Ben the Ignorant

Izar is famous for being pretty and being a good test of the telescope, the observer and the sky conditions. It has been split by oldtimers with apertures around 2 inches only but even my 5-inch Celestron has a tough time with it when the air is not super steady. My 80mm does not require such rare air conditions, though.

Since you like to see planets you need to observe when the air is calmer, so check meteoblue.com; you can customize the forecast for your city. On the left side of the page click on "Special", a menu will open with an "Astronomical seeing" option. Click it for a forecast of the air turbulence, I've found the main forecast and the seeing prediction are reliable, and my friends who do imaging rely on it, too. Remembering Jupiter is around 40" across, when turbulence changes a star point into a 3" disk you know what to expect. Other weather services exist but meteoblue is the one I know, and it's good.

Looks like you're simply seeing air turbulence, it's always there to a changing degree (it's a weather pattern so it changes).

It's not just a thing of the past, this 72ED was accidentally stopped down to 69mm by a mispositioned baffled: http://www.astrotest.it/test-reports/apochromats/skywatcher-evostar-72ed-ota/ Very good scope in most of its features but the single baffle is not enough (how much would a couple more plastic or aluminum rings cost?), and the main tube is not blackened properly (how much does a little black paint cost?). My 80 semi-apo and 80 full-apo both lacked baffles, I made some extra ones. By the way, this thread is read by many nostalgics and collectors who might want to see that japanese GOTO 80/1200, sold as tube and finder only: http://www.dark-star.it/vendesi-e-cercasi/

Good to know.

If low-dispersion glass had been available since the beginning achromats would not exist, all refractors would be apos and this discussion would not be taking place, they are the byproduct of limited glass technology. There is no reason except nostalgia for long heavy cumbersome achromats today, and it is a valid reason for those who value it above convenience, but convenience is the mother of all inventions and changes in the way of life, so... I bought an unexpensive 80mm f/7.5 achro several years ago, as a birthday gift for a friend, for his whole family to be more precise, because they own a rural home in southern Italy where they spend two months each year. The sky is super dark, M33 is visible to the unaided eyes; their simple achro with a low-power eyepiece and an AZ-3 mount is a great sky sweeper for these occasional stargazers. At the same time I bought the same achro for myself to have a travel scope that I'm not afraid to tote around, 115€, so no fear. But a couple years later I unearthed a new 80 f/7 semi-apo sold for one third of the regular price because the lens was dirty and the store staff didn't want to clean it. 115€ for an achro but 184€ for an apo, so why keep the achro? Funny that this thread arises now, since a couple of days I was just thinking of giving my achro to the same family because their year-long home is right at the edge of the city, so less light pollution, and their main window/patio happens to face South. The achro has not been used for at least a year. it made me realize I see no point in keeping it any more. Of course it would be a different story if the scope was huge and expensive.

My TS 80 triplet arrived in a Geoptik box.

The Celestron 100 ED was a bargain almost too god to be true. It's been discontinued for years but it was an f/9, aspherical apo doublet, probably a clone of the Sky-Watcher f/9 doublet but maybe not. Anyway, it got this excellent review: http://www.telescopedoctor.com/main.asp?cod=test/rifrattori/celestron-Omni102ED If you don't read italian, spherical was extremely reduced, no fringing in focus, only a little color spread outside of focus, no light scatter, extreme sharpness, 300x and no image breakdown. The best part was it retailed for not much over 700€. 746€ in a certain shop when I hadn't saved up, and then only 716€ when I had, mount and tripod included. But it was labeled as "available in may" when I had decided to buy in february of that year. So I waited and waited and waited, checking regularly the status of the thing. When it finally showed up as "in stock", I sent an email asking to confirm it was actually so, cause I knew actual stock is not always updated immediately. Yes, it's available for order, and you'll soon enjoy that fine instrument, was the answer. An hour or two later I'm back at the shop's site to place the order but it's labeled as unavailable. Imagine how shocked I was after a three months wait! One more email, they answered their provider has suddenly discontinued the thing and not warned them. So it had never been in stock anywhere, but only probalby available, and the probability turned out Schrödinger's cat was dead. Or it was materially present somewhere and was sold to someone else, which would not be better. Today you'd pay more than 716€ for the Sky-Watcher tube alone but back then the price inluded a CG-4 mount, Celestron's supposedly upgraded version of Sky-Watcher's EQ-3 mount. Manual controls, no dual-speed focuser but still a wonderful bargain. In theory. That was my worst disappointment ever in astro shopping. I must say I avoided that shop for a long time but ordered from them on a few occasions when I felt more at peace with them. As some sort of twist of fate they got me an 80mm semi-apo at 1/3 of the regular price because it had fungus on the lens but it was never used, happened in a wharehouse, the mounting rail and the focuser drawtube were pristine, never been used for real. So, be prepared to an occasional letdown, but don't boycott any shop, they might have what you need later and it might be an even better bargain. Lastly, since the mount alone costed around 300€ at that time, it means an 100mm apo doublet could be marketed by a brand usually more expensive than Sky-Watcher for about 400€. Food for thoughts, uh?

