Alan64

Dave, is this what you're looking for... http://www.forumskylive.it/Public/data/serastrof/201281510358_Astro Babys Guide to Collimation.pdf

I recently center-spotted the primary mirror of my 100mm f/4 tabletop. All you need is several sheets of white copy paper, a compass, transparent-tape, a permanent marker and a polyvinyl(or paper) notebook reinforcement. I made several patterns, and finally decided on one that would show just a sliver of the mirror all the way around... The pattern must be cut as perfectly as possible. The sharp compass-point produces the center point, and I enlarged the point's hole only slightly to effectively mark it with a permanent marker... I then took one of my discarded patterns and made a sizeable hole in the center. Next, I placed a narrow strip of tape across the hole and lightly adhered the top of the reinforcement to the underside of the tape, then laid the pattern over the mirror, centered the reinforcement over the mark and pressed it down, then peeled off the pattern and tape... I then cleaned the mark away with a cotton swab. It worked like a charm... The secondary scene as viewed through a collimation-cap, before and after the center-spotting... Incidentally, the telescope arrived nigh on perfectly collimated. It also has a glued-in primary mirror, and is essentially the same kit as the Sky-Watcher Heritage 100P. In the case of your spherical mirror, I'm thinking that it might be necessary to add some thicknesses of paper on the underside of the pattern near the outside edges so that the reinforcement will just hover in the air above the mark before you press it down. I may be wrong about that, however, as I do not have that particular telescope.

There could be pieces of metal shards lodged inside, and from the factory. It wouldn't be the first time. When cleaning out the old grease, I've found that charcoal-lighter fluid, the kind for grilling outdoors, works wonderfully in removing all traces of the old grease, with rags and an old toothbrush. I did the same to my EQ-3. It's much smoother now. When re-greasing, only small amounts of the new grease are needed, particularly with the Super Lube.

If you're up to it, and good at tinkering, disassemble the mount-head, both axes one at a time, and clean out the old factory grease and re-lube with a quality grease. I use this for all of my astronomical equipment... https://www.amazon.co.uk/d/Lubricants/Super-Lube-Synthetic-Grease-Syncolon-Multi-Purpose/B000XBH9HI It's PTFE, or Teflon, based. There are other greases that can be used as well, and instructions online to help in disassembling.

A fellow amateur, who lives in Denmark, saw a few of the Bresser refractors first-hand, and was of the opinion that they, the refractors, were a notch up in overall build-quality compared to those of Synta(Sky-Watcher, etc); for what it's worth. The primary mirror will be a parabola, of course.

If you have recourse to recovering your funds, if it doesn't prove to be as advertised, I'd say go for it, and before someone else goes for it.

Aside from the wrap, it nonetheless looks to be new, and is indeed a 150mm f/5 Newtonian; perfect. The image within the link is of the longer f/8 variant, which are usually mounted on a Dobson alt-azimuth or on a large equatorial(EQ-6).

The 45° Amici diagonal is really only suitable for daytime/terrestrial use; for observing birds and what-not. Consider a 90° star-diagonal for astronomical use at night... 1.25"... http://www.rothervalleyoptics.co.uk/antares-90-star-diagonal-125.html 2"... http://www.rothervalleyoptics.co.uk/altair-astro-2-mirror-star-diagonal.html ...for examples.

The 100ED would indeed be worth the striving towards, as the Japanese Ohara ED-glass element is FPL-53, and the best optical-grade glass in the world at present, second only to fluorite, with the other element being of German Schott crown.

I read somewhere, recently, someone saying not to let Sky-Watcher know just how wonderful the 100ED really is.

If you didn't have a fast 102mm refractor, I'd say go with the 102mm ED. What about a 150mm Maksutov; that for lunar and planetary, and the fast refractor for wide-field deep-sky?

Those are actually quite, quite good.

Our eyes, as humans, are weak, compared to an animal of the night equipped with tapetum lucida. For them, the same dark site as described must appear as an overcast day does to ourselves, and at high noon even.

