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London_David

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About London_David

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  1. Which cam

    Just to complicate things slightly. ZWO has realeased the asi385 very recently. You can buy it direct from their website. This has very similar specs to the 224 but marginally better and about $150 more expensive. The main advantages are a slightly larger sensor and slightly lower read noise. I haven’t seen anything about the 385 and don’t own one — but there is a thread on cn about it. Thought I’d point it out in case you suddenly realise you’ve not seen all the options. However, from what you’ve been saying I suspect the asi224 colour is your best camera pick. I love my 290 but unless you’re really into mono before you buy I suspect you’ll want colour. The 290 mono is better and more flexible and will give you more detail but... there is something quite fun about just seeing a colour image appear, especially if this is your first camera. Between the 385 and the 224 I’d say it just depends on your budget — they’ll both be good.
  2. Which cam

    Personally I’d recommend the the ASI224 colour too. It’s the best bang for your buck in terms of sensitivity at the moment, so you can use shorter exposures and stack rather than having to worry about your mount so much (though a motorised tracking mount of some sort alt az or eq is still pretty essential). You can also use it on planets as a video camera into which will give you a live feed off the sensor.
  3. How do we define Video Astronmoy

    I agree with much of the above -- And I think the distinction is only useful in helping people find the right board to post on. So, the true definition is simply whatever the moderators say it is in the posting rules! However, if I was pushed to come up with one myself then I'd also suggest that it is entirely about intention. I'd also conflate EEA and Video -- since the word video relates to a technology of moving pictures, which is the same technology used in any cameras. All cameras are essentially video cameras now. So I'd say astrophotography is about aiming to create a beautiful or interesting image that, like any other photograph, has aesthetic or communicative value, and it is probably for made for an audience (even if that audience is only the photographer himself, at a later date). EEA and Video Astronomy is about the act of observing, whether that be in the moments at the scope with live stacking or, I would suggest digging into photographic data at a later point in time. How can you exclude from "electronically assisted astronomy" or "video astronomy" a scientist who is looking at images from a video camera sensor trying to determine the chemical make up of a star. However, it seems clear to me that this is not a suitable fit for "astrophotography". The image itself is not the value, but the information it contains. I don't think you can ever draw a clear and satisfying definition using technology or exposure times because they will always change, and the image will never really tell you what the technology was. And either way, does it matter how something was created if it looks exactly the same to the pixel? There is nothing inherent in an image that you can look at and see is the essence of astrophotography or video observing. Any image will resist classification outside a context. So, as a definition: In astrophotography you are primarily interested the aesthetics of the image. In EEA or Video Astronomy you are primarily interested the meaning of the image. It is true that under my definition some images may start as an EEA/video observation then become astrophotography.Or indeed, two people could look at the same image at the same time and one person is engaged in astrophotography while the other is engaged in EEA. It is the use of the image in the context of the moment you are asking the question that matters. But I think the main thing is that "EEA" "Video" and "astrophotography" have a vague but specific enough catch for people to just about know what it is -- so they can find the right place to talk about things without too many confusing posts from different interests clogging up the board...
  4. That is a good compact scope that’s not too expensive. The thing to be aware with that scope is that it is a little heavy and it is f11. That means that if you do want to try putting a camera on there (either your A7r or a future astronomy camera) you will need longer exposures than a scope faster f ratio (eg an f5). I don’t know the scope well, but for any kind of imaging you should ask if they have focal reducers that work on it since ideally you want to get the f ratio down. Ideally f5 or lower but f6 is also okay. That means you can use faster exposures and not worry too much about star trails and blurring (since it is an alt az mount). Of course you don’t need to buy any of this now, but it’s good to future proof if your interests change. You may have done this already but the best advice given to me was to go to astronomy.tools once you have an equipment shortlist. Check out what different scopes do with different eyepieces and cameras on different targets. That way you really do get a sense of what you will see when you point it at the sky. You want to make sure you can see the things you are interested in. The other thing that helped me was to take a long trip out of town and see them in person at a show room to get a sense of size and weight. Sometimes you just love or hate the thing itself, separate from the specifications!
  5. The A7 series has a very sensitive sensor and is great for sticking on a telescope... The A7s sensor is actually a little more sensitive with lower noise, if I remember correctly, than the ASI224. However, the camera control is harder. I don't think (I may be wrong) SharpCap currently supports live stacking with DSLR, however that is coming according to the developer. Various combinations of other software will make this work. Have a look at Astrotoaster and DSSlive. It's not quite as elegant or user friendly as SharpCap, but plenty people use that and it works well. Whether the image will cover the sensor fully or not depends on the scope, also you sometimes need to be careful of backfocus. As mentioned the easiest way to find out would be to just email FLO and ask them if the scopes will cover the full frame sensor. Having said that -- how much you care about coma and other unsightly stuff depends on what your doing, and your interest. Since the A7 is a high resolution full frame sensor, you could just crop in and cut off the edges. A full frame sensor is quite a large area of sky. Then again -- it does depend on what you are interested in imaging. Check out http://astronomy.tools/calculators/field_of_view/ with your camera and possible scopes to see what you are likely to get. You can also actually crank up the ISO on the Sony and look at the live view. It'll be super noisy, but you will be able to see things. There are some good examples on YouTube of this with the A7s -- not the A7r. Do remember when watching these that most are probably shot at f2 or so. That's extremely fast for a telescope and getting to that fspeed is expensive. Here is one at f7: In terms of the ZWO ASI cameras and Mac... unfortunately Mac OS is limiting for astronomy stuff. It's not specifically the cameras in this case -- it's the lack of software. SharpCap is PC only. I too am also Mac based though, and I ran my mount, SharpCap etc, on Windows 10 though Parallels on my MacBook Pro very happily. I did this for a while before getting a mobile solution. https://www.parallels.com/uk/ is an extra cost, but it's cheaper than buying a PC and you can even hide Windows 10 away in the background and never see it, making the PC software look like it's running natively on your Mac OS computer.
  6. When the physics, numbers and ratios get complicated to hold in the head, or you’re feeling lazy, a useful tool for visualising is https://astronomy.tools/ there you can play around and see what each change will do.
  7. How safe is buying from FLO?

