Astro tips and timings.

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nick16

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All,

I am aware of the impending dark nights due to the new moon. (18th Dec)
Therefore i am hoping to head out on possibly Sunday 17th to see if i can get some Astro shots.

Being new to this type of shooting i have brushed up on a few good tips, however i am unsure when the darkest time to be shooting is. Im guessing around 2-3am? I am located in the South East of England.
I have a milky way grade dark sky site about an hour away, so i might look to go there. - alternatively i will stay closer to home and visit that site in the spring when the milky way is at its 'best'.


Lastly, im aware of a calculation in order to establish a rough shutter speed time?
I will be shooting Nikon DX and using an 11-16mm f/2.8 lens. (Probably staying on 12mm) - 18mm with crop factor accounted for.

Can anyone advise.

Thanks!
 
To get the stars to show are points rather than trails use the 500 rule -

Maximum exposure in seconds to prevent trailing = 500/(focal length of the lens x the crop factor of the camera).

Therefore in your example the max exposure will be about 27s. This is not a hard and fast rule as a star's apparent movement depends where it is in the sky, but it is a good starting point to experiment from.

Focussing at night can be a problem. You can try setting the lens to the infinity mark, but some lenses focus on infinity at a point slightly away from the mark. Another way is to focus on a distant object during the day and note when the lens is set, and use that position at night.

At a dark site a torch(a head torch makes things easier) that can give out red light is very handy as it stop you losing your night vision every time you need to turn it on.The only drawback I have found to a red torch is it is easy to forget it is on. I have spoiled a few shots by forgetting to turn it off and accidentally shining the light into the lens while taking the shot.

There is no need to wait until 2 or 3 am, unless you want something specific. At present the Milky Way cuts the NW horizon at a steep angle at around 9pm and at a dark site it will be dark enough then.

Have a look at Stellarium. It is free to download and shows the night sky for any location on any day (well up to many years in the future).

Dave
 
Thanks for the advice Dave.
I am all set for head torches and will be downloading software like stellarium tonight.
I do need to get a reliable compass however!
 
I can’t find this free app. I have found one but it says it’s 2.99.
 
AndyG123 said:
I think its free on pc and Mac and chargeable on Android and ios
Click to expand...

I was about to agree with you Andy about Android and iOS, as it is often the way with some software, until I went to the Stellarium site (http://stellarium.org/en_GB/ ). There isn't a version for Android and iOS, so I'm a bit puzzled.

Dave
 
nick16 said:
Thanks for the advice Dave.
I am all set for head torches and will be downloading software like stellarium tonight.
I do need to get a reliable compass however!
Click to expand...

Your eyes will get used to the dark quickly enough and you should be able to see the Milky Way with the naked eye.

Something I do is shoot with mega high ISO and shorter exposure time for my test shots to get it framed how I like then I reduce the ISO and set the correct shutter speed.

Focussing at 100% in live view on a bright star helps.

Full dark is achieved at about 6pm this time of year, unfortunately if you leave it too late the best bit of the Milky Way is setting I believe.
 
I had a check on stellarium and 9pm seemed optimal with the MW being a WNW direction.
However the cloud came in and so did the rain killing off all attempts.
...there is always next time!
 
Tringa said:
I was about to agree with you Andy about Android and iOS, as it is often the way with some software, until I went to the Stellarium site (http://stellarium.org/en_GB/ ). There isn't a version for Android and iOS, so I'm a bit puzzled.

Dave
Click to expand...
It should be available in the play store. They list it on the website because downloading the apk and installing it directly would essentially give it away for free without setting payment up on the website. So with the play store Google manages payments and they release updates as and when needed.
 
Craig_85 said:
Focussing at 100% in live view on a bright star helps.
Click to expand...

Yes. This find a star bring it to center in your view finder. Zoom in and any minor adjustments of focus seem huge when zoomed in..
I also have my camera set up to back button focusing so the shutter button doesn't focus. And I then
focus on manual. I then switch to af. My lens seems to kinda lock focus more when in auto focus and I'm always concerned about the focus slipping especially when pointing towards the sky. Probably me been paranod.
 
AndyG123 said:
I then switch to af. My lens seems to kinda lock focus more when in auto focus and I'm always concerned about the focus slipping especially when pointing towards the sky. Probably me been paranod.
Click to expand...
Interesting technique. I back button focus in MF most of the time, but never thought of turning that off to lock the focus...
 
The Milky Way can still be seen in the winter but it's pretty vertical and also a lot thinner in the sky. This is due to the different positions of the Earth in its orbit around the sun. In summer we are looking more towards the centre of the galaxy and in winter out towards the outer spiral arms where it is not as dense.
 
Is the milky way visible at this time of year? I'm based in north Gloucestershire. If anyone knows or any good locations to shoot it without light pollution?!
 
Tringa said:
To get the stars to show are points rather than trails use the 500 rule -

Maximum exposure in seconds to prevent trailing = 500/(focal length of the lens x the crop factor of the camera
Click to expand...

This worked well for film but with modern high res sensors will rarely result in point stars. The NPF Rule is more accurate:

(35 x aperture + 30 x pixel pitch) ÷ focal length = shutter speed in seconds. Pixel pitch = the camera sensor’s physical width in millimeters ÷ number of pixels in width x 1000 to measure it in microns.
Source: https://petapixel.com/2017/04/07/npf-rule-formula-sharp-star-photos-every-time/

At 12mm on DX this gives an exposure time of 17 seconds.

Obviously it's a bit more complicated than the 500 rule for calculating in the field: I highly recommend PhotoPills for astro and landscape work, as it includes amongst other things an NPF Calculator. If you don't have that, using a '300 rule' will yield better results.
 
That's interesting and a new one to me, I will give it some consideration.
 
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