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Ben Ritchie

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Everything posted by Ben Ritchie

  1. He taught me spectroscopy when I was an Astronomy undergraduate, and was a terrific teacher. Nice to see he has kept busy
  2. Interesting! I'm on the original list (signed up in either 2000 or 2001, and long since gave up hope of ever getting notified for a Stowaway or a 160EDF) so fingers crossed I might get lucky - would be a very pleasant surprise!
  3. Low-power browsing with a 2" eyepiece should be a natural use-case for it, but there are some slight frustrations - it's very focuser-heavy and hard to balance with a 2" diagonal and a heavy 2" eyepiece, as the short dovetail doesn't give much room for adjustment. I find mine a bit easier with a lighter max-FoV 1.25" eyepiece (I have a 24mm Meade SWA, but a 24mm Panoptic would be great too), and that seems to be a good combination and gives wide fields with less weight. Haven't had time or clear-enough skies to really test mine out properly - only arrived from FLO a couple of weeks ago, and life's been busy! - but first signs have been pretty positive, and i'm pleased with the purchase.
  4. Evening folks. I have a Tele-Optic Ercole which, until recently has been living happily on an EQ6 tripod (the EQ6 itself is in my observatory). I'm now planning on upgrading the observatory mount, which means the EQ6 will need its tripod back, so wondering what else people use with the Ercole? Would be used mostly with my Astro-Physics 130EDT, which is a pretty big and heavy refractor - the Ercole handles it quite happily with a couple of counterweights and the EQ6 tripod, but wouldn't really want to go for anything substantially less robust.
  5. Interesting thread. I'd certainly echo this what you get for your money has jumped massively right across the board in the last 15 years or so. To me (as a die-hard refractor fan!) the revolution was possibly the arrival of affordable apochromats, mid-90s were very rare and if you did come across one they were often things like the Meade ED f/9 doublets which were fairly marginal apochromats at times, and the arrival of the blue-tube 80ED for a couple of hundred quid was a huge change. But affordable super/ultra/etc. eyepieces and the unrecognisable changes in imaging from film and massively expensive, noisy, and small-chip CCDs to what's available now are also huge, huge changes. Glad it's still going strong, although to be fair it's at least third hand as it wasn't new when I got it. Still miss it though
  6. Ditto - think the EQ6 is definitely the mount of choice unless the additional cost and weight is a factor. I've used my C9.25 on a HEQ5 too and to me it's fairly marginal, especially if you have anything else bolted on. I replaced the original Vixen dovetail on my C9.25 with a Celestron's orange Losmandy one (very easy to swap over) and it's a decent improvement in rigidity.
  7. Nice! I had a TV60is once which was a terrific little telescope, tiny but built like an absolute tank. One of the ones where I wish I'd never parted with it
  8. As an example of the load-lugging capability, here's mine with a C9.25 and 100ED, and it works very well in this configuration - smooth and well damped.
  9. I owned one for a couple of years, and would agree with this Mine needed a fair bit of tweaking to deal with the infamous 76-second error, out of the box it was a bit of a disappointment for imaging but ultimately was very good once I got the worm gear sorted out (and then I sold it to get an AP 1200GTO ). Visually it was fine though, and Gemini is very good, particularly once you've done a few iterations to work through polar alignment and enough reference stars for it to build a decent pointing model. Once you've done that then go-to was bang on for me right across the sky. The Gemini handset feels very old-fashioned though.Personally i'd recommend one at the right price (in fact, i'd buy one again myself at the right price!). But you do need to tinker to get the best if you are an imager. edit: one more thing, accessories are very expensive and usually out of stock (or, at least they were when I owned one) so worth looking for one packaged with the bits you need - typically an extra counterweight or two, the clutch knobs (a big improvement over the basic set), and pier adapter if you're mounting it in an observatory.
  10. I have an Ercole, it's a very solid mount on an EQ6 tripod. Tracking is very smooth, at higher powers there is lots of nudge-nudge-nudge as you'd expect, it doesn't bother me at all although in general I favour lower powers anyway so don't do an awful lot of high-power work with that setup. Only downside to me is that although the list price isn't that bad, you just get a bare mount - saddle(s), tripod, and counterweight bar/counterweights if necessary inflate the price substantially. In particular I wouldn't want it on much less than an EQ6 tripod, so if you're going completely from scratch then the final price ends up quite steep.
  11. That's the one - looks like the seller put it in the wrong place on ebay (Cameras & Photography > Lenses & Filters > Lenses). I'd reckon they're still worth the better part of £100 today so you did get an incredible deal, well spotted
  12. Is that the flat-top version? When I owned one they were changing hands for nearly £200, so 99p is an absolute bargain indeed. Very much an old-school eyepiece, but I loved it - big and heavy, but a great vintage charm to it. Because you could see the top of the eyepiece (no eyeguard) it kind of felt like looking through a ship's porthole. Back in the day it was considered to give the TeleVue equivalents (e.g. the 13mm 'type 1' and 12mm type 2 Naglers) a decent run for their money, and I certainly ranked my one close enough to that benchmark, although eyepiece design moved on and it was left behind by newer eyepieces from TeleVue, Pentax, et al. I'd still pay a lot more than 99p for one
  13. The H-alpha filter on VLT/FORS is 0.6nm, and I think that's fairly typical for service mode filter on a professional instrument - that allows you to split H-alpha from the [N II] doublet at 6548/6582 angstroms, whereas even a very good 3nm filter will blend them.
