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My very first astro images

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#1 jerry10137

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Posted 07 April 2013 - 07:43 PM

After much research and collecting the right range of equipment for me, I have successfully captured my first batch of light frames from a Canon DSLR 1000D (modified). I got so excited in the hustle of working in one session that I didn't take any flats or darks. Still not quite sure how to take flats or if they are even needed. Anyway, I'm still learning the processing techniques so if anyone here wants to play with my stacked tiff's, let me know how to get them to you. I'd love to see what some of you can come up with. I have M13, M81 and M82. They will not be the best but I'd like to see what they are capable of.

Thanks in advance.

#2 Falcon-

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Posted 07 April 2013 - 07:45 PM

Sure - if you are able to post them online and link in the forums I am sure a few people will take a stab at it. :)

#3 hopefulap

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Posted 07 April 2013 - 08:46 PM

First - welcome to CN. Can you post a link to the files? I would like to see your first astrophotos.

#4 jerry10137

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Posted 07 April 2013 - 09:05 PM

Well....I'm having a hard time finding a place to host such a large file. Do you have a suggestion?

#5 jerry10137

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Posted 07 April 2013 - 09:07 PM

They were taken with a Canon 1000D Modified and a C9.25 Edge HD. It was a viewing session that quicky turned into a short time photo session because the skies opened up real nice.

#6 hopefulap

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Posted 07 April 2013 - 09:10 PM

I believe that a site used quite frequently amongst the members of CN is astrobin.com. If I remember correctly, it offers up to 500Gb of storage

#7 srosenfraz

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Posted 08 April 2013 - 12:07 AM

Well....I'm having a hard time finding a place to host such a large file. Do you have a suggestion?


Congratulations on taking your first astrophotos, Jerry.

For posting your stacked tiffs, you might want to try Dropbox.com. You can store up to 2GB for free. After uploading your file, you'll need to share the link (it'll copy the URL to your clipboard).

Also, as far as darks, flats, and bias frames - I would encourage you to work these into your imaging routine as early as possible. They're confusing at first, but once you learn how to take them, it takes very little effort. You will absolutely be able to have better results using calibration frames, so there isn't a great reason to struggle with less than the best starting point.

Here's the basics for taking your calibration frames:

Darks - Whatever ISO and sub exposure length you use for your light frames, take dark frames at the same ISO, the same sub length, and with the temperature closely matched to your lights (+/- 5 degrees F ambient is usually plenty close enough). For this reason, common practice is to take your dark frames in the middle of your imaging session or at the end of the session (many people will take them as they're breaking down their equipment). In general, you're best to take a minimum of 5 darks, preferably between 10 and 30 is better. You take many dark frames so that you average out the noise within the dark frames themselves. There's little reason to take more than 30 darks. All you do is to cover the scope or lens, and shoot however many darks at the same ISO and subexposure length (again, at a similar temperature to your lights).

Bias frames - These are frames taken at the same ISO as your lights, preferably similar temperature (although its much less critical than it is for darks) and for the SHORTEST time your camera can image. For many cameras, this is around 1/4000th second. As with your dark frames, cover up the lens or scope, and fire off your bias frames. Because they take very little time, I would encourage you to shoot around 30 of them.

Flats - These are the trickiest calibration frames. What they are used for is correcting vignetting and/or dust motes on the sensor and other things that cause uneven illumination of the sensor. They are VERY important for optimal results. I always shoot twilight flats, as it doesn't require any special equipment and twilight usually gives you an even illumination source (which is the key to good flats).

Because the flats are used to characterize your optical train, its important that you don't change the telescope configuration after shooting your flats (i.e., don't rotate the camera for better framing). If you rotate the camera in any way, then your flats are not valid, and you're better off not using them. Ideally, you want to have your focus very close to your imaging focus, as a significant change in focus will also invalidate your flats.

Ideally for flats, you're best to use the lowest ISO that your camera has (typically ISO 100). This is because it will leave your shutter open for a longer time and give you a higher signal to noise ratio in your flats. However, some programs require that the ISO be the same as your lights (I believe DSS requires this). If unsure what your software requires, shoot your flats at the same ISO as your lights.

