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acey

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About acey

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    Deep-sky observer
  • Birthday 10/12/61

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    http://www.crumey.toucansurf.com/index.html

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  1. I wouldn't wash any mirror with a coating less than a year old. I made the mistake with my first scope and scratched the mirror (though the scratch was very fine and did nothing to the view). A couple of weeks ago I washed the primary and secondary of my 12" flextube - it was about 5 years since last time so I figured they could do with it. I cleaned them the same way I wash my specs every day: under the kitchen tap with washing up liquid, using my finger to rub clean. (Pauses for gasps of horror...) With a cotton wool ball you can probably feel grit down to about a tenth of a millimetre. With a fingertip you can feel hundreths or even thousandths. When I scratched my first mirror years ago it was with cotton wool. Using my fingertip I was left with an immaculate, scratch-free mirror. Some water spots didn't drain off: I used a hair dryer on them, which left a few visible spots when the mirror was held at the right (or rather wrong) angle under strong light. They make absolutely no difference to the views. I'll do the same thing again in another five years. I saw the fingertip approach on a youtube vid a while back and after the initial shock I realised it was the obvious way to do it - I can certainly vouch for it. In the past I've used isopropyl alcohol - and made myself giddy with the fumes. I'll stick to washing up liquid thanks. And by the way, don't forget that all the light from the primary comes to the eye by way of the secondary and eyepiece: the system is only as good as its dirtiest part. That's why I gave my secondary the same treatment. Eyepieces, needless to say, don't get dunked under the kitchen tap...
  2. Glad you liked my post about dark sites Yes, I pack my gear in my car and drive 25 miles to a remote spot down a minor road with almost no through traffic. I chose the spot a few years ago after my previous one started to be encroached upon too much by a light dome on the southern horizon. I found it by looking at the OS map for reachable rural spots likely to have a clear, unlit southern horizon, went in daytime to check it out, and saw there would be easy parking that wouldn't obstruct anyone. Sitting alone there in the middle of the night I feel far safer than I would walking down any city street (though I'm not scared of that either). Primal fear of darkness/ghosts/wolves/psychos soon goes away once you're doing something interesting in a familiar place. Only downside is the investment of time and petrol, and the times when I've driven all that way only to be clouded out. My philosophy is that no one expects to go skiing or fishing or bunjee jumping in their back garden. You could I suppose do snorkelling in a bath tub, but it wouldn't be worth it. Some hobbies necessitate a bit of travel, and I live with that. My one tip: keep all your gear packed and ready in one place, and keep it simple, taking only what you really need. I once got all the way to a dark site only to find I'd forgotten my stool to sit on. Never made that mistake again. I can think of only a handful of occasions when anyone has stopped to ask what I was doing, and of course I was happy to enlighten them. No one has ever given me any problems, and there's absolutely no reason why anyone ever should. If a place is safe and legal to visit in daytime then the same applies at night.
  3. Look through the focuser without eyepiece. Every area you can see should be blackened/shielded/flocked to stop stray light entering the eyepiece. Usually means the area opposite the focuser, top of secondary and interior of focuser tube (and part of the dewshield). I found it led to some reduction of stray light issues on bright targets at my dark site (diffraction spikes were slightly less prominent). No difference on faint targets.
  4. Some reasons why it can be hard to get a scope pointing at the right bit of sky: 1. Sky is too bright (light polluted), so few stars are visible and it's guesswork to point the scope initially at a bit of black. Far easier if you can start by aiming for a naked-eye star and working from there. 2. An inadequate map (too detailed or not detailed enough) so that once you start looking through the finder you can't be sure if you're looking at the star you thought. 3. Inadequately aligned finder. Check it in daytime or with a stationary object at night (Polaris or, *sigh*, distant streetlight). 4. Trying to view objects that are just too faint/difficult for the scope/conditions/observer. Go for things you know you have a real chance of seeing. 5. Failing to match the finder or eyepiece view with the map. Be sure to observe which way stars are drifting in the FOV: they exit at West (like sunset) which is on the RIGHT side of a star map with north at the top. 6. If your finder happens to involve an odd number of mirrors (e.g. 1 but not zero) then everything is left-right inverted compared to your map, which is basically a nightmare (been there and had the headache). A prism (on a right-angled finder) is fine. Here, for what it's worth, is how I do it: 1. Align finder on Polaris. (I use the stock 50mm that came with my 12" flextube and have used the stock 30/50mm straight-through finders on all the scopes I've owned in the last 17 years). 2. Choose target area, examine naked-eye stars and compare with S&T Pocket Atlas. Point scope at a naked-eye star. 3. Compare magnified view with map. Navigate around star, comparing view with map, until absolutely certain that it's correct, and the map is correctly oriented. 4. Get within shouting distance of the intended target. 5. With a low-power eyepiece in the main scope (I use a TeleVue 32mm plossl) and an appropriately detailed map (I use Great Atlas Of The Sky), navigate to the exact target area. 6. Raise power and wait. After about ten minutes a mag 15 galaxy comes into view. Description composed mentally, then dim red light on and write it down. Choose next target (the nearest thing to the one you just looked at, while you're still familiar with star patterns in that area). Alternatively keep buying new gear in the hope it might solve any of the problems listed above
