The Baader Astro T-2 System™

t2-system-grafik Baader Astro T-2 System™ Component Chart

For over 30 years we have focused on the Astro T-2 thread system (M 42 x 0.75 mm); virtually every telescope manufacturer must offer this thread far ahead of the focal point of his instrument, such a universal T-ring (for DSLR cameras) can be connected.

The only exceptions are (still) Russian equipment, there the thread diameter is the same, but the pitch is still 1mm per revolution - rather than 0.75mm! Therefore, we offer among other things a "Russians adapter". At only 7mm additional optical length it can allow so many Russian lenses or telescopes to be compatible with an international Astro T-2 (M 42 x 0.75mm) connector!

For the sake of better recognition mostly are marked. See marking small 'a' or small 'i' in the respective indication! "a"; identifies an external thread (male); or, if Ø sign which a diameter, "i"; - a female is always (female) or - Ø character - an inner diameter.

 

The Optical Length

t2-system-produkte A small selection from the variety of products from the Baader Astro T-2 System

The optical length describes the extension of the optical path caused by an adapter or accessory when inserted into the beam path of the telescope. The values listed in the system table rounded to 1/2 mm. For pure threaded adapters or tubes such as the T-2 ring (#25), the optical length arises directly from its geometric shape. Because the optical design lengths apply to the assembled, external threads are not included in the bill. This explains the extremely short optical length external thread adapters compared to female threaded adaptors.

Parts that contain optical elements (such as Zenit prisms and binocular) the optical length can vary strongly from the geometrical form of the housing. Hence the values for the optical length by such accessories was determined directly on the telescope. When used with the unique Alan Gee tele-compressor the optical length depends in addition to the distance from the primary focus.

In general: If you add an accessory an item from the Astro T-2 System ™ into the beam path of the telescope, the extension length of the focuser to the value of the specified optical length must be shortened so that the eyepiece tubes moves closer to the lens. For negative values, the focuser must be extended because the distance between the focal plane of the lens increases.

