ollypenrice

Cheers, Steve, so now I'm wondering whether that argues against flexure on the grounds that most of the correcting applies to RA. On the other hand a flex in Dec would throw up a spurious command. Perhaps it doesn't tell us anything. I might be thinking about tilt again, though. Olly

Do we know the RA-Dec orientation of the elongation? Olly

Yes. I used a Baader saddle bolted onto the clamshell. Then both my solarscope and guidescope, on Vixen rails, could be swapped easily for each other. The system also allows easy fine tuning of Dec balance by sliding the guidescope fore and aft. Olly

Thanks Hawksmoor, that's very kind of you. We're glad you enjoyed it. We certainly did! Olly

I honestly don't remember a tilt adjuster module on mine. I'm not at all sure that I had one, but Tak do change things around with their hardware. I certainly never used it since I didn't know about it. Well, it looks as if nobody likes that guidescope carrier and, on single scope setups, I've never had any issues arise from approximate alignment of guidescope and imaging scope. While I like and use (two) ST80s for guiding there are a couple of things to watch, though I doubt you've missed them. The entire rear end of the scope is held into the main tube by three screws. These need to be very tight. I wouldn't baulk at a drop of epoxy to hold the back end in firmly, either. I did have the back end cause flexure once. The drawtube is also very vague so I tighten the lockscrew rather pitilessly to keep it still. Any extensions carrying the guide camera also need careful attention. Olly

OK so bin my suggestion about PA if the guide scope is on axis. I have to say that I never like adjustable guide scope holders or rings* and always prefer a bolted-down guide scope even if it isn't perfectly on-axis. With good PA this won't matter. That adjuster has to be a suspect, though it may be perfectly innocent. I guess the orthogonality of your filters could play a role but does changing filter change the distortion? If not it's highly unlikely to be that. (You'd have done well to replicate the same tilt in every filter...) Olly *Except in the case of dual rigs where, on two occasions, we've found the system prefers an on-axis guide star. I can't account for this. It could be experimental error but it happend twice so I just accepted the fact. PS, I found the Tak and reducer to be a stunning combination and Sara always runs the reducer, I believe, so I wouldn't be put off it too easily.

If the guide star were well off-axis relative to the Tak then wouldn't polar misalignment also produce this effect? Which connector is that, Steve? Since mine departed some years ago I can't remember it in every detail but the only connector to give me gyp was the tilt-adjuster (if that's what it was meant to be) on the reducer. Steve (Gnomus), are you using the reducer here? If you are then the 'three radial screw horror' is designed to test your tilt adjusting skills! I just loosened the screws, put the flattener on the table, pressed the top part down onto the bottom and tightened them. That worked in my case. Steve. (Just going with the flow - or should that be FLO? )

I think you're pixel peeping, which has its virtures but should be kept in its place. If you look at Tak FSQ images you see a lot of excellent ones. You also see plenty of stellar artefacts. I get the odd PM or email asking if I've noticed this or that that is wrong with my stars and do I mind? I have noticed and I don't mind. Here's an example. Have a look at the bright young blue stars on the left. They have classic Tak 'inverse light house beams' coming from either side. Greg Parker tells me that they arise from pinching. He knows more about optics than I do so I'll settle for that. https://ollypenrice.smugmug.com/Other/Best-of-Les-Granges/i-Vtk6nfM/0/O/VDB152%20HaOIIILRGB27Hrs.jpg But what interests me in this image is that the Tak has allowed me to catch more of the red SN remnant than I have ever seen before on the net. That doesn't mean nobody has gone deeper, it just means that I haven't seen it (and, yes, the processing is exaggerated but that was my intention - to drag it into view via colour.) So my advice - and my own policy - is not to let the details blind me to the big picture. Anyway I'm still backing PA... but it could be tilt. The standard test for tilt is to rotate the camera. Olly

Firstly (call me sloppy) I'd be pretty happy with that and be inclinded to get on with some nice processing! I can't see anything to complain about other than in the top two and, of those, the top left is slightly worse. If part of the image is OK it can't be tracking, so that's ruled out. That leaves tilt and polar alignment. My guess is tha latter. The effects of polar misalignment will vary with the relationship between the position of the guide star and the centre of the chip. The only test of PA in which I believe implicitly is drift. Olly

And I'm saying almost nothing... lly

I don't know, I'm afraid. I wasn't able to get there because we're very busy and Monique's back isn't making life easy for her at the moment. This image can, though, hold up in print form at a size neither Tom nor I have so far seen - almost 8 metres high. This is really the whole point of the image so, in a competion like the one in question, it doesn't do its thing. We now need to see if anyone would like a big one! Olly

That's a really great write up. I'm a bit surpised that with such a lifting capacity the lock screw is needed. I've never encountered a lock screw which didn't slightly (or less than slightly) affect fine focus but there's always a first time. WIth an R and P I think there's no danger in running the lock screw just partially when going for the last focus but would this be OK on a Crayford? Not sure. The old style Steeltrack we used on Yves 14 inch actually did very well. It was motorized and belt driven. Olly

For question 1 you'd also need to factor in the angle of the panel relative to the sun because the insolation varies as the angle of incidence changes. I suppose you could assume a multi-panel array with each panel equatorially mounted to track the sun. Olly

