ollypenrice

F7? That's not.... Olly

I think that in this case and in many others there is an interaction between the buyer and the seller in which the seller anticipates what the buyer wants (in this case small fast refractors at less than half Tak price) and tries to deliver it. Inevitably competition between manufacturers means that they don't want to be the ones to say they can't do it, they all want to be the ones who say they can do it. So they push to the very limits of what they can do, they get some prototypes to work, and they go into production. This interaction is 'policed' by the laws of consumer protection. If they say the scope can do it, it must do it or the sale can be recinded under the law. This system is working, but it strikes me that it is creaking as a system since customers like you are being put through endless faffing about which, in the end, will not be recompensed. Nobody will pay you for your time. My contention is that it would be better all round for the consumer to demand a little less and the manufacturer to promise a little less by either charging a little more or easing off on the spec or both. If this were a defence procurement contract and you were dealing with the manufacturer to decide price and spec I strongly suspect that you'd pitch in for a slightly slower F ratio and - quite possibly - a slightly higher price. The free market is not a procurement contract, it's an environment in which manufacturers are tempted to promise the impossible. I've said this before but I think the purchasing community should start to make it a bit clearer to manufacturers that we only want products which work. I can guess that they might come back with, 'Yes, but you won't buy them if we make them, you'll buy the ones our rivals fail to make reliably...' Olly

I always feel it's sad to think that the cheap Chinese import might put a guy like David Lukehurst into difficulty but it seems it's very much the other way round. Great review, very honest. For all its faults, and even though I'd go for a Lukehurst myself, I expect you'll get some great nights out with this when you've sorted it out. The dust lanes in M31 are, as Peter said, off centre and are very distinctive from a dark site and with the galaxy near the zenith. The elevation makes a big difference. Olly

Shoot me down in flames by all means but I see no reason to believe that the manufacturers know how to mass produce these small fast refractors with an acceptable probability of their working to spec. We have moved from the consistent successes of the stalwart ED80 (F7.5/F6) to thread after thread of dodgy corners and distorted stars. Is it not time to ease up on the flashy numbers and settle for something more like F6? I'm not a fan of extreme optics because I like optics to work. Lord knows, the IT side of the imaging business gives plenty of opportunity for random failure. At least optics can in principle be perfectly reliable, night after night, if you don't ask for more than the makers are competent to deliver. I could live with F6 and I believe the mid-price manufacturers know how to do that. It's a bit like houses. The developers want to be able to put '4 bedrooms and garage' on the description so you end up with garages in which you can't open your car door and bedrooms in which you can't fit a bed. I counsel F6! Olly

This is a beautiful job. Are you a professional in the machine shop? Welding stainless isn't for everyone. It does give the whole thing some real class. (I am probably the worst amateur welder in Europe. ) We have a 20 inch F4. It's such a nice size, big but not ridiculous and not too terrifying at the zenith. Olly

This seems like a good idea. It arises from an honest look at the reality of the present situation. The manufacturers are underpricing and failing to achieve the QC their designs deserve. We can argue about whether that's their fault or our fault or we can give FLO's idea a chance. If I were in the market for one of the scopes in question I would, without any hesitation, give this deal a try. Olly

That is a good and thorough review. I'd call F4.4 more than 'reasonably fast' for a refractor, I'd call it screamingly fast! Not many refractors go inside F5, after all, and doing so is never going to be easy for a maufacturer either optically or mechanically. I hope the fine tuning of tilt and chip distance go well and that you'll be back with more. Olly

I'm slightly wary of asking this - but what's 'insertion rubber?' How about having one plywood sheet with layers of rubber on both sides and one with a handle as per Shan's suggestion. Place the double sided one on a worktop, lay the offending rings on it and press the other one down turning with the handle. Come on FLO, this is right up your street! Olly

Floor matting of some kind? It will just be a matter of seeing what's around in the hardware stores/supermarkets. It needs not to be too heavily ribbed. Olly

"Ah, Mr Einstein, I wish to sublmt a patent for a piece of rubber glued to a piece of wood." Olly

I think I'll try a refinement of the trainer soles technique which has the virtue of not distorting the rings at all. I'll try to find some kind of strong rubber mat and cut out two squares which I'll bond onto plywood sheets. These will replace the trainers. The stuck adapter menace strikes visiting astronomers very regularly and the resident one from time to time as well! A definitive solution would be nice to find. Olly

