Jupiter sampling C14 F11 vs F18 - 11 Nov 2022

[geoflewis]

Thee's been a lot of discussion about optimal sampling for planetary imaging recently, so last night I set out to do a comparison. Of course the conditions were far from ideal, with me having to dodge clouds or maybe increasing for. The seeing was average at best, but transparancy was variable, so not sure what if anything my testing reveals or proves (probably not much).

Here are two back to back images from 6 min SERs with no de-rotation. Each is best 20% and sharpened in Registax 6 using the default (not gaussian) wavelet filters. I tried my best to match the details, but that was challenging and for the F18 image introduced more noise without ever getting the same level of detail. I just could not reveal the subtle detailed swirls in the EZ and the dark and white spots towards the poles, just aren't as crisp in the F18 image.

NB Jupiter transitted the meridian at 20:30, so these were shortly after that.

F18 (timestamp = 20:42pm)

F11 (20:59pm)

Sorry, I don't know how to resize the images so that the two Jupiters are the same size, so happy for anyone else to do that or let me know how to do it.

What I can say, si that the file sizes imaging at F18 were huge (double) and AS3! on my G5 gaming laptop took for ever to process the F18 data (I thought it was going to die...!!)

Maybe in better seeing, I might get better results at F18, but currently I'm not seeing any benefit operating at the higher sampling rate; IMHO there's a lot more downside with the huge files created.

I will be very interested to hear what others think. I have some IR and CH4 images that I captured at both FLs, so will share those later.

 

[knobby]

Very interesting Geoff!

I've just nabbed a 1.5 Barlow to try (if I ever get out again) on my zwo224 /C9.25 ... I usually use a 2x but as the seeing is always naff where I live, thought I'd give it a go.

[neil phillips]

54 minutes ago, geoflewis said:

Thee's been a lot of discussion about optimal sampling for planetary imaging recently, so last night I set out to do a comparison. Of course the conditions were far from ideal, with me having to dodge clouds or maybe increasing for. The seeing was average at best, but transparancy was variable, so not sure what if anything my testing reveals or proves (probably not much).

Here are two back to back images from 6 min SERs with no de-rotation. Each is best 20% and sharpened in Registax 6 using the default (not gaussian) wavelet filters. I tried my best to match the details, but that was challenging and for the F18 image introduced more noise without ever getting the same level of detail. I just could not reveal the subtle detailed swirls in the EZ and the dark and white spots towards the poles, just aren't as crisp in the F18 image.

NB Jupiter transitted the meridian at 20:30, so these were shortly after that.

F18 (timestamp = 20:42pm)

F11 (20:59pm)

Sorry, I don't know how to resize the images so that the two Jupiters are the same size, so happy for anyone else to do that or let me know how to do it.

What I can say, si that the file sizes imaging at F18 were huge (double) and AS3! on my G5 gaming laptop took for ever to process the F18 data (I thought it was going to die...!!)

Maybe in better seeing, I might get better results at F18, but currently I'm not seeing any benefit operating at the higher sampling rate; IMHO there's a lot more downside with the huge files created.

I will be very interested to hear what others think. I have some IR and CH4 images that I captured at both FLs, so will share those later.

 

The image is clearly noisier on the F18 capture. Still worth trying on Mars perhaps as my images show. Just experiment whatever turns out best is worth trying for

Nice capture. Its getting more difficult 

Edited November 12, 2022 by neil phillips

[geoflewis]

I think this whole topic is a crap shoot when imaging in the UK. The seeing is so changable, that it's almost impossible to get a reliable comparison.

I've just processed two IR images, one at F18 about an hour earlier than the F11 image and they're like night and day with the F18 image streets better.

IR - F18 (20:20pm)

IR - F11 (21:16pm)

I've tried to resize them to the same size. It's a complete reversal of what I saw with the RGB images.....🤷‍♂️

I know the seeing had deterioated a lot and I was imaging through passing cloud, but Iif I understand correctly, accoring to the maths, the longer wavelength of IR should perform better at lower sampling rates - I really don't know what to make of it and as @neil phillips commented on his recent Mars thread, I think we can get too hung up about it and should just go with whatever works for us.

