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A 30mm 100 degree 3 inch barrel in the works!

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#1 Darren Drake

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Posted 06 November 2012 - 10:12 PM

Scott Roberts is reporting on FB that he will soon be field testing one of these. There is a pic and it is enormous. Wow now SI or someone is gonna have to start making more 3 inch focusers for dobs....

#2 Keith

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Posted 06 November 2012 - 10:18 PM

He mentioned that a few years ago, but it I was sworn to secrecy on that. It was at the time being discussed as going with a 3" diagonal for larger SCTs that was also possibly going to be supplied by ES.

Now that the cat is out of the bag, I guess it is ok for me to say "I know"

I hinted about it on the "lowest X for cpc1100" thread recently, but would not say more out of respect to Scott. I am no longer in a position to find out such things anymore anyway, this was a few years ago, guess it was a slow moving process.

#3 Keith

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Posted 06 November 2012 - 10:38 PM

I went straight to FB to see...

#4 Darren Drake

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Posted 06 November 2012 - 11:40 PM

So how much will this go for?? $1500 is my guess....

#5 Jon Isaacs

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Posted 06 November 2012 - 11:41 PM

Scott Roberts is reporting on FB that he will soon be field testing one of these. There is a pic and it is enormous. Wow now SI or someone is gonna have to start making more 3 inch focusers for dobs....


Won't be of much use in a fast Dob until someone makes a 3 inch Coma Corrector... The modern F/3 Dobs are using the 21mm Ethos as the widefield because the 31mm Nagler results in an oversized exit pupil...

Jon

#6 Darren Drake

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Posted 06 November 2012 - 11:52 PM

Right only scopes slower than about f/5 could really benefit from this and perhaps only refractors.

#7 SeattleScott

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Posted 06 November 2012 - 11:57 PM

The problem with a 3" eyepiece is then you need a bigger secondary, which means lower contrast and light transmission. Maybe for a large aperture scope it would be ok, but there is going to be that compromise. I believe the CO on an 11" SCT is almost 4" already. Do you really want to make it 5" to get a wider field of view? Maybe on an F5 18" dob it would work well. But then you have to balance what looks like a 5-lb eyepiece!

I don't know, I do not see a lot of interest in this outside of observatories that use larger than 2" eyepieces for their huge telescopes. But it is fun to think about!

#8 Keith

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Posted 07 November 2012 - 12:02 AM

scott says $12-1500. And it would probably do well in C11/14 and M10/12/14/16 with proper adapter. Only rub is the c11/14 thread is slightly different than the m10/12/14. It looks like they are planning this mainly for their refractors, but when Scott told me about the idea a few years ago, it sounded like a 3" diag to thread to the 3" thread on the back of the larger SCTs and coma free cats was going to be included with the eyepiece.

As I posted comment on FB, I hope this would lead to other 3"ers, such as a 40mm range 82 or more importantly, a 50mm range 68. Would make the c11 a little more interesting, unless the rear baffle limits it. At f10 there is some leeway, but I think it is about 2.5" clear aperture, but I would have to measure. Either way, a 30mm 100deg is probably not using the full 3" anyway, and I have not ran numbers on any of those theoretical others.

Being f10, I personally would like to see wider 40 and 50mm designs in 3 inch, if a diagonal was available. In the old days, there was a thread on 3" eyepiece for the old 3" c14 diagonal, so I know this has been thought of before, not to mention the pentax 65mmXL.

#9 Jon Isaacs

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Posted 07 November 2012 - 12:11 AM

The problem with a 3" eyepiece is then you need a bigger secondary, which means lower contrast and light transmission. Maybe for a large aperture scope it would be ok, but there is going to be that compromise. I believe the CO on an 11" SCT is almost 4" already. Do you really want to make it 5" to get a wider field of view? Maybe on an F5 18" dob it would work well. But then you have to balance what looks like a 5-lb eyepiece!

I don't know, I do not see a lot of interest in this outside of observatories that use larger than 2" eyepieces for their huge telescopes. But it is fun to think about!


