geoflewis

10 minutes ago, Ags said:

Shot through drifting clouds; it was going to be a 6 minute sequence but the clouds thickened, so I got about 4 minutes of 6 ms subs at 100 fps at f10. For some reason my frame rate has dropped on my laptop lately???

Stacked in AS!3 with 1.5 drizzle, sharpened in RS6 and tweaked in Gimp.

Nice Mars with plenty of detail coming through. Have you tried a smaller ROI to keep the frame rate higher? 6ms should be giving you nearer 200fps. What capture software are you using?

48 minutes ago, dweller25 said:

Excellent @geoflewis 👍

Thanks David

7 hours ago, BGazing said:

This is great. That dark thingie in the polar cap is not an artefact (I was wondering when I shot Mars in my 8in), Peach's image shows it in more detail. 

Thanks and yes that dark region is real. It looks to me as if it might be the ground, with the lighter blue being cloud above and around the polar hood.

EDIT: I asked Richard McKim, Mars Section Director, BAA, who advised me that the dark area is the north end of Acidalium, seen through the polar hood.

7 hours ago, neil phillips said:

Its holding quite well. What gain was that? i had similar effect on Astro surface but not Registax. wondered about read noise. Do you normally get that  edge ?

The sawtooth edge that I’ve been getting on Mars this year is not something I’ve noticed before. However, I’ve always been at a much longer focal length, shooting shorter videos with mono RGB filters, then de-rotating and stacking them in WinJupos, to build the colour image. It may be due to imaging at F11/F12 with 6 min SERs, but I don’t really know; if anything I think it’s the smaller image scale…..🤷‍♂️

Thanks Neil, yes I resized from 96dpi to 192dpi, to smooth a sawtooth limb, which of course makes the image twice the size.

2 minutes ago, neil phillips said:

Was running a second capture at F26. 3 mins in the scope went out of travel needing a meridian flip. So added the 3 mins I got onto the existing 6 min capture i had. Did a video de rotation. Slightly harder processing and contrast. reduced to 70% in size. 

 

Well done Neil, very creative and well worth the effort.

19 minutes ago, Kon said:

Very nice Mars. Nicely processed.

Thanks Kostas, I'm very surprised how it turned out as I almost didn't bother as the sky was so foggy and Mars enveloped in a huge halo from the nearby Moon. So much so that it's thrown the colour readout of the camera off, so I had to manually force the colour with BGGR on one of the videos, when in fact it should be RGGB. The other one was correct. I've never seen that happen previously, it is very weird and I've no idea what happened.

After my session messing with different sampling on Jupiter and getting my fist Jupiter methane band image, I thought I'd try my luck with Mars. Laying close to the Moon, Mars was shrowded in brightly illuminated haze, but I opted for 3x6min SERs. However, I completed lost Mars to thickening fog during the 3rd SER, so this is a de-rotated stack of the best 10% from the other two.

Xanthe and the polar hood are well seen.

21 minutes ago, vlaiv said:

Won't work well I'm afraid.

13ms is too long and would defeat the purpose - but it does show that one needs longer exposure when using F/24.

Ok , no worries Vlaiv. I'm not sure about that, but maybe. I was using 13ms based on advice from a friend in Australia. Others suggested faster and slow fps, but I just went with that..... I'd not really thought it about it previously.

8 minutes ago, vlaiv said:

I would not mind doing it if someone shoots the movie in mono with 14" scope at twice critical sampling rate at 2ms exposure length

I have some old Mars videos (AVIs) from 2020 shot at F24 (according to FireCapture). They are mono 180s duration, but captured at 13ms. Equipment was ASI290MM (2.9mn px), C14, x2 TV PM, ADC. Any use?

5 minutes ago, vlaiv said:

In order to get same images - here is what you do.

You resize smaller image to x1.636363 size or 163.63% and then crop to the central 600px.

This will give you both same planet size and same image size (in pixels).

Thnaks Vlaiv, yes, if exactly F18 to F11, which I am not sure, but the princple is good and something for me to consider in future, if/when I want to do a comparison.

