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So, 24 Megapixels is starting to get annyoing


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My Nikon D600 is a superb camera for normal photography, which is another of my hobbies that I enjoy a lot, but for AP I'm starting to wish for something else.

It creates huge files. Processing is not so bad, I have a good computer, but one session can be 50GB of data and I have to throw away stuff. So far I have a lot of sessions that were failures, Rubbish focus, over exposed stuff etc, but soon I will need to start throwing away stuff I want to save.

I have just ordered my scope so I need to save a bit first but then I am getting a CCD.

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I can't see the point of keeping sessions that are not worthwhile. You can keep the raw files as a reminder of what not to do in future. Then you can always recreate the stacked images if need be, though I doubt there is much reason to do so if you have already deemed them to be bad.

Personally I'd just delete them, you wouldn't save out of focus/heads chopped off "daytime" photos would you?

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A high megapixel sensor is what you DON'T WANT for AP. The smaller pixels mean less sensitivity and the increased data means more time downloading and wasting valuable imaging time. Also, the increased data means longer processing times - stacking takes much longer and post-processing takes much longer. The image resolution is generally limited by the optics and the seeing rather than by the sensor once you get above a certain point. I think I've seen it said that something like 8MPx is the most you want in an APS-C size sensor. In particular you don't want less than 5 micron pixels - any less and the sensitivity is severely affected. In fact 6 or 7 microns is better.

Edited by Gina
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A high megapixel sensor is what you DON'T WANT for AP. The smaller pixels mean less sensitivity ......

In fairness, the pixel size on the Nikon D600 is 5.95µm, which is actually bigger than, say, the Canon 1000d or other Canons at 5.7µm. So, high megapixels doesn't necessarily mean smaller pixels. True, it's not a CCD, but as DSLRs go, it's probably not all that bad.

Edited by lukebl
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You could always do 2x2, 3x3 etc binning on your images before you start to process them. Apart ftom giving you much smaller images it would have the advantage of noise reduction.

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I doubt that it is worth trying to resolve below about 2 arcseconds per pixel. If your pixels take you below that you are likely to lose signal and, with it, real image resolution. Not until you have a really strong S/N ratio do you get to produce in a picture the optical resolution of which your setup is capable.

Our new camera has big 9 micron pixels and a lot of them because it has a huge chip. Great in a way but, boy, a big chip does bring a few big problems in tow!!

Olly

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Is binning something that my camera needs to do when taking the actual exposure or can you do this in post processing? What software do you use to bin the images? I know Pixinsight has the IntegerResample process tool but thats one image at a time.

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As I understand it, binning won't work with colour cameras. It's no good combining different colour pixels unless you want a greyscale image.

Edited by Gina
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The ATIK 383L (8300 sensor) is 5.45um with a 17MB image. Once you add LRGB you're looking at a large image. I think the largest image I have after processing is 6GB and the reality is at least an i7 with 16GB of RAM and an SSD to carry the current project is the best bet for processing.

Are you using 64 bit images during processing?

Edited by NickK
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Storage is cheap and getting cheaper. Flash drives are where the premium buyers are these days (both in desktop and server/storage arrays), and so spinning rust is getting ridiculously cheap.

I built my main PC (for gaming, turns out it is also good for image processing) back in early 2009 when the original Core i7 came out. Bought a 67GB SATA drive and it was well over 200 quid (mind you was a 10K RPM so not surprising). A couple of years later I ran out of space so I added a 200GB SATA for about £150 (7.5K RPM so not much cheaper really). Two weeks ago I was nearly out of space again, so I added a 2TB SATA for £67 (again 7.5K RPM). Could've bought a bigger disk but don't think I'll need the extra space ;) Prices have dropped off a cliff for non-flash storage.

As for deleting images, I have every single digital image I have ever taken since 1998 (astro or not) on hard disk somewhere; have even backed some of it up :) That including all of the failures and most of my astro-processing intermediate files. I'd rather spend my time on doing something more productive than sorting through a bunch of images dating back fifteen years, or even sorting through today's captures to delete the bad ones.

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Could've bought a bigger disk but don't think I'll need the extra space ;)

I wonder how many times that's been said over the years.

If their is one thing that has totally and continuously been under estimated from the word go and that's just how much memory/disk usage/capacity increases as the years tick by.

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Just be glad you're not into film-making where a 50 GB file is chicken feed. The Blackmagic cam I have on order runs at 125 MB per sec, shooting 5 MB raw frames :eek:

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I'd quite like a 'scope that would cover the frame of my old 5D with its big fat pixels. Unfortunately such a 'scope would be well out of my budget.

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Its often said on here bigger pixels are better but just one question

is it better to use a new Canon/Nikon/what ever with approx 20Mp or is it better to get a second hand Canon/Nikon/what ever from a few years back but only being say10Mp or less?

ie same make, same size sensor, older technology but fewer pixels

this is assuming one can't afford a CCD based set up yet and is either using s/h gear or doubling up using your primary latest and greatest photography camera

My assumption is that there is a compromise ?

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Its often said on here bigger pixels are better but just one question

is it better to use a new Canon/Nikon/what ever with approx 20Mp or is it better to get a second hand Canon/Nikon/what ever from a few years back but only being say10Mp or less?

ie same make, same size sensor, older technology but fewer pixels

this is assuming one can't afford a CCD based set up yet and is either using s/h gear or doubling up using your primary latest and greatest photography camera

My assumption is that there is a compromise ?

Trouble is, if you go for older models other things aren't as good. Best IMO is to go for the bottom end of the current range - get the advancements but not the higher megapixels or the bells and whistles that aren't wanted for AP anyway. Hence why I went for the 1100D - lowish megapixels but the latest image processor.
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