BSL Deep-Sky Imaging – Refracting Telescopes (Refractors)

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What is a Refracting Telescope?

Refractors use glass lenses to gather and focus light.
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They are popular for deep-sky astrophotography due to their sharp imagery, high contrast, and low maintenance requirement (no mirrors to align / collimate).

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Apochromatic (APO) Triplet / Quadruplet:
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Uses extra-low dispersion (ED) glass elements to eliminate chromatic aberration (colour fringing around stars).
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Ideal for imaging.

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Achromatic Doublet:
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Budget-friendly, but introduces visual colour fringing around bright stars, requiring violet / minus-violet filters.

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Field Flatteners & Reducers:
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Field Flatteners:
Essential optical accessories used with refractors to produce a flat focal plane across large camera sensors.
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Reducers
Reduce the focal ratio for faster exposure times.

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