'With grave joy we, the cosmical explorers, who were already gathered up into the communal mind of our own galaxy, now found ourselves in intimate union with a score of other galactic minds, We, or rather I, now experienced the slow drift of the galaxies much as a man feels the swing of his own limbs. From my score of viewpoints I observed the great snow-storm of many millions of galaxies, streaming and circling, and ever withdrawing farther apart from one another with the relentless "expansion" of space. But though the vastness of space was increasing in relation to the size of galaxies and stars and worlds, to me, with my composite, scattered body, space seemed no bigger than a great vaulted hall.'
- Olaf Stapledon, Star Maker
Not much inspires a sense of meaning in me these days like the sheer scope and scale and depth of creation.
If think the astrobiscuit collaboration images in these links were captured using lucky imaging, so a different process to the traditional long integration used in the M81/M82 image the OP shared. There's a video about it:
They were a combination of lucky imaging to get the very centre of the galaxies in high resolution, and traditional long integration for the rest of it. I know, because I participated.
It depends. Thing is, there's plenty to take pictures of out there that is big and dim. A camera with a decent camera lens (or even a not decent camera lens, at a push) on a tripod will get you good results, as long as you can collect light for long enough.
By far the greatest thing that improves astrophotography is the ability to collect light for a long time, and this implies tracking the movement of the stars across the sky. I'd say that this is more important than having a telescope. Without it, you're limited to taking pictures short enough that the stars don't move more than a pixel or two in that time, which is typically between a tenth of a second and ten seconds, depending on the zoom level of your lens. However, you can take multiple pictures and combine them. With a tracker, you can easily take exposures that are minutes long.
Lucky imaging is useful for things that are very bright, and it allows you to sharpen up the image. It works for the moon, and the brightest parts of some galaxies or nebulae. But the normal things that make spectacular astrophotography images aren't really helped by it. Mostly, the best thing to make images better is just to collect more light. Lucky imaging is great, but it's a niche.
I never understood why you need tracking, so long as the object you're shooting remains within the usable field of view (more noise towards the edges, at least on my phone) of the camera sensor. Why not apply the tracking afterwards in software? A lot easier to write code once that moves pixels around than to produce hardware that moves accurately in imperceptibly small steps for everyone who wants to do this. I assume there's a good reason why that doesn't work, do you know it?
If you're using a telescope, say with a modest focal length of 1000mm, then if it is held still on a tripod, then the stars will move across the field of view at a rate of a few pixels per second (depending on the exact sensor, and what part of the sky you're pointing at). Therefore, each individual picture will need to be less than a second in duration, before stacking in software.
It does work. I have produced acceptable images of the Andromeda galaxy by using a 150-600mm lens at 150mm on a tripod taking 1.3s exposures. I took 1151 images, which is a total of 24 minutes of light collection, and the image was rather mediocre.
I then make a rudimentary tracker, and took 22 exposures of 6s each, at 600mm, and the results were way better. At 600mm, I would have had to take 0.3s exposures untracked, and it would have been awful. I then bought a proper tracker, and did 254 exposures of 30s each at 600mm, and the result was just so much better.
The problem is that a lot of the pretty stuff we can make pictures of is very dim, so the main thing driving image quality (assuming the optics are OK) is the noise level of those dark pixels.
There are several reasons why it is better to have a physical tracker. One is that the noise from the sensor consists of shot/Poisson noise (from the photons coming in), dark current, and readout noise. If you have very short exposures, then the readout noise dominates. The shot noise is a physical limit - you can't get lower noise than the shot noise for the number of photons that you collect; you can only improve that by collecting more photons. The readout noise is entirely added by the equipment, and you can minimise that by taking longer exposures. The dark current is improved by cooling the sensor down. Other reasons are the data quantity (if you're processing it later or keeping the raw data, as most astrophotographers do), processing time, and wear on the shutter mechanism (if it is mechanical). Also, if you have a reasonably long telescope, if you don't have a tracker then the subject will keep moving out of the frame in less time than you would expect, and you'll have to keep re-pointing the telescope anyway.
Lucky imaging is the opposite - then you do deliberately want to take lots of short exposures to get sharper images, but the trade-off is that the noise is higher, and you really want to have a sensor with an electronic shutter. Short exposures are only suitable when there is something in the frame that is bright enough to register as a reasonably bright few pixels, otherwise there is nothing to align the frames with, and lucky imaging can't work out how sharp each frame is.
Really cool. I cannot tell which images are accurate color and if some are false color. I don't know enough about space photography to spot it without labeling. One caption of one image seems to indicate there is some false color (the one that says HI=Blue(false color)?). Are the rest of the images fairly color-accurate? Or are all of the images color-enhanced somehow, too?
I love images from astronomy, but I wish it was generally made clearer when color enhancement is and is not used.
Deep sky astrophotography rely on very long exposure and motorized tripod in order to take into account the Earth rotation. You can probably put your instrument on a balloon (... can you ? telescopes are heavy and voluminous !), but then you'll need to track the position of the balloon so that the instrument can still point in the right direction. Wind is chaotic, so it's probably a nightmare to compensate.
> To achieve high-precision measurements from a balloon-borne environment, the SuperBIT gondola – at roughly 3500 lbs – stabilizes its telescope to sub-arcsecond precision (akin to a three degree-of-freedom Steadicam) while sophisticated optics further stabilize the SuperBIT camera to < 50 milliarcseconds.
- Olaf Stapledon, Star Maker
Not much inspires a sense of meaning in me these days like the sheer scope and scale and depth of creation.
Beautiful work.