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The Veil Nebula
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Below is an image I took recently of the Veil Nebula in the constellation Cygnus.
The Veil Nebula is the remnant of a supernova explosion dating back several thousand years and is approx. 1,400 light years away in the constellation Cygnus. A supernova is when a star of a certain size explodes at the end of it’s life, hurtling it’s remaining material into space at speeds of a tenth of the speed of light. During this explosion, the star radiates as much energy as our Sun does in 10 billion years. Although this causes a devasting effect throughout that region of the galaxy, it creates this beautiful wispy cloud throughout space.
Image was taken with SBIG ST8XME CCD camera (thermocooled to -20degC) and a TEC140mm APO refractor (oil spaced triplet lens, 140mm diameter objective, 980mm focal length).
20 x 4 min exposures were stacked and combined to create the result.One area I’m having difficulty with is in adding borders and text (brief explanation of the object) in a format which would compliment the image.
Any suggestions would be greatly appreciated.
That’s a bit stunning-
thanks for the technical info too-Borders are definitely an optional extra, in my opinion-
completely unnecessary usually-A throwback from the poster culture,
and just a bit low rent-
though as they say, your mileage may vary-What is the pixel dimension of the original?
that’s a great image, would be lovely to see it large-j
ps- Mark- can we have an Astrophotography section?
:shock: :? :shock: :!:
I don’t know what to say. Pretty bloody amazing I suppose.
I agree with Joseph – maybe we should have an Astrophotography
section, though perhaps you might be the only one posting.
Still, that would be something to look forward to…Rob.
The camera takes images at a size of 1530 x 1020 pixels.
However, by the time the images are combined and processed, I usually crop a little off.
Before uploading them on the net, I then resize them to keep them more dial-up friendly.
A smaller size also helps hide the little flaws too. ;)
Here’s a link to a larger size image if you’re interested:
http://www.astroshot.com/Deep%20Sky/slides/2007%2009%2025%20Veil%20TEC140%20large.jpgOne of the things I tried before was printing some space-related images and hanging them on a wall.
However, I was never happy with the result. It just seemed so much darker than how I was used to seeing them on the computer.
The back illumination of a computer screen certainly helps images that are predominately dark like this one.
I was hoping that the right type of border might enhance the image in some way.How about if I were to make a negative of the image.
This would create a white background with black stars and nebula set against it,
Would make the image stand out better on a wall?
http://www.astroshot.com/Deep%20Sky/slides/2007%2009%2025%20Veil%20TEC140%20large%20negative.jpg
Or does this just ruin the image? Your comments and suggestions are appreciated.BTW, no rush re making an astrophotography section.
Lets see how the traffic goes and I’m sure the lads won’t mind amending the site if the traffic warrants it.Cheers,
astroshot wrote:
The camera takes images at a size of 1530 x 1020 pixels.
What sort of camera is that?
do you have access to the raw file?
Can you substitute a camera with more resolution,
or would that be pointless?
What is the sensor size?Sorry, so many questions-
I downloaded the big one, and enlarged it to 1.05m x 0.7m at 180dpi,
and it looks great-
would look better if the original wasn’t a jpeg, I’m sure-The negative looks great too-
but an image like this one can be appreciated for its aesthetic qualities as much as the academic ones-I remember Patrick Moore mentioning this one a lot-
back in the old days, astronomers would observe, then draw, or paint, what they saw-
often adding colours- interpreting, or enhancing their representation-Maybe it can still be done-
j
jb7 wrote:
What sort of camera is that?
do you have access to the raw file?
Can you substitute a camera with more resolution,
or would that be pointless?
What is the sensor size?Sorry, so many questions-
No prob re asking questions. You might regret it though with all the techie data below. :)
The camera is specifically designed for taking images of astronomical objects (i.e. extremely faint targets) and totally unusable for daytime objects.
It needs to be hooked up to a power supply and a pc for operation and download of the data.
The camera does not have any permanent memory storage device as the PC needs to be connected for operation.
The pc controls the camera (shutter speed, no. of frames, chip temperature).
The cooler the chip, the less noise in the image. In this case, the CCD chip in the camera has a thermoelectric cooler attached to it.
I normally cool the chip down to minus 20 degrees C in order to get low noise in my images.
The chip is extremely sensitive, with a quantum efficiency (QE) of approx 85%.
QE is a measure of the percentage of light photons that hit the chip which trigger a reaction on the pixel.
As I understand, a DSLR has a QE of approx 10%, therefore, this CCD camera is about 8.5 times more sensitive but with very little noise.
The CCD chip size is 1530 x 1020 with 9 micron pixels, or in English, 13.8 x 9.2mm
The images are taken in FITS format (lossless format) but I normally convert them to 16bit TIFF for processing.
