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BST Explorer/Starguider


Steve91

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40 minutes ago, bingevader said:

:shocked:

Is the 6mm WO SPL not a totally splendid EP then!?

Mine is ;)

Maybe better than splendid.
I don't have an issue using the 6mm even bought the 12, but the six came first, highly recommended and discounted, infact second hand, so I took a chance, with no regret.
Even tried to buy one (3mm) off e-bay for nearly four Months, the vendor just wanted too much, more than FLO's sale price, and would not give an inch!

There are several eyepiece companies that don't/won't have  every focal length in their  inventory, its just my wish to have the 6mm Starguider to complete 'my' set although the set itself is already complete.

As a minimum one really only needs three EPs based around the focal ratio of the Skyliner f/6?  For me now that would equate to a 3, 6 and 12mm so the WO SPL's fit that criteria. 6mm matches the focal providing 200x power + 1mm exit, with the 3 & 12mm offering one up - one-down either side, 0.5 & 2mm exits, perfect for my planets ( when I get to see them? )

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Barsta, who I believe manufacturer these eyepieces, don't list a 6mm and, as far as I know, never have:

http://www.barsta.com/show_hdr.php?xname=MDA8V11&dname=OPFOR71&xpos=13

The first I saw of this design was under the Astro Tech Paradigm branding back in 2009 when this review appeared on the Cloudynights forum:

https://www.cloudynights.com/articles/cat/cn-reports/eyepiece-reports/first-look-astro-tech-paradigm-eyepieces-r1845

Again, no 6mm listed there.

I wonder if the mythical 6mm ever existed :icon_scratch:

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No 6mm they were initially 5, 8, 12, 15, 18, 25, then they added a 3.2mm about 2 years back.

Always thought that a 4mm and a 6mm and maybe not the 3.2mm would have produced a better set. Would have been a nice group for planets.

The WO 6mm is very good as an alternative.

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Apart from the Tele Vue Plossls that were loaned to me (@Ghostdance  ) I have never looked through any of the eyepieces in my signature prior to purchasing, despite our best interests and advice for folk  to join a club and have a look. All my EPs were bought on recommendations, and good they were. The 8mm Starguider was my first BST.

I even bought the Delos just to trial the 8mm version, but their not for me now, likewise the Meade  4000 Plossl's are away, its just a matter of personal choice and what you like/dis-like. 

If I can get the time/conditions soon, I will try to test the full set of SPLs against the BCO's, and the winners stay. I'm sure I can strike a good deal for a full set, if that option arises.
 

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15 minutes ago, bingevader said:

So, what makes you think the 12mm BST Starguider hits an even sweeter spot?

......from the theory I have adopted and suggestions from  other users who share the same view and understanding,  and the fact that it just feels more comfortable for me, with a sharper although smaller image?


Its said that all scopes have an optimal setting and  under the right conditions, the user is confronted with the best the telescope can provide.
Everything will still subjective between different folk, no matter what I write, and there will never be a situation where it can't get any better, if you use x,y & z.

From all the previous tests, facts and results, some eyepieces will work better for  certain folk given certain parameters, and a few of those parameters result in data  that perfectly matches the telescopes data sheet, quite often stuck on the body of the scope next to the focuser. 

The focal length  of the scope divided by the aperture of the scope, all basic stuff results in  the focal ratio of the scope. 

If the 6mm provides me with 200x I will achieve the highest  practical magnification that my scope was designed for with a 1mm exit pupil.
Its been said many times, and the why I have adapted to it, is that anywhere between 0.5 ~ 2mm is about right for the majority of folk when viewing the Planets. 
If I use higher power using the 3mm I'll reduce the brightness due to the smaller exit pupil, the image will have less detail, due to the magnification, and just not as good an image compared to the 6mm.
Heading the other way, the 12mm allows for a bigger exit pupil, brighter image, more detail, but alas a smaller image ( the reason for some time I wanted a 12" or 10" Skyliner).
I have read many times  over, the feelings that folk have experienced  when  hitting their 'sweet spot'....... and its often or extremely close to when using an eyepiece that is twice or roughly twice the focal ratio of the scope in use,  and for this reason/theory alone, and the fact that I too sense that something is better/different, its the  reason I said the 12mm was sweeter.