[geoflewis]

8 minutes ago, neil phillips said:

The image is clearly noisier on the F18 capture. Still worth trying on Mars perhaps as my images show. Just experiment whatever turns out best is worth trying for

Thanks Neil. Lots of trail and maybe even more error.... Take a look at the two IR images I just put up - complete reversal in outcome, with the earlier F18 image far better.....

[neil phillips]

Just now, geoflewis said:

Thanks Neil. Lots of trail and maybe even more error.... Take a look at the two IR images I just put up - complete reversal in outcome, with the earlier F18 image far better.....

Which proves its easy to jump to conclusions about this. Also proves what i said on my Mars post. there can be reasons why over sampled images may do better. Getting fine focus (especially on mars ) can sometimes be easier. Not exactly sure why this image is better. looks to me like you nailed focus better. Its nosier still. But agreed far sharper. Whatever the reason. Continue your experiments on Mars. You may or may not prefer F18 but it's worth experimenting. See what transpires. At least you know you're trying different things to get the best you can. 

[neil phillips]

And dont forget higher sampling will likely work best under good seeing

[geoflewis]

7 minutes ago, neil phillips said:

Which proves its easy to jump to conclusions about this. Also proves what i said on my Mars post. there can be reasons why over sampled images may do better. Getting fine focus (especially on mars ) can sometimes be easier. Not exactly sure why this image is better. looks to me like you nailed focus better. Its nosier still. But agreed far sharper. Whatever the reason. Continue your experiments on Mars. You may or may not prefer F18 but it's worth experimenting. See what transpires. At least you know you're trying different things to get the best you can. 

I will continue to experiment Neil, but (and for me it's a pretty big but) I'm hating the huge file sizes and processing overhead of the higher sampled images..... It was less of a concern when I was capturing 1m videos for RGB with the mono 290MM camera, but these 6 min RGB SERs at F18 are huge (>15GB each) and take a long time to process, hence I'm not a fan, for what might be only small gains in resolution, if indeed any.

[neil phillips]

5 minutes ago, geoflewis said:

I will continue to experiment Neil, but (and for me it's a pretty big but) I'm hating the huge file sizes and processing overhead of the higher sampled images..... It was less of a concern when I was capturing 1m videos for RGB with the mono 290MM camera, but these 6 min RGB SERs at F18 are huge (>15GB each) and take a long time to process, hence I'm not a fan, for what might be only small gains in resolution, if indeed any.

Its a fair point Geof. You should perhaps do what i do, correctly sample. Then maybe run a couple at F18 right at the end as a comparison. I also wonder if different targets respond differently

Mars Jupiter Saturn. 

[Magnum]

11 minutes ago, neil phillips said:

And dont forget higher sampling will likely work best under good seeing

That's the key point, and ive been trying to say in other threads, the top imagers capturing from Barbados or Singapore with perfect seeing can consistently use very high sampling ( some would say oversampled ), and ive also been able to gain advantage from doing that in the UK when its a perfect night, by imaging at f21-f23, but on average and poor nights I then drop down to lower sampling say f15. Some say we that ideal sampling doesnt change with seeing conditions, well in theory no but in practice it definitely does. 

[neil phillips]

BTW from a distance on my 32" 4 k. that F18 looks great

[Magnum]

by the way, nice post Geof, and nice images

[geoflewis]

2 minutes ago, neil phillips said:

BTW from a distance on my 32" 4 k. that F18 looks great

Do you mean the IR?

[neil phillips]

1 minute ago, Magnum said:

That's the key point, and ive been trying to say in other threads, the top imagers capturing from Barbados or Singapore with perfect seeing can consistently use very high sampling ( some would say oversampled ), and ive also been able to gain advantage from doing that in the UK when its a perfect night, by imaging at f21-f23, but on average and poor nights I then drop down to lower sampling say f15. Some say we that ideal sampling doesnt change with seeing conditions, well in theory no but in practice it definitely does. 

