Zermelo

As @Mandy D said above, the tread will be accelerating even with respect to the wheel hub or vehicle, as circular motion is accelerated. When you consider it from the perspective of the road or external observer, you add in a constant horizontal velocity (assuming the vehicle speed is constant) to that circular, accelerated motion, resulting in the cycloid. I think the instantaneous direction of the acceleration is still towards the centre of the wheel at all times (the derivative of a constant velocity offset will always be zero and won't contribute), so "accelerating" vs "decelerating" would need to be defined relative to a specific direction in the road's frame of reference.

I think I see what you're getting at, Olly. Agreed, you could take this to mean either: (1) A specific, physical point on the wheel's outer edge that is, at the moment under consideration, in contact with road, or (2) The location in space identified by the intersection between the wheel's outer edge and a line drawn directly downwards from the wheel's centre They happen to be co-incident for the purpose of the current discussion. I suspect an information modeller would represent the physical points on the wheel circumference as one concept, uniquely identified by (for example) the angular offset θ from some reference zero on the wheel, while the concept (2) above would be more like a role ("bottom of wheel") that can be fulfilled by any of the circumferential points at some appropriate time t (another role of interest might be "top of wheel"). These roles are defined relative to the vehicle, not the wheel. If the motion of the car were known, it could be modelled as a constraint between θ and t (quite simply, if the vehicle's velocity is constant). I might choose different words, but yes, in sense 2 above, the "point" of contact does move relative to the road, even though any "point" on the wheel (sense 1) that is fulfilling the role of "bottom of wheel" at a given instant will be at rest, relative to the road.

The point of the wheel in contact with the ground is instantaneously at rest, with respect to both the road and a stationary external observer. Over time, from that perspective, the point on the wheel circumference traces out a cycloid, with speed varying from 0 to twice the vehicle speed. From the perspective of the wheel hub, the point on the wheel edge traces out a circle at constant speed, and is never at rest.

That doesn't surprise me, I've had keyboard issues with other apps. To be fair, it must be difficult for app devs with Android; as well as the different versions of the base OS, and the different flavours from the device manufacturers, they also have to deal with user-selectable keyboards.

Evidence of fission, possibly resulting from neutron star collisions: https://www.space.com/nuclear-fission-neutron-stars-heavy-elements-gold

Another DM classic - graphic below was included in an article on the possible effects on the Earth of the recent increase in solar activity. I wouldn't give us much of a chance.

You may, or you may not:

I think you need to break the improvement down across different dimensions, as other commenters are already doing. Light grasp (hence image brightness) Limiting magnitude Resolution Contrast Colour rendition Image stability? (that question about whether an increase in aperture can actually degrade an image, in indifferent seeing) And the type of target may have a bearing on this too, for example larger aperture resulting in smaller Airy discs, which some observers prefer and some do not.

And possibly one of the better ones, if it's clear: https://bigthink.com/starts-with-a-bang/2023-geminids-best-all-time/

That's awesome - if you spend enough with them, they throw in a surface-to-air missile! Or is that only for american customers?

You will never tire of the view of those two, together in the same field.

Yes, a glass, by definition, has a disordered composition, unlike a crystal.

https://stargazerslounge.com/topic/362613-sky-watcher-az-gti-tracking-noises

From a purely linguistic point of view, fluorite of any sort is crystalline calcium fluoride. "Synthetic" means it has been grown in a lab/factory, "natural" means it was dug up, but I would say both of those qualify as "real". Any commercial telescope objective is too large to be made from natural fluorite (which often has impurities anyway). FPL-53 should presumably be described something like "variety of glass having optical properties as close to fluorite as makes no difference", but that might be too long to fit around the outside of the objective.

Prepare yourself for a midnight visit from the JNES (Jovian Nomenclature Enforcement Squad).

I use a 6" Newtonian on a conventional tripod+alt-az mount. The reason that Dobs tend to dominate on larger sizes is cost. To mount a 10" Newtonian on a tripod alt-az as steadily as a on a Dob base would cost a lot more. With a Dob, you are maximising the aperture you can get for your outlay.

I paid even less when I bought mine. The prices on some of the Svbony kit do fluctuate massively, both locally and from China. It's worth keeping an eye out if there's something you're after.

Synscan Pro v2.4.10 (Android) This version has a couple of bugs, noted here. At the time of writing, this version has yet to be added to the change history. That list mentions four intermediate versions since 2.3.7, for which I did not see updates in the Google Play Store. Among other changes, the history mentions changes to the way that further stars are used to improve goto accuracy.

You have had some good suggestions above, but £30ish will seriously restrict your choice. If you don't mind ordering from abroad, there are a couple of other options. If you can stretch to £37, you could replace your 10mm stock eyepiece with one of these: https://www.aliexpress.com/item/1005006018468922.html It has a 60 degree field of view (like the Starguiders) and gives a good, sharp image with minimal distortions. As has been mentioned already, it would only give x65 in your scope, so you would still need a Barlow lens to give decent views on the planets. Or, for around £28, you could get this zoom: https://www.aliexpress.com/item/1005005756520671.html (there are three different models under the one listing - I'm talking about the 7-21mm version) A zoom gives you a whole range of magnifications in one unit, and is very handy if you're on a budget. I've not used this particular one, but it has had some good reviews. This would give you a decent magnification range of around x31 to x93, but for planets you would still want to combine it with a Barlow on good evenings, where you can use higher magnification.

When I did my review, the only other zoom I had to compare it with was an OVL Hyperflex 7.2-21.5mm, and the Svbony action was noticeably easier than the OVL. I did note that the final 4mm-3mm adjustment was less smooth, probably because that change involves the most movement of the eye lens on the stalk. And I, like the CN reviewer, have gotten used to tightening the focuser screw a little more than I would for a fixed EP (but not more than for the OVL). My subsequent acquisition of a Clicklock took care of that. More recently, I bought a Svbony 9-27mm, and the action on that is easier than on either of the other zooms. I think I've had the 3-8mm long enough now that it's not going to change, and I do get the feeling that the resistance is caused by the mechanics (velocity ratio?) inherent in the design, rather than friction or thick lubrication.

It's here: https://www.cloudynights.com/topic/862337-2023-eyepiece-buyers-guide/

Well, it gets better https://www.space.com/nasa-lucy-asteroid-dinky-3-space-rocks-contact-binary

I've found them to be responsive to feedback in the past.

That's an interesting contrast to another live thread, where the consensus seemed to be that smaller refractors outperform larger reflectors in iffy conditions.

Oh yes, I see what you mean. When you choose a deep sky object and hit goto, it counts down to zero but it never gives you the screen to confirm. I don't know how this release made it through regression testing. I've not used it in anger yet, I'm just trying this out on emulator mode. I haven't done any observing since I upgraded, and in any case I use sky safari for most things during sessions.