What filter if any for Bortle2 skies and a waning moon?

[RugbyRene (Rene)]

Hi all,

Apologies if this isn't the correct place for this.

In June I'll be travelling to Bortle Class 2 skies on the South Coast of NSW. and will be taking my rig down to take advantage of the dark skies.

The moon will be waning from 93% to 58% over the week I'm there. I'm worried that such a big moon will washout what will be dark skies. So my question is what filter should I use to to block out the moon. I'll be shooting with a ASI294 OSC.

Am I better shooting narrowband over broadband? Will a moon and skyglow filter allow me to shoot broadband.

Any advice would be appreciated.

Rene

[Atmos (Colin)]

I’d suggest it depends on what you’re wanting to photograph. Below is a bright galaxy shot from my Bortle 7 backyard under a near full moon.
NGC 253

Another is shot under dark skies and a full moon.
NGC 3372

The galaxy under the worst of conditions is probably less impacted than the Nebula under dark but moonlit skies. Shooting small bright objects aren’t as impacted by the moon as large diffuse regions.

So, it depends on your target. Narrowband allows for imaging under anything where as unfiltered, that can depend on what you’re intending to do.

[RugbyRene (Rene)]

Originally Posted by Atmos

I’d suggest it depends on what you’re wanting to photograph. Below is a bright galaxy shot from my Bortle 7 backyard under a near full moon.
NGC 253

Another is shot under dark skies and a full moon.
NGC 3372

The galaxy under the worst of conditions is probably less impacted than the Nebula under dark but moonlit skies. Shooting small bright objects aren’t as impacted by the moon as large diffuse regions.

So, it depends on your target. Narrowband allows for imaging under anything where as unfiltered, that can depend on what you’re intending to do.

What filters were you using in each case?

Rene

[Atmos (Colin)]

No filters at all. The first was taken with a ASI094 OSC (same as a Nikon D810) without any UV/IR filter and the second was with a stock Nikon D7200.

[Placidus (Mike and Trish)]

The effect of a big bright moon can be every bit as troublesome as the effect of city lights without moon.

Since you're stuck with the moon, the choices are:

(1) As Colin said, bright broadband targets, like open clusters and bright galaxies, preferably those in a different part of the sky from the moon. There is no filter that can block out moonlight but let the light from a galaxy through.

(2) Emission nebulae through narrowband filters, most particularly H-alpha, and again in a part of the sky furthest from the moon. A 6 nM wide H-alpha filter can let through say 90% of the light from an emission nebula, but block out all but 6/(700-400) = 2% of the moonlight.

Hope that helps.
Have fun!

Mike

[skysurfer]

Originally Posted by Placidus

The effect of a big bright moon can be every bit as troublesome as the effect of city lights without moon, i.e. no better than in Sydney suburbs.

Since you're stuck with the moon, the choices are:

(1) As Colin said, bright broadband targets, like open clusters and bright galaxies, preferably those in a different part of the sky from the moon. There is no filter that can block out moonlight but let the light from a galaxy through.

(2) Emission nebulae through narrowband filters, most particularly H-alpha, and again in a part of the sky furthest from the moon. A 6 nM wide H-alpha filter can let through say 90% of the light from an emission nebula, but block out all but 6/(700-400) = 2% of the moonlight.

Hope that helps.
Have fun!

Mike

Indeed, a full moon delivers a sky not better than Bortle 8 and a 50% Moon Bortle 5, even without artificial light pollution.


Indeed Placidus gives good advice.