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919 553-3980



919 553-3980



Thank you for visiting Siebert Optics!
Serving Large Observatories and the Amateur Astronomy Community alike.

200 Short Johnson Road
Clayton, NC 
USA  27520


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Eyepieces From .965" / 1.25" / 2.0" / 2.7" / 3.0" / 4.0" / 4.3"


BT70 RA88 / Miyauchi / Kowa eyepieces


Advanced Barlow Lenses including: Modular and 4 element Telecentric magnification multipliers


1.25" and 2" Advanced Binoviewers From $649-$1999


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Large and Small Non Illuminated and Illuminated Cross haired eyepieces.


Large and Small Binocular Cleaning and Alignment services $99 Call or Email for details.


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Camera Adapters - Universal


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Special binoviewer services and products you cant get anywhere else 

ICP's Image Correction Prisms for Newts




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Large refractor modular OTA's


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Observers Hood - light blocking 


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Eyepiece Comparisons

Photos are not intended to convey light transmission or edge brightness since too many other factors are involved including the camera's automatic setting that changes the exposure with every shot.

In short, the below comparisons represent medium price range super plossls costing roughly between $60-$80.  The 26mm superplossl is a Meade series 4000.  These examples are good indications as to how well they will perform both visually and with various types of photography.  The vertical lines superimposed on the right (in black) are to give a basis of comparison to demonstrate either how curved or how straight the lines maintain themselves all the way to field's edge.  Fuji represents the type of camera I used (Fuji 4700 - 4.3mp) a roughly $400 camera.  The 26mm represents the eyepiece size and SP means super plossl and, of course, Siebert is our eyepiece.  Both the 26mm and 32mm superplossl performed astoundingly bad.  The 40mm eyepiece was not necessarily a superplossl, but was a fairly good quality eyepiece.  It was a no name plossl.  But it still did not keep its edge correction when matched against my 45mm, but did have a wider fov.  I have been stating for some time the differences between my eyepieces and some of the other medium priced eyepieces.  This is proof of comparison.  All photographs were taken on an ETX 90RA at a distance of 20'.  You are encouraged to do your own tests if purchasing any of these eyepieces.  Color, sharpness and brightness were not edited.  These factors are exactly as represented.  So the false color you see on the 26mm is actually how the image looked.  Any questions or observations are welcome.  These tests can be performed by anyone having a relatively long focal distance scope with a digital camera and the ability to focus close.  An ETX would be preferable for these tests or other small SCT's.  The type of paper that was used was just graph paper.  


First 6 pictures are standard eyepieces 1.25" Siebert 26mm, 35mm and (45mm no longer in production) Vs their Super plossl  (SP) counterparts. 


Below them start the premium comparisons.

    Now the premium comparisons. Nagler and Panoptics compared to the best Siebert Optics eyepieces.


Notice the Siebert 24mm Ultra shows less field curve* in at F11.5. This serves the 24mm SO well in slower scopes. But the Pan starts to have a better edge as you get under F/6 and stars are a finer pinpoint at the edge. The Siebert 24mm Ultra is a killer eyepiece for binoviewers and also does great in any scope as a single eyepieces if you stay over f/6


Field curve* is roughly the same on these two maybe the Nagler a slight hair better. The Ultra 17mm has better eyerelief at 20mm and took a better picture then the Nagler 16mm type 4 although the Nagler had a 82 deg FOV and the 17mm Ultra had only a 70 deg FOV. I feel some will think it is a good trade.


Do not compare the focus, brightness and edge vignette below since the camera had more to do with the results then the eyepieces. 

The Pictures above give a good comparison of the design difference of 3 great eyepieces. The Observatory Series is a blend of the other two. The intent behind the design of the 34mm and 36mm were to balance Pin-cushioning with Field flatness so that the result would be far less Pin-cushioning then the Pan 35mm bringing it close to the Pentax 40mm you see in the picture above without compromising Field Flatness which is certainly a strength of the Pan 35mm. By balancing the strengths the result is that most people will find the Observatory Series compliments their scopes without too much Pin Cushioning  or a lack of field flatness. The #1 and #2 complaint I hear about low power high end eyepieces is their tendency to curve the stars around the field rather then move in a strait line ("This can be very distracting when sweeping the sky") or ("The whole field won't come to focus at the same time and if I focus the center the outer 20% of the edge is not in focus and vice versa.") .As quoted by 2 different customers. 

Do not compare the focus, brightness and vignette above since the camera had more to do with the results then the eyepieces.

Do not be concerned about the brightness of the photos since it is more a product of the camera position and shutter speed then the result of the eyepieces ability to transmit light. More soon.......





Coming soon 11mm Siebert Ultra compared to the Radiant 12mm. 


This is the new line of 1.25" and 2" Ultra Plus eyepieces.  The grid paper photographs below with superimposed black lines show graphically (no pun intended) the extremely optical quality of these eyepieces particularly with regard to edge sharpness.  Most of these photographs are not necessarily good quality otherwise and are not a good judge of the brightness and contrast as well as overall sharpness.  Some photographs have been resized and brightened and darkened to make them fit on the web page and to show up the vertical lines better.  Some photos may not be sharp to due to the camera's focus. (I am certainly not an expert astrophotographer.  These are the only enhancements made to these pictures).  But they do a very good job of showing field flatness and edge correction in relation to vertical lines.  As regards to edge correction almost all of this series regardless of the mm size maintains virtually vertical correctness.  This includes the 2" series with its extremely large set of optics.  Edge correction remains amazingly good.  Soon all my 1.25" and 2" eyepieces will be photographed here in the Ultra Plus series.              




                                            22.5mm Ultra Plus 1.25"                                                                 32mm Ultra Plus 1.25"                         

                          These eyepieces have less than 1% edge degradation Sorry about the shutter speed on the 32mm.

 It came out a little dark 1% over correction of particular benefit to people with scopes between f/4 and f/5.


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