allworlds

Kellners have has three elements - a single "field lens" and a cemented doublet "eye lens". The Skywatcher stock eyepieces are "modified achromat"; same general layout but a bit different on the lens shapes. Both designs are OK. Then Konig and RKE are also three-element designs but the other way round, doublet field lens and singlet eye lens. The main 2-element designs are the Huygens and Ramsden and they're kind of rubbish. It doesn't help that when made nowadays they are virtually always made as cheaply as possible.

Is it not said that for something to be art it must have no practical use other than being art? If so, well I shan't name any names but I'm sure we can all think of some telescopes that are art 😄

Word is that whatever it was, it's back down at mag 16 or so now. https://www.physics.purdue.edu/brightsupernovae/novae.html#NM332211a

Ooof. You can make a helical focuser from plumbing parts, here's a post outlining how somebody made one, https://stargazerslounge.com/topic/53836-diy-helical-focuser/ Plastic or metal will work - it just needs one pipe that holds the eyepiece and screws into another pipe that's fixed to the telescope. Might take a bit of experimenting to get all the lengths right. You can of course buy a focuser, but delivery times might be slow.

I can't find where but I have read that it doesn't work in the filter thread. I think the eye astigmatism correction needs to be on collimated light as produced by the EP, not on light that's coming from/to a focus as it does between the objective and EP. Makes me wonder if theoretically you could correct eye astigmatism before the objective? Impractical for all but the smallest telescopes but for binoculars the correction lenses would be reasonably sized. Has it ever been marketed? But yeah. Other than general Tele Vue quality (and any patents they might still have) there's nothing magic about it. An eyeglass lens appropriately fixed to the EP will work, though I'm not sure if off-axis segments would behave well.

Thanks both. In the end I got none of those. Wex had only one in my price range on display and Currys had none so I made the drive out to Sherwoods Photos where they had a bit more choice. I got a pair of Hawke Vantage 8x42. I also checked out a Hilkinson pair and couldn't see much difference optically. No super-wide field but plenty of eye relief which is going to be what's more important.

Hopefully he gets on well with it. The mount's great, I got a lot out of my Heritage 76, but I think the Huygens eyepieces on most of the Celestron versions are an economy too far. A decent 5 or 6 mm EP is a worthy addition to get about the most magnification the spherical primary is good for.

I previously owned cheap 10x"50"s (the sort that are really more like 10x40) that went out of collimation. I now want something a bit higher quality and I fancy dropping down to 8x40 for a bit less weight and shakes and a bit more field of view. I anticipate using them for scouting star hops and panning the Milky Way more than for hunting specific faint fuzzies. I've budgeted £75-125, plan to try them out before I buy, and am looking out for Black Friday deals (although here in the UK the "deals" are mediocre, it's more like Light Grey Friday...) Celestron Nature DX 8x42, Celestron Outland X 8x42, Pentax SP 8x40, Olympus 8x40 S, Opticron Adventurer II WP 8x42. The Pentax and Olympus advertise a great 8.2 degree field but I wear glasses for astigmatism so I'm not sure about the eye relief on them. Hence the others which advertise longer eye relief.

Discovered at mag 13.4 apparently in M33. I wonder what it is? Too bright for a regular nova in M33 (that would be more like mag 17). http://www.cbat.eps.harvard.edu/unconf/followups/J01350893+3031503.html http://xjltp.china-vo.org/psp22aj.html

Wasn't there a thread on these forums for people imaging with the EQ3-2 or CG-4 ? It's not the best mount but IIRC it's doable with a small scope (OP has an 80 mm apo). Anyway. With just tracking the telescope follows the movement of the sky but there are inevitably errors. It's motors and gears and polar alignment and nothing is ever perfect. If you try too long of a sub unguided you'll see stars becoming oval instead of staying points. A guide camera creates a feedback loop to correct those errors, driving the motors a little more or a little less to make sure that the stars stay in the same place (to within the system's precision) in the camera view. Does your mount currently have a motor drive on both axes? If yes, is there a guiding port or similar for those motor drives? If yes to both then the benefits of this kit by itself will be miminal.

