Ben the Ignorant

Yes and no. Just looking at any open star cluster, the 50mm shows only the main components and shows them weakly. The 80mm makes many more stars pop up, and displays what the 50mm displays with a very welcome boost in brightness, when comparing them at the same site. Going to a much better location can level the comparison, though, so it depends heavily on the respective quality of your skies in the UK and in France. There is a 1 magnitude gain from 50mm to 80mm, but if the naked eye star count is 1 magnitude worse, only the extra magnification of the Skymaster will grant some benefit.

A 10x is too different from a 20x and a 50mm is too different from an 80mm to make a fair comparo. Since an 80mm, especially with strong magnification, will require a tripod, you'd be better off bringing a small scope with you in France. So, if I were you I'd be researching the 56mm, 60mm and 63mm binocs.

And M27, I don't know how I forgot to say it, M27 doesn't boast the over-the-top surface brightness of NGC7662 but it's much bigger, so if you look for it close to the meridian you might see it. A 10x50 unveils it under a small city light-polluted sky but your light pollution or humidity rate could render the hunt tougher.

The brighter globulars, but don't go underestimating their size, a luminous sky extinguishes the outer stars and makes it seem as if the cluster is smaller than it truly is. The brighter open clusters because non-nebulous light sources (in other words, stars) compete very well against a light-polluted background. And the NGC 7662 nebula, by far one of the urban nebula chaser's best saving graces, it can be seen under the worst skies.

I can't remember if they were wet or dry, it was too long ago.

About that strange stiction between finely polished surfaces at 9:21, I think I remember feeling the glass microscope plates sticking to each other in biology class. But maybe it was just because they had a near-vacuum between them and atmospheric pressure pushed them together? The video says the surfaces have to be flat to around 1/10µ for the effect to occur, which is the diffraction-limited surface accuracy for lenses; are those tiny glass plates polished like lenses so they won't distort the image?

The last two seconds of audio are lost, the author apologizes for it on YouTube, but a flawless video nonetheless.

Start with NGC 7662 in Andromeda, it's so intensely bright blue you can't miss it. Just use enough magnification, but that reduces the hunting field, or be prepared to watch for anything that's not as tight as a star, averted vision helps. I've observed it with my 127mm from my city a couple months ago, and though I know it well, the ease with which it pierced light pollution stunned me again.

With very large exit pupils, in the 4mm to 5mm range, they are not that hard to see.

Almost all the brighter globulars look bluish to me, with varying degrees of greyishness depending on the telescope and conditions. Sometimes they appear so bright they border on white but I don't know if that qualifies as color. The most popular planetaries all have a clear bluish or greenish tint (without filter) to my eyes, also in various shades depending on the scope and conditions. The mighty Lagoon Nebula seems to have a very pale bluish look in large binoculars but only when transparency is great. And galaxies with strong surface brightness look either whitish grey or definitely blue, the most striking memory of this is the NGC 4485/4490 close pair in Canes. Through the rural astroclub's Celestron 11 they had an unquestionable blue tint, but from the city or through a smaller scope they were just grey smudges.

Alexandros doesn't ask what color things look, he asks how visible that color is; so the blacker background makes the color more likely to be seen if it's still intense enough after the filtering, if the eye is dark-adapted enough, if, if, if, and so on.

It's very difficult for reddish nebulas because the eye loses a lot of red sensitivity in the dark but bluish and greenish nebulas show some color under one or more of these conditions: - sky is quite dark and transparent - scope is real big - scope has very high contrast - scope operates at low power to concentrate the light on a smaller part of the eye, making the target seem more intense - target is bright - target is small and thus has higher brightness per unit of sky area (planetary nebulas are king in this) - you're looking through an O-III filter which makes the background so black the deep-sky object's color is not as difficult to discern because of stronger contrast That's for nebulas which have a large range of colors but galaxies and globular clusters have a smaller range of colors so the factors are mostly aperture and object brightness.

This is a cartoon contraption but you got to admire that someone had the dedication to craziness to build it for real!

Ever been embarrassed trying to explain to your neighbors what that strange dob is in your yard? Well, no more embarrassment, just tell them it's a mouse cannon. 😏

Just so everybody sees what we're talking about, this is the former spider. Its legs took that gentle curve when I severed them with giant cutting pliers, it's aluminum so no big effort and the consistent curve is funny to look at. It's a very sturdy spider but the slimmer one improved contrast, that was clear at first sight when I looked at the shady areas in dark trees. It seems Sky-Watcher puts the same spider/secondary holder on f/7 and f/5 scopes but the f/7 can take a smaller one, so if you want more contrast with your scope, changing the spider might be a better choice than buying more expensive eyepieces. The four small "L" holders are just stainless corners that costed one or two euros each. The longer part of the L was curved a bit with simple pliers, and the vanes are from an old fried electric transformer, its steel core was made up of piles of these thin steel blades. The hub is a plastic disk. Making the spider costed almost nothing, it's just that it takes a little daring and experience in metal crafts, besides that the only cost is time.

