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C4 - Iris Nebula with DSLR (unmodified)


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Last night was a bit of a miracle, there was more clear sky than predicted! I set everything up at dusk expecting to be able to do nothing more than practice polar alignment, but I actually managed to get some imaging in as well!

Admittedly I had to spend the first half of the night fighting SGPro in order to convince it to actually let the guider settle before opening the shutter again. The first hour of subs needed to be thrown away as they all had lines where PHD was trying to bring the guidestar into the right place after dithering, but SGPro has waltzed on ahead. It turns out that the integration of Sequence and Equipment Profile in SGPro is unclear and byzantine.

I managed to capture some of the dark dust surrounding the brighter nebula which I am pleased about. There is still a bit of a gradient from top to bottom, but I could not decide if it was more dust, so I decided to leave it in. The centre of the nebula is completely blown out unfortunately, I tried to take some shorter exposures, but even at 60 seconds, the core was blown out and I was getting no nebulosity at all.

Lights: 21 x 300s @ ISO400

Darks: 112 x 300s

Bias: 492

Flats: 54 x 1/8s

32760386254_31a2cc5dc0_c.jpg

C4 - Iris Nebula by frugal10191, on Flickr

Mount: Skywatcher AZ-EQ6 GT

Imaging Telescope: Skywatcher ED80 DS-Pro with 0.85x FF/FR

Imaging Camera: Canon 60D (Unmodified)

Guiding Telescope: Skywatcher ST-80

Guiding Camera: Starlight Xpress Lodestar X2

Software: Sequence Generator Pro, PHD2, PixInsight

I also tried to image the Elephants Trunk as some people have had success with unmodified DSLRs, but the 10x300s subs I managed before the clouds rolled in show no signs of nebulosity when stacked ;(

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Looks great. But it seems strange that the core is already blown out at 60 secs at iso 400.

Succes on a Ha target with an unmodified dslr is very much dependent on camera make and model. The manufacturer's choice of which wavelengths to block and the sensor's spectral response determines the outcome. I have had some succes with 7+ minute exposures on bright Ha targets (california and north america nebs).

Good luck

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Great start,

but I agree with Wim that it is odd that the core would be blown out. Maybe it is not really blown out, just smeared out by the atmosphere and possibly by poor guiding or focusing. I have a 60Da (so same camera but more Ha sensitive), and you can see what I got from 39 x 480s on a ES127 ED running on its native f/7.5, all at ISO1600.

So, I cannot imagine that the core in your subs is blown out at ISO400. Did you protect it with a layer mask while you stretched the image?

http://www.astrobin.com/278815/C/

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I was a bit surprised as well. SGPro had a definite spike on the right hand edge of the histogram indicating that the image had got some blown out pixels. If I open the RAW file in Photoshop it shows the centre of the nebula as 255,255,255. If I open it in PixInsight the Image Statistics show the Maximum as 15306, which is just slightly lower than the theoretical maximum of the 14bit sensor of 16384. If I then look at one of the 300s images, the Minumim, Mean and Median pixel values all go up, but the Maximum stays at 15306, which confirms that is as high as the sensor will go depite only being 93% of the theoretical full well value. Curse you Canon, first you take my Ha sensitivity, now you take 7% of my dynamic range ;)

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Well, the centre of your core and some of the stars will be 255,255,255, but it should not be as much of the centre as it looks like in your image. As far as I know it is the same sensor in my camera as in yours.

Edited by gorann
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Very nice effort given what you had to put up with.

I imaged this briefly last year when i had an ED80 Pro, i also used a canon 60D as i didn't have my Modded 600D back then, here is my 2 hour cropped effort.

 

ngc7023.png

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Yes, that background sky looks overstretched since the "blue-green mottle" typical of DSLRs is quite visible. Also, for this object you probably aim at 5 h total exposure so do not worry yet. Now, just make sure that you got the focus right (I assume you use live view on your camera at 10 x on some nearby star that you can see in live view).

I am very happy right now since clouds are gone and I started exposing for the first time in a month. The Sky Quality Meter show 21.2. I am going for the Leo Triplets, and maybe later for the Sombreo.

A good video tutorial on noise for us DSLR users is this one by Tony Hallas (in case you have not seen it):

 

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1 hour ago, gorann said:

Yes, that background sky looks overstretched since the "blue-green mottle" typical of DSLRs is quite visible. Also, for this object you probably aim at 5 h total exposure so do not worry yet. Now, just make sure that you got the focus right (I assume you use live view on your camera at 10 x on some nearby star that you can see in live view).

I am very happy right now since clouds are gone and I started exposing for the first time in a month. The Sky Quality Meter show 21.2. I am going for the Leo Triplets, and maybe later for the Sombreo.

A good video tutorial on noise for us DSLR users is this one by Tony Hallas (in case you have not seen it):

 

The noise on the DSLR is the bane of my life, but until ebay changes their pesky rules about me selling my own organs, a CCD is not on the cards ;)

I shall have a look at that video a bit later, but like yourself, there is a break in the clouds so I am trying to get some more data tonight.

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41 minutes ago, gorann said:

Good luck tonight Frugal!

The Met Office promised that the clouds would not come any further north than the M4, they were wrong... I managed a single 5 minute sub before the clouds rolled in. :clouds1:

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20 minutes ago, frugal said:

The Met Office promised that the clouds would not come any further north than the M4, they were wrong... I managed a single 5 minute sub before the clouds rolled in. :clouds1:

Rolling in here to just now but could be temporary, I hope.....

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Regarding your image, you obviously had not blown out the core so now you "just" need the clouds to go away so you can get more data = less noise.

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