How do I know which M42 Spacer Kit ring to use for my RASA 8 and ZWO camera?
First, find the required back-focus for the RASA 8 with its M42 adapter, which is 25mm. Then, find the back-focus of your ZWO camera (for example, 17.5mm). Subtract the camera's back-focus from the required back-focus (25mm - 17.5mm = 7.5mm). You would need the 7.5mm spacer ring from the kit to achieve perfect spacing.
Which spacer from the M42 Spacer Kit do I need for my EdgeHD 8" and a ZWO camera with a filter slider?
To use a camera with a Schmidt-Cassegrain or EdgeHD telescope, you typically need to meet the 55mm back-focus standard. The 30mm spacer ring is specifically designed to be combined with ZWO cameras and their filter sliders to achieve this 55mm distance, ensuring a fully illuminated and corrected field.
What does "M42 x 0.75" thread mean for the M42 Spacer Kit?
M42 x 0.75 refers to the thread specification. "M42" means it is a metric thread with a 42mm diameter, and "0.75" is the thread pitch in millimeters. This is the universal standard for "T-threads" or "T-mounts" in astronomy, ensuring these spacer rings will be compatible with the vast majority of telescope T-adapters, T-rings, and astrophotography cameras.
Are the rings in the M42 Spacer Kit labeled?
Yes, each of the three rings (7.5mm, 12mm, and 30mm) is labeled with its length. This makes it easy to identify the correct spacer you need for your setup without having to measure them each time.
What is the purpose of the glare-threaded interior on these spacers?
The blackened and glare-threaded interior surfaces are designed to trap and absorb any off-axis stray light that enters the optical train. This prevents internal reflections that can lower image contrast, wash out faint details, and introduce artifacts into your astrophotos. It's a critical feature for high-contrast imaging.
How do I install a spacer from the M42 Spacer Kit with a DSLR camera?
For a DSLR, you will typically have a T-Ring that attaches to your camera body and a T-Adapter that slides into the telescope's focuser. You would place the required M42 spacer ring between the T-Ring and the T-Adapter to add the necessary distance.
