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Andrew_B

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Everything posted by Andrew_B

  1. It's a sweeping statement to say that one design is unequivocally better than the other and they all have their strengths and weaknesses. The ideal scope would probably be an unobstructed three-mirror anastigmat but there are currently no commercially available telescopes of this type. A Newtonanian can't be as well corrected as two or three-mirror designs without additional optics but for planetary observing things like off-axis coma isn't a major problem so designs like the Newtonian and the Dall-Kirkham work very well. Having two or more curved mirrors has its advantages but it can also make the scope more sensitive to collimation errors and harder to collimate. At a given price point you'll also get a bigger and/or better instrument with a Newtonian due to its simplicity and in long focal ratio models the mirror is relatively easy to fabricate well and allows for a small secondary which is an advantage, especially for the planetary observer.
  2. According to FLO it screws onto the end of the focuser with an M63 x1 thread by the looks of it.
  3. I bought something similar through Aliexpress and looking on there now there are a few sellers offering that same basic item for less than £25 including shipping.
  4. I don't think you'd be disappointed by the X-T3. I love the Fuji cameras and even though mine are very basic things like the out of camera JPEGs can be superb. Granted that's not relevant to astrophotography but I think there's a lot to be said for a simplified workflow for normal photography and there's nothing to stop you shooting raw as well to give you more post-processing options if you want something different from what the camera itself has done. I'm sure the Pentax would be an amazing camera but I don't think full frame is necessary for good AP and it brings additional costs that you might not want to pay. Like you say, it's a much heavier camera so you're losing much of the advantage of APS-C mirrorless which allows for very small and light cameras that don't stress focusers or mounts all that much. The other thing is that while plenty of lenses and telescopes will produce a good image across the 29mm diagonal of an APS-C sensor, you'll find a lot of them aren't suitable for the larger 43mm diagonal of full frame. You see this particularly with things like focal reducers which often only quote a 30-40mm image circle and outside that you get severe vignetting or very visible aberrations. I wouldn't worry too much about trying to get one perfect camera at this point - you want something that will work well and you'll enjoy using but there's no reason why you can't upgrade or add another camera at a later date that might be better suited for astro. Focusing on learning how to image and your processing workflow will deliver amazing results from even very low end gear but even the best camera is going to produce disappointing results if your processing skills aren't up to much. I think you'd enjoy the X-T3 and so long as your stacking software handles the raw format (Astro Pixel Processor for example works just fine) I think you'll be impressed by its all-round qualities.
  5. Indeed. They don't make 'em like they used to ... thank goodness! Touching up optics and carefully rotating elements into the perfect position is a valid method when you're talking about very high end optics like A-P / Tak / TEC, but if you're doing it with a value-oriented product like an SCT it's more likely to be a way of getting round poor QC and inconsistent manufacturing methods.
  6. Quality control with SCTs seems to have been relatively hit and miss especially years ago, but I get the impression that newer models made by Synta have been much better and you're less likely to end up with a lemon.
  7. Are you wearing glasses and does the spike position change as you rotate your head?
  8. Thanks for your kind words. The X-T3 and X-T4 cameras are brilliant models and would make great all-rounders for astro and normal photography but they're not actually the best Fuji cameras for astrophotography because they perform noise reduction on the raw files which I don't think can be turned off. It's a little bit like what Sony do but nowhere near as aggressive so the impact on your images would be far less, but I've seen posts on dpreview where people have tested this and it does reduce the visibility of faint stars in an image compared to what should be there. This noise reduction is only implemented in Fuji's X-Trans models and their cheaper cameras that use normal Bayer patterns don't seem to be affected so although it's not a good a camera in terms of all round performance, an X-T100 is in some respects a better choice for astro than the X-T3. It doesn't have as good a screen though, so getting your lenses focused at the start of a session is a bit more fiddly. I think difference is relatively subtle so it's not like you can't get good astro shots with the more expensive models, just that you don't need to spend that much if astro is your number one priority but if you want a great camera for every use then you'll appreciate the features and handling of the better models. Samyang lenses are available natively in X mount and you can also get relatively cheap adaptors to fit lenses made for Canon EOS or Nikon F mount onto your Fuji camera. A nice thing about the Fuji cameras is that their red sensitivity is good enough as standard that you can take really good astro shots without having to mod them first. I've even short H-alpha narrowband with my stock X-T100 and got a surprisingly good result.