  14. Not sure what you mean? H-alpha is in the red, H-beta is blue/green, but you usually map narrowband to RGB channels which don't necessarily match their natural wavelengths (e.g. in the Hubble palette the red H-alpha line gets mapped to the green channel). I think you mean creating a false third channel? [O III] (not O111, by the way) doesn't really have much to do with H-beta emissivity, so H-alpha + [O III] doesn't directly correspond to anything as such (although arguably H-alpha coupled to gaussian noise would correspond to H-beta). The H-beta line is effectively H-alpha with a third of the signal due to the reduced emissivity (based on the tables in Astrophysics of Gaseous Nebulae and Active Galactic Nuclei). Doing H-alpha/H-beta/[O-III] doesn't make much sense as two Balmer channels trace the same material but at different signal-to-noise.
  15. H-beta emission traces the same material as H-alpha but with about a third of the emissivity as the Balmer beta 4-2 transition is weaker than the alpha 3-2 transition for almost all conditions you'll encounter. One advantage is that the H-beta line is in the blue/green, so you can capture signal with sensors that have very poor red sensitivity (which would also be no good for [s II], which is slightly further red than H-alpha). But if red sensitivity isn't an issue there's no sense in using H-alpha and H-beta.
  16. This sounds like collimation, but can be atmospheric or (lack of) cool-down - if the seeing is poor or the telescope hasn't cooled down to ambient then stars can appear soft even if the telescope is in perfect collimation. There's not much to suggest here other than practice, the Cheshire is a good option IMO and at f/6 the 200p shouldn't be too demanding This isn't a collimation issue, just that the finderscope isn't aligned with the main tube.
  17. I have the traditional set of a BSc/MSc in Physics with Astrophysics and then a PhD in Astronomy, although my PhD work was all theory (N-body/hydrodynamical simulations of galaxy clusters) whereas my subsequent research is observational astronomy, mostly using ESO's VLT. To be honest most observational stuff isn't very maths-heavy at all, not much more than typical undergraduate-level statistics.whereas theory and numerical modelling is generally intensely mathematical. I think this is good advice; my wife, who is a university reader in music says the same about her field too. If you want to do research then a PhD is essential, both for the training to professional level and for gaining the contacts and link necessary to run a research programme, but once you have it it is certainly possible to do top-level research outside the standard postdoc/lecturer route if you want to. A well paid day job and research as a 'hobby' makes a lot of sense these days. The RGO was great, I was a summer student there before it closed.
  18. I have the Ercole, it's a very nice mount. I still need to pick up a counterweight, but once I have that will try my C9.25 and report back
  19. They charged me £15 to Sussex and it arrived with one second-class stamp on!
  20. You don't need accurate alignment for visual, a rough alignment with the polarscope is certainly good enough and takes less than a minute to do but I often used to use a HEQ5 by putting it down facing roughly north (my garden is east-west, so I pointed the 'north' tripod leg at the fence - would guess that I was within 5-10 degrees) and then one-star aligning it. There was some minor drifting, but really not much of an issue to correct with the handset. Autoguiding would be far more hassle than that with the extra kit and cables if you are setting up and tearing down each night (you say you don't want a laptop, but most use one for PHD guiding or equivalents; guess you mean the stand-alone ones then? they are laptop-free but quite a bit more expensive, and harder to use IMO) and generally you do a decent polar alignment before guiding anyway. edit: forgot to say that what i'd do is spend a bit of time tweaking your setup routine to make alignment easier for visual, once you are used to it it really shouldn't take more than a few minutes to get 'good enough' - what telescope are you using? Is it long focal length that shows drift more easily, perhaps? Many of us mark out where the tripod legs go for reference, which gets you close from the start. A friend of mine has done it very subtly with a couple of triangular patterns in brick on his patio - only a backyard astronomer would spot that they're in the right place for the legs of an EQ6 tripod
  21. I suppose it is fairly simple, which is why you can buy a decent 80mm apochromat for a few hundred quid, even after it is shipped across the world and various importers and dealers take their cut. A decent 80mm achromat costs substantially less than that - a Vixen 80mf is £150 with rings, eyepieces, diagonal, and finderscope, and it's a fine double-star telescope, no shoddy optics in the one I had As you head to the high end, you're paying for better colour correction out in to the near-UV and near-IR, which doesn't matter too much to visual folk but matters a lot to imagers as a CCD can 'see' those wavelengths far better than the human eye. You're also paying for better quality control (the 'ones they didn't ship' as well as the ones that did), and you're paying for the lack of volume as the market for a £1k+ 80mm refractor is presumably tiny.
  22. Here's a nice example slightly edited to remove counts to hopefully make it a bit clear - the important bit though is the background can be far larger than the source signal
  23. I've used VISIR on the VLT, which is optimised for two mid infrared (MIR) atmospheric 'windows' between 8 to 13μm and between 16.5 and 24.5μm. That's at 2600 metres in the Atacama though, so far better conditions than you'd ever get in the UK. There are technical challenges too, once you're in the thermal infrared you have to remember that both the atmosphere and the telescope itself are strong emitters at around 250K; it's roughly equivalent to trying to image in the optical during daytime with a telescope made of bright luminescent panels and a reflective but luminescent mirror. There are specific techniques to help deal with this ('chopping and nodding', for one) but it's rather different to optical imaging
  24. Thumbs up for Rupert at astrograph.net from me. Very quick and helpful exchange of emails when I was looking for an alt-az mount, and two orders were received very rapidly.
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