What did you see in the sky tonight?

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Century of the Fruitbat

Post by Nitpicker » Mon Dec 16, 2013 12:31 am

Around this time of year at dusk, we see huge colonies of fruit bats as they make their daily passage of up to 50km from their day roosts, to their evening feeding grounds. Literally thousands of bats pass overhead for about a hour after sunset. A few of them stop for a break in my Golden palm trees, and a few others visit throughout the night. I try to discourage the bats by trimming the fruits and nuts off the palms. As amazing a spectacle as these bats are, they need to be treated with caution. A decade or so ago, it was discovered that about 30% of these bats are reservoirs for a lyssavirus variant, similar to rabies. Only a very small number of people have died from this variant. A larger number (a few hundred I think) who have been scratched or bitten by infected bats, have survived after being treated, post exposure, with the rabies vaccine and immunoglobulin (which I understand is quite a painful procedure in itself).

See:
http://en.wikipedia.org/wiki/Australian_bat_lyssavirus

...

I find it quite difficult to photograph these bats well, as they are fast moving targets in quickly diminishing light. But here is one photo I was reasonably happy with. It shows a few bats flying past the top of my Alexander palms, whilst the Moon pokes its eastern limb through an emerging thunderstorm (about four hours before the Chang'e 3 landed):
moon_bats.jpg
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Re: What did you see in the sky tonight?

Post by Nitpicker » Mon Dec 16, 2013 1:43 am

In honour of Chang'e 3's landing, I recorded some HD video of the Bay of Rainbows with my little 6 inch scope operating at about f/60. The night before the landing, I enjoyed quite good seeing conditions, and the terminator was closer to the landing site (near 9km diameter crater Laplace A, near centre of frame). However, on the next night, Dec 14, just as the craft was about to land, my sky was still suffering the effects of a recent thunderstorm and was about as wobbly as I've ever seen it. So, I thought I'd show these two images (nothing more than simple, cropped screen grabs from the videos taken on successive nights) as a comparison of different atmospheric seeing conditions:
dec13.JPG
dec14.JPG
(And yes, I need to clean a few specks off the sensor on my camera!)
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Re: What did you see in the sky tonight?

Post by Chris Peterson » Mon Dec 16, 2013 2:02 am

Nitpicker wrote:In honour of Chang'e 3's landing, I recorded some HD video of the Bay of Rainbows with my little 6 inch scope operating at about f/60.
You could stack a few hundred frames. That should provide dramatically higher resolution.
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Re: What did you see in the sky tonight?

Post by Nitpicker » Mon Dec 16, 2013 2:21 am

Chris Peterson wrote:
Nitpicker wrote:In honour of Chang'e 3's landing, I recorded some HD video of the Bay of Rainbows with my little 6 inch scope operating at about f/60.
You could stack a few hundred frames. That should provide dramatically higher resolution.
Yep, as soon as I figure out how to do it well. Thus far I've tried stacking similar videos of Jupiter and Saturn with Registax and yielded nothing better than any single frame (or maybe I've just contracted ABLV). I think it will work better on these Moon videos. Cheers.

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Re: What did you see in the sky tonight?

Post by geckzilla » Mon Dec 16, 2013 2:41 am

It's just hard to learn new things when you are constantly interrupted by random aggressive wildlife.
Just call me "geck" because "zilla" is like a last name.

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Re: What did you see in the sky tonight?

Post by Nitpicker » Mon Dec 16, 2013 2:45 am

geckzilla wrote:It's just hard to learn new things when you are constantly interrupted by random aggressive wildlife.
And I haven't even mentioned my neighbours! :ssmile:

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Re: What did you see in the sky tonight?

Post by Nitpicker » Mon Dec 16, 2013 11:40 am

Chris Peterson wrote:
Nitpicker wrote:In honour of Chang'e 3's landing, I recorded some HD video of the Bay of Rainbows with my little 6 inch scope operating at about f/60.
You could stack a few hundred frames. That should provide dramatically higher resolution.
Okay Chris, I'm sold. A couple of hours of playing around with Registax with my two short HD videos of Sinus Iridum (10-15 seconds each @ 25 fps) has yielded much better results. I still don't know what I'm doing with Registax, exactly, nor do I feel I am a good judge of good or bad when it comes to different image processes. My gut feel is that I have overcooked the processing here, to the point where it is starting to look like a painting. But I have to admit the final images I've come up with are a lot better than my simple screen grabs. Here is what I've come up with, closer to the full HD frame of the original videos:
Sinus_Iridum_20131213_2115+10_stacked.jpg
Sinus_Iridum_20131214_2310+10_stacked.jpg
(Of course, there's still no substitute for good seeing conditions.)

...

