wulfrun

I don't think that idea holds water anymore. Current "best guess" is that it'll continue to expand at an ever-increasing rate and eventually just become, essentially, a vacuum. Gravity will have lost. At least, that's my understanding of the current ideas.

Slightly over your budget but I found this in stock as of now: https://www.bristolcameras.co.uk/p-skywatcher-heritage-100p-telescope.htm I have no experience of the store. As a starter, you could do worse although it's not likely to provide "wow" views of planets. The table-top Dob style has already been commented on for its cons but if needs must...

As a small aside - Betelgeuse has exploded, not the star (as far as we know) but an oil tanker named after it: https://en.wikipedia.org/wiki/Whiddy_Island_disaster Somewhat ironic, not to diminish the awfulness of the disaster.

Recently, Neowise, which has rekindled my astronomy interest. Ever, probably the total eclipse of 1999, for which I was not quite in the umbra region but it went very dark and I managed a series of shots leading up to and beyond totality. Just a chip of the sun showing.

Suggestions: first - PATIENCE - if you break the stubs off you'll be in a worse position (obvious, I know). Try and get a small butane blowtorch on the alloy (?) parts and keep the stubs as cool as possible. Use something like mole-grips or, where there's enough thread left, get two nuts and lock them tightly against each other. Technique is everything; if you can get them to move, even a tiny bit - STOP - re-tighten slightly and repeat, rock them back and forth going slowly in favour of "undo". Penetrating oil (like Plus-Gas, not WD40) will help, get something on the stubs now and leave it at least for a day before you even start trying. Diesel works well as a penetrating fluid but take care with that blowtorch then. A light smear of coppaslip or equivalent (copper grease) on the new screws will reduce the chance of siezure in future, as will wrapping the threads with teflon plumber's tape - if you can get the threads back with it in place. I would replace them with allen-headed blacked screws if you can get them (should be easily available). If you have access to someone with engineering stuff, a "plug" tap run into the threads would be well worth the trouble, to clean the threads out.

From the looks of those on the link, they have a plastic cover on the bridge at the front, as do most nowadays. Unscrew it and you should find a standard-thread screw hole for an L-bracket. For a budget option, a sturdy photographic tripod can probably be had second-hand off an auction site for very little, just be sure it has a pan-and-tilt. A monopod as mentioned above is probably a better option though. I have a decent photographic tripod and L-bracket that I've used mine on - it's ok but not the most convenient, the tripod legs tend to get in the way at times. Does the job when needed though.

The movement across your field of view is due to the earth's rotation, well, 99-point-a-lot-of-nines percent is. You're also assuming that the distant object is not moving and nor are you (i.e. the earth is only spinning on a fixed spot), neither of which is true in astronomical settings. Not to mention the fact that to remove the earthly-rotation component you'd need to know that to a very high level of precision in addition to measuring your transit time to very high precision. Unfortunately, it's all gone way beyond the possible. A needle in a haystack would be trivial, in comparison. That's my take, anyway!

Thanks to all for the input. I'll give it all some thought and not rush into anything, possibly even wait till I've used the scope a bit and see where that leads me. I was aware that it's a "fast" scope and would require decent eyepieces to give its best. I have a better understanding now, at least.

Thanks, that's very helpful. I'll see if anyone else weighs in on the BST vs X-Cel LXs. The Explore is fair jump in investment, especially the 8.8mm 82-degree suggested above; I'll probably hold off on either of those until I see how I get on with the supplied 25mm before comitting. Out of curiosity, is there a technical reason you say that the 18-25mm BST/X-Cel LX would be awful or is that purely experience-based? I am not doubting you but if there's a technical explanation I'd like to understand it - I have that kind of mind and it's useful knowledge. Noted on the focuser, I'm sure I can cook something up. I'll mull over the 5-12mm range to try and avoid duplication with barlowing, although that might not be easy. Also, no-one's yet offered an opinion on the Hyperion zoom. Unless it's a poor choice it'd still be in the running so I'm still after bad/good idea opinions.

I think there may be crossed wires here. I know the theoretical maximum is around x225, I also know that "seeing" and other factors make that rarely possible. I meant what would you consider a realistic maximum in the UK, given the scope? I'm hoping the Virtuoso mount will at least keep things in the FOV usefully well - reviews suggest it will.