  5. Male-female Newbie-veteran Amateur-professional Moon-haters, moon-lovers
  6. Your conditions are fairly typical for a suburban location. You should be able to see some of the most conspicuous DSOs (e.g. M42, M31, M13, M81/82, Double Cluster...), but less conspicuous Messiers (e.g. M1) will be a struggle while ones of low surface brightness (e.g. M33, M101) will most likely be impossible. To see M31 as anything more than a little fuzzy blob you'll need to get in your car. If you can get to a place where the Milky Way is easily visible with the naked eye then you can be confident of getting good views. That usually means a naked-eye limit of about 5.5 or better.
  7. The cross hairs are much closer to the eye than the virtual images from the mirrors - I can't focus on mine either. It doesn't matter to me since I never use them. For secondary alignment I use a laser, looking down the top of the tube and adjusting the secondary to get the red dot centred on the primary. If I were using the crosshairs I think I'd just tolerate a blurred view and get things reasonably centred: the primary is more critical. If the primary is correctly aligned with respect to the secondary then the only significant "risk" is that the secondary is rotated slightly with respect to the focuser, resulting in a tiny loss of illumination at the eyepiece. If in doubt then do things iteratively: secondary-primary-secondary-primary... until satisfaction, boredom or madness ensue. I wouldn't use a camera to do it for fear of misalignment but if it works for you the problem is already solved. If you really want to see your Cheshire crosshairs in focus then the only solution may be backing away from the viewing hole or else use reading glasses. We all need them eventually.... Incidentally, the "f-ratio" of a Cheshire (length to width) needs to be in reasonable correspondence with the f-ratio of the scope, in order that the whole primary will be visible through it. For a long-focus Newtonian you can use a long Cheshire, and the cross-hairs at the bottom end will be far enough from the eye to be seen in focus. Fast Newtonians (such as my f4.9 Skywatcher 12") necessitate short Cheshires, hence the eye strain.
  8. Possible if you really had a clear horizon but in this case it looks like the setting sun may have been seen through distant trees in which case the "flash" could have been a final glimmer of light through foliage. If it was a green flash it would have looked distinctly green - that's how you'd know.
  9. Why not just use one of those things you see in pound shops for mounting a smartphone on a car windscreen? Or even better, just get used to using the finder - far simpler, not affected by magnetic fields, and won't spoil your dark adaptation
  10. Have you ever wondered what astronomers did before electric lights were invented? A candle or lantern could hamper dark adaptation as much as an LED. William Herschel got round it by dictating observations to his sister who sat inside a lit hut. A later astronomer (whose name escapes me) used the smouldering end of a cigar as his red light.
  11. The Viking spacecraft landed on Mars in 1976 and sampled the atmosphere there. A few years later the same proportions of gasses - a "signature" of Martian origin - was found trapped in microscopic bubbles in meteorite EETA 79001 from Antarctica. It was found there because rocks on top of ice fields are very conspicuous and can only have come from above. There are other ways of identifying Martian meteorites from their chemical composition, e.g. the proportions of different oxygen isotopes, and more than a hundred have been identified.
  12. It was his "last lecture" before MIT disowned him due to misconduct and removed his lectures from their site. They can still be found elsewhere online. https://en.wikipedia.org/wiki/Walter_Lewin_Lectures_on_Physics
  13. Don't get the biggest (largest aperture) scope you can afford unless you're sure you want the weight and bulk that comes with it. You say you mainly want to look at planets, which you can do from a light-polluted site, in which case transportability might not be an issue. But you still need to get it into your garden (if you have one). An 8" dob is a very good all-rounder and very manageable: the Skywatcher 200mm dob is currently £285. The 10" is £429 and is considerably bigger and heavier, the 12" (Flextube) is £529. I have the 12" and use it for deep-sky viewing at my dark site, but it's not for the faint hearted (and not great on planets - my Orion 8" dob was better). If you aren't so interested in deep-sky and really want to concentrate on lunar/planetary you might want to consider a 4" refractor of superior quality: I'll let others recommend one in your budget. Similarly you might want goto, tracking or other frills, which I can't comment on. Edit: previous post crossed with mine and looks a good refractor suggestion.
  14. Ursa Major. Huge (third largest after Hydra and Virgo), visible every night of the year, and packed with DSOs. There are 510 NGC/IC objects in Ursa Major; the only constellations with more are Cetus, Coma Berenices, Leo and Virgo - of which I'd say only Cetus is arguably under-rated. The constellations with fewest NGC/IC objects are Musca (9), Corona Australis (8), Crux (8), Sagitta (8), Chamaeleon (7) and Circinus (5). Sagitta does contain a Messier object though (M71), and is the third smallest constellation (beaten only by Equuleus and Crux). Bootes, incidentally, has 493 NGC/ICs - so I disagree with the previous post!
  15. Names are useful as long as there's only one name per object and everyone agrees on the name. For example, does the "Pinwheel Galaxy" mean M101 (as it usually does now) or M33 (as it did previously) or M99 (which was the first to get the nickname)? Should we call the Owl Cluster the ET Cluster, or the Phi Cas Cluster - or should we call it NGC 457? That's why catalogue numbers were invented. There are so many things up there, it's impossible to remember the name of everything. But agreeing on names makes the task easier, and catalogue numbers (M, NGC etc) are the names with widest agreement. The internet has produced a deluge of new nicknames - making it all the more important to preserve Messier and NGC numbers, so that we all know what we're talking about. No need to remember everything - that's what notebooks are for.