vlaiv

well, don't use reducer. I was also going to ask - why limit to 1000mm. That is not galaxy FL with APS-C sized sensor. Most galaxies are small enough to fit central 1/5th of sensor or there about at 1000mm. There will be a lot of sensor "wasted" on surrounding space. 2000mm is quite decent FL - and you don't need reducer for galaxies - again same reason - even without one, there will be still plenty of surrounding space captured for context.

Only if there is no bias. If there is bias of some sorts - with increased number of people guessing - you'll be closer to real value + bias rather than real value. Imagine following scenario - jar is twice as large - but you can't see it as it is not sitting flush on the desk - it is "embedded" in the desk, however, labels on the jar are positioned so that they fool people - so it looks like complete jar is sitting on the desk. People will make their guesses like they see regular jar, and compared to regular jar - average of their guesses will tend to the same value - but in reality, first jar holds twice as much cookies as the second jar (regular one). We introduced bias in the mix purposely. People won't suddenly start to give different random answers to account for that what can't be seen, right?

I think it has more to do with lack of color calibration of astronomy cameras rather than anything else. If you don't color calibrate instrument - it will have a bias toward the most sensitive part of spectrum - and if you look at QE curves of sensors they peak around 500-550nm in green region. For this reason raw R, G and B data - which is not true RGB of any particular RGB color space, will have that bias. People then "white balance" - which is wrong name and procedure to correct the problem, and if they don't do it - there is strong green cast - which they then want to remove as "there is no green in space" (even that is not completely true). In any case - doing that on false color images completely makes no sense (even if it does not make sense to begin with as it is wrong way to go about it).

And that is how you seriously approach mathematical problem On a serious note - I think that above approach relies on ability of average person to guess "on average" the right number of things in the jar. Its a bit like astronomy imaging and stacking - if you have enough samples with random error - average of those samples will give you best SNR value - or best value with lowest error - but it depends on two criteria. 1) - error being random 2) - guess on average being right condition 1 is generally satisfied when people start to guess and there is a lot of them - but condition two might not be - and then you have a bias. If jar is such that it always leads to over estimating how many items are in it - your average will over estimate exact value and vice verse - if some condition causes under estimation - so will average. Even "silly" things like - asking everyone while they are hungry can lead to over estimation (if cookies are in the jar ).

Two things happen here. First is that people use what is known as HST palette (or SHO) for narrowband images of some targets - or maybe bi color palette. When you shoot narrowband images - you get monochromatic images per element (like Ha, OIII and SII). Both Ha and SII are deep red - and would not differentiate in the image - so they are assigned different base colors and what you see is combination of these colors. here is classic example of HST/SHO palette - where hydrogen is mapped to green, oxygen to blue and sulfur onto red (SHO = SII, Ha, OIII = RGB) Other thing that happens that might confuse you is "artistic license" that people give them selves in processing which often leads to generally inaccurate color of celestial objects. Monkey's head image that you saw is probably either bi-color composition (Ha + OIII) or inaccurate use of SHO/HST type palette where people try to do SHO but end up "killing green" for some reason for the image - probably "because it looks better" that way.

Why is that? I was going to recommend EdgeHD 8" as potential candidate - but since you have one, what makes it unsuitable?

Still not sure where the problem is? If I understand correctly, you have following: Canon EOS - to M48 and M48 to T2 that is total of 15.5, right? How much path is each component? Then you have Filter wheel that is 20.87mm thick with T2 thread on each end right? Finally you have ASI183 with 2" removed which leaves T2 thread that goes into filter wheel - and that makes 6.5mm only to sensor (from camera front to sensor). Why would you want to use above adapter when everything fits properly one to another (above adapter seems to be some sort of male M48 to male T2 thread or similar)? Instead of using it - you can simply add 3x0.5 spacers somewhere in your train. Maybe use 0.5mm one in front of filter wheel and 1mm between filter wheel and camera? https://www.firstlightoptics.com/adapters/baader-t2-delrin-spacer-ring-set.html Or is that adapter needed for "first leg" of the train - Canon EOS + M48 to T2 and you need to shorten the optical path?

I think it would be better if you describe whole train and required spacing. Shaving 0.5mm of something that is already very thin is going to be tall order. Most adapters don't list thickness of such feature so you can't be sure in advance if it will help or not. It is probably better idea to look at the whole thing and see if you can save some length in different place - even if it is greater than 0.5mm - it is easier to add extension or shim then it is to reduce length.

