John

Thanks - a 1.1 arc sec separation in Scorpio - that should be fun 🙂

I think our brains flip the image that our eye projects onto the retina. Who is to say what is "reality" ? 🙂 Hope you enjoy your new diagonal 🙂

I "borrowed" it from this CN thread: Anatomy of a 20mm Erecting-Eyepiece - Eyepieces - Cloudy Nights

According to the Stella Doppie database, there is nearly 1 magnitude difference between the stars of the close pair of Tegmine. I wonder, at what point is a brightness difference going to start adding to the challenge of splitting these stars ? Does anyone know of a more equal pair of around the same separation ? - it would be interesting to compare those with Tegmine.

If the eyepiece is one of the 20mm erecting eyepieces, the optical layout looks like this: So the top lens in this case would be concave side towards the eye and convex side downwards. These top lenses do fall out easily apparently so you are not the first one that this has happened to 🙂 If yours is a different sort of 20mm eyepiece, let us know and I'm sure someone will be able to advise further.

I'll be interested to see if there are conditions under which a good 4 inch can get a definitive split of the close pair of Tegmine. As someone else said in this thread, seeing any stars at all has been a challenge over the past months, let alone actually splitting these close ones 🙄

It might be difficult to split them without damage - the 2 elements are cemented together and the cement is quite tough. Best leave that pair to see if the moisture will evaporate naturally I think.

One part that I omitted was that even after collimation of the SCT my ED120 was putting up sharper views of Epsilon Lyrae with 4 perfect airy disks while with the (collimated) SCT the stars were still a bit fuzzy around the edges. At least they were clearly split now though.

Here is one example. At an astro society observing event, I looked through an 8 inch SCT that could barely resolve the pairs of Epsilon Lyrae. The owner seemed to think the performance was OK but we did a star test and found the collimation a little off, not massively but definitely off. We adjusted the collimation and got a decent star test after a few tries. Both pairs of Epsilon Lyrae were duly properly, and rather nicely, split which seemed to rather surprise the scope owner. He later subsequently (a few weeks later) told me that the scope was now clearly showing Jupiter's Great Red Spot and Saturn's Cassini Division whereas he had not previously aware of these features being shown. Sometimes, it takes a look through someone else's scope to realise that yours perhaps has a little more that it could give 🙂 A lot of observing (probably the majority ?) goes on solo though so it is very helpful to read reports from other observers on places like SGL to get a feel for how you and your scope are doing and how hard you are pushing it. It is also reassuring at times to know that poor seeing is more likely to be the cause of lacking performance, if reported by others in your part of the world.

I've ordered the Svbony 7-21 to give it a try. It will be good to see how it compares with the 3-8mm. I have a nice Parks Gold Series (Japan) 2.2x barlow to use with the zoom to compare the shorter focal lengths including the Nagler 2-4mm zoom. Should be interesting 🙂

Are you seeking evidence, or otherwise, regarding the need for accurate collimation ? I'm curious about the purpose of your question that's all ! 🙂 Anyway, this thread covers some points, with examples, and is only a few months old so worth a look: Laser Collimation Guide for Newtonians - Discussions - Scopes / Whole setups - Stargazers Lounge I've found that some refractors need collimating as well, although it's usually a one-off process.

One idea would be to go along to a show such as the International Astronomy Show where lots of vendors and some manufacturers gather under one roof. You could broach your ideas with a number of people at the same time, to test the water 🙂 Vendors – UK Astro Show

In the past OO have been prepared to undertake bespoke requests. No sure what their position is now though. It's not just the cost though, you might have to be rather patient to get the instrument as well 😉

I'm in the same camp as @Stu on this one. High quality standard prism or mirror diagonal for me and I accept the L&R reversed views. Stellarium and Cartes du Ciel have fairly easy to use facilities to flip the image E&W / N&S / both and I'm sure other such tools have a similar function somewhere.

Orion Optics primary mirrors tend to be thinner than most, and therefore lighter. One of those honeycomb or strut back type designs is needed to lighten further I guess. Skywatcher use something like that on their 14 inch and upwards dobs I seem to recall.

Congratulations and thanks for the interesting and helpful input to SGL 👍

Poor Zaphod - he and Ford Prefect grew up together on a planet in the vicinity of Betelgeuse 😬 Still, he would have wanted to go out with a bang 😉

Nice capture 😀 I managed to snap it once back in 2020 with my old mobile phone at the eyepiece when it was close to Venus in the sky. Nowhere near as nice as your shot but at least you can just about see a phase:

Very interesting images Ian 🙂 I must dig out the sketches I made of Zeta Herculis when I first split it and more recently. I recall that those showed a noticeable change in position angle over a period of a few years as well. Unless it was just my lousy sketching 🤔 The Universe in motion - great stuff 🙂

Sounds lovely Neil ! It's a pity that this comet is really badly placed for me. I've managed to catch it with binoculars and my 4 inch refractor a couple of weeks back but the part of the sky that it is currently in is just about the hardest for me to get a clear view of from home. No opportunity to take a scope somewhere else currently so I'm having to enjoy it vicariously through reports such as yours 🙂

You should get good views of your targets of interest with both those scopes. Patience is needed with the planets though, because they are not always in favourable observing positions. Photos can be misleading because the camera can often capture more than the eye can see. Have a look for sketches done with similar scopes for a more accurate guide to what might be achievable visually. For the Sun you must use a suitable solar filter of course. Apologies if you know this already.

I've been doing a few measurements of where eyepieces reach focus. Of mine, the Svbony 3-8 zoom is the one that needs the most inwards focuser travel and the TV Panoptic's (and other TV par-focal group "b" eyepieces) need the most outwards travel. With the scope that I have been testing with (a long focal length refractor) the range of focuser travel I needed to accommodate the needs of both extremes was ~16mm when the scope was focused on Polaris.

I'm not sure that the ES Ultra Light's are any lighter than the Skywatcher equivalents 🤔 It's worth checking.

Good luck Dave ! Nice avatar by the way - one of my favourite albums 🙂

Just my thoughts as well 🤔