  9. I'd be happy with either make but I went with Fuji (X-A3 and X-T100) because their red sensitivity out of the box is pretty good and much higher than other makes apart from dedicated astro models. Canon have the advantage of having a bigger range of lenses, although mirrorless cameras generally work well with older manual lenses of any type. Software to remote control your camera from a PC is also only available for Canon (and Nikon) cameras from what I've seen and adaptors and accessories can be easier to find.
  10. Some of the Canon mirrorless cameras look pretty good - the range of lenses available for EOS mount is huge and being mirrorless the shorter flange focal distance means a lot of other lens types can be used with adaptors. The only downside with a stock camera is that most have relatively little red sensitivity and would need to be modified to fully realise their astro capabilities, but that's something you could have done at a later date. The aggressive noise reduction kicks in when bulb mode is used on some Sony cameras so exposures of 30s or less would be normal. Other models had this behaviour appear with anything over a 4s exposure which isn't very useful. I found some info about the problem here and here. Thanks for the kind words about the image. I used a mix of 90s exposures for the H-alpha and 120s exposures for the O-III data which would obviously have run into issues with a Sony camera. It's a shame because they're good cameras otherwise.
  11. A 2" prism is apparently more likely to cause noticeable false colour than a 1.25" one, simply because of the extra glass the light has to travel through. If you want to minimise scatter while also keeping false colour to a minimum then a 1.25" prism is the way to go but if you want a 2" model then a good quality mirror is probably the better choice.
  12. I've got that 32mm Baader prism and it's great quality for the money. I felt like I was seeing a little bit more contrast and fine detail compared to my dielectric mirror diagonal but any difference was subtle although the prism has the advantage of being a bit more flexible due to its T-2 connections.
  13. Any laser powerful enough to damage a lens would be far too powerful to use anywhere near unprotected eyes.
  14. One nice thing about the FS-60 in Q mode is that the relatively slow focal ratio is pretty forgiving with eyepieces and even relatively cheap ones like basic Plössls can deliver great views. If I want a high power zoom I use my Baader Hyperion 8-24mm with the dedicated 2.25x Barlow to give 3.6-10.7mm (56x-159x magnification) since I can't afford the Nagler zoom. I was using a Barlowed 6mm Fujiyama ortho with my FS-60Q last night to look at the Moon and it was surprising how well the image held up at 225x magnification even in moderate seeing so it's obviously one of those scopes that can take high magnifications very well considering its tiny size.
  15. That sounds like a lot less detail than you'd see through a decent 3" refractor. Is the 105mm ETX really that bad?
  16. I like the Hyperion Zoom and I found it looked brighter and more contrasty at the 8mm setting than my 8mm BST Starguider which is a respectable lens in its own right. With the 2.25x Barlow you get a very flexible setup covering 3.6-10.7mm and 8-24mm and I've liked using mine and felt it was good value for money. Your Skymax is going to be more forgiving of cheaper eyepieces than the 8" GSO due to its longer focal ratio so you might find that even a really cheap Plössl looks good in your Mak but might be a bit disappointing in the Dob.
  17. I think you're right. Something else I've read and tend to agree with is that once you're using reasonable mid-range eyepieces, you'll usually see more of a difference by spending money on a bigger or better scope than you would upgrading your eyepiece collection.
