Starship Asterisk*

by **NoelC** » Tue Jan 08, 2008 12:39 am

Yes, that's the problem here. The light pollution is horrendous!

In 2005 a hurricane (Wilma) killed most of the electric power infrastructure here for about a week. The views of the sky were to die for. Sigh.

-Noel

by **iamlucky13** » Mon Jan 07, 2008 8:10 pm

Very nice picture NoelC. I couldn't see any noise at the size of the image you linked to. Looks like the new Canon sensor is quality instrument. The lighting is very attractive, although it's a pity it washes out most of the stars.

by **NoelC** » Sat Jan 05, 2008 12:03 pm

It's lens flare, plain and simple.

Lenses are comprised of a whole slew of elements, most with curved surfaces, and as such secondary reflections of bright objects can be shaped strangely. They are usually oriented (pointed, angled, whatever you want to call it) toward or away from the light source, as Lance's green flare is.

Anyone who's taken flash photos into a mirror knows this.

It's a beautiful, beautiful photo, Lance. Don't let the nay-sayers get you down.

By the way, I've recently upgraded from a 20D to a 40D and the prowess of the new model in capturing long nighttime exposures is unprecedented. While by no means a beautiful shot, consider this 40D long exposure night image: http://forum.ourdarkskies.com/gallery_i ... _85842.jpg

-Noel

by **Mushhushshu13** » Mon Dec 31, 2007 3:30 pm

You know, the camera that took the shot was left to accumulate light for a while. The thing you're talking about is probly the result of the over exposure. If I leave my camera to absorb light for two secs, the picture gts all blurry and weird.

PS: WHat exactly is that objct anyhow?? I cant find it!

FRUSTRATION![/img]

by **Lance McVay** » Sun Dec 02, 2007 8:32 am

I believe it is a reflection of the moon, colored by the lens coating. If you look at the rocks at the bottom of the scene, you will notice they are lit by a source to the left, which was the moon. The artifact shows the same phase as the moon was that night.

by **iampete** » Sun Dec 02, 2007 6:29 am

If it weren't for the star being inside the circular shape, I'd swear it had to be a real object rather than an artifact.

However, I'm curious - what kind of artifact is it, i.e., what is the cause? To the best of my understanding, lens flares tend to exhibit "rays" and/or elongations toward/away from major light sources, and aperture-type flares don't produce specific "objects", per se. Is it dirt on the lens, or on the film, or ???

by **Lance McVay** » Sat Dec 01, 2007 9:52 am

One thing to keep in mind is that this is an extremely wide lens at 12mm rectangular. It's nothing like a telescope lens in any form. I've owned fisheye lenses that weren't this wide. I'm also using it for what was most likely not its primary designed purpose, which is a lot of night time shooting with bright light sources included.

Here is an image I took last night at 3200 ISO, absolutely untouched out of the camera. I haven't even leveled the horizon. I don't think anybody is going to be arguing over whether this is a celestial body or an artifact.

[/img]

by **DerekSmith** » Tue Nov 27, 2007 7:56 pm

Hi Chris,

I had looked at his other images but not with the detail that you have.

Two of the images at least show the same effect.

I'm sold - you are right and I sign on to this being a camera artefact.

Derek

by **Chris Peterson** » Tue Nov 27, 2007 7:31 pm

DerekSmith wrote:Chris, the lens flare around the moon is white and red and large, but I doubt that the white flare is because this is a low quality lens.

That isn't the kind of flare I'm talking about. I'm referring to internal reflections between elements that produce secondary images of bright sources. They are common image artifacts, and other nighttime shots by Lance also show them.

So I stand by my original statement, I believe it is unlikely that this is a flare effect

If not a flare, then what?

by **Chris Peterson** » Tue Nov 27, 2007 7:27 pm

DerekSmith wrote:Would you like to share an example of one of your flares with us that you think demonstrates this effect. And don't forget, the flare needs to point 'away' from the light source with its brightest point furthest from the moon.

Getting the same kind of flare means using the same kind of lens. Why not just look through some of Lance's other images? Here are a few: 1, 2, 3 that show similar flaring. The small differences are explainable by considering that the Moon subtends a larger angle in its images than the artificial light sources in the other images.

Of course, very much to the point, there's no reasonable object that could explain the flare in the aurora images. Lens flare is simply much more likely than any sort of atmospheric phenomenon that was stable over a minute or longer.

by **DerekSmith** » Tue Nov 27, 2007 7:18 pm

Chris Peterson wrote: Only very low quality lenses produce lens flare that is the same color as the source. The flare is caused by internal reflections, which are off of antireflection coatings.

