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Explore Scientific 3" 30mm Prototype

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#51 gatorengineer

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Posted 27 December 2012 - 11:36 AM

Well, I just pre-ordered mine. With the reason being, is that with the 25 F5, I will now have 105x at 1 degree with a 6mm exit pupil.

A E21 in a 25 F3.3 gets you .86 with a 5.5mm exit pupil, an E21 in an F3.7 gets you .77, at a 5mm exit both requiring paracorrs

So now I can get wider field of view then the fast scopes, still have the ladder, but am about 15k less invested....

Next step will be the 3" feathertouch.

In this regard, as there is not a standard for 3" eyepices, would it be possible for Astronomics (who I ordered through), to ask what the exact interpretation of 3" is and what the taper is... Thanks.

BTW I dont expec the eyepiece until 14, but hey its on order....

#52 Starman1

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Posted 27 December 2012 - 02:18 PM

Well, I just pre-ordered mine. With the reason being, is that with the 25 F5, I will now have 105x at 1 degree with a 6mm exit pupil.

A E21 in a 25 F3.3 gets you .86 with a 5.5mm exit pupil, an E21 in an F3.7 gets you .77, at a 5mm exit both requiring paracorrs

So now I can get wider field of view then the fast scopes, still have the ladder, but am about 15k less invested....

Next step will be the 3" feathertouch.

In this regard, as there is not a standard for 3" eyepices, would it be possible for Astronomics (who I ordered through), to ask what the exact interpretation of 3" is and what the taper is... Thanks.

BTW I dont expec the eyepiece until 14, but hey its on order....

Just a note about Coma and Paracorr:

It is not the exit pupil or true field that determines whether coma is visible in a field of view, it is the apparent field of the eyepiece.

I'll explain.

Take two eyepieces of 25mm--one of 50 degree field and 1 of 100 degree field. Since the field of the 100 degree eyepiece is twice as wide, coma at the edge (a linear feature) is twice as wide a star image in the 100 degree field as it is in the 50 degree field.

Now, use a 12.5mm 100 degree eyepiece. The field is 1/2 as wide, so the comatic star image at the edge is 1/2 as wide--the same width as the comatic star at the edge of the 50 degree field in the 25mm eyepiece.

BUT, the magnification is now twice as great. That increase in magnification makes the apparent size of the comatic star image at the edge exactly the same as it appeared in the 25mm 100 degree eyepiece.

And so it is with all magnifications--the apparent size of the comatic star image will be the same at all magnifications in 100 degree eyepieces.

So what eyepiece seems to present a comatic star image at the edge of the field is determined by the apparent field. Don't like coma? Stick to scopes longer than f/5 or apparent field eyepieces of 50 degrees or less.

Or, use a scope not known to have visible coma: refractor, Maksutov, etc. The SCT does have coma unless it is corrected (such as the Meade ACF or the Celestron Edge, both of which are corrected to eliminate coma). The standard f/6.3 reducer does a pretty good job of that in a standard SCT (it is a reducer/corrector).

#53 faackanders2

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Posted 27 December 2012 - 06:05 PM

Well, I just pre-ordered mine. With the reason being, is that with the 25 F5, I will now have 105x at 1 degree with a 6mm exit pupil.

A E21 in a 25 F3.3 gets you .86 with a 5.5mm exit pupil, an E21 in an F3.7 gets you .77, at a 5mm exit both requiring paracorrs

So now I can get wider field of view then the fast scopes, still have the ladder, but am about 15k less invested....

Next step will be the 3" feathertouch.

In this regard, as there is not a standard for 3" eyepices, would it be possible for Astronomics (who I ordered through), to ask what the exact interpretation of 3" is and what the taper is... Thanks.

BTW I dont expec the eyepiece until 14, but hey its on order....


I can just see it now; 3" focuser soon to become the new standard for large dobsonians. Many may feel it is time to upgrade their scope or buy a new one.

#54 Astrojensen

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Posted 27 December 2012 - 06:15 PM

And why not? Rafael Benner has a 4" focuser on his 30". It has 5" of travel, allowing to change from a single eyepiece to a binoviewer without fumbling with extension tubes or use barlows. On a 30" this is of course similar to a 2" with 2.5" travel on a 15"... Nothing ordinary. A 4" focuser doesn't look all that big on a 30". In Rafael's case, there's no need to worry about balance issues, when using a 30mm/100° eyepiece. It takes some real muscle power to track that huge dob.


Clear skies!
Thomas, Denmark

#55 gatorengineer

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Posted 27 December 2012 - 07:24 PM

Well long focus big dobs are a dying breed, Until they come up with a Paracorr X in 3", I dont expect to see many of these in todays generation F5 big dob..... For me its a worthwhile investment. I love my 9 120.... The next problem is the near $700 focuser from feathertouch. The other thing not to be discounted for me, is going from this thing to a small Nagler will be a heck of a balance change.... But fun...

#56 Astrojensen

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Posted 28 December 2012 - 04:51 AM

Until they come up with a Paracorr X in 3",


But these already exist! Well, sort of...:

http://www.astroopti...h/NewtWynne.htm

Not really plug 'n play, but it exists!


