seeing stars?

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stuck
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seeing stars?

Post by stuck »

This one is a good illustration of why you shouldn't try to photograph the night sky without a telescope. I took it when we were in New Zealand in 2012. Compared to where we live in the UK, there was much less light pollution and for the first time since I was a child I was able to look up and marvel at the Milky Way. Inspired by the sight I tried to photograph it.

The result was this 30 seconds exposure, wide angle shot. Some of the dots are stars but many are just sensor noise. Even if you squint you need a huge imagination to see anything worth seeing :grin:

With a bit of luck, this might prompt Graeme to upload a decent shot of the Milky Way.

Ken
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Re: seeing stars?

Post by BobH »

I tried that a few years ago in west Texas with a camera on a tripod and a long exposure. Of course, what I got was streaks of light, not stars or the Milky Way.
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Graeme
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Re: seeing stars?

Post by Graeme »

I haven't tried that! But I would of thought you might have captured something! Did you push your iso up to max? I've seen half decent Milkyway shots of 30 seconds at 6400 iso using a 10mm lens. A lesser fov will cause star trailing, your stars are just starting to trail. There is a rule of thumb, the 500 rule explained here.

Did you do any post processing? If you remove the black pixels (no data!) and stretch the rest you will probably find something there. (could you post up a Onedrive or Google Drive link to the file? (RAW file is best))

The centre, thickest part of the Milkyway is in the direction of Sagittarius and the best time for seeing that area of the sky is Mid summer (for Northerners) so winter is not good. But we could all get ready for next summer?!! I was toying with the idea of getting an attachment that will enable me to connect my Canon 18mm-55mm lens to my astro camera and attach to the telescope mount for wide angle shots but I hardly ever get enough clear skies to use the equipment I already have! And anyway, they contravene the 500 rule!

Regards

Graeme

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Re: seeing stars?

Post by stuck »

Graeme wrote:
29 Nov 2020, 09:03
...
Did you do any post processing? If you remove the black pixels (no data!) and stretch the rest you will probably find something there....
I did but probably with not enough subtly. When I tried to stretch it I simply amplified the noise and even with DxO's latest 'DeepPRIME' noise reduction algorithm, which is seriously impressive, I couldn't clean up what I got.

I suspect there's nothing in the data. I'd never tried anything like this before so the settings I used were a wild guess. For example, I deliberately didn't crank the ISO up to max because I knew my Canon 400D was very noisy and I knew I had to watch the exposure time to avoid star trails. This meant I ended up with:
Canon 400D
Canon 18-55 (non-IS) at 18 mm
ISO 200
f8
30 secs

Ken

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Re: seeing stars?

Post by Leif »

Graeme wrote:
29 Nov 2020, 09:03
There is a rule of thumb, the 500 rule explained here.
:laugh:
Leif.

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Re: seeing stars?

Post by ChrisGreaves »

stuck wrote:
28 Nov 2020, 19:04
... when we were in New Zealand in 2012. Compared to where we live in the UK, there was much less light pollution and for the first time since I was a child I was able to look up and marvel at the Milky Way.
We should not forget, too, that [as i understand it] the Earth's axis is oriented (a poor choice of words in this context) so that our South Pole points towards the heart of the Galaxy, with the inevitable corollary that the North Pole points away.
So that Australians and other antipodeans are gazing into the rich brightness of the Dowtown Core, whereas the rest of the world stare gloomily at the outer suburbs.

@Grame: "the 500 rule explained here."
Once I am dressed for outside I am going to toss BOTH my smart phones into the 44-gallong drum compost bin.

Cheers
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Re: seeing stars?

Post by HansV »

The center of our galaxy is in the constellation of Sagittarius, at about 29° South, so it is "visible" from much of the Northern Hemisphere...
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Re: seeing stars?

Post by ChrisGreaves »

HansV wrote:
29 Nov 2020, 13:00
The center of our galaxy is in the constellation of Sagittarius, at about 29° South, so it is "visible" from much of the Northern Hemisphere...
Fair Enough, oh Sage One!
Perth lies at 32s, and the remaining Australian Tourist Hotels lie close to that latitude.
In that sense, the vast bulk of the Aussie Population see the centre of the Milky Way pretty well directly overhead. [If I got that right]
Untitled [640x480].png
The Centre Of The Known Universe, on the other hand hemisphere lies at around 48N and is straddled by other population centres such as Telegraph Creek, San Diego, and Bristol.
That, if I've done my sums right, is a difference of 32+48 degrees of latitude, or 80 degrees.
And that is close enough to 90 to suggest that for the dense mass of population in the unblessed climes, the centre of the galaxy is "just behind that double-storey building over there".

