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billyharris72

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About billyharris72

  • Rank
    Proto Star

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  • Gender
    Male
  • Interests
    Astronomy, climbing / mountaineering, chess
  • Location
    St. Arvans, Wales
  1. I'd tend to agree with Ricochet. Personally, if your budget is under, say, £40, I'd recommend Plossls as by far the best option. While the field isn't wider than the stock eyepieces, optically they are pretty good. That includes the Skywatcher ones, which are pretty cheap. The only thing I'd add is that a 4mm Plossl is not a particularly comfortable eyepiece to use - eye relief is pretty tight even without glasses. I have one (a Celestron Omni) and quite like it, but it takes getting used to. With that in mind, something like a 32mm, a 9mm and a decent Barlow lens (the Celestron Omni is good for the money), while it will set you back a little more, would be a pretty good set of eyepieces. Might be worth checking out what they have on the Astroboot website - they often have Plossls on there at good prices. Best of luck with whatever you go for. Billy.
  2. From the BBC website (science pages): "Skywatchers have been treated to the first full moon of 2020 - known as a "wolf moon" - at the same time as a lunar eclipse."
  3. Good choice. My final setup for grab and go with that scope (which I still regret selling) was the OTA on an AZ4. Portable and absolutely rock solid. Another option is buy a cheap second hand set of tripod legs from somewhere like AstroBoot and just bolt a sheet of plywood on top to make a collapsible plinth for the Dob base. Works well and should only set you back about 30 quid.
  4. The heritage is actually easier to transport - it can be carried in one hand, but you're right about wanting something to put it on. Something like a 3 legged stool would do the job okay though and would not be too much more to carry.
  5. I'd agree with banjaxed. While I don't think equatorial mounts are all that hard to get your head around, the lighter models are often not great. The EQ2 may not be all that stable. I also think the EQ scope you're looking at may have a spherical mirror - not the end of the world, but not as good optically as the Heritage, which is a great scope. What is it about your site that makes you think it may not be suitable?
  6. Have you considered making your own dew heater? I have major issues with dew on the secondary, but loop of resistors drawing around 2 watts, wrapped in shrink tube and attached to the back of the mirror with electrical tape, solved the problem. Going the DIY route also let me use finer wire, so there is no real impact on the image. I imagine something similar could work for the primary? Billy.
  7. Hmmmm, point taken - that's nice! Makes me wonder if I've got something else wrong with my setup. I seem to be able to go both sides of focus, so it's not that, but have bloated stars in luminance and in blue. We're talking really bad here, like a blue fuzzy ring around each star. Removing it in processing leaves the stars looking almost white. I fitted an additional Astromimic UV/IR cut filter, a bit more aggressive than the stock filters. That cleans it up quite a bit - but now I seem to have the focus issue you mention. Only way to get focus is to put the flattener way too close to the chip. Wonder if it's just a QC issue. Billy.
  8. With an unmodded Nikon DSLR you should be fine with the 72ED, and it'd be a good match for the mount in terms of size. It struggles badly with RGB filters on a mono camera (below about 420nm it just doesn't focus), but the DSLR will not suffer excessive chromatic aberration. On the other question, it depends what lenses you have. With an 0.85 focal reducer/flattener you will get 357mm at about f4.9. Having used and compared a budget (c. £80) Sigma 70-300mm zoom at f5.6, my money would be on the Sigma. Yes, the zoom bit and the less than friendly manual focusser are a pain, but optically it's clearly better. Economies of scale - can't beat em! Billy.
  9. Interesting, and makes sense. I've tended to the exact opposite (pointing up) but down does seem much more stable thinking about it. That might even work with the guidescope setup, as it would be opposite to the guide. I'm really tempted by an OAG though. Do you use one with that DSLR? If so it should cover my chip no problem. Billy.
  10. Hi all: I've struggled a bit with getting a guidescope to work well with my 130 PDS/ HEQ5 setup. I've used three arrangements (all with a 120m as the guide camera). 1) QHY 30mm f4 guidescope, mounted in the finder shoe. Works well, but is a little short so pixel scale / performance could be better. Probably the best setup so far. 2) Skywatcher 50mm ED in the findershoe. Impossible to balance the scope in DEC with this setup - massively front heavy. I suppose I could put a counterweight of some sort at the back. 3) Skywatcher dovetail bar on top of the tube rings with an ADM clamp and the 50mm guider mounted on that. Worst setup by far - just terrible. First, it flexes. Second, the guidescope points straight at the camera unless I rotate the scopein the tube rings so it is out of the way. The scope is now out of balance in DEC (put it in parked position and loosen the clutch and it will move in the direction of the camera). Of these, option 1 is certainly bearable, and one improvement might be to try a guide camera with smaller pixels (maybe the ASI290MM). The other option I was considering was using an OAG. It would probably be the lightest and tidiest option, and it's cheaper. Does anyone out there have any experience with this combination? My main concern is with the illuminated field of the PDS. Will it be possible to illuminate the guide camera without having the prism protrude into the main imaging area? Thoughts and experiences much appreciated! Billy.