Clear skies!
Thomas, Denmark

#57 faackanders2

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Posted 28 December 2012 - 09:52 PM

Until they come up with a Paracorr X in 3",


But these already exist! Well, sort of...:

http://www.astroopti...h/NewtWynne.htm

Not really plug 'n play, but it exists!


Clear skies!
Thomas, Denmark


This is for a 4" coma corrector. It would be even a bigger leap from 2" to 4", but the cost would likely be out of reach for many; so 3" (or 2") may be the limit for most.

P.S. Moderator, Could this be moved to the eyepiece forum so it is easier to find?

#58 Astrojensen

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Posted 29 December 2012 - 02:52 AM

This is for a 4" coma corrector.



Oops! :) Well, it will fully illuminate a 3" eyepiece, that's for sure.

Let's try again:

http://www.astrosyst...3Zoll_Wynne.pdf


Clear skies!
Thomas, Denmark

#59 gatorengineer

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Posted 30 December 2012 - 05:30 PM

Well the issue with the Wynn is that it may not work visually. I dont know that it will or wont, but I was interested in buying one a few years back before the Paracorr 2 for an F3.5 scope. I called the US distributor and frankly he laughed at me on the phone.... Needless to say this vendor will never get a dime from me, it would be interesting to know if the wynns work visually. There are a bunch of F3ish dobs out there that arent fully illuminated with a 2" P2....

#60 Astrojensen

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Posted 30 December 2012 - 06:39 PM

Why shouldn't it work visually??? The 3" Wynne corrector from Philipp Keller has ~55mm working distance and the 4" around 60mm. I would email Keller directly and ask. I am pretty sure he could also design something with greater working distance, if the edge correction tolerances are relaxed a bit, as would be perfectly possible in visual observing.


Clear skies!
Thomas, Denmark

#61 AlienRatDog

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Posted 30 December 2012 - 07:32 PM

I am interested in a 40mm eyepiece...would be nice to make an adapter for larger SCT visual backs (I have a 12" SCT, I believe the back is like 3" or something like that)...so special 3" diagonals with large SCT adapter (11,14" celestron scts and >10"Meade SCTs)...I would be all over that!

#62 rboe

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Posted 30 December 2012 - 10:04 PM

This should help....

Attached Files



#63 herrointment

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Posted 31 December 2012 - 12:38 AM

Ron, I looked at your photo and swore I heard wheels turning.

#64 faackanders2

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Posted 13 January 2013 - 07:21 PM

Will ES be bringing this to NEAF or any of the shows?

#65 frebie

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Posted 14 January 2013 - 10:50 AM

I would certainly assume so, but you'd need to check directly with them to be sure.

#66 GeneT

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Posted 02 February 2013 - 10:59 PM

For some, OK--for me, no thanks.

#67 Bart

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Posted 05 February 2013 - 10:44 AM

I think the point of ridiculous has been reached!

#68 DaveJ

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Posted 05 February 2013 - 10:50 AM

I think the point of ridicules had been reached?


If you mean "ridiculous" I completely agree with you!

#69 Bart

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Posted 05 February 2013 - 05:52 PM

Yes, and I see I made two other mistakes as well. :tonofbricks:

#70 Clif

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Posted 07 February 2013 - 03:16 PM

I figured out by scaling the photograph (taking perspective into account) that the OD of the widest part of the eyepiece is 4.22 inches. Unless you have REALLY widely separated eyes, don't even think of buying two for a binocular.

#71 faackanders2

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Posted 10 February 2013 - 10:37 PM

I figured out by scaling the photograph (taking perspective into account) that the OD of the widest part of the eyepiece is 4.22 inches. Unless you have REALLY widely separated eyes, don't even think of buying two for a binocular.


Most 2" eyepieces can not be used for binoviewing either.

#72 aa6ww

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Posted 12 March 2013 - 07:52 PM

I think its awesome. Once all the bugs are worked out with adapting it to scopes, I'll get me a set. Good thing I paid off my house last year!!
I have a TOA with a 2.7" focuser, and an APM with with a 2.5" focuser, so at least that ones easy to upgrade, Better still, it should be awesome in my C11 and C14!!!
Bring um on with the big diagonal also!! a 40mm 100deg eyepiece would never stay on the shelfs, even with a $2k pricetag!!

...Ralph

#73 pbsastro

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Posted 17 March 2013 - 06:10 AM

Ralph, a 40-100 will not work in a C11 or C14, as they are limited to a 53-55mm illuminated field. The 30-100 has a 52mm field. A 40-100 will have a 70mm field. Even refractors with 1200+ focal length will start to show field curvature and other aberrations at the edge. You will have to go with 1600+ focal length.
If you want 40mm for the C14/C11, with the same 52mm field, that would be 40-75, but close to that we already have the XW40 and Pan41 with field of 46mm.
That said, the 30-100 will be awesome in the C14HD or C11HD.

#74 gatorengineer

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Posted 26 March 2013 - 05:13 PM

I bino view Ethos 17's.... with a Siebert 2" binoviewer. The explore 9 120 is too big, as is a terminagler.

#75 larry7

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Posted 25 June 2013 - 06:23 AM

Scott, I am very interested in a 40mm 100 degree plus a 3 inch diagonal for a 2 inch focuser!!!!!! Larry






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