upgraded my main scope when I start swapping ES for TV

[John]

That's impressive. I'm often amazed by what you guys seem to be able to eek out of smaller aperture refractors and good eyepieces.

Saturn seems to respond better to high magnifications than Jupiter. Even so the crispest views came at 225x and 257x. 300x was much better than I expected but it was not showing any new detail of course.

[russ.will]

I've now spent 2-3 hours on each of three nights with the BGO 7 & 9mm and ES 82 8.8mm, all in the AR127L. Considering that the EPs are less than a week old and the scope about two weeks, this must be some kind of cloud dodging record.

First impressions

I've never had an eyepiece turn up in a Jiffy bag, not to mention that fact that is was small Jiffy and there were two EPs in it. Even so, the individual boxes (which are the absolute bare minimum to contain and protect the BGOs) were individually bubble wrapped and then the pair bubbled wrapped again and it still didn't feel as heavy as an item of junk mail.

Digging them out, reveals a pair of featherweight, but nicely made EPs that are otherwise, relatively unimpressive to look at. Until you get up close. A very tidy, smooth sided and internally blackened barrel, adjoins a matt black, billet aluminium cap with crisp inlayed lettering in green and white. Inset into the underside of this cap, is the optical assembly, that gets increasingly jewel like with decreasing focal length. Close inspection reveals lusterous coatings that shine deep green and magenta in impossibly intricate layers. There's not a lot to behold, but what there is is very tidy indeed.

Application

For starters, they're tiny. If you balance your scope with no EP, then adding a BGO makes practically no difference to the status quo. The same cannot be said moving to the BGOs from the ES82s and even less so if one of those ES82s is the 30mm - It alone requires the OTA to be moved up in the rings by 2"+, even compared to the 2" 18mm.

The lack of safety undercut is practically a non issue. They're so light, even the slightest compression ring pressure will stop one from falling out after a meridian flip. As long as you give the thumbscrew even a slight tweak after inserting a BGO, it's unlikely to go anywhere.

Comfort

I don't know if it's because I have quite long eyelashes, but I find EPs with tight eye relief non too relaxing. The ES82 18mm is my least favourite of that crop, for this reason. You have to jam your eyeball right in there to see the fieldstop and then the lashes just seem to get in the way of the view and comfort. The BGOs are actually better for me. The ocular lens isn't recessed, maximising the distance you can maintain and with a much narrower FOV, there's less of a requirement to get up close and personal. Yes, it's still close (a non-starter for specs wearers), but nothing like as close as I had imagined.

The lack of eyecup does make them extremely sensitive to extraneous light sources. Viewing M5 with the moon over my right shoulder was a non-issue with the ES82 8.8mm. When swapping it out for the 9mm BGO, I found myself cupping my hands to shield the (surprisingly) reflective surface of the BGO from the unwanted and highly distracting, incident light source. I may investigate the aftermarket world of eyecups.

Viewing

After three nights, this can only be seen as a set of initial impressions from an owner of UWA eyepieces. Further more, seeing wasn't bad in parts, but stability wasn't brilliant - It was an average set of nights. Add in a near 60-75% waxing moon and DSO targets are limited by contrast, whichever direction you're pointing in. I selected my subjects based on the fact they sat inbetween and clear of the the influence of nearby houses. To the east, south and west of my house, I do have neighbours, but they're spaced out and only one house deep, thereafter being miles of open countryside. Pick subjects above the considerable gaps between these houses and their influence really is minimal. I have progressively trained them all with respect to security lighting!

M5. In the ES 8.8mm it was a tight knot of clear stars, averted vision teasing out a bit more detail and dimensionality. The 9mm BGO seemed to render the same detail, but without averting your visionas much, if at all. You could see the same features as the ES, but the BGO presented them directly, making it much less effort to view. I also missed the considerably wider view of the ES less than I thought I might. Indeed, it's wider FOV brought a couple of brighter stars in to play that were an active distraction. The BGOs framed this subject tightly, concentrating your attention.