  18. Sony sensors are brilliant but the cameras that use them can have image processing pipelines which implement noise reduction or other 'features' which can't be turned off, even when shooting raw. It's a software issue rather than hardware but if the embedded firmware doesn't allow the user to control these settings then you're a bit stuck. It's a bit of a cheat by camera manufacturers to make their products seem like they have better noise control than they really do. I don't mind JPEGs with always-on noise reduction but if shooting raw then it should be the unadulterated data coming off the sensor. The problem is partly caused by the kind of obsessive pixel peeping you see in reviews and on websites like dpreview where there's endless moaning about noise when shooting at high ISOs that back in the days of film would have been considered almost unusable and in response manufacturers (not just Sony) have sometimes fiddled the figures. Fuji do it in their higher end X-Trans models (although less aggressively than Sony) which is why I stuck to their cheaper and more basic cameras that use a standard Bayer pattern and produce proper raw files. You don't have to invest a lot to get good image quality from a camera and there are places like MPB.com which specialised in selling used photo gear and who have a proper returns policy and 6 month guarantee if you'd rather stay away from places like eBay. Something with a similar spec to the A6400 can be had relatively cheaply - the shot below was taken with my £180 eBay special and I think it did a good job for such a basic camera shooting narrowband in H-alpha and O-III. You can put together a very capable kit for a lot less than £2000, especially if you're buying some or all of it secondhand.
  19. How does the false colour in a large achromat compare to what you'd see with something like a small f6 ED doublet?
  20. Do you have a budget in mind? The most grab and go setup in terms of being ready to use ASAP with little cool down time would be a small refractor. A Mak should be good for the Moon and planets and is a really compact solution, but they're not the quickest to acclimatise.
  21. The Samyang lens is superb and very highly regarded. I don't have that particular lens but I've got a few other Samyang models and they're all brilliant. Sony cameras have great sensors but you do need to be careful about their suitability for astrophotography. Sony tend to implement a rather aggressive form of noise reduction which is applied to the raw files themselves and can't be turned off (unless this has changed recently) and it manifests itself by deleting fainter stars from the image, thinking they're actually noise. It's known as the "star eater" bug and it would be worth checking whether it's still an issue for that particular camera. I'm big fan of mirrorless cameras generally. Their small size, light weight, and short back focus distance makes them a great choice for all sorts of photography, but astrophotography in general. I've got a couple of 24 megapixel Fuji mirrorless cameras which use Sony sensors and are surprisingly good. Different makes and models have their pros and cons and it's not uncommon for cheaper models to be better suited to astro than more expensive ones because they're less likely to have fancy features that you don't need and can't turn off. You can get great deals by shopping secondhand and there are real bargains to be had in pre-modded cameras that have had their stock filters removed or changed to give them much better red sensitivity and massively improve their performance for astro imaging. My little 24MP full-spectrum modded Fuji only cost me £180 which is less than I'd have to pay to get an existing camera modified. Gear nowadays is so good that even very low end cameras are far better than what was the state of the art not that many years ago. Cheap kit and putting your efforts into learning the techniques and workflow for astro imaging will deliver far better results than throwing money at the problem but not developing those skills.
  22. I've got an AZ GTi and I can confirm that my FC-76DCU worked absolutely fine on it. Seems to work even with larger scopes such as the FC-100D models although I would have thought the DF and DZ versions might be pushing it a bit given their weight.
  23. I don't know if you've seen this article by William Paulini (BillP) reviewing different diagonals. There's some very useful info about optical path lengths which could be handy in deciding which diagonal to use and it shows prisms having significantly shorter optical lengths than equivalent mirrors as well as a useful comparison of other specifications and features.
  24. Have you done much astrophotography just using basic camera lenses? Shopping secondhand can get you some real bargains and you might be surprised how much detail you can capture with something like a short telephoto. There are a few advantages with this approach - shorter focal length means tracking errors are less of an issue and camera lenses typically have faster focal ratios than scopes so even when stopping them down a bit to control aberrations you can normally get away with shorter exposures. You're still learning the same workflow that applies to shooting with a scope but it's easier and less likely to cause frustrations and astrophotography can be tricky enough without making things harder than they need to be when you're a beginner.
  25. Plastic construction has a bad reputation in astronomy that's not entirely undeserved given that it's mostly used in very cheap products and is often poor quality. The right plastics used in the right way are every bit as good as metals and it's worth remembering that even things like missile re-entry vehicles are made of reinforced plastic so it's hardly weak or easily damaged stuff. Have you ever had a chance to compare the Tak prism to prisms from other manufacturers?
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