Hmmm, now I'm going to have to revisit a whole bunch of other videos I've been quietly recording and hoarding on my hard drives for the last year. With luck, the wet season will come early here, to give me time to work on them. :ssmile:
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Re: What did you see in the sky tonight?

Post by BDanielMayfield » Mon Dec 16, 2013 1:07 pm

No clouds this morning, but the clouds last night must have been helping me somewhat, blocking moonlight. I couldn't find any part of Comet Lovejoy. It's getting lower each night toward the light polluted horizon, and it's moving away from the sun so it's dimmer each night too, so tonight's no show made me happy that had caught a few looks at it yesterday. Also no meteors, but I did enjoy a nice view of Jupiter and its four large moons and a bueatiful orange setting Moon.

No coyotes, but I did hear a great horned owl.

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Re: What did you see in the sky tonight?

Post by geckzilla » Mon Dec 16, 2013 1:53 pm

It does look more detailed and smoother, Nitpicker. Is there an adjustment for sharpness or deconvolution? That's way too high if so.
Just call me "geck" because "zilla" is like a last name.

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Re: What did you see in the sky tonight?

Post by stephen63 » Mon Dec 16, 2013 2:19 pm

Nitpicker, here is a nice tutorial for using registax. It's written for Ver 4, and mono processing but the workflow is the same for color.
http://paulhaese.net/planetaryprocessing.html

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Re: What did you see in the sky tonight?

Post by Chris Peterson » Mon Dec 16, 2013 2:29 pm

Nitpicker wrote:Okay Chris, I'm sold. A couple of hours of playing around with Registax with my two short HD videos of Sinus Iridum (10-15 seconds each @ 25 fps) has yielded much better results. I still don't know what I'm doing with Registax, exactly, nor do I feel I am a good judge of good or bad when it comes to different image processes. My gut feel is that I have overcooked the processing here, to the point where it is starting to look like a painting.
Yes, Registax has a crazy number of processing options. Figuring them all out can be a bit daunting. I tend to steer away from its sharpening tools and just use it for bad image rejection (with my seeing here, I usually reject about 90% of the frames), alignment, and stacking. But that's not to say there's anything wrong with the Registax post processing tools.
(Of course, there's still no substitute for good seeing conditions.)
To a degree. But even sites with bad seeing usually have moments of very good, so if you have enough video frames, and your object isn't changing (Jupiter rotates so quickly that getting enough frames under poor seeing can be impossible), you can achieve the same results under poor seeing as you might under much better. Lucky imaging is a great technique to apply to bright targets.
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Re: What did you see in the sky tonight?

Post by Chris Peterson » Mon Dec 16, 2013 2:36 pm

geckzilla wrote:It does look more detailed and smoother, Nitpicker. Is there an adjustment for sharpness or deconvolution? That's way too high if so.
To be fair, we should distinguish between images with scientific intent and images with aesthetic intent. In the case of the former, it is frequently worthwhile to use wavelet processing or some other sharpening to enhance real detail, at the expense of creating (often) unaesthetic artifacts.

A technique I use very often is to create a highly sharpened image and composite it with the original, using Photoshop's layer blending (Lighter and Darker) and layer transparency. That often allows for bringing out edge detail without the edge artifacts that most sharpening algorithms produce.
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Re: What did you see in the sky tonight?

Post by geckzilla » Mon Dec 16, 2013 2:42 pm

Sure, sharpening is great. But this is a good example of too much. Halo artifact.
nitpickermoon.jpg
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Re: What did you see in the sky tonight?

Post by Chris Peterson » Mon Dec 16, 2013 2:53 pm

geckzilla wrote:Sure, sharpening is great. But this is a good example of too much. Halo artifact.
nitpickermoon.jpg
That is only too much sharpening if your intent is aesthetic. If your intent is to identify subtle structure, however, it could use quite a bit more sharpening.
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Re: What did you see in the sky tonight?

Post by geckzilla » Mon Dec 16, 2013 2:59 pm

Maybe elsewhere in the image, but not where there is already too much sharpening. The dark rim around the base of the crater is a fake feature. I mask areas of already high contrast off when I process.
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Re: What did you see in the sky tonight?

Post by stephen63 » Mon Dec 16, 2013 3:06 pm

Chris, when you say sharpening, are you referring to wavelet function or some sort of sharpening in Photoshop?

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Re: What did you see in the sky tonight?

