choosing and using a refracting telescope
Michelle Hills
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600mm): Wider field of view, better for nebulae and star clusters. Focal ratio (e.g., f/6, f/10): Lower ratios (f/5–f/6) are ideal for wide-field astrophotography, while higher ratios (f/10) are better for high-magnification observations. Optical Quality and Types of Lenses Q
