geoflewis

I had the same alerts here in Norfolk and the same cloud covered sky.....

Sorry Vlaiv, what are we meant to do with these?

Thanks John, this has been a very enlightening discussion for me.

I had a couple of goes at Saturn with the 462MC, but they were worse than I got last year with the 290MM, however, I had left it until well past opposition this year to even try, also I think I was applying IR as lum last year, so not a fair comparison.

Thanks Vlaiv, I think you may have hit the nail on the head. It may just be that it is easier to dial the focus with a bigger 'oversampled' image on screen. I certainly found this to be true when Mars was last close to us in 2020. I was operating at ~F22 for Mars in 2020, but only F12 for Jupiter and Saturn last year, but of course Jupiter and Saturn were much lower down and imaging them at all was very challenging. So far this year I have imaged all three at F12, but I am going to experiment with different amplification to see what differences I get, especially with Mars smaller diameter this year, but up at ~60° elevation. Thanks for all your advice on this complex (to me anyway) topic.

Ok , so if there is no detail loss due to oversampling, then that suggests that I'm definitely better to 'risk' oversampling versus undersampling, which is what I think I may be doing without any amplification in my image train - I think we calculated I am currently at <=F12 or 0.14"/px. There may be worse SNR at F22 v F12, but will I actually see it, especialy if in excellent seeig I can stack >10k frames? However, maybe at F12 I am not fully utilising the optics and I can't ever recover what I didn't capture - is my logic still wrong?

Ok, now you really lost me. How is comparing HST image with ground based image relevant to this discussion?

Who produced the image on the right and what equipment were they using please?

That's a cracking good Saturn Neil

@vlaiv Thanks again for the additional analysis and supporting images. It is beyond my ability to understand what you are saying, sorry. Well I understand what you are saying, but not the maths that 'proves' your analysis. It still leaves me questioning why the expreience of Chris Go, Damian Peach, et al, differs from your mathematical analysis. I think that they fine tuned their approach based on experience, so when experience/observation challenges the maths, I have to question the maths - it's almost like Ptolemaic v Copernican arguments. OK I know it's not, but hopefully you will understand my reasoning for doubting the maths....

Thanks Vlaiv, I am not a physicist, so can't challenge the theory on any basis other than experience, but I still contend that there must be something going on. We are not talking about hack imagers, but the world's best, so IMHO there must be a 'real' reason why they chose to sample at F22, F24, etc., with small pixel cameras like the 290 and 462 sensors. Look at the image from 5 Nov and more so the comments by Christopher Go. http://astro.christone.net/jupiter/ He clearly considers it an extremely good image displaying very fine detail, so I am curious what 'high frequency components' he may have lost by imaging at F24 rather than F12-F14 that you contend is optimum for his configuration, which is essentialy the same as mine and Avani's? Please know that I'm not just rejecting your analysis, but I can't for the life of me understand why the field evidence of these very experienced, talented imagers doesn't tie with the theory....

Thanks Avani, it's very good to hear from you. The topic of correct sampling is indeed very interesting; I'll add you to the growing list of planetary imagers who find that sampling well below (ie. much finer) the theoretical numbers as calculated by @vlaiv, just works. There must be something in the maths theory that just isn't correct as all the best planetary imagers get their best results imaging at 0.1"/px or lower, where the maths is saying optimum for C14 is ~0.14". It's a huge difference in sampling rate and I'm at a loss to fathom why the theory is not supported by evidence in the field.

Wow Neil, I've only just seen this, absolutely superb detail. I'm estimating down to <2km comparing with LROC quickmap....👏

Excellent animation and as others commented, it really deserves its own thread.

Excellent image NV. I was clouded out for this event and travelling for the similar transit the previous week, so good to see your high quality version.

Hi Nigella, I guess it’s an ‘it depends’, question. If de-rotating the SER/AVI then that will be unsharpened, though you may use a sharpened image as a reference frame. If I’m stacking each SER first, eg via AS3!, then yes I will sharpen with wavelets in Regustax, but I’ll hold back a bit to leave something on the table, so that I can take the de-rotated stack out of WinJupos, back into Registax for a final tweak. I think WinJupos handles a lightly sharpened TIFF better than unsharpened, but don’t overdo it as that could introduce artefacts that WinJupos might treat as real features. Nice Jupiter image BTW.

Just read the extra comments - all excellent info, thanks

Thanks Lee, that’s the configuration I was thinking to use . I’m going to try the Baader lens on its own, screwed into the nosepiece of the camera (I’ve already confirmed that it fits ok). So the configuration will be scope -> ADC -> FW -> Barlow lens -> camera, but I’ll be experimenting as you suggest. I use FireCapture for capture, but can set the ROI in the same way you describe to measure the planet - I can’t believe that I never thought to do that previously 🙄. I’ll then reset the ROI with a bit to spare around Jupiter for the capture itself.

Thanks Vlaiv, this is helpful, even if I don't fully understand all of it. Regarding my Jupiter image, WinJupos measured it at 349.8px, not the 339.8px that you used in your calculation and yes, it was when Jupiter was displaying a disc diameter of 49.2".

Thanks Lee, yes, I'm aware that the change in magnification for TV PMs is different than how it works for barlows. As the below chart of the TV website, shows there is definitely a reduction with the x2.5 PM the further it is from the sensor, but for the x2 PM the change is very marginal. It's one of the main reasons I moved from using the TV Barlows to the x2 PM. I have the ADC between the PM and camera as the ADC is 1.25" diameter, whereas the PM is 2" diameter. I'm also using a FW, so that increases the distance to sensor a bit too.

Thanks Lee. This whole discussion the last couple of days has been eye-opening for me. I've just fairly blindly followed the px_size x5 rule of thumb, then watched the on-screen image to see what worked. I felt including the x2 PM with an ADC was too much and I think last year I took the PM out when imaging Jupiter which was still very low down. On Anthony Wesley's (Bird's) advice I'd taken the ADC out for Mars in 2020, but I was happy with my results still including the x2 PM. As I discussed with @neil phillips yesterday, I think I was too hasty to give up on the x2 PM with the 462MC sensor, but with the Baader barlow I have some options to increase amplification without going as far as 0.07" / px. It will be good to experiment some more, as Mars moves towards opposition over the coming weeks.

Thanks, that's great to know.....

Phew....!! So I've checked my images with the ASI290MM from 2020 and see I was very similar to Go & Peach at 0.07"/px and according to FireCapture FL = 8500mm, equivalent to F23. That worked really well, so I'm definitely going to try again with the ASI462 at greater amplification.

Do you mean 0.08" to 0.09" per px. Jupiter at say 49" / 500px = 0.1" / px not 1" / px - or what am I doing wrong please?

Thanks, I just did that and got 345 px, so very similar to the 349 that WinJupos gave me. I did the maths myself based on Jupiter's diameter at 49.2" on that night which confirms the ~0.14"/px (49.2/349). So am I actully then already oversampled without any further amplification....?🤷‍♂️