I rest my case. Or at least, my laptop case.

(signed) "Harumph!" of Bonavista
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Re: seeing stars?

Post by stuck »

stuck wrote:
29 Nov 2020, 10:48
...
I suspect there's nothing in the data...
More messing around this afternoon adds further weight to my comment above.

Ken

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Graeme
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Re: seeing stars?

Post by Graeme »

The galactic centre is indeed at the zenith when viewed from the southern hemisphere but only in June. At the moment it's behind the Sun.

All the zodiac constellations sit on the same plane as the solar system objects appear in the sky, the ecliptic. In the winter the ecliptic rises to 60° altitude at night but only about 15° in the summer from where I live. All because the Earth's axis is tilted with respect to the plane of the Solar system.

The ecliptic is tilted with respect to the plane of the Milkyway so the ecliptic is overhead in June when viewed at night from the southern hemisphere.

If you download Stellarium you can position yourself in all sorts of places in space and time and waste another week of your life! :smile:

Viewing the celestial poles from Ecuador in fast time is fun!

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Graeme

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Re: seeing stars?

Post by stuck »

Graeme wrote:
29 Nov 2020, 18:52
...
If you download Stellarium...
Did that the last time you mentioned Stellarium
Graeme wrote:
29 Nov 2020, 18:52
...
you can position yourself in all sorts of places in space and time and waste another week of your life!...
Done that too :laugh:

Ken

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Graeme
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Re: seeing stars?

Post by Graeme »

stuck wrote:
29 Nov 2020, 18:44
stuck wrote:
29 Nov 2020, 10:48
...
I suspect there's nothing in the data...
More messing around this afternoon adds further weight to my comment above.

Ken

Can you nip back and take another shot at 6400iso?

Regards

Graeme

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Re: seeing stars?

Post by ChrisGreaves »

Graeme wrote:
29 Nov 2020, 18:52
The galactic centre is indeed at the zenith when viewed from the southern hemisphere but only in June ...
Hi Graeme, and thanks for these thoughts. I shall have fun going to sleep tonight.
I came back because I had a "gyroscopic" thought. In my previous post I had insinuated that Aussies would always have the galactic centre overhead, and I supposed that someone would start talking about "seasons" of the Earth. I had presented no argument for the southern hemisphere always pointing at The Galactic Centre. I sometimes have to force myself to see the solar planetary plane as NOT being in the plane of orbit around the Sum. But there you go.

In my mind I see The Earth as a gyroscope, a significant gyroscope, with little wiggle room, despite the mass of the sun. After all, my spinning top seems not to be affected by the earth's rotation. OK. My top spins for one minute tops, but what about naval and aviation navigational gyroscopes?

To that end I see the rotational (N-S) axis of the earth pointing to the galactic centre like an axle that, were it extended 30,000 light years (according to Eric Idle) would pass through the Bullseye.

So, I shall not push this train of thought, but will instead consider your arguments after I ...
download Stellarium you can position yourself in all sorts of places in space and time and waste another week of your life! :smile:
This will not take me a week to play with, but still and all I feel qualified to exclaim "You rat!"

Cheers and :thankyou:
Chris
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Re: seeing stars?

Post by BobH »

All of that is over my head!
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Re: seeing stars?

Post by Graeme »

BobH wrote:
29 Nov 2020, 19:37
All of that is over my head!
:laugh:

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Re: seeing stars?

Post by ChrisGreaves »

BobH wrote:
29 Nov 2020, 19:37
All of that is over my head!
:clapping: :clapping: :hairout: :clapping: :clapping:
Cheers
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Graeme
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Re: seeing stars?

Post by Graeme »

ChrisGreaves wrote:
29 Nov 2020, 19:07
In my previous post I had insinuated that Aussies would always have the galactic centre overhead...
Does this help:

DSSO7TyXUAAPQeR.jpg
ChrisGreaves wrote:
29 Nov 2020, 19:07
In my mind I see The Earth as a gyroscope,
It kind of is:

Earth-axis-rotation-precession-North-Pole-circle.jpg
ChrisGreaves wrote:
29 Nov 2020, 19:07
This will not take me a week to play with, but still and all I feel qualified to exclaim "You rat!"

You're welcome!

Regards

Graeme
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stuck
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Re: seeing stars?

Post by stuck »

Graeme wrote:
29 Nov 2020, 18:57
...
Can you nip back and take another shot at 6400iso?
...
Love, too. I just need your credit card details, to pay for the flights and hotels and other expenses.
:cheers:
Ken

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Re: seeing stars?

Post by ChrisGreaves »

Graeme wrote:
29 Nov 2020, 20:47
Does this help?
Somewhat!
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