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Hi, Looking for a 12" DOB (or larger) which can be transported to Prestwick, Ayrshire. Any brand, as long as the telescope is optically sound and in good working order. I'm a reliable buyer who has bought and sold on this site before. Thanks, Mark
Galaxy Centaurus A ( NGC 5128 ) in the southern constellation Centaurus ( please click / tap on image to see full size ) ............ Updated again - to try to bring out more faint detail ... ............ Updated images ... ............. Originals ... ( 100% crop ) Centaurus A is relatively near to us in the local group of galaxies and is around 11 Million light years away. The unusual shape of Centaurus A is believed to be due to an ancient collision between a large elliptical galaxy and a much smaller spiral galaxy. With an apparent magnitude of +6.8, Centaurus A is the fifth brightest galaxy in the night sky and in the middle of the 20th century it was identified as being the strongest radio source in the Centaurus constellation. Details: Galaxy - Centaurus A ( NGC 5128 ) Image ( Nova.astrometry.net ): Center (RA, hms): 13h 25m 28.924s Center (Dec, dms): -43° 01' 25.486" Size: 60.5 x 41.1 arcmin Orientation: Up is -89.9 degrees E of N Telescope: Orion Optics CT12 Newtonian ( mirror 300mm, fl 1200mm, f4 ). Corrector: ASA 2" Coma Corrector Quattro 1.175x. Effective Focal Length / Aperture : 1410mm f4.7 Mount: Skywatcher AZ Eq6 GT Guiding: TSOAG9 Off-Axis-Guider, Starlight Xpress Lodestar X2, PHD2 Camera: Nikon D5300 (unmodified) (sensor 23.5 x 15.6mm, 6016x4016 3.9um pixels) Format: 14bit NEF Long exposure noise reduction: off Filter: none Calibration: No darks, just master bias and master flat HDR combination of eight sets of exposures (27, 28 & 29 April 2017): 85 x 240 sec ISO 800 16 x 120 sec ISO 800 16 x 60 sec ISO 800 16 x 30 sec ISO 800 16 x 15 sec ISO 800 16 x 8 sec ISO 800 16 x 4 sec ISO 800 16 x 2 sec ISO 800 Pixinsight May 2017 Links: 500px.com/MikeODay photo.net/photos/MikeODay www.flickr.com/photos/mike-oday
I have had my 300P dobsonian for nearly a year now, and it has occurred to me that I finally may be qualified enough to write a review about this little beast. I think it would be good to avoid details on how it was delivered or what accessories I have bought for it. Similarly, I will not spend much time discussing how it performs when observing in detail, because that belongs, I believe, somewhere in the observing section. Anyway, as you might have guessed, Skywatcher Skyliner 300P dobsonian telescope is no midget. Simply put – it’s big. Its OTA is big, its dobsonian mount is big, it weighs a lot, it’s pretty hard to handle; pretty much as you might expect. I reckon that having a 12” dobsonian (solid tube) is the reasonable maximum for one person (albeit strong) to handle. With smaller telescopes, like 4.5” or even 8” ones, transportability of such device is not really a primary concern for most people, but when it comes to 12” and larger, moving the thing about can really become an issue. Luckily for me at least, I am – I like to think – a strong person, so I had no problem to devise an ideal transporting procedure when I want to take this baby out for observing. I am fully aware that the primary concern when moving a telescope is its weight – I am afraid that I do not know the exact figures of 300P, but if I would guess, I would say the telescope weighs some 40 kg (sorry about the metric), with distribution being 50/50 mount/OTA, but I cannot be sure. I have described my first impressions of the scope here: Skyliner 300P dimensions: Base diameter: 64 cm Base (mount) height: 78 cm OTA diameter: 35 cm OTA circumference: 114 cm OTA length: 144 cm "Parked" position height: 160cm Total weight: A lot! (cca 40 kg) Optics The heart of this puny thing is a parabolic primary mirror of 305 mm diameter (12”). It is actually pretty funny because the secondary mirror is therefore roughly the same size as the primary in my Firstscope 76 – this thought always makes me giggle. Well I know that there are plenty of you using larger scopes than 12” and those of you who do have my sincerest admiration, but I reckon 12” is the practical limit for me and probably always will be. Anyway, the primary has a focal length of 1500 mm, which means that even though it is an F/5 scope, its OTA is quite big, being some 140cm in length. The secondary mirror is held in place with a four-vane spider assembly, which allows you to adjust its position in all four directions to make it as dead centre as possible. I have also heard that it is best to have the vanes tightened like a string, but I am not sure about advantages of this one. When observing bright objects or stars, you get the traditional diffraction spikes, as expected. You can adjust the secondary in all ways and direction imaginable, but the great thing is that once you do it properly (so that, say, a laser beam from a laser collimator is spot on the primary centre spot), it does not move at all, even when you treat the scope roughly, so you might not need to adjust the secondary for quite some