badhex

One thing I forgot to add was a grab from Stellarium showing the position of Rhea aat the approx time of viewing:

Thanks Paul, pretty happy with the night, especially seeing Rhea. I also can't wait for darker nights - every little helps in the city.

Haha impressive! I will get back to it one day 😂

Welcome back! Sometimes it's easy to feel down about learning and forgetting stuff, or not feeling up to going out to observe, but don't worry about it - I started with this hobby over ten years ago and got to the point of grinding my own mirror for a dob, until I moved countries and ended up doing not doing any astronomy for nearly 5 years and forgetting most of the night sky, until got the bug again and have been back with a vengeance ever since. Just enjoy the hobby and do what you can!

Haha thanks Mark, potato was what I wrote on my notes! Perhaps I've seen The Martian too often 😂 I'm in a city (Berlin) although not the centre, so it's nearly, but not quite, as bad as it gets - I'm also only using a 102mm frac, and @Epick Crom commented on a previous post that it was only just possible for them under Bortle 6 with a 10' dob and averted vision. I had also tried for Panstarrs once before with a ZS73 under Bortle 4 (and some moon) back in June, and I couldn't get it then either.

Had another clear night on Saturday so had another crack at C/2017 K2 Panstarrs, with even less success than last time! More successful were some observations of the giants Jupiter, Saturn and Uranus, as well as my first time observing a Saturnian satellite other than Titan. As always, wordy version is here:

Great report! Welcome to SGL 🙂

Hello all, Another clear night so thought I'd I try again for C/2017 K2 Panstarrs with a backup plan of the gas giants, which should be better placed as it was later in the night/morning. Well, it's a good job I had a backup plan as Panstarrs was a total bust. A combination of factors - transparency, Ophiuchus being lower and further west over a more densely populated area of the city combined with the moon being higher up - meant I could not even find M10 as a guide post. The less said the better! For some more reliable targets, I moved first over to Jupiter, switching up quickly to my favourite combo from the last session - a barlowed BCO 10mm (179x). Seeing was pretty good but not perfect, and similarly transparency was not perfect but actually I think this helped. Lots more detail than last time and I spent a long time there. I had managed to dial in focus very finely by clamping down the focuser lock so the fine focuser moved only a touch each time. The NEB was almost cutting across Jupiter like a canyon. SEB typically less visible but phasing in and out. All four Galilean moons very visible. Due to the location of the moon and height of the tripod I rotated the focuser so I was facing away from the moon, which meant Jupiter was almost but not quite upside down. Not my preferred view for picking out features, but still lots of detail visible. At this point Saturn was out from behind the buildings, so again after locating I switched up to the 10mm BCO + barlow. Pretty steady seeing here, and plenty of detail despite the proximity of the moon. Cassini division not visible at all times, but popping into view regularly. A darker shade of atmospheric banding visible about halfway between the north pole and rings. Do we call that the Northern equatorial belt, same as Jupiter? I guess so. Titan was very visible as always, but this time I also picked out Rhea at about the 11 o'clock position! This marks the first time I've seen any other moons of Saturn, and may have muttered some exclamation to that fact. Initially I was only able to pick it up with inverted vision, and then later able to find it directly. It never ceases to amaze me what hidden detail we find with extended time at the eyepiece. After checking with Stellarium which moon I'd seen (I'd never have known it was specifically Rhea) I mentally noted the positions of Dione, Tethys and others and even tried letting Saturn itself slip off the edge of view to see if any other moons were detectable, but did not pick any others up. I was starting to get cold, but on a high from my personal discovery of a new gas-giant satellite, I decided to try for Uranus which was well risen at this point. As usual I started with the 40mm and a rough point to the correct area of sky, whilst consulting Stellarium once more for way points. In a rare case of Starlink being useful to Astronomers, a train of 5-10 satellites were due to pass incredibly close to the planet so I ended up finding it really quickly. Again, I switched to the current favourite combo for planetary work, barlowed BCO 10mm giving 179x. I was able to resolve the ice giant to a tiny, pale green-blue ball, much different to the stars nearby. First time I have definitively located Uranus without a goto mount, so once again very pleased with this outcome. As it was now hopefully high enough and out from behind a massive crane, I figured I also might as well try for Mars, then bed. With the same planetary combo, Mars was clearly about three-quarters and gibbous. Unfortunately lots of shimmer and colourful fringing from the atmosphere, but a dark central patch was visible, with maybe some bright poles? Overall it was a bit of a mess - like a small red potato. The night was clearly the night of the Giants!

