Zermelo

The stock 10mm eyepiece isn't great, though the poor view may be due to a low elevation - Jupiter isn't as well placed as it was. The Starguider range has an 8mm and 12mm, no 10mm. There are some here: https://www.teleskop-express.de/shop/product_info.php/info/p4931_TS-Optics-1-25--ED--eyepiece-12-mm---60--flat-field--long-eye-relief.html though they look pricey compared with FLO? In the U.S. look for Astrotech Paradigms.

I don't know how I missed your first review, Louis, but I could just have referenced it in mine, and saved on some typing. The test images are interesting, as ever, particularly the comparisons with the 5mm and 8mm Paradigms (the same as our Starguiders, of course). The one point I might disagree with you is where you say "as its price decreases from its initial offering" ... I suspect the price may go up, as more reviews get written 😃

Have a look here: https://stargazerslounge.com/topic/376745-a-record-of-the-accuracy-of-my-local-cloud-forecasts/ I have 5 or 6 that I consult. Actually, it helps to have an odd number, because they usually disagree, and you'd then have a majority decision.

I've read several descriptions of ghosting, which is why I wanted to be clear with mine. I didn't observe the effect in quite the way you describe, because my mount was tracking, but I'll try turning it off next time I'm out. Although I'm sure that what I'm seeing is derived from the bright object in view, I have never seen it as a duplicate image of the same size, or with any detail corresponding to the original object. It is always somewhat larger, and in some cases approaches the size of the entire field. But it always has the behaviour of moving in the opposite direction of eye movement. Ah, OK. So what I'm seeing is not the result of external corneal reflection, just internal. I lifted that simulation from a CN thread on ghosting. I suppose it actually shows both scatter and ghosting. The disc-shaped, off-centre effect is what I'm referring to as ghosting, but the diffuse, edgeless glow, symmetrical about Jupiter, is the scatter. Thanks for your comments, Don.

I finally got around to doing a review, here: https://stargazerslounge.com/topic/406326-svbony-sv215-3-8mm-planetary-zoom/