It's certainly true that the processing priorities in L are entirely different from those in RGB so processing them separately is a good idea. In RGB you aim for low noise, especially low colour noise, and strong colour saturation, but there is no need for detail. In L you're looking for the faint stuff, the detail and the contrast. Obtrusive noise reduction won't do much damage to RGB but it will certainly harm L. In LRGB you can extract a synthetic L layer from the RGB and blend it with the real lum layer, too. I find it's worth about 25% of real lum per unit exposure time, so 4 hours' synthetic lum equals one hour of real - on my setups. This won't work if your RGB was binned because it will lack the resolution to be useful. Olly

Indeed, and why not? If you go into Lab colour space and apply an insane blur to a and b channels then recombine you will see hardly any (or no) loss of resolution. Essentially it's the same thing, and also explains why you can bin colour. Olly

Yes, but there's more. At each partial iteration of luminance over colour you can slightly blur the luminance layer to reduce noise. Flatten it onto the RGB and re-apply the lum at higher opacity and, again boost RGB saturation and give L a slight blur. It is at the last application of Lum, ideally at 100% opacity, that you no longer apply the slight blur and so you restore the full resolution of the L. If you don't apply the slight blur between iterations I can't see what you gain from the iterative approach. That's not to say that you don't gain, it's just to say that I don't get it! As has been said, the key point about lum is that it is ultra fast since it is R plus G plus B at the same time. RGB or OSC cannot compete with this speed. It works because you simply don't need as much colour information as you need luminance, making LRGB the most efficient system. If you use red as lum, or Ha as lum (as was often done a few years ago but has, thankfully, fallen from fashion) you are illuminating your image in the light of red (or narrowband red.) How can this be right? Try it on a daytime image. Red is red. Luminance is full visual spectrum. I want my natural colour images illuminated by the full visual spectrum. For me that's the whole point. Not that there are rules, but I'm stating my own imaging intentions here. Olly

I think the point s that the ACF does not need flattening. It has, like the Celestron Edge, a natural flat field. The OP just wants to reduce the FL without messing up an already flat field by re-flattening it and renderng it curved. Olly

Here's some information if you scroll down the page to the LX200 bit. http://www.franskroon.nl/equipment.htm Frans has been one of our regular guests for years and I can promise you that he knows what he's talking about. Olly

The carbon is not really about weight, it's about stiffness and freedom from thermal expansion/contraction and its effects upon focus. On the other hand the carbon is maybe more likely to retain heat in the tube. How does this really play? Does anybody really know? I know I don't. I wouldn't listen to anybody who hadn't imaged with both, that's for sure. Olly

Yes. The serious imager with the luxury of money on the table needs to begin with focal length. What do I want to image? Next comes How big is my chip? I need a FL which will cause my targets to fill it. And then comes the killer. What F ratio can I afford? If you've already decided what FL you want this really means, What aperture can I afford? In reality amateur imagers (99.9% of them) simply have to accept that, as their focal length goes up, their focal ratio goes down. Personally I'm up for accepting that. I've already accepted it. Our TEC140 at 980mm FL is F7 while at 530mm we have the pleasure Mr Takahashi's F5. I have no desire to focally reduce the TEC, even if this could be done without filling the images with reflections, which is doubtful. I want it for the FL it brings. If I do go for something approaching 2M FL I'm going to be very lucky (and out of pocket) if I don't accept F8 or (quel horreur) even less. But I'm thinking about it. Olly

But would it? On the images (the exquisitely lovely images!) you've posted above you have a fair amount of space around the main targets so you might be able to frame them at native FL. Reducers bring no new object photons to the table, we must remember. All your reducer does is pour the same number onto fewer pixels. If you present the image at a smaller size won't you have the same effect minus the light loss of the reducer? I'd be strongly inclined to give it a try. If I were to buy one of these (distinctly possible) I'd be after the focal length. Olly

It's nice! (It would be nicer still to have one tonight but there seems to be a mania for thunderstorms at the moment!!) Olly

Here's one, bought second hand in the UK several years ago. TEC140 triplet Apo. Great visually and a super imaging scope for full frame CCD which it covers effortlessy using the TEC flattener. It is, in every way, such a nice scope. Then there's the Tandem Tak, half of which belongs to Tom. This pair of old fluroite FSQ106Ns cost less than a single new one but they are both great. The dual rig is a treat, especially for guests wanting to work fast. Why am I so keen on refractors? For imaging they are so easy and reliable. FOr visual I just love the quality of the image. I know you don't have aperture but I just adore that quality. Olly

From what I've seen the SQMs which have been here have been remarkably consistent but, as Steve says, for my purposes and, I guess, his, it's being internamlly consistent that matters most. In a break from the norm the whole of this month's dark time has been with visual observers. The Meter has behaved exactly in accordance with my night adapted impressions since it arrived so I'm more than happy with it. I haven't had a significantly bad sky on which to test that side of things, though. A pleasant enough problem as problems go. I trust Per won't be imporitng too many clouds tonight! You can't rely on customs to weed them out these days... Olly

It seems to be almost instananeous. Maybe a couple of seconds. Olly