Thank you, to everyone who has supported me here, on buymeacoffee or gofundme! If you'd like to support to, check out my buymeacoffee: buymeacoffee.com/deepskydetail
"Sometimes wrong, sometimes right" should be the mantra of astronomy. Very informative and entertaining video! I saw someone else ask about planetary, you probably got this but let me know if you want to chat about it. Although I'm not an expert, I've been doing planetary for a long time and I'm happy to share what I know. Keep it up!
Thanks, Naz! I agree "sometimes right, sometimes wrong" is a great mantra. Once my shoulder is good enough to lift my C8, I'll pick your brain about some planetary stuff ;)
Thanks for the video, great explanation! Another factor is that the heavier the telescope, the more difficult it is to drag it to places where the sky is darker. And if we consider the recognition of achievements by society as a goal of hobby (yeah! old goof battle of egos!), then, for example, it is easier to win an astrophotography competition with image taken on a telephoto lens plus tracker in the Atacama Desert than with a half-meter telescope in the middle of Tokyo. :-)
Excellent video!! I saw some of the other recent f ratio myth videos and had a number of items that bugged me about them. Very glad you made this video!!
When I make a final result from a stack of images I want the subject to be BIG. It's no use having a nice, bright, noiseless, subject if it is tiny. So all the theory breaks down when the starting assumption is to produce an image where the subject takes up (say) half the final field without appearing pixelated. In practice, most people recognise the constraints placed upon them by the equipment they already have and the amount of LP that reduces their signal/noise ratio,and choose their targets accordingly.
Oh, I definitely agree. SNR is not the only thing that matters. I would definitely trade SNR for resolution when imaging a far away galaxy for example! I wouldn't say that the theory breaks down though. The "triforce" is just as much about resolution as it is for SNR/signal :)
I think the key issue that most people miss (including me), is that while constant f ratio keeps the photons/pixel constant, it DOESN'T hold the pixels/arc-second constant. That varies linearly with aperture (for constant f-ratio and pixel size). Further confusing things, a larger aperture (all things being equal) will usually be capable of a larger 'flat' FOV in mm at prime focus, yes? What does this say about the cost of the sensor needed to fully utilize larger aperture? Larger sensors are expensive.
Yes! That's a very concise explanation of the problem and how to understand things. I feel that everything gets more expensive as you increase aperture 😅
I want to thank you for validating (and using the same equations) my point to a fellow astronomer almost a year ago. It got pretty heated and devolved into comparing the HST with an 80mm telescope 😂. My take away from research was that “it’s complicated” and any single metric is not really a valid tool across a broad spectrum of devices and configurations. It’s nice to see someone else put pen to paper.
Small bit of constructive criticism. There are several clips where you seem to be editing multiple audio recordings together, but there's little to no gap between the last word in the first audio clip, and the first word in the second audio clip. I would suggest adding anywhere from 1/2 to 1 second of pause between these clips. It makes the audio flow better, and easier to understand.4:58 - 5:01 is one such example
I really appreciate this feedback! I'll keep this in mind for next time. My video editing software can automatically delete the silent parts, and apparently I need to double check when it's deleting too much. Thank you!
Great explanation! I already understood the concepts, I hope it informs others as well. Maybe we should adopt a different metric for image capture performance? How about aperture/pixel size (or aperture area/pixel area for more manageable numbers?
That is an interesting idea! It'd take some thought to get a good metric that's as easy to understand as f-ratio. But maybe, we can figure something out.
Astrophotography is not only about SNR. Resolution is important as well. Maybe even more important, according to Hayes, who spends zillions to buy resolution. Overall, great video!
Very cool video! If I understood you correctly, then this is valid for faint large objects, but not for bright point like sources. Could you explain in two sentences why this is the case?
I can try :) From what I understand, the size of a point source of light (e.g., star) on your sensor is also affected by diffraction (i.,e., light bending). Because aperture determines how much diffraction there is, larger apertures (and faster f-ratios) can detect fainter stars. In other words, the signal from stars depends on f-ratio **and** aperture.
