Hello everyone! Tonight is a gorgeous night in my area to shoot, And I was thinking of shooting rosette nebula tonight. But! I want to try and do a multi day exposure of rosette nebula (Today and tomorrow!) Since both nights are clear. I was curious, With a DSLR That’s not cooled How can I achieve that? Since the sensor might have different temperature how can I do my calibration frames and then afterwards stack it? The reason I want to do a multi day exposure Is to pull out more of that nebulosity and reduce the banding/noise that seems to show! (My camera is a canon eos rebel t6 With a 75-300 MM Lens)
Thank you for taking the time to read :)!
Clear skies!
-Horriblebaby
How to do multi day exposures with a dslr!
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Hi,
I’ve done one multi-night imaging project with an uncooled camera.
Just take calibration frames (especially darks) separately each night, then calibrate each night’s data with its own calibration frames. After that, stack all the calibrated data together.
Clear skies!
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Hi, this sounds very familiar to me as I just shot M42 over two nights in a row using my DSLR and a 70-300mm lens.
For me, I shot calibration frames on my second night and used for both, as it was same time, roughly same temp, same place.
However, if I were to do it again, I would do two separate pairs of calibration frames for each night. That is probably the safest and correct way to do it. I was happy with my results, but this is one thing I would change to dial it in even more.
CS!
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Horriblebaby · Mar 20, 2026, 10:12 PM
Hello everyone! Tonight is a gorgeous night in my area to shoot, And I was thinking of shooting rosette nebula tonight. But! I want to try and do a multi day exposure of rosette nebula (Today and tomorrow!) Since both nights are clear. I was curious, With a DSLR That’s not cooled How can I achieve that? Since the sensor might have different temperature how can I do my calibration frames and then afterwards stack it? The reason I want to do a multi day exposure Is to pull out more of that nebulosity and reduce the banding/noise that seems to show! (My camera is a canon eos rebel t6 With a 75-300 MM Lens)
Thank you for taking the time to read :)!
Clear skies!
-Horriblebaby
Darks are never that accurate with a DSLR anyway. I would just lump all the lights together and run it with one set of calibration frames. The only place you might get into trouble is with the flats, not the darks. I’d try it that way first and if it doesn’t work then do separate stacks and combine.
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Hi, yes I have done multi-night imaging a few times with a DSLR.
Because the sensor is not cooled, once you start taking frames it will quickly heat up. How warm it gets is a function of the ambient air temperature and how long you wait between frames. During the course of the night, you might end up with frames that have been taken at a range of temperatures, as the outside temperature drops. So, matching a set of darks exactly to the lights (in terms of temperature) is hard with an uncooled sensor.
From a practical sense, unless the outside air temperature is really different between the two nights, or you dramatically change the “wait time” between frames (to allow cooling), you probably don’t need to retake the darks each night….the temperature difference isn’t large enough and your images may be at a range of temps anyway. But…is also won’t HURT to take more dark frames, it just might not gain you much.
What I do strongly recommend is dithering. That will really help with bad pixels.
Jeff
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Exactly, if you dither well you can probably do without dark frames altogether.
Jeffrey Kieft · Mar 21, 2026 at 01:43 PM
Hi, yes I have done multi-night imaging a few times with a DSLR.
Because the sensor is not cooled, once you start taking frames it will quickly heat up. How warm it gets is a function of the ambient air temperature and how long you wait between frames. During the course of the night, you might end up with frames that have been taken at a range of temperatures, as the outside temperature drops. So, matching a set of darks exactly to the lights (in terms of temperature) is hard with an uncooled sensor.
From a practical sense, unless the outside air temperature is really different between the two nights, or you dramatically change the “wait time” between frames (to allow cooling), you probably don’t need to retake the darks each night….the temperature difference isn’t large enough and your images may be at a range of temps anyway. But…is also won’t HURT to take more dark frames, it just might not gain you much.
What I do strongly recommend is dithering. That will really help with bad pixels.
Jeff
Hello! I have heard of dithering before, but what is it and how do you achieve it? Thank you so much for the help!
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Horriblebaby · Mar 21, 2026, 03:20 PM
Jeffrey Kieft · Mar 21, 2026 at 01:43 PM
Hi, yes I have done multi-night imaging a few times with a DSLR.
Because the sensor is not cooled, once you start taking frames it will quickly heat up. How warm it gets is a function of the ambient air temperature and how long you wait between frames. During the course of the night, you might end up with frames that have been taken at a range of temperatures, as the outside temperature drops. So, matching a set of darks exactly to the lights (in terms of temperature) is hard with an uncooled sensor.
From a practical sense, unless the outside air temperature is really different between the two nights, or you dramatically change the “wait time” between frames (to allow cooling), you probably don’t need to retake the darks each night….the temperature difference isn’t large enough and your images may be at a range of temps anyway. But…is also won’t HURT to take more dark frames, it just might not gain you much.
What I do strongly recommend is dithering. That will really help with bad pixels.
Jeff
Hello! I have heard of dithering before, but what is it and how do you achieve it? Thank you so much for the help!
It’s a small random offset of your frame of just a few pixels. Some will do it for every frame but most will dither every 4th frame or 8th. For me it depends on how long the subs are. It doesn’t hurt to overdo it but it does cut into total integration time. What is does is randomize the location of hot pixels and other defects so that the stacking program will then recognize them and remove them. PHD2 will do it when commanded by the controller software.
