...I've seen a lot of "in camera" images of AD's on CN Frank, nearly all of them at very short f/l's when compared to planetary image scales...but very few on the planetary imaging forum except the occasional one from ourselves or someone else rarely - although there are those that are not actual AD's, such as those this member posts with his images: https://www.cloudyni...s#entry11341763 which might confuse some people. (Post #8)
That's the critical difference, that & the other most important aspect (including our own)...they are always stacked images - neither small refractors nor CDK20's are used very often at 5-10 metre f/ls!
Your "higher power" comments are of course right on the money...& in should be said that seeing AD's visually though an ep is much easier - & common - but I am completely against imaging without collimating "in camera" for a number of obvious reasons.
I appreciate the comments about folks using <"the fuzz around the moons of jupiter"> but I'm not too sure about the quality of many of those images tbh...I see it as akin to Bahtinov mask focusing, or those that claim their SCT's maintain collimation for months or years on end.....like anything, the combinations of "adequate collimation" coupled with very good seeing can produce outstanding images from time to time - but to obtain consistency over years & years of imaging you cannot get away with an approach like this.
Pat & myself rather conceitedly claim this sort of consistency over many years, with hundreds & hundreds of high-resolution images. (not dozens & dozens as I stated earlier )
And, surprising or not to you Frank, we have never once seen an Airy Disk manifest itself onscreen as a complete, consistent entity in all our imaging years..! This includes 2017 when we beat the Keck to capture images of EQ storms on Neptune.....mind you, as I've said frequently since, the seeing was so darn good that we could clearly see the difference in focus using the blue filter with a shift of 12 microns - that is some seeing! No complete AD however...except in the stacked image.
That said, FireCapture's live stacking (or a similar feature in Sharpcap as I understand it) should prove invaluable wrt these points...although we do not utilise that function personally.
In the words of the great man himself (Torsten Edelmann) <"In FireCapture select "Stack" from the pre-processing drop-down list and from the number of frames you want to stack from the slider below. It will stack those in the preview and in the captured data.">
None of the preceding is any any way meant to depreciate Frank's general comments.....& these excellent capture programs' live-stacking options appear to remove the main issues in my preceding comments (perhaps even explain some of Frank's comments about seeing AD's wrt planetary imaging)...& I encourage people to adopt his Metaguide software also, especially if they find commentary like mine too confusing, which is often, I suspect - we're "Old School" & it took a long time to get to where we are, requiring the sort of OCD fairly common amongst planetary imagers of our ilk
Lukas, along with our "rapid cooling" technique I've also installed over-sized knurled brass adjusting "wheels" on the secondary screws...actually brass sheet cut into disks with knurling filed into the edges...drilled & tapped to accept machine threads longer than & in lieu of the original phillips head screws. (3 or 4mm off the top of my head)
This gives me considerable advantage in applying those final tweaks in very finite amounts to the extent that at the finish of collimating I will apply only pressure on any of them without actually detecting any movement in the screw-wheel itself - but manifesting itself in the resultant star-pattern. (again, if the seeing allows so)
As to the cooling method, we use 2 large orange, heavy duty garbage bags (I think they are a universal product) with the outer one a "fail safe" protector. The inner one we carefully fill with 5kgm of "party ice" & sprinkle 1kgm of common salt onto it & mix in quickly, applying the bags to the C14 facing straight down & using a cloth face washer to protect the Moonlite focuser & some pointy bits on the back casting first.
We will also carefully wrap a doona around the scope & over the ice bags to assist further. (it is already on the mount of course)
When the temperature is about 2°C below the anticipated air temp of the start of our imaging session we remove all this paraphernalia & allow at least 20-30 minutes for the primary mirror to relax before collimating at the start of every imaging session. (I should mention that we installed a dual thermometer to measure primary & air/ambient temperatures - easy with any of the ventilated Celestrons but a bit more complex on those that are not, such as our old C11)
Being a degree or so above or below the ambient does not seem to matter terribly, but too warm & heat flares & image degradation occur.....at colder temperatures the DR's take on an elliptical appearance but don't seem to affect the image as badly as too warm a primary...