M6 / M5 Astrophotography

Marco Nero said:

ScottPeach said:

This is the first time I’ve ever commented on a review. I just had to let you know how useful this is to me. After a lot of searching I finally know why lens I need!! Thank you!!

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Which lens have you decided to go with? My personal preference for Milky Way shots is the EF-M 22mm f/2 STM lens at present (for the EOS M cameras).

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Yet another poster here on this old thread.

Beautiful pictures which you posted earlier, and some very useful information.

I know you like the EF-M 22mm f/2 lens but I'm considering the Sigma EF-M 16mm f/1.4 lens as it has a wider FoV and aperture, or possibly looking for a fast & wide EF lens. I was already considering it, but after reading your post I'm even more convinced that I need a lens like that for better results at night.

I've been shooting some shots with my EF-M 11-22mm and have been pleased with the results but yes, sensor noise is an issue. I like the wide angle though for shooting the skies.

Tim van der Leeuw said:

Marco Nero said:

ScottPeach said:

This is the first time I’ve ever commented on a review. I just had to let you know how useful this is to me. After a lot of searching I finally know why lens I need!! Thank you!!

Click to expand...

Which lens have you decided to go with? My personal preference for Milky Way shots is the EF-M 22mm f/2 STM lens at present (for the EOS M cameras).

Click to expand...

Yet another poster here on this old thread.
Beautiful pictures which you posted earlier, and some very useful information.

I know you like the EF-M 22mm f/2 lens but I'm considering the Sigma EF-M 16mm f/1.4 lens as it has a wider FoV and aperture, or possibly looking for a fast & wide EF lens. I was already considering it, but after reading your post I'm even more convinced that I need a lens like that for better results at night.

Click to expand...

The Sigma AF 16mm f/1.4 DC DN (C) - EOS M-mount lens is a lens I've written about before... it's a wide, bright lens but it's 3 (or 4 ?) times more expensive than the EF-M 22mm f/2 STM lens (depending where you are in the world) . It's a better choice if you want an even wider view of the Milky Way. But beware of Sigma and their inability to guarantee compatibility with future Canon bodies. To quote myself from July 2019: "For Astrophotographers: the Rokinon 12mm lens (yes, I know this isn't the 16mm version) offers more contrast and an ability to expose for up to 7 seconds longer (than the Sigma 16mm f/1.4) when comparing to the two lenses. The Sigma produces some very prominent coma (as predicted) in the sides and corners.". This means you'll need to stop down the lens considerably for astrophotography to reduce the coma. I don't know by how much, but lenses like Canon's EF 24mm f/1.4L II USM require something closer to f/2.8 to eliminate the coma. The Sigma AF 16mm f/1.4 shares several of the design aspects of the Canon EF 24mmL lens (which isn't much of a surprise considering Sigma likely reverse-engineered the Canon EF lens) so I'd guess the coma limitation is probably close to the same. Just be aware of these aspects before making your purchase because this lens is similar in cost to the Canon EF-M 32mm f/1.4 lens... which is probably too narrow for most people wanting to do astro-landscapes. Right now, for EF-M lenses, the best choice for astro are the manual lenses from Samyang/Rokinon. They have be best coma control and come in several wide FOV options.

Tim van der Leeuw said:

I've been shooting some shots with my EF-M 11-22mm and have been pleased with the results but yes, sensor noise is an issue. I like the wide angle though for shooting the skies.

Click to expand...

All lenses can capture the Milky Way in a matter of seconds... if the sensor is large enough - but f/4 lenses are a bad choice. This is because the narrow aperture and high contrast of this lens will result in a need for much longer exposures using higher ISO settings. The combined result is a lot of grain and sensor noise as well as banding. The EF-M 11-22mm f/4-5.6 lens might do well on a sky-tracking EQ mount for telescopes but it will produce inferior results on the EOS M series cameras if only a tripod is used. The lens produces marginally "better" results on a more recent model camera like the M6 but it's still grainy. I've rated it as the least impressive native EF-M lens for astro.
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I recently moved to the EOS R system (Specifically the EOS Ra) for Astrophotography and won't likely shoot as much Astro with the EOS M cameras/lenses from this point forward. The difference in ability from the EOS Ra has made my EOS M6 and EOS 6D DSLR virtually redundant.

