Jeff Crilly
unread,Jul 28, 2026, 11:35:02 PM (6 days ago) Jul 28Sign in to reply to author
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True — big city pavement is going to have a negative effect on seeing. But what we’re really taking about is local seeing. Large surfaces that retain heat will of course cause local seeing problems. Eg House roofing, tall buildings etc.
While I do get the idea that local seeing may be affected by paving around the observing area, I do wonder exactly what characteristics of the paved are must exist in order to cause a significant and noticeable effect on local seeing.
(For example, light colored pavement? How long does it really take
I have some (possibly anecdotal) experience in this area.
Lick Observatory is completely 100% paved around the main observatory building (where the 36” and 40” domes are located). And not a single lane road — it’s a parking lot for like 50-70 vehicles. In the 25+ years I’ve been observing at Lick with a variety instruments ranging from well corrected SCTs to 6” refractors (no to mention the 36” and 40”), I have experienced excellent seeing (the best I’ve seen anywhere) on many occasions. Additionally , 100% of that observing was done in the summer months (as opposed to winter where there is an occasion dusting (or more) of snow up there).
So while I am sensitive to paving and local seeing… and especially weary of the effect in neighborhoods and cities, I somewhat question the effect in areas where the paving is limited, and the majority of the observing area is surrounded by grassland.
And, fwiw, with the rest of the existing park paved , I would wonder how much of the park has been causing local seeing degradation over the years.
Also of note is this: at the FP observatory pads the “good” direction is to the east and southeast. (West - where the road lies — is kinda useless due to light pollution…Oh, and the tower.). And it turns out there is nothing but grasslands to the “good” direction.
OTOH, dust on optics will result in decreased optical transmission over time and require more frequent cleaning potentially, damaging said optics.
YMMV