I love how Doctor Detail is supposed to be a bad guy and nemesis of deep sky detail and yet they are also all chill and you get the feeling they are friends behind the scenes. Do I spend time analyzing the lore behind the characters on Deep Sky Detail TH-cam channel? Yes, yes I do.
Thanks! I'm glad you enjoy the lore. I enjoy it too! I agree. I think deep down they all respect each other on and off the set even if they're all spying on each other all the time.😂
@@deepskydetail that would be sweet! i’m in the same boat, im pretty experienced and versed on the DSO aspect. but im trying to transition to planetary work as i’ve moved into bortle 9. i feel like im relearning everything again and there’s not much resources online.
Not a myth so much as a misunderstanding. We have over-complicated the discussion around f-ratio, and I think I know why: it’s because we have things backwards when we discuss telescopes in astrophotography. We should not say 200mm f/5. Instead, we should take a page from conventional photography and put focal length first: 1000mm f/5. I say this because it doesn’t make much sense to compare the “speed” of telescopes with drastically different focal lengths. For example, you would never say that a 3-inch refractor is faster than the Hubble, right? I mean, you could say it but it doesn’t really mean anything. It would be sort of like saying that my lawnmower has better gas mileage than a Lamborghini. It might be true in some manner of speaking, but the comparison is idiotic to begin with. I often hear people talk about using focal reducers to make their telescope faster. But what use is a faster telescope if the focal length is no longer ideal for the targets you want to shoot? Let’s take the example of Hyperstar, which converts SCTs from F/10 to f/2. You should not buy a Hyperstar because you want your SCT to be faster; you should buy it because you want a wider field and smaller image scale. In other words, an SCT with Hyperstar is NOT a “faster” alternative to a conventional SCT. After all, the focal length is four times smaller; it can no longer do what a conventional SCT can do. It IS, however, a faster alternative to, say, a short-focus refractor with a similar focal length to the SCT/Hyperstar combination. If you want a faster version of an 8-inch SCT, for instance, you need something with a similar focal length but a larger aperture. Which is another way of saying, aperture (still) rules. Going back to my original point: when selecting a telescope for AP, we too often arbitrarily decide on the aperture first. “I want a 100mm refractor.” Then we say, “But it needs to be fast for AP, so let’s go with a 100mm f/5.” This is backwards. What we should be doing is deciding on the FOV and image scale we need for the type of targets we want to image. Once we have decided that, the speed of the system is purely a matter of aperture, and is constrained by your budget, your mount, guiding, etc. For example, if you want to shoot at 400mm, you could get a Sky-Watcher Esprit 80 for a speed of f/5. But the Edge HD 800 with Hyperstar will give you the same image scale at f/2. That, to me, is a logical comparison.
Great points! You should definitely ask what our desired FOV should be! I do think we've got things backwards a lot of the time. Thanks for the comment!
Thank you, to everyone who has supported me here, on buymeacoffee or gofundme! If you'd like to support to, check out my buymeacoffee: buymeacoffee.com/deepskydetail
"Sometimes wrong, sometimes right" should be the mantra of astronomy.
Very informative and entertaining video!
I saw someone else ask about planetary, you probably got this but let me know if you want to chat about it. Although I'm not an expert, I've been doing planetary for a long time and I'm happy to share what I know.
Keep it up!
Thanks, Naz! I agree "sometimes right, sometimes wrong" is a great mantra. Once my shoulder is good enough to lift my C8, I'll pick your brain about some planetary stuff ;)
Best explanation I’ve seen on the topic. Hence the importance of increasing pixel size at large focal length
Thank you!
Man I don’t know why you have only 4k subscribers, your channel covers subjects that no other even dreams about. Keep it up.
Thank you!
Great video Mark! Love your deep dives on these subjects!