Once you decide upon what ISO to use for your lights, set the camera for Av mode, point the OTA at the zenith just after sunset, or a little before sunrise and note what shutter speed it says is the proper exposure. That is the shutter speed you'll use (some programs such as Images Plus can capture your flats using Av mode - if your program supports this, then use that setting, otherwise check the correct exposure with the above procedure). Now that you know your shutter speed, set your camera (or camera capture program) for that shutter speed and fire off 20 to 30 flats frames. While the camera is capturing the flat frames, keep the OTA moving a little bit so that any bright stars in the field are spread throughout the flats.

Again, it sounds a little complicated when you first hear how to do it. However, after you do it one or two times, it'll become second nature to you.

Hope this helps.

#8 jerry10137

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Posted 08 April 2013 - 09:28 AM

Wow!!! Thanks so much for all that helpful information!

I will look in to posting my stacked tiff images tonight. There may not be much technique to them because they are only light frames. And, they were stacked in DSS using the register images option and all defaults.

I now see how rewarding this can be and now officially hooked.

#9 srosenfraz

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Posted 08 April 2013 - 03:45 PM

Wow!!!
I now see how rewarding this can be and now officially hooked.


Well, then be prepared to dig deeply into your savings account!

:-)

#10 jerry10137

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Posted 08 April 2013 - 06:16 PM

Here is the stacked tif of M13.

These are only light frames stacked with DSS defaults.

20 @ 45 seconds
5 @ 60 seconds
5 @ 90 seconds

https://www.dropbox....zm72o5j/M13.tif

#11 jerry10137

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Posted 08 April 2013 - 06:19 PM

M82

20 @ 30 seconds
10 @ 45 seconds
5 @ 60 seconds
5 @ 90 seconds

https://www.dropbox....h7n23kk/M82.tif

#12 jerry10137

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Posted 08 April 2013 - 06:23 PM

M81

Same as M82 on exposures

https://www.dropbox....pmegeoq/M81.tif

#13 Falcon-

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Posted 08 April 2013 - 07:54 PM

Here is a quick process of the M13 stack. The colour blotches (residue of hot pixels) should go away with the use of Darks for future shots. For this one you might try a kapa-sigma stacking method to see if it is able to remove those hot pixels.

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#14 jerry10137

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Posted 08 April 2013 - 08:04 PM

Did we really pull out a smaller galaxy there to the far left?

Given the time, equipment and so many steps missed, that doesn't look bad at all. Thanks for doing that!

#15 Falcon-

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Posted 08 April 2013 - 08:13 PM

Yep - that is a faint background galaxy! :grin:

#16 Falcon-

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Posted 08 April 2013 - 08:16 PM

Here is a quick go at your M82 stack. Again the colour streaks are residual hot pixels and so alternate stacking may remove them (and good darks certainly will!).

I think the focus was likely a bit softer on this one then it was on M13. It is often not a bad idea to check focus on a nearby bright star when switching targets just in case. I know I have been caught out by forgetting to check focus more then once.

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#17 Falcon-

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Posted 08 April 2013 - 08:39 PM

Lastly here is M81. I pushed this one too far in my stretches so the noise in the image is very obvious - I did so to show off that you DID manage to capture the faint outer arms and a few of the active star-forming nebulae in M81 :grin:

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#18 jerry10137

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Posted 08 April 2013 - 08:49 PM

That is soooo awesome.....thanks so much for that! That gives me a very good idea of what we are capable of here. I can observe with the best of them but this was my very first go at imaging and now I'm super excited....

#19 srosenfraz

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Posted 08 April 2013 - 09:14 PM

Nice work on this data, Sean - very generous of you to give Jerry a hand with this.

#20 jerry10137

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Posted 08 April 2013 - 09:26 PM

Falcon,

I really appreciate you doing that as I don't even have a copy of photoshop yet or any type of software for editing the image. Would you be so kind as to maybe briefly describe the steps and software you used for the "quick and dirty" process? Or maybe can you point me to a helpful tutorial that would be easy to follow for beginners? Thanks a lot for your time.

