rl

Chromatic aberration is not the only issue with cheap short-focus crown/flint refractors. A lot of them suffer significant amounts of spherical aberration as well, and the field curvature might be a lot less predictable/ correctable. Alacant's suggestion with a Wratten #8 is worth a punt but that's about as far as I'd go. A least from the theoretical point of view, your Newt is a known quantity...any coma corrector to suit the f-ratio should be giving very acceptable results out of the box assuming the spacing is correct. We are taking it as read that you are looking to do deep-sky work here..I don't think it makes it clear in the initial post. A decent long-focus achromat is capable of very reasonable results on planets/ moon with nothing more than a cheap UV/IR filter. Are there any other ways you could optimise your results from the newt, at minimal expense? Are you using a Bahtinov mask to focus? Is the CC spacing optimised? Would a cheap LPR filter help? Processing? If you're determined to go the refractor route, the old blue Skywatcher ED80s often change hands for about £200 secondhand...mine did! They are a very good start, if a bit slow. The focal reducer is a very worthwhile addition. I've been doing astrophotography for 40 years and I'm still amazed at my own talent to mess it up completely either by clumsiness or forgetfulness. Given the infrequent good nights, anything that makes the data aquisition simpler and more reliable has to be a good thing. A small ED frac can be a big step in this direction providing it suits your chosen targets (wide field); easier to mount (half the weight, half the focal length, less than half the wind sail area), don't go out of collimation. They are about the closest thing in astronomy to kit which "just works". It might be worth saving up....optimise the return on those precious hours spent outside. RL

I can fully relate to the op's comments....lost track of the number of times I've packed up the AP kit on a good night after achieving nothing due to some minor procedural oversight. The sheer simplicity of kit without wires or batteries is an underestimated pleasure too often forgotten.

I have 3 scopes currently in my posession made by OO 150mm f/6 1/10 wave 200mm f/4.5 carbon fibre 1/12 wave (special order to request). Possibly the best all-rounder (for my circumstances) I have ever owned, any type of scope. 300mm f/3.8 carbon fibre astrograph 1/10 wave I bought the first two new and both were delivered on schedule. The only fault was a brass compression ring missing on a 2" extender. Optically all are as good as can possibly be expected from a Newtonian. All have test certificates, the validity of which I have never had question to doubt. I too have heard the stories; indeed, I bought an early Maksutov 140mm off them in 2000 and it was never right even after repeated returns to the factory. After several years of unsatisfied ownership I ended up giving it away to a school. But a lot seems to have improved since they got the Zygo tester; before that they could be a very hit and miss. Basically it's a small company with a large order book and sometimes things go wrong..that's never an excuse for poor customer service but I run a small business myself so have some small degree of sympathy when outside factors interfere! There are a lot of people who can get quite vocal over long delays or other issues, but the satisfied customers will be a silent majority wondering what all the fuss was about. But if you're the one waiting for months on end I'm sure it can be really frustrating....it's a risk. You can't really go wrong taking the Skywatcher route; they make more before breakfast then OO do in a year so they must be doing a lot right. I've owned skywatchers aplenty and always been happy with them (but curiously enough I've always been happier with their refractors). OO probably do make better mirrors but I would concede that whether the difference is important is questionable under uk skies. Nine nights out of ten the sky limits the resolution to one arcsecond at best, so you can argue that any scope over 6" meeting the Rayleigh criterion will show you all there is to see in terms of detail if not brightness. Personally I take a different view and would rather be best equipped with my main scope for that tenth night, or even the fleeting moments of half-arcsecond seeing on an average night. The real point of a mirror with 99.5% Strehl is that the scope as a whole will make 80% after the secondary has done its worst with diffraction effects. OO have been around for over 30 years now which probably says something in itself. Not sure if this helps, but it's one man's experience over many years with them. RL

John... As far as I am aware these were made as f/9 or f/10 only but I'm prepared to be wrong on this one. At f/15 a doublet would be pretty much colour-free making the extra cost and effort pointless. I'm just amazed at just how well it works..it seems to do everything a decent 6" frac is supposed to do. RL

Thanks all for the encouraging feedback guys...there's a couple of other slightly unusual items I might review in due course. RL

A review I've been meaning to finish for some time....word file uploaded. John_Owen_6 inch_refractor.docx

The narrow end of the baffle will just cover the secondary mirror. I expect you will see the remains of the glue as a guide. It should be concentric.

