Alan64

I had been wanting a Maksutov for a few years before I got my own, about a year ago or so. It makes for a very good simulation of a 102mm f/19 or even a 115mm f/17 achromatic-refractor. At focal-ratios like that, a refractor doesn't need exotic glasses to reduce or even to eliminate false-colour. I had thought about a 150mm, but not for long. For one, they're a bit more expensive, but the real reason was due to the longer acclimation period required prior to observing.

For the time being, you can transform the EQ-2 into a rudimentary yet fully-working alt-azimuth. This is my Meade 114mm f/8, and the EQ2-class mount that came with it... You simply throw the RA-axis back until the butt of it rests upon the latitude-stop bolt, then clamp it to secure... The EQ-2 will go almost all the way back, but far enough to effect the transformation, and at 85°, with my own in any event... The counterweight must be used, still, and to balance that side of the mount opposite the telescope. You then unclamp both axes, and motion the telescope left to right, and up and down, just as a dedicated alt-azimuth. With the axes clamped, both slow-motion controls can be used as well; fully operational. If that helps, you can certainly continue to use it that way. If you want the ability to throw the RA-axis back all the way to 90°, if your own does not allow that as it comes, a notch will need to be made into the body as shown, carefully, and to accommodate the width of the stop-bolt... The notch must not be made too deeply, or it will go past 90°, to 91° or more.

That due to at least one of two things. One, the ground, figured and polished surfaces of a short focal-ratio, crown-and-flint doublet, the curvatures, are steeper(convex), deeper(concave), a bit more exotic if you will. That requires more attention, and labour, in getting it just right. It's the same with a 150mm f/4 parabola vs a 150mm f/8, among Newtonians. Then, imagine yourself at a shop at the end of a dark alleyway. You know absolutely nothing about telescopes, yet one is earnestly desired nonetheless. The sign above the shop is faded and soiled. You can barely make out the name: Soso Telescopes & Pet Shop. The door creaks as you enter, and a bell tinkles, alerting the proprietor... "Good Day. I'd like a telescope, please. Ooooh, that one's nice and long. How much?" "220." "Hmm, what's that short one over there, by the dead parrot?" "It's the same as the long one, but shorter." "I can fit that one in my car! How much?" "420."

The rings are holding a 90mm f/10 achromat within that image. In so far as the spacing between the rings, they must also accommodate a shorter, 80mm f/6 achromat to which the rings originally belong; two telescopes, one set of rings. Imagine my delight when I discovered that the one set of rings also fit the 90mm f/10. In so far as the bar's length, that's to balance the 80mm f/6 when using a 2" diagonal and a 2" ocular, to move it farther forward. In that I did not purchase a set of rings and a dovetail-bar for the 90mm f/10, I can assure you that I will not be purchasing an extra set of rings for a third, then to have a useless spare on hand. For one, I'm a visual observer only, albeit with the odd afocal-shot taken with a small point-and-shoot camera, but only to demonstrate what may be seen during a live view, through this eyepiece and that, and this telescope and that. Two rings per telescope, maximum, in my stable, or sometimes for two, if I can get away with it. I don't even have premium rings for my premium refractor... ...as they are not necessary. Those work, and serve, admirably. Then, what does all of this have to do with securing a telescope within its mount's saddle?

Yes, like this... Any that are within the bar must be counter-sunk.

I think you mean less false-colour, rather than coma, being that the "Startravel" is a short-achromat, a refractor. Gracious, at f/5 I think it is, with lots of "rainbows". As you may know by now, the instrument is for the dimmer deep-sky delights, and so as not to rile it up. For something a bit more down to Earth in outlay, for the brighter and brightest objects, like the Moon, the planets and super-stars... https://www.firstlightoptics.com/bresser-telescopes/bresser-messier-ar-102l-1000-refractor-ota.html ...or... https://www.firstlightoptics.com/bresser-telescopes/bresser-messier-ar-127l-1200-refractor-ota.html Although, both will exhibit some false-colour, the 127mm in particular, but not nearly as much as the one you have at present. Another choice, and perhaps the best of all, would be a 127mm Maksutov... https://www.firstlightoptics.com/maksutov/skywatcher-skymax-127-ota.html ...or... https://www.firstlightoptics.com/bresser-telescopes/bresser-messier-mc-127-1900-maksutov-cassegrain-ota.html (I have this one, and under the Explore Scientific marque) A 127mm Maksutov is the "sweet spot" among the varying apertures of the design; an effective aperture, and reduced time in waiting for the telescope to adjust to the outdoor conditions prior to observing. If you choose a Maksutov, you will want to get a dew-shield for it straight away; for example... https://www.firstlightoptics.com/dew-prevention/astrozap-flexible-dew-shield.html You don't want the meniscus(the front "lens") to dew up on humid nights. It will also help to keep bugs, dirt and pollen at bay.