A fairly small difference in all regards. But a subjective factor in favour of the 6 inch (the 150P): traditionally a 6 inch reflector was the smallest of the "big scopes", whereas a 5 inch is the largest of the "small scopes". You'll see that reflected in Sky at Night magazine's observing guide and in various guidebooks. Of course your observing site and own experience are huge factors but the 150P might give you that bit more confidence going for suggested things to look at. The 150P's also the biggest of its type and to get more aperture currently means a significant increase in size and/or cost; the 130P almost seems like second best now. I can't find a side-by-side comparison of the two, either observing reports or even physical dimensions, unfortunately. On the other hand, I started in astronomy with binoculars. For a new starter with a budget of £240 and no more, I think the 130P and a 50 quid pair of binoculars is a better overall prospect than just the 150P, if you don't already have some binos. If you have constraints on overall size, maybe you need to fit it in a particular suitcase or something, then the 130P may win too. On the other end of the scale, if you can nudge the budget up and size isn't a major factor, you could go for a floor standing 6 inch Dob like the Ursa Major (£260) or Skywatcher Classic (£300).

The Moon's sometimes underrated. It's one of the (apparently) largest and most detailed things you can look at and I really sense that I'm looking at another world, not just a little disk. It changes each day too as the terrain near the terminator (the boundary between the lit and unlit parts) is shown best. And as the images above show you can get a nice snapshot with a smartphone. Phone imaging of planets and DSOs is possible but more difficult, a good camera app is recommended and the images tend to not be the most visually stunning, but the flipside is they can have more of a "this is what I saw" quality - a closer similarity to the view seen visually.

Nice and clear early evening in Birmingham. Started things off with an ISS pass. Fairly low and this was a "fade out" pass. The ISS went impressively red as it passed into Earth's shadow before fading to invisibility. I was spotting satellites through the whole observing session - naked eye, in the finder, and even one or two zipping through the eyepiece view. Then time for a spot of DSO hunting with the ETX 105. Found Albireo more by luck than judgement and that was my "anchor point" for viewing in Cygnus and Lyra. M57 was easy with direct vision and upping the power to 75x made the ring shape evident. M56 was more difficult before I had a "there it is!" moment while moving the scope a bit. Invisible with direct vision and merely suspected with averted, it was moving the scope that really seemed to make it stand out. It was next to a faint star which if I'm checking Stellarium right might actually have been a cluster member? By the time I reached the double double half my aperture was blocked by a building, as betrayed by the shape of a very out-of-focus star image. At 200x the southern member was elongated but not a proper split and the northern not split. Mirror shift was a right so-and-so too. Finished with M29. Not many members visible, but even though it's in a busy patch of the Milky Way it's sort of set aside a bit, the little square of stars did stand out and a check on my phone confirmed it was the cluster. I didn't feel like looking at Jupiter, and Mars wasn't high enough up yet. I'm getting the hang of the scope. Turn Left at Orion, along with practicing my star hopping in Stellarium, is working well and even though the finder is tiny (8x25) it does OK. The initial pointing is still troublesome though with the finder being right-angled. I might try and knock up a peep sight, all it would need to do is get a target star in the finder FOV.

That Great Weatherell Refractor @Steve Ward posted, that's a good look. As far as modern stuff goes, yeah I think Vixen fracs just have a certain something about them. I dig Explorer Scientific's BT series too. Similar aesthetics to the Vixens but two tubes is twice as good right ?

That could be anything, or an artefact. It's not obviously identifiable and there's no context, no visible stars, to know where it's located.

The OTA vlaiv and Zermelo have discussed. When I asked FLO they confirmed the Starquest version of the 102 Mak isn't user-collimatable, not that Mak-Casses are likely to need it. Here's the Cloudy Nights folks getting up in arms about it and also describing a possible workaround, https://www.cloudynights.com/topic/732639-no-collimation-screws-on-skywatcher-102-mak/ On the tripods, I'm just going by the photos. "Box section" aluminium tripod legs in the package: https://www.firstlightoptics.com/maksutov/sky-watcher-skymax-102s-az-pronto.html versus round aluminium legs (and an extension pillar) when bought as mount+tripod alone: https://www.firstlightoptics.com/sky-watcher-az-pronto/sky-watcher-az-pronto-alt-azimuth-mount-tripod.html I think Skywatcher don't do that on the AZ-GTi ones actually, but I'd still urge checking before buying.

I bet a little insect could crawl through the gap between the primary end cover and the tube. Or one just flies in while you're changing EPs?

