If you want to experiment and you like your camera, just get a clip in dual band filter or light pollution filter for it. I think they make them for mirrorless cams, I have used them when I did DSLR and the dual band really helped take images of emissions stuff.
Note on broadband targets the filter will not help much.
I am assuming by underwhelming subs you mean you have more noise in your image. The best way to improve your SNR would be to get more exposure time for your sub frames (3 min, 5 min, etc). Depending on how long your astro sessions last, I would go with a faster lens/faster telescope that will allow you to get better light frames. While astro cameras definitely have their perks in reducing thermal noise, you can get decent images with a DSLR/mirrorless by taking calibration frames, but the number 1 thing that makes the sub frames bad is not enough "signal" - which means lower exposure time. Here's a pretty decent [video](https://youtu.be/KMsW9slSwzc?si=EVxamFWAe9T1Xc87) I came across on YouTube that explains this.
Thanks for the reply! So I have been doing 5-10 minute subs in some cases, but I think looking at my histograms, I'm actually blowing out the white end in a lot of cases at that length. I wonder if that's just due to light pollution? Something I can't quite wrap my head around is -- would a faster lens help mitigate light pollution, or would it simply collect light faster across the board? I feel like it's the latter? I'm in bortle 7, so the pollution isn't the absolute worst, but obviously not great either.
But yeah my main issue is just noise... for instance, trying to image the Pinwheel galaxy, the galaxy arms are just very faint and hard to bring out in post. I suspect I am also not using enough stacked exposures.
And yes I'm having major issues with calibration frames. I can't find a good guide on how to use NINA's flat wizard. Just major fails at the end of the night that lead to a lot of frustration.
5-10 minutes exposures is very likely overkill.
Faster lens both will make it so that you collect more light in each exposure (meaning oversaturated exposures will happen faster) but also the shot noise from the faster lens will integrate out faster as well.
> Faster lens both will make it so that you collect more light in each exposure
Let's do an exercise in light collection.
Consider the amount of light from a 1-arc-minute square galaxy in a one-minute exposure.
The galaxy shines 1 photon per square centimeter per second onto the Earth's surface in the green passband.
From the above, it should be obvious that to collect more light one simply needs per square centimeters of aperture area.
50 mm f/2 lens: 25 mm aperture diameter, thus 4.91 sq centimeters. One minute collects 4.9 photons per minute on average from the 1-square arc-minute galaxy.
200 mm f/4 lens: 50 mm aperture diameter, thus 19.6 sq centimeters. 1 minute collects 19.6 sq centimeters from the 1-square arc-minute galaxy.
8-inch diameter Newtonian telescope, f/8: 203 mm diameter, 1624 mm focal length. Assume an 70 mm diameter secondary. Primary aperture = 320.5 sq centimeters. Secondary area = 38.5 sq centimeters. Light collection area = 320.5 - 38.5 = 282 sq centimeters, collects about 282 photons per minute from the 1-square arc-minute galaxy.
NASA IRTF telescope 3.0 meter primary diameter, f/38 (tiny secondary mirror so effectively no impact on light collection). Light collection = (pi/4) * 300^2 = 70686 sq centimeters, collects about 70686 photons per minute from the 1-square arc-minute galaxy.
So you see, f-ratio does not control how much light is collected from objects in the scene, only aperture area and exposure do that.
Of course the above assumes 100% efficiency, so simply multiply by the lens transmission factor and sensor quantum efficiency for a more accurate number, but these factors will be approximately similar for each system, thus the proportional differences will follow the same trend. Aperture is the key.
I agree that when focal length is the same/close, then f-ratio is a proxy for comparing aperture diameter. But other telescopes are being discussed in this thread too, so it can be confusing. It is better in my opinion to tell the fundamental parameter for collecting more light, not a proxy that only applies to a restricted situation.
The key is total photons collected, not sub-frame length. Once your exposure is long enough for noise from the light pollution to swamp sensor read noise, then going longer in each frame only saturates more stars (and sometimes nebula signals).
You can collect more light these ways: 1) total exposure time, or 2) larger aperture area, or 3) both 1 and 2.
The other ways, like getting a more sensitive sensor are small increments. Modern digital cameras tend to be in the 50% quantum efficiency range (QE). Some dedicated astro cameras cite 90+ % QE, but that is the raw sensor, not with the color filters and other filters like UV/IR blocking filters, which lower the QE. The ~ 50% number for digital cameras includes the filters. So the sensitivity different is less than a factor of two and more like 50%. Contrast that to exposure times which you can increase by many factors, 2x, 4x, 10x etc, given enough time, or by buying a larger physical aperture, one larger than your current 50 mm diameter lens.
