Neowise in Visible and IR

[OlDoinyo]

The comet Neowise had its perigee near the end of last month, when it reached a maximum magnitude of 3.3 (so I am told) and appeared as a dim smudge in the northern sky to the naked eye. I obtained some pictures of it; they are by no means good pictures, as I do not own the equatorial clock drive and other gear needed to obtain truly quality images of such a subject. A cursory glance about the Internet will turn up numerous better visible shots, although I was interested in infrared as well and those are not so common. The visible image below was obtained with the Sony A99v fitted with a Minolta 200mm lens; exposure was 8 seconds at f/3.5 and ISO 6400. The infrared frame was obtained with the Sony A900 fitted with a Sony/Zeiss 135mm lens and a Haida 850 filter, exposed 15 seconds at f/2 and ISO 3200. The images have been scaled to match. Alas, I do not own any equipment capable of taking a UV image of such dim subject matter, as that might have been interesting; I doubt I could have gotten much even with film.

 

 

The visible image, though noisy and afflicted with some rotational streaking, shows the basic features of the comet: the area near the nucleus shines green due to C₂⁺ ions, and the curving dust tail is clearly shown. The dimmer, straight ion tail, due mainly to CO⁺ ions, shows a faint blue. It was my hypothesis that the ion tail would not be visible in the infrared.

 

The infrared image is much the noisier of the two, as the A900 does not do well at high sensor gains, and I normally try to avoid using such settings. There is more streaking due to the longer exposure. Nevertheless, the dust tail shows quite clearly, as one would expect. As I suspected, the ion tail does not emit at such wavelengths and is not visible.

 

It is said that sufficiently good equipment can also resolve a third tail consisting of sodium ions in most comets. This was not within my ability to explore.

[colinbm]

Good on you, these are good.

[Cadmium]

Clark, Way to go, very nice, I am lame, I never went to look for it. Well done, great photos of it.

[Andy Perrin]

Nice! I took a bunch of visible photos of it, with similar quality to yours. Did not consider them worth posting (except to Instagram for friends). I tried stacking a few images by hand, which helped a little.

[otoien]

+1 on these comments, must be the first IR image I have seen of the comet (following a couple of astro photo fora). No dark nights were present here to capture the comet, and now that it getting there the comet is too weak and too low on the horizon.

[Stefano]

I tried to photograph this comet, in visible light the sky was too bright (there was also light pollution from houses and mercury-vapour lights), and so I tried in infrared, to "darken" the sky. I got something vaguely similar to a comet, but it may be my lens flaring.

[Andy Perrin]

Stefano, if those are truly Mercury vapor lights, you should get a neodymium filter to block them. The trouble is that in the US at least, we have switched over to LED streetlights which are not so easily blocked.

[Stefano]

My house is not in the middle of nowhere so I can't really pretend much, it was more an experiment than anything else. I used to go on a mountain with one of my mum's friends who has a nice telescope to look at the sky with almost no light pollution. I saw the Ring Nebula with my "naked" eye (with a telescope). I didn't see the rainbowy colors, it was too weak to activate my cones, but I saw it. I will never be able to do that from my house garden.

[Andrea B.]

Love seeing these photos! Very cool. Thanks, Clark, for posting these.