Jump to content



New Members
  • Posts

  • Joined

  • Last visited


10 Good
  1. Hi everyone, I'm looking at Page 7 of the November Sky at Night - the image titled 'Companions in Carina', a wide star-field apparently captured from the ESO in August. I wonder what's going on here - all of the major stars have a disk around them and on closer inspection, one can see that the disks are offset a little towards the edge of the image. Finally, looking at the two bright blue stars at the bottom right of the image, you can even see the shadow of the secondary mirror and the supports. You can see the same thing in another of their images, here: http://www.eso.org/gallery/d/104814-4/phot-26a-09-hires.jpg, though less obvious. The scope in question is a 2.2m f/8 RC. Because of this it seems odd that a it would suffer from this problem at all as a defect of the optics. Had a quick poke around their pages but no mentions that I could find. My theory is that it's simply an out-of-focus exposure or two which for some reason are stacked in with the others, but I can't fathom why that might be the case. Any thoughts?
  2. I find if you close one eye for a while and use the open eye to look to the distance, it mis-aligns or deforms the closed eye and it takes a while to settle back afterwards; helped enormously by covering your not-used eye instead of closing it, so it can relax.
  3. For those who haven't seen it before, the image she shows at the end can be seen here: APOD: 2009 January 11 - In the Shadow of Saturn (full size 2766x1364: here). Earth is the pale 'star' at about 10 o'clock just outside the main rings.
  4. Hi! I experimented with this a while ago, all I had to buy was a second long dovetail bar. I wanted to see if it could be done roughly and cheaply. Unfortuantely drilling holes is required though. So hopefully there's a camera mounting bolt poking out on top of one of the 200P tube rings. There's another one on one of the ST80 tube rings. If you cut away a square of the felt under where the bolt is on the ST80 rings, you can remove that bolt with a normal screwdriver. Then do the opposite to the 200P tube ring which doesn't have the bolt - ergo, you will have a bolt poking out of both rings on your 200P. Then you need a dovetail of the same size as the one your 200P is mounted on. As the rings are positioned over the holes on the lower dovetail, you should be able to drop the second one on top. To fasten it, you can use the big disc-like nut things that (when using them as camera mounts) you put under the camera. Does up nice and tight if you put the flat side of the disk facing up. I wouldn't want to use this dovetail as a handle pick it up or mount anything heavy there, but for an ST80 it seemed fine to me with the disc-thingies. Finally if you drill some holes in this at appropriate positions in the upper dovetail, you can then mount the ST80 rings and hence the scope. Don't worry about the holes not being perfectly straight -- if you're using collimating rings you can correct. I also bought some SW 120mm tube rings for use as collimation rings, though this might not be too critical if you're guiding with it? Hope that at least gives you some ideas. EDIT: Ahhh! Just realised, the second tube ring bolt MAY have come from the pair of oversized rings I purchased with the intent of making collimating rings.
  5. Second what matti said, you're almost certainly not focussed. As you got the scope today you're presumably using the supplied 25mm and 10mm eyepieces, Jupiter will focus to a very small disc in the 25mm EP (too small and bright to see cloud bands, in my experience, but great for seeing the moons) but the 25mm with the barlow, or the 10mm on its own will give a more "Jupiter like" view! You'll have to re-focus when you change eyepiece or add a barlow. Enjoy the scope, it's great fun
  6. If you point at say Vega which has a known RA and Dec position, for the sake of argument suppose it's RA 4 hours and 30 minutes, then by rotating your RA axis (or running your motor drive) during the evening you're working to *stay* pointed at RA 4h30m (and hence Vega). Your RA axis value thus shouldn't change, as you're pointing at the same place, so you lock the axis and let the scope move but the axis not. The co-ordinate system itself rotates so RA 4h30m isn't in the same spot for long. This is how I think about it, which of course could be totally wrong... it's all hopeless though for me as the RA circles on an EQ3-2 don't lock at any other position than 0, so it slips around anyway. All I can do (I think) is to re-calibrate every time I want to use them, which isn't often, fortunately.
  7. I did some research on this myself as I'm tempted by an HEQ5/EQ6 Syntrek and want the option of this exact upgrade. So there's 3 versions: The 'bog standard' HEQ5 and EQ6 are just a mount with RA/Dec motors. The Syntrek has a motherboard so it's a bit more smart (afaik it can do non-PEC guiding or you can drive it from a PC), but still has just the tracking controls on the handset. The Synscan (Skyscan?) has the same motherboard but it has a goto handset. So the handsets for the Synscan and Syntrek are interchangeable but not for the basic model. HTH. Someone else may be able to correct me if I'm wrong about the basic model.
  8. I tried to piggy back an ST80 on a 150mm f/8 newt on my EQ3-2 and even with both counterweights as far down the shaft as it would go, it wouldn't balance. If I had another 'big' (3kg?) counterweight I think it would work but it would seem to me as if that might start risking bending something. I mean the whole weight of everything on the mount rests against the altitude adjustment bolt, doesn't seem like it would take much more to start to bend that? I guess this would be the practical limit -- you could probably do an 8" Newt though if you were stubborn As others have said the supplied tripod will then start to be a problem.
  9. The 25mm EP that comes with the scope isn't bad, the 10mm aint so great. Both are adequate to get started, though virtually anything >£30 would be an improvement. I use a Skywatcher Extraflat 19mm with mine, for the money (about £42 IIRC) I've been quite impressed so far. To start with you wont need anything else but a moon filter or neutral-density so that the moon is not uber bright -- optional though, you just wont be able to see much for a while after looking at the unfiltered moon.
