First Astro Image Re PP: This is an image of M32 I took last Sept. after finally getting my mount back from Celestron for the third time. At the time of shooting this I was unable to...

Oknoder Loc: Western North Dakota

This is an image of M32 I took last Sept. after finally getting my mount back from Celestron for the third time. At the time of shooting this I was unable to gain anything of a usable image out of the subs, so I never posted the results. Lately I have been working on a new PP workflow using both Pixinsight and PhotoShop CS6. While Pixinsight's GUI is clumbersome and the program as a whole is not very user friendly, it is by far the most powerful PP program for astroimaging I have used to date, and I have used almost all of the mainstream options available. The sheer amount of data that it is able to pull out of the raw files is simply astounding.This is one of the reasons why I firmly believe in saving all of my NEF files.

This image is a stack of 25 images with exposure times ranging from 15-30 seconds at ISO between 1600-3200. No flats, bias or darks were utilized as I had not yet begun using this technique yet. I also had not yet found the Nikon Black Level hack. Imaging scope was a 152mm Newtonian that came free with my AVX mount. Imaging camera is a Nikon D800e controlled by a remote shutter release while sitting in a lawn chair next to the scope.

Just looking at the vast improvement I have made in a single year has gave me the satisfaction of knowing I have found a hobby that is both challenging and rewarding, especially when looking back at all the issues I have faced over the past 12 months

Matthew

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Albuqshutterbug Loc: Albuquerque NM

Wow1 very nicely done.
I am impressed that the software lets you use shots with different settings.
I assume there is a trial version?
Awesome.

Oknoder Loc: Western North Dakota

By different settings do you mean the different ranges in exposure times and ISOs? I could be wrong but I believe all programs allow this action as I have been using this technique from the beginning to help improve the signal to noise ratio. When I was doing the original research before purchasing any new astro equipment for imaging I read, can't remember where, that altering the exposures with DSLRs by time and ISO help eliminate noise and dynamic range in the same way as hdr does.

I could be wrong but I haven't gotten an error yet with a signifier pointing to this being an issue. I do use Dark's with setting similar to those of the main subs though.

Thanks for the positive comments too,
Matthew

JimH123 Loc: Morgan Hill, CA

Oknoder wrote:

By different settings do you mean the different ra... (show quote)

Great shots and processing.

I have wondered about the benefits of mixing long exposures with short exposures and have done some googling on this. DSS doesn't complain if you do it. But the question is whether you are improving the image. With long exposures, you can blow out bright areas, and stars grow fatter. And with short exposures, the bright area remain under control, but the faint stuff is not there.

So the issue is how to combine such that you retain the best of both? I haven't got this figured out yet. It seems like too much work to work in layers in Photoshop and to selectively erase to get the longer exposure version to shine through while keeping the best of the shorter exposure on top. Perhaps there is a good answer to this.

Jim

Oknoder Loc: Western North Dakota

Hmm I always figured the the software did this within the code. This image is a bad example per se, as there wasn't a whole lot of data to begin with. I plan on trying my new PP workflow on my old M42 next. We'lol see how that goes.

Matthew

JimH123 Loc: Morgan Hill, CA

Oknoder wrote:

Hmm I always figured the the software did this within the code. This image is a bad example per se, as there wasn't a whole lot of data to begin with. I plan on trying my new PP workflow on my old M42 next. We'lol see how that goes.

Matthew

I'm just not sure it is smart enough. I suppose it could be figured out with one short exposure and one long exposure and to stack them. If the stars come out skinny, its working. If they come out fat, there was no such stuff going on.

And also, there are several different stacking programs, and does one do this better than another?

Bloke Loc: Waynesboro, Pennsylvania

Oknoder wrote:

This is an image of M32 I took last Sept. after fi... (show quote)

Great job on the processing!