Almost any binoculars are of some use. 8x30 is a bit small for astronomy but Zeiss are a premium brand so the views might well rival cheap larger ones. 7 to 10 x magnification (fixed, not zoom!) and 40 to 50 mm objectives are good “every astronomer” binoculars. Much larger or higher magnification and they can no longer be handheld, a tripod or mount is needed, which means they’re really more for the enthusiastic binocular astronomer. Be aware Egypt is among the countries that are iffy about binoculars. Questioning and confiscation upon arrival are possible. Their laws and authorities regard them less as tools for birders and astronomers but more as tools for spies and criminals. (A few places such as Algeria virtually ban binoculars). So I would leave the Zeisses at home and take a budget pair.

The Skywatcher and the Zhumell are very similar and will give the same views. The Heritage 130P has been around for ages and is well regarded; the collapsible tube makes it store more compactly but not everyone likes its helical focuser. The Zhumell has a rigid tube and a more conventional focuser. IMHO unless you really like the idea of the flex-tube, just get the one that's more available or/and cheaper from reputable astronomy retailers. The Starblast refractor is optically worse with less aperture and strong chromatic aberration, and I'm not convinced by photo-tripod-style mounts. The refractor is suitable for terrestrial viewing as well as astronomy if that's something you want, whereas the other two are really just for astronomy. The three are pretty much equal on weight and portability, with the Heritage 130 being the most compact to store, but all of them would not be hard to carry down stairs or on public transport.

Keep in mind that the Skywatcher packages tend to come with cheaper tripods, whereas if you buy a mount+tripod without scope the tripod is usually a higher quality one. The OTAs are sometimes “cheaped out” too. Notable with the Skymaxes - lighter rolled steel tube and no user collimation on the package version, vs higher quality tube and collimation screws when you buy the OTA by itself.

I have a similar scope to the one vlaiv posted, though on an alt-az mount. I find it quite challenging to find things with because the long focal ratio and only accepting 1.25 inch eyepieces makes it impossible to get a wide field of view. The Moon and planets are easy to find (and look great) but hunting down DSOs takes me patience and detailed charts. (Edit: Turn Left at Orion has proven useful but I still find myself checking with some star charts that go down to mag 8.5 stars.) A Newtonian reflector is typically better in that respect. Skywatcher sell a 5 inch Newt and a 4 inch short-tube refractor on that same Starquest mount. (The refractor is perhaps even better at widefield than the Newtonian, but will show strong chromatic aberration at high magnification.) Ricochet raises a good point about whether your son's dyspraxia would affect him using a Dobsonian, which is the usual "default" recommendation. Positive of a Dobsonian is it is simple, conceptually and mechanically. You know your son best, so you'll know if he'd be better off moving the scope directly (a Dobsonian), using mechanical knobs for the fine movements (a mount with slow-motion controls), using a handset a bit like a TV remote (older Goto mounts), or using his smartphone (new wifi Goto mounts).

Old thread, but I think you're mistaken in attributing an inversion to the eyepiece. It's cameras that invert the view in software compared to what is physically on the sensor, to undo the inversion that's caused by a normal camera lens. (With an SLR's optical viewfinder, the reflex mirror and pentaprism sort the image orientation out.) Eyepieces magnify the image without inversion, as can be seen by a ray diagram such as https://i.stack.imgur.com/PHzEC.gif, My claim could be tested by putting a sheet of tracing paper (or a ground glass pane if you have one) at the focal plane to directly observe the real image.

Yeah. A Newtonian-type telescope (including things like Bird-Jones and Maksutov-Newtonian telescopes) will produce a rotated image, but exactly what the rotation is depends on the orientation of the eyepiece and the observer's eye. It's not really practical to get a correct image with one. For astronomical use I pretty quickly got the hang of it.

What do you currently have? I have a 4 inch Mak-Cass which has impressed me on planets, yet to really test it on DSOs though. I think Graham covered it fairly well. Maks and SCTs do offer good aperture in a small package, though the ultraportable Dobs have them beaten I reckon and the cooldown undermines grab-and-go potential somewhat. The long f ratio means no widefield but does mean eyepieces won’t show aberrations so much - but if your eyepieces are also being used in fast scopes that’s less help. I dare say that in terms of *quality* of view a good Mak-Cass might be second only to a good apo refractor? No coma, no diffraction spikes, small central obstruction. But Dobs have raw aperture on their side and diffraction spikes and coma can both be eliminated if you don’t like them.

Thinking just about visual use, chromatic aberration in the scope won't help. You might find an aperture mask improves things, make some out of black card of various apertures. A minus-violet, contrast booster, or similar filter can also help. Imaging adds a whole nother level of complexity, but if the belts are *difficult* to see at 66x with your eyes then that's not a good foundation as it were.