  10. Welcome to the 150PL club The mount has two locations where there are prepared holes/fixtures for the motor drive kit. The RA motor has a hex-bolt screwed into the body of the mount, the dec motor has a bolt hole on the side of the cradle where you mount the scope -- so it should all be just allen keys, screws, nuts and bolts which is in keeping with how the rest of the mount is held together. AFAIK the dec motor bolts just below the scope, and the RA motor has a kind of L shaped bracket which is bolted to the mount using the aformentioned bolt. Enjoy!
  11. Hi and welcome from one Peter to another! DSLR = Digital Single Lens Reflex camera. You completely remove the standard lens from it and with an adaptor you use the telescope as the 'lens'. How easy it is to achieve depends on the telescope design. This is called prime focus photography. You can't do this with compact digi cams as the lenses aren't removable, but you can take a photo through the eyepiece - known as afocal or eyepiece projection.
  12. Thats true but you're only really considering the surface of the paper in the example. Paper just serves as a suitable prop because it is very thin -- not zero thickness, of course, so you have to 'pretend' it's flat. That's exactly it.. to demonstrate gravity's effect on spacetime for example, the famous ball-on-a-rubber-sheet demonstration puts the 4D phenomenon into simple 3D terms. You have X and Y position on the sheet representing space, and the Z (up/down) direction is used to represent the distortion of spacetime caused by gravity/mass. Of course with a real object, the effect on spacetime happens in 4 dimensions, so space and time are deformed around the mass in all directions - you have 4 things you want to show but only 3 dimensions - you have to simplify somewhere hence the "pretend this paper is space"
  13. In the same way you folded the two dimensional sheet through the third dimension, you would fold the three dimensional space through the fourth dimension. You would pick two points to be the ends of your wormhole, and bend them through the fourth dimension until they touched. A simpler example would be to consider rolling a sheet of paper so that the two opposite ends of the sheet touch - to any hypothetical 2d-being on the surface of that paper, it is now infinitely long, or they can instantly travel to the opposite end of the sheet by walking off the top. If they walk along it, when they step across the join they're wormholed back to the other end! As they have no concept of "up" - the third dimension - they aren't aware of the fold through it, just as we would not be if if was a 4th dimensional fold -- you would enter this space and instantly be somewhere else, although the distance back to the other end of the wormhole is minimal.
  14. I agree with jahnmanson M81+82 are nicer galaxies to admire your handy-work at finding with - and you can get them both in the same view Andro to me certainly is fascinating but I can't help but get the idea people are a little disappointed when I say "behold! the nearest galxy!" and it looks like someone sneezed some grey stuff onto the mirror. At the moment I'm rather fond of what I think is M22 though - Point into the milky way in the south (ish). With binoculars, in the area just up in an alt-azimuth sense from Sagittarius you might see a small fuzzy, globule. I think it's about 2 fist-widths above the horizon. To the best of my memory it's near an almost rectangular asterism of 4 stars which you'll need a finderscope/bins to see - with a 9x50 finderscope it's fairly easy. I use a 20mm EP for 75x magnification, and it's fabulous - many individual stars. You'll know if you've got the right cluster cos there's a star right in the middle that's brighter than all the others.
  15. Not going for the GCSE myself, don't need it, but I wish I'd had the chance back at school Would have been a toss up between electronics and astronomy though -- tough one. For anyone worried about maths in the Astro GCSE, hopefully this nugget will re-assure you: a good thing about GCSE exams requiring maths to be done are that you can get what are called ECF marks - Error Carried Forwards. That means that if you had previously worked out some value (e.g. an angle) incorrectly, and needed to use it in a subsequent question (e.g. calculate the area of the triangle), then you can get marks for using the right formulas and working through to a sensible answer, even if the answer is wrong in the end. Most questions needing maths are multi-mark, only ONE mark is for the right answer, the rest are for using the right formula, making certain observations along the way, or whatever. Just write the correct number and you get 1 mark on a question with maybe 8 marks, cos you haven't shown you know how to get to it, which is arguably more important. If you take A-Level physics (well, depending on who provides the course) there's more astronomy (and electronics) relevant stuff too, though that may have been obvious. For astro you get optics, or maybe that should be electro-magnetics because the principles are applied to radio, etc., too: refraction, diffraction and interference for example. You get some cosmologically relevant stuff: gravity, magnetic fields and cosmic rays for example, and on some courses there's also a bit on stars - Hertzsprung-Russel diagram comes to mind, though the stuff on fusion [part of radioactivity] is relevant too. Additionally if you're lucky you get exposure to a thing called Mr. Einstein's Special Relativity. This will savagely mess with your head for a couple of weeks then become somewhat clearer. It helps if your lecturer is somewhat eccentric. Admittedly I did my A-Levels 4-5 years ago but I can't imagine it's much different now content wise. It's all come in useful, in unexpected ways: At uni my final year project was a basic simulator for the N-Body problem, which considering I was doing straight computer science with 'middle' maths was rather a challenge. I picked it myself based on a passing interest, and I'm glad I did because the assigned projects were all so uninspiring. If you're interested it's nice knowledge to have, and it sticks with you even if you forget the fine details.
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue. By using this site, you agree to our Terms of Use.