Recently, I received a set of GSO 30mm and 42mm SuperView eyepieces from Owl Services and noticed that the 30mm eyepice is taller than the 42mm. Checking some of the threads here, it would appear there are two different versions of the 30mm eyepiece floating around. One is just over 4" tall while the other is close to 5" tall.
The tall 30mm and 42mm eyepieces that I got aren't close to being parfocal and I have to rack up the focuser quite a bit when interchanging these eyepieces. Wondering if the shorter version of the 30mm is any better?
Cheers!
Rolly
Is your GSO 30mm and 42mm parfocal?
Started by
Guest_**DONOTDELETE**_*
, Jun 10 2004 11:38 AM
6 replies to this topic
#2
Guest_**DONOTDELETE**_*
Guest_**DONOTDELETE**_*
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topic starter
Posted 30 June 2004 - 12:10 AM
Okey dokey, so where shall I begin. Well, how about I purchased another GSO 30mm 2" eyepiece from another vendor to find out what was going on.
Well, after winning the Ebay auction and waiting patiently it has finally arrived and I am now the proud owner of two GSO 30mm 2" eyepieces but which one is the real Mckoy. Will the impostor be rooted out and sent off to astromart land. Or will it seduce and enslave its ocularholic owner. Stayed tuned to another exciting episode of "Ocular Wars: Invasion of the Clone".
Ok, enough of that. I've attached photos that appear to suggest that these are totally different eyepieces but on closer inspection it doesn't appear to be the case. After unscrewing the bottom metal skirts and peering inside, I noticed that both eyepieces use the same optical design except the taller eyepiece has it's optics further recessed into the eyepiece housing. By eyeballing it from the top of the eyepieces to the retaining rings the optical train looks to be the same in length in both eyepieces.
So what's the difference between these when put into a scope? Well, not much, except that the taller eyepiece isn't parfocal with the other GSO 42mm where as the shorter one is. Also, after spending a night going back and forth I did notice that the taller eyepiece had a slightly narrower FOV that I would guess to be about 2 to 3 degrees as compared to the shorter 30mm.
Overall, both eyepieces are outstanding values and perform far beyond their asking price. Having an eyepiece case that includes Naglers, Panoptics and a Radian, I'm not easily impressed. However, the GSO 30mm and 42mm eyepieces are making a home beside my Tele Vues. Sure, the GSOs don't deliver the ultimate in edge performance but they got sharpness and contrast in spades.
Cheers!
Rolly
PS: The tall 30mm is now making its way to astromart land
Well, after winning the Ebay auction and waiting patiently it has finally arrived and I am now the proud owner of two GSO 30mm 2" eyepieces but which one is the real Mckoy. Will the impostor be rooted out and sent off to astromart land. Or will it seduce and enslave its ocularholic owner. Stayed tuned to another exciting episode of "Ocular Wars: Invasion of the Clone".
Ok, enough of that. I've attached photos that appear to suggest that these are totally different eyepieces but on closer inspection it doesn't appear to be the case. After unscrewing the bottom metal skirts and peering inside, I noticed that both eyepieces use the same optical design except the taller eyepiece has it's optics further recessed into the eyepiece housing. By eyeballing it from the top of the eyepieces to the retaining rings the optical train looks to be the same in length in both eyepieces.
So what's the difference between these when put into a scope? Well, not much, except that the taller eyepiece isn't parfocal with the other GSO 42mm where as the shorter one is. Also, after spending a night going back and forth I did notice that the taller eyepiece had a slightly narrower FOV that I would guess to be about 2 to 3 degrees as compared to the shorter 30mm.
Overall, both eyepieces are outstanding values and perform far beyond their asking price. Having an eyepiece case that includes Naglers, Panoptics and a Radian, I'm not easily impressed. However, the GSO 30mm and 42mm eyepieces are making a home beside my Tele Vues. Sure, the GSOs don't deliver the ultimate in edge performance but they got sharpness and contrast in spades.
Cheers!