time, which is quite good, given the size of the secondary mirror. The primary mirror, being as heavy as it is, does not hold its collimation that well so tweaking it once in a while (I check it every time I head out) might be good. I should note that the primary mirror cell has pre-prepared holes for one 80x80mm fan in the back, for mirror cooling, which I think is handy, and easily exploitable. One thing that might present a problem is that it’s F/5 scope, meaning that it’s quite demanding on the eyepieces. Me, personally, I am not a perfectionist, so somewhat blurry stars on the edges of the field of view don’t bother me, but I can see how that might be a problem for some people. Anyway, there is not really much you can do about, except for whining about it, or buying an eyepiece that almost matches the price of the entire telescope. Take your pick. The focuser is a classical Crayford 2” focuser, which I think works quite well - you can adjust the tilt of it, and it is really firm and solid, even when you use pile up optical elements on top of one another. I bet there are better focusers for the job, but for me, using the scope purely visually, it works a treat. You can even fit it with a standard Synta motorized focuser, which makes the pin-point precise focusing (on planetary and Lunar observing) even easier. OTA The OTA is made of metal, and pretty much all of the OTA (primary mirror cell, focuser, etc.) are made of metal as well. Only thing made of plastic that I can think of are the two barrels supporting the OTA as it sits on the mount, and they are the weak spots of this scope’s build quality. The plastic parts touch the metal tube, which results in occasional squeak and creak now and then, which can get really annoying. Apart from that, it is all quite pleasantly well made. Of course, when considering the OTA’s shape and size, it all rather resembles a large dustbin; this means that every knock on the OTA gets amplified and it all sounds a bit too hollow, or tubby, which on one hand does not really feel assuring regarding the scopes build quality, but on the other, it is a great tool for scaring away stray wildlife at night - you just knock on the OTA and they are gone. I am given to understand that wildlife is scared by unnatural sounds, so this one fits the bill nicely. The finder scope is located in quite a convenient place, but I can’t really comment on using the default straight-through finder, because I have immediately replaced it with an RA finder (same spec), but I can see that using the default finder may get a bit awkward when you try locating something near the zenith; there is no problem with my RA finder in this area. Furthermore, the size of the OTA leaves you enough room for additional accessory to be mounted on - I myself have mounted a red-dot finder on it, as seen in the pictures, but there will definitely be no issue in trying to fit something like a Telrad or Rigel finder to it, or, indeed, using a small refractor for a finder (but you have to keep an eye on the OTA’s balance. Furthermore, the default matt black paint with which the inside of the OTA is painted, is really not bad, but I have taken the liberty of flocking it already link here: ) - I actually don’t believe it helps a great deal, but it is good to be able to exploit the performance capabilities of the optical system to the limit, and flocking can’t do any bad. Naturally, the OTA itself functions as a “bulletproof” dew shield for the primary, but surprisingly, you can get the secondary dewed up - it happened to me once, it was really unexpected, even despite the heavy dew-fall, and when this happens, all you can do is pack you stuff and call it a night. One thing that really bothers me though is the dust cover for the OTA - when it’s cold outside (and it usually is), it probably shrinks which means that when you pack your things and head home, the cover keeps falling off of the OTA, which is really annoying. Dobsonian Mount The OTA sits on a dobsonian mount - very basic, totally functional. It is made of chipboard material, and when I built it together, I was worried about it swelling up from water, so I glued all parts together, leaving no slit uncovered for water (dew to be precise) to get in it. What was surprising for me was that despite the fact the online description said the mount would come with Teflon pads, it came with roller bearing instead (for azimuth axis). It was quite a pleasant surprise, thought I reckon there was a mistake in the description in the first place. The OTA is cradled on four plastic knobs, two on each side, which works quite well, although sometimes, the resulting movement in the altitude axis stammers a bit - I have seen some DIY modifications, where people replaced the knobs with ball bearings, and I think it might be worthwhile, but for now, I will go with the default setup. There is even a shelf for your eyepiece with holes in them (three for 1.25” and one for 2” eyepieces), which seems nice, but for me, it is in a rather awkward position. Once the warranty is void, I can feel modifications coming, primarily