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M13, reprocessed

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#1 Augustus

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Posted 17 July 2019 - 11:21 AM

Of the three deep-sky astrophotos I've done this is the first of them, and the first that I've really finished and decided I'm happy with - odd considering it lacks a flattener or guiding and has the least amount of data. Since it's a globular though, the SNR is rather good which probably explains that.

 

Since originally posting this I've figured out how to improve my deconvolution, desaturate the noisy background and improve the white balance/saturation of the stars.

 

m13raw717_ABE_cropped.jpg

 

Full resolution photo on AstroBin

 

Technical card on AstroBin


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#2 scadvice

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Posted 17 July 2019 - 12:05 PM

I think I recall your first M13 processing. This is better IMO.

 

When I first started I didn't spend enough time when imaging on focus. Now focus is my primary goal as the final image is extremely dependent on that. Everything else seems to be secondary. I check focus sometimes three or four times now during a session. I currently use a Bahtinov mask but even this requires some skill to be developed.

 

I have an auto focuser which allows me to come to the focus point from both directions and count the pulses on each (minus any backlash). This way I get a pretty good center of the focal length to use. The auto focuser I have has a automatic method to adjust focus but I have not had time to learn it yet.

 

A friend who uses BackyardEOS blows the image way up and has a clear fine lined mm ruler he tapes temporally on the screen to check the center spike with. He also is coming in from both directions. Checks the full distance each direction and divides by two then moves by that final number into position.

 

All in all I'm seeing an improvement in my images and developing more repeatable results by concentrating on focus as a priority before starting and during the imaging session...

 

An example is linked below taken with the same DSLR (T3i mod) as yours. 

 

https://www.astrobin...415019/?nc=user


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#3 the Elf

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Posted 17 July 2019 - 02:00 PM

Nice job. The object is a bit small for your focal length. I recommend the book "the 100 best astrophotography targets" by Ruben Kier for the start. It is orderd by date and contains objects of all sizes including tips for photography. As the book is 10+ years old you will soon be able to achieve the same results with low priced equippment today. From my experience with the T3i (unmodded and mono modded) you can go for ISO 800 and take twice the exposure time. This lowers the amount of subs to process and gives you more dynamic range. Other than that I recommend a Bahtinov mask for focus. Most objects require much longer over all time, often several nights. When I started, I was impatient, too. For M13 3 hours should bring out a lot more details and lower the background noise.


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