Post by Chris Peterson » Mon Dec 16, 2013 3:06 pm

geckzilla wrote:Maybe elsewhere in the image, but not where there is already too much sharpening. The dark rim around the base of the crater is a fake feature. I mask areas of already high contrast off when I process.
I disagree. Even this area could use more sharpening. The thing with sharpening for scientific intent is that you need to understand the sort of artifacts that different techniques produce. You clearly understand what some of those look like, and have identified them. That means you aren't mistaking an artifact for an actual structure. If you were trying to understand the geology (selenology?) of this area, you would be well advised to apply more sharpening, and different sorts (deconvolution, wavelets with different frequencies, etc), since this will bring out specific kinds of detail and also produce different kinds of artifacts. By careful examination, a skilled observer can separate these things and learn a lot more.

You should see some of the massively oversharpened images of nebulas that appear in the literature. Ugly as sin, but critical to understanding things like shock front geometry.
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Re: What did you see in the sky tonight?

Post by Chris Peterson » Mon Dec 16, 2013 3:08 pm

stephen63 wrote:Chris, when you say sharpening, are you referring to wavelet function or some sort of sharpening in Photoshop?
I'm using the term to refer to any sharpening function, which could include deconvolution, manipulation in frequency space, unsharp masking, wavelet processing- anything at all.
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Re: What did you see in the sky tonight?

Post by stephen63 » Mon Dec 16, 2013 3:27 pm

In the case of processing for aesthetic images, there really is no set rule of thumb for the amount of sharpening or anything else. What I mean by this is that how you manipulate an image depends a LOT on what object you are processing. I'm sure it's no one's goal to overcook an image, but that's what happens when too much sharpening/color enhancement is used.

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Re: What did you see in the sky tonight?

Post by geckzilla » Mon Dec 16, 2013 3:29 pm

Alright, I confess I have no idea what scientific sharpening is. I always figured you'd want to avoid introducing fake details, aesthetic or for science.
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Re: What did you see in the sky tonight?

Post by Chris Peterson » Mon Dec 16, 2013 3:32 pm

geckzilla wrote:Alright, I confess I have no idea what scientific sharpening is. I always figured you'd want to avoid introducing fake details, aesthetic or for science.
All processing can add artifacts. When you're evaluating an image for scientific purposes, the goal is to distinguish what is an artifact from what is real, not necessarily to prevent artifacts, which you can't always do and still achieve the processing goals.
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Re: What did you see in the sky tonight?

Post by Ann » Mon Dec 16, 2013 5:24 pm

This time of year, the skies over southernmost Sweden are either murky and foggy or clear and bitingly cold. The weather here has been mild, so our skies have been relentlessly overcast. But yesterday I saw Venus (yay!) and the Summer Triangle. I could see that Vega looked very subtly blue and that Altair looked white with no hint of blue whatsoever. Deneb looked so-so, maybe just a little blue and maybe not at all.

When I got up extremely early in the morning, fog was in process of conquering the sky. The full Moon shone brightly, surrounded by a huge halo. I saw the Winter Triangle too, and I could just barely make out Rigel. An hour later, even the Moon had been swallowed by the thick, dense fog.

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Re: What did you see in the sky tonight?

Post by Nitpicker » Mon Dec 16, 2013 11:10 pm

Thanks for everyone's feedback. It is very much appreciated. I have a lot of big new words to learn when it comes to image processing. It is the part of astrophotography that is most mysterious and unintuitive to me. At the moment, many of your comments still sound to me like you're all from another planet. I will have a good read of that tutorial from Paul Haese -- thanks muchly. To date, I've only watched a couple of pedestrian YouTube demos on Registax, which offer nothing more than exercises in button clicking. I suppose I'll have to install a copy of Photoshop or Gimp at some stage too.

Despite my lack of understanding at this early stage, it feels like I've just taken ownership of a new camera.

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Re: What did you see in the sky tonight?

Post by geckzilla » Mon Dec 16, 2013 11:14 pm

If you need any help with Photoshop, let me know. I was thinking about doing some tutorials but ehhh that's a lot of work! I will continue to think about it. :D
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Re: What did you see in the sky tonight?

Post by Nitpicker » Tue Dec 17, 2013 2:59 am

Ann wrote:This time of year, the skies over southernmost Sweden are either murky and foggy or clear and bitingly cold. The weather here has been mild, so our skies have been relentlessly overcast. But yesterday I saw Venus (yay!) and the Summer Triangle. I could see that Vega looked very subtly blue and that Altair looked white with no hint of blue whatsoever. Deneb looked so-so, maybe just a little blue and maybe not at all.

When I got up extremely early in the morning, fog was in process of conquering the sky. The full Moon shone brightly, surrounded by a huge halo. I saw the Winter Triangle too, and I could just barely make out Rigel. An hour later, even the Moon had been swallowed by the thick, dense fog.

Ann

Very confusing this Summer/Winter business. I've been watching our Summer Triangle within our Summer Circle here, quite different from your Summer Triangle, which I can't see at all at this time of year. :-?