--
Regards,
Marco Nero.

Thanks a lot for your advice, Marco!
Certainly some things to consider.

Tim van der Leeuw said:

Thanks a lot for your advice, Marco!
Certainly some things to consider.

Click to expand...

Just take onboard any information you can obtain on the lenses that interest you. Some coma is to be expected but there are some wide, bright lenses that handle it well. There are professional photographers who ignore coma completely (including National Geographic photographers capturing astro-landscapes) and with regular photography it forms part of the "lens character" ...but with Astrophotography it is less desirable. There's quite a few astro-capable lenses to choose from in most camera series and most brands.
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Don't be afraid to experiment with different lenses that you think might possess the right values. And feel free to violate the so-called "rules" on processing and even apertures, ISO and especially exposure times. Sometimes, shooting with higher than preferred ISO can result in more detail being captured. Violating the "rule of 400/500/600" for exposure times can still yield better results with more light with minimal star trails. This is especially true when dealing with an astro-landscape where the background is defocused - but fudging the numbers can occasionally produce great results. If you have a personal use for a lens that might produce excellent terrestrial photography but might generate some coma etc, don't let that stop you from buying the lens. For this reason, the Sigma EF-M 16mm f/1.4 lens may still be a very useful lens to you. Stopping the lens down just slightly, and then correcting any residual coma later, might be the answer for you.

Wow, what an interesting discussion if you are into this sort of thing. A lot of useful and practical info, thanks to all those who contributed! I can add a little here too.

I too have gotten 'back' into astrophotography this year after a several-decades absence. I used to be an astronomer for a small science center near Hartford CT and did extensive astrophotography way back with Canon F1 and T70 film cameras, processing in a darkroom etc.

This year it started with my 'ancient' first-generation digital Canon T1i DSLR getting comet Neowise, then I upgraded to a D70, then to an M6, and finally on Black Friday open box deal to an M6 Mark II! Each upgrade jumped a generation or two in resolution and better high ISO performance.

I am blown away by what these digital cameras can do today. In 5 minutes outside plus another 15 at the computer I can get images unimaginable in the film camera days.

I have not shot Milky Way shots yet (I don't really have dark skies where I am). I got a vintage Minolta MC Celtic 135mm f2.8 lens, which turns out to be as sharp as decent modern lenses, and a Fotasy Minolta MD->EOSM adapter for $11, to get the brighter deep sky objects like the Orion Nebula, M31 and M32 in Andromeda, etc.

With that lens you can do about 1 - 1.3 second exposures without tracking. I use DeepSkyTracker free stacking software when I want to get lower noise and much fainter detail, for deep sky objects, and Registax for planetary photography. For the Moon and planets I got a Meade ETX90 off Craigs list for $100, which turns out to be a killer sharp and contrasty telescope for its size. Luckily mine came with the prime focus camera adapter, and I had a Canon EF T-ring.

I also got a MInolta vintage MC Rokkor 28mm f2.8 and MC Rokkor-X 50mm f1.4 as prime lenses for both daytime photos and constellation-type astrophotos. For daytime photos all of them are sharper and clearer around f5.6 - f8 than the 15-45mm EF-M kit lens that came with the M6 and M6 Mk ii. The 50mm f1.4 adds funny foggy shapes around the very brightest stars and is a bit soft at f1.4, becoming really good at f2. The 28mm and 135mm perform very well wide open at f2.8. I paid about $20 for each lens off a Craigs list deal.

Amazingly the Canon M6 Mark II with a 135mm f2.8 lens will actually show you the Orion Nebula and M31 galaxy in Andromeda in live view! You can even take a 4k video of them.

I've found using the EVF to be better for viewing, and especially for critical focusing, than the rear LED screen, for deep sky work, using the rear LED more to locate and frame objects at prime focus (except for critical focus where I still prefer the EVF) .