  11. My 2p worth - I'd probably go for the 102. As you've said, it's a very compact instrument, light and portable, and still quite capable. More aperture is always good, but it is at the cost of bulk (not that the 127 is exactly huge, but the planned mount is lightweight). On quality, from experience with the 102 and the 150 Maks, Skywatcher can say what they like but mechanically and optically these two scopes are really very similar. There is not some kind of quantum leap in quality once you go above 102mm, just more light grasp (and the ability to use a 2 inch diagonal on the larger models). Optically, I'd say both are decent scopes, but not great - an f12 or f13 Gregory Mak is fast for that design - it will suffer residual spherical aberration, and it is obvious on both the 102 and 150 SkyMax at higher magnifications (c. x200). Neither will outperform a half decent Newt (including on planets or double stars) but there is not much of a loss and the ergonomics of these little scopes are fantastic. The slightly slower f ratio on the 102mm might actually play in its favour. I have not checked the baffle tubes on these scopes but have never felt the need to, as I've never had an issue with stray light. That said, I have (like kappy-kat) heard good things about the advantages of flocking the baffle tube, and my one look through a C90 with internal flocking was very impressive, so maybe there is room for improvement there. Vignetting should not be an issue with a small chip. At prime focus both scopes cover a whole Nikon DX (15.8 x 23.6 mm) chip. Light fall off towards the edges is easily corrected with flats. Cheers, Billy.
  12. I think this sounds like a great setup - probably the most common "beginner" astrophotography setup there is these days, and for good reason. The other option (maybe a little more demanding, but with more light grasp, tighter stars and actually less expensive) is the 130 P-DS. To be honest, there's not much in it, and the 80mm ED is by all accounts a keeper. It involves a lot less fiddling around in the dark than a Newt. On the 72ED, I have one and have to say I'm retiring it as an imaging scope. The thing can't focus blue light. It's fine with an unmodded DSLR but on a mono rig the levels of CA are totally unacceptable. Add that to focus slop and a lack of in focus and to me that scope is just a dead end for imaging. That said, I may have a bad one, but I've not been at all impressed. Billy.
  13. Hi Paul. I have the 300mm version of this (bought secondhand from Mr niall) and have been very pleased with it. I'd answer your questions as follows (as always, YMMV). Setup time for me is about 5 mins. I take the scope out in two pieces, put the tube on the mount and that's it. It can be taken out in one, but its heavy and better as a 2 person lift. You'd want to allow another 5-10 minutes for collimation, but do this after cool down. Cooling time will depend on what you want to observe. For planetary or double stars (you have a 120ED, so the use cases where the Newt would give any advantage are limited) you'd want to leave it a good hour, but for use at the lowest powers on fuzzies or wide-ish field half that would be fine - there's nothing stopping you using it right away, but this isn't really a "quick peek" or a grab and go instrument anyway. Portability. Pretty bad unless you have a decent sized car and don't plan on moving the scope far from the car. Though a trolley (or observing partner) could make this easier. I never move the thing more than about 20 metres from where it lives in the conservatory, nor would I relish doing so. It barely fits in my Toyota Yaris, but a larger car would handle it okay. Overall quality. Good - in fact really good. With an ES 34mm ep stars are pinpoint over about the central 2/3 - the rest shows moderate coma consistent with a 12 inch parabolic mirror; this could be cleaned up with a coma corrector (or you could put what you're viewing in the centre of the field!). Seems to cope with higher mags well, though with the low position of the planets I've not had occasion to push it. Overall, I've been surprised by just how good the scope is optically. Mechanically I've no quibbles either. The focuser is okay, provided you don't mind single speed, and everything is rigid enough. You'll need to collimate the primary each time (no getting round that with a 12' Newt) but the secondary is stable even given the flex tube set up. Overall, I'm very pleased with mine. Hope this is a help. Billy.
  14. 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.
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