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PhilipR - Thanks; good to know that Maks, etc, rarely need collimating. CONCLUSIONS. Many thanks to all those who have taken the time and trouble to help me to learn whether it's worth upgrading from my 90mm f8 refractor to a 150mm reflector, and also many related things. I'm trying to feed a little bit back in the hope it may be of use to others, but this is just opinion.. 1. Yes it is. 2. Upgrading to a 130mm is very marginal. 3. I'm asking too much; there is little on offer to suit my particular requirements. I'm being inflexible, but can't do anything about my house being built into the side of a hill, and some trees, with a very restricted outlook. 4. Be careful what I read - some of the articles written by "journalist and researcher" people can be inaccurate with specs, and all the telescopes reviewed are amazing, they say. This seems to apply to any topic, particularly anything technical. 5. I would need a new mount to accept modern dovetail fittings if buying a Skymax OTA. FLO tell me that the rings on the Sky-Watcher Explorer 130P-DS OTA will bolt onto the AZ3. 6. Some people think the AZ3 mount will work with a 150mm telescope, some do not. I don't want to take the risk. A 130mm would be OK on this mount. 6. If anything, the Sky-Watcher Explorer 130P-DS OTA on an AZ3 is the best choice. 7. There are some cheap used 130mm Newtonians on ebay, such as the Skywatcher Explorer 130M and the Celestron equivalent, but they tend to have spherical main mirrors with f ratios too short to avoid significant SA. 8. I would not buy a new telescope from ebay or Amazon unless an unusually good deal (then one would ask why). Better to buy from FLO or a similar quality dealer. 9. I'm thinking of continuing with the 90mm unless I move hom. One thing, the 90mm shows me the stuff I want to see but naturally is very poor on DSO's, it's just that a bigger telescope will do it all better.

F15Rules - Yours is the second post to suggest a127mm Mak. I'm getting lots of suggestionson what instrument to buy, including 150mm f5 Newtonians! On the basis of 30 to 35x diameter in inches of the main mirror, would such a telescope easily take a magnification of 150 to 170x? I prefer this criterion than the 2x diameter in mm one, which assumes really good optics and excellent seeing. I like 120x for my 90mm refractor because there's very little dimming for one thing. If I bought a Mak, I would be prepared to sacrifice better wide field performance, a little more light collection (but have lower CA in keeping my 90mm) and not buying the 102mm achro. This would keep me close to budget. Is it difficult to collimate Mak or Mak-Cass telescopes? Stu - I think the above post from F15Rules is in accord with what you said about telescopes complimenting each other in your first post!

cajen2 - Thing is I've been advised in two posts that the AZ3 would not work well with the 150mm Newtonian because of its weight and because the centre of gravity moves a lot because most of the weight is at one end. Yet apparently people have done something like this with a flextube150mm, mount unspecified. The 130p is a lot lighter and would be OK with my mount, but of insufficient aperture to give a good performance boost over my 90mm refractor. Some years ago I found an excellent article on tuning up an AZ3 mount. The author actually fitted a rod to the top of the mount with a sliding weight to counteract C of G movement for his Newtonian. I need to be certain that any rig I put together will be lightweight, stable and provide a significant performance boost over my trusty 90mm refractor. For some reason, I'm being as fussy about the possible purchase of a new telesscope as I might when buying a used car! My approach is to have the gear packed, scope pre-cooled, watch the weather carefully, then if clear at a moment's notice carry it to the site, set it up and go. Useful in our unstable climate. Catanonia - Indeed it's wonderful to receive such generous help! Mark - Thanks for the images. Alkaid - Thank you for your clear, helpful and detailed comparisons. I've never seen one of these dovetail mounts. Are threaded holes provided in telescope tubes to attach the dovetail, so it can be bolted on from outside the scope, essential with refractors and cats? Another question, adjustable parts, movements or possible flexing in any mechanical system can lead to inaccuracies and play. With only two rods in the flextube, does this ever result in loss of collimation? Is there any significant advantage of the flextube over the full-tube version except that the flextube takes less space in storage?

Cajen2 - Thanks for the suggestion. Some weight would be saved on the tube, but as it's at the top of the tube, the balance problem with nearly all the weight at one end would be more critical than with the full tube. Peter_D - Thanks for the advice, but I like manual operation, and any EQ mount including counterweight (and motor (s) plus battery) would be heavier than the AZ3. Simplicity is my thing. A Bresser 127/900 weighing in at 3.4Kg would be light enough, or the cheaper Sky-Watcher Skymax 127 OTA, but I prefer the bigger jump to a 150mm scope to get a good upgrade. Prior to my search for a new scope, I knew about the traditional ring mounts, but had never come across these dovetail mounts. They seem to be supplied with physically short scopes. For my AZ3 a mating part to receive the dovetail on the scope would have to be bought and fitted to my AZ3. Alternatively, I could remove the dovetail from the scope (if possible) and make an adaptor plate of some kind. If there are tapped holes in the telescope tube I could possibly bolt it straight to the mount without the dovetail.