That all said, your earlier comment ...........The 6mm does seem to hit a sweet-spot in the 8", 1200mm dob. ;)  It was my impression that you were referring to the William Optic  6mm  that I own as a substitute for the non-existent Starguider. I then came back saying ........ I feel that  a 12mm is sweeter   again referring to the WO SPL.


Can I also make it quite  clear, that brand specific  is not of  any importance here, its the size of the eyepiece that is important. Your mention of   " you think the 12mm BST Starguider hits an even sweeter spot? "   was not what I said or meant to say, NO! ......Its not the Starguider itself, its the focal length, 12mm, any brand you prefer,  is/will be sweeter than my 6mm, Sorry if I misguided you. 

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On 13/04/2017 at 12:59, Charic said:

I still require that elusive 6mm?

 

On 13/04/2017 at 14:25, FLO said:

I'll see what I can do. 

 

On 13/04/2017 at 14:44, Charic said:

It would be great to have one.

 

On 13/04/2017 at 17:28, John said:

I wonder if the mythical 6mm ever existed :icon_scratch:

 

On 13/04/2017 at 17:37, Charic said:

It. doesn't, at least from my investigation and sources,  thats why I want one. 

 

Ah, then it is unlikely we will find one :biggrin:

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Never say never, I'll tell Barsta to provide you with one specifically for Charic, if that were possible! I'd be the proud owner, and FLO would be the No1 retailer.
Similar to the Tele Vue 6mm Plossl, not sure anyone has one, or Tele Due will ever build one?
Sorry if I've  inconvenienced you or your time  for the BST 6mm, although some retailers  may have more clout/persuasion with the manufacturers.

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5 minutes ago, Charic said:

I hope thats not photo-shopped John?

Now would I do that to you ? :angel12:

More seriously, I reckon the SPL 6mm will do an excellent job for you in that niche :thumbright:

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The 6mm is a fine EP John, and fortunately for me, I now have the full set! although do I really need 4 eyepiece sets ? 
I have had very little use of many of my EPs over the last Year, as  too have so many other users, due to the poor conditions of late, and I don't provide the wonderful service that you  meticulously take so much time over, helping others with their eyepiece choices, so it was time to decide, and make a few changes to my setup. The Meade 4000's  are still on auction as are my Delos, we'll see what happens next with the remaining sets?
After all, most of my eyepieces were for comparison/testing, to see what I like, and to offer something back should someone want to compare Starguider, Delos, Meade, Revelation, SPL ect.

The WO6mm will stay for now, but if its ever sold? it will probably go as a set. Likewise  with the Baaders. 

I'm not sure the Starguiders will ever leave this scope as it stands. The Plossls were bought to complete my desire to own a Plossl set, and with their larger focal range, I opted for the Revelations, right or wrong, over the accepted better quality Tele Vue plossls, but  as always, its down to the individual and their own personal choice as to whats best.

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11 hours ago, Charic said:

Can I also make it quite  clear, that brand specific  is not of  any importance here, its the size of the eyepiece that is important. Your mention of   " you think the 12mm BST Starguider hits an even sweeter spot? "   was not what I said or meant to say, NO! ......Its not the Starguider itself, its the focal length, 12mm, any brand you prefer,  is/will be sweeter than my 6mm, Sorry if I misguided you. 

Sorry, my sense of humour! My apologies if you thought I inferred that you meant the BST Starguider, I was just trying to keep us on topic! :D

Yes, I knew about the focal length, magnification, exit pupil assumption, which is why I assumed the 6mm hit the spot.

Never really used a 12mm on the planets, if the seeing is that bad that I need to drop back to the 12mm, I usually give up. I'll try again! :)

But now that we mention it and drifting completely off topic, for DSOs the 14mm seems to hit a sweet spot in the 8", 1200mm also! Is there a theory for that one too?

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In someones methodology yes, there will be a theory!

Whatever the eyepiece in use, that gives the user that special moment, could be called their sweet spot EP, this will be an individual thing as we are witnessing here. But the target itself, the viewing conditions, the telescope and its setup/collimation, and lastly the individuals eyes will always determine what/which eyepiece is best for  their sweet spot for that moment in time.

