Whirlwind

I think this is a bit of a disingenuous comment - no one is stating "just stay with CCD", it hasn't even been mentioned - this is about whether to consider that for the purpose of the usage (ie. high usage at a remote site) that obtaining a version of the same CMOS sensor in its industrial form is a better option than a consumer version because the manufacturer stands by it having a longer lifespan before it fails. Whether CCD or CMOS it is better to have all the evidence so individuals can make a judgement as to whether the risk is acceptable. That some of the chips have a restricted usage is a valid concern where the camera may be used over a longer period and beyond the recommendations of the manufacturer. By being aware of the risk you can both ask further questions and interrogate whether the level of risk is acceptable for the activity you are intending to use it for. The alternative is that we don't say anything, not mention it and if the worse did happen shrug your shoulders and think "well I knew that, but I couldn't be bothered to mention it" (or worse "I'll just be shot down for saying it")? How does that foster a positive astronomy community if the immediate reaction is to attack any person that might be highlighting a potential risk for consideration?

This is true but, they tend not to be used aggressively by consumers who likely only take a relatively short number of shots a year. In addition they are usually in high light conditions so exposures are in thousandths of seconds with less stress (no active cooling etc). As such 300 hours of photos is a lot.... On the other hand for astro imaging at a remote site wouldn't take that long in a year to get to 300 hours. Now 300 hours is only what Sony guarantee. They won't necessarily fail at this point but the company will have made a judgement as to the probability of any one failing before this point and whether it is replaced under warranty. We also don't know the distribution of the failures. It may well be that if you take 600 hours per year of images then 50% will fail or it might be 1600 hours per year, this will be internal knowledge only available to Sony. However, it is worth recognising a potential risk especially when you are looking at a £4000+ camera. I can't say I don't worry that in a couple of years we will start to see increased numbers of cameras 'failing' - but we may not be there yet as CMOS is still relatively young as a product in astroimaging.

I don't think the issue is between grade 1 and grade 2 in the way CCD sensors operated (which I'd be quite happy to say isn't a problem for astroimaging). There is generally little consumer information about the differences but I do note this on Astrographs site:- "Similar to area scan sensors, images produced by consumer grade sensors, provide a fast, high-resolution capture of the entire field of view. The main difference between them and industrial grade ones is that consumer sensors have a shorter life span, a shorter mean time before failure (MTBF) and, as a result, may cost much less than an equivalent industrial grade sensor. If you have a product that needs to be guaranteed for a long time, have a consistent image between each vision product, or if you need it to last for several years versus just one year you will want to consider an industrial area sensor instead. If you are purchasing hundreds of thousands of sensors per year and you have satisfied the other requirements, then consumer sensors may be the right choice for your application" (QHY600M - Why? (astrograph.net)) This principle would align with Sony placing an hours per use limit on consumer grade sensors (basically if it fails and you've exceeded this usage then there is no warranty on the chip etc). For the majority where you get few decent nights per year in the UK this limitation is unlikely to occur (barring some spectacular weather) before any natural/extended warranty expires. However at a remote site where you are imaging night after night it is definitely a consideration as you wouldn't want a chip of this cost to completely fail in a (relatively) short period of time (which Sony to an extent are artificially extending by limiting the usage per year) when the old CCD is rolling along nicely (despite some cosmetic defects).

Given the amount of time you are likely to image you may want to check what grade of sensor you get in the Atik. I've seen QHY have provided two versions before but also note Moravian now offer this sensor (plus the 2600MM equivalent) and note this on their website (C3 Series CMOS Cameras (gxccd.com)):- Assuming there is nothing untoward in the advertising here - any long term imaging at a remote observatory may well be worth considering the industrial grade as I assume that any operation above 300 hours may void the warranty if it goes bad (in effect more than 30 nights assuming 10 hours per night but excluding darks and flats). That Sony have to limit it in this way does make me slightly wary on the longevity where people get lots of clear nights (hardly ever likely in the UK mind!)

The FLT91 is only just out so there are unlikely to be many real world users out there just yet. Nevertheless in theory it does guarantee a certain quality of lens (and you can ask for a report at an extra cost - which might incentivise to be given a better one, especially as an earlier adopter). In terms of practical use I always found their more integrated flattener/telescopes more easier to use - especially the variable adapters which gives a bit more scope to play with back focus. I also think a lot of the earlier mechanical issues are now resolved (poor focusers etc). They probably are going to be much of a muchness with many similar triplets which are either from the countries of China (Skywatcher) or Taiwan (WO). I tend to steer towards the latter (or Vixen/Tak being Japan based) but that's more of my own personal political sensitivities.

