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Found 8 results

  1. I read a comment made on here the other day about the maximum magnification you can realistically use in UK skies (250x apparently). Therefore I was wondering what everyone else thinks this is, especially for you guys with 16" plus, apertures. I'm still fairly new to this game (only being observing for about 7 months), and only have a 5" Newt at the moment (but am about to replace with a 10" Dob) so I don't get any higher than 159x (6.3 mm).
  2. There is something that makes me think practicality. We can all agree that a long focal length scope is better suited for planetary use than its short length brother which would be best suited for dso viewing or guiding/photo. We can take those two (refractors) as an example: 90/900 and his brother, a 90/500 (and we will be using Plossl EPs) Exit pupil is an important factor in viewing comfort. Exit pupils are dependent on the scope's focal length, the EP's fl and the main lens diameter. For example, to acheive 100x in the 90/500 we will need a 5mm eyepiece and to acheive the same mag in the 90/900 we will need a 9mm eyepiece. The exit pupils of both scopes in those configurations will be 90/100=0.9mm The theoretical magnification limit for both scopes lies at about 180x. It is true that to reach this 180x you will need a 5mm EP in the 90/900 and a "2.8"mm EP in the 90/500 and those will probably make for an eyelash brushing eye relief... But looking at exit pupils up to 100x, those scopes do not seem to complement one another, but rather replace each other. So, ignoring abberations, and not taking into account eye relief so much, wouldn't the faster scope be almost as practical and easy on the eyes for high-ish magnifications as the slower, heavier, harder to mount in the wind scope? just my evening neurons buzzing...
  3. Hey guys. Thought about starting this thread. I feel like we all should inform eachother and newer members alike about the magngifications that can be achieved on planets,that provide the best sharpness/size ratio,depending on the scope and seeing. After this thread has grown a bit, i feel like this should be pinned,as to provide a little guide to newer members that are not experienced with planetary observing,as many will be fooled with the typical 50x per inch of aperture and get disappointed when they find that that image will be dim and blurry. For my 8” F/6 Sky-Watcher Dob For Saturn i like to use 150x in medium seeing and if i want something a bit bigger , switch to 240x ,which will give me a bigger,but blurrier image.iBut In good seeing, i found that 240x was very usable.When we have perfect conditions, i m certainly trying 300x. Mars, isnt very big in the sky right now,so even at high magnifications like 300x it still appears as a small orange dot. For observing mars,I suggest waiting for it to reach opposition.It benifits hugely from it! However,this happens once every 2 years....But 5ere are other planets to keep you occupied until then, such as jupiter,saturn and Venus. For Venus, i use 50-100-120 depending on its phase. For Jupiter, i like to use 150x, as it provides a very sharp image,with key features of the planet such as bands being very detailed.Waiting on my 6mm UWA Skywatcher to bring it to 200 and see how that plays out. Be careful! Don’t magnify jupiter too much, as it will loose much of its features and sharpness. Neptune and Uranus: These two will not impress, but are certainly have a nice colour to them. Even ar high magnifications, such as 300x and 400x, they will look like small discs with color in them.Uranus will look be colored green and Neptune a fainter blue. Mercury About mercury...Havent gotten the chance to observe it ,so the guys will have to inform you about that? Feel free to give your own opinions as to give members a wider source of information to help them observe better ! Cheers and clear skies. Kronos
  4. Hello. True beginner given an Orion Skyquest XT8 (1200mm focal length; f5.9). I have had to collimate (all sorts of fun that was) as the scope had been moved quite a bit over time. Believe I have it very near perfect but will star test. Scope came with an Orion 25mm Plossl eyepiece so I am exploring what range of additional eyepieces I would like. From what I’ve read this scope is capable of a theoretical 400x magnification. Again in theory that would take me to 3mm as limit of eyepiece. But then I read about exit pupil limitations and scratching my newbie head. The majority of what I see suggests .7mm exit pupil minimum...? But it appears I would need to buy a much larger eyepiece focal length to avoid too small exit pupil. I wear eye glasses so would be buying longer eye relief pieces in case that is relevant. Advice truly welcome. Neill
  5. I just ordered the SkyWatcher 200P Dobsonian from FLO this afternoon and after reading a lot of reviews on this model definitely believe I made the right choice ... Does anyone have any suggestions on the maximum ( or maybe " reasonable " would be a better word ) magnification for the planets , specifically Jupiter and Saturn ? So far with my Meade Infinity 600/90/f6.7 refractor and the 6.3mm kit lens I see both planets at around X95 magnification which shows the bands on Jupiter and that fainter , thinner band 2/3 up on Saturn ( anyone know what that one is called ? ) and also the moons too ... What has proved to be elusive so far is the famous red spot on Jupiter and also the Cassini division on Saturn's ring system ... Has anyone ever even tried the maximum magnification of X406 on the planets or would that be only really usable on the Moon . Any advice would be very appreciated .