...wise decision. The AZ4 will provide a solid, stable and lasting platform for the refractor. "'Another nice feature is the altitude and azimuth scales marked in one-degree divisions — a nice aid to locating celestial objects if you have a Palm or Pocket-PC planetarium program.' Ade Ashford - Astronomy Now, Dec 08" This is the manual for the AZ4, for both: the steel-legged and aluminum-legged variants.... http://www.opticalvision.co.uk/documents/163.pdf The aluminum-legged version is lighter, of course, but it also sits closer to the ground when the legs are not extended, albeit with less stability overall perhaps compared to the steel-legged. The 120mm f/5 has a short tube, but only in relation to its considerable aperture, and when compared to an 80mm. One of the benefits of refractors and corrected-Cassegrains(SCTs and MCTs) is the ability to sit, and remain seated whilst observing. Therefore, before purchasing either one, get out what you might anticipate as being your favourite observing chair, and a rule, make measurements, and according to the specs on the last page of the manual. Several variables require consideration before deciding on which one to get.

...splendid choice... A 2" diagonal with a 1.25" adaptor accommodates 1.25" eyepieces as well... In addition, by inserting a .965" adaptor into the 1.25" adaptor, one can use old-school .965" eyepieces even... A short-tube 120mm refractor is a bit much for the included AZ3 alt-azimuth mount within said kit, and when extra weight is added in the form of eyepieces and accessories, well. Give it a go with the AZ3 for a spell, and see how it works out. There is the option, however, of getting the OTA separately... http://www.firstlightoptics.com/startravel/skywatcher-startravel-120t-ota.html The OTA is £30 less than the kit, therefore the AZ3 is thrown in at a £67 discount. A more robust alt-azimuth mount... http://www.rothervalleyoptics.co.uk/skywatcher-az4-1-alt-az-mount-with-aluminium-tripod.html Whilst that one would easily handle the refractor, and any and all eyepieces and accessories, it does not have slow-motion controls, as the AZ3 does, for some inexplicable reason. http://www.teleskop-express.de/shop/product_info.php/info/p8069_TS-Altazimuth-Mount-with-Fine-Adjustment-and-Quick-Release.html ...and ideal, but for yet another inexplicable reason, it's not sold in the UK. It's very popular for smaller telescopes throughout the rest of the world.

Hello Dave, A 2" 32mm, as described, would probably be the only 2" eyepiece in your collection. Some get a 2" ocular in the 25mm-ish range, too. But the 1.25" oculars are more than adequate from 4mm to 25mm, for most people. My 2" 32mm is the only one I have, and I don't really feel the need for any more. If you plan on getting that 2" 70° 32mm eyepiece in future, then it would need a 2" mirrored star-diagonal, and with a 1.25" adaptor as it never hurts to have a spare. Although I'm unaware of 2" diagonals being sold without 1.25" adaptors. Most come with one in any event. On the other hand, if you decide on the 1.25" Vixen NPL 50° 30mm instead as your lowest-power eyepiece, then consider a 1.25" mirrored star-diagonal. Yes, one doesn't have to spend a fortune on eyepieces to have a rewarding experience 'neath the starry void.

