Ben the Ignorant

You might scratch the lens.

It's a very common question from beginners who probably don't know that many things can be observed with binoculars on any night. Too many to make a practical list in a post. We've been advising beginners to start with binocs instead of a telescope, but I'm starting to think a sky atlas should come first. Sky & Telescope's Pocket Sky Atlas is ideal, not too big, not overwhelming with too many entries, costs only 20€, and complete enough to be used at the telescope for several years after the binocular initiation. https://www.teleskop-express.de/shop/product_info.php/language/en/info/p193_Kompakte-Version-des-Sky-Atlas-2000---bis-7-6mag.html

Nope. 600£ is 675€ for an alt-az long-tube smallish achromatic when plenty of excellent f/7 semi-apos can be bought for the same amount of money. Take TS' 500€ tube, add a 290€ alt-az, that's 690€. Plus, the semi-apo has a 2" focuser for wider fields, and an f/7 ratio for wider wider fields. Unless one is dead-focused on the brandname or its endorsement and ignores practical things, the long narrow-field achromat is not interesting. There is always an affordable semi-apo that costs nearly the same as a nostalgic's achromat. Not even sure this mount allows pointing at 90° elevation from what I see in the picture, by the way. I just bought a Ronchi grating and tested my TS 80mm triplet (646€ in 2012) and my Astro-Professional 80mm semi-apo doublet (180€ on a liquidation sale). Both produce lines that are just as straight, so overall aberrations are controlled the same way. But the "cheap" semi-apo's lines have a somewhat sharper edge. Truer , more saturated colors in the triplet but a little bit more contrast and sharpness in the doublet, at the expense of a minuscule violet fringing, of course. A violet-absorbing diagonal reduces that so it can be ignored. Residual aberrations in the lenses compound each other so an air-spaced triplet will have more than an air-spaced doublet assuming the same polishing quality. Given how chinese semi-apos can excel I see no reasons except irrational reasons to pay high prices for achromats.

120€ feels right so 120€ it will be. Thanks for the input.

75% would be too much for a 7-years old achromatic but 50% is 115€ and I was thinking around 120€. The reasoning was based on what I read in a french-speaking forum, they usually say 60% for used stuff. That would be 138€ but shipping will cost about a dozen euros so 125€ would be fair. But the adapter is not there so 120€ feels okay. The thing is not scarse or in high demand (that I know of, am I right or misinformed?). So a little over 50% seems right. Everybody agrees? I still have a little doubt arising from the very good condition of the case and binoc.

Now that I have a low-dispersion 10x50 I'm selling my 10x50 achro locally (and on this forum if I find no takers locally). It's the well-known armored binoc that sells under various brands, Orion Resolux, Oberwerk Ultra, etc, TS Marine in this case. It's complete with case, straps, cleaning rag, front and rear caps and proof of purchase, nothing is damaged, only the tripod adapter is absent because it serves as a stop to limit the motion of the tube in a dob I built. The rubber knob proved ideal for this. Front lenses have no scratches, no dirt, no fungus or whatnot. Same for rear lenses. Eyecups sometimes have a ring of tiny cracks when they are folded down often but I don't wear glasses so they are intact. It's been cleaned and kept in storage since I decided to sell it, overall condition is very good, especially the case which is exactly like brand new. It looks greyish-black on the pictures because of unnatural lighting but it's really dark foliage green. Not sure how much to ask so I'm polling collective knowledge here; I paid 230€ for it in 2012, how much would be a fair price?

vlaiv answered exactly what I would have answered. Since your scope will be f/5 or f/6 you will need a widefield 2-inch eyepiece in the 20mm to 30mm range. To enjoy the largest view your future scope will provide its specs have to be around 30mm for a 68°, 25mm for an 82°, or 20mm for a 100° eyepiece. Always start your eyepiece set with a low power one that shows the largest piece of sky the scope can give.

