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step_hen

Whirlpool Galaxy

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My second ever DSO image. Again this was taken using the 7inch Intes Mak-Newt at astroadventures last week, using my 400D. I took this image shortly after using the 20" Dob to view M51 visually- what a treat! Despite the short amount of astro dark this time of year, and the growing washout from the waning moon that was about to rise, i could easily make out the spiral arms with direct vision and little effort. Aperature really is king!

step_hen-albums-dso-picture5253-whirlpool-galaxy-m51.jpg

Edited by step_hen

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Very nice Stephen. Really nice colour in the galaxy and nice tight stars.

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Hi Stephen....nice image....even better colours than my 2nd DSO also. Im a newbee too....please see my M51 in album.

cheers

bob

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Thanks guys. Nice pics Bob- can you fix the gradient on the image? Love the concord shots

Stephen

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there is a lot more here than you are letting show. The background is much too dark and the galaxy can stand more of a stretch and some extra saturation.

Dennis

post-15519-13387745408_thumb.jpg

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Very nice result and lots to play with.

John.

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Great work step-hen on the caoture and great work on the reprocess all!

It goes to show that a great image can be made excellent with the right processing.

Gary

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Thanks guys, i shall give the data a few tweaks and see what i can do to compare with the adjustments above. Looking at it now, i agree the background sky is too dark. Is there any way to bring out more detail in the galaxy without leading to the 'noisy' looking background?

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if you consider the background too noisy you can darken it without touching the edge of the galaxy with careful use of curves. Noise reduction such as Neat Image will look after the rest. You have good data there, it is well worth persevering with it.

Dennis

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If the background has noise you could make a noise-reduced version of the image in Neat Image, for example, as Dennis says. Then paste it on as a layer on top, use colour select to select the background, select inverse and erase the bright stuff from the low noise version before flatteneing.

You could also select the background sky and reduce the saturation, which will help a little.

Noel's Actions for Photoshop (highly recommended) has a number of useful tools which would help as well. Colour blotch removal and space noise reduction.

What you are seeing in this project is the need for hours and hours of data. But I thnk most of us would swap our second ever images for this one!!

Olly

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Cheers for all the input from you imaging guru's! Looks like i have a lot of photoshop to learn. Quick question- no bias frames were included- would this have helped with background noise? While i'm working on the reprocess, i'll post up my M13 image!

Stephen

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Darks already contain the bias signal so if you use dark frames you should not use bias, no need to subtract it twice. If you don't use darks you should subtract bias and it will make a difference to the noise in the frame.

Dennis

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Deep Sky Stacker was used followed by photoshop CS3

Sshhh... don't tell Dennis he doesn't like DSS (being kind) he's a bit of a Maxim Evangelist...:D

When your using DSS try and make sure you have all the fames that are required for one of the alternate calibration schemes that are listed inthe help files...

I have posted the charts on here before but haven't found the thread yet... but I have found the pics...

DSS_CAL_1.jpg

DSS_CAL_2.jpg

DSS_CAL_3.jpg

Billy...

Edited by Psychobilly

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Great image, I think you've got some good definition there. I don't understand all the comments about processing, hope it'll make sense the more I read, but love the pic anyway.

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Peter and Dennis- According what you have written above , and Peters diagrams from DSS, is it then possible to take a series of lights, bias and flats without any time comsuming darks, and the end up with a properly calibrated image? If bias frames can substitute for darks, why do most folk still seem to take darks?

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Ok, here is the first reprocess using Noels actions (Great photoshop addition- just had lots of fun experimenting!)

step_hen-albums-dso-picture5289-whirlpool-galaxy-m51-v2.jpg

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Boy, some progress. Okay, no more help for you, you are learning too fast!!!

Only joking. I bet you are quietly leaping up and down and waking up the neighbours about that image. I'd have done the same but - I don't have any neighbours!

Great stuff, well done. This really is an exceptional debut.

Olly

Edited by ollypenrice

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Peter and Dennis- According what you have written above , and Peters diagrams from DSS, is it then possible to take a series of lights, bias and flats without any time comsuming darks, and the end up with a properly calibrated image? If bias frames can substitute for darks, why do most folk still seem to take darks?

If you look at the three diagrams they all have darks....

Cant get away without them...

Peter...

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wow, what an improvement. Excellent work Stephen (with a little help from Peter :D).

Edited by russ

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Stephen, re your comment 'If bias frames can substitute for darks, why do most folk still seem to take darks?'

Bias frames do not substitute for darks. Using a non-temerature controlled camera you will have a problem with darks not exactly matching the light frames in terms of the thermal pixels generated. If you can dither the mount between exposures, and it is highly recommended by all the glitterati in astro imaging, you can do away with darks as outlier rejection algorithms in the combining software will effectively get rid of the thermal pixels. A hot pixel filter will clean up any that are left behind.

With my STL I never use darks, just subtract bias, apply the flat and that's it. If you do not use darks bias is essential, if you do dark subtract bias, is included in that subtraction because bias is in every frame you ever took.

To summarise, you don't need darks for a temp controlled camera; bad pixel mapping, hot pixel filters and bias will clean up your light frames. With a non-temperature controlled camera things get tricky; If your darks do not match your lights for thermal pixels subtracting the dark can provide a poor result.

Best thing is to try both and if you can dither the mount. What are you using for camera control?

Dennis

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Dennis- I think i follow. I must admit i initially misread Peters flow charts!

For camera control i was using DSLR shutter. I was using a borrowed laptop and this was my only choice (as DSLR Focus- the other program installed on the lappy- does not currently support my 400D).

Stephen

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