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

8 hours ago, Steve Ward said:

With reflectors the cooling to ambient is to reduce air currents inside the tube disrupting the view , it's not the figure of the mirror that is "off".

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

5 minutes ago, Mr Spock said:

NP101?

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

Here in SW Ireland our experience of the recent 2024 April 8th Solar Eclipse was that it was to end in the Atlantic just short of us. If lucky, just before sunset we’d get to actually see about a 35% eclipse very low to the horizon. I was lucky: I glimpsed it for about 4 seconds in a gap in the horizon-clouds. But the closest to totality, somewhere about 90%, was actually going to happen shortly after the sun had set, when about 5 degrees down. In other words, during Civil Twilight.

So, I thought, Twilight should be for a while significantly, perhaps even noticeably, darker than normal. I decided to take SQM-L sky-darkness measurements in the minutes leading up to maximum coverage and compare them to what I would expect on a normal evening.

In the event it wasn’t naked-eye noticeable. But it certainly shows up in the data.

Since early 2020 I’ve been collecting darkness data from my now-home site using a Unihedron SQM-L. Every time I’ve noticed a clear dark sky, I’ve nipped out and recorded the darkness, often several times. Using that data, together with concurrent Moon altitude and phase, Sun altitude and angular proximity of the band of the Milky Way, I’ve built a simple statistical regression model to be able to predict what darkness I can expect on a given night. Now that I have nearly 400 data points, the model is usefully accurate. One “darkness-factor” I have noticed but haven’t yet included in the model is “time of night”, to the extent that early evening after dark is definitely brighter at zenith than late evening when everyone’s turned their lights out, so it can certainly be made more accurate. For a moonless night, I can expect to predict a darkness value to within 0.4 magnitudes, and within about 0.2 in astronomical darkness. Milky Way proximity seems to make a surprisingly large difference, up to 0.4 magnitudes.

The chart shows darkness-value (y-axis) plotted against the altitude of the Sun (degrees below horizon). It shows that a typical evening displays a steady darkness-progression as the Sun sinks through the various Twilights, levelling out at whatever the local LP allows. An aside, regarding darkness for places with different levels of Light Pollution: I’ve found that as the Sun sinks through the Twilight Zones, (6, 12, 18 degrees down), measured darkness will be the same regardless of location until the local “LP” level is reached, whereupon the darkness “gets off at its bus-stop” and stays at a certain twilight level. But that’s an article for another day, I think.

No prizes for guessing which the “Eclipse Readings” are. They’re the ones at the far lower right. The red points are the actual darkness readings (LHS), blue points are divergence from predicted modelled values (RHS). When I started taking the readings, the Sun was 3.5 degrees down and the Eclipse was around 75-80% eclipsed. By the time of my final readings, it was 4.9 degrees down and the eclipse closer to 90%. The blue diamonds show that twilight went from over a full magnitude darker than expected, to fully 2 magnitudes darker. This was not noticeable by eye, as the eye was adapting much faster than the light was changing. Another aside: In a full total eclipse, which I experienced near Falmouth in Cornwall in 1999, as totality happened the darkness fell suddenly much faster than my eye could adapt. It really was someone turning the dimmer switch down!  It was like a curtain falling. I’ve not read that phenomenon described for this one yet.

Anyway, an interesting little snippet of data.

Thanks, Magnus

11 minutes ago, Stu said:

Any luck @Captain Scarlet?

An annoying belt of broken low cloud was passing, and luckily because of quite high wind, they were moving quickly. I got literally 5 seconds of a view. By the time I’d brought up my camera to my face, the cloud gap had passed and that was it. But I got to see so I should be grateful.

The twilight-eclipse was around 90% so didn’t in the end noticeably affect twilight, though I did take SQM-L readings every 30 seconds or so, and I expect that data to show extra darkening over expected. I’ll process that tomorrow and post up what it shows.

3 hours ago, Stu said:

Looks like it could be lovely with a sea horizon Magnus. Hope the weather is kind!

Raining at the moment but it is actually due to clear tonight. Fingers crossed.

I think for us in Baltimore Ireland (51.485N 9.346W), we might see the first bite, but totality happens when the Sun is nearly 5 degrees down. However it should mean that civil twilight will essentially go straight to full darkness not long after sunset, so we might see some effect of it. We're not quite far enough West.

Cheers, Magnus

A couple of packages from USA, one from Starlight Instruments and one from Stellarvue, each containing adapters to be able to fit my Feathertouch to my Stellarvue scope.

Storm Kathleen just coming through so it’s going to be a few days before I can give First Light.

Magnus

A few years ago I acquired a 150mm Mak, an Intes M603. It was somewhat “tired”, so I set about freshening it up. I replaced all the screw-and-bolt type fittings, some very worn, cleaned and re-aligned the primary to the focus-tube and otherwise had the scope completely dis-assembled into all its constituent parts.

On re-assembly, just as I was about to re-attach the secondary-mirror unit into the corrector plate, the secondary mirror fell off into my hand! Its glue had lost its stick.

So the whole scope, once put back together, was in a state of completely random alignment. Because it’s a Rumak-Mak, both primary and secondary are user-adjustable and collimatable.

Out of pure curiosity, I decided to have an observing session before any attempt at re-collimation. Just to see how bad it could be.

And it was BAD. During the day, local objects simply would not get sharp. During the night, “best focus” on a star was actually two separate brightish blobs connected by a streak. Out of focus patterns were a horrid hybrid of all the worst aberrations you can imagine. It was fascinating, actually. I drew diagrams of the in- out- and “at”-focus patterns:

When I did collimate it, all became good again and it’s a lovely scope. I still have it. I documented my travails with it

, if you need something to help you nod off 😆.

Cheers, Magnus

An unexpected lovely clear night. I took out my OO/Helmerichs 8” newt on Skytee2. I only really wanted to see 12P Pons/Brooks, which I did and which was splendid as First Light for my Morpheus 12.5 (thanks @bosun21) at 80x.

Jupiter was a boiling mess with a side order of CA (low and directly over Baltimore village).

Sigma Orionis was striking, the sometimes-faint C star quite clear. Trapezium was too low really, E fleetingly evident.

I wanted to see Mu Cephei, Herschel’s Garnet star and very red it was (also naked eye but not bright enough to see colour).

M1 was barely detected, odd as I’d expected it to leap out in 8” of aperture. On checking the secondary, dew was the culprit so I called it a night. Very nice to get out with a newt though.

Just about qualifies for a full report I think after a dearth, to follow tomorrow.

Cheers, Magnus 

On 30/03/2024 at 05:59, josefk said:

I’m flattered Greg by the request but they’re a bit rough so I prefer not 😚

Nice content on your website though and slick YouTube. Kudos to you. 

@josefk you do yourself down. They are true-to-life sincere (and very good) sketches to be proud of, I really think you should change your mind.

( @theskyhound )

M

Finally managed to get the weather to see it. Quite obvious tail through both 15x56 bins and at 36x through 105 scope.

Magnus

So far, Mercury through an actual scope (rather than simply “ticked off” by eye which is what I managed a few days ago) and at 21% phase too and very little atmospheric colour. Very pleased, certainly the best view I’ve had of Mercury ever. Comet beckons a little later 🤞.

Edit: so finally, FINALLY, I bagged the comet after many cloud-foiled attempts. The tail was very evident through both 15x56 bins and at 36x through my LZOS 105. Doubly pleased.

Magnus