Alan64

Another question? No problem at all. You've come to the right place. Your 200mm Schmidt has a focal-length of 2000mm, and is considered a "slow" telescope, at its f/10 focal-ratio. The nice thing about telescopes with slower focal-ratios is that most any inexpensive eyepiece will work very well and provide pleasing views. For the 1.25" format, a 32mm ocular would afford one of the lowest powers practical... 2000mm ÷ 32mm = a power of 63x; a 40mm: 50x, and the very lowest power available in the 1.25" format... http://www.365astronomy.com/32mm-GSO-Plossl-Eyepiece.html http://www.365astronomy.com/40mm-GSO-Plossl-Eyepiece.html Vixen makes very good Plossls... https://www.firstlightoptics.com/vixen-eyepieces/vixen-npl-eyepieces.html I have the Vixen 6mm and 30mm... The 30mm's field-lens is extraordinarily-large, and through which to look. The Antares Plossl line-up... http://www.rothervalleyoptics.co.uk/antares-plossl-eyepieces-125.html But where a Cassegrain really puts forth lies at the moderate-to-high powers. On most nights, you can use an 8mm... 2000mm ÷ 8mm = 250x, and for the Moon, the planets, and double-stars... http://www.365astronomy.com/8mm-the-planetary-uwa-eyepiece-58-degrees-1.25.html This 9mm(222x) has a somewhat wider field-of-view... http://www.365astronomy.com/TS-Ultra-Wide-Angle-Eyepiece-9mm-1.25-66o-with-Improved-Coating.html If you can wait on the boat, and do without the chromed barrel, this is the same eyepiece... http://www.ebay.co.uk/itm/1-25-31-7mm-Ultra-Wide-Angle-9mm-Eyepiece-Lens-66-Deg-for-Telescope-Best-track-/152129833857?hash=item236ba50b81:g:G8wAAOSwAuNW3lNp Incidentally, you do not have to purchase eyepieces and accessories of the same brand as the telescope. I've encountered some who think that you do, that they must match, but that is incorrect. Any brand of telescope may use any brand of eyepiece or accessory. For a relatively-moderate power, something in the 16mm+/- range would do nicely. Avoid eyepiece sets, such as these... https://www.harrisontelescopes.co.uk/acatalog/795.jpg https://www.harrisontelescopes.co.uk/acatalog/celestronepkit.jpg https://www.harrisontelescopes.co.uk/acatalog/series4000set.jpg https://images-na.ssl-images-amazon.com/images/I/51YYSxbn9IL._SY355_.jpg It's best, rather, to put together a set over time -- over the weeks, the months, and the years even -- and tailored to your observing habits. Always give careful thought to what is placed between the eye and the sky at night, and for best results.

Very good; then what you need, for use at night, is a 90° STAR diagonal. You can choose either a prism-type or a mirror-type. A quality prism-type is more costly. Synta of China equips their current line-up of Schmidt-Cassegrains with this inexpensive prism star-diagonal... http://www.rothervalleyoptics.co.uk/celestron-90-degree-star-diagonal-125.html I have one, and it's quite good, especially for the low price... I've used that diagonal with a Celestron C90 90mm Maksutov, which is similar in design to your Schmidt-Cassegrain, and I'm pleased with the views; no complaints here. Others have had less-than-stellar experiences with it, and I attribute that to the lack of quality-control at the factory there in China. Alternatively, and unfortunately, the next step up in a prism is bit more costly... http://www.rothervalleyoptics.co.uk/baader-prism-diagonal-t-2-90-degree-32mm.html That's just the prism and body, which requires an eyepiece-holder and nosepiece to complete it... http://www.rothervalleyoptics.co.uk/baader-125-helical-focusing-eyepiece-holder-t2.html http://www.rothervalleyoptics.co.uk/baader-nosepiece-125-t2.html You'd never need another, unless you get a fast refractor in future to complement the Schmidt -- for low-power, wide-field, binocular-like views -- in which case you'd want a mirror-type. In so far as the prism-types available, indeed, in so far as all things man-made, it all depends on the level of quality desired. The mirror-types are more plentiful due to the ease in their manufacture, and consequently permeate the marketplace... http://www.rothervalleyoptics.co.uk/altair-astro-125-dielectric-star-diagonal.html Now, if you'd like to use your telescope during the day, for viewing land targets, birds, or other, you would want either a 45° or 90° AMICI(erect-image) diagonal... http://www.rothervalleyoptics.co.uk/antares-45-erecting-prism-125.html http://www.rothervalleyoptics.co.uk/antares-90-erecting-prism-125.html This is what a 45° Amici looks like(left)... The 45° would be comfortable for viewing land targets close to the ground, whilst the 90° would be more comfortable for viewing objects higher up, like a mountain top or the top of a tall tree nearby. If your visual-back might accommodate, and for use at night... http://www.rothervalleyoptics.co.uk/altair-2-dielectric-diagonal-99-quartz-push-fit.html ...then to use 2" eyepieces and accessories.