Unfortunately, as with all cameras, the larger the chip, the more expensive the camera.
I chose this one for it’s high sensitivity. http://www.sbig.com/sbwhtmls/ST8XME.htmSo, I bet you’re sorry you asked those questions now, aren’t you. :)
Not at all,
all makes perfect sense-
looks like a great sensor-Its just that I can’t justify traveling with a fridge and a pc when I want to take a picture-
(I’ve only got a mac anyway)It seems to me that once you make the image,
there’s a graphic representation stage, similar to the one we all go through here-So don’t be afraid to ask questions yourself :D
btw, there’ll be lots of different opinions concerning the borders and text thing too-
so if you really need to go there, just do it well-
personally, I’d prefer the image posted like the one above-j
jb7 wrote:
It seems to me that once you make the image,
there’s a graphic representation stage, similar to the one we all go through here-Yes, there is an image processing stage alright.
The images are taken from the camera and run through a program called Maxim DL.
This program is designed specifically for the operation of astronomical ccd cameras and can also carry out a ceetain level of processing as well.In this case, I took the 20 images and combined them into one image with the program Maxim DL.
Within this program, I run an algorithm called DDP (Digital Development Processing) on the image.
This stretches the histogram so as to try and model the conventional development of photographic emulsions.
Then the image is brought into Photoshop and the curves and levels are adjusted to try and highlight the object but keep the background dark.
Hope this helps clarify the processing stage a little.That’s astonishing. And your tech data is absolutely fascinating.
I’ve only skimmed the article about the camera, but it seems to say that
the CCD is “stationary” (I use the quotes because it’s whizzing through
space along with everything else) and that the information collected
is turned into a still image. Or have I got that wrong?PeteTheBloke wrote:
That’s astonishing. And your tech data is absolutely fascinating.
I’ve only skimmed the article about the camera, but it seems to say that
the CCD is “stationary” (I use the quotes because it’s whizzing through
space along with everything else) and that the information collected
is turned into a still image. Or have I got that wrong?Perhaps to explain a little better…
The stars rise and set each and every night. This is due to the fact that the earth is rotating.
If I take a exposure of more than a few seconds, the stars will appear to form a “trail” in the image rather than a pinpoint dot.
To get around this, I have a motorised mount which can very accurately counteract the effects of the earth’s rotation and “lock on” to a star and track it all night long across the skyIn this case, the nebula is indeed moving at extremely fast speeds.
However, due to it’s extreme distance away from us, we don’t see any movement while looking at it.
The only way to notice any movement in the nebula is to take images over several years and compare them.Hope this clarifies it a little Pete.
Thanks for that Michael. I knew stars leave a trail in a stationary camera
but I must have misunderstood the camera spec. I thought it was saying that
the camera somehow compensated for this – not with a motor drive, but with
software. I was surmising that your 4 minute exposures were a necessity as the
nebula moved past the field of view. Which leaves me with the question: why do you not
take longer exposures if you have a motor drive? Or am I being dim?PeteTheBloke wrote:
Thanks for that Michael. I knew stars leave a trail in a stationary camera
but I must have misunderstood the camera spec. I thought it was saying that
the camera somehow compensated for this – not with a motor drive, but with
software. I was surmising that your 4 minute exposures were a necessity as the
nebula moved past the field of view. Which leaves me with the question: why do you not
take longer exposures if you have a motor drive? Or am I being dim?That’s a fair enough question Pete.
It comes down to the whole issue of signal/noise relationship.
An 80min exposure would have lots of signal but also lots of noise.
This would make it difficult to process and bring out the most from the image, especially from the faintest regions in the image.
However, with many exposures combined together, the noise cancels itself out and so permits alot pf processing.
The other issue is blooming.
The standard dslr camera has a certain level of protection in it which, when the pixel is fully saturated, prevents the signal leaking or bleeding onto another. pixel If it didn’t have this protection, a bright spike would appear on the image from bright light sources. This technology reduces the efficiency of the chip by about 30%. My CCD camera does not have this feature, thereby increasing the sensitivity of the chip. However, with all pluses, there are minuses.
For more, read: http://www.ccd.com/ccd102.html
If I took really long exposures, the stars would all have artificial spikes on them.
Hope this helps explains the reasons behind the exposures.
Thanks for asking a good question though.This all makes for fascinating reading Michael, and a hell of a lot more
technical than most of us here ever have to deal with. I can’t begin to
appreciate the amount of work and effort that must go in to capturing
these sort of images. Thanks for being so detailed and informative in your
explanation of what you do. Marvellous stuff indeed…Rob.
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