NZer captures first photos of another solar sytem

[FlyingKiwiGirl]

Could someone explain how he did this please, in layman's language

An astronomer has captured the first amateur pictures of another solar system from a tiny telescope in his back yard.

Rolf Olsen, a New Zealand based astrophotographer, has published the first non-professional pictures of the disk of debris and dust swirling around Beta Pictoris, a very young solar system .

Incredibly, the 12 million-year-old system was captured with only a 25cm telescope.

The material that forms the proto-planetary disc around Beta Pictoris has been photographed by large observatories often before, but it was not thought possible for amateurs to take a picture of the system, because of the glare from the star itself.

But by capturing an image of a similar star and subtracting it from the picture of Beta Pictoris, Olsen was able to eliminate the stellar glare, revealing the dust disk.

Olsen says he got the idea by reading a 1993 Harvard paper titled 'Observation of the central part of the beta Pictoris disk with an anti-blooming CCD'.

First he gathered fifty images of Beta Pictoris.

Then he collected similar pictures of another star that is similar in colour and brightness- Alpha Pictoris.

He subtracted the image of the second star, removing the glare.

The raw image of the material disc looked scrappy, so he blended it with the original image of Beta Pictoris using photo editing software.

But even so the picture is being hailed as 'a milestone.'



NZer captures first photos of another solar sytem - World - NZ Herald News

[ravncat]

Looks like he used a fairly large telescope, and image stacking. So he took a bunch of pictures of the star with the solar system so that he could get rid of noise, then he took images of a similar star, so he could subtract the brightness and color from his image, which is what the black spot is. This let him "remove the star" but "keep the disc" (the fuzzy area around the black spot).

not sure how cropped the image is, either way, pretty cool.

[ArmySoldier777]

I think you're mostly right, but a 25cm telescope really isn't that big at all. It's not tiny, but still not very big. I wonder what size lens he used

[FlyingKiwiGirl]

OK, so why didn't he just put a black dot on top of the star, why did he need to take a picture of another similar star? And what does he mean by "and subtracting it from", I know what subtracting is but how would he have "subtracted" it?

[Jonbar18]

Originally Posted by FlyingKiwiGirl

OK, so why didn't he just put a black dot on top of the star, why did he need to take a picture of another similar star? And what does he mean by "and subtracting it from", I know what subtracting is but how would he have "subtracted" it?

Subtracting means just taking it out of the image...in this case by covering it. He could have just used a black dot, but taking a picture of a similar star seems a lot easier than calculating the size the dot needs to be to cover just the right area

[ravncat]

Well, 25 cm is a 10 inch lens - that's diameter of the lens - which is alot of light gathering - much more than a standard (for beginners) 3 inch tele... I don't know if he was using another lens or not, because the article didn't say if he was shooting afocal or not.

Originally Posted by FlyingKiwiGirl

OK, so why didn't he just put a black dot on top of the star, why did he need to take a picture of another similar star? And what does he mean by "and subtracting it from", I know what subtracting is but how would he have "subtracted" it?

A black dot on the star would have given him trouble with what was the star and what was the cloud - he wanted to get rid of just the glare without getting rid of objects in the glare. He knew he had Star + Cloud and wanted to eliminate just the star - so he found a different star, of similar light spectrum, and used that to "subtract" the star. (I wish i could draw a diagram here) but the idea is that he had no real way of distinguishing from what was glare and what wasn't. By finding a similar star he could make a good approximation of the glare brightness - and after subtracting that he'd be left with no glare, but objects in it would remain.

The subtraction would be via luminosity. It's a filtering trick. The other way he could have done it is with an "occulting disk" But that would require a very precisely sized disc placed infront of the telescope that matched the size of the star. This is done alot for imaging mercury - because it is so close to the sun. (Or to see the corona, etc.)

[Vincent_G]

Originally Posted by FlyingKiwiGirl

Could someone explain how he did this please, in layman's language

Photoshop ..

[FlyingKiwiGirl]

Great! Thanks guys........I think I understand A little lightbulb came on with Ravncat's description of how that 2nd star worked. It sounds very complex and while I know some people obviously enjoy that sort of stuff, it doesn't sound too exciting to me.......until you hit the jackpot of course!

I wonder how many have this for their bed-side reading!
Olsen says he got the idea by reading a 1993 Harvard paper titled 'Observation of the central part of the beta Pictoris disk with an anti-blooming CCD'.

[metallion58]

He used a CCD camera. It is made specifically for astro-imaging. They look like these but work on the same principle as our DSLR.
As for the telescope, the article doesn't mention the type. But the scope is used as the lens for the CCD camera. So, assuming it was a Newtonian, he had something like a 10", f1200 at f/4.7 lens. If it was a Schmidt-Cassegrain (other wise known as SCT, that would give him a 10", f2800 at f/8 lens.
They would have to be be on German equatorial mount to compensate for earth's rotation during long exposures.
That's for the imaging part of the equation.
As for the image treatment, it's already been described, in laymen's term, although it's a lot more complicated and time consuming than that.

[Biomech]

On the subject of night photography
How the hell do you photography the stars?

I've tried with an f/1.7.

Even a few seconds on the shutter creates light trails, how would you photography stars without trails? If you crank the ISO up enough it's just too noisy to use.