What has dropped off is the light baffle around the secondary..the important part (the secondary mirror) is the silvered spot on the back face of the meniscus. It was presumably glued on. The baffle has fallen on to the primary...hopefully it's too light and too soft to scratch the surface. The retaining ring for the meniscus should simply unscrew if you very carefully twist it using some pins/ nails in the 2 holes. You may have to make up a tool specially to move the ring; they can get tight with age and dust etc. 2 nails in a piece of wood with the right spacing will reduce the risk a lot. Spend some time preparing for this...it's worth an hour making up the tool and ensuring the OTA is firmly held without being bent. You should be able to simply remove the baffle and the scope will still work, but it will be prone to off-axis light getting in and spoiling contrast. If you're feeling brave then glue it back in place. Hopefully those on this site with Meade Mak experience. There's bound to be a special type of glue...there are those on this site much better qualifies on the exact details. When the job is done the retaining ring only needs to be nipped up not much more than finger tight. Good luck, RL Sorry, looks like everyone else types faster than me...a lot of responses for a clear night! RL

SGL have not seen fit to offer an "react" emoticon for envy...

"foggy, misty, or just plain raining" Is the clue in the OP's title notes? For 15 years my main scope was a 130mm f/10 Achro made by John Owen( still have it). It's by no means optically perfect..I would expect an ED120 to be better. Living in the centre of Birmingham, I found taking it to a decent dark site was the trick...I found all manner of DSOs with it under a dark sky. Would trying a filter help out on a lot of emission line DSOs? I find a UHC helps a lot in cities and a gentler Deep Sky helps a moderate to good sites.

I have just bought the CT8 version with a 1/12 wave mirror as a special (ordered at astrofest). I have yet to have a night good enough to allow any sort of objective assessment om Jupiter. However, looking at high altitude stars, the scope shows as good a set of diffraction patterns as I have ever seen in a Newtonian.....after I had loosened the mirror clips just a tad. It originally had toblerone -shaped Airy discs. The problem was obvious..the mirror is held in very well..perhaps too well..it is fixed in with top clips, radial adjusting screws, and lots of silicone goo just to make sure nothing comes loose. And a tape band binding the circumference of the mirror to the 3 mirror clips.... Collimation is of course critical, and it collimates easily. The 3 locking screws for the main mirror protrude so if you stand it on end there is a risk of disturbing the collimation, but that's obviously not an issue if it's kept on a mount. The only real optical fault is a caustic curve on very bright optics but, to be fair, I haven't found out whether it's down to the scope, the coma corrector or the eyepiece I was using at the time I noticed it. The scope innards look well and truly black with no exposed shiny bolts. The (far eastern origin) focuser is excellent. Normally I don't like Crayfords but this one really will hold a camera and a coma corrector without slipping. An d I haven't needed to adjust it so far. You can argue there is not much point in going for a very high spec mirror with a 30% obstruction; the Strehl for the whole instrument can't be much above 80% even if the mirror is 99.4% (this on is) but at least you will know the problems are going to be somewhere else and you are getting the best possible overall result. I bought it as a jack-of-all-trades instrument (accepting the master of none tag) to keep for 20 years and from what I have seen so far it will certainly live up to expectations. Not too small to be deep-sky useless and not too big to manhandle, and enough resolution for the sky to be the limiting factor 4 nights out of 5. Highly recommended, but be prepared to faff about with it to get it as you want. The short tube assembly is definetely an advantage. Vixen and Takahashi still make better made scopes but OO have come on leaps and bounds in the last 10 years. It's always open to question whether it's worth the premium over the equivalent SW but in my case I reckon it is. I'm pretty certain I'm getting the absolute best an 8" short Newt can reasonably be expected to do, and in a light but rigid package. I bought an AZ-EQ6-GT mount at the same time specifically for this scope and it seems like the perfect match for AP. The scope plus camera plus OAG, coma corrector etc comes to about half the mount's payload spec. It's all extremely stable even in a breeze. It's well suited to the ES 4 element coma corrector. RL

Mea culpa...Bought this at astrofest a few weeks ago, it's dangerous place!. I blagged a 1/12 wave mirror as part of the deal. Got the mount at the same time..The curse of the cumulostratus is probably down to me....

My AP rig... Looks good for tonight...Bring on the Virgo cluster1