allworlds

Well now you've made me want to figure that out. For a singlet lens the radii of curvature are quite easily related to the focal length. Guessing a refractive index of 1.5 and assuming it's a symmetric lens, the radii of curvature end up equal to the focal length actually. https://physics.stackexchange.com/questions/168749/radius-of-curvature-and-focal-length Using the equation for a circle y^2 = r^2 - x^2 1/3 foot away from the centreline of the 122 foot focal length the lens edge is 0.00046 feet lower than the centre. That's about 5.5 mils. I wonder how Huygens measured it? Or maybe he didn't exactly - maybe he just ground lenses and saw what focal length he got?

Nothing right now. Every pair of bins I’ve owned - and OK they were all cheap ones - has gone out of collimation and I don’t feel confident trying to fix it. It had me seriously considering a monocular just so that doesn’t happen, but I do prefer the two eye view when it works. Wondering about going 8x40 for a bit less weight and shakes. The cheap “10x50” I had before were internally stopped to 40 mm anyway.

Mars in lousy seeing, but I made out a roughly triangular dark feature central-ish. Which is the first time I've seen any detail on Mars, so that's something.

What’s missing? If it’s eyepieces, new ones are better anyway. Same arguably for the finder. While the Astromaster’s not the best scope around, anything better will cost a lot more than a hundred quid.

I'm not sure if Huygens's 120 footer was an aerial telescope or not. He also made what he called "tubeless" telescopes - what we would now call a truss-tube, of sorts. There is a drawing of Hevelius's 150 footer, https://commons.wikimedia.org/wiki/File:Houghton_Typ_620.73.451_-_Johannes_Hevelius,_Machinae_coelestis,_1673.jpg That's what you had to do to get the chromatic aberration under control before achromats were invented. Or you could build a reflector - with mirrors that were about 66% reflective at best and needed the tarnish polishing off every few months and after you do that a few times you've wrecked the figure.

My experience is with smaller scopes, but some of the things that worked for me: Get properly dark adapted which means getting away from nearby lights. You can't do much about general LP except travel a considerable distance away. But you don't want streetlamps, neighbours windows, insecurity lights, and so on shining on you or the ground around you, that will kill your dark adaptation. In a city this can be difficult and is why I quit observing for a while. Opaque screens might help. Precise and methodical star hopping with good charts. Low-depth charts and instructions like "find these stars then go three times further", that involved panning multiple fields of view with little guidance, never worked for me. I needed more detail in my hops; the next star either within the same field of view or just a little way outside it. You can set up your telescope and eyepieces, magnifying finder, or Telrad in Stellarium's "oculars" setting. On computer; not sure about the phone app. You can then use this to rehearse your star hops virtually. Be sure to set the light pollution setting in Stellarium to something about right. (I usually make the computer program a *bit* better than my depressing city skies, but I don't have it set to dark-sky-site levels.) General observing skills, averted vision and so on, which really just come with practice.

Venus is the goddess of love and it turned out to be the most hellish place in the solar system. I doubt that's what the Greeks and Romans had in mind.

My new-to-me ETX 105 has a busted Az/RA drive. Motor whirrs but mount doesn't move. I popped it open to have a look and a part of the gearbox housing has broken, causing the gears to misalign and be disengaged. Does anyone know either somewhere/someone who can repair these, preferably in the West Midlands, or where I could obtain spare parts. Meade UK don't seem to have it, they have the gearbox for the smaller ones but not the 105, https://www.meadeuk.com/Meade-Spare-Parts.html

That's painful, but remember scopes are for looking through not looking at. There's that one professional telescope with half a dozen black circles on its main mirror - bullet holes. Louis D, you say that, but ENS Optical is selling a 6 inch Mak with a whacking great chip in its corrector. (Selling it very cheap, of course.)

Not great conditions, lot of thin cloud and gaps, but broke the 105 Mak out anyway. Viewed Jupiter and saw the Great Red Spot clear as you like, first time I have. Quite distinct shading on the north polar area too. But generally not as much crisp detail as I saw the other day. I didn't bother to let the scope cool properly which won't help. Found Uranus despite not having a finder on my scope right now. Helped that it was near the Moon and there's a distinctive three-pointed asterism pointing the way. And a bit of lunar. A crater with a distinctive line from centre to rim stood out - Petavius I believe.

