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


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


BT70 RA88 / Miyauchi / Kowa eyepieces


Binoviewer Alignment and Supercharge Services


(Specialized Binoviewer services you can't get anywhere else)


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


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


 Binoviewer OCA's and Accessories


Adapters - Meade Scopes and ETX


Binoculars - Quality Modified


Large and Small Non Illuminated and Illuminated Cross haired eyepieces.






Camera Focus Adaptors


Camera Adapters - Universal


H-Alpha Focus Accessories



Special binoviewer services and products you cant get anywhere else 

ICP's Image Correction Prisms for Newts




Extension Tubes


Large refractor modular OTA's


Eyepiece Comparisons


Focal Length Reducers




Planetary Fleece Blanket 


PST Accessories


Telecentric Barlow Lenses


Zero Magnification Adapter





Ladies Corner

Saturn Earrings  

Astronomy themed totes/purses


Free Domain Pictures

Astronomy Accessory Links of 

       products not offered 

       by Siebert Optics


Useful Astronomy Links


International Dealers


Astro photos


Non-Astronomy Items









 2" up to 4.3" Observatory Series

Here are some reviews that have been done on the Siebert Optics eyepieces showing their advanced optical design   Click here, and  here   



See our UT Monocentrics and Planesphere eyepiece line. Click here


Observatory 2" eyepieces. Click here.



Elite 2.5"/2.7"/3"/4"/4.3"eyepieces. Click here and here.



Diagonals: 2.5"/2.7"/3"/4"/4.3" and Hybrids. Click here



Telecentric Barlows: 2.5"/2.7"/ 3" 1.5x - 2.5x Click Here



2" 36mm Eyepiece

This eyepiece is only sold as a binoviewer pair with the purchase of a Elite series binoviewer and is not sold individually.

  2" has a 65 deg. FOV and 20mm's eye relief.

 Compact in size and only 9 oz.

No "Blacking out" or "Pin Cushioning" 

  2" is $269 (Ob236mm) Brass add $70*




35mm Pan vs. Siebert Observatory 36mm. Both are sharp to the edge in fast scopes but the OB wins on pin cushioning and it also has eye relief that people with eye glasses will appreciate. >>>>>>>>>>>>>>>>

All Observatory. eyepieces are under 9 oz.

Were did the Observatory Series eyepieces come from. Click here

Large optics reduce apparent vignetting.


Click on picture to enlarge. Here is the eyepiece comparisons page. 

Observatory eyepieces are known for their excellent edge correction. The 34mm and 36mm are sharp to the edge at f5 and very good at f4.5 without a Paracorr.


2" 34mm Eyepiece 

This eyepiece is out of production. 

2" has a 65 deg. fov and 20mm's eye relief.

 Compact in size and only 9 oz.

No "Blacking out" or "Pin Cushioning" 

    2" is $269 (Ob234mm)Brass add $70*


All Observatory. eyepieces are under 9 oz.

Large optics reduce apparent vignetting.


Click on picture to enlarge. Here is the eyepiece comparisons page.

Observatory eyepieces are known for their excellent edge correction. The 34mm and 36mm are sharp to the edge at f5 and very good at f4.5 without a Paracorr.


 Observatory Elite

This line has many professional and  amateur applications

See complete list below.

Click on pictures below.


 4"  40mm - 100mm

 4.3"  40mm - 100mm


2.5" 40-70mm $899 (Brass) add $199* .

For Istar and like F10-F15 .

All have 25mm E.R.

The 2.5" 40mm 75 deg FOV

The 2.5" 42mm 75 deg FOV

The 2.5" 50mm 70 deg FOV

The 2.5" 55mm 63 deg FOV

The 2.5" 60mm 57 deg FOV

The 2.5" 65mm 53 deg FOV

The 2.5" 70mm 50 deg FOV

2.5 lb



2.7" 40 -70mm $899 (Brass) add $299* .

All have 25mm E.R.