Chris, the lens flare around the moon is white and red and large, but I doubt that the white flare is because this is a low quality lens.

Have you ever seen or can you post an example image which demonstrates a flare like this. I have searched a large number of flare images and never come across an effect like this.

So I stand by my original statement, I believe it is unlikely that this is a flare effect, but I am keen that someone shows us an example that matches of a known flare effect

by **DerekSmith** » Tue Nov 27, 2007 6:55 pm

iamlucky13 wrote:I agree with Chris. I've seen plenty of green and magenta flares off of my lenses from the coatings.

snip..

Would you like to share an example of one of your flares with us that you think demonstrates this effect. And don't forget, the flare needs to point 'away' from the light source with its brightest point furthest from the moon.

The most chromatic artefacts tend to be iris effects, so none of these please if they just happen to be the right colour, we need a ray/cone that points 'away' from the light source.

Derek

by **iamlucky13** » Tue Nov 27, 2007 5:34 pm

I agree with Chris. I've seen plenty of green and magenta flares off of my lenses from the coatings.

Lance, another thank you for sharing your pictures and comments. I really like the reflection off the aurora off the ice to the left, giving way to the moon's reflection on the right.

by **Chris Peterson** » Tue Nov 27, 2007 4:25 pm

DerekSmith wrote:Undoubtedly, that lens open as it is on F4 is flaring quite badly from the moonlight, you can see the huge flare halo and its numerous flare spikes radiating out from the moons light source. But they are all WHITE - as they should be for a white source. However, this single spike is green and almost identical in hue and intensity to the aurora.

Only very low quality lenses produce lens flare that is the same color as the source. The flare is caused by internal reflections, which are off of antireflection coatings. Such coatings are highly wavelength dependent, and in fact usually reflect shorter wavelengths. That's why camera lenses normally appear green, blue, or violet. This lens appears to have good quality AR coatings, so only a tiny fraction of the moonlight is internally reflected- nowhere near enough to saturate to white.

The fact that the flare is the same color as the aurora can be explained by the fact that both are showing a nearly monochromatic green. Color cameras generally have problems with monochromatic sources, since they often stimulate only one pixel- in this case the green ones. As a result, two different colors of green can't be distinguished from each other.

I do not think this can be explained away as lens flare, and as its orientation is different in a subsequent shot, yet it is still present, indicates that it is real, but as yet unidentified.

You can't tell how the orientation changes, because the pictures have been cropped. But to a good first approximation, the flare points towards the optical axis of the lens (the center of the image) in both cases, just as would be expected.

by **DerekSmith** » Tue Nov 27, 2007 3:16 pm

Lance McVay wrote:Thank you all for the kind comments.

The object near the moon is, as far as I know, nothing more than lens flare. I was using a 12mm lens at full aperture, and in my experience, pointed at a bright light source, this lens will definitely flare.
snip....
Lance McVay
lancemcvay@gmail.com
http://sacredartichoke.com

Hi Lance,

I have a real problem with your conclusion as to the nature of the 'object' as being lens flare.

Undoubtedly, that lens open as it is on F4 is flaring quite badly from the moonlight, you can see the huge flare halo and its numerous flare spikes radiating out from the moons light source. But they are all WHITE - as they should be for a white source. However, this single spike is green and almost identical in hue and intensity to the aurora. If it were to be flare, then it would have had to have been auroral flare, but the auroral light source is far too diffuse to cause such an event.

I do not think this can be explained away as lens flare, and as its orientation is different in a subsequent shot, yet it is still present, indicates that it is real, but as yet unidentified.

Derek

by **Carl Horn** » Thu Nov 22, 2007 3:57 am

G'day, As a rank amateur who likes to look at NASA's "pretty pictures", I must ask if the object at 7pm to the Sun is a comet, and if it might be Comet Holmes? Cheers, Carl

by **Lance McVay** » Tue Nov 20, 2007 9:51 pm

Actually I did want to ask, what is the red glow at the base of the mountains just to the right of centre?

