Zermelo

It's interesting that quite a few of these stars are described as being green, and previous discussions have also mentioned green stars. As has been observed above, there is a degree of observer subjectivity in such assessments, and I expect that, with doubles, colour complementarity has an effect too. I've seen green myself, but very rarely. And yet, there are good arguments for saying that green stars do not exist: https://stargazerslounge.com/topic/375783-ep44-sunday-18th-april-2021-730pm-bst-why-there-are-no-green-stars-by-paul-money/#comment-4072939

Are you following a design that you can share here?

Yes, Orion is a great hunting ground for doubles, and all of those are good. I've found 52 Ori at 1.0" to be very challenging unless the seeing is good, and I'll often go there first to check out the conditions. I would add 32 Ori/STF 728, which is a touch wider at 1.4", though with a greater mag difference than 52 Ori.

That's interesting, Rob - I'd not thought of taking binoviewers to an outreach session. Which eyepieces were you using, and what TFOV were you getting? Did you find that many people were needing to adjust the gap between the EPs to suit their face profiles?

This story just popped up in the DM science section too, and was another chance for one of their interns to show their lack of scientific knowledge: "The cosmic phenomenon carried the energy of 240 quintillion electron volts - that's 240 billion billion (followed by 18 zeros). For comparison, a typical lightning bolt is about 300 million volts." So, if you're not sure what type of quantity an electron volt is measuring, just Google for something big, that's measured in Volts instead. You might as well compare it with the size of Wales. I converted the 240EeV to around 38 Joules of energy - enormous for a single cosmic ray particle, but small beer in the macroscopic world. The average energy of a lightning bolt is apparently around 109 J, which is just a bit larger.

Miranda is impressive.

Yes, the more I observe, the more I think that what I describe as poor seeing is often heat rising from nearby buildings, either heat absorbed during daytime in the summer, or heat from chimneys and flues in the winter.

I must experiment with different combinations. I think I have seen a different colour on the opposite side, as you describe. A bit like atmospheric dispersion, but that shows as a top/bottom difference, not side-to-side.

Well, I didn't research that very well: the moon was actually high up and dominant. But the goto was working well, with a small but consistent error, so I could pretty much guess where the fainter targets were, even if they weren't visible in the 9x50. The seeing did vary a bit, but overall it was mediocre. I did split quite a few doubles, including some wider-but-faint first timers: HD17007, 30 Arietis, HD15695, 66 Ceti, HD15994, HD17332 and HD6651. The tightest I managed were 42 Ceti at 1.6" and Epsilon Arietis at 1.3", though only very occasionally in a boiling murk. Jupiter was similar to last night, not taking a lot of magnification, but showing some detail in the equatorial belts. Uranus was its usual pale green self (I've never seen it otherwise). And the moon - it just fitted into my Svbony 9-27mm zoom at its widest, nice and sharp to the edge, though with a thin, yellow caste on the limb. Tycho was bright and prominent, this close to full. But high magnification showed some softness to the detail. Later on in the session there seemed to be some high mistiness across most of the sky, and the moon's effect was magnified. A bank of cloud blew in from the North East, and my ungloved hand was seizing up, so time to come in.

Aligned the Mak, back in for some extra layers - temperature is dropping like a stone out there.

It's cloudy here right now, but the cold stuff from the North looks like it could bring some clear hours this evening: Interestingly, Meteoblue is forecasting some poor seeing here, but Metcheck is much more optimistic. The jet stream will still be with us: and of course, the big, bright thing will be up all night, though quite low down in Pisces.

Ah, sorry, I just looked at your post count and you may not be able to access links to the internal marketplace just yet.

No connection with me, but just now ...

I agree with the above comments, that mount looks a little bit insubstantial. FLO sell the SW 127 on an EQ3-2 mount, though, as you say, for quite a bit more. They do have a discounted ex-demo item at the moment. By the way, even with the Skywatcher model, there are two versions of the 127 OTA. One is sold bundled with a mount, the other is normally sold on its own. The optics are identical, but the bundled version is slightly lighter, lacks collimation screws (though the Maks hold their collimation very well in any case) and has its dovetail in a different position.

This is an important point. You may already be aware of this, but if you wear glasses only to correct for distance, then the scope's focusing mechanism will normally take care of that. Though it may be a pain if you're sharing sessions and need to refocus all the time; not difficult to test out, though. However, if you wear glasses because of strong astigmatism, then you will need to use them for observing too (leaving aside some very pricey accessories). Even then, you may find that you can get away without them when using higher magnifications (shorter eyepiece lengths). The Starguiders mentioned above were my own first upgrades, and work very well in my F/5 reflector, though I don't wear glasses. If you are happy to order from abroad, then XCEL-LXs mentioned above by @Naughty Neal are good performers with a proven design, and normally retail for twice that price. I'm not sure about their eye relief, though. For your longer eyepiece choice, I agree with @cajen2 that the Vixen NPLs deliver great views. I have the 30mm and use it all the time, even though I have an excellent (and more expensive) UFF. They also do a 25mm.

It was the first outreach evening of the winter season for my club, at a local school. The 4" achro doesn't get much use at home, but it's the one I usually take to outreach. The weather didn't look promising while we were setting up, but at least the low cloud was scudding across rapidly enough that no-one needed to wait too long for a gap. I'd planned to shoot for some wider targets that better suited the short scope, but with the prevailing cloud I ended up alternating between Jupiter and Saturn instead. The achro did OK on these, with an ES 6.7mm giving a modest x90, and a Baader semi-apo filter taking out most of the violet. After a while the low cloud cleared up a little, and everyone got to see a few sights that impressed them. I finished off with Albireo for the stragglers, with the colour contrast rendered very pleasingly by the Bresser.

"... OK Midjourney, /imagine that a mainstream astronomy kit provider started producing some really cool, semi-professional stuff, and exhibited it at a show somewhere a long way away. Create some photos that might be taken there, by a lucky visitor. Oh, and tease the viewer by blurring some of the key information... "

If you were happy to order from abroad, even cheaper: https://stargazerslounge.com/topic/412945-svbony-zoom-eps-on-sale/?do=findComment&comment=4433978

If you really did want to spend up to £100 on a "Barlow", I'd go for a x2 telecentric multiplier like this or this. They have some advantages over the regular Barlow design (there is some discussion and links here). But if I were you, I'd stick with a cheaper, decent, conventional Barlow like this one. You could use the Barlow with the Stellalyra 8-24mm, if you are already committed to it, or perhaps have a look at the SV315 (the Svbony 7-21mm mentioned by @Mr Spock above, £42.49 in the sales), which has very good reviews. I am currently testing out an SV125 (9-27mm), with which I'm also impressed. Finally, as also suggested above, you could try the SV215 3-8mm planetary zoom unBarlowed, which would give a continuous range of magnifications. It is a very decent item (my own review here), but will set you back a little over the £100, even in the sales. As has already been said, plenty of options.

There's a Black Friday deal on UK Amazon, £110.49, 12 left.

Those higher mag Barlow tend to be used for imaging rather than visual. One rule of thumb is that the maximum magnification in ideal conditions is around twice the scope aperture in millimeters, so ~x300 for your scope. But, in the UK at least, the usable magnification is often less than this due to seeing conditions. I would save your money for something else.

Get thee behind me, Satan (other malevolent deities are available)

Is that a fancy name for one of these?

Yes, perhaps I should have said "settle up" rather than "settle down".

I've seen wildly varying prices on different sites. I'm assuming it will settle down with time.