For deep sky work be sure to set the "Simulate Exposure" menu setting to "Disable" - when the frame is dark the camera will automatically bring up the gain and show the faintest stars and deep sky objects. it's a bit startling in the M6 Mk ii to actually see so many stars in the EVF winking on and off when sharp focus is attained. On a telescope, for the Moon, having Simulate Exposure 'enabled' helps you quickly see what the correct exposure will be. it's tricky to guess the exposures of the Moon at different phases and with different magnifications (with or without teleconverters, for example). I set the camera in full Manual mode and set the shutter speed (for the moon this will be between 1/15 s all the way up to 1/500 depending on the config).

For the M6 Mk II I set the shutter for "Electronic" mode to remove any vibration from the shutter opening or closing, I use the Canon remote control phone app with Bluetooth paired to release the shutter for both the M6 and M6 Mk II, so there is no vibration from the camera or user.

I found the increased resolution and better low-light sensitivity of the M6 Mark II is definitely an improvement from the already excellent M6, if you can spring for the much more expensive Mk II. The M6 Mk II also includes a stills intervalometer which the M6 did not have (both have time-lapse video however).

I shoot in RAW mode to ensure to get the max info from the images, in case I want to do more post-processing work, images will always contain original detail and more pixel information than a compressed JPG file.

For the record I shoot all my astrophotos using "Daylight" white balance, more for the fact that I always know what it was, it's always consistent, and it seems quite logical to me as that's what our eyes sort of are calibrated for. However my point of view is people can use whatever suits them ---- after all, isn't color in photos a *perception* thing? and it even varies from person to person, so I am kind of amused by the long discussions by 'purists." As photographers we change and balance the colors, and alter them, increasing saturation etc all the time for better effect. Even what comes out of the camera is already some engineers' interpretation of a color balance.

Fast_Larry said:

For the M6 Mk II I set the shutter for "Electronic" mode to remove any vibration from the shutter opening or closing, I use the Canon remote control phone app with Bluetooth paired to release the shutter for both the M6 and M6 Mk II, so there is no vibration from the camera or user.

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This reply is just in relation to using Electronic Shutter settings...
You won't be getting movement from the camera in Mechanical Mode although the loudness of the shutter release implies more movement. The application of Electronic Shutter is more useful for stopping 'Shutter Shock' in a mirrorless camera than to eliminate vibration in the fraction of a second that the shutter closes. On a DSLR camera, it was often recommended that the mirror be "locked up" before astrophotographic use ...because the hard "slap" action of the mirror flipping up/down was causing movement in stars since it caused minute movement in the camera due to inertia and weight distribution from the weight of the glass mirror. Depending on the sturdiness of the tripod and the stillness of the air at the time, I will use either a 2-second or 10-second delay with the self-timer to prevent vibration. You can take this another step further by activating touch-release on the LCD screen. Using a heavy tripod is going to have a noticeable amount of difference in the sharpness of the images compare to using a lighter tripod. Thought this can be countered by hanging a 2liter jug of water or sand from the middle of the tripod (to keep movement to a minimum).
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As a result, I do not consider Electronic Shutter settings to be useful with mirrorless cameras unless being used for either "silent mode photography" or when "shutter shock" becomes an issue (which it is with the recent EOS R5 camera due to higher pixel-count sensor. The higher the resolution of the sensor, the bigger the problem becomes... which is why the R6 isn't suffering the same issues at the same shutter speeds as the R5.
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I find that using Bluetooth or WiFi with the M6 tends to drain the battery too fast for my liking. Using a Remote Trigger is a better solution... and both the M5 and M6 have both an Infrared sensor for a handheld remote release (Canon RC-6 Remote Control) as well as a Port designed to accommodate a manual release cable (see image below).
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For anyone considering a remote, the RC-6 is just fine if you're avoiding star trails. For shots longer than 30 seconds you will want to consider the remote trigger release like the one below (called the RS-60E3). There are other non-Canon models and intervalometers available as well. Whilst I have both of the Canon release devices, I no longer use them at this time, preferring instead to use the self-timer built into the camera.
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EOS M6 with remote tether for longer-than-30 second exposures.


EOS M6 + 11-22mm lens - using the remote tether for capturing the International space station... this was a 73 second exposure. Note that the stars are shifting, but not the ISS or the foreground.


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Regards,
Marco Nero.

I believe also that on several camera models, like Canon R5/R6, using the electronic shutter reduces the dynamic range?