That's glow from the Forest Service Mendenhall Glacier Visitor's Center. Their lights do seem to have quite a red glow about them. In this photo, those lights are providing the foreground light on the brush and the icebergs.

by **podkayn** » Tue Nov 20, 2007 9:15 pm

I apologize! I thought I'd gotten to the end of the string; obviously, I didn't notice that there was another page. At least I was right.

by **iampete** » Tue Nov 20, 2007 7:01 pm

Lance McVay wrote: . . .
Actually I did want to ask, what is the red glow at the base of the mountains just to the right of centre?

I assume it's some inhabited area. I have seen long exp nighttime pix which show distant towns/villages as "glows" somewhat similar to that, although the one in this picture is much redder than I recall seeing previously.

by **craterchains** » Tue Nov 20, 2007 6:58 pm

Looks up, , , "sighs".

Some people just can't read.

Edited to add, , , , , ,

Looks down, yep, you were right, Thanks for being a vet, they are good people most of the time. Congrats on making it to retirement also.

by **podkayn** » Tue Nov 20, 2007 6:52 pm

Since the moon is overexposed, could the streak just be an artifact of the camera? Obviously, it's cold (the lake is iced over) and ice crystals could form on the lens cover and reflect light in a way which would automatically be oriented toward the light source (the moon). I know that I've often seen a movie camera record streaks when it is panned past the sun. Could this be such a streak? I'll believe this until someone proves me wrong.

by **Andy Wade** » Tue Nov 20, 2007 8:25 am

Lance McVay wrote:Again, thanks for the kind words. I've been overwhelmed with the response I've gotten today from this photo.

Lance McVay
lancemcvay@gmail.com
http://sacredartichoke.com

Well in that case Lance, I'll add mine too. It is a great picture. It looks really cold!
Many thanks from a mere stargazer in Yorkshire, England, who has never seen an aurora in his life.

Actually I did want to ask, what is the red glow at the base of the mountains just to the right of centre?

by **Lance McVay** » Tue Nov 20, 2007 3:12 am

Thank you all for the kind comments.

The object near the moon is, as far as I know, nothing more than lens flare. I was using a 12mm lens at full aperture, and in my experience, pointed at a bright light source, this lens will definitely flare.

The photo was taken early in the morning of October 4th, 2007. I'm not sure if I had changed the camera's setting for daylight savings or not, so it was either taken around 4 or 5 am.

The moon was just a crescent, and there was no visible aurora that night, just a faint light that outlines the mountains from the sky, which is sometimes hard to tell if it is a faint aurora or just the moon illuminating the Juneau Icefield behind these peaks. I was exposing for the foreground icebergs with the hope that I would get some subvisual aurora. The photo has had some slight adjustment to levels in Photoshop, but no more than I do to any other photo. There is certainly no false coloring or other trickery involved.

It is a 30 second exposure at ISO 3200 taken with a Canon 20D. I generally take a high ISO photo at a short shutter speed to check for framing before taking longer photos at lower ISOs. Photo IMG_2288.jpg on this page: http://sacredartichoke.com/coppermine/d ... m=8&pos=16

was a longer, two and a half minute exposure at ISO 200.

Again, thanks for the kind words. I've been overwhelmed with the response I've gotten today from this photo.

Lance McVay
lancemcvay@gmail.com
http://sacredartichoke.com

by **Chris Peterson** » Mon Nov 19, 2007 5:39 pm

Axel wrote:One possibility is that the photos were not taken on the stated date. They might have been taken years before. But in Alaska early on the morning of 4 October 2007, the Moon was just past its last quarter; this is consistent with its culminating sometime in the wee hours before sunrise.

Note that the EXIF header is intact in the photos. There's no good reason to doubt that they were taken on October 4, 2007.

The fixed orientation of the artifact with respect to a saturating light source in the three images where it is seen strongly suggests nothing more than lens flare.

It certainly isn't a comet. The color is wrong, the shape is wrong, and there have been no comets in recent years that looked like this.

by **Axel** » Mon Nov 19, 2007 5:38 pm

It has struck my slow mind that the APOD picture is labelled IMG_2287.jpg in McVay's gallery, whereas the darker picture is labelled IMG_2288.jpg. While it isn't 100 percent certain, chances are the lighter picture was taken before the darker one, in which case both would have been after sunset - and the Moon would definitely not be there on 4 October 2007. Whatever... McVay's photography is stunning.

Starship Asterisk*

Aurora in the Distance (APOD 19 Nov 2007)

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Expand view Topic review: Aurora in the Distance (APOD 19 Nov 2007)

Exposure

APOD 19 November AURORA

Technical possibility

Late flash (duh!)