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Gina

First Light Modded 1100D - M51

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All that hard work payed off :):confused::) that's a good looking sub with lots of lovely detail in there waiting to be pulled out. For my flats I leave the camera on the telescope and in the morning put a clean white cloth over the dew shield and point the telescope to a window in my shed. Set my camera to AV and take my flats that way.

So long as you don't move the camera from the night before it works fine. Reading through the deep sky stacker manual they say in there that temperature is not important when taking flats and Bias shots but it is for your dark's so I take my dark's after finishing by putting the telescope in my shed with the camera still in position put the cap on and set my timer to take 60 dark's, in the morning I take my flats and bias.

That way I can just concentrate all my time on taking subs, these are downloaded to my laptop with backyard eos and when I pack up the camera is disconnected from my laptop, but with my timer on it I can carry on taking dark's then flats in the morning and Bias shots.

I have bought two battery's for my camera as its easy to keep one charged up and ready all the time. With focus slipping issues I now focus first on a star with my Bahtinov mask and then screw down the locking screw nice and tight to avoid any slipping going on, had that happen a few nights back and got wise to it as its a pain having to refocus as you know.

I packed up at 2am last night and it looks like rain and cloud for the rest of the week so glad I stuck it out while it was clear.

What dedication you have to have to get good results doing this but its worth it to see those brilliant galaxy's and nebula.:(

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There's loads of great detail in that image, Gina.

An artificial flat will take care of the vignetting, no problem. Good tracking and plenty of signal-to-noise.

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Thank you both :) That image has come out well Zak:)

Just finished another DSS run with 42 flats added. That has certainly flattened the background etc. I'll post the result shortly.

Edited by Gina

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Look like you should have a cracker image there Gina.

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A couple of examples of post DSS processing in GIMP with flats added in DSS. First is full frame scaled for here the second cropped a bit and then scaled. I'm not happy that the flats worked properly - there still seems to be some dust shadows. The background has a gradient on it too which wasn't there on the previous run.

M51-2012-04-15-02-s.jpg

M51-2012-04-15-02-s.jpg

M51-2012-04-15-02-cs.jpg

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Look like you should have a cracker image there Gina.
Thank you :) I think I might if/when I get the post processing better.

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The histogram looks a bit clipped on the left, on the cropped image. have you adjusted the levels?

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I believe you have NGC 5198 in there, 150 million LY's distance, not something any Tom, [removed word] or Harry would capture....:))

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The histogram looks a bit clipped on the left, on the cropped image. have you adjusted the levels?
Yes. Edited by Gina

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I believe you have NGC 5198 in there, 150 million LY's distance, not something any Tom, [removed word] or Harry would capture....:))
Thank you :confused: I think I can see a couple of other distant galaxies in there :( Edited by Gina

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Yes.

It looks like you have clipped the black point too hard (though I am only using the JPEG image). Be wary of clipping it too hard...you will lose precious data if you do that.

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Thats coming along nicely Gina your processing skills are getting lots of practise with all these goes at M51, good fun as well. I love processing the images the next day really adds to the fun of imaging.

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Thanks Mark :) Yes processing is interesting probably more so than sitting in the warm room while APT and PHD did their stuff and looking at the images in Canon's DPP which showed more on RAW images than JPEG but took rather a long time to produce full resolution. I was very impressed with last night's RAW images. I could see though that 150s was about the most I could use without showing a noisy background. I shall be interested in seeing if cooling the image sensor improves that. The odd thing is that darks taken under the same conditions do not show that noise.

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I was reading that manual in deep sky stacker and it shows clearly in there that if you stack lots of darks you will get rid of the noise, they say about 30 or more but I have done some tests to see how much noise I can get rid of and finding that stacking about 60 does a nice job and the same for my subs.

If you stack 20 subs and compare that to stacking 60 you will see the noise levels drop significantly. I am no exspert on these things I just want a clean image to process with in ps and stacking 60 plus subs is working pretty good for me even though I went to all that trouble to get my guiding system working like you I find the longer the subs the more noise I have to deal with. This where a cooled ccd camera would be of benifit I guess, more money.

But most night if your only on one subject taking 60-80 short subs on a clear dark night works pretty good. I have seen several images where the subs were 10 minutes long or 5 minutes long and found my images are getting pretty much the same results with shorter subs but more of them. Again I dont understand it all but just going on what I am getting from my final images. Still loads to learn about all that but its fun learning.But noise levels go down in your subs if you stack lots of them is what I am finding and that goes for darks as well. 60 darks is better then 20 and 80 is even better still when there stacked you can see the noise levels going down.

Trial and error many times but I keep notes on what I do and compare my results to see if it makes a difference.

Edited by Quatermass

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Interesting, several people have said that over 15-20 darks produces very little improvement. I increased my darks from 15 to 25 last night but there is no reason why I shouldn't set APT to collect any number of darks after I've finished with lights. I can just close the roof, put the cap on the scope and set up APT to grab the darks while I go to bed :) I find the sensor temperature (or rather EXIF T) stabilises after a short time of running constant exposures. Last night it was 12C - probably some 10C above ambient.

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No harm in doing a test in deep sky stacker thats what i did just to see if it had any effect and it certainly did. Stacking 50 subs with 20 darks first then doing it with 80 darks 30 flats and bias reduced the noise in the image a lot. You can stack your subs as many times as you want so it pays to do a few tests and see what you come up with I think.

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Very interesting QM, i have a Cannon 1100d in the post so all the of Nikon darks,bias ect will go on the storage drive, and a new set made for the Cannon, its unmodded and unguided atm, will probably stay that way with a view next year to the new 60da, will run some tests keep you posted and Gina do a comparison to your Images (M51)to see how much more you get with fainter stars ect with a modded Camera....

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Since I modded my camera last month the images did seem a bit more noisy but not that much and stacking and testing my subs and darks has shown me how much I can reduce noise. At the moment a stack of 60 subs 60 darks and 30 flats and Bias seem to be about right but will be doing more tests to double check the noise. Of course warmer weather is going to increase the noise levels as well I guess.

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You could leave a hose pipe on it that would keep it cool...Doh....we got a hose pipe ban,,,perhaps next year....:)

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We really do need some rain but hopefully during the day only :)

Sent from my GT-S5670 using Tapatalk 2

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Absolutely!! :) Most people hope for rain at night with dry days - we're different :confused:

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