I think this might all depend on what you prefer to image. If it is nebulae / clusters etc then a wider field is better and would look at the FSQ85/106 with your camera. If you prefer galaxy imaging then you probably want a longer focal instrument and something like the TSA120 / TOA130. You can also get reducers for these to help with imaging nebulae. Honestly I would have though the TOA130 (with an focuser upgrade) would be the lifetime scope because there is unlikely to be anything really better that would be noticeable.

The difference is how it is being interpreted. You are using it as evidence that it does exist. The papers demonstrate that mathematically the laws we have in place cannot differentiate between the two possibilities. Therefore this suggests that there may be something about the laws that needs to be refined. The observations suggest that there is no difference in whether you look left or right. Whether that is experiments that measure radiation pressure, to spectrum of emissions and so forth. Mathematical formulations are just a different way of describing the same principle but it doesn't change fundamental parameters. We know Newton's theory was wrong from measurable evidence (e.g. Mercury's orbit) whereas relativity does resolve this and we continue to test it all the time. We know something is 'wrong' as we can't combine relativity with quantum mechanics but observationally both fit the theories. This is why we test ever more refined experiments (e.g. CERN, gravitational wave detectors). What we didn't do when we had a problem with Newton's laws was to arbitrarily adjust some of the parameters to make things 'fit' to the observations. We could have done this but we would not understand the universe any better (and in fact science would stagnate). This is why just arguing that you could adjust the factors in an equation between c and frequency isn't sound. It's in no way testable, has no physical rationale behind it and drives us down a dead end. As I said before this is the approach we took when we assumed the Earth was the centre of the universe. We devised ever more elaborate ways to explain the patterns of the orbits but with no physical reality behind it. It failed because it could not predict the next object found.

That's not what we are saying at all. What is being said is that the approach you are taking to justify the rationale is the same principle used by people to justify the earth is flat (and also the same approach to make the Earth the centre of the cosmos hundreds of years ago). What you are doing is taking a principle and trying to use reasons to justify the empirical evidence which is the same approach. In effect what you are doing is trying to prove the principle correct, whereas science is about trying to prove your theory incorrect. Any theory can be *potentially* correct but it has to be testable (and not just altered to fit what we observe). The paper referred to doesn't claim that c varies in different direction it just claims that it in principle special relativity doesn't prevent this from occurring. That isn't *proof* that it actually is. To do that the theory must be testable observationally that would differentiate the two possibilities. You have to prove that why the hydrogen alpha line looks the same regardless of which side of the sun we are on and be able to explain not just the why the frequency has stayed the same but why all the observational physical processes we see (down to basic experiments like a double slit experiment can be explained. Energy levels are also a fundamental of Quantum mechanics. If you change energy levels then the way objects would bond, interact and their forces would change (molecules might be more or less tightly bound for example). Such changes to interactions would be observable.

Yet this is exactly the problem. You are just claiming that you can do this without any empirical evidence. We can all do this, as noted before I can likely come up with some reasoning as to why stars are actually glowing marshmallows on the other side of the galaxy. It sounds unrealistic but I can just keep coming up with ever odd reasons for any argument against the idea but not put forward any way of testing that idea. It is not scientific method to respond to a criticism of theory by inventing something else to explain the criticism away. For example at a basic level, if you change c in different directions then the energy conversion between mass and photons changes in different directions. If energy changes then the quantisation of energy changes which in different directions means that frequencies change for the same energy levels. As such hydrogen alpha emission/absorption should be different in different directions. This is simple to measure from a spectrograph. If energy quantisation levels change then the way that gases act in high g environments changes - and we have standard candles for these sort of things (White Dwarfs). All of these observations would be slightly out in one direction to another if c is different in different directions. Just because c = fλ does not mean you can fiddle with c and not have a consequences across a vast number of other fields. If you don't produce a testable theory then the proposal is not better than a 'flat earth' theory because the same principles used by some to try and explain a flat earth are being used here. How about another argument against this relating to GPS satellites. If you stand on the surface and look to one horizon then a GPS would transmit its signal at one speed and then as it travels across you horizon then it would be transmitting in the opposite direction so c would be different. The 'clock' has not changed only the direction. Any change in c would be noticeable as you would then see a slight shift in position - so the question is why don't we see this as a changing c should result in a relatively circular and consistent pattern of location changes despite the object being 'bolted' to the ground.