For one - I'm not claiming that it is different - but to me, it certainly is plausible that it is different. Here is one thing that I've noticed people differ in. Some people are quite capable of abstract thought while others are not so. Last night I was discussing existence with a friend over a pint (as you do) and we came to the conclusion that he has real difficulty imaging nothingness - in general sense - like when you start to build imaginary universe and wonder at what point you can say that there is existence. That is highly abstract notion and I understand that he has difficulty grasping it. I've also noticed that some people have difficulty with abstractions in mathematics or in general. This ought to show us that we don't have as similar consciousness as we might think at first. Here is another example. When I was in high school sometimes I played "mental chess" with a friend of mine on a way back from school. He was truly gifted chess player (not sure if he is still active chess player) and he had no trouble playing prolonged matches whilst keeping complete board and situation in his head. I really struggled to do so - although I'm quite good at visualizing things in my mind. I could never have "current" state of board in my mind - but had to resort to tricks like keeping list of last moves and checking next moves against that or whatever - and I often made mistakes.

@EarthLife I'd give you like gazillion likes for posting that video I was not aware that there is period in human development where we become aware that others have mind as well.

Ok, so I might be coming from totally different perspective into this and this might be a problem - but I'll explain the way I see it. Computer neural networks are based on actual thing, so we can say that they are abstraction mimicking the real thing to a degree. Maybe not all the intricacies but if something holds for artificial neural networks - I think it will hold for real brain as well - at least things that I will mention. If we take a neural network and break connection between neurons A and B - neural network will start giving different output for the same input even if what the network "has learned" is the same. We can see this in serious injury to the brain where individuals must re learn certain skills - like learning to talk / walk and so on again (these are extreme cases). This is what I mean by wiring of the brain. As far as I can tell (but I'm not 100% certain on this) - pathways or connections between neurons form in early age and part of learning. This is different from artificial neural networks which are mostly "fixed" - e.i. count of neurons and their connections remains the same ("no rewiring"). Given above and from the fact that we all have different DNA - it is very sensible to assume that: a) two individuals might not have same number of neurons b) two individuals might not have same number of connections or differently arranged connections between existing neurons Now, it is possible for two networks with different architectures to be trained the same and to roughly have the same response - but it will never be exactly the same. From this it is easy to see that even if we have very similar / "the same" structure of eyeball, photosensitive area, optical nerve and so on and we get the same electrical impulse to the brain - first neural network / processing center will be different because it will likely have: a) different number of neurons b) with different connections c) and different training Ok - so this is very hard to explain - and for precisely that reason it is hard to establish if we have the same perception or not. Let's try with green: there is nothing in physical phenomena of color that is green. Green does not exist in physical world - it is our sensation. It is sort of a feeling in our brain that we get when we see object or light that is green. People that have suffered some severe trauma sometimes smell colors. Their brain is rewired differently in such way that when they see green for example - they "smell" or have sensation or feeling inside of their brain of some smell. By the way - smell is also very similar to color - in the sense that we have this perception in our brain of something - and as we have seen this perception is triggered by certain signal from processing center of our sense (which can get mixed up). That is what I mean by perception - thing that happens in my consciousness when green light triggers my sensory system - a feeling. There is simply no way of telling if I have same green feeling as someone else. Maybe my green feels like your roasted pork (either smell or taste) - but we would never know that because all we have in order to communicate that to one another is just comparison between physical stimuli and corresponding feeling that each one has but can't express.

Interpretation is the same. But we can't say that about perception. What I see as RED - I will associate with warmth and danger and arousal and all those nice things that nature took care that I associate it with. That is interpretation. In fact - my mind is not doing the association - my "body" is. Here is interesting question: at what stage do color blind people fail to differentiate red and green? Or to put it in another words - would people with particular type of color blindness see green as threat?

You see what you did there with showing me that color: you said to me - look at this, once your brain matches any color to this particular one - you need to yell acid. You might have as well told me that it is called superluminal green.

Same neural network can be trained differently and produce different output for same input. That is how we learn and remember. Even if "schematics" (number of neurons and their connections) of neural network is the same, and even that is different in different people, result of certain stimulus will be different. Optical nerve can deliver same electrical impulse to "processing" network - but that network might output totally different signal for same stimulus in different people.

Very true - pain threshold is again something to consider when speaking about matching part. We sometimes can't even match things between us and in certain cases not even on individual level. Depending on state of mind and body chemistry - sometimes we can find certain stimulus pleasant and sometimes unpleasant. So stimulus itself is not solely responsible for response it creates - there is also state of observer. Given that one observer can be in different states - it is not very hard to imagine that different observers will be in different states.

I wonder how similar / different would be certain parts of the brain? Number of neurons and their connections ....