Purchase I ordered my zoom directly from Svbony, at a cost of £105.91, plus £20.92 for shipping and taxes. This was the “duty fully paid” price, though you can choose to skip the taxes and settle up when it arrives (or not, according to your luck). I pre-ordered and it took about four weeks, arriving in time to be a Christmas present. Some filthy weather followed, delaying my chance to test it out. When it did clear, there was a succession of very cold nights, and I tried it out on eight occasions during January. Observing Location All sessions were conducted at the same, semi-rural, mid-Bortle 4 location. The darkest SQM reading was 20.75, when the moon was absent. Observing Conditions The temperature over the eight sessions ranged from 6°C down to -4°C. The moon phase ranged between 0% and 91%, but several of the sessions coincided with nights lacking a moon. Relative humidity ranged from 56% to 86% (no obvious dew was observed during any session). Seeing varied from Antoniadi IV to II; where significant, specific conditions are mentioned below. Transparency varied from 4/7 to 6/7; a persistent hazard in the cold weather was smoke from nearby houses in specific directions. OTAs Used One session used a 150mm F/5 Newtonian, two sessions a 102mm F/5.9 achromat, and five with a 127mm Maksutov, approx. F/12. Where a specific OTA is not mentioned for an observation, the Mak is indicated by default. While the slower focal ratio of the Mak tends to reduce differences in performance between eyepieces, it does have the advantage of introducing fewer aberrations of its own, compared with, for example, the CA in the achromat and coma in the Newtonian. Comparison Eyepieces The following eyepieces were used in comparison observations, some more than others: Baader Morpheus 9mm BST Starguider 8mm OVL Hyperflex zoom 7.2mm-21.5mm (used at 7.2mm) ES 82° series 6.7mm Baader Morpheus 6.5mm BCO 6mm BST Starguider 5mm BCO 10mm + x2 multiplier (hence 5mm equivalent) OVL Nirvana-ES 4mm Of these, the BCO 10mm is probably the sharpest on-axis. Other Equipment Baader semi-APO filter Astronomik UHC filter The refractor was used with a 2” quartz/dielectric mirror diagonal. The Mak was equipped with a 1.25” Takahashi prism. With its short focal lengths, the zoom will mostly be used unenhanced, but a brief test was conducted with an Altair x2 telecentric multiplier. The Observer … … is as important as the other components in the optical train. So, for the guidance of the reader: Experience: I have completed around 150 observing sessions, including 1800+ observations. I have so far seen 100 Messier objects and split doubles down to 0.9”. Corporeal status: my eyeballs are the wrong side of fifty years old. In my Bortle 4 skies, I can’t see much beyond +5 NELM. My observing eye (when examined 18 months ago) has astigmatism of -0.75 cyl. I’m not aware of any other defects. Results I couldn’t decide whether to order the comments by target object or by defect type, and ended up doing a bit of both. Physical Attributes The eyepiece is compact, and quite heavy for its size. It looks and feels solid. The rotating zoom action is smooth and easy to operate, though the final step from 4mm to 3mm requires a little more torque, since the leverage is increased. By comparison, I found it easier to adjust than my Hyperflex 7.2-21.5mm. Zooming in cause the eye lens to rise on a central stalk, in the same way as the Televue Nagler zoom. The click stops are obvious without being overly severe. It was easy to keep track of the focal length in the dark by counting the stops from either end of the range. There was no noticeable stiffening of the mechanism in sub-zero conditions. In each of the three OTAs the eyepiece was held in different compression rings, and with moderate tightening it was easy to hold the eyepiece firmly enough that it did not slip when the zoom level was changed. I did not notice any change in the resistance through a session, nor any over the three weeks since I’ve been using it in anger. As has been noted in other reviews, the nosepiece is rather long, and would have impacted on the prism in the Tak diagonal. I installed a single parfocal ring to prevent this; it also has the effect of moving the zoom ring away from the diagonal, allowing easier access with gloved fingers. Other reviewers have recommended the parfocal ring to allow both hands to be used, one holding the ring while the other operates the zoom. I did not find this to be necessary, but it is possible. The rubber eyecap is neither too sloppy when extended, nor too difficult to fold back. The eye lens is recessed only by a small amount. It was noticeable that there was only just enough inward travel on the Newtonian to achieve focus, although this would have been less pronounced without the parfocal ring and the helical focuser used in the scope. Observations: Stray Light Control The main use of this eyepiece for me will be for higher magnification viewing of planets, the moon and tight multiple stars, and also possibly planetary nebulae and globular clusters. For planets and brighter/tighter double stars in particular, stray light (scatter/ghosting) will be detrimental. A word or two about “ghosting”. This term seems to be used by different people to refer to differing optical defects. For the avoidance of doubt, the usage in the descriptions below means a phenomenon where – almost always when a very bright object is being viewed – there is a near-uniform disc superimposed on the image, ranging in