Rolly
PS: The tall 30mm is now making its way to astromart land
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#3
Mike Hosea
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Posted 30 June 2004 - 12:55 AM
I can't think of a good reason to recess the lenses farther (that just takes up in-travel), and the shorter one pretty much parfocal with the 42mm, so I suspect there was some screw up at the machine shop, like cutting the outsides to the same dimensions as the one that has a 50mm+ focal length. Probably what you see now with the 30mm is the result of somebody saying, "No problem, just put the lenses in and sell them like that." What do you think?
#4
Guest_**DONOTDELETE**_*
Guest_**DONOTDELETE**_*
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topic starter
Posted 30 June 2004 - 09:37 AM
That seems to make sense since the tall 30mm appears to be the same dimensions as the 50mm eyepiece but I can't confirm this.
Also, I contacted Tom Roginski from Owl Services and asked why his Ebay ads have size specs that are different from the one that I received. This was his response "Recently they increased the size of the rubber eye cup very slightly and the barrel length slightly. This makes the group now par focal or nearly so. All other specs should be the same." Based on my own experience that is definitely not the case. Heck, the short 30mm and the 42mm are pretty close to being parfocal with my Tele Vues. However, the tall 30mm is way off, so much so it becomes a bit of a pain.
FYI - I got the tall version from Owl Services while the short one came from an Ebay seller called adastra4ync.
Cheers!
Rolly
Also, I contacted Tom Roginski from Owl Services and asked why his Ebay ads have size specs that are different from the one that I received. This was his response "Recently they increased the size of the rubber eye cup very slightly and the barrel length slightly. This makes the group now par focal or nearly so. All other specs should be the same." Based on my own experience that is definitely not the case. Heck, the short 30mm and the 42mm are pretty close to being parfocal with my Tele Vues. However, the tall 30mm is way off, so much so it becomes a bit of a pain.
FYI - I got the tall version from Owl Services while the short one came from an Ebay seller called adastra4ync.
Cheers!
Rolly
#5
jmoore
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Posted 30 June 2004 - 10:28 AM
hmmm...this kinda bums me out. My 30mm is the tall version...also from Owl services. As noted above, my 30mm and 42mm are not parfocal. Sounds like the shorter version is much more desireable, especially if you also have the 42mm (for parfocal reasons, and also if the shorter version has a little wider FOV).
I just sold my 30mm on AM (am keeping the 42mm for now). I wonder though, would I be selling this 30mm off if I'd gotten the "better" version? Probably so, in which case this is moot, but who knows...maybe I would have liked it enough to keep it then.
Fact is, though, I just don't see myself using 2" EPs much with my current scopes. I only kept the 42mm because it gives me the widest true FOV I can possibly get for my current budget, so in those rare circumstances when I *need* 2.3 degs FOV from my 8" scope, now I have the option. [With my 1.25" EPs, I can get 1.7 degs, which is ample. The 30mm GSO would have given me about 2.0 degs...not a significant enough FOV gain to justify the annoyance of swapping out adaptors to switch between 2" and 1.25" barrels].
I just sold my 30mm on AM (am keeping the 42mm for now). I wonder though, would I be selling this 30mm off if I'd gotten the "better" version? Probably so, in which case this is moot, but who knows...maybe I would have liked it enough to keep it then.
Fact is, though, I just don't see myself using 2" EPs much with my current scopes. I only kept the 42mm because it gives me the widest true FOV I can possibly get for my current budget, so in those rare circumstances when I *need* 2.3 degs FOV from my 8" scope, now I have the option. [With my 1.25" EPs, I can get 1.7 degs, which is ample. The 30mm GSO would have given me about 2.0 degs...not a significant enough FOV gain to justify the annoyance of swapping out adaptors to switch between 2" and 1.25" barrels].
#6
Relativist
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Cosmos
Posted 30 June 2004 - 09:42 PM
I have the problem that I can't thread the 2" barlow into the 42mm but I can into the 30mm, anyone else try that?
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#7
Mike Hosea
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Posted 30 June 2004 - 10:12 PM
I had no problem with it (other than not liking the vignetting). The threads were all the same on mine.
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