Thanks, Rich!! :)
Thanks for the video, great explanation! Another factor is that the heavier the telescope, the more difficult it is to drag it to places where the sky is darker.
And if we consider the recognition of achievements by society as a goal of hobby (yeah! old goof battle of egos!), then, for example, it is easier to win an astrophotography competition with image taken on a telephoto lens plus tracker in the Atacama Desert than with a half-meter telescope in the middle of Tokyo. :-)
great points! Thanks for the comment :)
The 'Tri' is size of scope , a suitable mount , a suitable camera.
The 'Force' is what damages your bank account!
That also makes sense. Especially about the bank account 😅
You put a lot of time and effort into these videos. It is appreciated.
Thank you! I appreciate someone appreciating the work put in :)
Also, saw your video of the pier yesterday! It was great!
@@deepskydetail Thanks
Excellent video!! I saw some of the other recent f ratio myth videos and had a number of items that bugged me about them. Very glad you made this video!!
Thank you!! It's so easy to get confused about signal. I'm glad you enjoyed it :)
I like the video. Your deep dives are amazing. Makes me wonder if......... ahhh, never mind. Great video!
Thank you :) And you are correct, I am secretly a master of the universe working out of Castle Grayskull!
When I make a final result from a stack of images I want the subject to be BIG. It's no use having a nice, bright, noiseless, subject if it is tiny. So all the theory breaks down when the starting assumption is to produce an image where the subject takes up (say) half the final field without appearing pixelated.
In practice, most people recognise the constraints placed upon them by the equipment they already have and the amount of LP that reduces their signal/noise ratio,and choose their targets accordingly.
Oh, I definitely agree. SNR is not the only thing that matters. I would definitely trade SNR for resolution when imaging a far away galaxy for example! I wouldn't say that the theory breaks down though. The "triforce" is just as much about resolution as it is for SNR/signal :)
I think the key issue that most people miss (including me), is that while constant f ratio keeps the photons/pixel constant, it DOESN'T hold the pixels/arc-second constant. That varies linearly with aperture (for constant f-ratio and pixel size). Further confusing things, a larger aperture (all things being equal) will usually be capable of a larger 'flat' FOV in mm at prime focus, yes? What does this say about the cost of the sensor needed to fully utilize larger aperture? Larger sensors are expensive.
Yes! That's a very concise explanation of the problem and how to understand things. I feel that everything gets more expensive as you increase aperture 😅
I want to thank you for validating (and using the same equations) my point to a fellow astronomer almost a year ago. It got pretty heated and devolved into comparing the HST with an 80mm telescope 😂. My take away from research was that “it’s complicated” and any single metric is not really a valid tool across a broad spectrum of devices and configurations. It’s nice to see someone else put pen to paper.
Wow! Great info. You just saved me from wasting thousands of €s 🙈 Thanks!
Fantastic video as usual!
Thank you!
Small bit of constructive criticism. There are several clips where you seem to be editing multiple audio recordings together, but there's little to no gap between the last word in the first audio clip, and the first word in the second audio clip. I would suggest adding anywhere from 1/2 to 1 second of pause between these clips. It makes the audio flow better, and easier to understand.4:58 - 5:01 is one such example
I really appreciate this feedback! I'll keep this in mind for next time. My video editing software can automatically delete the silent parts, and apparently I need to double check when it's deleting too much. Thank you!
Great explanation! I already understood the concepts, I hope it informs others as well.
Maybe we should adopt a different metric for image capture performance? How about aperture/pixel size (or aperture area/pixel area for more manageable numbers?
That is an interesting idea! It'd take some thought to get a good metric that's as easy to understand as f-ratio. But maybe, we can figure something out.
Thanks for making this great video!
Thank you! Glad you enjoyed it!
Astrophotography is not only about SNR. Resolution is important as well. Maybe even more important, according to Hayes, who spends zillions to buy resolution.
Overall, great video!
Thanks! I agree that resolution is really important, and the triforce of signal could also be called the triforce of resolution :) 22:51
@@deepskydetail What scope do you have?