brightness from barely perceptible to quite detrimental, and of a size that is variable, but may fill the entire field (and then may be detected by an overall reduction in contrast). I was going to mock up a simulation, then I found this one in CN: [EDIT: to be clear, the artefact above that I am identifying as ghosting is the circular area with a reasonably clear edge, which is not concentric with the planet. The image also shows scatter, which shows here as a larger, more diffuse area, with no obvious edge. In my observations, it was not always true that the scatter area was larger than the ghosting, if both were present, but the appearance of both was like those in this mock up] If the eye is moved in one direction, the artefact moves in the opposite direction. Since the cause is unwanted reflections from surfaces that may include the observer’s own eye, the effect can also be a little ephemeral. The most relevant observations for assessing stray light were the planets and brighter double stars, though tighter faint doubles and the moon were also useful. I suspect that individual observations to assess stray light were sometimes affected by meteorological factors, which is why I wanted to perform a number over different evenings. Solar System Saturn had become inaccessible from the observing site since Christmas. Jupiter was observed on three occasions, though it was not well placed, quite low down and above rooftops. On two of the three, the conditions were so poor that the views were worthless, in any eyepiece, but the other observation (with the Mak 127) was in decent (Antoniadi II) seeing. At 8mm (x188), the Svbony showed a strong NEB and SEB, and two fainter belts closer to the poles. The NEB showed some fine detail to its northern edge. The Galilean moons were tight, and each had a sharp diffraction ring. Ganymede showed a slightly creamy colour, when compared with the others. Some ghosting was seen, though not so much that it ruined the scene. The view in the 8mm BST was very similar. Both eyepieces showed a little more scatter around the Jovian disc than the Morpheus 9mm, though the background sky was not as dark in the Morpheus. Mars was much better placed with respect to altitude during the review period. With the Mak 127 in good (Antoniadi II) seeing across three sessions, the Svbony consistently showed a distinct North polar cap and obvious, but less clear, darker markings. The edge of the disc was sharp through 6mm>5mm>4mm (x250 > x375), though scatter increased and so did ghosting. However, at 6mm it showed better detail than the Morpheus 6.5mm and ES 6.7mm, although the Morpheus showed a little less scatter, which improved the contrast with the adjacent sky. At 4mm, the Svbony had more ghosting than the Nirvana 4mm, but less scatter and a sharper disc. At 3mm, the Svbony image revealed no new detail (unsurprising at x500) In more mediocre conditions, the Svbony at 8mm showed albedo features when the BST 8mm did not (both showed the North Polar cap). The disc edge was also sharper in the Svbony, and remained so through to 6mm, delivering pleasing views. The image in the BCO 6mm was similar, but with some ghosting. Uranus was observed once in moderate (III) seeing, showing a good disc in the Svbony at 5mm, with a nice, obvious green colour. At 4mm there was a little scatter, but less than the Nirvana 4mm, and the Nirvana image was noticeably dimmer. A Baader semi-APO filter was tried briefly for Mars and Jupiter with the Svbony and other eyepieces, on the refractor and on the Mak. It killed the violet fringe on the achromat, in all eyepieces, though it wasn’t very obvious in the first place. With the Mak, of course, there was no fringe, but the semi-APO has a Neodymium substrate that might have enhanced planetary features. There was no noticeable improvement, for any eyepiece, so most of the observations were conducted without. The moon was observed in a single session, using the 150mm Newtonian, in a waxing gibbous phase (approximately 10.4 days old). While there was significant jet stream activity overhead, the seeing was good, and the target was at an altitude of approximately 60°. No filter was used. At 8mm and 7mm, the Svbony views were very crisp. Craters and mountains near the terminator showed much detail, especially the terraces of Copernicus, and the surrounding features. The colour of the smoother areas seemed neutral and natural. The Morpheus 6.5mm showed as much detail, and of course with a wider field, though it did show some pronounced yellow/brown chromatic aberration of the exit pupil near the field stop; I’ve experienced this effect with the Morpheus only on Luna. Taking the Svbony up to 5mm (x150) did not diminish the sharpness, or the overall satisfaction of the view. At least 20 craterlets were visible in Clavius. The BST 5mm was not quite as sharp, though the eye relief was better, and the view out to the field stop was more easily taken in. When the eyecup was screwed up to avoid blacking out, the experience was more comfortable than the Svbony at this focal length. At 4mm (x188), the Svbony view was still sharp and pleasant, though showing no more detail than before. The 4mm Nirvana showed as much, but there seemed to be an obvious yellow cast across the field, and also some CAEP like the Morpheus. Maxing out the Svbony at 3mm (x250) made the lack of any extra detail visible as image softening, though it did not otherwise break down. Brighter Stars (including multiple stars) In difficult (Antoniadi