But then what would I do? Hold a normal bubble level next to them? I can do this by holding a normal level against the Atik sitcker which is aligned with the chip but it's a fiddle and only fairly accurate. I'm hoping this will be easier, and won't require me to find my bubble level each time. I mean, I'm a bloke. I can never find anything!! Marking the FW against the draw tube won't work because you sometimes take the camera off it and it won't necessarily go back in the same orientation. Sure, I'm not expecting perfection, just a hand to get close. If the target needs perfect alignment (because it nearly fills the chips) then I'll refine it the usual way. If one or both of these cheapo levels is not at right angles to the other then either the idea won't work or I'll get to remember how far off centre a particular bubble needs to be, and in which direction. I might even write it down on a piece of paper and lose it... It does occur to me that a classic engineering track rod could be used between cameras to oblige them to rotate together but you'd need to pull out all the cables for it to work. An idea too far, perhaps! Olly

That has some great numbers going for it, particularly the possible FOV which would make it a cracker for things like the Veil, Rosette, etc. The price strikes me as more than reasonable, too. Very nice indeed and with that excellent red colour thrown in as a bonus! Olly

I've just this minute ordered some mini 2 way self adhesive bubble levels intended for caravans and camping cars. I'm going to get my cameras perfectly orientated either in landscape or portrait using the star trail method, then set the counterweight arm and OTAs to horizontal and stick them on the backs of the CCDs. I use a dual scope fast imaging rig and this should allow me to switch between landscape and portrait on both very quickly and fairly accurately. I'll report back on how well this works. Olly

Here's where you are, courtesy of Registar. I always think it best to have a camera orientated along RA and Dec, either in portrait or landscape, unless there is a good reason not to do so. It makes life easier in many ways. It is easy to do so. Just take a short exposure while slewing slowly. The camera angle is shown by the angle of the star trails. Olly

Can you tell us something about autoguiding in de-rotated alt-az mode? The only professional scope I know from experience is direct drive and so 'encoder guided.' This is hardly the thrust of the thread but I'm interested. I know that there are still plenty of professional EQs but are many being built these days? I thought alt az and de-rotator had become the norm. Olly

We'll have to disagree amicably on that. You think the alt az mount is the right mount for AP and I don't. This doesn't mean we have to duel to the death with loaded pistols. (I hope. I don't have one!) Olly

Yes, the need for counterweights is the big GEM palaver.

Again, I agree. In truth Alt Az and equatorial mounts overlap in price so I don't think it's so much about the net cost as what you can do if what you have is an at az mount and don't want the bother or expense of changing. One of my biggest astronoomical regrets is firstly buying a wedge for, and then de-forking, my Meade SCT. As an Alt Az scope for visual observing it was fabulous, with a convenient EP position almost all over the sky and no flip. I heartily wish I had just left it alone. Olly

You are quite right and that is why I didn't say that. The thread demonstrates very well that it can be done with an Alt Az mount. Olly

I wouldn't dream of doing so and don't believe anything I've said should be taken as divisive. If it seems that way then I apologise. If the technology you predict comes to be then, wallet willing, I'll be in there! Olly

Well, we'll go round in circles if we're not careful. In astrohotography we use long exposures. Long exposures need to be made while tracking the sky across the whole image. Only an EQ mount can do this at amateur level. An Alt Az can only track in the centre. This is not a value judgement such as stating when reflectors become too small. It is a hard fact. You're perfectly right about the professionals using alt-az but they use alt-az with derotators. (Way back in this thread I jokingly referred to one I've used.) The prfessionals don't autoguide, though. They use direct drive mounts reading absolute encoders. I know of no way of autoguiding a deroataed alt az, though Meade used to list a derotator at one time. I'm a huge fan of alt az for visual and detest EQs for this purpose. Anyway the people positng on this thread have done wonders and I don't want to come across as saying anything else! Olly

I would never say that. Formula one is a heap of moneymaking rubbish. I was a kart racer and racing cyclist. I thought the cycle racing was best of all. Quite right, and I wouldn't suggest for a moment that you did. I think there is a right and a wrong mount. A mount which tracks the sky without rotation is the right mount and one which doesn't is the wrong mount. I repeat, I like this thread but I think it should be a thread about what can be done with an alt-az mount. It should not turn into a thread pretending that an alt-az mount is the right mount. Olly

I like this thread, as I've already said, and I like your images. However, I'm not able to accept the phrase, 'The so-called wrong equipment.' It IS the wrong equipment. The right equipment for DS imaging is the equatorial mount. I think it's important to bear in mind that beginners will be drawn to this thread. For me this is an excellent thread about what can be done with what is, no bones about it, the wrong equipment. Olly

Photoshop?