Calibration in DSS..... Is it doing it wrong?....RESPONSE FROM LUC OF DSS

[martin_h]

My brain is still going haywire trying to get my head around the idea that you need a light frame (of some sort) to make a master dark. If Maxim doesn't need this approach why would any other software need it?

Dennis

That is exactly the problem! it doesnt deal with calibration frames in the way that is generaly accepted.

It sort of does everything on the fly so you need to run a stacking routine to get a master out of it.

If you try to just load darks or flats or bias frames on their own and try to calibrate them it doesnt work - it will only stack if there is a light frame(of some sort) which is the cause of the original problem I think.

[martin_h]

Aplogies if my frustration with trying to understand some aspects of DSS is making me less than my normally undiplomatic self.

Dennis

My turn to apologise - it seems there is a way to stack calibration frames- its not so simple or obvious - load a set of frames - say dark frames as light frames, go to the stacking settings tab and select "no alignment" as the alignment method(all the other methods rely on stars for alignment - hence the "light frame" in the earlier statement. while in the settings tab under the light tab select "median".

Not intuitive, obvious, or indeed user friendly, and I suspect, futher muddies the water.

[RobH]

[quote=roundycat;1695227

Aplogies if my frustration with trying to understand some aspects of DSS is making me less than my normally undiplomatic self.

There can't be any copyright on a simple mathematical approach to dealing with image calibration so why the hell do some people go to the trouble of finding ways to do it differently?

Dennis

Dennis...if you suddenly became super diplomatic I'd think you'd been hijacked by aliens :D;)

I think that people find ways of doing it differently because they don't properly understand the way it works, at least, that's the only logical reason I can think of, however, I assume the DSS guys know what they're doing.

Cheers

Rob

[martin_h]

He's not the only one confused by it all...I dont pretend to understand the maths or logic behind all of this apart from the basic principals, but it would be nice to come up with a working model that can make DSS do what it is supposed to do, ie chuck everything in to the mix, hit the button and out pops a registerd, calibrated, stacked image frame.

[Demonperformer]

it would be nice to come up with a working model that can make DSS do what it is supposed to do, ie chuck everything in to the mix, hit the button and out pops a registerd, calibrated, stacked image frame.

Where would be the fun in that;)?

[martin_h]

[blinky]

So would it not be best to....

Load in Dark frames, mark them as light, median stack

Load in Bias frames (as Bias frames), Load in Flat frames, mark them as light, median stack

Load in light frames, load the Master Dark, Master flat and then stack.

Would that be the proper way to do things?

[jgs001]

So does this mean, that the way I'm using DSS is producing results that are not properly corrected ?

I load an image... (whatever I have handy, although normally a light), all my flats and the master bias (from previously, although if I wanted to create a new master bias, I'd do all the bias too). Stack it, creating a bias corrected master flat. Clear the list, load my lights, darks and master flat, and let DSS do it's thing on all the frames.

If I was combining multiple nights data, I'd create that nights master flat in the same way, but then load up my saved file list, and add the new nights data to a new group.

[Psychobilly]

Perhaps the best place to ask these questions is the Yahoo_DSS group....

Billy...

[RobH]

So does this mean, that the way I'm using DSS is producing results that are not properly corrected ?

I load an image... (whatever I have handy, although normally a light), all my flats and the master bias (from previously, although if I wanted to create a new master bias, I'd do all the bias too). Stack it, creating a bias corrected master flat. Clear the list, load my lights, darks and master flat, and let DSS do it's thing on all the frames.

If I was combining multiple nights data, I'd create that nights master flat in the same way, but then load up my saved file list, and add the new nights data to a new group.

No, it sounds like you're doing it right.

Peter, I agree that at this point it's a matter for discussion on the DSS forum.

Cheers

Rob

[roundycat]

I really have never seen or heard of anything quite so daft. I wonder how many finished images could look a lot better if the DSS writer/s had used a common sense approach?