25 minutes ago, Magnum said:

If the f11 one has not been resized then yes its coming out at about f16.5 for me rather than f11

The entire image was resized from 416x416 to 600x600, but of course Jupiter was in a larger relative ROI in the smaller image. Just my hopeless attempt to make the images look similar sizes.....🙄

22 minutes ago, vlaiv said:

Here is a protocol that I would suggest for anyone wanting to compare two different samplings that will mostly make things equal.

It requires mono camera and some special processing.

We shoot single video - but we create two new videos out of it to be processed. Video is shot at exposure length suitable for smaller sampling rate but with higher sampling rate (use of barlow).

First video is created by binning each frame 2x2 and then taking every 4th frame (we discard other 3). This will give us lower sampling rate at exposure length of lower sampling rate with 1/4 of all frames equally spread over capture period.

Second video is created by summing each group of 4 frames to make output frame (stacking without alignment). This will give us higher sampling rate at  exposure length of higher sampling rate with 1/4 of all frames equally spread over capture period.

We have thus managed to create videos - each at appropriate sampling rate, each with realistic exposure length to reach same signal level, each with the same number of subs in same seeing / same conditions.

Drawbacks - recording will have x2 read noise it would usually have and we are limited to x2 difference in sampling rate (we could not do above x1.636363 example).

Next part has to deal with same processing. This is tricky as wavelets are applied based on feature size, so they must be set differently.

Thus we must create two images to be processed like this:

We stack both videos with same stacking parameters (same percentage of subs, same number of alignment points and relative size of alignment points being the same - which means that smaller sampling  rate will use half the size alignment point) to get two planetary images.

We then create two images for processing by taking smaller planet image, enlarging it x2 and putting it side by side with larger planet to form single image. We similarly take larger planet and reduce its size to half and put it next to small planet.

This way we can test processing at both sizes.

We can even create third image where we simply put them side by side without resizing and process that. My only concern is that there could be bias in processing and parameters selected so that one of the two looks better.

I think I'll pass on that......😖

35 minutes ago, vlaiv said:

Here is what I find interesting in this comparison.

First two images are supposed to be F/11 vs F/18, right?

This means that Jupiter in one image should have 18/11 = x1.6363.... larger diameter.

I've measured following diameters in two images:

If smaller Jupiter has 470px diameter - larger should have 470 x 1.63636 .... = ~769px and not 524

Difference between two images is much less than F/11 and F/18.

Noise difference is very large indeed, and I wonder if images where manipulated in some other way?

If we check the native image, at F/11 it should have sampling rate of 0.153"/px and that would make 46.2" diameter Jupiter be ~301px

Maybe drizzle x1.5 was used for that image? It would be much better fit if drizzle x1.5 was used to F/11 and F/18 integrated normally (accounting for small FL change due to primary - secondary distance change when focusing).

 

Sorry Vlaiv, I tried and failed to resize the F11 Jupiter image to the F18 image. All I achieved was to make both images including the border the same size, but clearly there was a larger ROI for the F11 image.. Here is the F11 image before I resized it.

Does the maths work now. I get F11 v F18 as that is what FireCapture reports.

6 minutes ago, Magnum said:

Thats very good for your first methane band Geof, 

Thanks Lee, I've processed it about a dozen times. Tried drizzle x1.5 too and a bunch of different wavelet settings and think this is about as good as I can get from it. Must say it's far better than I anticipated, so your PM advice yesterday was a huge help, thanks. I also spent a few hours watch Chris Go on YT yesterday to get some pointers from him. All good learning I think. Might be interresting to see what I can do with the filter under better seeing conditions and by running a few shorter vids then de-rotating the resultant stacks as Chris Go recommends.. Also next year Jupiter will be much higher elevation, so more favourably placed....🤞

I'll round of my set of Jupiter images from last night, with my first attempt at Methane band (CH4). This is at F11 with the GRS just rotating into view and some other detail coming through too.

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.

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? 🤷‍♂️

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 😉

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.....

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...?

1 minute ago, Magnum said:

by the way, nice post Geof, and nice images

Thanks Lee

2 minutes ago, neil phillips said:

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

Do you mean the IR?

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.

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.....