I don't know if this affects the M6ii as well.

Using smartphone for shutter release is really useful btw, you don't have to bring a remote shutter release accessory along with you. Good for bulb exposures.

Thanks for this informative post!

Based on your experience with an f/2.8 135mm lens, I hope that on my Fuji X-H1 with an f/2.8 140mm I can achieve similar results. I will have to learn how to do stacking though!

Next summer when skies are clear, the Milky Way is visible, and the nights a bit warmer again...

Here are my best photos so far with the M6 Mark II and 135mm f2.8 lens or 200mm f3.5 lens (both Minolta MC). From my testing, however, I am starting to feel like this is the limit without a tracking mount, just a tripod... I'm having to shoot at ISO 2500 to 5000 to get this kind of result, and adding more frames doesn't seem to really increase the level of detail or reduce the noise level much, which is strongly tied to the ISO. When image processing I have to work very hard to bring detail barely up from the background noise. I am starting to feel like the only way to get further is to use a tracking mount to get much longer exposures and go to lower ISOs for really clear photos, in the ISO 100-800 range as is possible. I choose an ISO which just begins to show background light in the sky, which is something like 0.8 - 2 seconds at ISO 2500. Using a tracking mount, you'd be able to take multiple 30-60 second exposures to be stacked, each at a low ISO that would give a far greater dynamic range.... and the resulting image should look so much clearer with a lot more detail to work with, and lower noise.

Larry,

Really nice.. what are the technical parameters around these shots.. any filters ?
----Daniel----

Fast_Larry said:

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Nice go at Andromeda.

R2

--
Good judgment comes from experience.
Experience comes from bad judgment.

jaadwa said:

Larry,

Really nice.. what are the technical parameters around these shots.. any filters ?
----Daniel----

Click to expand...

I took that photo of M31 with the Canon M6 mark II, a vintage 1970's Minolta MC Celtic 135mm f2.8 lens wide open at f2.8 with an $11 Fotasy Minolta to EOS-M adapter off ebay, 100 separate exposures of 2 seconds each, 10 dark frames, 10 bias frames stacked using DeepSkyStacker free software (took about an hour on a Dell Windows 10 laptop).

I had the camera mounted on a meade ETX-90 telescope, the motor drive doesn't work well and does not drive at full speed any more so 2 seconds is the longest exposure that gave pinpoint stars.

I used ISO 2500, however my own experience and testing, and research after that on using ISOs with various cameras seems to yield that the Canon M6 Mark II is relatively ISO invariant from about 400 and higher, so I could probably have used a lower ISO than 2500 with no real increase in noise.

Interestingly I tried again this Monday with a vintage Minolta MC 200mm f3.5 lens, and a home-altered Viltrox 0.71 speed booster that can now mount the Minolta SR lenses to EOS-M, yielding a 142mm f2.5 lens slightly sharper than the 135mm! I did this only on a tripod with no motor drive, and was only able to use 0.8 seconds exposure on each frame to get pinpoint stars. I did 200 stacked exposures. And at the end of all of that I could not get as much faint, fine image detail from M31 as I got in my first attempt with the 135mm!

This shows me that I am at the limit of what I can capture in each frame above the 'noise level' with my lens --- and the ONLY WAY I can get fainter detail is to get a tracking mount and to take longer exposures. Stacking more frames does not result in more detail in the final image, if each frame can't pull any more detail out of the noise --- the way to improve the signal to noise ratio is to get more photons in the frame, i. e. longer exposure.

I think if I can get a really good tracking mount like the iOptron Sky Tracker Pro or Sky Guider Pro, I would try to shoot around 50 frames of 60-90 seconds each.

I also did not use any filters, however there is some light pollution where I shoot at the ocean near Howard Park in Tarpon Springs, Florida, and I am considering something like the SkyTech LPro Max or one like it. My testing shows I am also probably being limited by some light pollution.

The shot of m42 in Orion was with the Canon M6 Mark II, the vintage Minolta 200mm f3.5 and Viltrox 0.71x speed booster (so an effective 142mm f2.5 lens), 200 stacked 0.6 second exposures on tripod with no drive at ISO 5000.

