michael.h.f.wilkinson

Yes, I know all this, I teach computer vision at the university, and I include lectures on the human visual system, on which many computer vision methods are modelled. But as I said, an experienced observer can pick out the moments of good, steady seeing, and I can readily spot the appearance of granulation as the image snaps into view. This is also important, as the image is not stationary while focusing, and the human visual system is extremely adept at picking up temporal changes. This is why you can pick up very faint fuzzies by nudging the scope. The moment the blob moves in the FOV, other parts of the visual cortex kick in (notably in V3 and V5), and detect these slight changes that would go unnoticed if viewed as a stationay image. Experience of the observer also plays a role: in variable star observing, you tend to get better and better at picking out slight differences between stars, as you gain more experience. Regarding motion blur: this is why I advise people to take a lot of time observing planets: there are moments of prolonged steadiness in the atmosphere. These are rare, so you have to be patient enough to observe them

Note that lucky imaging cannot extract detail that isn't in the data, and the images clearly show the presence of granulation, albeit at a very fine level. It is also not noise, as you would then expect to see regions with the "wrong polarity", i.e. dark speckles on a lighter background, rather than the reverse (on occasion you see the odd pore, of course)

I typically know I have hit perfect focus when granulation appears. The C8 can show more detail, for sure, but the grains are clearly visible in the 80 mm.

I can see granulation at the eyepiece without issue, unless seeing is very bad. The brain can memorise the moments of good seeing very well (which is why planetary sketches showed more detail than photographs managed).

Darks don't always calibrate the pattern noise fully, but they do reduce it well. I also find that when combining data from different sessions, where the camera is tilted at a slightly different angle, the stripey appearance is reduced very effectively (more data so less stretching also adds to this effect)

I regularly spot granulation in my APM 80mm, but more aperture certainly gets more detail. I have ordered a 6" F/5.9 achromat for solar, and with a solar continuum filter I don't worry about CA. Big sunspots and granulation in 2017, using my APM 80 mm F/6, with 2x TeleXtender

This kind of pattern noise is frequently seen in DSLR chips, especially when the temperature is high, and dark current is stronger. You have stretched the background quite a bit (hence the noise) so they pop out strongly. I would guess darks and flats, and dithering would remove them

The 102 mm is bound to show more detail, especially when using a solar continuum filter, which hass a fairly narrow passband, so chromatic aberration is hardly an issue

I put it at 8.5 or a shade brighter, certainly much closer to the mag 8.5 reference star in the AAVSO chart than to the mag 7.1 star. I did quite a bit of variable star observing as a teenager, but stopped when I started studying astronomy (mainly through lack of a telescope in my own place), so I may have become a bit rusty. Having said that, I do not think I am a full magnitude off.

A drop by 2 magnitudes in just two days is quite unusual for a nova. Very curious to see what happens next

I struggled with my 16x80 bins (against a rather bright night sky here in the North of the Netherlands). Curiously, the nova showed up easily in my 80 mm F/6 triplet with 31 mm Nagler (so 15.5x). Even though the Helios LightQuest 16x80s are pretty good, the APM triplet concentrates the light of stars into far smaller points, making fainter stars much easier to spot.

I put it at 8.5, or a shade brighter.

Hope to have a go at this tonight

CA in DSO seems to have a different impact than on planetary imaging, I find. As a rule, the centre is better corrected than the edges, and although you are working at higher resolution, you do not stretch the lower intensities as you do in DSOs, so the wings of the PSF aren't artificially boosted. This is because the dynamic range is much lower in planetary imaging

In my experience (on other scopes), under good seeing conditions aperture is king for planets (imaging and observing). All three have pretty similar apertures, but unless there is something seriously wrong with the 125 mm doublet, it should have the edge in terms of resolution. The colour correction will theoretically be worse, but this will hardly be noticeable visually, and even in imaging I doubt the additional colour fringes could be spotted. Again, all lie in the 4-5" range, so changes won't be dramatic.

We were live-streaming the event from the Blaauw Sterrenwacht, using my gear, and I had some time to capture data. Here is the first one. Not brilliant, but the best I could do to focus the Coronado SolarMax-II 60 (single stack) on the little chip of the ASI178MM. The Coronado focuser is really cruddy for imaging (reasonably usable for visual). The sky was pretty hazy which didn't help. Grey scale: Pseudo colour:

First NLCs of the season. Not brilliant, but at least I have a result

Many (older) laptops have both USB 3 and USB 2 ports, with the one type usually on one side of the machine and the other on the other side

The internal SSD in my newer laptop is indeed even faster, than the T5s, but the T5s work well on slower laptops

Older SSDs can be slow, and are often cluttered, because the OS hogs a load of space. I used the external SSD in the old Core i3 laptop and got much better speeds. I have a couple of these Samsung T5 SSDs (and an older T1), dedicated to image capture, and they work really neatly. You could try one, and if the old laptop really isn't up to the task, you can still use them with a faster laptop

I have obtained high frame rates with my ASI174MM on a modest machine in terms of CPU and RAM (Core i3, 4 GB), but with a very fast SSD (an external Samsung T5). Processing speed is not the issue, this is purely an I/O-bound problem. I do remember tweaking some USB speed settings for maximum speed using FireCapture. Things do run more smoothly on my Core i7 laptop.

I will be doing WL only in the solar continuum band, so an APO isn't really necessary

Welcome to SGL, from the North of the Netherlands! Indeed this is not the best climate, but we persevere. If you also happen to be in the North, don't hesitate to drop me a line

The Technosky/TS is apparently a touch lighter (but that may be because the ES includes a finder and star diagonal). Both my Vixen Great Polaris and GP-DX mounts should be able to handle the scope easily. Seeing might not be ideal in Ca-K, but I have had god white light results with the C8, so I don't worry too much about the seeing in white light and H-alpha

The degree of spherical aberration is of particular importance here as is focal ratio. The Skywatcher 6" F/5 is too fast to my liking, and suffers more from SA than the others I was considering. The F/8 is too long and cumbersome. F/6.5 hits quite the sweet spot with my Baader TZ-4, F/5.9 is a touch short, but with the 4.5x telecentric underway, that is not an issue. Mechanically and optically the Technosky/TS 152mm F/5.9 edges out the ES AR152, apparently