IV) seeing, the Svbony at 5mm (x300) gave a slightly better view of Rigel than the BCO 10mm + x2 multiplier, though the companion was unseen with either. Castor showed little scatter in the Svbony at 7mm (x214), and the contrast with the surrounding sky was good. At 4mm, the view was very slightly crisper and brighter than in the Nirvana 4mm, though both were unavoidably unsteady. In good (II) seeing in a different session, the Svbony at 7mm and 6mm showed a lovely split of Castor with sharp diff. rings, though the contrast was affected by some pronounced ghosting. A further observation at 4mm in the refractor (x150) showed little scatter or ghosting, resulting in a sharp, contrasty view. The 4mm Nirvana gave a largely similar view, though stronger ghosting reduced the sky contrast, and the diffraction rings were not quite as crisp. Rigel’s companion was also seen in better conditions with the Svbony at 7mm in the Mak, sharp between the fourth and fifth rings. In moderate (III) seeing in the Mak, the Svbony at 6mm showed a vibrant view of Almach, though with a fair bit of scatter from the primary. The Morpheus 6.5mm was very similar, but with a little more ghosting. The ES 6.7mm image was as sharp, but had higher levels of scatter and the colours were washed out to some extent. In similar conditions, Algieba was neatly split by the Svbony at 6mm (x250). Again, the views in the Morpheus 6.5mm and ES 6.7mm were similar, but with a touch more scatter in the latter. In better (II) conditions with Almach, the Svbony at 8mm (x188) delivered a very bright, pleasant view, with well-coloured stars, neat diffraction rings and good contrast against the background sky, in spite of some scatter. The Hyperflex zoom at a similar magnification produced a near-identical view (it should really get more use than it does). At 6mm the Svbony image was still pleasing, as sharp as the BCO 6mm, but with less scatter. In poor (IV) seeing, Alnitak (2.1”) showed identically in the Svbony at 5mm and in the equivalent BCO 10mm + Altair x2 combination, the companion seen in the second diff. ring in still moments. Tighter and/or Fainter Multiple Stars Most eyepieces will handle stray light better with dimmer targets. Across the sessions there were several observations of multiple stars where magnitude was less of a challenge. In difficult seeing with the Mak, the Svbony at 5mm split 36 Andromedae (+5.5, +6.5, 1.2”) in stiller moments, as did the 5mm BST, although the latter view had the inferior contrast. At 4mm the Svbony still showed little scatter, while the 4mm Nirvana had noticeably more scatter, though also splitting the pair occasionally. In challenging seeing (IV), three components of σ Orionis (+3.8 AB, +8.8 C, +6.6 D, +6.3 E, seps. 29.9” down to 11.6”) were visible in the Svbony at 8mm. Increasing to 4mm (x375) was sufficient to show the fourth component (C) in occasional quiet moments and, while hardly comfortable, showed a little less scatter than the Nirvana. In slightly better seeing (III), the Svbony at 7mm showed the C component a little more clearly than the Morpheus 6.5mm on one occasion, but the honours were reversed on a different evening. At 5mm, the view in the Svbony was very similar to the BCO 10mm with the x2 Altair telecentric multiplier. η Orionis (+3.4, +4.9, 1.8”) showed its companion to the Svbony at 5mm, sitting in the diff. ring. The BCO 10mm + Altair x2 combination was similar, possibly a shade superior on scatter. 32 Eridani (+4.7, +5.9, 6.9”) in poor (IV) seeing showed less scatter and better contrast in the Svbony at 5mm, compared with the BCO 10mm + Altair x2, and also showed more of a colour distinction, though this was better still in the Morpheus 9mm. λ Orionis (+3.4, +5.5, 4.5”) was seen as well in the Svbony at 7mm as in the ES 6.7mm, and the diff. rings appeared crisper at 5mm (x300). HR 1902 (+5.7, +6.6, 1.2”) was just split in difficult conditions with the Svbony at 4mm (x375), an easier job than with the Nirvana 4mm, which gave more scatter. 6 Trianguli (+5.2, +6.7, 3.7”) was pleasant in the Svbony at 5mm (x300) in good (II) seeing. The BST 5mm gave noticeably more scatter. At 4mm the discs were not as tight and scatter increased, but still a touch better than the Nirvana. γ Arietis (+3.9, +4.6, 7.4”) in good (II) seeing was beautiful in the Svbony at 6mm (x250), with little scatter and two sharp diff. rings on each star. The BCO 6mm was equally sharp, but increased scatter affected the contrast with the background sky. ε Arietis (+4.6, +5.6, 1.3”) in moderate (III) seeing, was just about split in the BCO 6mm, with very little scatter. The Svbony at 6mm (x250) showed almost no scatter, and delivered a view with more contrast, brighter and crisper. The split was wider at 5mm, with similar image quality. Increasing to 4mm and 3mm resulted in more scatter and larger discs, but still not unpleasant. The same target on a poorer evening (IV) was just split in the Svbony at 6mm, but still showed very little scatter and good sky contrast. In the Morpheus 6.5mm the view was very similar. Tegmine (+5.6 AB, +6.3 C, 5.9”, and +5.3 A, +6.2 B, 1.2”) in good (II) seeing, with the Svbony at 8mm, showed a very slight yellow/blue distinction, with little scatter. At 6mm AB was resolved with no degradation of quality. The Morpheus 6.5mm was very similar, possibly having slightly tighter stars. At 4mm (x375), the Svbony effected a split of AB, with some increase in scatter. The view was considerably better than that shown by the Nirvana, where