The 130/900 Sky-Watcher I got from Teleskop Service IS parabolic and it star tests perfectly, very sharp images and very straight Ronchi lines. The defocused diffraction patterns are truly identical on both sides of focus, and that's so rare I was baffled I paid so little for that optical tube. Sorry, I didn't take pictures of that because I didn't know I would have to show them. But the scope is so good I am making a thinner spider and a secondary holder that's not larger than the secondary mirror, unlike the stock arrangement. Job is not finished, the collimation screws have to be installed, the long screws have to be shortened, paint is just a rough blackening to avoid reflections while testing, but the image has already proven to be more contrasty. I wouldn't be doing this if the scope wasn't worthy of the effort, no views of the major planets yet but it is a very, very sharp lunar telescope. I have superglued O-rings around the focusing wheels to get a little more leverage and better traction, again, I wouldn't be doing these refinements if the optics were not worth it. And to answer Ricochet's question, coma is negligible, barely there at low power and outside the field at high power, so not a problem at all.

After returning from the club's observatory first thing I did was clean my binoculars' eyecups and eyecup covers with alcohol, it evaporates so fast you don't have much time to do the cleaning. But that's a good thing, the cleaning has to be brief, and the quickly evaporating pharmacy alcohol (ethanol) leaves no traces. I've stopped lending my binoculars because skin or eye infections are a real risk, and I bought another bottle of alcohol that I left at the observatory's little eyepiece locker, with a bag of those cotton patches women use to remove make-up, recommending they clean eyecups after each public session. However it caused another problem, dumping the alcohol-soaked patches in the bin causes a fire hazard, so they would have to be burnt on the grass each time, don't know that all the other people have the patience to go through that. What is a good, non-flammable disinfection agent suitable for optics?

The knob won't fall off, turn it till the image is sharp. The large disk of light is the massively unfocused planet, and the black circle is the shadow of the round secondary mirror's housing. We all see that in our scopes when they're largely defocused, don't be surprised if it takes an enormous number of turns, my C5's knob makes 37 turns from infinity focus to closest focus (at 2.5 meters). That's necessary to make the focus accurate, and to allow the Schmidt-Cassegrain telescopes to be used as long-range microscopes and macrophoto objectives. I've taken pictures of bumblebees from 3 meters and birds from a few tens of meters when using my Celestron as a telephoto/macrophoto lens.

Some old-fashioned plastics "deplastify" over time, they release their hardening component in the air so what remains is a sticky goo, it occurs in old binoculars' eyecups and in some parts of my not-so-young car (I'm attached to it and feel no attraction to other models). The fume and/or the remaining paste can be toxic but I don't know to what degree. If the rubber in your eyepiece is synthetic maybe that's why the warning is there but it could be a mistake or an overreacting paranoid measure. I've never seen that kind of warning on an eyepiece before.

Yes. Automated cameras keep track of meteor strikes but a number of visual observers testifying of a more subtle lunar transient phenomenon makes sure the event is not a camera artefact, and multiple witnesses gather more infos that can be cross-examined. As in the process of digitally stacking images, what is common in all of them is probably real, and what is not is probably misperception.

Yeah, I tended to think of the Moon as a dull rock with an occasional outgassing and a few meteor strikes here and there, but it has a lot more events and features worthy of curiosity. One I had forgotten about is the maze-looking plateaus that harbor magnetic anomalies, one of them is shown in the video, and the others are catalogued on maps but I haven't observed them for ages. On location there must be many, many odd things happening all day that we don't know because of distance (and because our telescopes are too wimpy to show things like the american flags on the Moon, what are we wasting our time with? 😏). The testimonies of astronauts are invaluable, robots can do a lot but the spoken account of a direct witness can't be beat.

For visual only carbon is a useless expense, and a triplet is not necessary either, especially for wide fields, you'll stick to lower powers most of the time so a doublet in an aluminum tube is okay. The 80mm f/7 doublet with FPL-51 glass will fill your bill. Teleskop Service and other brands sell it, there's no need to be "loyal" to a brand, the scopes are the same, but maybe some cosmetic details that you like will be present on one and not the others. Then there's the Sky-Watcher doublet with the slightly better FPL-53 glass, not expensive and in stock at First Light Optics, that one is sure to not disappoint. One difference worth mentioning is focal length, and thus, tube length. That is something to watch for when piggybacking a scope, as well as weight and balance. Speaking of weight, the eyepiece that will provide the widest views you're after can be very heavy (790g for my 34mm/68° Maxvision) or rather lightweight (330g for my 30mm/68° Aero Sky-Watcher). So, plan ahead how much field you want, and how much the eyepiece/diagonal/finder/mounting rings will weigh.

I have the 3.5mm, the 5mm and the 9mm Myriads, and they're all excellent. The 13mm is mysteriously not available, and the 20mm I didn't buy because it never went below my personal limit of 200€ for an eyepiece; I'm checking 365astro's website regularly just in case. In my 300/1500 dob it would give the maximal field with a 4mm exit pupil, almost as bright as a 5mm but shows less of the natural astigmatism of the eye with large exit pupils. Somewhat darker background, too.

For those who are into compact achros, that one is complete with diagonal, large finder, and dual-speed 2" focuser, handle and Vixen rail. It is one of the bargains Bresser offers pretty regularly in their website. Almost 200€ less than the usual price, that's a very substantial reduction. 😮 https://www.bresser.de/Sale/Ausstellungsware/EXPLORE-SCIENTIFIC-AR102-Air-Spaced-Doublet.html