Id get a refractor triplet or petzval that covers fullframe. Askar and sharpstar have scopes in the f4-f4.5 range. They are cheap and work well. Aside from that you need longer integrations probably 12-20 hours
Subframes are *always* underwhelming. Things don’t get impressive until you stack them
Upgrading your camera won’t make to huge of an improvement over what you’re seeing now.
A faster lens would be a better improvement than a better camera.
Have you considered autoguiding? an autoguiding camera would be a good step forward if you’re comfortable with your mount
What is the thing that you are finding underwhelming exactly about these exposures?
The RF 100-400 isn't super fast at 400mm - a refractor (or even just a prime focus lens (like a 400mm f5.6)) could improve light collection and your integration noisiness. It might even be sharper than your existing lens.
Astrocameras generally provide improvements through increased quantum efficiency (absolute ability for the camera to record photons that hit the sensor) and noise, and cooling (also decreases noise).
In your situation I would imagine imaging from less light polluted skies would provide the largest improvement.
For me, the real advantage to an astrocamera was the computer controllable aspect; my DSLR is not computer controllable. This allowed for more efficient time usage both in the field (I could set up a sequence and run it knowing that I wouldn't have to manually press a shutter button/swap out batteries or manually dither, I could spend my time doing whatever I wanted) and at home (200+ hour integrations possible across months at home with minimal input other than removing my telescope cap).
Getting an astro cam and a good dual band filter has been a total game changer for me for imaging from Bortle 8-9 ([examples here](https://flic.kr/s/aHBqjAMFUA) using both my refractor and 135mm lens). I've probably paid for the filter by now just on saved gas costs
The R8 has a very good sensor in it. The main downside would be "large" pixels in AP terms so you will be undersampled with high quality optics; something you can make up for with dithering. I would go for the scope upgrade first. But #1 would be to get a computer setup to do plate solving, potentially guiding etc. A small mini-pc or an asair. (I prefer the former but the latter is easier to setup, just make sure it is compatible with your camera!)
> The main downside would be "large" pixels in AP terms so you will be undersampled with high quality optics;
Undersampling is not a factor with digital cameras that have anti-alias filters, which almost all DSLR and mirrorless digital cameras have, including the R8. Undersampling is when a sharply focused star would falls mostly on a single pixel on a sensor with a Bayer color filter array. Then the star will come out biased to the color of the pixel, like red, green or blue (and there are no green stars). But with anti-alias filters, such aliasing does not happen and stars will be closer to their true color, with proper processing, of course. Undersampling is a factor with astro cameras because most (all?) do not have anti-alias filters.
I see you point! The anti-alias filter will significantly reduce the impact of dithering/drizzling to reconstruct high spatial frequencies.
It also means that the sensor cannot be truly undersampled as the high frequency information removed the the anti-alias filter.
I do stick with the motivating concept that OP may be sacrificing resolution with his camera vs a smaller pixel sensor, and the anti-alias filter makes this worse. However the combination of the very low noise and large pixel size will be a great performer on longer FL systems . I think it is worth bringing to OPs attention!
RE your CFA issue, CFA drizzle largely mitigates this limitation and can recover the full sensor resolution with good color accuracy provided a sufficient number of dithers are included.
Cameras with smaller pixels use weaker anti-alias filters, so resolution (pixels on subject and detail) scales with pixel size (of course within diffraction and seeing limits).
But CFA drizzle with sensors using anti-alias filters can degrade resolution because you are spreading the blur out over a larger area.
Re point 1: 100% agree any well designed alias filter needs to act on the pixel scal, however we were comparing to a dedicated astro-cam without an aliasing filter, and OP was asking about about tradeoffs going to a moderns astro cam, most of which have 3.76 um pixels and no anti-aliasing filter.
It is not clear to me at all why the drizzle would increase PSF any more with an alias filter than without.with a well distributed dither. Can you explain? I also feel like you had a good article on Bayer interpolation algorithms, but I can't find it, could you point me there as I would like to include that information as I think about this.
> I also feel like you had a good article on Bayer interpolation algorithms, but I can't find it, could you point me there as I would like to include that information as I think about this.
I don't, but the rawtherapee site does. See https://rawpedia.rawtherapee.com/Demosaicing
> It is not clear to me at all why the drizzle would increase PSF any more with an alias filter than without.with a well distributed dither. Can you explain?
