Takahashi Mewlon CR Extender 1.5x

Product Overview

The Mewlon CR Extender 1.5x is Takahashi's magnifying extender for the CCA-250 and the Mewlon-250CRS and Mewlon-300CRS Cassegrains. Depending on the host telescope it stretches the native focal length by roughly 1.5x, reaching as far as f/15.1 on the Mewlon-250CRS for high-resolution planetary and lunar work.

Who It's For

This is a good match if you own a CCA-250, Mewlon-250CRS, or Mewlon-300CRS and want the longest reach those telescopes can offer — high-resolution lunar and planetary imaging, or high-power visual observing, beyond their already long native focal ratios.

Key Features & Design

• Shared across three telescopes: one part, with the resulting focal length and ratio set by which Cassegrain it is mounted on.
• 44mm image circle on the Mewlon-250CRS and Mewlon-300CRS; 40mm on the CCA-250.
• 117.5mm back focus held constant across all three telescopes.
• Long-ratio result: from f/7.5 on the CCA-250 up to f/15.1 on the Mewlon-250CRS.

Optical / Mechanical Design

The CCA-250, Mewlon-250CRS, and Mewlon-300CRS are already long-focus Cassegrain designs; the EX CR1.5x extends each further rather than correcting or reducing. Because the multiplier interacts with the native focal ratio of each telescope, the resulting f-ratio differs meaningfully across the line — f/7.5 on the CCA-250's faster native f/5.0, up to f/15.1 on the Mewlon-250CRS's f/10.0 — while the back focus stays fixed at 117.5mm on all three.

Recommended Uses

High-resolution lunar and planetary imaging, and double-star and high-power visual observing, on the CCA-250, Mewlon-250CRS, or Mewlon-300CRS.

Compatibility and Accessory Notes

Takahashi publishes this extender for three telescopes.

The same three telescopes also take the companion Reducer-CR 0.73x, which Ontario Telescope carries separately, for the opposite trade-off. Spacing detail is in the Takahashi Back Focus Guide.

Good to Know Before You Order

Long focal ratios reduce image brightness per unit time: f/15.1 on the Mewlon-250CRS trades exposure speed for resolution, which suits planetary lucky-imaging more than faint deep-sky targets.

Frequently Asked Questions

Is it difficult to set up?

No — it threads to the rear cell with a fixed 117.5mm back focus on all three host telescopes, so there is no spacing to work out.

What is it best used for?

High-resolution lunar and planetary imaging, and high-power visual observing, on the CCA-250 or Mewlon CRS line.

Does the same part fit all three telescopes?

Yes — one extender, with a different resulting focal length and ratio depending on the host.

Is there an opposite option for wider fields?

Yes — the Reducer-CR 0.73x fits the same three telescopes and reduces rather than extends; send us your target list and we can help you pick between them.

Bottom Line

The Mewlon CR Extender 1.5x stretches the CCA-250, Mewlon-250CRS, and Mewlon-300CRS to their longest published focal ratios — up to f/15.1 — for high-resolution lunar and planetary work.