BGO - different focus point.... Confused!

[Stu]

I've just received this very nice 18mm Baader Genuine Ortho from another member. It performs as you would expect, but I'm confused by its focus point which is about 5 to 6mm farther out than my existing one. Wouldn't be a problem but I intended to use them in a binoviewer and this makes it a bit uncomfortable.

The embossed writing, both white and green is different on the piece I've just relieved; a darker green and generally a bit thicker I think.

Is anyone aware of differences between batches like this? I assumed all BGOs were made equal? Means I will have to check more carefully next time....

[Louis D]

Time to buy a third and hope it matches one of the two you already have and then sell the odd man out.

[John]

Looks it might be from a different production run Stu. I thought they were all alike as well though. Some of the Japanese clones such as the Fujiyama orthos do have shorter black body sections so there is around 6-8mm difference in their focal plane position but I thought all the BGO's were the same

[spaceboy]

This is the only thing that put me off BGO and later the Astro hutech. Superb views but not par focal across the range and some of the shorter focal lengths ate up inward travel. As John said they were probably from different production runs. Not being par focal I doubt there was much importance to make runs with identical focal points if tooling or supplier changed ???? Not much good for BV's if that is the case. If you did decide ortho were the way to go I can recommend the Fujiyama's which are (to my eye anyway) as good as the BGO's and being par focal may make life easier if you don't have much focus travel to play with.

[Dude_with_the_tube]

i had 2 sets of BGO`s Stu and i didnt had this issue,nor with Denks,nor with my current ones.I would  agree with John,that this might be the case of different runs as both EP`s look slightly different.(is it me or it is the angle of the pic,but also the tops of the Ep`s look slightly different?? )

When binoviewing it is critical to have both Ep`s from same run.However,i wasnt aware that there where multiple runs of BGO`s .We learn something new every day. I moved away from BGO`s for binoviewing due to them being flat tops and they just felt "cold" to face when observing and wasnt comfortable for my liking, if you know what i mean.However,for solar binoviewing 18mm where perfect as you observe during the day.And obviously in solo BGO`s are cracking orthos.

 

 

[Dude_with_the_tube]

2 hours ago, spaceboy said:

This is the only thing that put me off BGO and later the Astro hutech. Superb views but not par focal across the range and some of the shorter focal lengths ate up inward travel. As John said they were probably from different production runs. Not being par focal I doubt there was much importance to make runs with identical focal points if tooling or supplier changed ???? Not much good for BV's if that is the case. If you did decide ortho were the way to go I can recommend the Fujiyama's which are (to my eye anyway) as good as the BGO's and being par focal may make life easier if you don't have much focus travel to play with.

would like to know what parfocal issue of single EP  and different focal length in cyclops mode has to do with binoviewing?

[spaceboy]

38 minutes ago, Dude_with_the_tube said:

would like to know what parfocal issue of single EP  and different focal length in cyclops mode has to do with binoviewing?

For 2 reasons in my mind. 1) Might sound trivial but every time you want to change magnification in BV's your already fussing about in the dark taking out 2 eyepieces then putting in another 2 so if they are par focal your near enough on focus once done.  2) If you struggle with inward focus as many BV's do, and you find a particular ep works if there is next to no focusing required between ep changes then you know other focal lengths in that range should also work.

I am wondering if Baader did 2 versions of the BGO as in my experience mine were not par focal yet I did read some reviews to the contrary. I am wondering if you have picked up one that is and one that isn't Stu ?? Are your other BGO parfocal ??

[Dude_with_the_tube]

16 hours ago, spaceboy said:

For 2 reasons in my mind. 1) Might sound trivial but every time you want to change magnification in BV's your already fussing about in the dark taking out 2 eyepieces then putting in another 2 so if they are par focal your near enough on focus once done.  2) If you struggle with inward focus as many BV's do, and you find a particular ep works if there is next to no focusing required between ep changes then you know other focal lengths in that range should also work.

I am wondering if Baader did 2 versions of the BGO as in my experience mine were not par focal yet I did read some reviews to the contrary. I am wondering if you have picked up one that is and one that isn't Stu ?? Are your other BGO parfocal ??

First of all BGO`s are parfocal,with only slight adjustment of focuser required. (we are talking mm and not inches) However,Ep`s being parfocal DOES NoT affect them being used in binoviewer. Parfocal meaning is that you will not need to re-focus or in some cases slight adjustment will be required when you change to a different focal length EP,but even EP being NON parfocal,2 identical ,same focal length Ep`s should still work in BV.  I,for example,use Meade research grade what are not parfocal and i cant say that there is an issue with that.Slight adjustment doesnt really bother me if i change to another pair.