This is beautiful example of how perception can be different in different individuals. We know that all senses end up as being electrical impulses in our brain, right? Why does one produce color, other smell and third note of certain pitch? They are all just electrical impulses at the moment they "enter" our brain, right? It is the brain and structure of the brain that determines what each electrical impulse will be felt like. Now, we, in general, have very similar brain structure - but there is enough differences to raise question if what we experience is also different. Different people do have different wiring in their brain. Chess player will have different wiring in their brain compared to say rock climber or precision optician (our brain rewires itself to some extend based on our experience - that is how we learn and acquire skills).

Not sure that it is - I'd associate it with discomfort rather than color of lemons and limes. But in either case - we associate it with something - but no way of transferring information of how that actually feels.

Say for example that I don't understand what acid green means (and to be honest, I'm not entirely sure I do). How would you explain it to me? Try to give me explanation of what the acid green looks like without showing me actual color.

Yes. Best we can do is "match" - but we can't determine that they are equal in sensory sense. If I show you two pieces of red paper - we will both agree that it is the same color and we will name it the same - red. But there is no way to assert if our perception of that color is the same. Similarly - if we play two notes on a piano - we can say that they are the same (or different and in what sense different - like higher pitch) - but no way to assert if we are "hearing" the same note (here hearing means our perception of the note). All the properties that we assign to color or note will match - but there is also no way of saying if we actually see / hear the same thing. Take "warmth" for example. Blue is cold color and red is warm color. Nothing about cold or warm is related to perception of color - it is rather related to matching of colors. We say that red is warm because fire is red and sunshine is (reddish - on sunset for example), while blue is water and ice and thus is associated with cold. We just took names of perception phenomena (we similarly can't say if we experience cold or warmth in the same way) and made a relation between them.

Here is counter argument. What about 540nm wavelength light is green? What property does 540nm photon have that is different from 686nm photon - except for wavelength / energy? There is nothing in the wavelength or energy itself that would determine what color should be perceived as. Why do we "perceive" one as green and other as red? Where does the color come from? Did the universe create it for us or is it just sensory artifact? Could time passage be also sensory artifact of sorts? We never touch anything, but we all have firm (pun?) idea that we touch things. Things that we perceive as solid are in fact mostly empty space and all that anyone ever felt is electromagnetic repulsion. Yet we seem to be mesmerized and very amused when holding two magnets that repel each other. We find it very interesting as it is "action at a distance" that seems so strange to us. Again - sensory artifact. We needed to invent tools that would paint us real picture of what the matter really is. Maybe we need to develop tools to understand that time really is, not what we sense it as?

Here is an interesting idea. If there is no time - then there is no sense in asking - what came before - as there is no before / after - those are concepts that stem from concept of time. There is strong indication that time is nothing but illusion. Most of it comes from relativity. Fact that it is flexible and that it is sort of related to spatial dimensions creating space time is one indication. Simultaneity of events - or rather it being tied to observer is another strong indication. There are observers that have their "now" aligned to our past and observers that have their "now" aligned to our future. Combine that with quantum mechanics and entanglement and you get very interesting situation. We usually think that measurement in one place determines state in different place. Say that we measure spin of electrons - and measuring one will determine spin of the other, right? But what measurement was made first? That depends on frame of reference. We can either talk about hidden variables or accept that order of events does not really matter - no causality - or no time. Then there is fact that all fundamental laws of physics are time reversible, yet time seems to flow in one direction. Maybe we are asking the wrong questions?

Well - that is the meaning of intrinsically unknowable - you can't know it even in principle. If universe is defined as "everything there is", and something existed that created it - that something: a) must not exist any more - or it must be part of this universe and hence could not have created it b) has no connection to this universe (see a - as any "connection" can't be current connection). If there are any "artifacts" present in this universe that tell us about what created it - it will not tell us enough to be able to distinguish it from all other things that would leave the same artifacts. Besides those artifacts - all the rest about what created universe is simply unknowable. Then there is issue of time. Concept of creation is tied to time - or very simple version of time - one that is just sequence of events without necessarily assigning ratio of sorts (something is "twice as old" as something else - it is enough to know what came prior to something else), but if time existed outside of the scope of our universe - then what "contains" time and how it came into being? You see - if something caused our universe to come into existence - it must have happened before - and that implies existence of at least basic order of events - or time.

Philosophy tries to deal with some of it by asking questions like - how much can we know? / is there limit to the knowledge? How can we be certain that some knowledge is true and so on. For example - can anyone be sure that sun will rise tomorrow? Something all take for granted - but there is no guarantee of that. Similarly - if we performed experiment N times - there simply is no 100% guarantee that it will behave the same N+1. Some say that by doing things more times - we build confidence that it will happen in the same way - but there simply no way of being certain about it.

How is that any different than saying something like: In the beginning there was the Big Bang and everything we know "came into existence". How did it happen? Well, that is beyond of our realm to understand / probe / know. It is intrinsically unknowable.