Pleiades was 100 stacked exposures with 200mm f3.5 lens (no speed booster) at ISO 2500, 0.4 second exposure.

After reading a lot more I think I should start shooting 50 dark frames, 50 bias frames, and start also shooting flats and flat darks to improve the stacked result, smoothing out more noise and getting more uniform brightness across the frame.

BTW here is an excellent article about ISO, how it really works in digital cameras, and how to decide what setting to use for astrophotography, just found this last night. https://petapixel.com/2017/03/22/find-best-iso-astrophotography-dynamic-range-noise/

Tim van der Leeuw said:

I believe also that on several camera models, like Canon R5/R6, using the electronic shutter reduces the dynamic range?

I don't know if this affects the M6ii as well.

Using smartphone for shutter release is really useful btw, you don't have to bring a remote shutter release accessory along with you. Good for bulb exposures.

Click to expand...

You raise a really interesting point. I wasn't aware, and am surprised that, using the electronic shutter could result in reduction of dynamic range. I've done a little hunting around the topic, and it does appear that some cameras do show a reduction in dynamic range when the electronic shutter is used.

I am particularly interested---one of the reasons I switched from the Canon m6 to the m6 Mark II was so that I could use the electronic shutter for all my astrophotography. I was definitely seeing a reliable loss of sharpness due to the mechanical shutter shake on Moon and planets shots though a Meade ETX90 at prime focus at exposures of 1/15 s thru 1/1000 (slower than 1/15th results in motion from Earth's rotation). With the Mark II a much higher proportion of the shots are sharp. I wouldn't dream of shooting the dozens or hundreds of stacked exposures for deep sky stacking using the mechanical shutter mode due to the potential shake.

Some of the loss of dynamic range from some cameras may be due to the particular camera dropping the bit depth of the image in electronic shutter mode to get a faster line by line image. Some of the loss for some or all cameras may be due to the readout taking up to 1/10 of a second, effectively meaning the time for the sensor to be 'fully read' could be 1/10 of a second longer than needed --- you can see how this would result in more noise for a 1/500th second exposure, however for 0.5 second and longer exposures used for deep sky work, this effect might not really matter that much.

I use the electronic shutter option most of the time, even in everyday shooting for landscapes. I only use the mechanical shutter for action shots.

I find that the images out of the M6 Mark II all around, even with electronic shutter, are fabulous, noticeably cleaner with less noise, especially in low light, than the M6 I had, and way better than the 70D and Canon T1i I've had in the past. I would be surprised if it turns out the electronic shutter reduces the dynamic range noticeably in the M6 Mark II...

Fast_Larry said:

Here are my best photos so far with the M6 Mark II and 135mm f2.8 lens or 200mm f3.5 lens (both Minolta MC). From my testing, however, I am starting to feel like this is the limit without a tracking mount, just a tripod... I'm having to shoot at ISO 2500 to 5000 to get this kind of result, and adding more frames doesn't seem to really increase the level of detail or reduce the noise level much, which is strongly tied to the ISO. When image processing I have to work very hard to bring detail barely up from the background noise. I am starting to feel like the only way to get further is to use a tracking mount to get much longer exposures and go to lower ISOs for really clear photos, in the ISO 100-800 range as is possible. I choose an ISO which just begins to show background light in the sky, which is something like 0.8 - 2 seconds at ISO 2500. Using a tracking mount, you'd be able to take multiple 30-60 second exposures to be stacked, each at a low ISO that would give a far greater dynamic range.... and the resulting image should look so much clearer with a lot more detail to work with, and lower noise.

Click to expand...

WOW! That came out real nice! Are you saying this is or is not the results with stacking? What Bortle scale was this taken at?

Marco Nero said:

Tim van der Leeuw said:

Marco Nero said:

ScottPeach said:

This is the first time I’ve ever commented on a review. I just had to let you know how useful this is to me. After a lot of searching I finally know why lens I need!! Thank you!!

Click to expand...

Which lens have you decided to go with? My personal preference for Milky Way shots is the EF-M 22mm f/2 STM lens at present (for the EOS M cameras).

Click to expand...

Yet another poster here on this old thread.
Beautiful pictures which you posted earlier, and some very useful information.

