• Mar 22, 2026 choosing and using a refracting telescope 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 By Michelle Hills
