billyharris72

Hi all. I'm trying to get my head around this, in the context of stellar physics, and how stars emit both thermal and line radiation. Most of the books I've read seem to cover electron energy level transitions and then talk about thermal energy and black body radiation as if there is no issue to explain as to how one turns into the other. I get the idea of electron energy level transitions, and (to some extent) of collisional line broadening, but I'm struggling to get my head round how these quantum energy state transitions relate to the translational (kinetic) energy necessary to raise the temperature of a gas. Presumably this has to happen or the gas in stars would not get hot. I've seen an explanation on physics stack exchange that suggests that, with the electrons in a higher state, interactions with other molecules become more likely and that kinetic energy can be passed on that way. But what happens in this process - does the electron de-excite without emitting a photon? If not, where does the energy that is passed on come from? And are photons emitted by atoms in other ways (e.g. does the translational acceleration of the atoms release photons, in a way similar to braking radiation)? Also, are there other ways a photon can heat an atom or a molecule? The same stack exchange thread has a post that suggests that radiation cannot directly heat a gas molecule. I could see (from the above discussion of energy levels) that such a mechanism might not be necessary, but what about cases like co2, where infrared imparts energy to an oscillating dipole? This doesn't seem to involve energy level transitions at all. Presumably, for that matter, neither does transmittion of photons through the at least the inner part of the radiative zones of stars, as it's presumably all plasma at those temperatures. Struggling a bit with this one. Any help (or suggestion for not-to-advanced reading) much appreciated. Thanks, Billy.

I don't use automatic platesolving that often, but when I have I've used the built in functionality of AstroArt. Overall I've found that to work reasonably well, though Astrotortilla looks to be more powerful. You can also set up Astrometry.net to run locally, though I have not had any joy with that. Billy.

Oh, that's not so good. Not having one of these scopes I don't know if it would reach focus, but it does sound like quite a bit of extra travel. I suppose the other option might be to move the mirror up the tube a little. Billy.

If the sensor needs to be further out then it shouldn't be a huge problem - it's when it needs to go further in than the focusser allows that the problems start. If it won't reach focus a T2 extension tube should get you the extra distance you need. How big is the chip on that camera? Coma will be pretty significant at f4, but won't affect objects in the centre. Billy.

It really depends what youre looking for and at what kind of level. For a gentle but broad and pretty comprehensive introduction to astronomy with minimal maths, Dinah Moche's Astronony: a self teaching guide is great. Ian Morison's Introduction to astronomy and cosmology goes a bit deeper and is another book I'd recommend highly. I've recently picked up a copy of Fundamental astronomy, edited by Karttunen at all. From an initial skim it looks fantastic, but doesn't hold back on the maths. Its not massively complex stuff, but you definitely need to be reasonably comfortable with calculus. There are also four OU textbooks that look good, and are a bit more gently paced than the previous. An introduction to the sun and stars is definitely worth a read. Hope this helps. If in doubt I'd start with Moche - it's a great book. Billy.

I bought a dedicated observatory tent, and have to say I was not impressed. It was okay once set up, but the construction was very flimsy. The design was really poor, putting way too much pressure on the fibreglass poles. It broke the second time I set it up and was swiftly moved to the bin. Not one of my better investments Personally, I'd stay clear of something marketed as an observatory tent unless I'd actually seen it with my own eyes. Billy.

More confusing to me is Edgar Allan Poe. A man passionately interested in science (Eureka is all over the place but you can't deny his interest), arguably the inventor of science fiction (we'll leave Kepler's Somnium out for now), author of a prose poem in praise of Humboldt. And author of this (warning: what follows is not great). Sonnet - to Science Science! true daughter of Old Time thou art! Who alterest all things with thy peering eyes. Why preyest thou thus upon the poet’s heart, Vulture, whose wings are dull realities? How should he love thee? or how deem thee wise, Who wouldst not leave him in his wandering To seek for treasure in the jewelled skies, Albeit he soared with an undaunted wing? Hast thou not dragged Diana from her car, And driven the Hamadryad from the wood To seek a shelter in some happier star? Hast thou not torn the Naiad from her flood, The Elfin from the green grass, and from me The summer dream beneath the tamarind tree? Never got my head around this. Billy.

I'm not sure on this poem - it could be taken as part of the old "two cultures" dichotomy (okay, I admit, it definitely is), but it's not that bad. I didn't take its main thrust as astronomer bashing but as pointing to difference between the (interesting, valuable, fascinating) world of astronomy (done mostly in offices, lecture rooms and these days computer labs) and the experience of just looking up (from a body, on a moist evening, with human eyes) at the night sky. I'm not convinced that human endeavour since Copernicus has added to the fundamentals of that experience at all. Ignorance might not be bliss, but neither is knowledge; bliss is just looking up. I like both, for what it's worth, but I can understand from my time in academic and other analytical pursuits the idea of being tired and sick, even with subjects that fascinate me. Billy.

Glad you're enjoying the scope - I think at that size there isn't a better scope on the market, at any price (happy to be corrected if anyone has one). The price being riduculously good is an added bonus of course. You're right about aperture, and this is why, if you do want a significant upgrade, you will need to bite the bullet on size. There just isn't a better option that isn't significantly bulkier. To see a real improvement over what you have I'd skip the 150 and go straight to 200mm in a Newtonian (where a Dob is the easiest option). They're a bit of a faff, but surprisingly portable when you get used to it (at least for back garden use or car travel - I wouldn't go hiking with one!). A Schmidt or Maksutov cassegrain could be a less bulky alternative in terms of the tube, but you'll lose both field of view and (a little) in terms of optical performance (again, skip the 150mm - the 130 Hertiage is optically the equal of Skywatcher's 150mm Mak even on planets, and is better on everything else). Also, by the time you mount it it's not really less bulky. I'd say the same for a refractor - you'd need at least a 120mm ED, to equal or surpass the Heritage, both bulky and expensive. If it were me, I'd consider a bigger Dob or sticking with the (very capable) scope you already have for now. In terms of a present that is astro focused, what about a good set of binoculars? Billy.

If you're looking for a course of action you could do worse than check out if there are any astronomy clubs in your area. The chance to talk with others, learn from their experience and try out different types of kit can be invaluable. Billy.

I agree. Despite occasional gripes it's my firm belief that the Moon is, on balance, a good thing. Like the pic! Billy.

I've decided to thin my collection of underused binos, as I mostly only use the Swaro ELs these days. So the following are up for grabs. Helios Apollo 15 x 70. A good binocular by all accounts but being an astigmatic spectacle wearer i never got on with them. Supplied with case and tripod adapter. Looking for £190 + postage, or pick up locally (anywhere between Cardiff and Bristol). Opticron Trailfinder WP3 8 x 56. I've always really liked these but the Swaros have made them rather redundant. Slightly narrow FOV (6 deg.) but great eye relief and very nice view across the whole field. Looking for £80, again plus postage (or collect / deliver locally). Cheers, Billy.

Follow up pic as suggested in the forum sticky. Billy.

For sale, one Skywatcher Startravel 80mm. Good condition. Focuser has been tightened to remove slop and lens edges blackened. OTA supplied with tube rings that came with it, 6x30 finderscope and 90 degree mirror diagonal. Asking £60 plus postage (TBC), or collect locally (Chepstow area, can travel to Cardiff or Bristol). Regards, Billy.

2mm is a fair bit, but I wouldn't worry about it unless it is actually causing problems in use. If you want to try tightening it up the best resource is probably. http://www.astro-baby.com/heq5-rebuild/heq5-we1.htm Hope this helps. Billy.