I know you like the EF-M 22mm f/2 lens but I'm considering the Sigma EF-M 16mm f/1.4 lens as it has a wider FoV and aperture, or possibly looking for a fast & wide EF lens. I was already considering it, but after reading your post I'm even more convinced that I need a lens like that for better results at night.

Click to expand...

The Sigma AF 16mm f/1.4 DC DN (C) - EOS M-mount lens is a lens I've written about before... it's a wide, bright lens but it's 3 (or 4 ?) times more expensive than the EF-M 22mm f/2 STM lens (depending where you are in the world) . It's a better choice if you want an even wider view of the Milky Way. But beware of Sigma and their inability to guarantee compatibility with future Canon bodies. To quote myself from July 2019: "For Astrophotographers: the Rokinon 12mm lens (yes, I know this isn't the 16mm version) offers more contrast and an ability to expose for up to 7 seconds longer (than the Sigma 16mm f/1.4) when comparing to the two lenses. The Sigma produces some very prominent coma (as predicted) in the sides and corners.". This means you'll need to stop down the lens considerably for astrophotography to reduce the coma. I don't know by how much, but lenses like Canon's EF 24mm f/1.4L II USM require something closer to f/2.8 to eliminate the coma. The Sigma AF 16mm f/1.4 shares several of the design aspects of the Canon EF 24mmL lens (which isn't much of a surprise considering Sigma likely reverse-engineered the Canon EF lens) so I'd guess the coma limitation is probably close to the same. Just be aware of these aspects before making your purchase because this lens is similar in cost to the Canon EF-M 32mm f/1.4 lens... which is probably too narrow for most people wanting to do astro-landscapes. Right now, for EF-M lenses, the best choice for astro are the manual lenses from Samyang/Rokinon. They have be best coma control and come in several wide FOV options.

Marco Nero said:

I've been shooting some shots with my EF-M 11-22mm and have been pleased with the results but yes, sensor noise is an issue. I like the wide angle though for shooting the skies.

Click to expand...

All lenses can capture the Milky Way in a matter of seconds... if the sensor is large enough - but f/4 lenses are a bad choice. This is because the narrow aperture and high contrast of this lens will result in a need for much longer exposures using higher ISO settings. The combined result is a lot of grain and sensor noise as well as banding. The EF-M 11-22mm f/4-5.6 lens might do well on a sky-tracking EQ mount for telescopes but it will produce inferior results on the EOS M series cameras if only a tripod is used. The lens produces marginally "better" results on a more recent model camera like the M6 but it's still grainy. I've rated it as the least impressive native EF-M lens for astro.
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I recently moved to the EOS R system (Specifically the EOS Ra) for Astrophotography and won't likely shoot as much Astro with the EOS M cameras/lenses from this point forward. The difference in ability from the EOS Ra has made my EOS M6 and EOS 6D DSLR virtually redundant.

Click to expand...

Which wide angle lens do you recommend for the FF R cameras?

3V AudioVideo said:

Fast_Larry said:

Here are my best photos so far with the M6 Mark II and 135mm f2.8 lens or 200mm f3.5 lens (both Minolta MC). From my testing, however, I am starting to feel like this is the limit without a tracking mount, just a tripod... I'm having to shoot at ISO 2500 to 5000 to get this kind of result, and adding more frames doesn't seem to really increase the level of detail or reduce the noise level much, which is strongly tied to the ISO. When image processing I have to work very hard to bring detail barely up from the background noise. I am starting to feel like the only way to get further is to use a tracking mount to get much longer exposures and go to lower ISOs for really clear photos, in the ISO 100-800 range as is possible. I choose an ISO which just begins to show background light in the sky, which is something like 0.8 - 2 seconds at ISO 2500. Using a tracking mount, you'd be able to take multiple 30-60 second exposures to be stacked, each at a low ISO that would give a far greater dynamic range.... and the resulting image should look so much clearer with a lot more detail to work with, and lower noise.

Click to expand...

WOW! That came out real nice! Are you saying this is or is not the results with stacking? What Bortle scale was this taken at?

Click to expand...

The photos I posted were stacked using deep sky stacker, yes. The site I observe from is Bortle class 5. To go for fainter objects I think I will have to try a light pollution filter and go for longer exposures with a tracking mount.

