Red Blob in the Rain

[Demonperformer]

That's what I'm calling this new piece of modern art ...

Woke up 3.30, fantastically clear, got up, set up telescope, started imaging Mars ...

At 4.33, it started to rain [having lost a previous attempt at Mars because the clouds covered it for half the vid ... I should have realised at that point things were not going to go well]

I was taking 200s vids, and I never knew how long a minute and a half could be while waiting for the capture to end and wondering if the mains lead with its four-plug adaptor into which the telescope and laptop were both plugged was going to go 'bang' in the wet before it did.

Anyway, long story short ... capture ended, laptop, telescope and mains lead all indoors safely and quick processing job.

Suppose the best that can be said is that you can make out the 88% phase of the planet.

And yes, I know it doesn't look particularly red ... played with colour filters on Registax and it didn't make a lot of difference.

609/1000 frames - 1/5s - 5fps

[brianb]

Suppose the best that can be said is that you can make out the 88% phase of the planet.

And yes, I know it doesn't look particularly red

It looks to me as though it's overexposed. Once the image is "burned out" I'm afraid there's not much you can do with processing tools. The trick is to get the exposure somewhere close to but not actually saturating the sensor ... it's hard to judge but, like focusing, getting it right is one of the knacks that successful webcam operators have to acquire.

wondering if the mains lead with its four-plug adaptor into which the telescope and laptop were both plugged was going to go 'bang' in the wet

Risky. Use a deep cycle battery!

[Ant]

When imaging planets (which to be honest I'm not that good at) I've also found that underexposing leads to a much better result than using the correct exposure (when viewing the live feed).

It's a good start mate. I've always found mars quite hard to image. Also how about adding in a barlow to increase the image scale!

Cheers

Ant

[brianb]

how about adding in a barlow to increase the image scale!

Good idea if you have good seeing and some experience processing webcam AVIs. But focusing with a barlow is much, much harder than at prime focus!

[Ant]

I don't find a 2x barlow that much more of an issue. I agree that as you get to 3x and 4x (only tried the 4x times a few times) it does get very tricky. As Brian said at 3x and 4x seeing can make life very difficult.

I would still say that trying a 2x barlow won't cause you too many issues - the biggest issue I've always found with barlows is getting / keeping the object on the chip!

Ant

[Demonperformer]

Thanks for your feedback, guys.

I am in the throws of getting a 2x barlow anyway, so will give it a go when that happens. Similarly, I am looking at power packs, but will basically need two - one for the telescope and one for the laptop - the general concensus from other threads seems to be you should not try to run both from one powerpack - and will also need a converter so I can get the 15v the laptop needs from a 12v pack - this hobby can seriously attack the bank balance, can't it?

As Mars gets nearer opposition and bigger, the problem may go resolve itself somewhat.

I see the point about image brightness, my plan was to go on and try shorter frame exposure times - my best Jupiter piccie was obtained using 1/100s frames, but thought I would start with the long ones - then rain stopped play. Guess I was a bit anxious to get something on the forum as it was my first Mars attempt.

On the subject of image brightness -

Can anyone explain to me the difference in AMCAP between the brightness option and the gain option [these are the only sliders I've done much playing with]? Seems to me they do the same thing and max-brightness + min-gain = min-brightness + max-gain.

I'm sure they must do different things or they would not both be there, but don't know what it is.

Thanks.

[brianb]

one for the telescope and one for the laptop

Run the laptop off its internal batteries. You should get at least an hour driving a webcam, which will use more disk space than you have available.

[Clayton]

On the subject of image brightness -

Can anyone explain to me the difference in AMCAP between the brightness option and the gain option [these are the only sliders I've done much playing with]? Seems to me they do the same thing and max-brightness + min-gain = min-brightness + max-gain.

I'm sure they must do different things or they would not both be there, but don't know what it is.

Thanks.

The way I understand it (not that I really know )is that gain works by amplifying the signal and is on the input side (analogue) of the processor in the webcam, a bit like a mast amplifier on a TV set. Turn it up too high and it will introduce noise to the signal/picture. Whereas Brightness is on the output side (digital) a bit like the brightness or volume control on a TV (pre digital) and works by attenuating the output and will not introduce noise. I used to run with brightness up full and gain as low as I could go whilst still maintaining a reasonably full histogram (Max brightness with Min noise), but now I am finding better results in the colour by dropping the brightness to about 70%-80%

As to what settings you should use

Everyone has their own favorites which can be very different from each other and still come up with top pictures.

I would suggest that if you plan on stacking shorter avi's then keep the gain low. with larger stack sizes there is a lot more flexibility with gain.

Good luck

[brianb]

I am finding better results in the colour by dropping the brightness to about 70%-80%

Yes, you need some headroom when sharpening too. Nothing about 75% on the histogram is a good place to be.