Is this as dark as it gets?

[Bart]

Hello all,

I wondered if anyone can tell me if this time of year is as dark as it gets. I realise the night will get longer, but will they darken? I got my first telescope in Jan last and I seem to remember the sky was darker. I dont think the LP has got much worse recently. I wondered had it anything to do with going from a 6" to a 10"? Does the background sky look less black with more aperture? Thanks for any comments.

Bart

[Ramjo]

I noticed the same when I went from a 6 to a 8, expecting to be amazed, objects only very slightly bigger, sky brighter, then the same again when I went from a 8 to a 10

[Ags]

The sky blackness (and nebula dimness) depend on the the aperture divided by your magnification. This ratio is known as the exit pupil. So if the sky background was black in the 6 inch at 150x then it will be black in the 10 inch at 250x.

[lukebl]

A crucial factor is 'astronomical twilight' which marks the start of proper darkness and ends a lot later that 'civil twilight'. For instance, at the moment civil twilight for me ends at around 17:10, but astronomical twilight doesn't end till 18:30. This period of true darkness obviously is longest around the solstice.

However, I have found the biggest influence on sky darkness in areas subject to any light pollution is air humidity. Moisture in the atmosphere reflects street lights, and can have a huge impact on the darkness of the sky. I live in a suburban area with quite a lot of street lights, but one night a couple of weeks ago when the air humidity was exceptionally low I could see dark skies almost to the horizon. You need to keep an eye open for these rare windows of opportunity.

[Ant]

There seems to be a lot more almost invisible high cloud around, I think that this may be the cause.

I'm hoping that as winter comes there'll be less of the high clouds and a darker more transparent sky.

Cheers

Ant

[Kai]

If you live under flight paths then you do also suffer from the exhaust gas hanging around at high altitude as well.

I used to live near Canterbury and the amount of planes flying over is incredible and it does effect the seeing without a shadow of a doubt

[hemihaggis]

what we are looking for a settled period of high pressure in the depths of winter , low humidity , cold clear air , wooly socks ....

[brantuk]

Download this plantarium and click on "insolation" for a detailed graphic showing exactly how dark it gets all through the year. There's also lots of other interesting items in there too. Enjoy

Sky View Cafe - Astronomy - Star Charts and Ephemeris

[anthony2577]

Another relevant factor is the climatic aspects.

The frequency of good seeing nights here in South Bucks seems to have reduced considerably over the last 10years, due I believe to increased periods of high humidity.

anthony 2577