The 2.7" 40mm 75 deg FOV

The 2.7" 42mm 75 deg FOV

The 2.7" 50mm 70 deg FOV

The 2.7" 55mm 65 deg FOV

The 2.7" 60mm 63 deg FOV

The 2.7" 65mm 58 deg FOV

The 2.7" 70mm 54 deg FOV



3" 40 -70mm $999  (Brass) add $299*

All have 25mm E.R.

The 3" 40mm 75 deg FOV

The 3" 42mm 75 deg FOV

The 3" 50mm 70 deg FOV

The 3" 55mm 70 deg FOV

The 3" 60mm 65 deg FOV

The 3" 65mm 63 deg FOV

The 3" 70mm 58 deg FOV

The 3" 75mm 55 deg FOV

The 3" 80mm 50 deg FOV

 4.0 pounds


4" 40-100mm  $1499  (Brass) add $499* 

4.3" 40-100mm  $1499  (Brass) add $499*

All have 25mm E.R.

If your scope has to carefully manage focus in-travel please give me details on the limitations of your scopes focus.  

All have a No F.S.

    40mm AFOV 75deg

    42mm AFOV 75deg

 50mm AFOV 70deg

55mm AFOV 70deg

60mm AFOV 70deg

65mm AFOV 65deg

70mm AFOV 65deg

75mm AFOV 60deg

80mm AFOV 60deg

85mm AFOV 57deg

90mm AFOV 55deg

95mm AFOV 52deg

100mm AFOV 50deg



Observatory Elite 50mm - 110mm sizes 2.5" - 4.3" eyepieces are 6 element. They are fully anodized Grey.

For large diagonals click here.

 This 80mm 4" eyepiece was sent to the Mount Wilson observatory in 2007 for use in their 60" Cas   See it in use in link below.   E.P. info here.

All pictures used are with the permission of owner.  http://www.icstars.com/HTML/Events/MtWilson60/index.html Click pictures below.


How about this 70mm 4.3" 70 deg eyepiece that was sent to the Carnegie Institution of Washington in 2010 for their 6.5 meter or ( 234") Magellan. Link to Observatory below. The Siebert 70mm is in the side of the scope next to Patrick.


Picture of the Carnegie Institute's Magellan in Chile With Siebertoptics 70mm 4.3"

https://www.youtube.com/watch?v=i9dNDGOmmgI  Changing the mirror.





This scope below belonging to the MDM Observatory are now using my 80mm Elite 4.3".and a 4.3" diagonal.

Pat Seitzer who is pictured above viewing through the Magellan purchased the 80mm and 4.3" diagonal in behave of the University of Michigan. The school is a part owner of the scope 2.4-m Hiltner pictured below. Here are a few of his comments.

Looking to obtain an eyepiece and star diagonal for the 2.4-m Hiltner telescope at MDM Observatory on Kitt Peak.  This is a f/7.5 Ritchey-Chretien scope without a field corrector. Thanks, Pat

I have looked through your eyepiece on the 6.5-m Magellan telescope in Chile - amazing view.  They recommended me to you.

Hi Harry
The 80-mm eyepiece is a smashing success on the 2.4-m Hiltner telescope at MDM Observatory.   Fantastic views. Photo of it and star diagonal on tailpiece attached. Great job.
Thanks, Pat

The apparent FOV is perfect for M51 - both components fully visible. Really dynamite viewing. ---Pat


                                                     2.4 meter Hiltner below.                               



How about this 110mm 4.3" 55 deg 10 lb eyepiece that was sent to the University of California for the Lick Observatory in 2013 for their 36" 3 story Historic Refractor.

Above is Dr. Elinor Gates Manually pushing the Giant Lick refractor. Comments from the Dr. Gates below..

"Here is a photo of the eyepiece as mounted on the 36 inch refractor. At some point I hope to get a better photo, but I think you'll agree the brass eyepiece looks very nice in the historic brass mount we have. We haven't had much opportunity to use the eyepiece yet as our summer programs have just started for the season, but I'm pretty pleased with it so far (though one of our volunteers thinks the eye relief is less than 25 mm, but I haven't measured it, so don't know if he is complaining about nothing or not)".


Link to Observatory below.




   2.7" and 3"eyepieces. 4" and larger below.

