Saturn disaster

[WayBig]

after getting a decent image last week, I tried again last night and it was a complete disaster....would appreciate any input anyone can give on what might have gone wrong.

I expected the conditions to be quite good, as earlier rain had cleared to give fairly good conditions, indeed through the eyepiece things looked ok, with the cassini division visible in still moments

However, on processing the avi, the results arent very good at all.

1) Reg thinks that it's a black and white AVI, and examining a single frame shows an image that appears to be B&W, whereas a single frame from last week's AVI has plenty of colour

2) Even when stacking 2000+ frames any slight tweak on the wavelets gives horrible onion rings on the image

3) The image size is much smaller than last week....is Saturn moving away from us (relatively) and getting smaller by the week?

4) The cassini isnt easily visible on individual frames, though I took as much care in focussing as I could so am not sure why this didnt show up, is there anything in the webcam settings that could account for that, could it be 'seeing'

Can I put it down to "seeing"

Here are the webcam settingd for the two days (there are some small differences in gamma and gain, but a big differentce in saturation (oops, dont know how that happened) would that be the cause of my lack of colour on the avi and any of my other problems, or does that just effect the displayed image and not the saved avi

Sharpcap settings for the bad image

Frame Rate (fps)=10.00

Exposure=-4

Saturation=-100

Gamma=16

ColorEnable=255

BacklightCompensation=0

Gain=16

Sharpcap settings last week for the good image

Frame Rate (fps)=10.00

Exposure=-4

Saturation=0

Gamma=13

ColorEnable=255

BacklightCompensation=0

Gain=23

Thanks for any comments, I thought i'd nailed it last week, but have taken several steps backwards

TIFF of 2000+ stacked frames attached which has a stretched histogram but no wavelet tweaks, and the best JPG that I can create from it

Poor Saturn.tif

[JamesF]

Which camera are you using for this?

James

[Freddie]

Not a sharpcap user, but your colour saturation has gone from 0 to -100. This may explain the B/W

[JamesF]

I'm thinking it probably does, but SharpCap just uses the range of values given to it by the windows driver I believe and they're not always intuitive

James

[WayBig]

Sorry, I'm using an SPC900.

The saturation setting probably explains the lack of colour (though I thought that it only applied to the display rather than being saved to the AVI, but that doesnt appear to be the case)

Would it also account for the onion rings and the lack of detail particularly on the cassini division?

It probably wouldn't account for the smaller size....are we moving away from Saturn now?

Thanks

[Space Cowboy]

Gain is too low compared to gamma. You need gain at least 80% with Saturn and gamma should be no higher than around 10 or even 0.

[JamesF]

We are moving away from Saturn, yes. Opposition was a few weeks back, on April 15th. I'd not noticed it getting that much smaller, but obviously it will be doing so.

I think you should try gamma at 0 and gain at somewhere around 50 depending on how bright the image looks, then experiment with various settings for saturation.

I think the onion rings and lack of detail are at least partly due to low image signal. Increasing the gain may help with that. Getting a reasonable value for saturation (I'd try anything between about 0 and 30 I think) should help with the colour. In my experience, setting the gamma to anything other than zero just causes bloating in the image and loss of detail.

James

[WayBig]

Thanks, Stuart and James, i'll try to remember the advice on gain and gamma and try that out next time....it's frustrating to have wasted an evening due to something that I should have known.

I've attached a single frame from each of the 6th and the 15th AVIs - to be sure that there was no resizing in processing, with histogram stretched just to brighten the image...both of these were taken with a x3 barlow..it's definitely shrinking!

[JamesF]

The frustration is something you have to learn to live with

I've spent well over a year working at planetary imaging with my 127 Mak and SPC900 and it's only now that I'm starting to feel that I'm getting the hang of it and producing images that are approaching the limits of the kit. I've probably thrown away dozens of hours of captured images that I decided just weren't good enough when I examined them in the cold light of day. It's not so bad when you get a run of clear nights, but if you're only getting one every couple of weeks it is seriously frustrating. And then it comes right and delivers something like this, of which I am quite proud:

At that point it all becomes justifiable

James

[Space Cowboy]

Thanks, Stuart and James, i'll try to remember the advice on gain and gamma and try that out next time....it's frustrating to have wasted an evening due to something that I should have known.

I've attached a single frame from each of the 6th and the 15th AVIs - to be sure that there was no resizing in processing, with histogram stretched just to brighten the image...both of these were taken with a x3 barlow..it's definitely shrinking!

Chris Its worth a teaspoon of gamma with Saturn to bring out the C-Ring though as James says too much gamma and things go wrong. I would try some avis with 0 gamma and a couple with about 10%.

When I got my best Saturn shots last year with the 250 Dob and Spc 900 I used over 90% gain. Ideally you want the fastest exposure time possible with a histogram of around 40-50%.

Saturn has not shrunk that much the left image looks quite large for a 3x barlow shot?

[WayBig]

Doh, schoolboy error, I had saved my more successful settings in a sharpcap profile, selected them on the menu but forgot to press "load" - so I got the default settings with zero saturation...

I'm not familiar with the histogram settings in sharpcap - is it the setting on the "Transforms" menu - then slide the "Black Threshold" up to 40-50%?

[Space Cowboy]

Yep thats the one.

To be honest i always leave saturation on its default setting. You can always raise or lower saturation during processing.

I had great sucess adding a extension tube to the 3x barlow....getting up to f25 really makes a difference especially with the cassini, provided seeing is good.