Zermelo

I thought about filing it under "eyepieces", then I thought, it's not really saying anything about the eyepieces...

I just noticed that Svbony have a sale on eBay at the moment for both their 7.2mm-21.6mm and 9mm-27mm zooms. These have been discussed before on the forum, they are SVBONY's versions of eyepieces that are made under various labels. If you already had your eye on one, or both, now might be a good time. Confusingly, both versions are called "SV191" - if you search for that, you will find each zoom available separately, or the pair for £46.99 posted.

A thread that's a bit like the big bang - starts with a small seed, blows up, gets messy, could go anywhere...

I read somewhere that it had been speculated that this was exactly what had happened - quantum fluctuation gives particle-antiparticle pair, inflation expands space and multiplies matter and antimatter, then asymmetries in the physical laws result in excess of matter over antimatter, which is left over to create our universe I have a book somewhere, can't remember which one, that explains this. Just as curved spacetime can give rise to a volume that is finite but unbounded, so can it result in a situation where time can begin at some finite point in the past, and yet not have any "boundary", i.e. there was no beginning as such to the universe. I really couldn't get my head around the details. Both of these points show how our difficulty with "causation" of the universe might be mistaken.

I stuck on a Telrad to replace the stock red dot finder, and I use a 9x50 RACI in the finder shoe. Now that I use SkySafari I rarely use the Telrad, but I find the RACI invaluable to identify the field when the goto isn't very close.

Hello, and welcome to SGL. Have you seen this post?

I have found FreedomFind useful to avoid noisy slewing in my back garden in the middle of the night. I use it with SkySafari, so I guide my movements using my phone until I'm close enough, then do a goto for the final couple of degrees (which it does quietly). If you're moving between widely-spaced targets then, yes, it will be faster than using just gotos, though it can be a bit less accurate. For that reason, a decent optical finder is very useful. I've not used Celestron kit, so I can't compare.

I've been thinking about ClickLocks since this thread, but since I was quite happy with the performance of my Revelation diagonal, I went for a reducer that will live permanently in it

Try for M51.

I like my 14mm as much as the other Morpheus I use. There's probably already a link somewhere above to this thread on CN, which does discuss the 14mm in particular. Ernest Maratovich has done aberration bench tests on all of them. I can't find the link now, but I copied the figures out a while back: which show the 14mm as slightly inferior to the others off-axis at F/4, but as good as the 12.5mm at F/10.

Sometimes the ads use an "X-ray" image: It's been said before that the 17.5mm was a little different (and released later). Though they are all described as 8 elements in 5 groups.

From the Code of Conduct: The Buy & Sell section Access to SGL's buy and sell section is a privilege that has to be earned, You can do this by accumulating 50 posts to view / buy from the classifieds and 250 posts to place an advert in the classifieds. This has been initiated so that people can't just join the forum so they can off load or buy up astronomy equipment.

That's why FLO generate the clouds. They're no fools.

If you are able to leave the tripod/mount undisturbed between sessions, you can get it to hibernate and continue on the next session. I have to bring all my gear in, so I do an alignment each time. I prefer the "north level" flavour, but if I'm trying to align at dusk then the stars may not be obvious, so "brightest star" is sometimes better. You will get better with practice. I find that mine is always good enough to get me within my finder, and usually within a long eyepiece fov. That's all you need.

This page has pictures of some common aberrations: https://www.skyatnightmagazine.com/advice/understanding-optical-aberrations/ For a more technical explanation: https://www.telescope-optics.net/coma.htm

I'm also wanting this, ideally combined with light pollution levels. The best I've found so far is this: https://stargazerslounge.com/topic/275117-uk-map-combo-of-light-pollution-and-clear-nights/#comment-3013632 which is quite low-res. I think you can download cloud cover data from Meteoblue, but you have to pay.

I am mid Bortle 4 (SQM 21.02 is the best I've measured). With a 6" on the best nights, I've seen the cores of M51/NGC5195 and some light patches where the arms would be, but no continuous arms. I think I would see them if my eyes were 30 years younger. But I did see definite arms on M51 when I viewed it with a 5" Mak from a Bortle 3 site.

Well that's interesting, given the statement on that other thread that I can't find now. Perhaps they did it just for you?? But now you've also removed one of the reasons why I wasn't going to be tempted by this offer Only a few more days to stay strong ...

I think we are identifying two different senses of "consistent" here. (1) In the purely mathematical/logical sense, a set of (well-formed) statements is consistent if they cannot be used together to derive a contradiction, using the agreed rules of inference for that system. In particular, when applied to a proposed set of axioms for a formal system, that axiom set is said to be consistent if it is not possible to derive a contradiction, i.e. ⱯP ⌐(P V ⌐P) where P is any well-formed statement. Godel showed that any system complex enough to contain normal arithmetic must either be inconsistent or incomplete (in the sense that the system must contain well-formed statements that cannot be proved either true or false from its axioms). This effectively torpedoed the attempts of Hilbert and others to prove the consistency of mathematics by describing it from "outside", with metamathematics (I think, hinted at in a previous post on this thread). (2) In a more general, physical sense, that property of reality by which it is observed to behave in the same way in different times and places, and hence which behaviour science can then render as "universal laws". This is a bit more debatable, for example do we still count the laws affecting cosmology as "consistent" if the value of the cosmological constant or the speed of light change over time?

Assuming that you mean examples of similar quality, then the received wisdom is that it's about neutral at F/7: https://stargazerslounge.com/topic/328670-mirror-vs-prism-diagonal-for-fast-refractor/ https://www.cloudynights.com/articles/cat/articles/mirror-vs-dielectric-vs-prism-diagonal-comparison-r2877

Yes, I think if I had my time (and money) again, I'd get a 2" Clicklock dielectric. My Revelation diagonal is very decent, but I like the look of the Baader mechanism. I believe Baader do a Clicklock 2" to 1.25" adapter, so I'm thinking of getting one to put in the Revelation.

The other advantage of a 2" diagonal, even if you don't have many 2" eyepieces, is robustness. My heavier EPs feel safer in my 2" than in my 1.25" tak prism. The larger diagonal is significantly heavier, so I do need to think about balance and mount capacity.

I have the GtiX and it does the same. I think it just means that the WiFi is connected, so it is going to be flashing the whole session. Stop it? In my case, thick black tape.

Arguably the single most useful development in mathematics, for modelling the real world, was the invention of calculus, based on the properties of a (continuous) real number system. The continuity leads to irrationals, transcendentals, and more, which some mathematicians have found objectionable. But the usefulness of calculus in science has tended to outweigh the objections from a minority of mathematicians - the universe seems to behave as if it were continuous, whether it is or not. Recent speculation that space and time might be quantized, and not infinitely divisible, would give support to the skeptics, but they seem to be entertained only by a small minority.