I'm sorry but this argument simply isn't science. You can create any number of arguments to argue against the evidence to hand (e.g. the spectroscopy doesn't work because you change frequency / length) and hence you end up with increasing divergence of physics just to 'prove' that a theory could be correct. This is the same as saying that all stars on the other side of the galaxy are made of bright glowing marshmallows because of any number of concoctions that can be thought up. It *could* be possible, because we can't physically check but all evidence suggests that it is not the case and hence an experiment that distinguishes the two possibilities. To argue your case you need to provide a test that would definitively test or disprove the arguments that are brought forward. You have two here - one that spectroscopy measures wavelength/frequency which are related to c; the second that lasers would not work in the way they do if c changed in different directions. You now have to put forward tests that break these experiments but at the same time still allow c to change in different directions. Otherwise we will just go round and round.

The standard back focus from the Vixen reducers is 63.5mm (confirmed here Vixen FL55SS fluorite apochromat with Flattener HD and Reducer HD (skypoint.it)). If you are just using the flattener then you get an extension with the HD Reducer set which is 76mm long (Vixen Flattener HD Kit for FL55SS | Vixen) so given the threads that would give about 130mm to play with when just using the flattener. When considering attachments the M60 adapter is less common to find. Vixen producer a 'rotator' that also converts to a standard t thread thought TS optics also do some other adapters to M68 and M48 I believe.

Yes, sorry I had seen your comment. I was trying to produce an experiment that could be tested without the need for measuring the actual wavelength/frequency directly and have something that would fundamentally 'break' without measurement if the speed of light was different in various directions (in this case the excited atom).

The problem with articles like this are that they are only really pseudoscience. They postulate something but provide no tests to prove it is incorrect. I would however propose that lasers can disprove this postulation. Firstly lasers are based on exciting atoms and using mirrors the same wavelength/frequency of light to de-excite the atoms in a controlled way. The atoms have specific energy levels because the electrons can only maintain certain energy levels. As a laser can use a mirror to induce this then the light will be travelling in different directions and hence the assumption would be it would be faster/slower in one direction. However, wavelength and frequency are linked, so a change in the speed of light would change the frequency/wavelength of the light. So what you should see over longer distances is a divergence and splitting of spectroscopic observations in one direction compared to the other (which is a lot easier to do than in white light because we are talking about specific discrete frequencies). Over long distances this should be measurable. In addition as the energy of the light would be different in the two directions then only in one direction would the interaction between the atoms and the light be most efficient (as the atoms have discrete energy levels). As such the flux of the laser would be different in the two directions (as one direction has induces energy changes better than another).

As an alternative how about a colour APS-C CCD instead which come up relatively frequently e.g. U.K. Astronomy Buy & Sell (astrobuysell.com - (I have no links to seller!) This gets you a colour APS-C camera for about a halve-third of the cost of a new 2600. For someone that is just jumping into CCD/CMOS then this might be a more cost effective option and allows you to test the water. The pixel size is more appropriate for longer focal lengths as well and was a type of camera that has been a work horse for years. There's also a mono for the same price (if you changed your mind on this as I think this is more future proof and the saving does then let you spend on filter wheels/filters etc).

Transport costs are unlikely to fall anytime in the future. There are bigger dynamic changes occurring in the wider market. One of the large factors for increased shipping costs is due to waste changes. A couple of years ago a lot of waste for recycling went to China but it has increasingly closed its doors to most waste (barring metals). Shipping use to be able to offset costs partially through having ships full for both journeys (you ship the goods one way and the waste the other way). With much less waste going to China a significant fraction of ships are going back empty. As such the shipping costs have almost doubled (as you pay to ship the product and then pay to move the ship back empty). It's not really a pandemic issue either.

Yes but that is balanced by that the retailer in the EU doesn't charge VAT when you buy the product (unless it is under £140ish). As such the price you pay should exclude VAT at the checkout (and VAT varies across the EU). That can balance out to lower costs overall depending on the product (this can be especially true if the supplier/distributer of any product is EU based). The bigger problem is that a lot of retailers won't sell to the UK because the mess that the customs set up is in.