The 120mm f/5 will gather a lot of light, and the Baader semi-apo filter sounds to be effective, per research: win-win. The achromat has a focal-length of 600mm. That's all that's needed when choosing eyepieces and a barlow. The lowest-power eyepiece, and for great wide-field views, will be a 32mm, and since the focusser is able to accept 2" eyepieces, this 2" 70° 32mm, combined with a 2" 90° mirrored star-diagonal, would be a great performer, and pictured at right... http://www.firstlightoptics.com/skywatcher-eyepieces/skywatcher-panaview-2-eyepieces.html 600mm ÷ 32mm = 19x, and quite close to that of a pair of 20x80(20x) binoculars. I have the same 32mm, and illustrated here alongside my Synta 1.25" 25mm... Just by looking at it, one can get a sense of its performance. The 1.25" 45° Amici-prism terrestrial/daytime diagonal supplied with the kit can be used at night, but it is not designed for astronomical use, therefore its performance will be lacking. The kit is sold with one, and in a terrestrial/daytime configuration. A 90° mirrored star-diagonal is recommended for fast refractors, for astronomical/nighttime use, and for best performance... http://www.firstlightoptics.com/diagonals/skywatcher-di-electric-star-diagonal.html A 2" eyepiece and diagonal is not required however. For examples... A 1.25" 50° 30mm(20x) Plossl... http://www.firstlightoptics.com/vixen-eyepieces/vixen-npl-eyepieces.html I have it, too, and it's a great performer. I chose it over the GSO and Baader 32mm Plossls, and after careful research... ...and a 1.25" 90° mirrored star-diagonal, for example... http://www.rothervalleyoptics.co.uk/altair-astro-125-dielectric-star-diagonal.html 600mm ÷ 30mm = 20x(2x barlow: simulated 15mm/40x), (3x: 10mm/60x) 600mm ÷ 25mm = 24x(2x barlow: 12.5mm/48x), (3x: 8.3mm/72x) 600mm ÷ 10mm = 60x(2x barlow: 5mm/120x), (3x: 3.3mm/180x) Examples of better-quality barlows... 2x: http://www.rothervalleyoptics.co.uk/antares-x2-twist-lock-barlow-lens-125.html 2.25x: http://www.firstlightoptics.com/baader-planetarium/baader-classic-q-225x-barlow.html 3x: http://www.rothervalleyoptics.co.uk/antares-x3-twist-lock-barlow-lens-125.html A barlow is placed into the optical train, and therefore needs to at least match the quality of the refractor's doublet-lens and the eyepieces, and for better performance. The lens element of the Baader Classic Q 2.25x, listed above, is removable, and at 1.3x. I recently read of a fellow amateur with a GSO 2x/1.5x. As he removed the element to place it on an eyepiece, he dropped it and chipped the lens, therefore extra care is needed when handling. Barlows are used for visual, and imaging. For visual, its use is two-fold... 1. To multiply the number focal-lengths within a small eyepiece set, as demonstrated above. 2. To reach a higher magnification without having to resort to using an eyepiece with a tiny eye-lens and short eye-relief. For example, this is a 4mm orthoscopic... You know that one has to be difficult and even painful to look through, eh? Instead of using it, 3x-barlowing a 12mm, and for a simulated 4mm, makes for much greater eye comfort... That combination of a 60° 12mm and a 2.8x barlow actually simulates a 4.3mm; but close enough, and O! the wonderful things I've seen with it! Then, there are eyepieces that have a built-in barlow, with said greater eye comfort, and when compared to a standard 4mm orthoscopic or Plossl... http://www.firstlightoptics.com/skywatcher-eyepieces/skywatcher-uwa-planetary-eyepieces.html

An 180mm Maksutov-Cassegrain would make for a splendid celestial "microscope"; for the Moon and the planets and double-stars, and would simulate a 140mm f/19 refractor. Observing quite a few of the smaller, single deep-sky objects should be possible, too. Now, a 30mm ocular, which gives a wide-field low-powered view at 25x via my 6" f/5 Newtonian, would realise 90x with said Maksutov: a considerable magnification, and one of the lowest practical powers. Perhaps more people than we know look upon the short tubes of the Cassegrains thinking that one would make for a capable deep-sky instrument, until it's there before them. Notice how the 2700mm focal-length of the 180mm Maksutov is folded into three sections within the optical tube... Therein, its true nature is revealed.

Physics is incapable of being "unfair". It is what it is.... I have an 80mm f/6 achromat. It even came with its own vampire-star... At f/6, the aberration is well controlled, up to a moderate magnification... However, research the colour-suppression performance of the faster Synta 80mm f/5 achromats(Orion, Sky-Watcher, iOptron, et al). Then, add an extra 40mm to said f-stop. The aberration increases with aperture when the same f-stop is maintained. Again, a 120mm f/5 achromat should offer, at times, wonderful if not stellar deep-sky performance, and that is its strong suit.

