Celestron M42 (T-2) Extension Rings Set

Celestron M42 (T-2) Extension Rings Set

is used to set the optimal working distance of your camera on the telescope in order to achieve the best imaging quality
the set contains three extension sleeves of different lengths (7.5 mm, 12 mm, 30 mm)
for connecting your T-ring and T-adapter with standard male and female T-threads
In order to achieve the best astro images, it is important to maintain the correct working distance between the camera and telescope. If the flange focus required by your camera is not maintained exactly, the stars at the corners of the full-frame image sensors will appear stretched rather than as points.


Example: RASA 8 with a ZWO ASI 183 MC PRO camera:

Required back focus distance for RASA 8 with included M42 (T-2) camera adapter: 25mm
Back focus of the ZWO ASI 183 MC PRO: 17.5 mm
A 7.5 mm M42 spacer ring is required to achieve the correct working distance
Example: RASA 8 with an ATIK Horizon camera:

Required back focus distance for RASA 8 with included M42 (T-2) camera adapter: 25mm
ATIK Horizon back focus: 13 mm
A 12 mm M42 spacer ring is required to achieve the correct working distance
The Celestron M42 spacer set contains three spacers of different lengths to achieve the correct spacing.

use
Depending on whether you are shooting with a DSLR or a CCD/CMOS camera, there are two ways to use the M42 extension ring. If you are using a DSLR, screw the desired M42 extension ring between your T-ring and the T-adapter for your optical tube. If you are using a CCD or CMOS camera, screw the desired M42 extension ring between the camera and the optical tube T-adapter.

Below you will find an overview of which extension rings to use for our optical tubes EdgeHD, Schmidt-Cassegrain and RASA 8:

Size of the intermediate ring:
7.5 mm offers the right distance with RASA 8 for many ZWO cameras
With RASA 8, 12 mm offers the right distance for many Atik cameras
30mm brings ZWO cameras with filter sliders to the 55mm back focus standard for use with Schmidt-Cassegrain & EdgeHD
Housing
The M42 extension rings are made of machined aluminum, black anodized. The inner surfaces are blackened and equipped with a glare thread for stray light suppression in order to achieve the highest contrast. Each spacer ring has a knurled surface that provides a large gripping surface for screwing and unscrewing. The M42 extension rings are compatible with M42 x 0.75 (T-thread) camera adapters.

Manufacturer Celestron
Item number (#) 820820
EAN code 4047825046444
Net weight (kg) 0.10
Optical length (mm) 7.5mm (.29"), 12mm (.47"), 30mm (1.18")
Internal connection (telescope side) thread, T-2 (M42 x 0.75)
External connection (eyepiece/camera side) T-2 (M42 x 0.75)
compatible brands Celestron
Adapter type camera adapter