Not surprising, as Takahashi's in-house operations are more along the lines of a mechanical nature, with their regular offerings at least; the tubes, the focussers, the mounts and tripods perhaps in addition. The fluorite-doublet of my own was produced by Canon-Optron.

Incidentally, Takahashi is offering an achromat, albeit an 80mm f/10, for the first time in decades... https://www.highpointscientific.com/takahashi-starbase-80-beginners-refractor-telescope-stk0800 ...and perhaps guaranteed to knock your socks off, achromatically.

It's anastigmatic. I would hope so.

In a Newtonian's favour, aperture-fever cannot be remedied with a refractor, true, but at times one does prefer that qualitative over that quantitative. And then, I had started with a pea-shooter of a refractor, yet the mold was set nonetheless. I suppose that makes me a bit partial. Acquiring that 80mm 20 years later was most welcome, and exciting. Then, about ten years later, I got a 102mm achromat, but returned it shortly thereafter. At about the same time, I got an 8" f/5 Newtonian, but I've yet to observe through it, as I had gotten an OTA only. I do want to see what it may show to these ever-aging eyes.

I love his books, particularly the older publications. I like the "Sky at Night" video of Sir Patrick, in 1961, with his assistant, and the 24" Newtonian. Unfortunately the clouds rolled in, and just as they were about to observe.

"...a 6-inch Cooke refractor and a 12-inch cassegrain...", according to observatory's website. The refractor is physically longer than the Cassegrain. Perhaps they used both for the viewing, if both were present at the time. I didn't see it in 1986, as it was too far away. At that time, all I had was this, a 60mm... I didn't have binoculars, either. But by the early 1990s I had an 80mm, and saw the dark pock marks left behind on Jupiter's surface when the remnants of Comet Shoemaker-Levy impacted the planet. That comet had disintegrated, and never to be seen again. It turns out that the comet had been captured by Jupiter about 20 to 30 years before, and began orbiting the planet. Imagine, what a horrific thing if that happened here. The use of drugs would skyrocket, I expect, and in not knowing when the inevitable was to occur. My maternal grandfather, in a later recollection, saw Halley's at the age of 5, but that was during its last visit in 1910. It was so close to the Earth that a telescope wasn't needed. Photographs were taken of the comet in 1910... Note how Halley's speeds up as it nears the Sun... https://en.wikipedia.org/wiki/Halley's_Comet#/media/File:Halley's_Comet_animation.gif Yes, indeed, that 127mm will be an eye-opener for you. Incidentally, the shorter 127mm that John is considering would also be ideal for comet-hunting.

A 127mm aperture would be for the increased resolution(detail) only I would think, whilst observing the Sun; certainly not for the increase in brightness. Wouldn't false-colour intrude in that as well.

Hi Neil, Have a look at this... I don't know if you've ever seen one, or have ever owned a smaller refractor like that one. That one being a 50mm f/12, 10mm smaller in aperture compared to the ubiquitous 60mm instruments produced for decades. I had blackened and flocked it throughout, as well as updating a feature or two on the outside. I've observed with it after the fact only once. I saw a globular-cluster through its "eye", M22 I think. It wasn't all that dim, and with averted-vision I was able to detect the "diamonds" sparkling within. Now, I never suggest a refractor that small to those first starting out with a refractor, with 80mm being the suggested minimum. You do want one's interest to be held in the beginning, and to grow. That's another nice thing about refractors, the sparklings oft seen, as if the object is alive, a sentient-being even. Case in point: on the left, M13, the great globular-cluster in Hercules, and as seen through my 150mm f/5 Newtonian. On the right, M13 as seen through my 100mm f/8 refractor... Now, I'm not an imager; visual-use only. When I observed M13 through the Newtonian, the image was pleasing enough, but I saw no sparkling within. Needless to say, I did see that wonderful characteristic through the refractor; glorious.