Seems a pretty reasonable suggestion, thanks. I had also considered 25mm and 8mm plus barlow for a slightly greater variety. I've seen that diagram and it's quite useful to see what it shows in the EP. I knocked up a spreadsheet that calculates all the relevant stuff for me - for any given eyepiece/barlow - but of course that just gives numbers without context.

Thanks for the opinion, it's always good to hear - whether one agrees or not - and the nudge towards BSTs. Your ideas would give me x28, x42 and x63. Are you suggesting that more than x63 is likely useless in the UK? That comes as a surprise! I can well believe it true from my back-yard but under better conditions what would be feasible? Before you say it, no I haven't fallen for the idea that magnification is everything...just sometimes nice to have on hand. Half the idea of choosing this scope is that it's very portable to darker skies. Yes, I live in Wolves but I was born in Bloxwich (someone has to be). EDIT: for not a lot more I could, instead, get the Hyperion Zoom 8-24mm, with a slight sacrifice of FOV at the 24mm end. It seems to be well thought of. Any opinions welcome.

First off, the scope in question is a Skywatcher Heritage 114P Virtuoso, so 114mm f/4.4 and fairly modest capability and with tracking but not Go-To. Note that I'm new to astronomy, at least in the practical sense. I won't get my hands on the scope until Christmas but I'm thinking ahead about an eyepiece set, not least because I expect the 10 & 25mm supplied to be mediocre and limiting, at best. With this in mind there's no rush and bear in mind that I have no strict budget. Saying that, I don't want to go way over-spec and break the bank for no good reason. However, I suspect that this may not be my last or only scope, so I'd want any purchases not to be useless on future equipment. I've read multiple articles so I understand things like magnification, FOV, exit-pupil and so on. My "experience" though, is not based on practice. I'm also new to scopes so there are probably pitfalls that I have no idea about. I do have a lot of experience in photography (terrestrial not astronomical) so the basic concepts aren't new. I have in mind a set of 3 eyepieces plus a Barlow, 2x seems to be the sensible choice. I have not yet developed any preference for DSOs, planetary etc so I'm aiming for a general, starter set that would cover a useful range and is based on the new scope's capability. I'm looking at either BSTs in 5mm, 8mm and 18mm plus 2x barlow OR Celestron X-Cel in 5mm, 7mm and 18mm plus 2x barlow. BSTs seem to get a decent reputation. Either of these gives me from x28 up to x200 in reasonable steps and all fit within sensible ranges for exit-pupil and magnification. The mid-range FLs fall into the "about 2mm exit-pupil" sweetspot, I believe. I could swap out the 18mm end for a 25mm for x20 but I'm old enough that the 5.7mm exit-pupil is likely a waste and I have a reasonable pair of 10x50 binoculars (Pentax SP WP) for low-power use. I know the highest magnification is close to the theoretical limit and wouldn't often be usable anyway but I'd be getting it almost for free, so why not have it available. My questions then: are the choices reasonable? Have I picked sensible quality? Are the Celestrons worth 40% (ish) more than the BSTs? Anything glaringly obvious that I've missed? One other question: barlows - there's no such thing as a free lunch so where should one be avoided? I didn't find any explanation of the pros and cons in my reading but I think they are the astronomical version of a photographic teleconverter, which I do understand well enough. I'm very much open to alternatives for make, or FL/FOV choice. I'm also open to not buying anything yet, or to a different set, if that's a more sensible approach. Apologies for the long-ish post but I wanted to explain my logic so it's there to be picked apart. I'd rather learn from my mistakes the cheap way, from those with better knowledge!

How did you collimate it? Sorry - couldn't resist! Top marks for improvisation though.

Fair point and well spotted, not something I'd actually noticed that the main fuse supplies everything. Indeed a fuse needs a serious overload to blow quickly, the zener could burn out its internal leads before the tracks go, if the fuse is as high as that. That would leave a weakness in the zener idea as suggested.

Connect it across C3, which is next to the voltage regulator, not really in need of a diagram since it's marked on the board. Make sure than banded end of the zener connects to the positive side of C3 (work it out or use a test meter to be sure). Without having the board in front of me, I'm not quite sure but possibly solder it to the underside of the board onto the pads for C3? Whichever way you do it, use sleeving on the leads, insulated wires or whatever it takes to ensure you don't make inadvertent connections elsewhere. Also, double check everything before powering up again.