Any would be a good choice. The Heritage 150P is probably the cheapest and is highly portable. The Skymax 127 can also be highly portable with the right mount and tripod but is the most expensive of the three (and if it's brand new I expect it's either over budget or under mounted). A good Mak-Cass is an excellent lunar and planetary scope, I have a smaller one that impressed me, but it won't do wide field and it gives up a bit of aperture for deep sky. The XT6 is arguably the best all-rounder of the three but it's a bulky thing to move around - easily transportable by car but not very practical to take a long distance on public transport, two wheels, or on foot.

http://60mm.free.fr/en/l60_deep_sky.php Might be useful? Although you have a Mak-Cass rather than a refractor it’s very similar in aperture, focal length, and therefore capabilities. 2 1/2 inch fracs were a classic “starter scope” so there’s a fair bit on them. I’d try for some open clusters, they can do nicely in a small scope. Perseus and Cassiopea are well placed in the evening and have some.

Both. But assuming you want to buy one first, that’s harder. The 8 will be your high power eyepiece for planetary viewing, the 12 more of a medium power. I’d say get the 8 but that does leave you with a large magnification gap, but you can buy the intermediate powers later. Edit: Next time I get out with my similar scope, I’ll ask myself how badly I’d miss the high power.

I went to buy a Skymax 102, it was out of stock on FLO, ordered from Harrison, they refunded because they were out of stock too, other places were either out or didn't have live stock info. So I put in a lowish bid for a Meade ETX 105 on eBay, thinking it would probably go for more, and only ended up being the winning bidder! First light was just now. The good: The lunar and planetary views are crisp and sharp and wonderful and everything I wanted. The NEB on Jupiter had little waves and filaments, there was a bright zone just south of the SEB, all the kind of stuff I couldn't have seen before. I don't have a clue what's what on the Moon but craters stood out so sharply. Saw Saturn (and Titan) but it was low and the seeing seemed iffy. I don't really know how to star test but Vega showed diffraction rings and I guess they looked centred? No deep sky yet, not with tonight's near-full Moon. I got it in an enormous and very well padded hard case, but if I get a smaller bag that's still adequately padded it'll fit nicely in my bike's rear basket. The bad: The finder is in a stupid place. It works well enough as a finder (8x25 right angle, kind of cute) but gets in the way of my nose when I try to use a short eyepiece. I ended up breaking out the Barlow just so I could get some more physical distance from the scope. Quikfinder or Telrad on my shopping list I think. The Autostar controller's display ghosts worse than an original Gameboy, I actually thought it was broken at first until I slowed the text scrolling speed way down, and it's kind of sluggish in general. I guess that's state-of-the-noughties computers for me. The ugly: When I powered up the mount it would slew left, but trying to slew right gave a horrible noise and a weak jerky motion. After turning it off and on a few times and playing with the clutch a bit the azimuth motion is completely busted, the motor whirrs but the scope doesn't move. (So I never actually got to test the sky alignment and goto). So it's a manual mount until I get that fixed. It's usable enough manually, same as the Heritage 76 pretty much, maybe a bit more trouble in the alt axis.

Proper astronomical telescopes have aperture and focal ratio (or length) as their main specification, not aperture which in any case depends what eyepieces you use. (Spotting scopes are usually specified like binoculars, lowmag-highmag x aperture.) So what you state isn't promising. And the only reason I can think that the "terrestrial magnification" would be different would be the use of an erecting eyepiece, which is something some infamously bad telescopes do.

Moon first, pushed the Heritage 76 to 100x on it. The wind was sure up sometimes, the little Heritage rarely shakes but today it did in the gusts. Tried my hand at photos holding the smartphone to the eyepiece but the result was pretty lousy. There's an area around the terminator that caught my eye when viewing, looks like a valley (anything that's not a crater will catch my eye on the Moon!), it shows up much better on your image above but I don't know if it has any name? Had a go at Jupiter but nothing special there. 100x is too much on it, lower power does better. I think I saw it better the other day. Missed out on Saturn, trees were in the way. Saw possibly my least impressive view of M31 ever, really not the conditions for it but I thought I'd look at something deep sky anyway. Found the Coathanger by accident and rounded off with a quick look at Albeiro.

