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James Webb Space Telescope


Mike JW
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Last night I actually had clear skies - cold and dry.

The main aim was to track down the JWST as it steadily heads out to its orbital position. It is in Monoceros at around the mag 13 mark.

Image below - it is there!!!! but how could I be sure? I knew I was spot on with the RA/DEC

1195824448_JWST05Jan22_07_47_49.png.ce7f54c287f3c3f36af6782509f14ef6.png

Image below.

Patiently watching - yep it is there or is it?

762369525_JWST05Jan22_07_48_15.png.6991a7ce0c24663013b0bbe8c4061d93.png

Hooray - there it is - so pleased to have got it

1302011899_JWST05Jan22_07_49_05.png.0e6bd2ae33debdb98d47eb4458b0eedb.png

The info says 70 x 5sec subs. I actually took sequence of about 120 subs and then selected the best ones.

At the time JWST was 574,000 miles away and travelling at about 360 mph (I think). (just checked my sums and it nearer to 1100mph - thanks Stu - see below)

Below is a gif file to show how the JWST was moving

1538422178_JWST05Jan22_08_13_06.gif.a7473557f9c00a28326b45f6d8ca3f3e.gif

Mike

Edited by Mike JW
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Excellent capture @Mike JW, that can’t have been easy! It is brighter than was reported on SkySafari but then I thought mag 24 was a bit off! I wonder if anyone has seen it visually?

Checking the ‘Where is Webb?’ site, it gives a speed of 0.3050 mi/s. Multiplying by 3600 gives 1098 mph which seems more likely given how far it still has to run.

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Looks like another entry for the 'things animated in the sky SGL image competition'.  This JWST has rather captured the imagination of some SGL members hasn't it?  Quite a challenge to definitively prove you've you've really spotted it.  I'm surprised at how quickly it appears to move.  Once it gets to where it is going will the 'apparent' movement across the sky persist (i.e. will it track an orbit like the ISS) or will become a stationary point in the sky (subject to the earth's rotation 'apparent movement') like a star is?

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45 minutes ago, Martin Meredith said:

That's really marvellous, Mike. I'd like to do this myself if it ever clears over here...

Did you try making a GIF of the subs (as opposed to the evolving stack)? The movement ought to appear smoother.

Martin

Hi Martin,

I did a gif of the evolving stack, hence the continuous track of the JWST.  One reason why the movement is jerky could be because so many subs were dumped so the time frame could be 5 secs intervals or in some cases 20sec interval. The wind kept rocking the scope and being so low down there was quite a lot of star wobble.

Here is the gif of the subs

1221725292_JWST05Jan22_10_53_48.gif.a4457ad3fa305f6ab1f47733d779467d.gif

Mike

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21 minutes ago, JOC said:

Looks like another entry for the 'things animated in the sky SGL image competition'.  This JWST has rather captured the imagination of some SGL members hasn't it?  Quite a challenge to definitively prove you've you've really spotted it.  I'm surprised at how quickly it appears to move.  Once it gets to where it is going will the 'apparent' movement across the sky persist (i.e. will it track an orbit like the ISS) or will become a stationary point in the sky (subject to the earth's rotation 'apparent movement') like a star is?

I imagine it will have a rather a convoluted motion in the sky, partly driven by its orbit around the L2 point and partly due to the Earth’s rotation. I’m not sure if any of the apps like SkySafari or Luminos are modelling this correctly yet, pretty sure they aren’t.

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Thanks every one for the feedback, contributions and the obvious enthusiasm for this observation. Made for a nice change to my galaxy hunting (which I also did last night as well as some visual observing of double stars).

Mike

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1 hour ago, JOC said:

Looks like another entry for the 'things animated in the sky SGL image competition'.  This JWST has rather captured the imagination of some SGL members hasn't it?  Quite a challenge to definitively prove you've you've really spotted it.  I'm surprised at how quickly it appears to move.  Once it gets to where it is going will the 'apparent' movement across the sky persist (i.e. will it track an orbit like the ISS) or will become a stationary point in the sky (subject to the earth's rotation 'apparent movement') like a star is?

The 'movement' is largely parallax due to the observers position moving as the Earth spins. Someone on CN has posted his analysis of the movement over a relatively short period and was able to compute the distance to JWST to a very good accuracy.

 

Mike's images should be able to do the same, just need the pixel scale and time of first and last image.

Edited by AstroKeith
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32 minutes ago, AstroKeith said:

Mike's images should be able to do the same, just need the pixel scale and time of first and last image.

I have the time of the first and last image. What is pixel scale? how do I find that out?

Mike

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50 minutes ago, Mike JW said:

I have the time of the first and last image. What is pixel scale? how do I find that out?

Mike

A plate solver would usually give you that. Its the size, in arc seconds of each camera pixel. You might have measured this before?

When you have the size of a pixel in arc secs, then zoom in on your combined image and count the pixels between first and last image. Now you've got the total arc sec the JWST moved over the time elapsed.

From the time elapsed between first and last images, work out how far you moved due to earth's spin. Then thats your parallax base line to calculate JWST distance.

I'll do the calcs if you can give me the first and last times and the distance travelled in arc secs on the images.

