MnAstro Forums

A single star... or is that 18?

Since JWST is reported to be able to "look back in time", would it be this might represent the star cluster our sun was part of billions of years ago. The elongated disks of pre-planetary matter.

We have people in the club who can help with collimation...

matt_2018 wrote: ↑Fri Feb 11, 2022 2:41 pm We have people in the club who can help with collimation...

Let me know when you get up there, we'll stay here and tell you which screws to turn.

I waited 15 years and spent $10 billion dollars and all I got was this lousy Strehl ratio of 0.0001. - Chris Burke

[attachment=0]Screenshot_20220211-174053_Google News.jpg[/attachment]

This shows which image is from which mirror.

I feel so much better now, diffraction spikes and all, after taking this image when I first heard it would be the one.

A nice short video on the first light image and the collimation procedure:
https://youtu.be/QlwatKpla8s

Superb video! Another interesting factoid, the alignment star HD84406 is actually too bright for routine imaging.

I've been scratching my head trying to understand how they determined which star was from which mirror. They eluded to it in the video, but didn't come out and say it exactly. Are they using the "selfie" images to determine which mirror is brighter for each sub exposure in the mosaic? If so, that's pretty cool. If that's not how they're doing it, I'm still scratching my head.

I had the same question... Could they be using star shapes to identify the mirror corresponding to an image?

Here are the stars lined up with the corresponding mirror segments.
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Could be that once they found the star images in the mosaic, they moved each mirror one at a time and took a photo after each mirror movement to see which star image moved.

"We are pointing the telescope at a bright, isolated star (HD 84406) to capture a series of images that are then stitched together to form a picture of that part of the sky. We don’t have just one mirror looking at this star; we have 18 mirrors, each of which is initially tilted towards a different part of the sky. As a result, we’ll actually capture 18 slightly shifted copies of the star – each one out of focus and uniquely distorted. We refer to these initial star-copies as 'segment images.'

One by one, we will move the 18 mirror segments to determine which segment creates which segment image. After matching the mirror segments to their respective images, we can tilt the mirrors to bring all the images near a common point for further analysis. We call this arrangement an 'image array.'"

https://webb.nasa.gov/content/webbLaunc ... sWebb.html

Thanks Merle. That validates Mark's theory.

It also means this had nothing to do with it.

Cooling down!!
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Current status.
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Thanks for sharing!
Looks like cooling is quicker away from the shield.
Did they turn on the fans for cooling it down?! ...

Did they turn on the fans for cooling it down?! ...

Fans in space?

Sorry, that was an attempted joke... it failed...

bsk1947 wrote: ↑Fri Feb 18, 2022 10:32 am Sorry, that was an attempted joke... it failed...

I got it

I was going to suggest they should have made the whole thing out of SMAs

Deane Clark wrote: ↑Fri Feb 18, 2022 10:42 am

bsk1947 wrote: ↑Fri Feb 18, 2022 10:32 am Sorry, that was an attempted joke... it failed...

I got it

I was going to suggest they should have made the whole thing out of SMAs

What's an SMA?

The SMA is the Secondary Mirror Assembly.
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Labeled here as the "Secondary Mirror"
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Another attempted “joke”. The SMA is the dark blue circle in the upper right, the coldest mirror “segment” at 30.82K.

So the Webb is just like my Newtonians. The secondary mirror always gets coldest and dewy/frosty, putting an end to my observing session.

Dick Jacobson wrote: ↑Sat Feb 19, 2022 1:15 pm So the Webb is just like my Newtonians. The secondary mirror always gets coldest and dewy/frosty, putting an end to my observing session.

Hope they packed a hair dryer....


Merle