The idea was to keep it simple, one component, whilst providing some protection against over-voltage. The probability of a 7805 going short isn't that high but for a few pence why not. Perhaps a liberty to call it a crowbar circuit but that is its function. Agreed the zener should be checked if the fuse blows without obvious cause.

Easy - obtain a Zener diode of 5.6V and 1-watt (or higher) rating. Referring to the hand-drawn schematic further up this thread, connect the zener between the positive side of C3 and earth, the other side of C3 will do nicely. The Zener has a band on it, that end must be connected to the positive of C3. Use a reasonable gauge wire or just solder the Zener on the back of the board, whatever is convenient physically really. Zeners are available in a wide range of voltages, you need something higher than the supply is ever likely to be in normal use but not too much higher. Off the top of my head, 5.6V is a standard value and quite acceptable. Be aware that if the zener is called into action, it might be sacrificial and fail itself but it will certainly blow the fuse and protect the other circuitry. Just to explain, a zener that is wired "backwards" passes almost zero current until the threshold voltage is reached, above which is rises very steeply. It will draw so much current that the fuse will blow, and if it fails in the process it will fail short circuit too, guaranteeing protection. Excellent and cheap over-voltage protection known as a crowbar circuit.

But they invariably blow over the heating element.

A bit late to this topic but if the voltage-regulated circuitry is sensitve to over-voltage, it ought to have a "crowbar" zener diode following the voltage regulator. A 5.6V 1-watt zener to earth would cause the fuse to blow if there's an over-voltage fault on the 5V line. Any series-regulator that relies on a bipolar pass-transistor is liable to fault by short-circuiting and passing full voltage, since that's almost always the failure mode of the pass-transistor. Commercial designers don't bother with such protection unless it's costly circuitry being protected, since it costs in components and PCB space - although in this instance they did bother wth reverse-polarity protection from the diode at the power input, strangely.

Standard practice is that a fan should blow air onto a heatsink, never suck from it. Blowing causes turbulent flow off the fan blades. Not the same application but the principle is the same as explained here: https://sound-au.com/heatsinks.htm#s18

Assuming it is quoting NASA, what's this bit about: "The agency said that weeding out the nicknames was a first step in its 'commitment to diversity, equity and inclusion'." What's equity got to do with it, or is it the new name for equality? I always thought equity was to do with money. I think they'll have to rename quite a few things if we're going to go all-PC.

I'd suggest a visit to Wikipedia to look up gravity and the equivalence principle. Io is not "merely falling into Jupiter", which implies that it is doing so passively. Io is in a non-inertial frame of reference, meaning it's being accelerated* by Jupiter's presence. Io's orbit is also complicated by resonance with Europa and Ganymede so it's acceleration is changing, with means physical work is being done and that's the source of most of the heat. I'm not too sure I've explained it all that well and I'm not too sure I actually understand the concept all that well myself, never mind trying to explain it simply. *Sorry if I'm patronising you but "accelerated" here is meant in the strict physics sense - a change in velocity - not the everyday sense of "going faster and faster"

Not sure a UV torch or LED-based item will work but it could be worth a try. I know things like water-sterilisation stuff uses UV-C which is absolutely NOT eye-safe. I'd assume you need something along those lines to kill fungus. LEDs don't usually go down to UV-C wavelengths, except possibly the expensive commercial stuff. You can get UV-C fluorescent tubes easily enough though, although they come with a warning not to expose your skin or eyes. I have a 365nm 3W UV torch, but again you are warned not look into the beam. It's not very bright, visually, and that's the issue - it doesn't give a visual clue that it's actually quite powerful. Edit - just noticed the shoe-sanitisers claim 265nm, that ought to work if the claim is true.

Good to know it wasn't too bad a choice then. My logic was it's not too big, for portability and storage but the tracking should help me follow things. I'm on the fence regarding Goto and too inexperienced to know if it would suit me or not. I tend to think (rightly or wrongly) that I should at least try to learn my way around without it until I'm at least competent enough to set one up and see if I feel the need. I think the next purchases would be some half-decent eyepieces but again, I've yet to see what direction that leads in terms of FL. Expect the see some "what eyepiece?" type questions in due course!