Okay, makes sense that I was struggling with then with only 102mm of aperture!

Thanks Paul, yes Ophiuchus is not really well placed for me either - low and over the city - which is part of the problem I think. I wish the picture was mine but its just a snap from Stellarium with the GRS right where I believed I'd observed it at that time 🙂

Thanks Epick, what size scope were you using? I tried again last night but ophiuchus being lower down (I was out later), plus transparency and the moon meant I struggled to even find the right area of sky!

Thanks Mark for looking, appreciate it. I did actually try the larger of the two retaining rings when I first discovered the issue, and it's actually just a flat disc threaded on the edge, possibly so they could use the same EP body for different FLs. It does appear to be functional in the construction as such. The fields lens does have its own retaining ring underneath.

I got the APM version of this earlier this year, excellent bit of kit!

Thanks for reading!

Haha thanks, I always like to give folks the tl;dr highlights in the other thread with the option of a wordy version here 😅

Had a go at C/2017 K2 Panstarrs the other night unfortunately to no avail, but did have more luck with Jupiter (no surprise there!). Wordy version here:

Hello all Went out on the night of the 14th to attempt C/2017 K2 Panstarrs with my TS102 whilst at its closest approach. After a few mins M10 was easily found in the Lacerta ED 40mm at 18x. I framed up the area and variously switched between the APM 24mm UFF (31x), Morpheus 17.5mm (41x) and Pentax XW 10mm (71x) to try and find the right balance of background contrast and light gathering. Definitely in the right place, but not convinced I really picked it up even after around an hour or more of trying, even with averted vision. By 0100 the moon had appeared from behind a building and was starting to kill the contrast even more, so I decided C/2017 K2 Panstarrs was not to be under Bortle 7 on a basically full moon! I may try again with the C5 or from a darker location before it departs. A bit disappointed with my rubbish skies, I switched to the other side of the sky for a somewhat risen Jupiter, clocking an unknown double by accident whilst panning around. With the 2.5x barlowed 10mm (179x) and non-barlowed 4.5mm (159x), the equatorial belts were pretty clear, but somewhat wobbly seeing meant the SEB was less so a lot of the time. Clouds turned up not long after. Moved over to the Double Cluster while I waited, with the 40mm, then the 24mm. Really very beautiful in the 24mm. Switched up to the 17.5mm for a touch more contrast. Moved back over to Jupiter once the clouds had cleared, seeing a touch better. Convinced I saw the GRS but hastily-googled tables say no transit at this time. Switched out to my BCO 10mm with 2.5x Barlow (179x). Very nice views during moments of clarity, the BCO proving itself once again - I thereupon made the decision I should probably upgrade my GSO Barlow to a Powermate for the coming planet season. The lower SEB was looking distinctly humped and GRS-like in moments of clarity, and I noted it was almost at the midway point of the belt at 0144. Moon was now causing a loss of contrast due to local LP and the clouds came back so time to call it! Once back inside, I checked Stellarium - which I have previously distrusted to give me accurate GRS transit info - and this is what it showed at 0144 for Jupiter: Still pleased with a few hours observing despite no Panstarrs, I went to bed happy!