in the mount area. Transporting it The OTA sits on a dobsonian type mount, which is made from chipboard, and there are only two hand screws (functioning as tension screws) that hold the thing together. So when you remove the screws, you can move the OTA and the mount separately. It is good to grab the OTA by the primary mirror cell at the bottom with one hand and support it at least 2/3 of the way up with another – that way, you have quite a good firm grip of the thing. Only thing you really need to be careful about then are doors (for obvious reasons). When I head out observing by car, I usually load the OTA first. Now with our Megane estate, it is not a big deal – I just fold one of the back seats down, and lay the OTA in gently through the boot, and eventually secure it in place with a seat belt. Initially, I was worried about scratching the thing when moving it so I wrapped it in a bed sheet, but it has proven unnecessary, and even dangerous that it might slip out of the sheet. When I transport the thing by a small hatchback (Clio), the things get a bit tricky – I have to fold down the front passenger seat and remove the rear seat to let it fold flat. Then I place the OTA on the front passenger seat and secure it with a seatbelt. I think that you can see the catch at this point – no company when observing; and, it is useless to try and load the OTA transversely, because it would not fit (unless you have a Hummer or something). So I can see that transporting the scope with a small hatchback can indeed be very tricky, but I can manage it (I even think it is easier to load it in a small hatchback anyway, but that is just my point of view). Once the OTA is in, I load the mount in the boot – there is no problem with the estate car, but hatchback struggles, and I have to put it in horizontally - it is like solving the Hedgehog in the Cage puzzle. Operating it For some, the mere dobsonian mount the scope sits on can be a limiting factor, but I think that the very essence of the mount makes the scope amazingly easy to use. Of course that being only Alt-Az type mount operated only manually, you are limited to visual observations only, or occasionally, some webcam planetary astrophotography (but even that is hard enough with high magnifications). However, I as yet have no tendencies to step into the astrophotography area (because I don’t want to bankrupt myself), so for me, the combination of large scope on a dobsonian mount is ideal. You can set up the telescope, despite its size, in less than 3 minutes I’ve checked), even when you are on your own. Of course you stretch your back a bit, but at least it’s quick and very simple. From then on, it is just simple point-and-shoot principle, which I think is fabulous. All you need is to get accustomed to the whole flipped image idea, and anyone can enjoy himself. I once invited a friend over for some observing, who has never seen a telescope of any sort up close - he was able to observe Jupiter and follow it on his own in 10 minutes or so. This just proves it large scope/dobsonian mount is a really foolproof concept, even though it’s purely for visual use. Observing with it As you might have guess, the scope’s primary area of use is DSOs, and I have to confirm that it performs really well. I can finally dive into observing dim and small galaxies and galaxy clusters, and I can finally see some famous objects like the Stephan’s Quintet or the Veil Nebula. As you might expect, objects like Orion nebula look fantastic, and I can even see some nebulosity around the Seven Sisters in Pleiades. The dust bands of the Andromeda Galaxy pop out miraculously, and I am able to resolve individual stars in every globular cluster I have tried so far. Furthermore, the bright image enhances the colour experience, which means that when for example observing open star clusters, their different colours become apparent. Sometimes, I just try and sweep the sky randomly, and there are blobs and fuzzy patches appearing in the eyepiece all the time. The sky never looked so full to me! Planetary nebulae and larger galaxies finally show some internal structures, and with the image being so bright, observing planets with high magnifications delivers really good contrast. There is no point in going into details, but a list of some of my observing reports is below: http://stargazerslounge.com/topic/150839-yet-another-unexpected-session/ http://stargazerslounge.com/topic/150457-unexpected-session/ http://stargazerslounge.com/topic/150127-surrounded-by-forrest-19th-may-2012/ http://stargazerslounge.com/topic/139441-at-last-a-full-on-session-with-my-12/ Upsides Good on DSOs Great on DSOs Again great on DSOs Dobsonian mount is easy to use Great value for money Quick and easy to set up Good Crayford focuser Decent stock finder scope (8x50) Bracket for 80x80 fan Mostly comfortable viewing positions Downsides Big and heavy Big Heavy Hard to transport, takes up a lot of room Occasionally squeaking Manual movements only Alt-az only Visual only Hard-to-reach EP shelf Secondary mirror can dew up Dust cover keeps falling off of the OTA