    As everyone says, very safe. One thing to emphasise in addition is that they have excellent pre and post sales service. They’re always friendly and available for questions on email or phone. Plus I’ve had to return and switch stuff and it’s arrived fast and been easy.
  8. If you are interested in imaging, it’s worth checking out the video astronomy section here and the EEA section on Cloudy Nights. I started last March as a total beginner and was warned off photography. However, there are fantastic new cameras and while it is still very difficult to get spectacular images to rival Hubble, I’ve found that you can get surprisingly good images in bad conditions. I see more with my camera than I ever could visually because of London light pollution — and that’s was most important to me. Your entertainment in imaging does depend a little on how much you enjoy working with computers. You will spent time struggling with Windows and software. Personally I don’t mind that, tweaking these things to work how you want is part of the fun. For imaging, I wouldn’t let price or difficulty scare you off. You can get easier cheaper solutions than a heavy eq mount and scope. However, I would say if you don’t like computers, then avoid it. I have a small scope (150pds) and a lightweight mount (eq3-2 goto) and am very happy with what I get. An 80ed, a 130 or 150 newtonian or a 4” - 8” SCT (and focal reducer) will allow you to see stuff and take images if you get a cmos camera like the asi290 mono or the ASI224 colour. I suggest those only because I have the ZWO asi cameras and they are relatively inexpensive and very good. Other manufacturers make similar cameras with the same sensors. Yes you do need a heavy mount and expensive equipment if you want to win astro photography competitions, but if you just want to see stuff the bar is far lower. For imaging make sure you get a “fast” scope which is generally around f5 or less. That means you can make your exposures shorter, given the same amount of light. If you have a bit of a search on the Internet for examples with the equipment your interested in you can see the kind of results you can get. You can image dso’s with stacking at short exposures under 5 seconds. You can use an alt az mount for imaging so long as you keep your exposures short and stack — search out SharpCap and have a look at stacking. I would make sure you get a mount with tracking if you are remotely interested in imaging since it will be annoying and your results will not be good otherwise. A tracking mount is also futureproofing if you want to get into imaging later. Personally for £700 I would second either of the scopes suggested by alanjgreen above, or another option: https://www.firstlightoptics.com/sky-watcher-az-gti-wifi/sky-watcher-explorer-130ps-az-gti.html Or buy the 130pds and the Skywatcher GTi az mount separately, that would leave you with 256 and you could get a asi224 for £273, if you don’t mind spending the extra 50. Attatched is an image taken when I was playing with a new camera. This was using a 71mm refractor on a regular photo tripod — no proper mount, no tracking at all and I roughly eyeballed the focus since I had no bahtnov mask. I was also stacking exposures of a half second since the seeing was terrible. It’s not going to win any competitions but it was taken out of a bathroom window in central London with light coming in from the room next door. That’s what was on screen on my laptop as I was pointing the telescope at Orion. You could get much better images with the ASI224 and the 130pds or the 80ed in a reasonable location. As I said, for imaging, it does depend on how much you want to fly the computer rather than the mechanical-optical stuff through an eyepiece, but seeing dso is not so hard with a low noise high sensitivity camera.
  9. Time efficiency simulations of three cameras

    The spreadsheet sounds really interesting. I started putting together exactly the same thing for myself a few months ago but I could never quite get the maths right — plus I never use excel for more than a simple table so I was trying to figure that out too. I abandoned it to other things in the end. I’d love to check out your version but the link on your site gives me a 404 at the moment — can you repost. Thanks!
  10. EAA Field Observing Platform

    Back in March I was putting together an EEA setup for myself and got a lot of useful advice from people here. I also did a write up on what I bought. You may find the thread useful or give you some inspiration. My focus was on being lightweight small and portable, which guided decisions over other considerations. I’m really pleased with the way it has worked. I particularly like the compute stick / iPad setup for control. You just have to be careful about power requirements.
  11. What do you use to power your video cameras?

