ollypenrice

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

Good to lnow. lly

Well, the latest underwhelming news of my own 1.8 x 1 metre copy of the print is that it's gone off the parcel tracking radar just before midnight on the 14th at Heath Row and not been heard of since. Disgruntled of South East France.

I reckon I could see the Las Vegas light dome from Dante's Peak above Death Valley so you have your work cut out lving near it! Olly

I should, I think. Thanks for the link. Olly

It's funny, I thought of the wall as I took the picture. It is very un-English, as you say. Lime mortar and the warm tones of the stones, which have no moss or other growth on them. Our walls are home to little rock lizards and we have redstarts nesting under the edge of the roof tiles at the moment. Inside the house under natural light it reads 7 so it will read in poor observing conditions (which I think would describe our stting room... ) Olly

Although I've seen these regularly in the hands of our guests, I've never had my own... until now that is, because two kind guests, John and Viv, kindly sent me one as a present yesterday. I was thrilled to bits because these devices are so useful, espeically to the imager. Many members will know of them, but for those who don't they look like this; You simply hold them in this position, pointing to the zenith, and press the button. A sensor on the top measures magnitudes per square arcsecond. If this sounds a bit arcane, don't worry. It appears as a number on the digital scale. The scale is logarithmic so is highly compressed by the time you are in dark sky territory. A value of 21 is roughly where good sites begin and the best reading I've ever heard of was 22.1 in the Australian outback. Sky and Telescope suggest that 22 is generally considered to be the level found under a totally dark site on a moonless night. They discuss the use of the meter here; http://www.skyandtelescope.com/astronomy-resources/rate-your-skyglow/ Last night, with twilight still clearly around, we started at 21.1 and were at 21.6 by midnight. The best anyone has recorded here is 21.9. If I ever see 22 I'll throw a party! (In the morning...) One use of the meter is to scout around for the darkest site in your area. For me its usefulness arises from the fact that, when imaging at the PC screen, it is impossible to assess the current sky quality until your eyes are dark adapted - and that takes ten minutes as a bare minimum. With the meter you can check the sky reliably and immediately and so decide whether the clouds have scuppered you or not. The manufacturer's website is here. http://www.unihedron.com/projects/darksky/ Very highly recommended. Olly

Clouds? Rings a bell. Aren't they a British thing? lly

Heheh, a reasonable car could indeed be anything. A full size 8 metre high print would, I think, buy a car we would, as confessed petrol heads, both consider reasonable. Maybe not new, but reasonable enough to scare the pants off us. Maybe it would be better to describe such a car as unreasonable... Ah yes, that's more like it! lly

So far, no. Tom has organized some big prints, two for people who've asked to buy them and one is currently on its way to me in a large cardboard tube. These are 'only' 1.8 metres high. I haven't yet broken this news to Monique's picture framers but I'm sure they'll be able to deal with it. Tom will be here next month and we'll get down to discussing how to propose a big one to museums during his stay. I do hope we can find an interested party but Tom and I can't afford to get a full size print done. It would be the cost of a reasonable car. Olly

I think it inconceivable that taking half as many lights and dark subtracting them would give as clean a result as taking twice as many lights and not dark subtracting them, especially if a small dither were built it. The dither wouldn't even need to be activated between each sub. The occasional movement would do. I share Michael's disapproval of gadgets which think they more about what I want than I do and I also share Ronin's view that there are too many holiday snaps in the world. (Why do so many people bother when they could just look at mine?? ) Olly

Agreed, a first class account. We don't often read what you say in your opening paragraph - that a dark site is not apparently dark at all. The more you adapt, the easier it is to move around. We have even debated whether or not Jupiter casts a shadow. What makes moving around impossible is the arrival of mist. Living at 900 metres (3000 feet in old money) we are sometimes cut short by rising valley mist from temperature inversion and at this point finding anything, even at arm's length, becomes near impossible. When imaging, one problem is assessing the sky, which you cannot usefully do withing ten minutes of looking at a screen. This is whee a sky quality metre comes in. We are usually between 21.6 and 21.9 on clear nights here. In the outback I gather that you can hit the low twenty-twos. Olly

Good stuff. Hope it all gets going nicely! I still watch in bemused wonder as the Per/Yves/Grinde/Jeff/Woodsie shed suddenly springs to life in our back field. On occasion it scares the life out of me when I have my back to it (I don't know exactly what a wild boar contemplating a charge really sounds like at close quarters...) Olly

We can't have young Mr Goodricke so upset after all he's done for eclipsing binaries! Larger one is here; http://ollypenrice.smugmug.com/Other/Best-of-Les-Granges/i-LgK642h/0/O/ORION%20400%20HRS%20WEB.jpg Smaller one is here; http://ollypenrice.smugmug.com/Other/Best-of-Les-Granges/i-LgK642h/0/X3/ORION%20400%20HRS%20WEB-X3.jpg Olly

Tom and I are not expert tattooists (perhaps with no direct hands on experience whatever so far...) but I have a Dremmel Tool and Tom has some inks he drained from disused ball point pens and we'd be delighted to have a go. If SGL members would care to form an orderly queue we'll start drilling straight away. Once the survival rate hits 70% we'll try to set up a deal with Steve at FLO... Olly

Nicely moderated. Thanks Auspom. I only mentioned the print in the first place as an explanation as to why we worked at this focal length, creating an image that is too large for PC screens. Cheers, Olly