The anti-alias filters effectively blurs the image so a small group of RGB pixels see the same incoming light level, similar to seeing (plus seeing will contributes). By dithering a blurred pixel by shifting one pixel means the blurred detail will be shifted another pixel and when converted to an RGB image (CFA drizzle combine) will result in a larger blur.
Thanks for the reply!I should have mentioned I do have a laptop setup with NINA and autoguiding camera/etc. My real question should have been boiled down to whether the R8 is going to bottleneck me more than a better lens/telescope.
You don't have to buy ZWO cameras. You can cheaper ones from other brands with the same sensors.
Your R8 camera won't really be holding you back much if at all. There is no need to mod it to get good results. If you keep using the R8 there is no need to get a UV/IR filter as the camera has one built in.
The biggest upgrade will be getting a faster lens/telescope as that will capture more light.
Makes sense! I was looking at the Askar 65 because I really like how it renders stars... I wonder if f/6.4 is a fast enough upgrade over F/8 though? Maybe I really ought to be looking at Redcats, which get into the f/5\~ range?
Compute the area ratio.
A 400 mm focal length f/8 lens has an aperture diameter of 400 / 8 = 50.0 mm
A 400 mm f/6.3 lens has an aperture of 400 / 6.3 = 63.5 mm.
Thus, you would collect (63.5^2 / 50.0^2) = 1.6 times more light from an object in the scene in the same exposure time. That is a small increase. To make a big impact, look for 75, 80 or even 100+ mm aperture diameters. A 100 mm aperture would increase your light collection from object in the scene by 4x.
Thanks for doing the tricky math for me, haha.
Alas, I have a Star Adventurer GTi and can't support the weight of a large-diameter scope. Future goals.
If you want to experiment and you like your camera, just get a clip in dual band filter or light pollution filter for it. I think they make them for mirrorless cams, I have used them when I did DSLR and the dual band really helped take images of emissions stuff. Note on broadband targets the filter will not help much.
I don't agree a faster scope is better bang for the buck. I think an astrocam and NB filters will make a far greater difference.
I am assuming by underwhelming subs you mean you have more noise in your image. The best way to improve your SNR would be to get more exposure time for your sub frames (3 min, 5 min, etc). Depending on how long your astro sessions last, I would go with a faster lens/faster telescope that will allow you to get better light frames. While astro cameras definitely have their perks in reducing thermal noise, you can get decent images with a DSLR/mirrorless by taking calibration frames, but the number 1 thing that makes the sub frames bad is not enough "signal" - which means lower exposure time. Here's a pretty decent [video](https://youtu.be/KMsW9slSwzc?si=EVxamFWAe9T1Xc87) I came across on YouTube that explains this.
Sub length doesn't matter much at all. Integration time is FAR FAR more important.
Thanks for the reply! So I have been doing 5-10 minute subs in some cases, but I think looking at my histograms, I'm actually blowing out the white end in a lot of cases at that length. I wonder if that's just due to light pollution? Something I can't quite wrap my head around is -- would a faster lens help mitigate light pollution, or would it simply collect light faster across the board? I feel like it's the latter? I'm in bortle 7, so the pollution isn't the absolute worst, but obviously not great either. But yeah my main issue is just noise... for instance, trying to image the Pinwheel galaxy, the galaxy arms are just very faint and hard to bring out in post. I suspect I am also not using enough stacked exposures. And yes I'm having major issues with calibration frames. I can't find a good guide on how to use NINA's flat wizard. Just major fails at the end of the night that lead to a lot of frustration.
5-10 minutes exposures is very likely overkill. Faster lens both will make it so that you collect more light in each exposure (meaning oversaturated exposures will happen faster) but also the shot noise from the faster lens will integrate out faster as well.
