This 70mm double-separation blue membrane lens, offered inF300/360/400/500/700/900mm focal lengths, is a versatile accessory for DIY astronomical telescopes. Its double-separation structure reduces optical aberrations, while the blue anti-reflective coating enhances light transmittance and cuts down glare for clear imaging. With a standard 60mm caliber, it seamlessly fits most matching telescope setups, making it ideal for hobbyists and beginners. Whether for wide-field stargazing or planetary observation, this lens delivers consistent performance to support customized telescope builds and outdoor viewing needs.