Dennis

[BlueAstra]

I must admit I am one of those people who throws lights, flats, darks and bias into DSS, and after selecting preferred options, lets it get on with it. I can see now that this may not be the right thing to do, and illustrates my lack of understanding of this process and some of the terms used. I think it would be really useful, and benefit a lot of users, if someone could compile a simple summary step by step process list specifically for DSS users based on the discussion here. Maybe it could become a sticky for 'preferred' DSS processing.

[RogerTheDodger]

As I'm just starting out I'd appreciate that too

[martin_h]

So does this mean, that the way I'm using DSS is producing results that are not properly corrected ?

I load an image... (whatever I have handy, although normally a light), all my flats and the master bias (from previously, although if I wanted to create a new master bias, I'd do all the bias too). Stack it, creating a bias corrected master flat. Clear the list, load my lights, darks and master flat, and let DSS do it's thing on all the frames.

If I was combining multiple nights data, I'd create that nights master flat in the same way, but then load up my saved file list, and add the new nights data to a new group.

No you are doing it the correct way

[jgs001]

thanks for the confirm guys... and that also explains why when I used bias and flats in the way you'd expect I got some very odd results...

[narrowbandpaul]

I admit that I too use DSS. I liked the fact that you just threw images at it and it did the business. I assumed that the guy who wrote knew what he was doing. Clearly not.

So I think I will ditch DSS, as the number of subtractions that are performed is more than is neccessary which will add noise. What a stupid method. I will inform my friend in the states who really knows what he's talking about when it comes to CCD imaging. Im sure he will have a few words to say about this....

I have a 90 trial of maxim, so if that works nicely, which im sure it will, then a purchase of a real programme like maxim will be required.

DSS fail!

paul

[RobH]

I'd be very interested to see what he has to say Paul.

It would be nice to be able to summarise this properly and then contact the DSS designers.

Unless they are particularly precious, it may well halp them improve the program, which is great in the faxct that it clearly is useful for many people who can't or don't want to, invest a lot of money in Maxim or the like.

Rob.

[dph1nm]

As far as I am aware, DSS does allow for scalable darks. So you do have to subtract the bias from the dark (although you might prefer to do it only when you have to)!

NigelM

[dph1nm]

If I have one bias, one dark and one light, and I subtract the bias from the dark, then subtract the resulting bias-subtracted dark and the bias from the light, this is the same mathematical procedure as subtracting the original dark from the light. No extra noise is added. I can make the same argument for N x bias and N x dark. So where is DSS going wrong?

NigelM

[Dangerous-Dave]

Fascinating thread.

I wish getting the calibration slightly wrong was the limit of my problems with it. I seem to constantly get a very soft image that looks like it's been run through a median filter but damned if I can find out where it's happening. Simple answer - use Maxim!

[RobH]

OK....Two things now need to happen.

Firstly, any untoward bashing of DSS needs to stop.

For the record, I think that the guys who write DSS are to be applauded.

They have come up with a program that many use very successfully, at no financial benefit to themselves, and it must be a heck of a job writing a program like that.

Secondly, for the authors of DSS to be brought in on the discussion as we are now going round in circles, and they may well be able to provide answers that will finally clear up any confusion.

Without knowing how the DSS algorithms work, we are shooting in the dark.

Cheers

Rob

[martin_h]

I have posted a link to this thread on the DSS yahoo groups for discussion, so hopefully we will get a definitive answer.

[RobH]

I've just emailed the DSS owner too

[Shibby]

Well said. I like DSS very much, but then I am... Biased... (pause for effect). It's made at least one step of the difficult process of learning deep sky imaging much easier, and I see no reason why not to continue using it.

Thankyou all for this thread, I'm learning much! The way I understand it then... (or at least the way I will use it from now on)

Stacking images using DSS:

1) Load flats, bias frames, and a dummy light.

2) Stack

3) Clear the list

4) Load lights, darks and master flat (from 2)

5) Stack

6) Job done

Sorry, I think I'm just reiterating, and as you say Rob, shooting in the dark (another pun? )

[RobH]

Didn't even realsise I'd made a pun :D