ollypenrice

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?

GoTo works perfectly if the mount isn't level. Witness Takahashi mounts which cannot be levelled. My Tak Go To is first class. You can have a Tak mount polar aligned before a regular mount user has got the tripod level. That is literally true. My point wasn't about the speed of levelling, though, and Steve's right that it is better to level a mobile (non Tak) mount because of the interaction between azimuth and altitude drift iterations. My intention was to comment on a fixed observatory pier, the OP's topic, in which many designs compromise rigidity in order to offer levelling which is simply not needed. In a pier you want rigity. The real pests are the manufacturers who design mounts to be secured onto tripods or piers from below. For piers this pointlessly introduces the need for some form of access, so we get into ratboxes and owls nests and all sorts of silliness. Nowadays most manufacturers have woken up to this. Avalon, Mesu, iOptron, 10 Micron and many others now have systems which require no central access from below. Hooray!! Olly

Dec isn't level. If Dec is level you'll be looking at the horizon! Olly

This is a vexed question and is flirting with the dreaded F ratio myth. But firstly the only form of binning possible here is software binning because we cannot bin a one shot colour camera. Whether or not focal reducers 'speed up' capture depends on what part of the image interests you because what they clearly don't do is bring in any new photons from an object which fits on the chip without reducer. Viz; In my opinion you might just as well crop and software bin in the scenario above as use a focal reducer. If you downsize the native FL image the information it contains is concentrated onto fewer screen pixels and the image will look less noisy. This is why, when you stretch an image, you must always keep checking it at 1 to 1 because when software binned (downsized to fit the screen) the noise won't show. If you decide to present an image at 50% of full size you need far less data than if you want it to hold up at full size. I see no advantage here in using a focal reducer. Where a focal reducer really does bring in useful new photons is where it brings into the frame something you want to see; In this scenario you have useful light from NGC1977. The light from the empty sky around M33 was not useful. Of course the pixels 'fill' faster with a FR and the widefield M42/NGC1977 will reach an acceptable S/N ratio faster than the M42-only image on the left. But if you gave both images the same exposure time and then cropped out M42 from the right hand image it would be no better than the M42-only from the left reduced to the same screen size. Such is may take on all this, anyway. Olly

I know it can be odd at first but this isn't really hard to grasp. What does Polar aligned mean? It means that the mount's RA axis is parallel with the earth's axis of rotation. So if, in imagination, you took out your polarscope once the mount was aligned and fitted a steel shaft through the middle of it, fixed at each end to your observatory, it would then be impossible for your polar alignment to be imperfect. (It would get in the way of the scope but we're just thinking aloud here.) So now your mount has a steel shaft through its RA axis and cannot be moved by any means from perfect alignment. Now unbolt the pier from the floor and loosen the polar alignment bolts. In fact throw them away!! You can now tilt the pier forwards, backwards and sideways and the PA remains perfect. So there is no relationship between the angle of the pier and the PA. The main reason for levelling is simply to set the 'clock' in the polarscope reticle to vertical. (On Taks, with their potentially tilted tripods, you do this by means of a bubble level on the RA housing.) The other reason is that, in doing drift alignments, there is less interaction between drift tests in the south and then in the east or west. Maybe this is what Alignmaster didn't like when the mount wasn't level. My real point is that in an observatory mount there is no need to compromise a pier's rigidity by making it highly adjustable. Better rigid than adjustable if you can't have both. Olly

It would have to be quite a steep hill, in reality. This is actually metioned in the manual. And if Tak users live too far north for the rather limited adjustment in altitude they routinely put something under a foot to tip the tripod. By the way, I don't see how Alignmaster could have any knowledge at all of how the altitude angle was acheived (whether by tilting the pier/tripod or using the adjusters. The result is identical. Rather intelligently the levelling bubble on Avalons only runs east west, it isn't a circular bubble level.) Olly