May sky VS August sky quality?

[gingerman]

Likely a stupid question, but I hope someone can share their knowledge & experience to clarify...

A few days ago, I've been able to shoot astro-landscapes in Bortle 2 location for the first time in my life. Previously, it was Bortle 3 at best for me (all using LightPollutionMap website using VIIRS 2015, so not entirely hard facts). No moon in the sky in both cases. Although I could see the MW with my naked eyes in both cases, the Bortle 2 May sky looked washed out compared to August Bortle 3 sky, even in zenith, 3+ hours after sunset and 2+ hours before sunrise, in both cases. I didn't expect this, although it is possible that my memory is tricking me.

So, I was wondering - is there any reason why same Bortle level May sky would look more washed out than in August?

 

[W5JCK]

It could depend on location and seasonal weather patterns. In my location spring is wet, the air almost always moist, if not full of moister. You are looking through a few hundred miles of atmosphere even when looking straight up, and a lot more if you look toward the horizon. The more moisture and dust etc. in the atmosphere, the less "seeing' in the views. August in my location is hot and dry, May wet and yucky. In Bortle 2 you will likely not even notice high clouds due to the less amount of ambient light, so you might not even realize it is a bit cloudy or hazy, or that a recent dust storm has darkened the view.

 

[Alen K]

In Bortle 2 you will likely not even notice high clouds due to the less amount of ambient light, so you might not even realize it is a bit cloudy or hazy, or that a recent dust storm has darkened the view.

Dust Storms can be bad news for astrophotography. I was recently on the island of St. Maarten/St. Martin. I wasn’t there to do astrophotography but brought some equipment just in case I got a chance. Unfortunately, dust from the Sahara (all the way across the Atlantic Ocean) made the skies terrible, especially near the ocean horizon line. I was hoping to photograph eta carina, which would have been low but was visible over the ocean with no light pollution in that direction. No dice. I couldn’t even see stars that low, only much higher up.

Another killer is smoke. That has ruined some shots on several nights when shooting low in the sky. Other nights were ruined completely (could hardly see stars even overhead). Wild fires hundreds of miles away can be a PITA. (But such a problem is totally insignificant compared to the problems of people who lost lives or homes as a result of those fires.)

 

[gingerman]

Thank you, both. Dust in the air, or something similar, is likely the reason - I now realise I was seeing some particles constantly moving in my flash light beam, and those weren't insects.

 

[nighthiker]

Thank you, both. Dust in the air, or something similar, is likely the reason - I now realise I was seeing some particles constantly moving in my flash light beam, and those weren't insects.

Hi!

Astronomical seeing conditions: https://www.meteoblue.com/en/weather/outdoorsports/seeing/london_united-kingdom_2643743

There is also 'air quality': https://www.meteoblue.com/en/weather/outdoorsports/airquality/london_united-kingdom_2643743

Aerosol forecast: https://atmosphere.copernicus.eu/ch...tion=classical_europe&valid_time=202405100300

The 'usual' reason for bad seeing is simply water vapor. Dust might be worse, but is less frequent.

 

[gingerman]

Thanks for the links, never heard about this site before.