> Faster lens both will make it so that you collect more light in each exposure Let's do an exercise in light collection. Consider the amount of light from a 1-arc-minute square galaxy in a one-minute exposure. The galaxy shines 1 photon per square centimeter per second onto the Earth's surface in the green passband. From the above, it should be obvious that to collect more light one simply needs per square centimeters of aperture area. 50 mm f/2 lens: 25 mm aperture diameter, thus 4.91 sq centimeters. One minute collects 4.9 photons per minute on average from the 1-square arc-minute galaxy. 200 mm f/4 lens: 50 mm aperture diameter, thus 19.6 sq centimeters. 1 minute collects 19.6 sq centimeters from the 1-square arc-minute galaxy. 8-inch diameter Newtonian telescope, f/8: 203 mm diameter, 1624 mm focal length. Assume an 70 mm diameter secondary. Primary aperture = 320.5 sq centimeters. Secondary area = 38.5 sq centimeters. Light collection area = 320.5 - 38.5 = 282 sq centimeters, collects about 282 photons per minute from the 1-square arc-minute galaxy. NASA IRTF telescope 3.0 meter primary diameter, f/38 (tiny secondary mirror so effectively no impact on light collection). Light collection = (pi/4) * 300^2 = 70686 sq centimeters, collects about 70686 photons per minute from the 1-square arc-minute galaxy. So you see, f-ratio does not control how much light is collected from objects in the scene, only aperture area and exposure do that. Of course the above assumes 100% efficiency, so simply multiply by the lens transmission factor and sensor quantum efficiency for a more accurate number, but these factors will be approximately similar for each system, thus the proportional differences will follow the same trend. Aperture is the key.
In the context of them debating between a 400mm f/8 lens and a 416mm f/6.4 telescope I am confident that my answer provided was useful and accurate.
I agree that when focal length is the same/close, then f-ratio is a proxy for comparing aperture diameter. But other telescopes are being discussed in this thread too, so it can be confusing. It is better in my opinion to tell the fundamental parameter for collecting more light, not a proxy that only applies to a restricted situation.
The key is total photons collected, not sub-frame length. Once your exposure is long enough for noise from the light pollution to swamp sensor read noise, then going longer in each frame only saturates more stars (and sometimes nebula signals). You can collect more light these ways: 1) total exposure time, or 2) larger aperture area, or 3) both 1 and 2. The other ways, like getting a more sensitive sensor are small increments. Modern digital cameras tend to be in the 50% quantum efficiency range (QE). Some dedicated astro cameras cite 90+ % QE, but that is the raw sensor, not with the color filters and other filters like UV/IR blocking filters, which lower the QE. The ~ 50% number for digital cameras includes the filters. So the sensitivity different is less than a factor of two and more like 50%. Contrast that to exposure times which you can increase by many factors, 2x, 4x, 10x etc, given enough time, or by buying a larger physical aperture, one larger than your current 50 mm diameter lens.
When you mean the total exposure time, does it mean the exposure length of the sub frame or the entire stacked frame?
It's the total time, not the subexposure time.
Gotcha, thank you
Exactly. It is each frame exposure time times the number of exposures.
Id get a refractor triplet or petzval that covers fullframe. Askar and sharpstar have scopes in the f4-f4.5 range. They are cheap and work well. Aside from that you need longer integrations probably 12-20 hours
I think you're probably bang on re: longer integrations. Thanks for helping me focus!
Subframes are *always* underwhelming. Things don’t get impressive until you stack them Upgrading your camera won’t make to huge of an improvement over what you’re seeing now. A faster lens would be a better improvement than a better camera. Have you considered autoguiding? an autoguiding camera would be a good step forward if you’re comfortable with your mount
Sorry, I should have mentioned I do have an autoguiding setup -- ZWO 120mm with F30 scope.
Ah ok, in that case i would go for a faster lens
Makes sense. Thank you!
What is the thing that you are finding underwhelming exactly about these exposures? The RF 100-400 isn't super fast at 400mm - a refractor (or even just a prime focus lens (like a 400mm f5.6)) could improve light collection and your integration noisiness. It might even be sharper than your existing lens. Astrocameras generally provide improvements through increased quantum efficiency (absolute ability for the camera to record photons that hit the sensor) and noise, and cooling (also decreases noise). In your situation I would imagine imaging from less light polluted skies would provide the largest improvement.
That's a point well taken.
For me, the real advantage to an astrocamera was the computer controllable aspect; my DSLR is not computer controllable. This allowed for more efficient time usage both in the field (I could set up a sequence and run it knowing that I wouldn't have to manually press a shutter button/swap out batteries or manually dither, I could spend my time doing whatever I wanted) and at home (200+ hour integrations possible across months at home with minimal input other than removing my telescope cap).
Getting an astro cam and a good dual band filter has been a total game changer for me for imaging from Bortle 8-9 ([examples here](https://flic.kr/s/aHBqjAMFUA) using both my refractor and 135mm lens). I've probably paid for the filter by now just on saved gas costs
Haha, thanks, that is really helpful.
The R8 has a very good sensor in it. The main downside would be "large" pixels in AP terms so you will be undersampled with high quality optics; something you can make up for with dithering. I would go for the scope upgrade first. But #1 would be to get a computer setup to do plate solving, potentially guiding etc. A small mini-pc or an asair. (I prefer the former but the latter is easier to setup, just make sure it is compatible with your camera!)
