ollypenrice

Quick question: why would you take different sub lengths? It is very rare indeed that an object's dynamic range requires it. M42 is the obvious example of one which does, but the difference in exposure time needs to be extreme in order to solve the problem. 99% of the time it makes more sense to use a single exposure time. Olly

This is such a faint, dark object that I don't envy you the task of prizing it out from the light pollution. You've done it, though. Good going. Olly

Nice moody image. I'd say the colour balance was rather swayed towards green and away from blue, maybe? Olly

This is incorrect. There is no increase in the amount of light per unit time because the available light from M33 goes into the front of the telescope and cannot, therefore, be increased by a lens at the back. What the reducer does is put the same amount of light onto fewer pixels, exchanging intensity for scale and resolution. Your calculation applies when the aperture is increased so as to reduce the F ratio. When the focal length is reduced to increase it, all you get is a smaller, less resolved, but brighter image in the time. This debate is an old one and is usually called The F Ratio Myth, which will Google. Olly

Great image and spectacularly deep. I did this in the Twin Tak rig and gathered an enormous amount of data on it, but this is signifcantly deeper. I saw no sign of that tenuous blue nebulosity in Stock 23 (a lovely cluster) and there's an impressive confidence in the two VdB objects. Olly

Buying a new 200D, the necessary accessories and the modification is going to cost so much that it will make an almighty dent in any budget for a dedicated camera. It has always seemed to me that the one advantage of a DSLR is that it can be had cheaply. In all other respects they are roundly out-performed by dedicated cameras which, since CMOS took over, have become much, much less expensive. Olly

People can get used to anything. I had family living in Feltham who had got used to a constant mush of white noise which rose, as fights went overhead, to a volume making conversation impossible in the garden. At its quietest it was still quite loud. It's the same with light pollution. People have got used to it and even come to fear the dark, associating light with security. The question is, why should we have to get used to it? It is unspeakably vile. I live in a house with, in effect, no light pollution and I find staying with family in town very unpleasant once night fails to fall. It is unnatural and bad for the spirit. I love seeing the family but, ack, that orange glow... Olly

https://www.pixelskiesastro.com/contact I know Dave Wills and Colin Cooper and reckon they are straight players. Olly

Yes, I see in the link that your original Flame is the classic colour. The addition of Ha doesn't normally change it by much, I don't think, either in PI or Ps. Olly Edit: I only focus on this because Ha blending is mentioned in the title. It's a good image.

Lovely - and yet another testament to the MN190. Those optics really should get more attention, especially now that cameras have made a metre such a potent focal length. Olly

Now that is a piece of work! Absolutely splendid, giving us something few of us have seen before despite its lying in a much-photographed constellation. It's also beautifully done. Hats off! Olly

You are simply meeting the virtues of the camera and seeing why it beats a DSLR. As stated above, it will probably be too bright for the moon. I've never had a deep sky CCD camera which could image the moon and I've had quite a few. AdamJ is right: you must dim your flats panel to give long enough subs to avoid seeing the wipe of the shutter. The good news is that typing paper is all you need. Olly

Exactly! Olly

I wonder what colour your broadband-only Flame was? In this it's rather red when it is really a more yellowish-orange colour than it appears here. Is this a result of the Ha addition? I don't know how APP blends Ha. Olly

Good result. I don't use mine for astro but I think it's a mind-bendingly good lens, especially at the price. Camera lens images are going to be star-dominated because of the small aperture producing large stars. I think that if you ran your image through Star Xterminator to remove the stars, you'd be able to stretch the galaxy harder then replace the stars at a softer stretch to keep them down. Lovely star colour in yours. (Starnet++ is an alternative to StarXt.) Olly

I have two Geoptik panels. One has worked fine for several years, the other has stopped working just out of warranty. It was a big one and expensive, so I'm not happy. I now think that some clean white cotton (ex sheet!) in several layers, and stretched over a wooden frame, will become my default sky flat solution. I've previously been stung three times by failed Aurora panels as well. Olly

I don't agree that darks and bias should be re-done after a change of scope because, if there were any difference between them after this change, it would be because they were affected by light leakage and no good anyway! The best way to do darks and bias is off the scope with an absolutely perfect seal to prevent light ingress. Many camera makers include a screw-on metal chip cover for just this purpose. When I compared darks done this way with darks done on the scope, with every effort to exclude light, I found a perceptible difference because excluding light entirely is a lot harder than you might think. Flats record the projected light through a specific optical train at a specific orientation onto a specific chip, so they must be done after any change and at the focus position used for the lights. Olly

I think Wim and Tomato have it. A glory of warm core, blue arms and magenta splashes my look nice but I don't think it's the truth. Olly

In truth, I don't think the RASA is 'soft,' exactly. Stars present a very specific optical challenge and it is on stellar shapes that it is at its weakest. In terms of the resolution of other detail, I've no beef with it - though I haven't done a direct comparison. To endorse the points made by Goran and Tomato, a difference in speed at the scale offered by the RASA doesn't just make a convenient difference in time, it makes, in reality, the difference between the possible and the impossible. I have participated in a 400 hour mosaic once, with Tom O'Donoghue. On occasion we had three identical rigs running simultaneously. I probably wouldn't do so again, but shooting 400 hours in 90 hours is a very different proposition and that's what we did for the M45 to California mosaic in the RASA. Olly

It should work but, being a Quark, it might not! The 4 inch refractor, though, is a very fine thing. Olly

OK, this may be true, though some reducers bring image quality issues of their own. Extra glass means extra dispersion and the risk of internal reflection, both of which we've seen on SGL in the past. My earlier aim was to challenge the overly simple notion that F ratio alone determines exposure time in digital imaging. Olly

Strictly speaking I'm a RASA user, not an owner, and my detailed findings were published in Astronomy Now in a full length review. If you want the best possible star shapes with the highest degree of consistency then buy a high spec refractor. I don't think that's very controversial except, perhaps, among those who don't think star spikes are artifacts. 👹 Modern processing, involving the separate stretching of stars and target (where they are not the same) means that the need for the best possible stars at capture is greatly diminished. The RASAs are widefield instruments by dint of their focal lengths, so we are talking, most of the time, about a large number of small stars. The stars we are getting in this context, processed through StarXt, are OK. The non-stellar parts of our captures are sensational - in my view. It's hard for me to make direct comparisons between the dual Tak FSQ106 rig we ran and the single RASA because we are using a modern CMOS in the RASA as opposed to old CCD in the Taks. What I will say, without any doubt, is that I would not go back to the old dual rig over the RASA at any price. I'm not a pixel peeper and I don't process for pixel peepers. I'm interested in the big picture, seen at a size which keeps it the big picture. If that's your thing, you'll love the RASA. If you look at images in a different way it may not be. Olly

Sorry, I'm not with you on this. A target focal length at a given aperture does not allow for any variables so what are we comparing with what? Olly

Same for me. I also took the advice of Ian King who basically said, just go straight into mono CCD. I was up and running in no time despite the fact that, back in those distant days, I had hardly any computer skills and no forum help as there is today. (We were on dial up.) Olly

Indeed, though I thought there was a bit more than that to 'étendue' so I stuck with 'flux per pixel.' Doesn't étendue also have something to do with the efficiency of a light beam at a steep angle? Or something???? 🤪 Olly