I do wonder about a premium Dob for OP. Something that's optically and mechanically a cut above the usual Skywatcher ones. Or perhaps an ultralight one. I'm not sure what good ones are available in the UK though. If diffraction spikes are bugging you curved spider vanes are the solution to that - this can be done as a modification if it's not factory supplied. Not much good for imaging, though planetary is possible with an EQ platform.

Nicely done. Yeah I remember from some other observing that stuff in the sky often seems higher than I expect. So far the only time I've seen Mercury was in one of the transits though.

When you don’t wear your glasses, are you wearing nothing, or are you wearing your contacts? It could be down to differences in your vision in bright and dim light. IIRC some glasses-wearing astronomers get eye tests and glasses done for their night vision and it might be a different prescription to daytime. Could be the Travelscope’s chromatic aberration making its focus less precise? It could be that you are focusing differently. The telescope focuser enables you to make an object look like it’s closer than, at, or beyond infinity in terms of how your eyes (with or without glasses) focus it. Maybe by day you’re focusing the objects so they look like they’re near (in focus terms, not the magnification). See if you get different results depending on whether you start with the focuser retracted and extend it until you reach focus, versus starting extended and retracting it.

You mention "quality" a few times. Do you want to see more - fainter things, finer details? Or do you things to look better but you don't necessarily see more - clearer contrast, pinpoint stars? Two slightly different things. Seeing more means getting bigger aperture pretty much - and your weight requirements constrain that - but a better quality of view could be given by the right scope at a similar aperture. I think really what you want is a whole fleet of "next telescopes" though.

For some reason whenever I subscribe to any magazine, it usually ends up dropping through the door and I ignore it. That's happened with a fair few I subbed to. But if I buy one in a shop I read it. I've picked up both S@N and Astronomy Now before, and probably will do irregularly in future. I've heard good things about S&T and Astronomy but don't know where to buy them in the UK. (And I spend too much time in front of a screen so I kind of prefer my books and magazines to be paper.)

Yeah, I had a smaller Newt on an equatorial mount and it drove me up the creek, I hardly ever used it and eventually got rid of it. This 10 inch is a scope that's high on performance per £ and low on practicality and usability. You can buy a much more practical Dobsonian mount. Orion Optics sell them, there's probably other suppliers too. Or make one if you have the tools, workspace, and skill (things that I lacked). But whatever mount it's on it's a big heavy scope. Think about how far you'd have to move it from where it's stored to where you observe. If you'd prefer something ready-to-go, consider a new 6 or 8 inch Dob.

13 years on, does the advice here from @The Warthog still hold? I'm getting back into the hobby after some years of doing very little. Compared to the breakneck pace of "tech", it feels like most of the telescopes and mounts I remember are still around. But eyepieces? Plossls seem way cheaper than I remember, Revelation appear to have ceased to be, Astro Essentials have arrived, and I read people talking about "goldlines" whatever they are.

A few have suggested the short tube frac. And I could get for example a Startravel 102 on an AZ3 for pretty much the same price as the Mak on the Pronto. I hear the advantage that they're probably the most durable type but my doubts are threefold. One, unless the f ratio is very short they're not coming in as compact as the Mak. Two, the CA is putting me off (and I'm pretty sure apos are well out of my budget). And three, if I want a scope that's good for widefield and poor for high power, I already have that in the Heritage 76. I think I'm taken by the idea of a Mak as almost the exact opposite. And yes. I used to have a "department store" 60mm frac bodged onto a lousy photo tripod. It did an OK job looking at the Sun with a Baader film filter on the front; watched the Venus transit in it. But pointing at anything at night was hopeless.

FLO have the Nexstar 102 SLT Maksutov reduced in price. Buy or avoid? The aperture is a bit less than I was aspiring for (would prefer 5 inch) but it seems like it will tick the compact size box. Anyone got good or bad experiences with the mount? Edit: Or, for a comparable product, Skywatcher's 102 Mak on the AZ Pronto. Obviously manual vs GoTo, but I'm interested in how the stability compares. Wobbly mounts are not fun.