Seems that those buildings were engineered by the same folks who design public lighting. 😁

Thought a little more about it and they also knew about opacity and transparency; when the water is too muddy there's no point in hunting there. Also reflection, the Sun reflecting off water hides the prey so they had to chose a spot at a good angle relative to the Sun. Naturally they noticed how light scatter happens because it is another hindrance to that kind of fishing, the more troubled the water the more Sun glitters you take in your eyes, that's painful and it protects the fish. Same for turbulence inside of water, the more agitated, the less you can aim. Spontaneously, without really thinking about it, one tries to take advantage of tree shadows and such to avoid reflections, so they had a grasp of albedo. And naturally they noticed a low Sun casts reflections at the same low angle, so the equality between incidence angle and reflection angle was understood, even if not formally. There's not a long path from these observations to the idea of a line perpendicular to the plane of water and starting at the point of reflection, with angles identical on both sides. Straight lines, flat planes, points, angles, symmetry, that is the basic of geometry and it probably started there as much as in other mundane places and activities. Total transparency or total opacity of the water, plus all the in-between cases might have spurred the idea of rates, which is also a mathematical concept. From just seeing things to noticing them to parsing and studying them, that's how science began.

Try attaching a round disk of black paper or cardboard on the secondary, make it larger than any protrusion the secondary housing might have, and do a test shot. Then remove it, and make an aperture mask, a ring smaller than the mirror so the mirror's retaining clips and the screws inside the tube are in its shadow. Do some test shots, you'll know where the spike is caused.

Not with math but in a practical way.

Take a look at these tips.

I wondered about that so I just made a speedtest (Ookla), and the rate is as it was, around 40 M. Could be a coincidence, but FLO pages do flash completely in a shorter time, there's no "fast piece by piece displaying", I get the whole page in a split second.

Pages do load a bit faster for me on the continent, included those from First Light Optics.

People who have out-of-body experiences say they can go anywhere they want in the Universe instantly. If there's some truth to that it's because they don't have to drag their material body along.