I've also found that to be true in the field Lee Quite a few times actually 

 

[geoflewis]

1 minute ago, Magnum said:

by the way, nice post Geof, and nice images

Thanks Lee

[neil phillips]

Just now, geoflewis said:

Do you mean the IR?

yes the IR

[geoflewis]

4 minutes ago, Magnum said:

That's the key point, and ive been trying to say in other threads, the top imagers capturing from Barbados or Singapore with perfect seeing can consistently use very high sampling ( some would say oversampled ), and ive also been able to gain advantage from doing that in the UK when its a perfect night, by imaging at f21-f23, but on average and poor nights I then drop down to lower sampling say f15. Some say we that ideal sampling doesnt change with seeing conditions, well in theory no but in practice it definitely does. 

I think you're completely correct Lee. I wonder what sampling rate Damian Peach uses with his rig in Selsey, do you know...?

[geoflewis]

3 minutes ago, neil phillips said:

yes the IR

I've just started processing the RGB SER that I captured immediately prior to that IR with identical focus, so it will be interesting to see how that turns out.....

[neil phillips]

2 minutes ago, geoflewis said:

I've just started processing the RGB SER that I captured immediately prior to that IR with identical focus, so it will be interesting to see how that turns out.....

That will be interesting, sharp but nosier surely? control that noise if so Geof

[geoflewis]

3 minutes ago, neil phillips said:

That will be interesting, sharp but nosier surely? control that noise if so Geof

Will do boss - at least I'll try 😉

[neil phillips]

4 minutes ago, geoflewis said:

Will do boss - at least I'll try 😉

lol you know it makes sense

[geoflewis]

Well here is an F18 RGB image captured immediately prior to the above sharp IR image, i.e. the timestamp is just 7 mins earlier. It's so much softer than the IR, yet still too noisy I think.

I don't know what to make of it, but maybe I'm just missing sharp focus operating at F18 on the RGB with the colour camera? 🤷‍♂️

[Magnum]

I found this comparison I did on Sept 4th with my old 224C, colours is slightly different between the 2 as it was only a quick comparison, and I really cant be bothered to process it again from scratch.

Anyway the left image is at prime focus with my 12" LX200 but with extra spacing the disc measured 250 pixels which works out to be F13, the right image is using my 2.5x Barlow measuring 480 pixels and is bang on f25. I have enlarged the f13 image to match the f25 image size. They were taken about 30 mins apart and conditions were pretty consistent throughout the session. To my eyes the f25 image is way more refined.

Ive since upgraded to the 462C with smaller 2.9um pixels compared to 3.75um on the 224C so ive dropped my working FL down from f25 to f21 now to get me similar scale.

the ideal sampling maybe somewhere between the 2, but I would conclude same thing Neil said, its better to oversample than to undersample

Lee

Edited November 12, 2022 by Magnum

[geoflewis]

3 minutes ago, Magnum said:

I found this comparison I did on Sept 4th with my old 224C, colours is slightly different between the 2 as it was only a quick comparison, and I really cant be bothered to process it again from scratch.

Anyway the left image is at prime focus with my 12" LX200 but with extra spacing the disc measured 250 pixels which works out to be F13, the right image is using my 2.5x Barlow measuring 480 pixels and is bang on f25. I have enlarged the f13 image to match the f25 image size. They were taken about 30 mins apart. to my eyes the f25 image is way more refined .

Lee

Nice images and good comparison Lee. Yes, I agree,  the right hand images is far superior.

[Magnum]

Just now, geoflewis said:

Nice images and good comparison Lee. Yes, I agree,  the right hand images is far superior.

on the Down sides  the f25 image took much longer to stack and takes up much more disc space and was dimmer so had to use higher gain, yet the final image still looks smoother to me.