vlaiv - Thanks for going into this in such detail. I think that different sources, and seemingly good ones, can give different specs for the same item. I have seen the AZ3 tripod offered for sale with an EQ 2 (or 3) head fitted with a 6"/150mm Newtonian. I think this is too much weight. I don't need EQ counterweights; I was just saying they are part of the tripod load if used as an EQ, such as on the telescope and mount just described. Your image is exactly the same as my mount, and the specs you give agree with a check I made. Better to get real knowledge from a forum rather than some gibberish from some jounalist who may have no experience of astronomy. I agree the mount will be better with the f5 version of the 6" Newt rather than the longer f8 version. Having said that, something like the 6" CC would be better. I have been advised a couple of times in this discussion that a f5 6" Newt may be difficult to use on the AZ3, and have decided not to try a Newt on this mount. The centre of gravity is near the mirror end and could cause instability in the mount, varying with elevation of the scope. With a physically short instrument such as a Cass, Mak or Mak-Cass 6", the C of G would be close to the centreline of the mount at all elevations, and there would be less than half the windage. nfotis - Thanks for your advice. I agree that for observing the Moon and Venus (phases only) that ambient light doesn't matter - it can help so the eye doesn't become too dark-adapted when viewing bright objects. As well as street lights, my house is built into a hill. There are 13 steep steps leading to the front door and the hill limits my view to between about WSW and NNW. Otherwise I can't get lower than about 50 to 75 degrees above the horizon. I'm taking your advice on not using a 6" Newt on the AZ3, you're not alone in thinking this. A Skymax 150 at 5.6Kg, although a bit heavier than the Newtonian at 5.0Kg, would be more stable on an AZ3. CONCLUSION. I'm grateful for the high quality advice received, and for what I've been taught. It seems that I have been saved from buying a telescope which would not work well with my AZ3 mount. The best option would be for me to buy a physically short OTA such as a Cass, Mak or Mak-Cass 6",but these telescopes are beyond my price range. A search for used scopes from FLO, other dealers and ebay suggests that there are a lot of Newtonians on Dob or EQ mounts for sale, but almost no physically short OTA's. A possibility would be to buy a used telescope with mount and use the AZ3. Anyway, this is now all on me. Spend the money, or not. For the forseeable future, I plan to stick with my 90mm f10 refractor and AZ3 mount. Interestingly, this (and accessories purchased separately) suited me very well when I bought it, and still suits me very well.

Thank you for being so helpful in your replies. I can't figure out how to reply to people individually, so am answering the four preceding posts in this single post. Thank you also for your kind welcome. Stu- thanks, the complimenting of scopes is an interesting idea. Zermelo - Thanks for the thought-provoking links. The one on what you see through 4 to 8" telescopes, with hints on observing, was particularly helpful. I have done web searches, including Youtube, and haven't found a clear article or video on my particular query. It would be easier if I was buying my first telescope. Mike - Thank you for your clear response. Your kit is in a different league to mine! rl - Thanks for your helpful comments; yes, I need to be very focussed on weight. I've looked into the need for collimation. Apparently it can be done simply with just an eyepiece holder with a pinhole in it, and acentre mark on the main mirror, but a light source is needed. This is a slight reservation with Newtonians, as I'm reluctant to make adjustments to an optical instrument in a dark field. I'll look into OO scopes. Vlaiv - Thanks for your detailed reply. My budget is total £350 for a 6"/ 150mm reflector OTA and £650 for a super lightweight 8"/ 200mm reflector OTA (which doesn't seem to exist). What I mean by using low power is that my favourite magnification for my 90mm refractor is 120X . Using the theoretical maximum magnification with this telescope of 180x degrades the image. For me, 120x for the 90mm is a "sweet spot"; it's easy to use and seems to bring the best out of the telescope. For a 6" I would go up to 160x to 200x. Much above this, seeing needs to be very good anyway. I don't plan to do imaging or specialised wide-field observation. The AZ3 tripod has a specified load of about 10 to12Kg. With the f5 150mm 6" Newtonian at 5Kg plus EQ mount counterweights weighing maybe 2 to 4Kg the AZ3 may not handle it, but I'm using the far lighter ALT AZ head. For me the total load is about 6Kg.

I'm a very casual observer and have a Skywatcher 90mm f10 refractor on an AZ3 ALT AZ mount, and would like a bigger telescope (but want to keep the 90mm refractor). I need to be able to carry the telescope and mount for 1/2 mile in one load, and I'm a pensioner. Using a rucksack for mount and accessories and carrying the telescope in my arms works for the refractor. The trip can't be done by car, and a wheelbarrow or dolly would be a liability. Observing from home is not an option. A 200mm would be ideal, and I like the Skywatcher f5 Explorer OTA, and its price, but at 8.8Kg is too heavy. The Skywatcher f5 Explorer 150mm OTA is a lot better at 5Kg, about the maximum weight for me. I considered the Skywatcher Skymax 127mm Mak OTA, but the aperture is smaller than I would like. Where magnification is concerned, I prefer to err on the low side; even at the risk of missing out on the finest detail at times. It's more relaxing, the image is clearer and there's less shake. I'm looking for a BIG difference, and as far as I can gather upgrading from my 90mm to a 150mm f5 Newtonian would be very broadly equivalent to upgrading from a 90mm refractor to a 115mm refractor, which to my mind is probably not worth the money or time. Having said that, excluding secondary mirror and spider loss, the 150mm Newtonian has about 2 1/2 times the light gathering capability as the 90mm refractor. I like using the AZ3 mount, and want to continue using it, and it's only about 3.7Kg weight. It's probably a bit like using a Dob (too heavy for me) but with easy to use slow motion controls. The maximum rated total load for the AZ3 tripod is 10 to 12Kg. My main interest is in the Moon and more accessible planets. Even the "easier" DSO's are a a bit of a struggle and are unimpressive with the 90mm, but might try for the more accessible DSO's with a bigger telescope even though this won't produce miracles. The bottom line is, is there much point for a casual observer in upgrading from a mid-priced 90mm refractor to an f5 150mm Newtonian (an f 6 or f7 would be preferable but more bulky and a bit more heavy)? The cost is about £225 for the 150mm OTA, a good 8 or 9mm eyepiece would cost about £50 and a ND Moon filter about £10, with about £12 delivery. This is driving me potty, please advise.