This is the collimation-scene of an 80mm f/6, a crown-and-flint achromat, which did not require collimation upon arrival... Well, perhaps a slight tweaking is necessary, particularly since it is at f/6. You do want to push one for all it's got, in magnification, per its aperture. Alas, it exhibits a blemish, and when having observed Sirius in this instance... I see that all the way until it's at perfect focus. It doesn't seem to degrade the images however; I hope, I trust. On the other hand, the collimation scene of a 70mm f/13 achromat... That's not so good. But what I found, mainly, in that instance, was a wonky focusser.

It is not impossible to collimate a triplet in a home setting. The OP would need to research to go about that, if collimation is in fact required.

I've already hinted that it requires collimation. I, too, am suspecting that, and as you did, and in agreement with John.

You asked for information.

My reply was in reference to the problem with misalignments that occur with triplets, the subject of this thread at present, and other objectives with more than two lens-elements.

I was referring to refractors only, and to the OP's Tele Vue NP101is, a quadruplet-apochromat.

Triplet-apochromats are favoured by imagers, although they are used on occasion for visual-use. Incidentally, your Tele Vue is a quadruplet. Consequently, you'll want to handle that one as one would a newborn babe. Then, for visual-use only, a doublet-apochromat serves admirably, and are, generally, problem-free. Triplets, if misaligned, are usually not an at-home repair. They are sent off instead, for servicing.

I read once where two friends compared their telescopes one night. The visitor brought their 127mm refractor, albeit an apochromat possibly. The host brought out their 200mm Schmidt-Cassegrain. The host had a sidekick for the 200mm, an 80mm refractor. But the 80mm, apparently, wasn't that much of a competitor to its perhaps unsuspecting owner, and to their 200mm reflector. After the session was over, the host sold the 200mm reflector shortly thereafter. It is not known, however, if it was replaced with a 127mm, or even a 150mm refractor. I found that result rather interesting.

Yes, I was working outside after midnight, and during a break I walked down the driveway and looked into the sky, and there was Mars rising in the east. It had cleared the tops of the trees. I waited until it climbed a bit higher and brought a telescope out... I had been wanting to test that 100mm f/4 Newtonian further, as it's not really suitable for the higher powers, but since it has a 4" aperture I'm determined to push it. I did just that, that morning, and then snapped this afocal-shot of the planet at a power of 200x... Mars is bright, and closer to the Earth during this time. It's going to get brighter still over the coming weeks. Opposition of the planet will occur on October 13th, when it will be at its very brightest, and a little larger even. I'll be testing that star-box further still near that time, but I'll need to dim the planet down a bit with a filter, and perhaps to see its details a bit better.

In the above, the poster has a point about a 127mm f/10 achromat being a beast, but I have to disagree as to the first part, for it is a refractor, and a 200mm instrument would be ££££, and for an achromat even; not to mention the debilitating expenditure in acquiring a mount just to support it, to get it off of the ground. It is also interesting to note that the gentleman above has no refractor listed within his signature; an oversight perhaps, or not. But it's not about the aperture of a refractor competing with the aperture of a mirrored telescope. Quite frankly, mirrored telescopes spend their days attempting to emulate the level of sharpness and contrast that only a fine refractor can provide, for a refractor uses lenses instead of mirrors, is 100% unobstructed, and generally requires no maintenance. It is the very first and oldest design of telescope. "The Original & Best", like a bowl of Kellogg's corn flakes, albeit for the lack of a better analogy. Then, we have Mother Nature. Our own eyes, which utilise lenses by which we may see, and most clearly in youth. If that were not enough, there are far-away galaxies that act as telescopes themselves, which are known as lensing galaxies. Peering into my crystal ball, albeit cracked, I see, in the OP, a desire to see with his own eyes what a refractor is really like. I suggest that an 80mm f/8 or f/11 is capable of demonstrating that. But no need to worry, for even though a mirrored behemoth, relatively, may beckon with its brighter reflections, the refractor will always be there, waiting, and beckoning in its own not-so modest might and right.