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From Sirius to Mars


Naz
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An attempt at a wide field of Orion / Taurus / Pleiades / Mars.

10 sec at f3.5 ISO 1600 Dslr. Origioal image in NEF Raw, Noise reduction off. processed in CaptureOne LE. The over all blue cast is due useing tempeture control to reduce the chip noise and amp heat

I have taken 10 shots and when I figure out the stacking software, I will update.

image.jpg

Feedback please and any info on useing Registax would be appreciated

Nabban

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Just interested in why you turn off the in camera noise reduction? I tried to find out on some DigiPhot newsgroups how this works and after a lot of shouting and bawling I was told that the in camera noise reduction gets rid of lots of the amp glow and chip noise. Apparently the camera takes a second picture with all the same conditions except the shutter stays closed. This gives an image of any amp glow etc. which is then subtracted from your image. This reduces the nasty colourings a lot and gets rid of the banding which often shows on DSLR images at high ISO settings.

I use a Nikon D50 so I suspect that your D70 should be similar but with obvious advantages.

BTW have you tried one of the el-cheapo catadioptric lenses yet? At 50 quid ish it gets you up close and personal with Orion and his mates, the downside is that the viewfinder is so dim it's almost impossible to point it at anything.

BTW great pictures - keep it up!

Captain Chaos

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Thanks for your query Captain C

Yes I am aware of the noise reduction, but I thought I would try with out. I have been told that the noise reduction can also delete the fainter stars and detail. It was just an experiment to see what would happen. Next time i will take two shots of the same object, one with and one without to see what the difference is.

Yes I have a 500mm f8 cat lens, which as you said is hard to se through. I will experiment with this set up later when I have mastered stacking the images.

I did take some with a 90mm f2.5 lens, but at 30 second exposure, star trails showed. Next item will be a driven mount to solve that one. Expence! Expence! Expence!

nabban

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Thanks for your query Captain C

snip

Yes I have a 500mm f8 cat lens, which as you said is hard to se through. I will experiment with this set up later when I have mastered stacking the images.

snip

nabban

Try the 500mm @ the moon, you will need a tripod to stop the shaking (well I do, Eddie aged 8 can snap away handheld with a 600mm with no shaking, must cut down on the fags and booze) but the shutter speed will be well up past 1/125th, especially as you will need to add 2 stops or use spot metering.

Captain Chaos

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Apparently the camera takes a second picture with all the same conditions except the shutter stays closed. This gives an image of any amp glow etc. which is then subtracted from your image. This reduces the nasty colourings a lot and gets rid of the banding which often shows on DSLR images at high ISO settings.

You are describing the Canon method of noise-reduction. I think you will find (it is a fast moving market!) that Nikon use the more traditional Dark-Frame-Subtraction method which does not require a second exposure. (All things considered, the Canon method is more accurate/effective).

Steve

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Thanks for all your input guys. From what I under stand about the Nikon noise reduction method is that they use something like the despeckle filter, hence the finer detail and fainter stars may be lost. Nikon do use a dark shot for dust ref. As I didn't buy the D70 with astro in mind, it was bought before my reawaking to astro. I will when ever the lottery comes up, or I can persude the financial controller to cough up look to get a dedicated astro cam / scope / mount. I think about 5 grand would just about cover it.

To be more serious for a mo, I will when I get a chance, try testing, one shot noise off one noise on, and post the unprocessed results (apart from NEF to jpeg for web use).

I wiil be useing the 500mm cat for some moon shots, gives me the same as a 750mm compared to 35mm film. Also looking to get a direct T mount for my scope and most important a motor drive.

But it all costs and takes time.

nabban

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Sorry messed up the quote :?

James, I think a registax tutorial would be very useful for a lot of people. There is a tutorial on the net for which a link has already been posted. It is for V2 and just isn't all that good. For a beginer it is ok if you just use all the auto settings and don't want to attempt any processing. The manual processing and quality options are pretty daunting. I guess some of them are for obsessives but some of them are obviously very useful. Roger is going to help me out this w/e when I pick up my scope but I am sure there are plenty of others struggling.

Martin

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