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Capturing and Processing data from an SXV-M25 with MaximDL

RichieJarvis

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RichieJarvis

RichieJarvis

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Hi All,

I've been trying to help Stephen Green out with his SXV-M25, and have run into a few problems. Have a look at the attached image. As you can see, there seems to be a gap between each pixel of the object captured - does anyone know what I am doing wrong here?

Is it something setup incorrectly during capture, or is it something wrong with the processing?

Thanks,

Richie (and Stephen!)

post-14845-133877354151_thumb.jpg

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MartinB

MartinB

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It's just the bayer matrix. It needs debayering. Maxim will do this - convert to RGB tool under the colour menu. Choose the "high quality" algorithm. I normally do this after calibrating but before stretching the histogram

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steppenwolf

steppenwolf

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I am not entirely convinced by the the XY offset argument but would love to be wrong - I use an offset with just the 'Y' ticked in MaximDL for my own M25C if you want to give that a try. Have you tried a colour convert only - i.e. no calibration beforehand, just to eliminate a problem here?

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Eddie

Eddie

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It is as Mark suggested a wrong x/y offset. Which version of Maxim are you using?

Steve, with a OSC you should apply the calibration before you debayer but you should apply a boxcar filter to the calibration frames to strip the bayer matrix. (maxims calibration routine allows you to do this)

Also see badly colour balanced image attached!

Eddie

post-13417-133877354264_thumb.jpg

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steppenwolf

steppenwolf

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Steve, with a OSC you should apply the calibration before you debayer but you should apply a boxcar filter to the calibration frames to strip the bayer matrix. (maxims calibration routine allows you to do this)

I know that! - I was suggesting NO calibration at all, just in case there was a problem with the 'dark', this would take one step out of the equation.

Pleased that the problem is just the offset though. When I got my M25C, I had to experiment with the offset and I got some great (??!!) colours but didn't notice a pattern in any of the test conversions.

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mcrossley

mcrossley

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It is as Mark suggested a wrong x/y offset. Which version of Maxim are you using?

Ithankyou! :(

Steve, with a OSC you should apply the calibration before you debayer but you should apply a boxcar filter to the calibration frames to strip the bayer matrix. (maxims calibration routine allows you to do this)

Now there's a thing. I think the opposite - well the boxcar bit anyway - because who is to say that the flat has the same profile in each colour channel? For instance with dichroic filters the band pass changes with the angle of incidence, therefore the colour balance will change slightly from the centre to the edge of the image. Normally this isn't noticeable because the bandpass changes are so small, BUT, put the filter behind an f/2 system (Hyperstar anyone? or a fast camera lens) and the colour shift becomes very obvious.

Have a look at quite a few of the Hyperstar images and you will find circular 'halos' and colour shifts in the background out towards the corners. Partly due to the diffulty in getting a good flat with Hyperstar, and partly (I surmise) due to the average colour flat being applied.

So, apply the raw flats to the image before colour conversion, or colour convert the flats and apply after the image colour conversion? Which is better? Only one way to find out.... th_fight.gif

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mcrossley

mcrossley

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Unfortunately I don't think I have any flats at the moment that are good enough to test this out, I wonder if Steve L has....?

I'd like to compare a Hyperstar image taken through a LP filter and:

1. Boxcar filtered flats applied to raw images.

2. Raw flats applied ro raw images.

3. Colour converted flats applied to post colour converted images.

Oops, sorry for hi-jacking the thread, maybe I should start a new one.

Mark

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RichieJarvis

RichieJarvis

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Thanks guys - plenty for Stephen and I to try.

Unfortunately, I don't think I kept the un-calibrated frames when I combined them. To download that image, don't click on it - right-click, and do save-as, then you'll be prompted to down it instead of your browser attempting to display it.

Sounds to me like the way forward is to play with the settings in MaximDL - its version 5.01 btw.

I think the easiest way to do this is probably going to be to use a normal lens and get things working right before astro-imaging again :)

These OSC cameras just confuse poor, simple mono-camera guys like me you know! :(

Thanks again for the advice.

Cheers,

Richie

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