Last night I staid awake between 1:50 and 3:40, hoping to see some Aquarids. My meteor observing routine is watch for 5 or 10 minutes, stop for another 5 or 10 if nothing happens, and of course keep observing if the shower begins. The 5 or 10 minute time depends on how much energy I have and how intense the shower is predicted to be. The very beginning of the time I had alloted myself saw a largish but slow and isolated cloud overhead, the type I also see in typical good october nights: they are big but tight, move at a lazy pace, and leave immense clearings of very dry air. Not october but the similarity made me sure the atmosphere would clear the same, and at the next time slot, after spending a little time at the computer, I returned to my largest window and saw a blackish city sky with no clouds in sight. Something with unusual pulsating lights instead of the customary blinking beacons made me curious but binoculars showed it as a plane flying in a curve that made its lights look odd. Some run-of-the-mill satellites crossed the sky, nothing to see here, move along. I opened the window to get a feel for the air but it was rather cold so I shut it and thereby reduced my viewing field but there was no meteor to see anyway. Time slot after time slot elapsed, and not a single meteor, so I finally decided to give in to sleep but at the very last moment - isn't it always at the last moment? - something moved on my neighbor's roof across the street. It was dark and slender, and moved like it was curling on itself swiftly, and then jumping from tile to tile. After slithering on the roof's angle it stopped, and its head seemed to disappear for a moment. Is it shoving its head inside the chimney, I thought? What is it hoping to find there? Will it have the audacity of jumping down? Are weasels that adventurous? Not this time anyway. After spending a goodly amount of time with its head buried inside the chimney, maybe pondering to enter it to hunt for God knows what, the weasel got its head out, and took a long look around, realizing it had made itself vulnerable, so it needed to assess the presence of enemies. Cats roam the roofs as freely as weasels at night, and attack them by instinct, I've witnessed it at my former home. The more massive and predatory cats dart at weasels with a ferociousness they don't display for other animals, and the underweight weasels wisely run away at full speed. But no threats this night, just me and my laser, that was of no use since I was alone but I had kept it in my hand, moving it between fingers just to not be completely idle, being completely motionless while we wait seems to be against nature. Hey, what if the beast sees the green dot close to it, will it freeze? Will it run away? Will it do something totally unexpected? Well, kind of. The weasel ignored it. I moved the beam around it, on its fur, no special reaction to the dazzling dot on the roof, but maybe because it was focusing on the source of the laser, which was obvious: me, a large potential predator in the weasel's primitive brain. Uh, that guy is clearly watching me and doing something strange, Should I worry? Should I flee? After pondering that and remaining motionless during the reflection, like we also do, the furry nighttime little burglar concluded I was too distant to be a threat, and resumed its forray among the tiles. Too bad a cell phone camera is useless in that darkness and from such a distance. At a junction between two planes of the roof, under an angle covered in zinc foils, the weasel suddenly became shorter and shorter, and finally what remained of it vanished. What? I thought, I'm sure it didn't go away, it just got shorter like a magician's assistant and then disappeared totally! There's no escape route I couldn't see, what has become of it? Did it enter the roof? Then it clicked, yes, there's no other way it could go, and if I wait for a while I'll see it exit the secret tunnel it found, no doubt after a systematic search of all potential hiding places on high roofs. A minute later the dark pointy head of the beast emerged, always nervously looking around, exited the narrow opening with an obvious effort to extract itself of a place that was not meant for its comfort. Then it resumed its frolicking form roofs to ledges, still ignoring my laser beam. I'm not too surprised by that, I've played with my laser and wandering cats at night; some are afraid of the beam, others just don't bother with it, and that weasel was the cool type. Err, if you don't hurt me I don't fear you. Now I have to ask my neighbor if she ever heard tiny footsteps inside her ceiling. It so happens her landlord has some repairs to do on that ledge, so obstructing the weasel's secret entrance is a must. There, no meteors, maybe more meteor luck this night, or maybe more unexpected stuff like that. Saw nature in action anyway.

I'm not an imager but I'm always curious to see what they do. Looking at the full-size image in the corners and at the center stars seem to be tight. Try shooting some very bright single stars of different magnitudes and colors, center and edge, that will reveal more. That is one of the tests Teleskop Austria's boss does to judge telescopes at prime focus, but the magnified patterns in a star test are a must for complete evaluation. http://interferometrie.blogspot.com/2015/11/120840-skywatcher-esprit.html

I'm finding this old thead just now. I had only one problem with my EQ-3 that required opening it, stiction in DEC; the red disks were rough. Pulled them out, smoothed them, I don't remember if I did it with fine sandpaper or a rough kitchen sponge, lubed them, don't remember with what. Stiction is gone. The other axis had the same issue when the mount was new but trying different settings with the adjustment bolts made it better. Still not good enough so for two or three weeks I turned the RA axis maybe 40 or 50 times every day, in both directions. That alone solved the RA problem without dismantling anything.

I'm using a non-mechanical, circuit-only SSD memory since 2017 and it's 10x faster but maybe head-and-motor drives still have advantages I don't know of.

How come they didn't try with Andromeda's black hole? It's big and not too distant.

That's what they all say. ?

I'm afraid one telescope only would be impossible for me because of the differences between a light bucket and a rich-field scope, but two would be possible. A 12 inch dob and a 115mm apo.

In my limited experience it is the Maxvision 34/68.

Sky-Watcher sells all types of refractors, achromats, semi-apos, apos, doublets and triplets, but Sky-Watcher sells no prism diagonals, only mirrors, so...