That's because all telescopes are good but for most people, the most versatile, largest for the cost, and easiest one to use is the dobsonian. Maybe you already know, but a larger diameter increases resolution and brightness so a big scope is a big help to see better. But, you might not be like most people, so your personal best beginner scope could be another type. By all means find an astro club near you and try as many telescopes as you are allowed to, I don't know stargazers who don't let newbies try their scope and discuss it. Then come back here with the remaining questions. However, if you can't go to a star party, don't fear, you can't go wrong with any largish, simple reflector or refractor in the usual beginner range. A standard 10x50 bino is a great starter, too, and you'll keep it forever. After a lifetime of stargazing with scopes up to 12" I just bought myself a "small" top-notch 10x50 last month, and I've been in a binocular skygazing frenzy ever since.

NGC 1647 and 1746 in Taurus, sparse but not drowned in field stars, not faint overall and not too faint in their individual stars.

All I could find was this: http://r2.astro-foren.com/index.php/de/10-beitraege/02-ed-optiken-halb-apos-und-frauenhofer-systeme/677-b045-02-how-to-collimate-a-apm-100-bino I've never done that job but I assume an extremely distant lamp can act as an artificial star. The parallax with a target several kilometers away has to be negligible.

You can't keep a doubt about your scope's collimation. Aim it at a 2nd or 3rd mag star at very high magnification and defocus it just a little so you see one central dot and two or three rings. Defocus on each side of sharpest focus, the pattern on one side might be clearer. If the rings and dot are perfectly concentric collimation is good. At f/5 miscollimation does not forgive so be sure of that before anything else.

It's excellent, and I had not noticed at first but the price cut is extended to most APM binoculars because of the AME Astro Fair.

Oberwerk and Tecnosky make interesting giant binoculars and binoscopes, maybe you can find one that suits your budget.

A really badly derotated and/or decentered objective lens could cause that. I bought (and still have) a cheapo 80mm achro doublet that was so derotated and decentered the image had an horrible blur to it. Rotation marks were present on the lenses' edge so that was quickly solved but the centering problem required adding radial screws to the cell. Not something you should do on a classier scope that's still under warranty, though.

While looking at APM's binoculars for other reasons I stumbled upon this fresh offer (wasn't there yesterday): https://www.apm-telescopes.de/en/apm-highlights/binoculars/binoculars-50mm/apm-ed-apo-12-x-50-magnesium-series-binoculars.html?info=13672 I just reviewed the 10x50 and it's splendid. Bought it more than two weeks ago but the first moonwatch was only two nights ago because of the usual reasons; compared to the classic armored 10x50 achro, center was sharper, more contrasty, brighter and whiter with almost non-existent flaring. Edge of the achro made a slightly elongated Moon with obvious green and purple fringes, and quite a noticeable loss of resolution; two ghost images of the full Moon when it's a bit off-center. Edge of apo keeps the Moon's shape, almost no loss of sharpness, and fringing is much, much narrower and that much fainter.

A 16x70 APM Magnesium apo if I can sort out doubts about its real weight. APM's site says 2124g, Teleskop Service's page says 1926g, and my 16 years-old Fujinon weighs 2100g with strap and caps on, the real mass that hangs at my neck. A magnesium alloy bino should be less massive than the old Fuji because of density and the need to compete so 1926g should be the real figure, hopefully.

The bag had another defect, some piece of fabric at the rear left this gap with the lining showing inside, not pretty and liable to be torn if something catches it. Someone at the bag factory got absent-minded for a moment. The needle being as cavemanish a tool as the knife and the hammer, that kind of thing can be adjusted by anybody, so not really a problem. Stitched from the inside of the bag and that's all. Not something you sent a complain about to the maker or the seller, not a motive for a return, and the job does not void the warranty; I'm just showing it so the review is complete. The essentials of the binocular itself have no issues.