any AB split was masked by stronger scatter. Achird (+3.4, +7.5, 13.6”) in good (II) seeing with the Svbony at 5mm (x120 in the refractor) showed the faint secondary clearly, and a sharp primary with a couple of diff. rings, though there was some ghosting. The Morpheus 6.5mm was a fraction crisper, but the ghosting was stronger. In addition to the regular observations, when I observed Almach in the Mak, I moved it to just beyond the edge of the field stop. When exiting the field, the star was extinguished rapidly, and only a little light was seen to leak into the view with it placed just outside the stop, commensurate with the levels of scatter I’d seen in other observations. Contrast This has already been mentioned in several of the preceding observations. When targeting doubles, reduced scatter and/or ghosting can enhance the contrast with the background sky, an aesthetic improvement, but also useful where fainter companions are to be detected. For Mars/Jupiter/Saturn, contrast can make the difference between seeing a feature or not. In addition to the comments so far, there was one observation of a planetary nebula: NGC 2392 (Clown Face/Eskimo nebula) in the Svbony at 8mm was very obvious and extended, though no specific structure detected, with good contrast and with the central star seen with direct vision. At 6mm, brightness was reduced and averted vision needed, though this was also true of the Morpheus 6.5mm. The addition of an Astronomik UHC filter did not obviously enhance the view. Field Curvature This is a tricky one to assess. Firstly, observers can accommodate differential focus to different extents, and younger eyes can generally manage better – they may not even detect that the field is not flat. Also, FC is affected by the rest of the equipment, and the net effect is often an interplay between eyepiece and OTA. Perversely, an eyepiece with strong FC may seem excellent if used in an OTA imparting an opposite curvature. In mitigation of the first point, my eyes are not the most youthful, and I don’t think much will be hidden on that account. On the second point, I have used three OTAs of different designs and focal lengths, and the Mak, at least, ought to be showing the picture reasonably accurately. As I will be using the zoom with a driven mount, and mostly on compact targets, FC isn’t my top concern, but I did a little investigation. In the Mak 127, Almach was allowed to drift to the edge and no defocusing was observed. In the F/5 Newtonian, 36 Andromedae was focused in the centre of the field with the Svbony at 4mm, and gradually moved to the edge. Some refocusing was required from about 75% from the centre, but still gave a decent image. Beyond around 85%, the stars developed aberrations that could not be refocused. Given the results in the Mak, I ascribe the reflector observations to FC and coma in the OTA, rather than the eyepiece. Barlowing The zoom is unlikely to be used with a Barlow, but one test was conducted with a 2x Altair telecentric multiplier at 8mm, comparing the view with the zoom at a native 4mm. There was no discernible difference. Blacking out I have previously been pulled up on the distinction between this effect and “kidney beaning”, the latter being apparently very rare in the modern eyepiece. Blacking out, then, is restricted to the phenomenon where there is a comparatively small range of distances between the eye and eye lens that show the image properly, so that correct positioning of the eye becomes critical. This can be helped by a suitable eyecup, comfortable seating, etc. In none of the observations so far have I noticed this effect with the Svbony, though I did see it a couple of times with the BST 5mm and Morpheus 6.5mm. Eye relief This was the most obvious drawback of the Svbony. At 6mm – 8mm it was adequate, but hardly comfortable. At shorter lengths, folding back the eyepiece was essential to access the full field, and then care was needed not to touch the eye lens (one session did result in a deposit from eyelashes). I don’t need to wear eye glasses to observe, but I got the impression that it would be difficult or impossible. Parfocality As others have reported, the Svbony is not parfocal. Whether or not “nearly parfocal” is a meaningful attribute is moot (and very much so on CN). I found that the slightest touch of refocusing was needed on the longer focal lengths, and a little more at the short end. Other eyes may find that less is required. Conclusions In modest scopes, for most of the time, the Svbony held its own against fixed eyepieces ranging from the decent budget end to upper-mid-price. For its most likely use cases, it controlled stray light acceptably well and delivered sharp, engaging views with decent contrast. Over the review period, on average, it outperformed the Nirvana 4mm, BCO 6mm, and BST Starguiders. It probably won and lost to the ES 6.7mm in equal measure, and was outperformed clearly only by the Morpheus. It does not, of course, have a field as wide as some of the comparison fixed eyepieces, so the experience is inevitably diminished to that extent. The main disadvantage is its tight eye relief, particularly at the shorter end, which makes it less comfortable to use than some of the fixed eyepieces. The Svbony zoom is a capable eyepiece and, at the price, should make a mark. With its 3mm-8mm range and small form factor, it could usefully be paired in a travel case with a longer zoom such as the Hyperflex 7.2mm-21.5mm. I’m happy to have taken a chance on it.