  6. Hi all! I was just wondering about something, and would much appreciate to hear some opinions /suggestions... Premise: I'm just starting, very green, and very curious... With my f5 Newton and DSLR I have been getting some very satisfying results so far, apart from the expected coma and tracking issues. I was wondering if it was at all possible to have more magnification with such a setup, to be able to catch also the smaller DSOs... I have been told that those smaller objects are difficult in that one needs longer focals, and thus longer exposures, and thus better guiding. So, just slapping on a barlow between the tube and the dslr would only frustrate things, apart from focussing issues... Can anyone confirm this? This is obviously a long term issue for me, as at the moment, I'm quite happy with the setup I have, and the lack of funds for now puts any ideas I might have on hold. But for the future it would be very interesting to know what options there are for really far DSOs... I would definitely first of all start with setting up auto guide (not just for far DSO), so guide scope, guide cam and PC + connections and software. That's a big bite. Afterwards it would probably be: buying a purpose scope for deep DSOs, long focal, big aperture. SC? RC? A good APO? Opins? thanks all! Gerhard.
  7. Hello all, Disclaimer for all: I am still a newbie so good chance this is a bad question, but I was hoping for an explanation anyway. I've got a SkyWatcher 8" (1200mm FL) Dobsonian (manual, no GOTO). So far, I am mostly interested in visual and AP planets. I have recently started gradually upgrading my equipment. Got a ZWO ASI 224MC, and a TV Powermate 2.5x (hoping to get an HEQ5 mount soon too). Here is where the baffling happens. According to math, my scope's potential magnification is 400x (200mm aperture x2). Obviously that is supposed to be theoretical, true only for nights with perfect seeing, and in the past, using a typical 2x barlow and a 6mm plossl, I could touch that 400x (1200x2 /6 = 400) , and my mileage would vary according to seeing, so it verified the hypothesis. Along came my new equipment, the camera and the powermate. The maths for this produce a magnification of 491x (1200x2.5 / 6.1mm) which by far exceed the theoretical maximum. I was, however, able to produce the attached planetary pics, which I think are pretty decent for a manual dobsonian, considering I have still not fully mastered the art of stacking and processing, and the fact that they were taken from within the city (Thessaloniki, Greece). I have also noticed that visually, when using the Powermate and the 6mm eyepiece (500x zoom), it still looks as clear as, if not clearer than the common 2x barlow and 6mm eyepiece combo(400x). So I guess these are my questions: 1. When doing AP, is the maximum zoom we can use higher than for visual, because of stacking, or not? 2. Is there a chance that the TV Powermate can implicitly increase the theoretical max magnification, because of its superior quality? 3. Would adding a motorized mount, enhance the results I get, or have I pretty much reached the absolute max quality shots I can get with the specific OTA? Thanks a lot in advance, Alex
  8. OK so just as I was writing my original and confused question I had a thought and think I might have worked it out. I've attached a drawing to try and show what I mean and help others if they're ever as confused as I was. I could only find sources that quoted brightness reduces four-fold for a two-fold increase in magnification, but I just couldn't wrap my head around and visualise it (too little mental exercise these days!!) - I knew it was something to do with the area of a circle but that's about it. Then I had a thought and made a little drawing: The blue circle represents what the telescope can see - for example it's maximum field of view (i.e. the most amount of sky it could ever possibly see: I worked out a theoretical 18.92 degrees for the SW200P - the second image shows how I came to this conclusion). The grey object (of no particular shape) in the middle of these blue circles is the same size because as far as the telescope is concerned the sky is the same scale (the scope still "see's" the same circle of sky). The red circle represents a lower power eyepiece's view and encircles a larger [field of view] area of the sky (the lower red circle show's what we'd see in the eyepiece: a smaller, brighter object) The green line represents a higher power eyepiece's view and encircles a narrower [field of view] area of the sky (the lower green circle show's what we'd see in the eyepiece: a larger, dimmer object) Am I right in thinking that the higher power eyepiece takes the light from a smaller [field of view] 'circle' in the sky than the lower power, but 'blows it up' to the same size in the eyepiece for us to see, as in the lower green and red circles? And if so is that what explains why the brightness goes down four-fold for a two-times magnification (because the light from a smaller [field of view] area is being shown at the same/similar size to the eye)? And essentially is this right: the scope always see's the same [field of view] 'circle' of the sky but the different eyepieces pick out different sized [field of view] 'circles' of this? Before I realised this I was under the delusional and confused impression that a smaller object in the sky might be brighter because the whole of the objective aperture could be used for that one object!!
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