Currently mag 18 and brightening, 1° north of famous colorful double star Iota Cassiopeia, heading southeast. https://www.skyandtelescope.com/astronomy-news/possible-interstellar-comet-headed-our-way/

Well, when reading a review I want to feel like I'm there and examining the thing for myself so that's how the APM's review was done. So, lots of photos indeed, I made them over three or four days, couldn't be done in one take. And yes, Porro's are great, large diameters like 70mm are possible only with Porro's, and making a straight binocular with the same image quality takes a big price increase because roof prisms have complicated shapes, and they need phase coatings and dielectric coatings. Roof binoculars are narrow and I don't feel comfy holding them, the grip and elbow position with a wide Porro seem more natural to me. The 8x40 in the review has the frame of 50mm binoculars so the grip is the same. They look funny with their shorty barrels on a wide frame but they feel right.

Down to f/7.

The review is online.

I've had my APM 10x50 apo for a dozen days so I feel ready to compare it to the very popular and well-known armored Teleskop Service 10x50 "Marine" achro that's been selling under various brands for many years, the shape is always the same, colors can change but the instrument is very recognizable. Let the show-and-tell begin. The APM comes in a white box that's elegant and sturdy enough to be kept if you have the storage room. Bag, straps and cleaning rag are standard. The bag is padded and well-made but it has a weird pocket more than 20cm deep with very narrow openings; if you don't have the 8-inch long fingernails of a sorcerer you won't recover what's inside so I stitched it shut with these two curved lines of thread. Another minor issue was a bunch of defective teeth: But fortunately it has two sliders so a narrow strip of nylon blocking the sliders before they hit the defective spot solved the problem. It doesn't look out of place, the good looks of the bag are not lessened. But this is a comparo so see how the APM's strap has better stitching: The strap itself is the same neoprene thing. It's washable and proved flawless after seven years. Strangely, the stated weight of binoculars is not the same in all sites so here is data that can't be disputed. The APM does not come with the usual tripod attachment, it has its own, tough metal thing. It feels like a piece of armament or an engine part, tightly machined and anodized well. Tha APM adapter is screwed around the oversize bolt: But it also attaches to standard 1/4-20 accessories at the center, nice versatility. But how does it handle, you wonder? That is a factor of weight, size and shape so let's see these. The waist of the TS is slightly over 62mm across. The APM is only 1mm narrower but the difference can be felt. 65mm at the rear, where the index finger rests. 4mm more, that feels bulky in comparison. The ends of the barrels are very nearly the same. So, how do they feel overall? Because the TS barrels have more belly and those ribs, but the APM has slimmer and straighter barrels plus a lighter weight, it feels definitely sleeker in the hands. Note that the APM is longer by a few millimeters because its eyepieces hold seven lenses when the achromatic is content with only five. It startled me when I read the description but thinking of it, seven lenses to provide a wide, FLAT, 65° field (same as the TS) when the objectives deliver a very steep f/4 light cone seems like a reasonable number of lenses. The brand-new focusers of the APM are more fluid than the TS focusers after seven years of use, by the way, but completely free of sloppiness. Just as firm as they should. Now a little warning illustrated by the two following pics of the front coatings. TS is on top, and seems to perform poorly but only a small change of angle, and… ...the APM still wins but the coatings now look more like what the eye sees. Keep in mind that my phone camera doesn't have much dynamic range and resolution, so the visual differences shown here and in the following pictures are as close as possible to reality, but not perfectly faithful. The eye sees so much finer than this. TS prism coatings. APM prism coatings, same "dishsoap" green color but the APM is somewhat darker. It equalled or outperfomed the achro in this and all other respects, nice finding for optics that cost double the price. Note that prism housings look identical so shock resistance should be the same. Seven years of sometimes bumpy car trips never decollimated the TS so I can expect the same from my APM. One needs to be reassured about the new expensive things one buys. APM boasts a great resistance to water but doesn't speak of shock resistance in their leaflet, the above pics tell me what was missing. A feature where they exactly equal each other is the blackening and the ribs inside the barrels, they are precisely the same component. The "junk" around the achromatic's exit pupil, straight-through. The "junk" around the APM's exit pupil, somewhat dimmer, the prisms seem to have gotten a better blackening. Same test but for lateral blackening of the eyepiece lenses and housing: APM above. TS here. Patterns are not the same but the eye sees a bit less reflexions overall in the APM, not obvious in the photos. I thought my achro had big eye lenses at 25mm... (the camera's perspective makes it seem a bit less, phone cameras and their super short focal lengths are very limiting) Uh, Big Bad Wolf, what big eyes you have! 27mm. If you saw a closeup of the rear of the APM without context you might believe it is the front end of a small binocular! I ditched the metal calipers and switched to a decrepit but soft plastic ruler because bringing metal close to lenses is out of the question. Uh, one mistake, the TS does win in one respect of that comparo, its objective caps are captive. But since I value the new (expensive!) APM more I put the capive caps on the APM. However it takes an O-ring to keep the "captive" in place, and that hides the elegant indigo ring in the groove. The O-ring nicely locks itself in that groove, so the arrangement does not look too much out of place but I hope to find aftermarket caps that don't hide that touch of color. Sometimes I observe through my window at the second-and-a-half floor (yes, there is such a thing if the stairs are spiralling and the architect wants to show off, or maybe he was just crazy), so losable caps mean I have to make an emergency dash for the street before cars run over the caps. Binocular makers, stop making losable caps! How about coatings at the other side, now? A laser helps. TS has slightly brighter reflections throughout. I extended that comparo to the Fujinon 16x70 and a TS Wildlife 8x40 achro, the APM eyepieces had the softest reflections of all. They really took care of every detail. How about lens edge blackening at the front, where stray light is more likely to enter the system? TS has no arc. It's another feature where it equals the apo and proves itself as a solid performer. Fujinon has a very faint arc, not much to worry about. In these tests the laser was always placed at the spot where it caused the brightest possible arc. APM is super dark, very satisfying thing to see after craving and saving for it so long. Just so the issue is clear this is what a bad arc looks like. That's the small 8x40 achro, despite the lack of edge blackening contrast and brightness are quite good so don't be dismayed if you see this in your binocs, it's only one area of performance among many. Now a harsh unrealistic test but these make things more evident when they are too subtle to photograph. A sodium streetlight around 35m distant. First the APM: Now the achromat: What's there to see? First, the apo's main halo is smaller. Visually the apo's halo is also smaller, dimmer and less spiky. Second, secondary halos are dimmer are broader in the photo, same visually. In the achro shot note the several very small but very bright flares above the lamp. They were the same visually. Coatings are not perfect and they do cause flares but flares have to be as large as possible because spreading their light makes them less visible. It reduces their surface brightness in astro parlance. Optical designers have to optimize glass types, lens curvatures for image quality, lens spacing, cost, etc, but they also have to choose curvatures so the reflections end up as far from the focal plane as possible so these flares are too dim to be seen. It must be a very complex art, and once again I'm glad the folks at APM took that task seriously. I did a half-dozen of each achro and apo shots but for some reason the achro pics were always much darker than the apo ones. Visually the difference was way smaller than what the pics suggest, but one can't deny the finer optics show the tiles and the roof's zinc edge with better clarity. I hoped to present how the apo and the achro show bright light sources and their chromatism but sadly it became a show of the camera's limitations. A distant factory's mercury lamp, center of the achro's field. Same lamp at the edge. Same lamp at the other edge. My eyes pick up a bloated lamp with less detail and a violet flare oriented toward the center of the field, but the camera sees all overexposed lamps the same, and reveals only yellow-green chromatism where the eye sees both the violet and yellow-green fringes. APO's center shot. Looks more bloated than the achro because the camera is not consistent. For various reasons I had to hold the NexYZ adapter, binocular and phone assembly by hand, resting it on the window for a little more stability but as astro imagers know, less than perfect stability is guaranteed failure. I had hoped to do this test with Sirius because it's a real point source but it's much fainter than the lamp so… Apo's edge