As I stated in a follow up post, the three two-storey houses will only probably block a small area of sky. The biggest loss will be M31 and likely the Ring Nebula. The effect of loss of sunlight may also come into play and depending on how far back the places go, I may lose some nice sunsets. Yes, I'm being selfish. I don't won't to lose any sky, no matter how small
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My other concern will be what lights will be visible from their properties, particularly on the second storey. The sky is quite dark in their direction because I'm close to the beach. Bedroom and outside lights might cause issues.