ollypenrice

Not necessarily. Because the stars are bright you don't need many subs to get a good SNR. For stellar cores what would you need? 3x15 seconds per colour? Pretty quick. Another thing that works well is to use your RGB-only for over exposed parts of the image rather than the luminance. There's less signal in the RGB, normally. You can convert it to greyscale and combine with the luminance or work in RGB in Layers. In fact I don't worry about saturated stellar cores because I find I can pull the colour into the core from the outside using Noel's Actions Increase Star Colour or by doing it longhand. Olly

I've never used one with these panels. Olly

Absolutely not. The first Avalons just used the NEQ6 motherboard, handset and motors. That's the one I had and I was very happy with it. I only sold it when I was offered a second Mesu on the used market. Actually I really liked the fact that it used these components because they are cheap, effective, reliable, familiar and spares are always available. Mechanically the Avalon has nothing in common with the EQ6. It's beautifully made, CNC machined from solid and has a backlash-free, maintenance-free belt drive system which self-compensates when it wears (which it only does very slowly anyway.) I think it's one of the best mounts available. It's expensive for its payload but I would expect it to have a very long, trouble free life. You also get excellent backup from the maker. Olly

What's your objective? If it's imaging I'd go for a new and better mount. Olly

You could just get a length of square section steel tube (probably an offcut from a local metal yard) drill it and bolt it to your dovetail and then bolt your tube rings to the opposite side of the steel. The steel between the dovetail and the scope will put the scope further from the saddle plate, considerably increasing its moment. Olly

I always wonder why the MN190 has gone quiet. I tried to buy one years ago but the rather odd UK dealer wouldn't send abroad so I went for a refractor and stayed there. The design surely has vast potential. Steve Loughran, on here, used to post great stuff from his. Olly

I'm sure it does but 'daylight' is noise and Jupiter is signal. More aperture builds signal faster than noise. It really was very strange seeing at least nine cloud belts on Jupiter, in reddish brown colour, plus the transit, against a blue sky! The Jovian detail was comparable with that seen in our 14 inch SCT at night. Olly

This is what my optical guru said in reply: Yes, in general, a mirror is much more sensitive to any kind of unwanted pressure from the mount. A reflective surface gives more ray deviation under a certain pressure than a refractive element does. Thats also why a lens performs better than a mirror when surface imperfections (rms and P/V values) are the same.

Nah, it's just what happens to be kicking about around here! 😁lly

Ah yes! Good thinking. Olly

The good news: I once watched a shadow transit of Callisto over Jupiter in excellent detail, both the transiting moon and its shadow showing clearly against the cloud-belted disk, in the middle of a clear blue-sky spring afternoon. The bad news: the telescope in question cost about six million euros. It's a 0.8 metre Ritchey Chrétien with mirrors by Dany Cardoen. The planetary eyepiece is - ahem - a 31MM Nagler. This leads me to suspect that aperture might be important for daytime observing... http://www.obs-bp.com/ I'm lucky with my neighbours! 😁lly

Salut Fred. I'm an Englishman-turned-Frenchman in the south east, where I came for good skies for astronomy. Welcome to SGL. Cordialement, Olly

Thanks Ray, the observatory does have permanent webcam coverage and a log of openings and power cuts. We did some testing yesterday and the park position and limit stops seemed robust. It's now looking more promising. Olly

I was just mulling over the same question! We know that mirrors are usually left slightly loose, or at least not firmly gripped, to avoid pinching - and yet refractor objectives are also made of glass and are held firmly enough not to move. Could it simply be the size of the glass elements, the larger sizes of mirrors being more prone to expansion? I really don't know but I know a man who does. I'll ask him. Olly

The advantage of an OAG on reflectors is simply that they 'see,' and so correct for, any movement of the primary in its cell. You're not certain to have such movement, or not often, but an OAG puts you on the safe side. You're guiding and imaging on the same light cone. Olly

That is a very, very, very classy image! If you consider the components that went into it they'd include optics, camera, mount, stacking software, sharpening software and processing skill. Even if the Mak were slightly better (by no means a cert) it can influence only the first of these components. I cannot see it leading to a better image. Olly

Sure, I use the BB myself. Olly

Like you I'm a pragmatist. I need to take the process through from beginning to end. However, I'm sufficiently piqued by Vlad's arguments to want to give it a go - especially since, at 0.9"PP, I'm easily oversampling on nights of indifferent seeing anyway. An aspect of the argument which I found particularly convincing concerned sharpening. Take the core of M101 since I, too, processed Rodd's data and, by chance, another member's on M101 the following day. I then went back to my own for a reprocess, so three different captures. In none of these cases did a basic log stretch reveal much spiral structure right into the core. It was all pretty soft. However, in each case, sharpening revealed a spectacular level of spiral structure right into the core. Better still, the structures were the same in all three datasets and they agree with the Hubble image insofar as they go. This convinces me that the sharpening routines are revealing genuine information contained in the capture. Now for the crux... Why was this particularly applicable to the core? Because it had the best SNR. The further out from the core, the less it was possible to sharpen as the SNR tailed off. (My own image was criticized on the French forum, perfectly reasonably, for being out of balance with itself in terms of sharpening, the core being sharper than the rest.) So might we actually do better to get more signal of lower resolution and to sharpen harder than to chase more resolution at an inferior SNR? I'm up for an experiment. Olly

I recently processed some 10 inch Quattro data captured by another member. It was absolutely excellent and, given the large aperture for the focal length, it had gone very deep for the exposure time. The flip side of this is that the same member spent a long time reassembling and perfecting the instrument when he first took delivery of it. It was certainly worth the effort. I don't see why the 8 inch shouldn't be made to work as well as this. Olly

Yes, £6K really was a rather derisory sum! 🤣 More beer and skittles than croquet, what?

I don't follow. Sorry. Olly

I don't know it either. I've used the Picostar artificial star which is OK. Olly

He can indeed but this can be done in the daylight using the 'flats' method. Has the OP said which 80mm he's using? I think there is one which covers full frame. I know from personal disappointment that the FSQ85 doesn't, despite Tak's claim. Olly

Take a shiny new ballbearing and a decent sized old cardboard box. Spray the box mat black on the inside and glue the BB to the bottom. Set this up at a good distance from the scope so that the scope looks into the box at the BB. (There is a formula for how far away it should be but I can't remember it and got decent results from too close. It would google. The length of a decent driveway ought to do it.) Illuminate the BB with a torch beam, or whatever, just off axis. The BB test is to be found in some of the best optical shops in the world. I saw it in Dany Cardoen's workshop down the road from my place and he has mirrors at Paranal. The principle is delightfully simple: only light from the part of the BB closest to the scope will be reflected towards the scope, so it approximates automatically to a point source. It isn't as fine as a star test but it's a very good start. The problem is, with the Hyperstar, that you can only collimate with the camera and F2 is pretty darned difficult. I've commented on Starizona's claim that the Hyperstar makes imaging easy elsewhere and loudly! Olly

It was a full frame CCD but so long ago that I can't remember. It was to do with prism depth, not focus. Olly