I think he has copyrighted it, so no-one else is allowed do it. This may be the most "definitive" post, but I've seen several others on specific topics.

That's interesting, Louis. Scatter was the defect I was most interested in with mine, and I was actually quite pleased (there's that "quite" word again, sorry). It lost out narrowly against a Morpheus 6.5mm, for example, but I'd expect that. It was noticeably better than my Nirvana 4mm, though. I did find it a bit difficult sometimes to exclude the effects of possible high cloud, too thin to see with the naked eye, but enough to increase the scattering. On the image darkness, again I was happy overall. The Svbony views in good conditions seemed quite vibrant to me. I have been meaning to post my review, but it's turned into a bit of a marathon. I should finish this week.

Mine too. It does very well for the price, but the action is a bit too stiff.

Just before Christmas, our low-pressure sodium street lights were replaced with LEDs (and a few nearby roads). Although they weren't as bright as some others I've seen, it did seem that there was more light leaking into my back garden than before. I've been waiting for a clear might with a new moon to measure the zenith brightness, and I now have. I got 20.75, when previously I've had it up to 21.00. I don't know whether a few dozen street lights can make that much difference. I'll keep taking measurements.

This one must be in with a shout, even if it is one of the ugliest scopes ever constructed

Question: does this feature have a name? I saw this tonight and it was very pleasant and sharp, about half way between Copernicus and the terminator. It looks like a ring of little peaks, presumably the remains of a mountain wall surrounding a crater? It looked much more obvious in the scope than it does on the screen shot above (taken from my moon map app). Neither the app nor my paper atlas have a name for it.

There was some lovely detail on the moon earlier, up as far as x375 in a 6". Surprising, as the jet stream is very active.

Well, I finally saw the comet. I decided a bit late to go out, with a forecast of cloud moving in, so I went with the Newt instead of waiting for the Mak to cool. I was mainly wanting to look at the moon, to compare the Svbony zoom against fixed EPs. So I didn't even bother to align properly, and with the thin cloud already forming, and the moon very bright overhead, I didn't think I'd have a chance at the comet. But I did a goto, and there it was, sharp nucleus and extended disc. A very productive hour.

Yes, a "pointing accuracy enhancement". It doesn't contribute to the overall alignment, but is supposed to improve the local accuracy. Yes, you can align within SkySafari, and it will create an offset between it and SynScan, provided the discrepancy isn't too large.

Hello, welcome to SGL. You might want to have a look at this current post, which is asking for similar advice and has already had a few responses. The Skymax has a 1500mm focal length, so a 10mm eyepiece will give you x150, which will be good for planets in reasonable observing conditions. In very good conditions, you might want to go a little higher for Saturn and Mars, but I would try it out with the stock eyepieces first before you start thinking about extras (when you do, have a look at this guide). You don't need to spend much on a moon filter, but a variable polarizing model is useful as it lets you vary the brightness: https://www.firstlightoptics.com/moon-neutral-density-filters/astro-essentials-variable-polarising-moon-filter.html

I have found the 16mm Nirvana to be very pleasant, in all my scopes. I still can't believe it's under £100 new. I have one ES 82 degree, the 6.7mm. It's very sharp and controls light well, though I find it gives slightly dimmer images than some of my others. You should probably steer clear of Hyperions at F/5, but I've found the Morpheuses to be excellent. They are "only" around 76 degrees, but the experience is more immersive than I get from either the Nirvanas or ES. I've picked up four of them now. Unfortunately they're £230 new, but you might get one second hand for your target price, if you're lucky and/or quick-fingered. Three of my four were. Only you can decide whether or not it's worth the spend to go from 60 to 70+ If you can get a look through someone else's at a club night before buying, it might help,

I understand that you want to make the best possible decision on your first buy. I spent ages analysing all the options before I bought mine. But there's only so far that you can go without diving in somewhere. There will always be different opinions, even on apparently objective criteria, and your view may turn out to be different, once you've tried for yourself. In my case, I started with a Star Discovery 150i, which you mention, and I've been very happy with it. I learned a bit about the sky, and observing, and then I bought another OTA (optical tube assembly - i.e. the scope minus a mount or tripod) - the Skymax 127. I can use that on the same mount, and it has given me more options. Then I got a 102mm refractor, and I use that on the same mount too. I think that whichever you buy out of the three that you've mentioned will give you pleasure, allow you to see a good range of objects, and help you to learn. When you (or your wallet) is ready to buy again, you will have a better idea where you want to go next.