Very cool video! If I understood you correctly, then this is valid for faint large objects, but not for bright point like sources. Could you explain in two sentences why this is the case?
I can try :) From what I understand, the size of a point source of light (e.g., star) on your sensor is also affected by diffraction (i.,e., light bending). Because aperture determines how much diffraction there is, larger apertures (and faster f-ratios) can detect fainter stars. In other words, the signal from stars depends on f-ratio **and** aperture.
Excellent OoT reference.
Thank you! :)
Ok, so have to get big aperture and big sensor.
I love how Doctor Detail is supposed to be a bad guy and nemesis of deep sky detail and yet they are also all chill and you get the feeling they are friends behind the scenes.
Do I spend time analyzing the lore behind the characters on Deep Sky Detail TH-cam channel? Yes, yes I do.
Thanks! I'm glad you enjoy the lore. I enjoy it too! I agree. I think deep down they all respect each other on and off the set even if they're all spying on each other all the time.😂
@@deepskydetail Frenemies perhaps 😉
The larger your diameter the smaller your stars are for a given f ratio. This because resolving power is aperture dependent.
Yes, good point!
do a planetary astrophotography one. next
I can try! I do planetary, but I'm not as well experienced with it as DSO stuff. So, I'll have to do some research ;)
@@deepskydetail that would be sweet! i’m in the same boat, im pretty experienced and versed on the DSO aspect. but im trying to transition to planetary work as i’ve moved into bortle 9. i feel like im relearning everything again and there’s not much resources online.
Not a myth so much as a misunderstanding. We have over-complicated the discussion around f-ratio, and I think I know why: it’s because we have things backwards when we discuss telescopes in astrophotography.
We should not say 200mm f/5. Instead, we should take a page from conventional photography and put focal length first: 1000mm f/5. I say this because it doesn’t make much sense to compare the “speed” of telescopes with drastically different focal lengths. For example, you would never say that a 3-inch refractor is faster than the Hubble, right? I mean, you could say it but it doesn’t really mean anything. It would be sort of like saying that my lawnmower has better gas mileage than a Lamborghini. It might be true in some manner of speaking, but the comparison is idiotic to begin with.
I often hear people talk about using focal reducers to make their telescope faster. But what use is a faster telescope if the focal length is no longer ideal for the targets you want to shoot? Let’s take the example of Hyperstar, which converts SCTs from F/10 to f/2. You should not buy a Hyperstar because you want your SCT to be faster; you should buy it because you want a wider field and smaller image scale. In other words, an SCT with Hyperstar is NOT a “faster” alternative to a conventional SCT. After all, the focal length is four times smaller; it can no longer do what a conventional SCT can do. It IS, however, a faster alternative to, say, a short-focus refractor with a similar focal length to the SCT/Hyperstar combination. If you want a faster version of an 8-inch SCT, for instance, you need something with a similar focal length but a larger aperture. Which is another way of saying, aperture (still) rules.
Going back to my original point: when selecting a telescope for AP, we too often arbitrarily decide on the aperture first. “I want a 100mm refractor.” Then we say, “But it needs to be fast for AP, so let’s go with a 100mm f/5.” This is backwards. What we should be doing is deciding on the FOV and image scale we need for the type of targets we want to image. Once we have decided that, the speed of the system is purely a matter of aperture, and is constrained by your budget, your mount, guiding, etc. For example, if you want to shoot at 400mm, you could get a Sky-Watcher Esprit 80 for a speed of f/5. But the Edge HD 800 with Hyperstar will give you the same image scale at f/2. That, to me, is a logical comparison.
Great points! You should definitely ask what our desired FOV should be! I do think we've got things backwards a lot of the time. Thanks for the comment!
Is aperture king? Yes. /end video
06:50 😉
6:23
Wow..... make a simple concept difficult.
I'm all for constructive criticism. If you have something more specific you'd like to say, please share.