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Tony Gondola · Mar 21, 2026 at 03:33 PM
Horriblebaby · Mar 21, 2026, 03:20 PM
Jeffrey Kieft · Mar 21, 2026 at 01:43 PM
Hi, yes I have done multi-night imaging a few times with a DSLR.
Because the sensor is not cooled, once you start taking frames it will quickly heat up. How warm it gets is a function of the ambient air temperature and how long you wait between frames. During the course of the night, you might end up with frames that have been taken at a range of temperatures, as the outside temperature drops. So, matching a set of darks exactly to the lights (in terms of temperature) is hard with an uncooled sensor.
From a practical sense, unless the outside air temperature is really different between the two nights, or you dramatically change the “wait time” between frames (to allow cooling), you probably don’t need to retake the darks each night….the temperature difference isn’t large enough and your images may be at a range of temps anyway. But…is also won’t HURT to take more dark frames, it just might not gain you much.
What I do strongly recommend is dithering. That will really help with bad pixels.
Jeff
Hello! I have heard of dithering before, but what is it and how do you achieve it? Thank you so much for the help!
It’s a small random offset of your frame of just a few pixels. Some will do it for every frame but most will dither every 4th frame or 8th. For me it depends on how long the subs are. It doesn’t hurt to overdo it but it does cut into total integration time. What is does is randomize the location of hot pixels and other defects so that the stacking program will then recognize them and remove them. PHD2 will do it when commanded by the controller software.
Okay awesome! For ph2d, do I just need my mount to plug into my computer and then select a dither option in the software? Or do I need anything else.thank you!
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Tony Gondola · Mar 21, 2026, 03:33 PM
Horriblebaby · Mar 21, 2026, 03:20 PM
Jeffrey Kieft · Mar 21, 2026 at 01:43 PM
Hi, yes I have done multi-night imaging a few times with a DSLR.
Because the sensor is not cooled, once you start taking frames it will quickly heat up. How warm it gets is a function of the ambient air temperature and how long you wait between frames. During the course of the night, you might end up with frames that have been taken at a range of temperatures, as the outside temperature drops. So, matching a set of darks exactly to the lights (in terms of temperature) is hard with an uncooled sensor.
From a practical sense, unless the outside air temperature is really different between the two nights, or you dramatically change the “wait time” between frames (to allow cooling), you probably don’t need to retake the darks each night….the temperature difference isn’t large enough and your images may be at a range of temps anyway. But…is also won’t HURT to take more dark frames, it just might not gain you much.
What I do strongly recommend is dithering. That will really help with bad pixels.
Jeff
Hello! I have heard of dithering before, but what is it and how do you achieve it? Thank you so much for the help!
It’s a small random offset of your frame of just a few pixels. Some will do it for every frame but most will dither every 4th frame or 8th. For me it depends on how long the subs are. It doesn’t hurt to overdo it but it does cut into total integration time. What is does is randomize the location of hot pixels and other defects so that the stacking program will then recognize them and remove them. PHD2 will do it when commanded by the controller software.
What Tony said!
I’ll expand on that by saying that you need to be using software that controls the mount (and camera) and that is capable of dithering. It will move the mount just a tiny bit (a few pixels worth) between frames (or sets of frames) so that any bad pixels are not at exactly the same place on every frame. I have only used it with guiding, but in theory it can be done without guiding but with good tracking.
Dithering is not necessary, but is definitely something to bring into your wheelhouse as your experience and equipment capabilities grow.
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Horriblebaby · Mar 21, 2026, 03:52 PM
Tony Gondola · Mar 21, 2026 at 03:33 PM
Horriblebaby · Mar 21, 2026, 03:20 PM
Jeffrey Kieft · Mar 21, 2026 at 01:43 PM
Hi, yes I have done multi-night imaging a few times with a DSLR.
Because the sensor is not cooled, once you start taking frames it will quickly heat up. How warm it gets is a function of the ambient air temperature and how long you wait between frames. During the course of the night, you might end up with frames that have been taken at a range of temperatures, as the outside temperature drops. So, matching a set of darks exactly to the lights (in terms of temperature) is hard with an uncooled sensor.
From a practical sense, unless the outside air temperature is really different between the two nights, or you dramatically change the “wait time” between frames (to allow cooling), you probably don’t need to retake the darks each night….the temperature difference isn’t large enough and your images may be at a range of temps anyway. But…is also won’t HURT to take more dark frames, it just might not gain you much.
What I do strongly recommend is dithering. That will really help with bad pixels.
Jeff
Hello! I have heard of dithering before, but what is it and how do you achieve it? Thank you so much for the help!
It’s a small random offset of your frame of just a few pixels. Some will do it for every frame but most will dither every 4th frame or 8th. For me it depends on how long the subs are. It doesn’t hurt to overdo it but it does cut into total integration time. What is does is randomize the location of hot pixels and other defects so that the stacking program will then recognize them and remove them. PHD2 will do it when commanded by the controller software.
Okay awesome! For ph2d, do I just need my mount to plug into my computer and then select a dither option in the software? Or do I need anything else.thank you!
Basically yes. The software the runs your imaging and mount triggers (commands) PHD2 to dither.