Was there a reason that you were looking for a tripod-mounted scope? The Dobsonians are meant to sit on the floor and work well like that. One common reason for preferring a tripod is if you have an obstructed horizon, then the tripod can help raise the viewing point. As @NGC 1502 says, the Skymax and the Dob are both good choices for a first scope, in their different ways. Yes, the Skymax has a narrower view because of its longer focal length - the maximum you can get (unless you modify it) is a little over 1 degree. So there are a few objects that you wouldn't be able to fit in entirely, but far more that will fit. You can simulate what you might see (in terms of the fit, but not the quality of the image) at this site: https://astronomy.tools/calculators/field_of_view/?fov[]=70|2245|||1||&messier=45 (I've set it up here for the Pleiades, viewed in the Skymax and an eyepiece that gives it a maximum field of view). An 8" Dob will gather considerably more light than the 127, so you should be able to see fainter objects and details. But you will need to get used to "nudging" (unless you get one with motors, which will be considerably more money). The Mak on the Az-Gti, if set up correctly, will track objects and allow easier extended viewing. This can be useful if you are sharing observing with family or others who are inexperienced. And you have the go-to, which can be very useful if you don't know the sky (yet). The wider field of the Dob makes it easier to get an object into view than the Mak, but in either case I would recommend you use a combination of a decent optical finder and a red dot/ Telrad /Quikfinder, which make it as easy in the Mak as the Dob. Depending on the scope you buy, it will come with either a red dot or optical finder. If there is only one finder shoe, then put an optical finder in that and get the other one as a stick-on. You may also find an advantage in the Mak with eyepieces. A scope with a faster focal ratio (typically F4.5 to F6 for reflectors like the Dob) will be less forgiving of some eyepieces. In particular, if you want to get into wider field models (say, 70 degrees plus), then you might have to pay more for a better design, to achieve the same quality of image that you could with a lesser model, when used in the Mak. The Dob is more of an all-rounder in terms of targets, while the Mak can be better for higher magnifications, typically for planets, tighter double stars, globular clusters and planetary nebulae. I Have a Skymax 127 and a fast-ish reflector. I enjoy them both, but have found myself gravitating more often to the Mak.

Welcome to the forum, and no need for apologies, this one has exercised some very good minds. It's called "Olbers' Paradox": https://en.wikipedia.org/wiki/Olbers'_paradox

I've been testing it with a Skymax 127. I will also be using it with a 150mm F/5 Newt.

Well the low cloud did clear, but transparency was a bit variable, the seeing was quite good, same as last night. In the end, it was the cold that drove me in. This was my third night in a row, and I think it's gotten into my bones. I had a good look at Mars for half an hour, which was showing better than yesterday for me. And a few doubles, and the Eskimo Nebula, but my goto is having a hissy fit at the moment, so it's back to the red dot and RACI. My main aim this week was to compare my recent Svbony 3-8mm zoom with the rest of the stable. I'll get around to writing it up when the weather changes.

I just managed to get aligned here, looked up - sky full of clouds. But the forecasts are still optimistic.

In this cold spell we have had evenings limited by some high cloud, but I didn't see any tonight. The seeing started off quite poor, but improved some after a while. Jupiter was very poor, low above the rooftops, couldn't make anything out. Mars was quite decent high up, even though it's getting smaller, the North polar cap is still obvious and I caught some albedo features. Uranus was, well, Uranus. Like @bosun21, I took a Morpheus 17.5mm to M38, and also to M35,36,37. And a few doubles to try out the debutant Morpheus 6.5mm: Alrischa, epsilon Arietis, Almach, Algieba, HD 36203. Finished with M42 at different magnifications. Over 4 hours outside, and everything was covered in frost when I turned on the headtorch.

Even if it's not a dewey evening, you may find some advantage from the dew shield in controlling stray light entering the tube, bouncing around and reducing the image contrast. It depends on how much local light pollution you have, its direction, how well the inside of your tube is blackened , etc. I always fit mine, dew or not.