Well they are 'achievable' but you do need the correct set up. Firstly you need a reflector, many refractors aren't well corrected in the near UV. Secondly many commercial CCDs aren't that sensitive in the near UV (CMOS can have advantage here). The issue of attenuation has already been noted but you can still get some signal. However you also need to think about the stars you will observe. Objects bright in U or B are very hot and hence conversely few and far between relatively. Many stars will not be that bright in U and B. As such you need to make sure you have a large aperture to be able use these type of filters. If you are just starting out V is definitely the way to go as you will get the most out of it and then you can diverge from there.

I believe this is a function of the architecture of the DSLR. This DSLR uses CMOS so each each row is read out using a different set of electronics. As such each row has a slightly different read noise associated with it. This is generally not a problem when you have plenty of signal. In day time use it won't be noticed and you probably didn't notice it when it was unfiltered because of general background noise (light pollution etc). Now you have a narrowband filter most of the background is removed so this underlying pattern is exposed. It is much better controlled on CMOS astronomy cameras because they are cooled and have been designed to control this as much as possible - something that DSLR camera manufacturers give less consideration to (as they aren't designed for only astro work). The solution is to dither by several pixels (slightly move the cameras pointing) each time you image. This will mean that the location of the bands will be different on each image of the object. If you take enough and then average/median combine the images the effect will be removed as you have averaged out across the final image. Most imagers regardless of camera dither as it allows you to remove stubborn artefacts that processing can sometimes struggle to remove.

It depends on what you want to do. AAVSO prefer to have calibrated results so they can compare to all other results. However, if you are doing things for your personal interest then you don't need to have a V filter to do photometry. In fact a Lum/clear filter is just fine, that will show up variability in some ways better than a V filter as you are allowing more light in. In the astrophysics world different colour filters are used to infer spectral types of objects or how to classify any variability. For example the depth of an eclipse in a binary will be different with different filters because each star will have its own temperature (barring two similar temperature stars). On the other hand planet eclipses will be the same depth in any band - in this case because of the shallow depths more flux (i.e. no filters is better). So don't think you have to have specialist filters to do photometry.

At a simple level there are two types of noise, systematic and random. It is correct to state that systematic noise can be removed (such as using dark frames). However, this assumes that the systematic noise is completely predictable. In some cases this is not the case and is effectively 'chaotic' (in that there are some many individual components that it is impossible to predict them all accurately - this does not make it random however. Bias is a good example for CMOS - this isn't random noise but it could be considered systematic, chaotic noise. Hence you don't calibrate out the bias because it is not predictable. As noted there are other ways to proxy removing this noise so that you are only removing a stable signal. This is why for CMOS you can get more commonly fixed pattern (walking floor) noise and for CCD you can get bad pixels that don't calibrate out completely (and need other tools, e.g. dithering). For CCDs fixed pattern noise is more limited to individual pixels so to an extent are easier to remove with just a few images and a bit of dithering and processing. For CMOS as noted before every pixel has a source of systematic, but chaotic noise that generally requires more aggressive dithering (this is due to electronics being on each individual pixel) but as it is prevalent on every pixel (although improving in how much of it is there is). In effect what you end up doing is 'smudging' this fixed systematic noise across the image. As it is everywhere this effectively averages out this noise source across the image. Although you then subtract off this average noise off it does result in a residual memory of that noise (as no one pixel is fully corrected for the noise because the correction is an average of the error). For general astroimaging this is generally not a problem (as you just image for longer) and subsequently in the processing there is a floor which below is given a value of 0 (so you cut out this noise). However where each exposure is important (rather than the combined image) then this type of systematic noise can lead to problems (especially for faint objects). I agree that the spectroscopy/photometry are not important to most on the forum, I did not state otherwise, but the OP asked about the relative merits of getting a SX834 compared to a 2600MC so hence the intent was to provide a balanced consideration of the merits of going for the SX834 and its relative advantages.