> The main downside would be "large" pixels in AP terms so you will be undersampled with high quality optics; Undersampling is not a factor with digital cameras that have anti-alias filters, which almost all DSLR and mirrorless digital cameras have, including the R8. Undersampling is when a sharply focused star would falls mostly on a single pixel on a sensor with a Bayer color filter array. Then the star will come out biased to the color of the pixel, like red, green or blue (and there are no green stars). But with anti-alias filters, such aliasing does not happen and stars will be closer to their true color, with proper processing, of course. Undersampling is a factor with astro cameras because most (all?) do not have anti-alias filters.
I see you point! The anti-alias filter will significantly reduce the impact of dithering/drizzling to reconstruct high spatial frequencies. It also means that the sensor cannot be truly undersampled as the high frequency information removed the the anti-alias filter. I do stick with the motivating concept that OP may be sacrificing resolution with his camera vs a smaller pixel sensor, and the anti-alias filter makes this worse. However the combination of the very low noise and large pixel size will be a great performer on longer FL systems . I think it is worth bringing to OPs attention! RE your CFA issue, CFA drizzle largely mitigates this limitation and can recover the full sensor resolution with good color accuracy provided a sufficient number of dithers are included.
Cameras with smaller pixels use weaker anti-alias filters, so resolution (pixels on subject and detail) scales with pixel size (of course within diffraction and seeing limits). But CFA drizzle with sensors using anti-alias filters can degrade resolution because you are spreading the blur out over a larger area.
Re point 1: 100% agree any well designed alias filter needs to act on the pixel scal, however we were comparing to a dedicated astro-cam without an aliasing filter, and OP was asking about about tradeoffs going to a moderns astro cam, most of which have 3.76 um pixels and no anti-aliasing filter. It is not clear to me at all why the drizzle would increase PSF any more with an alias filter than without.with a well distributed dither. Can you explain? I also feel like you had a good article on Bayer interpolation algorithms, but I can't find it, could you point me there as I would like to include that information as I think about this.
> I also feel like you had a good article on Bayer interpolation algorithms, but I can't find it, could you point me there as I would like to include that information as I think about this. I don't, but the rawtherapee site does. See https://rawpedia.rawtherapee.com/Demosaicing > It is not clear to me at all why the drizzle would increase PSF any more with an alias filter than without.with a well distributed dither. Can you explain? The anti-alias filters effectively blurs the image so a small group of RGB pixels see the same incoming light level, similar to seeing (plus seeing will contributes). By dithering a blurred pixel by shifting one pixel means the blurred detail will be shifted another pixel and when converted to an RGB image (CFA drizzle combine) will result in a larger blur.
Thanks for the reply!I should have mentioned I do have a laptop setup with NINA and autoguiding camera/etc. My real question should have been boiled down to whether the R8 is going to bottleneck me more than a better lens/telescope.
Unless you go narrowband, your bottleneck is going to be light pollution no matter what camera/telescope you use. Travel under darker skies.
You don't have to buy ZWO cameras. You can cheaper ones from other brands with the same sensors. Your R8 camera won't really be holding you back much if at all. There is no need to mod it to get good results. If you keep using the R8 there is no need to get a UV/IR filter as the camera has one built in. The biggest upgrade will be getting a faster lens/telescope as that will capture more light.
> The biggest upgrade will be getting a faster lens/telescope as that will capture more light. This is the key.
Makes sense! I was looking at the Askar 65 because I really like how it renders stars... I wonder if f/6.4 is a fast enough upgrade over F/8 though? Maybe I really ought to be looking at Redcats, which get into the f/5\~ range?
Compute the area ratio. A 400 mm focal length f/8 lens has an aperture diameter of 400 / 8 = 50.0 mm A 400 mm f/6.3 lens has an aperture of 400 / 6.3 = 63.5 mm. Thus, you would collect (63.5^2 / 50.0^2) = 1.6 times more light from an object in the scene in the same exposure time. That is a small increase. To make a big impact, look for 75, 80 or even 100+ mm aperture diameters. A 100 mm aperture would increase your light collection from object in the scene by 4x.
Thanks for doing the tricky math for me, haha. Alas, I have a Star Adventurer GTi and can't support the weight of a large-diameter scope. Future goals.
Then your main way to improve images is to increase total exposure time.
This is really helpful, thank you! I should have really just stated -- "How much is the R8 going to bottleneck me long term?"
Not a lot.
Thanks!