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  #21  
Old 20-05-2014, 10:29 AM
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Octane (Humayun)
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John,

Are you using a flattener?

I'm about to spend some money with Claudio...

H
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  #22  
Old 20-05-2014, 10:31 AM
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Quote:
Originally Posted by Amaranthus View Post
The standard error of the mean is inversely proportional to the square root of the sample size, so it is a matter of diminishing returns.
Good point, now that I think of it (beyond the conventions I have accepted to date). What then would be an appropriate number of darks? I use 40.
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  #23  
Old 20-05-2014, 10:40 AM
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Have to go. Work is calling. Thanks. Lot's of excellent input. Very much appreciated.
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  #24  
Old 20-05-2014, 10:43 AM
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Amaranthus (Barry)
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Appropriate number of darks depends on your exposure length and thus number of sub. If you are doing 10 min subs, you won't really want to be doing 50 darks! For short subs, I usually take up to 25 darks. For long subs, anywhere from half to equal number of darks vs subs.

(But I'm still very much in the process of what works best for me under different conditions, since I only took up the AP game recently)
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  #25  
Old 20-05-2014, 11:32 AM
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Quote:
Originally Posted by Octane View Post
John,

Are you using a flattener?

I'm about to spend some money with Claudio...

H
I am using the Flattener H, only thing I found was that if you use the standard fittings as per the System Chart, I got elongated stars out on the edges. I got Peter Tan to machine up a couple of parts that were a couple of mm wider than the standard EOS Adapter, that made the world of difference.

The image below is an 80 second shot, just a single image, gives you an idea of how the scope is performing. No Darks, Bias, Flats or Dark Flats, just a test image. The Canon 60Da.

Cheers
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  #26  
Old 20-05-2014, 11:41 AM
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Octane (Humayun)
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Excellent, John!

I've emailed Claudio asking for an appropriate mount for the DSLR (for use with an Extender-Q) and will buy the flattener.

I'll trial it out and if I have non-pinpoint stars, I'll be in touch to find more out about your Peter Tan specials.

Thanks!

H
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  #27  
Old 20-05-2014, 01:13 PM
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graham.hobart (Graham stevens)
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canon raw data

Interesting thread.
I am curious as to what software people are using to stack and whether this has any impact on the quality of the "product at the end".
In particular now I am curious as to how changing my RAW canon files to TIFFS before stacking would affect my process, plus in DSS how to stop the calibration of dark frames or opt out?
I have never stacked with anything else so would like to know what others are using (aprt from DSS)?
Graham
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  #28  
Old 20-05-2014, 01:22 PM
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Merlin66 (Ken)
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Graham,
I use AstroArtV5 for all my image acquisition with all my cameras (DSLR, Atik16 and ATik314.)
I also does all my pre-and post processing - batching of Lights/Darks/Flats stacking etc. etc. etc.
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  #29  
Old 20-05-2014, 01:23 PM
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Not sure what others use Graham but I use ImagesPlus and have from the very early versions, it will automatically convert and stack all your various subs and convert from CR2 to either FITS or TIFS.

I normally do a slight stretch in IP then import into CS6 for further manipulation.

There are quite a number of different programs out there so other people can comment on them.

Cheers
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  #30  
Old 20-05-2014, 01:28 PM
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Graham,
I am very new to this but I use DSS. DSS does accept canon RAW files but it may modify them. I use Startools for processing, and it likes the stacked file to be as unprocessed as possible.

So I use dcraw to convert RAW to TIFF as described here: http://www.startools.org/forum/viewt...67&hilit=dcraw

Startools likes the output file to be saved as FITS 32bit integer.

I have turned off any processing in DSS - can't remember it all off the top of me head.