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Hi Keith

I am someone who failed A-Level maths and struggled with O-Level maths and then whilst doing my Biology Degree I had to go on a special maths course to enable me to somehow cope with Population Statistics - never did understand what I was doing!!!

Anyway, here goes.......

1st image at 21.02.31. Last image at 21.20.16. (17 minutes and 45 seconds)

Pixel count is 31.

Pixel size: I came across this formula 206.265 x (camera pixel size) x focal length. I use a focal reducer on my set up so focal length is not likely to be that accurate. Plugging in the data and I get a figure of 0.9899482 arcsecs for each pixel.

How far did I move?  My latitude is 51.3270 N. (height above sea level of 50m). The earth spins at the equator - 1037.69mph. Using cos (latitude) x 1037.69 I calculate that I was moving at 489 mph.

Is this all the info you need?  I will be staggered if the final answer is anywhere near the actual figure. Fun hunting out this info.

Thanks,

Mike

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Inspired by Mike JW's shots of the JWST I had a go myself on the evening of 5 Jan. The gif feature in Jocular was a good way to pick out the moving telescope.

578256111_JWST06Jan22_12_57_45.gif.931702abbecc6c7d58e7126ec6fa980d.gif

 

50 x 15 second subs.

Seemed to work pretty well.

 

Bill S

 

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On 05/01/2022 at 14:05, Mike JW said:

Hi Keith

I am someone who failed A-Level maths and struggled with O-Level maths and then whilst doing my Biology Degree I had to go on a special maths course to enable me to somehow cope with Population Statistics - never did understand what I was doing!!!

Anyway, here goes.......

1st image at 21.02.31. Last image at 21.20.16. (17 minutes and 45 seconds)

Pixel count is 31.

Pixel size: I came across this formula 206.265 x (camera pixel size) x focal length. I use a focal reducer on my set up so focal length is not likely to be that accurate. Plugging in the data and I get a figure of 0.9899482 arcsecs for each pixel.

How far did I move?  My latitude is 51.3270 N. (height above sea level of 50m). The earth spins at the equator - 1037.69mph. Using cos (latitude) x 1037.69 I calculate that I was moving at 489 mph.

Is this all the info you need?  I will be staggered if the final answer is anywhere near the actual figure. Fun hunting out this info.

Thanks,

Mike

Hi Mike, sorry for the delay - I  missed your post with the data in.

First answer I got was way wrong. I suspected the pixel scale so I put one of your images through a plate solver and got a pixel scale of 1.56 arc sec. (see result from astrometry.net below)

I get 383.km moved on Earth (straight line between observations not along the surface)

This then computes to a distance to JWST of 818,030km or 508,300 miles. Well done!!

 

The biggest error is your estimation of the pixel count at '19' a minimum error budget would be +/-1 pixel, but it could be up to double that as you were estimating the position of each end separately? So I compute an error band of up to +/- 51000 miles or 84000km

Keith

Screenshot 2022-01-08 at 15.19.14.png

Edited by AstroKeith
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Hi Keith,

Thank you for doing the maths. A pleasing result. 

In your post you mention 

4 hours ago, AstroKeith said:

The biggest error is your estimation of the pixel count at '19'

Where did the figure of 19 come from? I counted 31 pixels from start to finish of the track of JWST.

If I feed into  http://astronomy.tools/calculators/ccd_suitability my telescope details (15" Dob and at f3.5) it gives me a 1"/pixel. To get a figure of 1.56"/pixel my scope would have to be operating at about f2.2 - no way is it doing that? - the coma would be a nightmare. Am I making a mistake somewhere?

PS - I did not think about who Keith might be when your first post came up - silly me. We know each other - I am Andrew R. friend who pops down to Haw Wood - still remember that excellent flapjack of yours at my last visit.

Mike

 

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2 hours ago, Mike JW said:

Hi Keith,

Thank you for doing the maths. A pleasing result. 

In your post you mention 

Where did the figure of 19 come from? I counted 31 pixels from start to finish of the track of JWST.

If I feed into  http://astronomy.tools/calculators/ccd_suitability my telescope details (15" Dob and at f3.5) it gives me a 1"/pixel. To get a figure of 1.56"/pixel my scope would have to be operating at about f2.2 - no way is it doing that? - the coma would be a nightmare. Am I making a mistake somewhere?

PS - I did not think about who Keith might be when your first post came up - silly me. We know each other - I am Andrew R. friend who pops down to Haw Wood - still remember that excellent flapjack of yours at my last visit.

Mike

 

Don't know why I wrote 19! - I used your 31.

You can see from the screen grab from the plate solve that it has found 1.56 arc sec based on that image. Strange why it doesnt match to your expectations. If you let me have the sensor details I'll see what I get?

Glad we met up! I'll pass on the compliments to the baker!

Keith

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I had begun to suspect something wrong with the pixel count but not sure how to sort that one. There was not any binning. I have just sent you an image on your email (private not via the forum).

Cheers,

Mike

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Final update to anyone following the attempt to calculate the distance from my image to the JWST. 

At the time JWST was around the 924,000km mark. Re-doing the calculations Keith (I) came up with a figure of around the 1,028,000 Km mark. Rather a large error but fun and absorbing to give the idea a go, so thank you to Keith for doing the maths. Quite likely a better result could have been obtained if I had run the sequence for much longer than the 17 minutes.

Mike

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