Marco Nero said:

ISO can range from ISO 800 to 1600 or up to 3200 (depending on the lens and scene).
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* Try ISO 1600 and then crank up to 2000, 2500 and 3200 as needed.
Son't be afraid to experiment. An ISO setting and shutter speed combo with a particular lens will usually produce nearly identical results if the weather and sky conditions are the same. Higher ISO and a narrower shutter speed can often capture more details than a slower shutter speed and lower ISO settings. The signals-to-noise ratio is often better with higher ISO for astro shots but I draw the line at around ISO 3200 and keep all my shots at this ISO setting or lower.

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Thanks again for posting this nice gallery of your images, and for all your insights. Very, very nice shots, it's great of you to share for others to enjoy and to help others improve their work.

I too have experimented a lot with changing ISO settings for astrophotography. I studied astronomy way, way back in college and was actually a professional astronomer for half a decade before going into software development. Much of my experience comes from doing astrophotography with old film bodies like the Canon F-1 with telescopes and fast (now) vintage Canon FD lenses.

Back in the day with film, ISO was a measure of film's sensitivity to light and was of course a key characteristic of doing photography, you chose your ISO (or ASA as it were) carefully to achieve a particular result or to work around limitations you had gathering enough light. So I thought I had a good understanding of what ISO means and does.

However, I've recently read up on it a lot, only to find that with digital photography, ISO 'settings' function and behave differently than they did in the film days... it's a whole new ballgame and I realize that I, and probably many others, actually may not really understand ISO settings and dynamic range on digital cameras as well as we thought we did.

This article is one of the best ones I've found that explains it, it's worth a read:

https://petapixel.com/2017/03/22/find-best-iso-astrophotography-dynamic-range-noise/

The most important takeaway is that changing the ISO does not in any way increase the 'sensitivity' of the sensor --- a similar number of photons are going to be captured by each pixel at any ISO given the same shutter speed and aperture! Changing the ISO for a digital camera only results in the 'gain' on the sensor's reading of the image being boosted, either in an analog way (upstream) or digitally (downstream). For many cameras raising the ISO actually may be detrimental.

I notice a lot of your shots are with the Canon M6, which I used for about a month last November before upgrading to the M6 Mark II. In particular, those two cameras are basically ISO-invariant from about ISO 400 and up for low-light photography and especially astrophotography... meaning that cranking the ISO higher than 400 results in no benefit for the image in reducing noise, and actually would be detrimental to the dynamic range as you are limiting the highlight detail that can be captured. This behavior is highly dependent on the camera brand and model --- for many other Canon digital cameras there IS a reduction of noise at ISO 1600, 3200, 6400, or whatever, and there is a different 'optimal' ISO to use for astrophotography.

Sure, at ISO 400, after you take your Milky way astrophoto, for example, the image that will come up on the camera afterwards will *look* dark, however, in post-processing, pushing that image 3 EV values will result in a nearly *identical* image to one you would have gotten at ISO 3200, with about the same amount of noise. However the ISO 400 image is less susceptible to the highlights being 'blown out' the way they might be if the ISO 3200 setting is used. (Note that this assumes you are always shooting in RAW mode which is capturing the full bit-depth of the image from each pixel.)

This also means you might see 'dark' images on the view screen as well as you are taking photos, but don't be deterred by it... the same light data will get recorded at iSO 400 as it does at ISO 3200 with about the same amount of noise, as long as the shutter speed and aperture are the same!

As I've mentioned in other posts, the Canon M6 Mark II has a setting in its menu to 'disable' Exposure Simulation --- meaning that the view screen will not try to show you what the image looks like at your chosen ISO/aperture/shutter speed, but will just auto-adjust it. I don't remember if the Canon m6 has the same setting.

As I've mentioned in other posts, the first time I disabled Exposure simulation on the M6 Mark II I was astonished that the gain automatically cranked to maximum for deep sky work, and M31 and the Orion nebula actually appeared on the viewscreen with an 135mm f2.8 lens!! I could actually compose the picture for them, and manual focusing became so much easier as the faintest stars would only 'pop' into the frame when the focus was dead on (when viewing at 10x manual focus zoom mode).