Secondary,when binoviewing,you dont really change your pairs that often as there is simply no need for change.And as much as it sounds complicated,with new models of BV  having a click-lock or similar system,it doesnt really take that much of a fuss to do it.I would say the same amount of time as you do in single EP mode.On top,you dont really use or change that many pairs of Ep`s in binoviewer anyway.Maximum will be 3-4 pairs in total what you will use.Could also be only 2 pairs+ GPC/OCS/barlow/powermate

And lastly.Your point will only partially apply if you are trying to use your telescope and binoviewer in "native" mode without the aid of GPC,OCS or barlows/powermates,and even then,refocusing distance between different focal length Ep`s will be relatively small and will not affect anything.(same producer/series of Ep`s) Most likely an optical aid like GPC/OCS/barlow/powermate will be used and as such you will have sufficient inward/outward travel anyways in most cases.

I am not aware of multiple runs of BGO`s and i have never heard that people are struggling with BGo`s in BV,as such i am more declined to think that there is an issue with one of the 18mm Ep`s itself.Could be manufacturing issue ,could be something else.My suggestion would be to try and pick up another 18mm BGO and see if the new one matches up with one of the existing ones.

Clear skies

[John]

When the Baader GO's went off the market the reason generally given was that the manufacturer had been hit by the Tsunami / Earthquake I recall.

We all mourned the passing of these excellent eyepieces and for a short while the used price for them skyrocketed. Thankfully it settled back to more sane levels reasonably quickly.

Not too long after that (within a year or so ?) eyepieces bearing remarkable similarities in design, fit, finish and performance to BGO's appeared branded Astro Hutech, then Fujiyama and then University Optics (the new run of HD orthos). One principle difference between these was the focal plane position. The Astro Hutech's were mostly par focal with the Baader GO's except for the 6mm and 18mm as I recall. The Fujiyama versions were very close to a par focal range and reached focus uniformly around 8mm further out than Baader GO's and most of the Astro Hutech range.

I did wonder back then if in fact more than one Japanese manufacturer was originally licenced and tooled up to produce the Baader GO's but perhaps due to demand levels Baader stuck with the one factory for the majority of production. When that manufacturer was hit by the natural events, Baader decided to drop the range and sourced the Chinese made (to a Zeiss design) Baader Classic range in it's place.

The other manufacturers were then free to start production of the Baader GO types again but under marketing agreements with other brandings.

This is why I wonder if Stu's 18mm Baader GO's were actually out of different manufacturers, the regular one and then an occasionally used one ?

The odd thing is that Baader are usually pretty particular about specifications and would, I'd have thought, have included the focal plane positioning within the spec of eyepieces produced by another manufacturer to ensure par-focalilty with others in the range.

All pure supposition of course - apart from the physical and performance similarities of the eyepieces and the timing of their appearance on the market, I've nothing to substantiate any of this !

I guess it will remain a mystery

[bingevader]

Were they very expensive ?

Would it possible to alter the position of the lens sets within the body of the eye piece ?

I suppose it would alter the eye relief too, but would mean they were both the same height externally.

Just a thought.

[spaceboy]

I think they were around £89 new Ben and used could be picked up for £50

3 hours ago, Dude_with_the_tube said:

First of all BGO`s are parfocal,with only slight adjustment of focuser required. (we are talking mm and not inches) However,Ep`s being parfocal DOES NoT affect them being used in binoviewer. Parfocal meaning is that you will not need to re-focus or in some cases slight adjustment will be required when you change to a different focal length EP

I beg to differ regards them being par focal. While I didn't have the 12.5 & 18mm I did have the 5,6,7,9mm and the 6mm was no where near the same focal point as the others and would not even come to focus in my EVO it required so much inward focus. I admit the 5,7,9 weren't a million miles apart but no where near as close focusing as their Fujiyama replacement. And I didn't say being par focal affected them being used in BV's?? I said they would be near the same focus so less fussing. IE: better than an eyepiece that may require several turns of a focusing knob. Peoples experiences differ due to different kit so we will have to agree to disagree on BV's being a fuss to use. I admit they are great to look through offering far more comfortable viewing than squinting with one eye but they just weren't for me.

 

2 hours ago, John said:

When the Baader GO's went off the market the reason generally given was that the manufacturer had been hit by the Tsunami / Earthquake I recall.

We all mourned the passing of these excellent eyepieces and for a short while the used price for them skyrocketed. Thankfully it settled back to more sane levels reasonably quickly.

 

Supply and demand will always drive some people to desperation. I remember the same thing happening with the SPC800 when Morgans stock ran out. You could buy one from them for £6 at one time but they were selling for almost £90 on ebay when the supplies dried up. Even now they can sell for £50 used. I think the most I'd seen a used BGO sell for was £130. Fantastic eyepiece for £50 used but £130 you would need you head looking at. I think some Pentax XW's were selling for around £155 at the time so I know where my money would have gone.

 

Stu are you on cloudy nights?? Those yanks love BV's an aren't short of a few cases full of eyepieces. (they put our show us your eyepiece case thread to shame) Might be worth opening a thread on there to see if any issues have arose ??

[Paul73]

You might be better off going for a new pair of BCO. The image quality is very similar and the supplier could check the batch.

You could be fishing for matching BGO's for ever. And, you get a 50° FOV with the BCO.

I had the 18mm BCO. I liked it so much that I bought the rest of the range.

Paul