Ivo who wrote Startools told me all of this. It seems to have improved my images.
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  #31  
Old 20-05-2014, 01:33 PM
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Hi Graham, my decision wasn't based on quality, but what worked.
I could never get DSS to work for me.
PI would stack no more than four(!) 60Da subs(18mpix) before I got 'out of memory' errors. Even then it was super slow. I spent ages trying PI memory management tips on threads etc but none worked and I gave up on PI. This was on a quad core i7 machine with 16GB ram!
I trialed AstroArt and whalla, it just worked. Very fast and I'm yet to hit a memory limit. As for output quality, no idea. It works so I bought it.
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  #32  
Old 20-05-2014, 01:34 PM
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DSS uses dcraw as its RAW decoder (get the latest 'beta'), so I'm not sure of the advantage of doing the conversion outside of the stacking program.
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  #33  
Old 20-05-2014, 01:35 PM
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Simon, did you have drizzling enabled? That is the single biggest cause of out of memory errors in DSS.
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  #34  
Old 20-05-2014, 01:40 PM
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graham.hobart (Graham stevens)
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dslr

I have always used DSS so have nothing to compare with but I have Astroart5 so may try that now.
The star registration in DSS can be a bit sus, but I have never really tweaked any of the settings from the standard except recently tried sigma and kappa stacking.
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  #35  
Old 20-05-2014, 01:49 PM
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Quote:
Originally Posted by Amaranthus View Post
Simon, did you have drizzling enabled? That is the single biggest cause of out of memory errors in DSS.
The memory errors were not with DSS but PI. And no, no drizzle.
At the time I tried DSS it couldn't handle the 60Da raws, from my dodgy memory, the output was a single pink thin vertical line. Others had complained of the same issue, I moved on.

AstroArt also uses DCraw.
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  #36  
Old 20-05-2014, 02:01 PM
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graham.hobart (Graham stevens)
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DSLR raw data

Yep- I had that with the 60Da- you need the DSS Beta version for 60Da's.
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  #37  
Old 20-05-2014, 02:02 PM
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Quote:
Originally Posted by Amaranthus View Post
DSS uses dcraw as its RAW decoder (get the latest 'beta'), so I'm not sure of the advantage of doing the conversion outside of the stacking program.
Yes it does Barry but it modifies the data. By using dcraw first with the arguments Ivo suggests it gives cleaner data.

This is how Ivo described it to me (I hope he doesn't mind me reproducing this here):

The main thing is that DSS no longer should meddle with the colour balance and should no longer create anomalous colour data in the highlights.
The problem with modifying the colour balance before StarTools can analyse the data is that any noise levels will be skewed due to the multiplication (which is what whitebalancing does) of the signal (and thus noise) in the individual channels. Highlights get clipped by the whitebalancing as well, introducing anomalous colour data in the highlights. This is why you'd want to give StarTools data that is as virgin as possible. The Tracking feature will be able to work better and will help the various modules yield better results if it can oversee the full noise evolution.


I have compared final images with using RAW or TIFF (converted first by dcraw) into DSS and the TIFF stack gave a less noisy final image with more dynamic range.

Here is an example: http://www.astrobin.com/93400/C/
A & B were done with RAW, C was done with TIFF.
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  #38  
Old 20-05-2014, 02:14 PM
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Exporting TIFFs from Canon's Digital Photo Professional will give you, in your TIFF, exactly what the sensor captured.

Using third party software will give you results, but, they will not be precise.

This can be demonstrated by opening a Canon CR2 in any number of RAW decoders (ACR/LR, CaptureOne, blah, blah, blah). None of them will render the image like DPP does. The one true Canon RAW converter.

H
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  #39  
Old 20-05-2014, 02:15 PM
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I suspect that the various products employ their own preferences, which affect the end result. DCRAW is the universal converter for many of these programs. The issues under discussion would apply universally as well, presuming that RAW DSLR data will always present unique non-linear issues.

It might be that dcraw options may differ by camera and model.
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  #40  
Old 20-05-2014, 02:32 PM
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Quote:
Yes it does Barry but it modifies the data. By using dcraw first with the arguments Ivo suggests it gives cleaner data
Paul, interesting - can you confirm that with the latest beta of DSS, which is using an updated version of dcraw. It seems strange that the dcraw conversion it uses would modify anything. I definitely keep everything else 'virgin' when using DSS - or at least as much as is possible!
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