M3. Ditto.

Moon. Having had a good scan around with 8.8mm ES to refresh my dwindling short term memory, the 9mm BGO was inserted into the diagonal with much anticipation. It didn't fall short. Okay, it wasn't showing me as much moon as the ES, but quantity isn't always a quality of it's own. For starters, the BGO had a small, but significant sharpness advantage on axis. The extra-crisp delineation of the edges of lunar features had, to use a phrase that I don't like - More pop. They simply looked like they stood out a little more and as a result, a greater appreciation of their relative dimensionality was imparted. Tall stuff looked taller and subtle differences were clearer.

Scanning the relief of craters straddling the terminator, where extreme contrast quite unlike any other astronomical subject exists, was exquisite. The ES gives a pretty good fist of itself, but the BGO removes a layer of uncertainty, rendering the tips of peaks, the walls of craters with razor precision, a 3D texture that a 2D interface has no right to deliver. There was a hint more in the way of shadow detail too, even through the CA the F9 achro throws into the mix, making it seem less of an issue than through the 8.8mm ES.

And that's just on axis. What really impressed me was the way this level of sharpness was delivered throughout the field of view. Of course, UWAs like the ES82s accept certain compromises as a result of the panoramic view that they deliver, the trick being how close it gets across the central portion of it's wide remit. Comparing the portion of the 8.8mm FOV to the area covered by the 9mm BGO reveals a slight fall off in comparison, but nothing verging on unacceptable. The BGO attempts no such wide filed compromise and whilst off-axis encompases a much smaller visual real estate than the ES, by god it's consistent from one edge to the other. Having drunk in the terminator detail, on axis, I slewed the mount from field stop to field stop at 2x speed, watching for the drop off in performance. If it happened, it was right at the field stop and absolutely minimal, if even worth noting. There's just a sharp, dark line where the image stops. Between these extreme points, the field is flat and consistently sharp and indeed, completely certain of focus. If something is in focus, the entire field is.

Saturn is too low in the east at the moment, at least it is by the time I have to hit the sack. Damn.

Interim conclusion

I bought these in an out of character moment of spontaneity, concerned that I would miss out on a last chance to own a legend. Subject to having a few more objects to view and getting to spend some time with them in the 12" F5 Dob, I'm already feeling they were worth the investment, although I'm equally certain I'm not about to flog any of my current EPs because of them, regardless of focal length overlaps. There are plenty of subjects that will take their level of magnification in my scopes and require a larger FOV to fit them in. So they're nice to have alongside the UWAs, but not a replacement. Indeed, if the financial bottom fell out of my world, the BGOs would hit the classifieds first.

No. They add another string to the bow of the EP case for the subjects they suit. They've had me spending hours on the moon, which has previously either been something to end a viewing session with, or something to put me off bothering to go outside altogether. In that respect, the paltry £65 each I paid for them is money well spent. Now, do I pony up a bit more cash for the 6mm whilst it's still out there?

Russell

[John]

Thats a great review Russell - I really enjoyed reading it

I think you are right - there is some sense in having a few good orthos and ultra wides in the eyepiece case, if you can run to it.

[Qualia]

Ay, a beautiful and well constructed review, Russell and thank you for taking the time. In answer to the final question, I can only answer yes.

[alan potts]

Russell,

A very nice and well written report, seem I will have to froget the 7mm for the time being then. I agree even having not used them they are to compliment others not to replace. I would no way ever replace my 6mm Delos ( if it was not broken ) with the 6mm BGO, but for a short while it will be doing.

Alan.

[Stargazer_00]

Great read, Russell. I'm full of mixed feelings from reading it. I'm glad I didn't buy them when I was in the shop now because that's a great review and you got a lot of enjoyment out of them and that's great, but now you've gone and sold them to me I wish I had them!

Seriously though, great review. eloquent as always. thanks