shot of the lamp might look a bit tighter and less fringed than achro's but not conclusive. I had hoped to remove from this review as much subjective judgement as can be done but it seems personal impressions have to be here anyway. So, visually the apo's starfields have a blacker background, stars are much, much tighter near the edge. A faint star cluster in the middle of the achro's field is a cluster but it becomes a nebula near the field stop. It remains a cluster all the way in the apo. M35 (from a city) showed 3 to 4 stars in the achro but 4 to 5 stars in the apo. Galaxy M81 goes from just detectable in the achro to visible in the apo. Andromeda is only a core with a hint of a disk in the achro; it is a brighter core with a hint of the pseudo stellar core in the apo, and the vague disk becomes a flattened flying saucer in the apo. M32 is easier to see. Daytime trees show brighter leaves in more nuances of color when looking at tough shady areas. Contrast and sharpness are superior at first sight in all conditions, sunlight, nighttime, overcast days, haze, dusk, hard bright sky behind a dark electric pier. No chromatism at all in the center; away from center only a faint trace of hairline colored fringes in tough conditions, goes unnoticed unless one looks maniacally for it. Super minimal crescent distortion, noticeable only when panning left and right back and forth very fast, nearly nothing in normal panning, and less and less with practice. Cortex needs to get used to new things, even very good ones. TS achro has more of that negative distortion and panning funkiness Now eye relief. Here subjective opinions or questionable figures go away, fortunately. Just look. Projecting the exit pupil on a white thing parallel to the lens makes a blurry spot… ...that becomes sharp at the true eye relief distance, about 5mm further than the back of the eyecup for the TS 10x50. The little 8x40 does better, about one and a half millimeter more. Note the two O-rings placed under the twist-up eyecup to keep it at the right distance for me. These eyecups are narrower so they enter deeper in the eye socket, large eyecups kinda reduce eye relief. The barrels and eyecups in the APM and TS have the exact same diameter. The 16x70 has the tightest eye relief of all, looks like four millimeter. I was so used to this and the 10x50 TS that at first I held my APM too close, causing some aberration and making blackout happen too easily when rolling the eyes to look at things near the field stop. For a while I thought of buying the 12x50's eyecups (if possible!) since each of APM's 7x50, 10x50 and 12x50 ED's have various eyecup lengths, each taylored to the eyepiece's relief. But that proved unnecessary once I understood the issue. My new 10x50 has the longest eye relief of all, yay! Looks like 8mm. Lastly, a scatter test. Simply put all the suspects under a bright ceiling or sky. The ceiling in that room is white so unmerciful test. Light enters and then exits the optics, scattering at each possible place, on the coatings, on the housings and inside the glass. The 8x40 performs according to its price and that's okay. The 10x50 achro does better, still in line with its price and reputation. The Fuji does somewhat better than the APM and it'd better outperform it in at least one respect, since it costed twice as much and its reputation has to be justified. By the way, it has an edge sharpness in between that of the 10x50 achro and that of the 10x50 apo, nothing to blame, it was bought sixteen years ago but the optical design is several years older, and it's an achromat. The APM's coatings are on average a dark olivine tint that looks almost grey-black because they are so efficient. You wouldn't waste your money buying one; except for the losable caps it has only good things about it. Since aftermarket caps can probably be found, or APM will upgrade them, it might have no defects at all.

The weight is not what makes the binoculars shake, the body shakes all the time to maintain its balance, and the binocs magnify the effect, so any optics with the same magnification will show the same motion, no matter how lightweight. The solution is to make them more stable, so you could also use larger binocs as an extra benefit; or resort to electronically stabilized binocs but they are expensive.

The sky should be grey. The collective glow of stars (and to a lesser extent, nebulas and galaxies) that are too faint to be seen individually turns the black of space into a dark grey. It's like seeing an open cluster to the naked eye as a greyish smudge that is resolved into stars by an instrument. You could say the whole sky is a star cluster so the whole sky is also a grey smudge. To have a truly black sky would mean it has nothing beyond the stars you see with the naked eye, so nothing more to see with telescopes.

Jean Texereau's How to Make a Telescope, old-school indeed, and still unmatched.