Ah, a 200mm Schmidt; I thought so. That looks to be a very nice kit, indeed. You have several options for a 90° star-diagonal, and for use at night. During the day, for land targets, there are also 45° Amici-diagonals available. But we'll need to see an image of your visual-back, there at the rear of the telescope, like this... Are you able to insert a diagonal into the v-b, then tighten the screws to hold it; or do you need one that screws onto the v-b, which is common with that type of telescope? This is an example of one that screws onto the v-b... https://www.astronomics.com/images/Product/large/11608.jpg ...and in comparison to the standard type... Also, when you say "horizontal prism", are you referring to the kind that's used during the day, for corrected, upright images? If so, that's an Amici, or erect-image, diagonal.

Hello Jimmy, and welcome. Please post a nice clear pic of the kit, and to help us to help you, like this... Or, locate the specs label on the telescope itself, and list its information here. I'm thinking that it's a 150mm or 200mm Schmidt-Cassegrain. If it is, then Schmidts do require collimating, alignment of the optics inside, especially in that it's used. That may be part of the problem. The optics could be fouled as well, and that would result in less-than-stellar images. "LX90" refers to the mount, not to the telescope primarily, so we'll need some more information. Cheers.

Iain, that's a very if not extremely good afocal snap with a phone-camera. Feel free to ramp the power up to 200x and beyond when observing the Moon. I took this shot at almost 200x with my 150mm f/5... Congratulations on the new kit!

Your Newtonian is a 130mm f/7, therefore the secondary off-set is not going to be that apparent at f/7. Note the off-set here with my 150mm f/5, on the right... On the left, an f/4, and even faster, therefore the greater the off-set. Fortunately, the off-set occurs automatically during a normal collimation procedure, and does not require a separate step to perform. Once you get the collimation-cap, and a Cheshire too, hopefully... https://www.firstlightoptics.com/other-collimation-tools/premium-cheshire-collimating-eyepiece.html ...then, you can insert the collimation-cap where an eyepiece normally goes, aim the telescope at a white, blank, illuminated wall or other, place a small camera over the pinhole of the cap, zoom in if needed, snap a shot of the scene as I have many times, then post it here for us to have a look. The collimation-cap allows you see the entire optical system inside at a glance. Incidentally, a secondary off-set is to ensure that all of the light collected by the primary mirror reaches the eye. But, again, there will not be much of an off-set with your f/7 Newtonian after a proper collimation with the cap, and the Cheshire... A Cheshire is useful for for centering the secondary mirror directly under the focusser... The secondary mirror must also appear perfectly round, as a circle, or very near to it, as shown. A Cheshire also serves to ensure that the center of the eyepiece is aimed directly at the center-spot of the primary mirror... I look forward to seeing a nice snapshot of your secondary scene. Cheers,

Yes, I have the file saved, too. Cheers.

I don't know if 'twill or not. It's embedded within an Italian website(.it). I just discovered it recently, within the last month I think.

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