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919 553-3980



919 553-3980



Thank you for visiting Siebert Optics!

200 Short Johnson Road
Clayton, NC 
USA  27520


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About Siebert Optics

Contact Information







Telescopes for sale



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


 Binoviewer OCA's and Accessories


Binoviewer Alignment and Supercharge Services


Adapters - Meade Scopes and ETX


Binoculars - Quality Modified


Large and Small Non Illuminated and Illuminated Cross haired eyepieces.


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


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




Observers Hood - light blocking 


Planetary Fleece Blanket 


PST Accessories


Telecentric Barlow Lenses


Zero Magnification Adapter





Ladies Corner

Saturn Earrings  

Astronomy Themed  Fleece Blanket 

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









Converters & Extension Tubes


Self Centering eyepiece holder refits.

Fits most $200 binoviewer clones.

 Self Centering eyepiece holders Pair-$49. (BOsc)

Do you want to use your Burgess/Orion/ or similar Binoviewer and have  a fully Self Centering Diopter arrangement  Get rid of your white Nylon screws  and merging problems.  Spring loaded Self Centering mechanism always give perfect centering. Effortless installation. If you have questions call or email. More info under picture.


The binoviewers that can use these are the ones that have the nylon screws and relatively thin eyepiece holder walls that they thread through that makes unscrewing them a hazard since it does not take many turns to have them fall out. On the unit above the eyepiece holder on the left is different then the one on the right. The left is too thick to use these refits. It was a later model eyepiece holder that had thicker walls for the screws to thread through. The right side had the thinner walls and the adaptors can fit over the holder for a proper attachment. So if your binoviewer eyepiece holder looks like the one below you are set.

Converters and ID enhancement for refractors and SCT's Diagonals

 Refractor nose replacement. This sells for $30. (WOrefdiagnose)

SCT visual connector replacement. This sells for $30. (WOsctdiagnose)

Or both for $50

Do you want to use your WO, AT, Denk, Orion, or other similar Diagonal with your refractor but can't because it is made for an Celestron SCT visual back. How about the other way around. You might have to purchase a whole second Diagonal to be covered. Here is the  solution in the picture below.


These are also better in one very important way. They have a larger CA inside the front tube then the OEM part does. 41mm is the max size in these diagonals. The Siebert Optics replacements are 45mm Dia. CNC machined and nicely baffled inside. These replacement nose attachments are what is needed . 


52mm to 49mm filter converter

52mm to 48mm filter converter

49mm to 48mm filter converter

And any combo of these sizes you can think of.

Just specify the type ends

Ex: 52mm male / 48mm Female.

Ex: 48mm male / 52mm Female.

Ex: 49mm male / 48mm Female.

Ex: 52mm female / 48mm Female.

This sells for $39 each or 2 for $60 (CON5248)


These are for Camera and telescope filter exchanges.


Pictures Soon.



2" or 1.25" Adapter rings both male and female

This sells for $10 each or 2 for $15 (CON91R)

All rings are standard eyepiece and filter compatible.

Adapter shown: 2" standard Female inside treads. .

2" Male outside also available

.2" to 1.25" Super low profile and self centering. 

This sells for $30. (CON91SD)

These are also ideal in the 2" Black Knight Binoviewer.

Adapters are shown here in a 2" binoviewer.

1.25" to  2"  Converter

This sells for $65. (CON91st)


.965" to 1.25" Straight Converter

This sells for $30. (CON91STR)


Extension Tubes:


1.25" Extension Tube 

providing 1.5" of extra travel.

$20 (125EXT)




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!.

available in any dollar amount you wish to purchase.

I accept PayPal, the #1 payment service in online auctions!

We accept Visa, Mastercard,


  American Express. U.S. Money Orders, and Personal Checks (held 10 working days for clearing)Online payments may be made securely through



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