I've searched and found some tutorials but they all use different software. Photoshop is just too much. Yes, I spent some cash on my setup but I'm not buying photoshop. If you could give a brief overview of what you did here it would be very helpful. Again, thanks so much for your time.

#21 Falcon-

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Posted 08 April 2013 - 09:56 PM

Would you be so kind as to maybe briefly describe the steps and software you used for the "quick and dirty" process?


For my initial take on each image I used PixInsight to do the processing. PixInsight is an extremely powerful imaging package, but has a fairly high initial learning curve.

For a bit of a simpler procedure I have re-done the M13 image in Nebulosity. Nebulosity does pre-processing and stacking similar to DeepSkyStacker (only slightly less automatically) but it also does camera control for actually capturing the images and has some handy post-processing tools. There is a trial version of Nebulosity you can download. It is fully functional but adds random lines into the image as you work. The lines are not bad enough that they get in the way so you can certainly download it and give this process a try.

I actually think this version ended up better then the PixInsight version, but only because I did not take the time to get the colour calibration correct in PixInsight. Using slightly different settings in DSS may help you get a better initial colour balance so you do not need to adjust quite as much.

So here the process I used. This is not necessarily the steps needed for ALL images but it is a good starting point

0) Save the output image from Deep Sky Stacker as 16bit-per-channel instead of 32-bit-per-channel (many applications, including Nebulosity, do not like DSS's 32bit TIFFS). In my case I used PixInsight to open the 32bit version and re-save as 16bit.
1) Open Nebulosity and load up the M13 image
2) In the top-right is a tool box called "Display". This lets you make rough view-only (non-permanent) adjustments to the image that can be helpful in evaluating images, especially during capture, but in this case we want to see the image as it actually is. Turn off the "Auto" checkbox and set the B and W sliders to their home positions (0 and 65535)
3) Image Menu -> Auto Color Balance (not always effective, but worked fine here)
4) Image -> Levels / Power stretch. Move the Power slider towards the left (I used about .4 in this case)
5) Use the mouse to select the entire image *except* for the fading outer edges. Go to Image -> Crop. (this is to remove the area on the edges where not all images overlapped, producing little dark/gradient strips)
6) Image -> Curves. Change the curves to brighten MOST of the image but darken the background a bit (I used the Keller Ha preset as a starting point and then draged the lower-right side handle down till I had a dark-ish grey background
7) Image -> Adjust Hue/Saturation. Increase the saturation (S value) to suit yourself. I used about 0.7 in this case
8) Image -> Curves. Make some SMALL adjustments similar to our first curves adjustment. Do not make the background TOO dark or you loose the fainter stars and items like the faint galaxy on the left.
9) File -> Save JPG file as Displayed if you are totally done or save as 16bit TIFF or PNG if you want to move to some other app to continue editing.

After that I used Mac OS X's built in Preview.app to reduce the file to less then 800px wide and less then 200k in file size to comply with the forum's image posting guidelines. Result is attached here.

Attached Files



#22 jerry10137

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Posted 08 April 2013 - 10:12 PM

I really appreciate you taking the time to explain that. You have been very helpful! Thanks a ton!

For those that would like some detailed info here.....what happened is we had a local star party and the public showed up at. We were feeling a bit down because it was partly cloudy but a few of us hardcore decided to make an all nighter. Well..about 1am the sky opened up and most of the folks had left. There I was with a dark sky ready to take some test shots with my new equipment. To make a long story short I was very unprepared because it was more of a fellowship type of star party.

C9.25 Edge HD on a CGEM DX mount. The polar alignment was just a basic 2 star with 3 calibration stars added. I watched it for about an hour and it was tracking pretty decent. No autoguider but I do have an SSAG on order.

Canon 1000D (modified) using a fresh copy of BYEOS. Had a another colleague there even trying to show me how to use that. Remember, this was a first time for all of it.

We just started snapping subs until I ran out of darkness. I should have snapped darks but I never did. I will next time. I also have some subs of M51 but they will not stack. DSS tells me that there is no consistent star to lock on to and that only 1 of the subs is saveable. In any case, these are better results than I expected and I am very proud of my first astro image.






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