I'm curious what you are finding with the Canon R mirrorless camera with regards to ISO, I haven't looked into those.

Marco Nero said:

Fast_Larry said:

For the M6 Mk II I set the shutter for "Electronic" mode to remove any vibration from the shutter opening or closing, I use the Canon remote control phone app with Bluetooth paired to release the shutter for both the M6 and M6 Mk II, so there is no vibration from the camera or user.

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This reply is just in relation to using Electronic Shutter settings...
You won't be getting movement from the camera in Mechanical Mode although the loudness of the shutter release implies more movement. The application of Electronic Shutter is more useful for stopping 'Shutter Shock' in a mirrorless camera than to eliminate vibration in the fraction of a second that the shutter closes. On a DSLR camera, it was often recommended that the mirror be "locked up" before astrophotographic use ...because the hard "slap" action of the mirror flipping up/down was causing movement in stars since it caused minute movement in the camera due to inertia and weight distribution from the weight of the glass mirror. Depending on the sturdiness of the tripod and the stillness of the air at the time, I will use either a 2-second or 10-second delay with the self-timer to prevent vibration. You can take this another step further by activating touch-release on the LCD screen. Using a heavy tripod is going to have a noticeable amount of difference in the sharpness of the images compare to using a lighter tripod. Thought this can be countered by hanging a 2liter jug of water or sand from the middle of the tripod (to keep movement to a minimum).
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I find that using Bluetooth or WiFi with the M6 tends to drain the battery too fast for my liking. Using a Remote Trigger is a better solution... and both the M5 and M6 have both an Infrared sensor for a handheld remote release (Canon RC-6 Remote Control) as well as a Port designed to accommodate a manual release cable (see image below).

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Thanks for your insight. With the M6 I was using the self timer both at 2 seconds and 10 seconds, but on the more entry-level Meade ETX90 the mount is so shaky that even 10 seconds probably wasn't enough time to damp out the vibrations!! Since I tend to shoot many shots in sequence for stacking, shooting many exposures became very tedious and time-consuming with the self timer.... for the conjunction of Jupiter and Saturn where the planets were getting lower to the horizon with each minute, this was especially a problem.

With the M6 mark II the bluetooth app was a Godsend... I don't see a problem, or perhaps enough of a problem, with battery life, I have 2 Canon batteries (not 3rd party) and even in a 2-hour session of nearly continuous shooting (500-700 exposures including darks and bias frames), I don't even run one of them out, so for me the app is a great solution. The intervalometer also lets me set up 10 or even 50 shots to be taken in sequence at one touch of the shutter button on the app, and with the electronic shutter being used, the camera contributes no vibration and is totally silent as it shoots, so I can have it fire off 50 photos extremely quickly with less than a second delay between them.

For deep sky work, using electronic shutter and the app, I see zero vibration, Manual inspection of every file shows that are all tack sharp (good way to check for planes and satellites going through the image too!).

For some reason with the M6 nearly all my Moon shots through the telescope had some sort of vibration, all were 1/15 - 1/1000 second... they were in focus, just had movement... with the Mark II nearly all of them are now sharp. Could have been the tap on the screen to start the self timer, I'm not sure.... the way for me to find out if the electronic shutter is having an effect is for me to do more testing. I don't have the M6 any more but can test on the Mark II with and without electronic shutter to see if that's a factor.

On another topic. I recently tried a Viltrox 0.71x speed booster with the ETX90, testing both with and without it at prime focus on a quarter Moon, with very favorable results. I've found the speed booster to work very well with telephoto lenses in general, with no decrease in sharpness that I can see, and possibly even an increase in sharpness in some cases (the opposite f what you see with a teleconverter, compressing the image might hide flaws in the lens!). The M6 mark II's sensor has so much resolution that I still have to downscale Moon images at prime focus even with the speed booster, and it seems that the extra stop of light makes it much easier to get really nice ISO 100 images (I've attached one).

I took this with Canon M50 unmod. So clearly these cameras are capable of good stuff.

Jezz1 said:

I took this with Canon M50 unmod. So clearly these cameras are capable of good stuff.

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Very nice! What was your setup and exposure (including ISO)?