Captain Scarlet

Just in again from a session outside with only the naked eye. I’d intended to get my 12” out but it was cloudy and rained earlier so I baulked. In spite of that, even without scope it seemed a privilege to be stood out under such a sky. Lyra was stark whereas Bootis was almost drowned, such an odd comparison. Ursa Minor stark too. M13 naked eye. I measured 22.05 on my meter, the highest I think I’ve ever recorded. Just gawping. Magnus

I noticed a beautifully clear sky just before bed last night so went outside for 20 minutes or so with 15x56 bins. I saw _something_ exactly where C/2023 A3 (Tsuchinshan-ATLAS) should be, but that comet is mag 10.8 . Theoretically that is just within the potential of such a pair of binoculars, plus it was incredibly transparent, mag 22.0 measured at zenith, and the comet coincides with another rather faint star SAO 139411 at mag 10. Jury out therefore on whether I got the comet. M101, 51, 81 & 82 were all there, M44 and the Coma Cluster Melotte 111 naked eye, its shape quite clear. It was cold though so bare hands lasted only the 20 minutes. Clear again tonight so the 12” may come out. Magnus

Interesting, thanks for all the responses. I lean towards Bill Paolini’s thoughts as presented by @JTEC, but local opinion seems to be evenly divided. As for adding heaters to secondaries, I’ve avoided that for the same reasons, and decided that dew-opacity signals “end of session”. Luckily I’ve found that there’ve been overall surprisingly few heavy-dew nights, and this is Ireland! Magnus

It’s my understanding that the figure of a Newtonian mirror can significantly change shape whilst cooling, with the edges cooling faster than, and thus at a lower temperature than, the core, inducing turned-edge-type aberration. I’ve often seen it in my own 12”, starting off a session with seriously different in-and out-focus patterns, gradually becoming hardly-different later on. This describes it: http://www.loptics.com/articles/fourlessons/fourlessons.html

Just in from a short but enjoyable session with the 140 frac. First Light for my Feathertouch on the scope. Wonderful as expected. Seeing seemed not too bad: 268x on the Moon was fine. One Plato craterlet on show, the big central one, in moments of clarity, but no Alpine rille, though it felt as though it should’ve been visible. Not sure what the optimum angle is for that. That remains a Nemesis for me. Epsilon Lyrae a nice split too, first look of the season. Magnus

Planetary detail, especially Jupiter. I think that 8” Newt vs 5” refractor might be close to an equilibrium between the two. The refractor of course has a purity of view and a minimum level of diffraction “light-spreading”. Whereas a Newt has its diffraction spikes. Mostly, those spikes are diffraction “thrown away” from the star you’re looking at, so don’t affect the view of the star itself too much. But Jupiter can be imagined as a multitude of bright stars all clumped together, each “star” throwing its spikes directly into the neighbouring “stars”, dramatically smearing out contrast on the disc and negating the effects of the extra aperture. As it happens my own best views of Jupiter are equally split between my top-notch 5.5” refractor, and my 8” Newt. But of course they were on different nights with different seeing. Magnus.

It’s common knowledge that until a scope, be it reflector refractor or cat, is properly cooled (or warmed!) to ambient temperature, its figure will be off and the view through it will be poorer than it could be. So why isn’t the same accepted as being true for eyepieces? I can understand that small eyepieces will adjust temperature quickly, but surely monsters with many elements of thick glass, which description includes a lot of the top-end eyepieces, will suffer from cool-down effects and aberrations just like an OTA? And yet the received advice is to keep them in your pockets to stave off the dew. Cheers, Magnus

Yippee I got it! fast-moving cloud with a good few gaps. I used my 88mm Kowa spotting scope with Delos 4.5 inserted giving 113x. Awkward angle of course but once seen it leapt out. Very pleased. Magnus

Things were looking optimistic early evening. There’s clear sky north but moon area has remained stubbornly covered. 🤞

Something you must ask yourself when uncertain whether you’re really seeing something is “would I see it if I didn’t know exactly where it’s supposed to be”? And particularly with Sirius B, are you seeing “that dot” regularly in the same place, minimizing the possibility of seeing a random artifact appearing fleetingly just where you want it to? You must be harsh with yourself about those to confidently declare a positive, in my opinion.

I’ve had a bit more of a look around. My bet is a TV 102 f/8.6 see here https://www.wlcastleman.com/equip/reviews/100mm_refractors/index.htm

That was my first thought but in looking up the no101 is f/5.4 . The scope in the article seems f/9 at least?

Perusing the Irish Times website just now, I came across an article inviting entries for an astrophotography competition. At its head is a picture of a couple of people with a scope. The scope is clearly a Televue, but seems quite a slow one, ie long and narrow. I don’t recognize it from those with which I am familiar; which model is it does anyone know? Magnus

Sounds like a very nice mirror, I have two OO mirrors myself. Magnus B.

Definitely it sounds like bad seeing. And observing from inside a warmer room, you’re looking through a stream of warm air pouring out of your door or window, that’s a well-known effect even amongst birders. I have a fabulous 140mm refractor with which I’ve seen Saturn’s small moon Mimas on a very good night. But the last time I took it out, the seeing was really bad, yielding views similar to what you describe, so I just abandoned and came in after a few minutes. It’s just bad luck you had one of those nights for your Starfield’s First Light. Don’t lose heart, it’ll be fine I’m quite certain. Cheers Magnus