The Baader Astro T-2 System™ Overview

T-2
Component #
LABEL (i)=internal THREAD, (a)=external THREAD Opt. length (mm) Connection: objective connection: eyepiece auxiliary thread or diameter
# 1A Maxbright Mirror Diagonal T-2, incl. Adapter #3 43 T-2(i) T-2(a) M34(i) out #3
# 1B
T-2 Stardiagonal Prism 90°, 36mm (Zeiss Prism), with male/female T-2 thread, incl. Adapter #3
38.5 T-2(i) T-2(a) M34(i) out #3
# 1C
Prism Diagonal T-2 / 90°, 32mm (suitable for Maxbright Bino), incl. Adapter #3
35 T-2(i) T-2(a) M34(i) out #3
# 2
T-2 / 90° Baader Roof-Prism (Astro-Quality-Grade), with male/female T-2 thread, incl. Adapter #3
47.5 T-2(i) T-2(a) M34(i) out #3
# 3
Adapter 36,4a / T-2a (direct T-2 photo-thread for Vixen, NexStar4, Meade a.o. focusers)
0.5 M36.4 x 1(a) T-2(a) M34(i)
# 4A Glasspath Corrector 1.25 (incl. Teflon-centering) ≤ -30 ----- M34(a)/T-2 clamp Ø 38mm -----
# 4B Glasspath Corrector 1.70 (incl. Teflon-centering) -65 ----- M34(a)/T-2 clamp Ø 38mm -----
# 4c Glasspath Corrector 2.60 (incl. Teflon-centering) -120 ----- M34(a)/T-2 Kclamp Ø 38mm -----
# 5 1¼" Extension Tube / 1¼" Glasspath Corrector 18.5 M28(i) M28(a) Ø 26mm(i)
# 6
T-2 Quick Changer (combines Zeiss Micro bajonett with T-2 female thread) Standard Version
11 T-2(i) Ring-clamp -----
# 6A Baader TQC Heavy Duty T-2 QuickChanger 11 T-2(i) Ring-clamp -----
# 7 Baader TCR Hardened Steel T-2 ChangeRing 4 Ring-clamp T-2(a) Ø 38mm
# 6+7 T-2 Changer System (Combination of #6 & #7) 15 T-2(i) T-2(a) Ring-clamp
# 6A+7 TQC/TCR Heavy Duty Changer System (Combination of #6 & #7) 15 T-2(i) T-2(a) Ring-clamp
# 8
Click-Lock Eyepiece Clamp 1¼" (with built in diopter-adjustment)
32-38 T-2(i) Ø 1¼"(i) T-2(a)
# 8A
Focusing Eyepiece Holder 1¼"/T-2 with 3 clamping screws
Fine focussing (5mm focus travel)
Rotation Locking Screw
29-34 T-2(i) Ø 1¼"(i) -----
# 9
Adapter M44 (i) / T-2 (i) (combo of Zeiss M44 female and T-2 female thread)
14 T-2(i) M44 x 1(i) Ø 40mm
# 10 Reducer 1¼" / 24.5mm – for 24.5mm eyepieces 6.5 Ø 1¼"(a) Ø 24,5mm(i) M28,5(i)
# 11 Eyepiece Holder 1¼"/36.4 (a) fits 1¼" oculars onto Vixen thread M36.4 27 M36.4 x 1(a) Ø 1¼"(i) -----
# 12 T-2 / M43 x 0.75 Takahashi-Adapter 0,8 (!) M43(a) T-2(a) M34(i) for #4a,b,c
# 13 External Thread M44(a) / T-2(a) – for Zeiss 5 M44 x 1(i) T-2(a) Ø 38mm
# 14 Nose piece 1¼"(a) / T-2(a) – with safety groove 0,5 Ø 1¼"(a) T-2(a) M34(i) / M28,5(i)
# 15 Reducer 2" / 1¼" – with clamping ring, T-2 thread and M48 filter thread 9 Ø 2"(a) Ø 1¼"(i) M48(i) / T-2(a/i) / M34(i)
# 15A Pushfix 2" / 1¼" reducer for Newton focuser 1 Ø 2"(a) Ø 1¼"(i) M48(i) / T-2(i)
# 15B Baader 2" to 1¼" ClickLock reducer 9,5 Ø 2"(a) Ø 1¼"(i) M48(i) / T-2(i)
# 16 Nosepiece connection 2"(a) / T-2(a) and with safety groove. M48 filter thread 2 Ø 2"(a) T-2(a) M48(i/a) / T-2(i)
# 17 2" SC Deluxe eyepiece 53 UNC 2"(i) Ø 2"(i) /  S65 M58(i)
# 17A+B 2" SC Deluxe eyepiece with 2" filter holder (for SC & HD) 53 UNC 2"(i) Ø 2"(i) /  S65 2" Filter Thread / M58
# 18 3.3" Celestron Nut for C11/C14 (ring clamp #17) 0 UNC 3.3"(i) ----- -----
# 19 2" Barrel, chrome, with Teflon spacer rings 0 Ø 2"(a) UNC 2"(a) M48(i)
# 20 Alan Gee Telecompressor II ≈≤ 50 T-2 clamp T-2 clamp -----
# 21 Baader T-Adapter (BTA) for all SC and MAK telescopes 16 UNC 2"(i) T-2(a) T-2(i)
# 21 B SC Ultrashort T-Adapter with a 7mm optical length, T-2 (a) / 2"(i) 7 UNC 2"(i) T-2(a) T-2(i)
# 22 Thread adapter M43(a) / T-2(a) – Vixen-Adapter 2,5 M43 x 1(a) T-2(a) Ø 38mm
# 23 Thread adaptor M42x1(i) / T-2(a) – "Russian"-Adapter 7 M42 x 1(i) T-2(a) Ø 38mm
# 24 T-2 Sliding / Locking Focuser 1¼"(i) and T-2(i) – Hub 11mm 27.5+11,0 T-2(i) T-2(a) Ø 1¼"(i)
# 25A T-2 intermediate ring 15mm T-2(i) / T-2(a) 15 T-2(i) T-2(a) Ø 38mm
# 25B T-2 intermediate ring 40mm T-2(i) / T-2(a) 40 T-2(i) T-2(a) Ø 38mm
# 25C T-2 intermediate ring 7.5mm T-2(i) / T-2(a) 7.5 T-2(i) T-2(a) Ø 38mm
# 25V Baader VariLock 46 extension Tube 29-46mm with spanner tool min. 29 / max. 46 T-2(i) T-2(a) T-Adapter
# 25Y Baader VariLock 29 extension tube 20-29mm with spanner tool min. 20/ max. 29 T-2(i) T-2(a) T-Adapter
# 26 T-2/T-2 Inverter ring – changes T-2(i) in T-2(a) 0 T-2(a) T-2(a) Ø 38mm
# 27 Thread adaptor 2"(a) / T-2(a) – with M48 thread for 2" Filter 0.5 UNC 2"(a) T-2(a) M48(i)
# 28 Expanding ring T-2(i) / 2"(a) 1 T-2(i) Ø 2"(a) -----
# 29 Threaded ring M48(a) / T-2(i) 2.5 T-2(i) M48(a) -----
# 30 CCD Collar1¼" (Focus stop ring for CCD cameras, etc.) ≤ 10 Ø 1¼"(i) Ø 1¼"(i) -----
# 31 T-2 eyepiece filter holder 0 T-2(a) T-2(a) M28.5(i)
# 32 Eyepiece Ultrashort 2" (on both sides) for Zeiss (M68) 17 M68 x 1 Ø 2"(i) M68 x 1
# 33 Variable extension (12-16mm) incl. lock ring (= #26+34+35) 12 (10) T-2(a/i) T-2(a/i) -----
# 34 T-2 conversion ring (converts T-2(a) external thread in T-2 (i) internal thread) 10 T-2(i) T-2(i) -----
# 35 T-2 locking ring 2 T-2(i) T-2(i) -----

2 thoughts on “The Baader Astro T-2 System™”

  • Brent Harrold

    Hello,

    Can you please tell me what component I would need between a standard t-ring for a Nikon and my Baader 31mm Asph.

    Thank you,

    Brent

    • Team Baader

      in addition to the T-Ring Nikon to T-2 ( http://www.baader-planetarium.com/en/baader-t-ring-nikon-to-t-2.html )
      you need the Hyperion T-Adapter M43 to T-2 ( http://www.baader-planetarium.com/en/baader-hyperion-t-adapter-m43i--t-2a-(m42x0.75).html )