Oknoder Loc: Western North Dakota

JimH123 wrote:

I'm just not sure it is smart enough. I suppose it could be figured out with one short exposure and one long exposure and to stack them. If the stars come out skinny, its working. If they come out fat, there was no such stuff going on.

And also, there are several different stacking programs, and does one do this better than another?

After a little digging I think I've figured out how to program determines which are the best stars to use out of the stack. It bases its algorithm off of a setting called full width half mass (FWHM). So after calibration and alignment I'm pretty sure it uses those numbers to determine what data to reject at least as far as the stars go.

JimH123 Loc: Morgan Hill, CA

Oknoder wrote:

After a little digging I think I've figured out how to program determines which are the best stars to use out of the stack. It bases its algorithm off of a setting called full width half mass (FWHM). So after calibration and alignment I'm pretty sure it uses those numbers to determine what data to reject at least as far as the stars go.

Which stacking program is this in? I don't see a setting by that name in DSS. Under light frames, I do see:

1. Average
2. Median
3. Kappa-Sigma clipping - Pixels outside the range [a distribution around the mean] are clipped.
4. Median Kappa-Sigma clipping - Pixels outside the range [a distribution around the mean] are iteratively replaced by the median value.
5. Auto Adaptive Weighted Average - The weighted average is obtained by iteratively weighting each pixel from the deviation from the mean comparatively to the standard deviation.
6. Entropy Weighted Average (High Dynamic Range)
7. Maximum

Choice of:
No Background calibration
Per Channel Background Calibration
RGB Channels Background Calibration

- each with option to Debloom

- also some additional option on how to interpolate -- Rational or Linear Calibration Method, and then an option for RGB background Calibration Method.

I am not up to speed on just what all of these mean.

Oknoder Loc: Western North Dakota

I couldn't tell u what it means really, and it's not an option it is just one of the measurements all astro programs I researched use in determining how to stack an image. From what I read you also get a better end result if you use the image with the smallest FWHM as you first or reference image. In DSS this is what the program computes to come up with the image score, which determines if it is used in the stack or rejected.

Again this is just my understanding and I may be wrong.
Matthew

Oknoder Loc: Western North Dakota

In DSS after registering all your subs then look on the far right of the results section ( Ignore the score ). There you will find the average FWHM for your images. Odd that you cannot see it before registering, as I was under the impression that you use the image with the lowest score to reference the rest off of, as long as your composition will not be hindered by the subject being on the edge of the frame or whatnot.

Hope this helped at least clarify things a bit, as a side not FWHM is also what the programs that offer this feature use to control focus.
Matthew

CraigFair Loc: Santa Maria, CA.

Oknoder wrote:

This is an image of M32 I took last Sept. after fi... (show quote)

JimH123 Loc: Morgan Hill, CA

Oknoder wrote:

In DSS after registering all your subs then look o... (show quote)

Here is a useful link on understanding stack:

http://deepskystacker.free.fr/english/theory.htm

By the way, I cannot find any reference to any one combining short exposures and long exposures in DSS. In entry, I found reference to doing one stack with short exposures and one with long exposures and then processing them as layers in Photoshop. This doesn't sound very fun at all and would be a ton of effort.

One reason I doubt it makes sense to combine long and short exposures is that the darks are done using the same exposure time. If you combine long and short exposure times and if you had both long and short darks to go with them, there is no matching of specific darks to specific lights.

But I am still searching for a definitive answer.

Albuqshutterbug Loc: Albuquerque NM

Oknoder wrote:

By different settings do you mean the different ra... (show quote)

The ones that I have wont let me mix and match. It wants things to be static.
I'll get my act together someday and figure out how to stack singles. Mine look like a Painting by Dali when I do it.

JimH123 Loc: Morgan Hill, CA

Albuqshutterbug wrote:

The ones that I have wont let me mix and match. It wants things to be static.
I'll get my act together someday and figure out how to stack singles. Mine look like a Painting by Dali when I do it.

We have to get you going with image stacking. You will be amazed at how much more you see.