These 2.7" and 3"eyepieces are for Large and Backyard Observatory Telescopes alike.  Camera adaptor now Optional.


4 " and + size Eyepieces


The above 80mm is used at the Mount Wilson Observatory in California.  Here  the 80mm Elite is compared to a 40mm Pentax XL.  And below shows the optional mounted on camera adaptor.

The above 70mm 4.3" eyepiece is used in the 24 Foot Dia Magellan in Chile.. picture above. 

This 90mm Elite was sent to Herold Observatory, Onalaska School District, WA as part of an Astro-Physics 4.3" focuser upgrade for their 24" Cassegrain.

Here is the 4.3" Focuser on their site.  Click Here.


28", f/9 Cassegrain Telescope


These 4" 55mm and 70mm Elites below were sent to Seoul Korea for the Research Institute of Space & Astronomy.. Scopes to be used are a 600mm and 1000mm RC..


  The Elite series eyepieces on your scopes.

4.3" / 4 "/ 3" /2.7" and 2.5" Eyepieces Some of these eyepieces can even be used in long F.L. backyard Observatory scopes. The eyepieces below will give you at least twice the amount of sky possible for your largest field stop 2" eyepieces.

10" - 60" and much larger Cassegrain scopes.

5" and larger long F.L. Refractors.

EX: 6" f15 Refractor F.L. 2268mm

------------Here is the Elite difference.-----------------------

(55mm 2" TV Plossl) and it's 50deg AFOV has a 1.10deg True FOV.  

(65mm 3" Elite) and it's 65deg AFOV has a 1.67deg True FOV.

Now that sounds like only about 51% gain in true FOV but the amount of sky you are now covering more than 2.3x greater in terms or Square area. This will hold true for any scope you use it in. More facts below.

-----Will you have problems with your Exit Pupil. Look Below.-------

Exit Pupil with 3" 65mm at F15 is      = 4.3mm --Great

Exit Pupil with 3" 65mm at F12.5 is   = 5.2mm --Great

Exit Pupil with 3" 65mm at F10 is      = 6.5mm --Not Bad

Click on eyepiece pictures below to enlarge.

What scopes can use the 50mm-110mm?  Many CCD chips will benefit from the 40mm-50mm eye lens and huge optics of these eyepieces. In fact it may be the lowest possible power photo you could take through your scope with eyepiece projection imaging. 



 2.5" 2.7" 3" 3.7" 4" 4.3" Diagonals

Diagonal  2.5" -  3.0" optical path 6"

All diagonal come with a stepdown to use 2" eyepieces

2.5" Diagonals  

2.7" Diagonals   

3" Diagonals

4.0" Diagonals 

3.7" Diagonals 

4.3" Diagonals 

Other attachment modes possible just email.

All Anodized. 2.5" up to 2.7" - Price: 14th~ $1199 /20th~ $1299  /30th~ $1399 Brass fixtures add $499 

All Anodized. 3" size - Price: 14th~ $1399 /20th~ $1499  /30th~ $1599 Brass fixtures add $799 

All Anodized. sizes up 3.7" up to 4.3" 14th~ $1999 /20th~ $2199 / 30th~ $2399 Brass fixtures add $1199

Any Adaptor you wish for the above diagonals.

2.7 to 2"  $79 each

3" to 2"  $79 each

3.7" to 2"  $99 each

4.0" to 2"  $99 each

4.3" to 2"  $99 each

 Telecentric Barlows

Specify size and magnification.

Barlow 2.5" $299

Barlow 2.7" $399

Barlow 3"    $499

Barlow 4"+   $699







  4.3" on top 3" and smaller below. Diagonal are 14th to 30th ~ and  97%-99% reflective. Precision Annealed Pyrex.


 All T- 6 and Black Delrin construction, Fully baffled.

30 day return policy. "No restock fees"







Pictures soon













Pictures soon






See Products list for complete list of prices and configurations.


All listed products come with a 30-day money-back guarantee* unless otherwise stated.

Specialty order items are not refundable (items made specifically for you).

We welcome
International orders!.

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