A 120mm f/5 achromat is going to exhibit oodles and gobs of false colour on every bright object you observe. Do you remember kaleidoscopes as a kid, and it gets worse as the magnification is increased. A fast achromat however excels at observing the dimmer deep-sky objects; not too terribly bright, mind you. If you want to observe mostly at higher magnifications, then go with either a 150mm f/12 Maksutov, or a 150mm f/5 Newtonian combined with a barlow. The Maksutov would be a near-simulation of a 120mm f/15 planetary refractor, and perfect for observing everything up close. Similarly, a 127mm Maksutov would mock a 90-100mm long-focus refractor. On the other hand, a 150mm f/5 Newtonian would imitate a 120mm f/6 apochromatic refractor... http://www.firstlightoptics.com/reflectors/skywatcher-explorer-150p-ds-ota.html Newtonians are apochromatic, meaning "totally without colour"; that being false colour, or chromatic aberration. With a better-quality 2x barlow, the 150mm f/5 would enable magnifications up to 250x and beyond, in good and better seeing conditions; and all the way down to 23x with a 32mm ocular for wide-field deep-sky objects and vistas.

I'm near-sighted, and have worn glasses since my relative youth. In any event, what I had meant by my statement regarding the camera's shortcomings, is in that it fails to capture the sharpness of a live view. This is a photograph I took with the Tanzutsu 60mm f/15... It appears nice and sharp, eh? Ah, but not nearly as sharp as the live view at the time the photograph was taken. Here's a close-up... During the live view, within the circled portion, I saw what appeared to be dozens if not hundreds of what I term "hills and dales", within that ridge. The event has me almost convinced that the achromatic doublet was not manufactured by Tanzutsu, but by the Japanese optical house, Towa, instead. The two companies were in collaboration with one another at some point in the past. I wouldn't be surprised if the doublet was a part of Towa's old stock, and possibly from at least a decade prior to the refractor's manufacture.

A 5" Zeiss apochromat might exhibit only one thing: perfektion.

At f/6, 480mm, the Antares will indeed exhibit its fair share of false colouration, and the camera only accentuates it further in the resulting photograph. I've been told that the camera itself, even, will introduce colours, particularly when held at an angle. Here's another shot through the Antares, and at a higher magnification. However the colour wasn't as strong when observing with the eye...

The Moon was almost full, waning I think, when I took that photograph, thus the use a variable polariser to dim down the brightness.

Refractive family portraits... Takahashi FS-102, a 102mm f/8 apochromat... Purchased new in 2003, it is a consummate "pupil", my having split Sirius in the same year when it and its companion, "The Pup", were practically adjacent to each other; said companion having blinked in and out, but never having disappeared entirely within the Dog's intense glare. The separation between the two has steadily increased since that time. I attribute said feat to the refractor's exquisite calcium-fluorite doublet, known for its relative absence of light-scattering... Tanzutsu 60mm f/15 achromat, and upgraded to a 1.25" focusser... Made in Japan in 1987 or '88, this example was purchased as new old-stock earlier this year. Almost 5" had to be cut off of the optical tube, from the front, and in order to effect the new 1.25" format. An extra tube-baffle was added, and ultra-flat black spray paint applied throughout the optical path where necessary, from the front edge of the dew shield to the 1.25" visual back. I had always wanted a long-focal achromat, albeit only a 60mm. Lastly, the most recent acquisition: an Antares 805 80mm f/6 fast-achromat... It, too, will need enhancing, but as it stands I was able to view the Airy disc of the brightest star within Orion's Trapezium, designated "C", rather distinctly and under high magnification. Nonetheless I consider it to be little better than a guidescope with less than stellar optical quality. An afocal image via the Takahashi, and simply by holding a point-and-shoot camera up to the eyepiece... Likewise, via the Tanzutsu... ...and via the Antares... Chromatic abberation is well-controlled with this example, but present nevertheless. In every instance, the Canon S110 always falls short of that seen during a live session.