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This is a comparison of raw spectra taken 8 days apart showing depletion of sodium emission but increase in C2 and CN.The comet looks like it has now lost its golden colour and images are picking up more blue/green in the coma perhaps due to this increase?
David
Clear here again tonight! Also just realised that my Canon has been imaging at f/27! Wondered why I wasn’t getting the ion tail recorded, hope to do better now!
David
Comet Neowise caught in single 20s exp. with Ricoh Theta camera last night
https://theta360.com/s/jOGdKcj6M9KsLhWHUK5I5aqwq?utm_source=app_theta_twitter&utm_medium=social
David
Thanks Robin, I thought that was probably the case! So a Sodium tail is back in the running!
Have you got a spectra across the tail yet?
David
Here’s a great image and spectrum by Torsten Hansen using a star analyser and 135mm lens. The sodium tail is much straighter than the dust tail, so would definitely manifest itself towards the left. See lower image here:
Thanks for that link Robin. It looks as though the offset of the Sodium tail is just 3 degrees from that of the main dust tail in the PSI image. Presuming that this image shows south at the top, the Sodium image is offset in a clockwise direction. I have measured Andy’s image and it shows that the red tail is offset approx 17 degrees in an anti-clockwise direction. So I don’t think the red tail is Sodium.
David
That’s interesting, the colour of this certainly looks redder than sodium. But I don’t see much evidence of NH2 in the Neowise spectrum, but I guess most spectra have been centred on the nuclear region.
David
Beautiful image! I’m guessing it could be due to Na emission in the yellow?
https://britastro.org/node/23206
David
Caught this spectrum of the comet this morning showing bright Sodium line, C2 banding and I’m guessing CN emission on far left? 20 x30s with ASI 183mm and Alpy (binned 2×2 at 2.5A/pixel).Taken with 50cm f/4 Connaught Dome at NLO.David
Sorry, cloudy here in Devon. Could only catch a fleeting glance of Capella every now and again.
David
Thanks for that. i am researching Lockyer’s work on sunspots when he projected the sun’s image on to a screen with a slit in it, over which he positioned a sunspot. With his spectroscope receiving the light of the spot, (I guess it was his 7 prism one) he noticed that the spectral lines were widened. This was years before Pieter Zeeman’s discovery of the splitting of spectral lines due to magnetism and Hale’s observations linking sunspots and magnetism.
David
Was the image captured with a reflector or refractor? If the latter, the ring may have been caused by the star showing excess infrared emission hence out of focus with respect to other stars. Advise him to take another image of the same star field, but this time refocus on the star with the ring. If that sharpens then all the others will look like planetary nebulae – proving the point!
David
Thanks for the heads up! I caught a spectrum of it last night with an SA100 & C9 30x30s exp.Rotated image 90 deg to avoid galaxy: Think I’ve caught the Si II absorption line at 6127A. Cheers, David
There were quite a few field stars interfering within the coma tonight – sure it’s not a star?
David
Thanks David, I have had peculiar analemma type trails on hyperstar images before but this one was a very regular motion between each successive image. However, when you actually look at the artifact close up it shows a spiked appearance, so other than a Klingon starship it must have been a ghost image from that bright star!
David
Here is a two image blink comparison: start and end times: 02:14h and 02:25h 2020-03-23
https://www.dropbox.com/s/im2wjebof8mh083/C2019Y4_20200323_dgs.gif?dl=0
It’s also been spotted by observant non-astronomers!
Just received this query, to which I have replied.
David
Comment: Dear NLO team,
I wonder if you could help me please? On Friday night (24th May) at a out 11.30pm 2 of my friends and I watched a very strange phenomenon for a good minute, from a country lane just north of Totnes in Devon. (We were sober.) We were admiring a very starry night sky, when we noticed what looked like a horizontal band of stars moving in unison from west to east across the sky. They didn’t fade away but steadily moved, with stars at the ‘front’ end more closely spaced together than those at the back, which seemed to lag. It was completely silent. There were no flashing or coloured lights to suggest it was a plane. Really odd. It almost looked like a train was gliding along up there , with lights showing from its windows . I’m guessing this was an illusion caused by something, but would be grateful if you can explain as it has mystified us! Many thanks. Karen
It’s still there. Image taken last night May 5th with 50cm in Connaught Dome at NLO with ZWO ASI 183MM. 10 x 60s exp.