I could use the added field of view in my 25 inch F/5, the 31mm Nagler without a Paracorr provides about 0.80 degrees, a 30mm 100degree eyepiece would provide about 0.95 degrees... significant but not significant enough to deal with the hassle of balance and adding a 3 inch focuser.

The usefulness of an eyepiece like this is somewhat dubious in the sense that it is not so useful in scopes that are already optimized for a wide field of view. It would be great in my 12.5 inch F/4.06 if there were a Paracorr available but without one, it would not be workable. The beauty of TeleVue products is the integrated solutions, a Paracorr that works with the 31mm Nagler... The NP series that provide wide flat field so that the 31mm nagler can show it's stuff.

Of course the 106 FSQ would provide some amazing views if the eyepiece were sharp at F/5.

Jon

#10 Rick Woods

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Posted 07 November 2012 - 12:17 AM

Scott Roberts is reporting on FB that he will soon be field testing one of these. There is a pic and it is enormous. Wow now SI or someone is gonna have to start making more 3 inch focusers for dobs....


I'm sorry; what are "FB" and "SI"?

#11 core

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Posted 07 November 2012 - 12:19 AM

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#12 Scanning4Comets

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Posted 07 November 2012 - 12:50 AM

Holy moly! That thing needs a crane just to put it in the focuser. :lol:

#13 Shneor

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Posted 07 November 2012 - 02:42 AM

Scott Roberts is reporting on FB that he will soon be field testing one of these. There is a pic and it is enormous. Wow now SI or someone is gonna have to start making more 3 inch focusers for dobs....


Won't be of much use in a fast Dob until someone makes a 3 inch Coma Corrector... The modern F/3 Dobs are using the 21mm Ethos as the widefield because the 31mm Nagler results in an oversized exit pupil...

Jon

Not necessarily true. The 9mm ES120° shows pinpoint stars from center to edge in my f/4 without any correction needed. It apparently has a quite different design. Unfortunately, as far as I know, only three CN members have one of these, but several observers have viewed through mine. All were amazed by the sharpness across the entire field.

Clears,
Shneor

#14 Keith

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Posted 07 November 2012 - 04:54 AM

how much for your 9mm ES100? =)

#15 Mark9473

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Posted 07 November 2012 - 07:15 AM

Siebert has been offering large format eyepieces and diagonals for years. I wonder why ES think they will be more successful with it.

#16 Jon Isaacs

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Posted 07 November 2012 - 07:44 AM

Scott Roberts is reporting on FB that he will soon be field testing one of these. There is a pic and it is enormous. Wow now SI or someone is gonna have to start making more 3 inch focusers for dobs....


Won't be of much use in a fast Dob until someone makes a 3 inch Coma Corrector... The modern F/3 Dobs are using the 21mm Ethos as the widefield because the 31mm Nagler results in an oversized exit pupil...

Jon

Not necessarily true. The 9mm ES120° shows pinpoint stars from center to edge in my f/4 without any correction needed. It apparently has a quite different design. Unfortunately, as far as I know, only three CN members have one of these, but several observers have viewed through mine. All were amazed by the sharpness across the entire field.

Clears,
Shneor


We have been through this one before with other eyepieces... The 30mm Widescan II comes to mind.

Coma is there to be seen at F/4, the coma free region is 1.4mm, the approximate field stop diameter of the 9mm 120 degree eyepiece is 19mm, that's a lot of room for coma. I have a hard time believing moving a bright star like Rigel to the edge of the field would provide a nice round and still clean primary and secondary.

If an eyepiece truly eliminates coma in an F/4 Newtonian, then the reverse coma necessary to do so would be visible in a coma free telescope...

Jon Isaacs

#17 Sarkikos

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Posted 07 November 2012 - 08:09 AM

So, a 3" eyepiece might make sense in big SCTs which are not yet available, big slow refractors and marginally in 25" Dobs?

Eh... :shrug: I think I'll pass.

Mike

#18 Keith

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Posted 07 November 2012 - 08:17 AM

people's tolerance or ability to detect coma varies greatly. Once the astigmatism found in the more basic designs is gone, most people are happy, and really picky folks start to notice the coma. I also found MANY people like to use the word coma to describe any edge of field abberation, and some even use the word to describe "feild curvature in newtonians". Even fairly knowledgeable guys I have known, maybe they just wanted to make the explanation simple.

