Milky Way In Bortle 7?

[Arran townsend]

Hi all, quick question, I live just outside birmingham, I have bortle 7 skies I can't see the milky way with my eyes or with long exposures, my question is if I take several exposures in the the milky way's direction, would I get be able to see the milky way?

[Stu]

13 minutes ago, Arran townsend said:

Hi all, quick question, I live just outside birmingham, I have bortle 7 skies I can't see the milky way with my eyes or with long exposures, my question is if I take several exposures in the the milky way's direction, would I get be able to see the milky way?

I suspect the answer is probably not.

If the sky background is brighter than the Milky Way, all you will get is a brighter background, still with no detail.

You will likely need to be in a good Bortle 6 or better still 5 to start to see results.

[vlaiv]

Actually you can but it is not easy ...

For a good image you will need fast lens and a lot of total exposure, but it can be done even in very severe LP.

Processing will be a challenge as well.

Here is example:

This was taken from my balcony and I'm in bortle 7 skies (you can see evil street lights shining from below). This image is quite limited since I used short exposure (and not many of them, I think it was less than 20) because camera was mounted on alt-az mount without tracking (actually piggy backed on ST102 - it has appropriate thread to mount camera on one of its mounting rings).

Camera was Canon 760d and I used kit lens (18-55mm), so speed was F/4.5 max (I don't remember zoom and F/speed I actually used for this image).

I also wondered if I can capture it - so I gave it a go. At very best / very transparent nights you can actually start to distinguish MW near the zenith (you can tell that there is something there and you can even guess direction of it). I also managed M31 with averted vision on more than one occasion - but only when it is highest in the sky.

[cletrac1922]

Hi Guys

 

Just checked https://astrobackyard.com/the-bortle-scale/

 

bortle explanation

https://en.wikipedia.org/wiki/Bortle_scale

I came up with a bortle of 4

 

Zenith sky brightness information

Coordinates

27° 55′ 50″ S 153° 15′ 40″ E

SQM

20.82 mag./arc sec2

Brightness

0.507 mcd/m2

Artif. bright.

336 μcd/m2

Ratio

1.97

Bortle

class 4

Elevation

63 meters

 

 

John

[vlaiv]

9 minutes ago, cletrac1922 said:

I came up with a bortle of 4

Mag 20.8 is pretty decent for AP. A bit less so for visual - for visual you benefit from very very dark skies.

With AP, at some point sky noise will be approaching other noise sources, so there will not be much difference. Anything above 20.5 is a good place to do AP.

I'm currently at mag 18.5, but plan to move to ~20.8 skies by the end of the year. I did some calculations - this will reduce my total exposure time by factor of about 6 to 6.5.

So whatever signal I now capture in six hours with my scope - I'll capture in one hour in those skies - so that is quite a bit of improvement.

[cletrac1922]

vlaiv

Interesting figures

We have ranges to west of us, and go up there as well

Beautiful clear skies, which block light pollution from both Brisbane and the Goldcoast

Interesting thing, bortle map still showing 4, for that region, and expect to be less

Check event horizon for this month, club website http://sas.org.au/

Images member have taken

John

 

 

[Arran townsend]

On 20/06/2019 at 18:57, vlaiv said:

Actually you can but it is not easy ...

For a good image you will need fast lens and a lot of total exposure, but it can be done even in very severe LP.

Processing will be a challenge as well.

Here is example:

This was taken from my balcony and I'm in bortle 7 skies (you can see evil street lights shining from below). This image is quite limited since I used short exposure (and not many of them, I think it was less than 20) because camera was mounted on alt-az mount without tracking (actually piggy backed on ST102 - it has appropriate thread to mount camera on one of its mounting rings).

Camera was Canon 760d and I used kit lens (18-55mm), so speed was F/4.5 max (I don't remember zoom and F/speed I actually used for this image).

I also wondered if I can capture it - so I gave it a go. At very best / very transparent nights you can actually start to distinguish MW near the zenith (you can tell that there is something there and you can even guess direction of it). I also managed M31 with averted vision on more than one occasion - but only when it is highest in the sky.

What shutter speed did you use for each frame?

[vlaiv]

9 hours ago, Arran townsend said:

What shutter speed did you use for each frame?

Don't remember that either. In all probability it was less than 10s or max that duration. I don't remember how much subs I took - but it must have been few dozen or so (20-30 probably, I doubt it was more than that).