So noise can arise in several forms. Some are completely random and others are not. Ultimately all you want remaining in an image is truly random noise as when you combine data these errors will balance out. For example read noise is a fixed source, random noise is a natural consequence that you never measure something exactly. So if your true value was 0 and you observed 5 images of the same pixel then you might get -2.-1,0,1,2, which averages out to a value of 0. Calibration frames take out the things like dark noise (for example) but you are still relying on the measurement of any individual measurement of this value to be truly random - so you want your dark frame images to be 198,199,200,201,202. These will average to a value of 200 and subtract away from your image. On the other hand if the fluctuations are not truly random and has an underlying additive or subtractive element that is different to that when you take your images then you end up adding a fixed noise back into your image. Because of the design of CMOS (each pixel has its own electronics) then you can end up residual fixed noise that is difficult to remove and in some cases isn't stable (for example biases are not generally taken with CMOS cameras because it can be unstable at short exposures). There are different ways to approach this. For CMOS it is common to aggressively dither to average out the fixed pattern noise that they can generate. Even for CCDs it can be worthwhile to dither to remove some hot pixels that can not be managed through darks. However these tend to be relatively isolated whereas for CMOS the effect occurs across the chip. For images it is perfectly OK to have some residual noise if you can dither it out. You just expose a bit longer (or more images) to beat the noise. For photometry / spectroscopy where generally you want to aggressively avoid placing objects in different locations and you want each image to be close to perfect as possible, ideally you want pixels that respond the same all the time. Hence for a CCD after you have calibrated you generally have a floor value for each pixel that it will to a reasonable approximation randomly vary around. For CMOS with for example aggressive dithering you tend to have both a naturally varying signal plus a background value that has been averaged out over many images (and hence the floor value is just that bit higher because average of the noise has been added to all your images). Hence CCDs tend to calibrate better from a noise perspective and at the moment are more useful work such as photometry and spectroscopy. Although CMOS technology is advancing and it might not always be the case.

Well the 834 is a mono camera to start and don't think there is a colour version so keep that in mind. CMOS is steadily replacing CCD in the market. Not really because one tech is better than another but other sectors want the (much) faster readout and apart from science dedicated businesses CCD has a limited demand. The 2600MC will give you a larger field of view, slightly more sensitive (especially in the blue) and faster capture rates with potentially tens of frames per second (which can help if you have a less well behaved mount and could use it for planetary). The 834 should have more stable noise characteristics which will be easier to calibrate out (CMOS generally has walking floor noise). CCDs also bin better than CMOS (for the former this reduces noise, but not really in the latter so much). The noise and full well depth when you read out the sensor are generally comparable at the same gain settings - however for CMOS you generally can alter these yourself so you get more flexibility if you want higher read noise, but larger well depths or vice versa. A CCD is fixed in this regards. *Calibrated* CCD images generally still win out from a noise perspective because of their stability So it largely depends on what you want to do with it and the scope that it will be attached to. If you want to do any science work (photometry, spectroscopy) the CCD still wins out (stable noise that is easier to calibrate). If you just want photos of large nebulae the new CMOS give a lot of area for the same value. On the other hand this helps mostly for mid to long focal length instruments as generally even a smaller chip can cover most objects with a short focal length telescopes. Also keep in mind what telescope you are going to use. If you use mid/long focal lengths (or are planned for in the future) then larger pixels can be better otherwise you are sampling too finely. Just to note in terms of the 834 unless you are using very short focal lengths the 694 might still be the better choice.

The second image also is definitely not in focus so that isn't going to help with the quality of the image. It is hard work to start imaging with a long focal length telescope. Your set up needs to be that much more refined to be able to manage this. Getting a wedge might also help as you won't need to track in two axes at once, once properly set up. But really to start with you want a short focus length refractor. Nevertheless it is a long journey and for your starting images they are very good.

There is also this company/person that is more active on IceinSpace. They are also based in Aus I believe so would give you ask to objects you would never see in the northern hemisphere. Remote Imaging and Telescope Hosting — Astrophotography by Martin Pugh (MPC Q56) (martinpughastrophotography.space) I thought there was another similar project that used Officina Stellare telescopes but can't seem to find them having a quick look so maybe they don't exist anymore. If you are just after data to play with (and are less interested in the imagining side) then maybe ask around for anyone that might want to share data with someone that does have a remote set up. It might not be 'professional' as the above options but a good relationship might give you more objects you wish to process (and the person with the equipment gets some support to the hosting costs). In comparison a subscription model depends on how many people are subscribing to that 'scope. If you mainly want to process galaxies but you join a nebula dominated group you might not get as many targets observed as you would like etc.

Still, if you need to align it properly for flats after you have imaged then you still need one that is accurate (otherwise dust bunnies will be in different places for the flats etc).