In my experience, the elimination of the rest of the abberations, coupled with the barlowing effect of the nagler type eyepieces, makes most people happy, especially when upgrading from eyepieces like said widescan or its cheap chinese clones, to a nagler or more modern chinese nagler clone. At that point, adding the paracorr eeks that extra bit of perfection out of the field. I am kind of bummed that televue only does type II now, because that sucker is expensive. I can understand eliminating the original smaller lens (t-thread) versions and forcing the universal system and it's available tunable top, and T adapters and spacers, but they should have at least kept the universal type 1 in the lineup.

I have owned the original photo-visual version, and then the second to last version of the visual only paracorr. Of course it was vignetting with the 31 that prompted me to get the visual model. At f5, the 31nagler still did very well, and when I was offered a trade I couldn't refuse at a star party for the visual, I let it go figuring I could still use the original for the 22nagler, which totally blew chunks without a paracorr. At f4, the paracorr was a much bigger necessity than it was at f5.

When I sold my 8"f4, I included the photo-visual as a package, because imaging was the main interest of the buyer.

If I get back into dob's, I hope I am lucky enough to get a paracorr at a good price. I am one of the guys who can see the difference, and would not have traded that visual model had I not had the original photo/visual as a backup. It is a non issue for me now being newt free, but I spent a good portion of a decade as a newt guy.

#19 Keith

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Posted 07 November 2012 - 08:26 AM

So, a 3" eyepiece might make sense in big SCTs which are not yet available, big slow refractors and marginally in 25" Dobs?

Eh... :shrug: I think I'll pass.

Mike


wondering what you mean by big scts that are not yet available. Were you just referring to the diagonals not being available? IIRC ES might have been planning a 3"barrel refractor type diagonal (which makes sense since Scott was ref their APO). Even if that is the only diagonal they offer, and they do not offer 3" visual backs for SCTs, OPTEC already does for their 314 and 316 3" .75 reducers, for folks who want the benefit of those reducers (imaging) without having to shell out the big bucks for the TCFS-3 focuser. 3" slide in optics are already on the market in the imaging scene, so getting a visual back for the SCT is not a problem, should ES intend their diagonal only for refractors.

Either way that EP looks to be 10lbs easily, It is one thing to have to slide a CW to rebalance for a 31 nagler, but this would require adding another weight for sure in some cases.

#20 Keith

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Posted 07 November 2012 - 08:38 AM

Oh, JMI had a 3" focuser too, so getting them on a dob would have multiple options, but coma would be an issue. My experience with ethos and ES100's in f5 and slower is that they are in the "good enough" range like the 31 nagler. Of course Jon has VERY good points about issues like this being an even bigger field where more intense coma would be, and requiring a bigger secondary. Not to mention trying to balance a dob with an EP that heavy.

I think this EP will be a winner with the BIG cassegrain guys, RC's and CDK's and Classical Cass, and of course the aforementioned big SCTs, where a field that large is actually NEEDED. If I had one of these I would have a 4"-3" sleeve made and take the sucker to the 60" on mt wilson or palomar, but it would have to be very good seeing, IIRC they are f16 and that would be over 800x! This is where it would be sweet if ES considered 40 and 50mm range 3" eyepieces with 82 and 68 degrees. Maybe even less critical designs since they would only be used on f7 or slower scopes. More realistically, the local club has a 21.5" Cass in f8 mode (has f16 secondary as well but never used), last I knew it had a 4" WO focuser on it, so all that would be needed was a 4"-3" sleeve to adapt the diagonal (which ES hopefully includes with the EP or has available at least). I know the 31mm nagler and my widescan III look great on that scope, this sucker would probably be pretty awesome at 146x with a TFOV approx .68 degrees w/3.75mm exit pupil. *BLEEP* now we need a 3" UHC filter!

Just speculating of course, as the market is limited, and I think they will probably stop at the 30 and market it as an uberwide for the APOs with big focusers.

