ollypenrice

Let's ask PatrickO if he wants to do an 18 panel mosaic of M31! lly

Smaller targets are free! 🤣lly

Yes, it's as Grant says; you'll have less than half a degree FOV with that setup and M31 is about 3 degrees. You need a smaller target! Olly

An aside, but Takahashi do the Extender Q which is designed for the task, but I've never used the one I have. There's a big loss in field of view. Olly

I have a Moonlite but don't use it. It's too prone to slipping with a heavy CCD. A number of friends have found the same. By far the best focuser I've ever used is the FT rack and pinion on my TEC. Olly

Assuming you mean for deep sky imaging.? New... nothing that I know of. Cameras at that price have tiny chips and your telescope has a focal length of 900mm (if I'm right?) This will give you a miniscule field of view at a high resolution, which is also the hardest kind of imaging to do. I would begin by plugging in your scope and potential cameras into this kind of calculator to get an idea of field of view. https://www.12dstring.me.uk/fovcalc.php Too small would drive you mad and limit you to tiny, relatively obscure targets. If I've missed a sub £500 camera and you can find one with a workable chip size then ignore me. Used would be much more promising. CCD cameras have dropped in second hand value but remain superb instruments. They include models with larger chips for a better field of view and larger pixels for a sampling rate better adapted to 900mm. So I'd look for a used CCD. Olly Edit: Crossed with Clarkey above. I plugged your scope, the ZWO 294 and a 0.7x focal reducer into the calculator in the link. It looks as if you would need a 4 panel mosaic to image M42. That is very limiting... However, check my findings.

Is it like this a) in the flats themselves and b) in the stacked lights if you don't apply the flats? Olly

We assume you're not using a diagonal anywhere? How are you defining the chip orientation? If you look down the scopes from the front you'll be able to see the chips. That's the sure-fire, software-free way to know that they are aligned the same way relative to the mount's saddle plate. Once they are, the read-out software may do two things to confuse you: it can present you with an image rotated by 180 degrees or even a flipped (mirrored) image. I don't see how it can make the long side the short side, though! Olly

The problem in astrophotography is not getting more resolution by having smaller pixels, it is matching your pixel size to your telescope so that you are not chasing resolution you will never achieve and, in so doing, putting too little light on each pixel. As for printing, you will still get a reasonable result by resampling your image upwards using an option which preserves details. The print will not contain more detail than it did at its standard size but you are likely to look at it from a greater distance. Plug your potential camera and scope into a calculator like this: https://www.12dstring.me.uk/fovcalc.php If you are using a mobile setup you will be very unlikely to be able to resolve real details with any sampling rate below 2 arcsecs per pixel. Using pixels which give a lower value in arcsecs per pixel is OK but will not allow you to make a better large print than resampling a smaller print upwards. Note that 'resolution' is carelessly and inaccurately used in the daytime camera wold. People assume it can be measured from the megapixel count of the camera but it can't be defined this way. It is the pixel size and focal length which matter. The field of view is controlled by the chip size in mm. For mobile imaging, one shot colour does make sense and is cheaper. Olly

As Vlaiv says, it does correct and really quite well, though not perfectly. It's worth reading about its highly eccentric inventor. https://en.wikipedia.org/wiki/Bernhard_Schmidt Olly

The combination of Sahara sand, if you still have it, and moonlight is not a good one. I must say that I don't do anything during the full moon week, even in Ha. Olly

If you start with that attitude - ie 'Need to understand,' then you'll succeed. That's very different from asking, 'What do I click?' I'd make it a benchmark for selecting tutorials as well. The moment the video maker says, '...then I just play around with the sliders...' turn them off. And be warned, there are some truly terrible tutorials out there. Olly

Yes, that's great. Olly

This won't make any difference. What you're seeing looks normal to me, too, and that's why the manual places so much importance on collimating with the star in the centre. If you have an EP with crosshair I'd use that for centering and re-centre between each adjustment. You're a bit off near the middle as well, as others have said. (The secondary shadow is slightly displaced to the upper left to my eye, and the best star shapes are slightly left of the image centre.) Olly

...though you might wait a year. Which reminds me, does anyone still say 'Donkies' years?' My grandmother (born 1890) used it all the time to mean 'ages and ages.' Olly

Good resolution of small stars, there. Olly

I agree with everything except the alt-az mount. Alt-az is fundamentally wrong for AP* and I believe it's best to use kit which is fundamentally right. My only experience of a 'wedged alt-az' was a nightmare, but you've clearly read up on this and been convinced. It's just that you're deviating from your intention of getting it 'right first time,' in my view. While you're thinking about your setup you might also be wanting to be thinking about your image pre-processing and post-processing software. Like many people who've been doing this for a long time, I use a confusing and promiscuous mixture of software. I wouldn't recommend this to a beginner! I'd nominate Astro Pixel Processor, probably, but there are others which I've never used. Olly *Without a field de-rotator.

The badness of a joke could, perhaps, be expresssed in skunks? (Or should that unit be reserved for anther purpose? Don't go there!) Olly

Triceratops: How bad is it???? T Rex: It's the full giraffe... Olly

...and the Serpentine as a derived value, S2/S1 (when S2 is the serpent's own length and S1 is its length as measured in a straight line from tail to head. It is sometimes argued that a serpent is faster when it has a low S ratio but this is an example of the S ratio myth. Olly PS, Could wavelength be measured in Mexicans?

I got it. As an imager I felt I had to photograph the volume of the extraterrestrial body in question. (Exposure time 0.3 hummingbirds.) Olly

Really lovely stuff. I never get on with false colour as well as I do with with natural so I instinctively go for the HaOIII. However, the Hubble image has more striking local contrasts. Obviously these extra contrasts are provided largely by the colour but I wonder if some of that extra contrast comes from brightnesses as well? You could find out simply by putting the Hubble over the HaOIII as a luminance channel. I'm guessing you removed the stars and replaced them with ones with a softer stretch? They are admirably tiny! Another thing I like is the way you've gone deep on the gasses but not turned them into something solid-looking. They still look gaseous. Chapeau! Olly

I find that images shot at 0.9"PP look fine at 100%. The ones I used to shoot at 0.6"PP did not. When I resampled the 0.6"PP images down to the size of the 0.9"PP ones they looked equivalent. I could find no consistent improvement in resolution between the two, though seeing during the runs was not always equivalent so I think occasions when one beat the other were due to that. I have never attempted to find out the image size at which I genuinely start to lose final resolution but it will be higher than 0.9"PP so I think even that is oversampled. (My Mesu mounts run reliably at about 0.3" RMS.) If you're interested in this, find out the maximum screen size your potentially oversampled image will sustain. (That's the maximum size at which you feel it looks good. Yes, subjective, but our aim in the end is to look at our pictures!) If that turns out to be 66% then there was no point in sampling at your present scale. You'd get the same or better from a system sampling of 66% of that. Amidst all the theory, there's the practice. I don't believe a 10inch SCT will give stars as tight as a 5 inch refractor. The theory can say what it likes but I find SCTs to give bigger, softer stars. Olly

...quite so. And handset, of course! Yes, I still use those. Windows updates? Pah! Olly

I'd certainly try it. Professional astronomy flats contain pixel by pixel information which would, of course, be lost in binned flats. I doubt that amateur flats do so, though. We're just trying to correct for the broad inequalities of the light path. You'd want to use unbinned darks-for-flats to calibrate the unbinned flats, though, before software-binning them to match the lights. There might be other effects coming into play as well. Given that flats taken strictly by the book sometimes play up (usually by over-correcting) I think that predicting the outcome of your proposal might be difficult. Just try it, say I. Olly