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Edit:  Sorry if this should be in the Getting Started Equipment Help and Advice section. Please feel free to move this if required.
 

I have recently brought a Canon 550D (with 24k shutter count) to learn and master astro timelapse. After reviewing a test run I noticed there are lots of stuck pixels against the rotating night sky.
I then did a black exposure with the cap on, and the shot came up with even more hot pixels than I was mentally prepared for. My wife has a 1000D and it is nowhere as bad. 

Uploaded a Jpeg if anyone wants to see, or attached a CR2 file if anyone wants to have a play. This is a 30 sec exposure on ISO 1600, the standard setting I predict to use in the field
niOIPtV.jpg

I have done both air blowing and manual sensor clean but the pixels are still exactly where they are. I read up they can be removed in post processing but the thing is, how much is too much ? 
Should I be concerned about this and have it returned or is this to be expected and should be embraced? 

Thanks for reading in advance


And for those who are curious about the practice timelapse....

giphy.gif
11mm (APS-C), 201 frames, 25s exposures, ISO 800 , f/2.8, Bortle 5-6, Adobe Lightroom

 

IMG_4792.CR2

Edited by Panda Alvin
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My Canon has a "long exposure noise reduction" function that can be on / auto / off.

It's in the menu "C.Fn II: image"

Check for it in the manual of your 550D. In the setting auto, when you expose for more than one second, the camera takes an additional exposure of equal length with the shutter closed, right  after the first, normal shot. It then subtracts the second (dark) exposure from the first, to remove the hot pixels.

The time lapse looks wonderful.

Edited by Ruud
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24 minutes ago, Ruud said:

when you expose for more than one second, the camera takes an additional exposure of equal length with the shutter closed, right  after the first, normal shot.

Thanks, and yep I see the function which is off at the moment.

If I do turn it on and want to keep the same movement rate, would you know if I should ramp the ISO to 3200 and exposure to 12s? Or would the noise to signal ratio increase too much and not worth it? 

Edited by Panda Alvin

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18 minutes ago, Alien 13 said:

try the method mentioned here.

Yup, done that several times before hand but no luck with it. 🤔 Not sure if I did something wrong or the function isnt working / broken for me.

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The plastic lens cap that comes with these cameras is not particularly light-proof, so might be producing spurious extra hot-pixels.

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6 hours ago, Panda Alvin said:

Yup, done that several times before hand but no luck with it. 🤔 Not sure if I did something wrong or the function isnt working / broken for me.

The remapping in sensor clean will not work with camera jpegs you must use RAW, if your not doing so.

RAW converters can use the updated sensor map included in the file to clean the image.
You must do the clean routine after the camera has reached temperature equilibrium .

BTW most sensors will have loads of hot, dead and stuck pixels, not unusual.

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Hot Pixels can be removed in processing. APP has Bad Pixel mapping to remove them. You definitely should not turn on long exposure noise reduction if you are going to be doing any DSO imaging.

Peter

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I have a couple of CCD full frame chips which look like snowstorms - honestly orders of magnitude worse then yours - but the data comes out free of them. I stack in AstroArt and apply their hot pixel filter. It works.

Olly

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Thanks the suggestions so far, I have tested my camera and looked through some AP software just now and this is what I have discovered. 

The stuck pixels are still in the same brightness and location in a dark room. I always take pictures on both RAW and JPEG, but always use RAW as much as I can / whenever possible.
I know dark frames can be applied on DSS photos Stacking and in Startrails (cumulatively), but is there a software out there that applies dark on a frame by frame basis (and en masse) to go in timelapse? I have not come across Astro Pixel Processor or AstroArt before, so I have no knowledge if they could help on this situation.

Sorry I am still very new to all these software myself and may have missed some functionality here and there. I've just learnt Adobe Lightroom automatically removes 1 pixels stuck pixels so the ones I see must be bigger than that.
Anyhow, I think I will hold on to the camera and explore ways to improve on what I have instead.

Edited by Panda Alvin

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Oh I also forgot to mention that I did the test on the Canon long exposure noise reduction mode, it does remove the very visible stuck pixels leaving only the less visible... well noise in the image. Only concern is that if I did this in the timelapse, the sequence might get less smooth ?

Edited by Panda Alvin

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28 minutes ago, Panda Alvin said:

 is there a software out there that applies dark on a frame by frame basis (and en masse) to go in timelapse?

That's what in-camera dark subtraction does. There are two problems with it - it doubles the time required and it can erroneously remove small stars (if it is combined with other noise removal techniques).

The hot pixels don't move, so stacked darks will remove all of them.

People say temperature changes make darks for DSLRs unreliable. I made sets of darks for warm, cool and cold evenings and found that using the right set worked really well. You don't nee a new set of darks for each session, or even for when you change equipment.

Taking bias frames (really short exposures) will also help.

Ideally you also want flats (which make a big improvement by getting rid of vignetting and dust effects.).

 

 

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Sharpcap can do dark & flat subtraction to each frame as you go along, but timelapse requirements are slightly different. @rwg wrote the program and would be able to advise if it would suit.

Edited by Demonperformer
autoincorrect!

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Astro Pixel Processor is good at removing bad pixels. See here

Peter

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