Nik271

I think FLO don't normally check the collimation of doublets, simply because doublets very rarely arrive out of collimation. I am sure if there is any issue with the scope they will take care of it.

I managed to see the ray this evening (18 Feb 2024) at about 18:00 with my 102mm ED F7 refractor, using magnification of x120. There was some passing cloud and in the gaps between the clouds the bright ray on Hesiodus floor was evident framed by dark shadows on both sides. It looked to me like a bright door opening on the crater rim and letting the light in.

4 inch secondary, as big as my refractor for tonight! I was also looking at the trapezium at about 8pm and got a hint of E at x185. I find F quite hard even in my largest scope a 7 inch mak.

Spaceweather.com says the region 3576 is 720MH which is about 140 square degrees on the Sun or 2100 million km^2. I tried to picture it as a square: sqrt of 21x10^8 is about 46 000km, so this is a square with side four times the diameter of Earth. Big!

I just had a good look at it during a few minutes of sunshine. Seeing is poor, just can do x50 but yes totally worth it. It's also very magnetically active so may send out a big flare towards us.

I don't mind being confused with this crowd ;)

It's also worth pointing out that angular separation you can resolve depends on the magnitudes of the stars. Bright stars are the best, for example Castor AB at 5'' will look 5x18=90'' or 1.5 arcminutes apart in your binoculars, so you should be able to split it with excellent vision. On the other hand a similar double star pair of say 9-th magnitude and separation of 5'' may be not resolvable. This is because human acuity depends on the brightness of the objects since the retina uses different cells for low levels of light.

I was lucky too with the clouds, it was clear for two whole hours, 7pm to 9pm. Had a brief view of a shadow transit of Ganymede. Very distinct dark dot near the south pole. The wind was shaking the tube of my 102ED so x120 was difficult. Transparency was decent, M42 was showing its 'wings'. Had a brief look at Keid 40 Eridani. The B/C pair were easy to spot near the orange primary but I could not separate the white and the red dwarf from each other. Finally I just cruised the open clusters of Auriga and Gemini. A very windy but satisfying grab and go session.

Yesterday I had a brief window of clear sky between 8 and 9pm. The main goal was to try Eta Geminorum (Propus) with my Skymax 127. This is a rather close and unequal pair ( orange mag 3.5 primary and a bluish mag 6.2 secondary), which has become quite a bit easier with time. It was discovered by Burnham in 1881 and at the time he wrote that "it is difficult for telescopes of smaller than 12 inches in aperture". Since then the gap has widened from 1'' to 1.7'' separation and of course telescopes have become better and now it must be within the abilities of a good 4 inch refractor in good seeing. I started with my usual tests for seeing: Theta Aurigae, which was very steady at x120 (12mm EP) and Wasat (Delta Gem) which was also showing clearly. I tried a few more of my favorites: Alnitak, Rigel, even Sigma Cass in the other side of the sky, all looking well. So I was reasonably confident that Eta Gem is also possible. At x120 I can only see the orange primary. With a 9mm (x165) there was a hint of some disturbance in the first diffraction ring. Finally I went all in with 6mm (x250, about the maximum of the scope). The primary Airy pattern was not so clean and steady anymore but in moments of stability I saw a bump on the west side of the diffraction ring. Here is my sketch, the blue was more of a teal colour and more faint, I could not find the right colour on my sketchpad. Afterwards a visit to the nearby M35 was a no brainer, I could just about fit it all in with the 24mm Hyperion at x65. The transparency was briefly excellent, I could spot the nearby NGC 2158 as a dim gray smudge. And then of course since I am in the neighbourhood I visited M1. It was showing very nicely (for my suburban sky), the elongated shape was obvious and I could see a hint of structure inside. Perhaps my eyes were well dark adapted by then, or maybe the approaching low clouds helped to block the light pollution. Anyway, now is the season when Gemini is high in the sky, so give Eta a try if you can! Clear skies and thanks for reading, Nik

I definitely noticed improvement in contrast when I replaced my basic SW mirror diagonal that came with my Skymax with a dielectric. But even then there is a bit of light scatter around Jupiter. I think the mirror surfaces are not as smooth as in premium scopes, which is fair at this price point.

I believe it's planet X OP is talking about. The problem is that the area of sky the models suggest is too big and the chance of occultation of a star is very small. It's better to look for movement but at these magnitudes (mag 20 or more ) you need big telescopes which means small fields of view, expensive telescope time, so the search is still going on.

Interesting shoot out! You will need a new avatar 🙂 I consider my 5 inch Skymax to be roughly equal to my 4 inch refractor, losing at the wide views but edging ahead of my refractor at planetary. However my refractor is a 500 quid Svbony, about as budget as you can get in the ED class. I'm pleased to see the Skymax is not totally trounced by the Tak. I'm happy to keep both my scopes since they serve a different purpose, if I had a 4 inch Tak though probably I would have reached the same conclusion as you. Nik

Very nice! I like doubles in moonlight. The second one, STF 194 is very impressive for a 100mm scope, on the Raleigh limit. The third one (STF 208 or 10 Arietis) is a bit wider now, about 1.6''. I should try these as a hard test for my 100mm refractor. I also like the 4mm Nirvana in the refractor, found it very sharp and comfortable, giving a sweet spot of magnification on tight doubles.