Actually, they will move out of the way if turn the EP on its side and gently tap it, and just as gently turn it back upright and into the focuser. It actually took me a few goes to get all the bits into the FOV for the photos 😂

Thanks Mark. The link I posted to the Japanese page has photos of many of the variants, so I'd be interested to know if any of yours are the same era as mine. You can see that the font appears to be lighter weight in the early '70s examples of this design which matches mine. I think you might be right about the retaining ring, I've had a look close up with a camera and it does look like chipped paint:

Thanks Dave, you could right about the paint, it's very lightweight and clearly fragile as it is in at least four bits. Re the field lens, I'd need a lens spanner with long, thin and straight shanks which should be possible, but it's quite awkward to get to so might end up being quite specific. I'll see what I can pick up online, hoping not to spend too much more money though 😅

So I managed to give the Huygens a quick test in the daytime to see how it performs in my F7 TS102, and I have both good news and bad! The good news: So, obviously not a completely fair test as it was daytime only, but I was surprised at how well it performed even at F7, especially given that I was expecting it to be a total mess. Quite a 'natural' sort of tone to everything with very little CA (except for the field stop which is essentially a purple halo). Pretty sharp across the centre 50-60% of the FOV, and eye relief was copable. Field stop reasonably defined, when you can position your eye correctly. I tried it with a 2.5x barlow making the scope F17.5, and the view was even better, as expected, but with a small amount of rectilinear distortion. The bad news: First viewing was fine, but after having taken the EP out to rearrange the thumbscrews for the various adaptors needed to get from 2" to 0.965", suddenly there was a large black artifact in the FOV! I checked again and realised that there were around four pieces of detritus freely floating around inside the large gap (per Huygens design) between the eye lens and field lens. I'm not sure exactly what they are, but they look slightly curved, and if I knew exactly the construction of the EP I might guess at a perished washer or spacer from the field lens or maybe where the metal barrel meets the upper Bakelite part of the EP. Photos included at the bottom of this post. I did test to see if the metal barrel would unscrew like is commonly the case but it didn't want to budge with moderate hand force, and I as I don't know if it does actually unscrew I don't want to force it and destroy the EP. My other options appear to be using a small lens spanner to unscrew the eye lens holder which is bakelite and possibly fragile (already seems a bit chipped), or unscrew the field lens which is about 2cm inside the barrel and not easy to get out or put back. I also don't know if the spacing between the two lenses is set by stops within the body of the EP, or whether it is determined by how far you screw in each of the parts. Nightmare! It's a bit of a shame as otherwise this EP is in good condition for its age and its entirely possible that the seller was not aware of the problem. I took a bunch of pictures and thoroughly inspect the EP on arrival and did not see anything so I'm not going to go down that route. Any thoughts or advice on how I might proceed to fix this would be welcome! Chimney in focus with detritus in FOV With 2.5x Barlow

Thanks Don, I've been recommended his business before on SGL actually but had forgotten about it. Looks like some good quality kit.

Thanks Louis. I can give the EP a try with my 1.25" Barlow and an adaptor for now and see if it cleans up the view a bit. I have already seen one Celestron 0.965" long barlow which looks to be quite a lot better quality than the usual cheap plastic ones, but I'm never really sure what constitutes a reasonable price for a lot of the 0.965 stuff, as there's so little info on it.

Good spot, thanks!

As other have mentioned, I haven't followed every single post so maybe this has been discussed, but I have a question: So, in a conventional telescope we can correct for many aberrations created by the optical elements, e.g. CA by using multiple objective elements or Coma with a Paracorr etc. If, like the JWST we are using a large gravitational body such as a galaxy cluster as one of the optical elements in our train, clearly we cannot create a physical corrector as this would need to be different for each different gravitational body we use. That said, if we know the data representing the physical properties of the gravitational bodies we are using as an optical element, then surely a model can built using that data to then transform the images digitally, after the fact, and restore some of the shapes and positions of the smeared galaxies we see in the JWST images? Like a sort of digital Paracorr or field flattener, let's say? Obviously, such a transformation could not restore data that was not captured, much like there are limits to taking a small low res image and trying to make it larger - the information simply was not recorded in the original image, but perhaps we could grt some of the way there? Maybe this is nonsense, but would love to hear from people with a better understanding of the physics than I.