My ground rules and recommend for newcomers  are twice, equal and half the telescopes focal ratio in that order for their initial or replacement eyepiece selection, but I would add a low powered eyepiece before buying the eyepiece that is half the focal ratio, as half the ratio will get little use, and would  be at the extreme of what the scope is capable of achieving.



 

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2 hours ago, bingevader said:

But now that we mention it and drifting completely off topic, for DSOs the 14mm seems to hit a sweet spot in the 8", 1200mm also! Is there a theory for that one too?

Yes. I have seen somewhere a graph of exit pupil vs aberration size. On that graph were two lines; diffraction, which dominates at low exit pupils, and aberrations caused by your eye lens, which dominate at large exit pupils. The point at which the two lines crossed, signifying the minimum observable aberration/the sharpest image, was at 2.4mm which equates to a 14.4mm eyepiece in an f6 scope. Of course, different studies find slightly different results and so generally anywhere in the 2-3mm region is typically stated as the "optimum" exit pupil. 

I have also seen it stated that the best corrected part of your eye lens is the central 2-3mm, which corresponds to the typical size of your pupil during the day. Eyepieces between 12 and 18mm sit in this region for an f6 scope. 

I personally use a 14mm eyepiece in an f6 spotting scope during the day. I have found this combination the most comfortable to use as it seems to minimise the brightness difference between observing through the scope and without, compared to say a 12mm eyepiece which is a little dimmer than the nominal daytime brightness and therefore needs that moment of readjustment when moving to or from it. 

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7 hours ago, Ricochet said:

Yes. I have seen somewhere a graph of exit pupil vs aberration size. On that graph were two lines; diffraction, which dominates at low exit pupils, and aberrations caused by your eye lens, which dominate at large exit pupils. The point at which the two lines crossed, signifying the minimum observable aberration/the sharpest image, was at 2.4mm which equates to a 14.4mm eyepiece in an f6 scope. Of course, different studies find slightly different results and so generally anywhere in the 2-3mm region is typically stated as the "optimum" exit pupil. 

I have also seen it stated that the best corrected part of your eye lens is the central 2-3mm, which corresponds to the typical size of your pupil during the day. Eyepieces between 12 and 18mm sit in this region for an f6 scope. 

I personally use a 14mm eyepiece in an f6 spotting scope during the day. I have found this combination the most comfortable to use as it seems to minimise the brightness difference between observing through the scope and without, compared to say a 12mm eyepiece which is a little dimmer than the nominal daytime brightness and therefore needs that moment of readjustment when moving to or from it. 

That probably explains why the first Nagler was a 13mm as was the first Ethos. Al Nagler knows his stuff :smiley:

 

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On 14/04/2017 at 22:24, Charic said:

I'm not sure the Starguiders will ever leave this scope as it stands. The Plossls were bought to complete my desire to own a Plossl set, and with their larger focal range, I opted for the Revelations, right or wrong, over the accepted better quality Tele Vue plossls, but  as always, its down to the individual and their own personal choice as to whats best.

I'm a bit confused over the above. As you can see from my signature, I have a few of the Explorer branded BST eyepieces. Am I reading the above correctly? I thought that the BSTs' were Plossls. The above seems to me to say they aren't. Or am I reading the above statement incorrectly?

 

Mark

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24 minutes ago, trynda1701 said:

I'm a bit confused over the above. As you can see from my signature, I have a few of the Explorer branded BST eyepieces. Am I reading the above correctly? I thought that the BSTs' were Plossls. The above seems to me to say they aren't. Or am I reading the above statement incorrectly?

 

Mark

BSTs are a negative/positive design like the Vixen LV/NLV/SLV/LVW, Pentax XW, Naglers, ES-82, etc. while plossls are strictly a positive-only design.  Here's a Televue diagram showing the difference between the two design types.  The BST design actually looks like this (the eye looks in from the left side).

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Hmm, interesting. So what type of eyepiece type should I call my BSTs', other than the negative/positive type, if not Plossl? Are they classed as Nagler-like, without being Nagler? The same way I thought my ES Maxvisions were Plossl, but are actually a Panoptic clone?

 

Mark

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