Perhaps we will see Jupiter with one moon much sooner. I run Stellarium until May watching the moons dance around Jupiter but could not spot a time when just one will be visible. I wonder if anybody has made a study of this.

Thanks Dave, you are a lucky man, there were just a handful of moonless Jupiters in the past 20 years. They seem to be rarer than a total solar eclipse except that of course when they occur they can be seen by anybody on half the planet, whereas a total solar eclipse is visible from a tiny area.

Yesterday at about 6:45pm I had a brief opportunity to observe Jupiter with just one moon visible: Callisto. Ganymede was just eclipsed, Europa was transiting the disc of Jupiter while Io was occulted by the shadow of Jupiter. It was a most unusual sight, I was lucky that the clouds cooperated and I managed to observe it by sheer luck since I didn't check it up in advance. The seeing was decent as well, I could use x140 with my 102mm refractor. This set me thinking: can it happen that Jupiter appears without any moons visible? The wonders of the internet search engines gave me the answer quickly: yes it can happen but not often, only once in a few years. In 1910 an amateur Italian astronomer Enzo Mora computed (by hand!) the dates of such evens for the 20-th century. A later paper by Jean Meeus in Journal of BAA added a list for the 21 centrury (I assume he used computers or at least electronic calculators in 1987). His paper is available here: https://articles.adsabs.harvard.edu//full/1987JBAA...98...35M/0000036.000.html According to his calculations the next such event is in the morning of 28 July 2033 and will be visible from the UK (if there are clear skies of course). It's a long wait sadly. The previous three events in 2019,2020 and 2021 were during the day from the UK. So I wonder if anybody here has observed such an event in the past? Clear skies! ( and especially on 28 July 2033 🙂 ) Nik

Jupiter with only one moon visible right now: Callisto. Pretty rare I think. Europa should come out from in front of the planet any moment now and Io should emerge from the shadow of Jupiter. Cool stuff going on!

The shadows playing on the floor of Plato are fabulous tonight. My seeing is meh, not possible to go over x100 but still plenty of detail visible. The straight wall looks good too.

Nice! Interesting how all cameras are more or less equal at the Moon at this image scale. It's probably the atmosphere that blurs everything equally.

I noticed the Moon is just a couple of degrees from Jupiter tonight. Single shot with Canon 250D, Canon EF-S at 250mm, F/5.6, 1/125 sec:

Yes I think an APO or least an ED doublet is a better choice than an achromat, and not just because of the glass. The more expensive scopes also have better focusers which at F/5 or F/6 is important as the focus point is very shallow.

In Sri Lanka you will have an easier time since Sirius rises quite high. Wait until it is at least 50-60 degrees above the horizon and choose a night of good seeing. Use magnification of at least x200. Your 130mm Newtonian, if well collimated should show it, just make sure the Pup is not obscured behind a diffraction spike.

This article has photos of Sirius B which shows what to expect. The glare of Sirius A makes imaging the secondary very hard. https://skyandtelescope.org/observing/sirius-b-a-new-pup-in-my-life/

Last night I had excellent seeing on Sirius, totally unexpected. My plan was to try to see some detail in the Rosette Nebula with OIII filter and my widefiled scope, a Svbony 102mm ED refractor. I bought this two years ago for widefield so did not expect it to be good on planets - it uses FPL51 glass so at very high mags (180 and above) there is a bit of colour on bright objects. Actually it turned out ot be a decent performer on planets, close but not quite equal to my 127 Skywatcher Mak. The sky was beautifully clear at 5pm but by 9pm when I set up there was a thin layer of haze. Rosette, a difficult target from my sky at best of times, was totally invisible, so change of plan was needed. On a whim I swung to the nearby Christmas tree cluster. The brightest star there, S Mon, is a tough double ( just under 3'' separation and 3 magnitudes difference between the primary to secondary). With a 4mm Nirvana giving x180 I had no trouble splitting it. The seeing was extremely good, the primary dispalying a perfect diffraction pattern with the secondary nesting next to it. This is when I regretted that I haven't taken out a larger aperture scope on the EQ5. Instead I had the 4 inch refractor on AZ5 on an adapted surveyor tripod, good for grab and go but not ideal for high mags. But it was too cold to fiddle with cold metal when changing scopes. So the refractor had to be. After a quick look at my other test for Sirius: Alnitak and confirming it was an easy split in the seeing I swung down to Sirius who was just showing over the rooftop. Immediately I recognized I was in luck: Sirius was steady and displaying multiple diffraction rings, surrounded by a faint violet halo (FPL51 doublet, no surpises here). After relaxing my eye and manually tracking with frozen fingers I became convinced that I see a faint dot about north east of Sirius. To make sure I switched to a 3mm LER and the Pup was easier to see, popping in and out of my vision. It is no longer directly following the primary but it has moved further north of east. I have had easier splits but with larger scopes. So this is my personal best for smallest aperture showing the Pup 🙂 It just goes to show that seeing is king for splitting doubles, especially for Sirius. Here is a picture of my new Sirius B spotter scope. It's waiting for a gap in clouds 🙂 Clear skies! Nik

Note that the rear 100mm of the tube is removable, so in that configuration the scope with contracted dew shield should be just 60-10= 50 cm long, so should fit in cabin luggage. My only concern for portability is the weight, about 6 kilos. I wish they made an FPl 53 doublet in the same body,