    I wanted a small light portable solution so I use Lithium Ion laptop/tablet external batteries. I have one battery to power the mount and one that powers the computer (Intel Compute Stick), camera (ASI290) and USB hub. The camera is powered through the USB hub using USB 3. They are light and small, so I attach them to the mount legs using 3M Command strips which keeps everything neat for setup and breakdown. The two I bought were: RAVPower Portable charger with QuickCharge 20100mAh -- I need the quick charge on this to power my coreM Compute Stick since it needs a higher amp rating. There's nothing special about this battery other than the Quickcharge. I get about 5+ hours of computer use with this. It's hard to guage. I've never actually managed to use all the power in the battery in a night of viewing. I always recharge at the end of a night. Poweradd Pilot Pro 2 23000mAh -- this is what I use for the mount because the control box needed a 12V in. There aren't too many LiIon batteries out there that output 12V. When I bought it this was the best bang for the buck -- it also has variable voltage options and a nice percentage guage. I get about 12 hours mount control out of this. I don't always recharge, so I usually get about 2 evenings with some power left over. There may be better options out there over the past year, but I found Amazon the best place for these batteries since they are intended for laptops and phones, rather than the astronomy shops.
  12. Looks like I’m in the minority here but I find working with the tech part of the fun and the challenge. That said, I often find Windows very frustrating - and it is the core of my system. I could do without the OS just doing bad stuff to me. From from random unwanted updates at inopportune moments, to running out of disk space because of OS temp files, to the occasional mysterious RDP failure, it drives me crazy at least once a month. But you take the rough with the smooth.
  13. How do you mount your Telrad?

    3M make load bearing velcro designed for hanging pictures. They’re great for sticking anything to a surface, especially if you want to take it on and off. I added some small blocks to flatten the underside of the Telrad base, so I could add “Command” strips instead of their double sided sticky tape: https://www.amazon.co.uk/dp/B004051TE2/ref=cm_sw_r_cp_api_6IN7zbNWXX7W9 I have some black command strips round the ota at different positions. That way I can rotate the tube and snap the telrad back on very quickly. Mainly I just velcro on and off the base part of the telrad during setup/breakdown. The strips also peel off easily with no damage.
  14. As a rule of thumb most lenses are sharpest 2 stops down. It varies from lens to lens. A great place to explore about classical photographic lenses is Ken Rockwell’s website. His article on sharpness is very good on this: http://www.kenrockwell.com/tech/lens-sharpness.htm More than anything, photographers pay high premiums to have lenses that give them more options in more situations. It’s more difficult to make a zoom lens that performs well at f5.6-f22 from 75mm-300mm than a fixed aperture prime f4.9 300mm. Hence why — for similar performance — zoom lenses are more expensive than primes, and fixed aperture refractors can be cheaper than adjustable aperture lenses. That’s not to say classical lenses won’t perform for astro, they can and do. If the tool works, then great! The technology is only there to provide options and the ease of use. On the diffraction spikes, personally I would avoid using step down rings as a solution. Step down rings are designed for changing the thread size on the outer thread of a lens so you can screw in filters or accessories of different thread sizes, they cant change the aperture, only the size of the light entrance opening of the lens. Using rings to vignette the image may reduce the spikes but the aperture is set with the blades at the diaphragm inside the lens. If the intention is to optimise the optics and performance, blurring the light path is not a optimal solution. It may blur out the faintest stars for example. That may be fine for the intended final image, maybe a wide field nebula shot rich in colour — but for me I’m often trying to see deep faint objects not make things pretty so that’s not a solution. It just introduces noise in the whole image to soften the spikes in the highlights. There are lots of great options at different costs but classical photo lenses are not necessarily better or cheaper. They can be, but it depends the intended use, and how it works with the camera being used.
  15. As I understand it (and someone may have mentioned this in this thread)... but the two things to be aware of with a regular photographic lens are diffraction spikes and the optimized f stop for the lens. Since refracting telescopes are a fixed aperture, stars have no diffraction spikes: the aperture is perfectly round (whereas on a Newtonian you get the distinctive cross). If you have a classical photographic lens with a changeable aperture, there are moving blades to change the size of the hole and you get a spike for each blade. With some designs you could have 15 spikes coming from your stars. Maybe you like the look of tiny shiny spikes on stars, or maybe not, but it is something to be aware of and historical some have regarded them as "imaging errors". For me, I quite like them sometimes (and now you can even get filters on photoshop to add diffraction spikes to perfectly round crisp stars...). Regular camera lenses are also optimized for shooting below wide open. So an f3.2 rated lens could have best imaging performance several f-stops lower. Buying a great classical photo lens means you will be paying for features, qualities and mechanics you may not need in astro photography (changeable f-stop from mechanical shutter blades being one). Hence why it is possible for a well designed and made refractor to be cheaper than a traditional DSLR camera lens for the same performance. It doesn't make either type of tool necessarily better or worse: they're just different shapes of hammer.
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