#21 Keith

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Posted 07 November 2012 - 08:58 AM

The problem with a 3" eyepiece is then you need a bigger secondary, which means lower contrast and light transmission. Maybe for a large aperture scope it would be ok, but there is going to be that compromise. I believe the CO on an 11" SCT is almost 4" already. Do you really want to make it 5" to get a wider field of view? Maybe on an F5 18" dob it would work well. But then you have to balance what looks like a 5-lb eyepiece!

I don't know, I do not see a lot of interest in this outside of observatories that use larger than 2" eyepieces for their huge telescopes. But it is fun to think about!


I missed this one earlier. The bigger secondary applies to newtonians, not SCTs, the narrower light cone of the SCT could possibly allow this to work well, especially on 14". Since the 1.5(or 1.75 I forget) inch rear opening on an 8" SCT works well with full field 2" eyepieces, I am sure this sucker will work fine on an 11" with its nearly 3" rear baffle. It might require a low profile thread on diagonal vs one sliding into a visual back as I mentioned earlier, but I am not sure to what degree that would be necessary, if at all.

But "redesigning" the optics of a cassegrain for this eyepiece would not be necessary. What Jon was referring to were newtonians, which are typically optimized for the most acceptable illumination at the edge of a 2" field, typically 70% or better for visual, and 100% or more in an astrograph. A visually optimized newtonian would likely show darker edges with this, and that is where a larger secondary would be needed. On an SCT the secondary is no where near the point of focus, on a newt it is much closer and is an important factor in the design.

#22 Sarkikos

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Posted 07 November 2012 - 09:13 AM

Keith,

wondering what you mean by big scts that are not yet available. Were you just referring to the diagonals not being available? IIRC ES might have been planning a 3"barrel refractor type diagonal (which makes sense since Scott was ref their APO). Even if that is the only diagonal they offer, and they do not offer 3" visual backs for SCTs, OPTEC already does for their 314 and 316 3" .75 reducers, for folks who want the benefit of those reducers (imaging) without having to shell out the big bucks for the TCFS-3 focuser. 3" slide in optics are already on the market in the imaging scene, so getting a visual back for the SCT is not a problem, should ES intend their diagonal only for refractors.


SCT's are the only major type of scope that I've never owned, and I don't really plan on owning one ... well, maybe a nice C6 for grab-n-go. :grin: And I'm not into AP at all, so I've not really kept up with what is available in both those areas. But just reading this thread I got the impression that 3"-EP-ready SCTs are not out there now. I suppose that was a false impression?

Either way that EP looks to be 10lbs easily, It is one thing to have to slide a CW to rebalance for a 31 nagler, but this would require adding another weight for sure in some cases.


Yes, the weight could be a deal breaker for many observers. I had a hard enough time balancing my scopes for my 2 lb ES 82 30mm, much less some 10 lb monster.

Overall, I don't see 3" eyepieces having a big market among consumers of astro gear. Barely a notch in a niche.

Mike

#23 Keith

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Posted 07 November 2012 - 10:18 AM

C11/14 and Meades 10/12/14 all have a 3" thread on the rear cell. Hence the peterson eye opener option. On a standard LX200 with microfocuser, there is a step down ring to standard 2" threads that has about 1.5" clear aperture, so widefield 2" eps get light loss at the edges. Taking off that step down ring, and attaching a visual back or focuser directly to the 3" rear cel, opens the aperture to the full 2" and then some. So all it takes is a 3" visual back and diagonal (not common) and theoretically this could work. Since the 11" and the 14" celestron both use the same thread, it is already possible to add a 3" JMI or optec focuser to the scope, so all that would be needed was the diagonal. I would be interested to see a field lens pic of that monster 30, to see how much of the 3" field it is using. Since the light cone is a narrow f10, I have a feeling this could work well on even a c11.

#24 Darren Drake

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Posted 07 November 2012 - 10:39 AM

Keith
I would estimate based on the 31 nagler being what it is that the field lens is about 2.4 inches across but that's just an educated guess. I'm pretty sure its not the full 3 inches.

#25 Keith

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Posted 07 November 2012 - 11:03 AM

a full 3" in 82deg or 68deg would be pretty sweet though, or even 42mm82 and 55mm68, even if they are not full 3" (I think the pentax 60mm XL was 65deg at full 3" thread on)






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