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DSS and longer exposure


SCh
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New to the forum so hello all and please excuse if I am breaking protocol, putting in the wrong place etc.

I am moving into tracking and can gain longer exposures now, having been using DSLR on shorter exposures using the 500 rule. As a result I am used to taking hundreds of images and stacking them. Longer exposures, new world. I have been taking 30 second exposures, perhaps 30 at a time but when I stack them in DSS I get a white screen. I have increased the star detection threshold and it has worked at times but not consistently. 

I am imaging with a Canon Eos 550d ISO 1600 f5 100mm fl no telescope,

What am I doing wrong?

What do people think would be optimal balance between exposure,  ISO, etc for the brighter DSOs like Hercules cluster and the link.

Any suggestions welcome.

Steve

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Hi and welcome.

After you've stacked there will be a histogram that you'll need to pull down. I'm busy stacking last night's imaging run so I'll update this post once it's finished.

 

UPDATED: I'd imagine your stacked imaged looks like the first image here. On the bottom left you'll notice the histogram has been moved to a more suitable position.

histogram 1.jpg

histogram 2.jpg

Edited by geordie85
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Thank you both for this I will try. Sadly my result seems so white I do not have a trace of the histogram on screen. Rather I have the left hand luminance curve but no red green or blue curves.

Is my set up wrong?

Update!

I have switched the RGB colour calibration off and I have colours. Have also followed your advice above and I have an image.

Trying another now will post what happens.

Thank you.

Edited by SCh
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When taking the images you should check the histogram then. Your ISO should be driven by the histgram for the exposure length used. You want the histogram 25% in from the left edge when looking at it on your camera. It might just be for your light pollution you have over exposed your images at ISO1600. Look at an individual sub where is the histogram?

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The Histogram is way over to the right thanks, I will experiment with the ISO. I am getting stars now, a fuzzy Great Cluster in Hercules, but not very many stars the background is washed out and I think stars are lost in the glare. Luckily I can drive out to a darker area. The camera I am using is modded, does this make it more susceptible to Sodium Light Pollution? Thinking is the orange nearer to the red end of the spectrum?  

I live in a semi rural area but the Local Authority, with the best of intentions for most but not me, have installed what seem to be amazingly bright sodium street  lights. The whole area is bathed in a lurid orange glow. Totally ott!

Thanks I will try lower ISO, and also experiment out of the glare.

I was setting up in the garden for convenience with the mount bring new.

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Thankfully seeing as you used ISO 1600 you have room to drop that. If the lights are sodium you could consider a filter. I use a 2" baader neodymiun filter with a step down ring to attach to my camera lenses, I have various step rings so the filter can fit all my lenses.

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Guest Tuomo
18 hours ago, happy-kat said:

When taking the images you should check the histogram then. Your ISO should be driven by the histgram for the exposure length used. You want the histogram 25% in from the left edge when looking at it on your camera. It might just be for your light pollution you have over exposed your images at ISO1600. Look at an individual sub where is the histogram?

Dont you think 25% from the left is bit too low? The way I see it,  you should avoid underexposing AND overexposing image. Everything between is ok.

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