CCD Camera decisions - Mono vs OSC, FOV, Filter wheel etc...

[MikeWilson]

Thanks Rob and Tony for the info and food for thought!

[ollypenrice]

Coming back to Nadeem's point about the possibility of using a DSLR to get the colour, I can see the logic. However, for some reason DSLRs seem to be pretty hopeless on star colour. Do others agree? I have no idea why this is but it is something I often notice even in good DSLR pictures. So for this reason it is not something I would budget on doing. This is a good M42 but the stars are very white.

Deep Sky Astrophotography by Frans Kroon M42

Our Atik 4000 OSC is excellent on star colour. As I've said before, using it alongside its mono equivalent does not, in reality, produce very predictable results. Sometimes it performs briliantly, sometimes less well than the mono. Obviously I exclude separate Ha layer imaging in saying this.

Olly

[rfdesigner]

Star colour -- just guessing.

It might be down to the spectral response of the colours used for the bayer mask. With DSLRs there is strong overlap, presumably to try and match the human eye. see Spectral efficiency figure 8. However our astro RGB filters seem to have more abrupt cut off between colours.. so a body with essentially black body radiation but with a tinge more blue or red would possibly show up less with the DSLR than with abrupt RGB.

alternatively it could simply be that many DSLR images get clipped so stars turn white.. if people are experienced at astrophotography then they will try and avoid clipping, but they will probably also be using a dedicated CCD.

Olly: have you made any DSLR images... perhaps you could do one yourself and compare against one of your CCD images?

EDIT: looking further through the link.. it might have something to do with NIR response/lack of/NIR filter removal.

Derek

[PortableAstronomer]

Does anyone have any ideas how much this beast would cost?

Andor iKon-L 936 - 27.6 x 27.6 mm Active Image Area CCD Camera

I guess the line that says "contact us for a quote" means it's going to mean a 2nd mortgage..

[rfdesigner]

Does anyone have any ideas how much this beast would cost?

Andor iKon-L 936 - 27.6 x 27.6 mm Active Image Area CCD Camera

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expensive

I'd budget of 5 figures.

Of course you may be able to pick up a used one from a pro.. (I would be expecting them to be going EMCCD)

[George]

I've found this thread fascinating and informative as I've been dithering for a year or two about moving on to a CCD from a DSLR BUT I'm still undecided about which direction to take.

The obvious choice for my very LP sky's would be mono but I also live in one of the cloudier parts of the UK and messing about with filters, mosaic's and multiple nights on 1 image would put me off imaging for good.

That leaves OSC, again I wouldn't entertain mosaics for the above reasons so that leaves the APS size CCD's as the only runner for me. I tried cooling the 1000D last summer and had good results getting it down to -28C below ambient but I still have the condensation problem within the camera to crack. I'll have another go these coming short night months and If I don't succeed it's got to be the QHY8L I think, If I do succeed I'll spend the money on a MN190 which should pair well with the DSLR.

Keep this thread going its fascinating

[Zakalwe]

I've found this thread fascinating and informative as I've been dithering for a year or two about moving on to a CCD from a DSLR BUT I'm still undecided about which direction to take.

The obvious choice for my very LP sky's would be mono but I also live in one of the cloudier parts of the UK and messing about with filters, mosaic's and multiple nights on 1 image would put me off imaging for good.

That leaves OSC, again I wouldn't entertain mosaics for the above reasons so that leaves the APS size CCD's as the only runner for me. I tried cooling the 1000D last summer and had good results getting it down to -28C below ambient but I still have the condensation problem within the camera to crack. I'll have another go these coming short night months and If I don't succeed it's got to be the QHY8L I think, If I do succeed I'll spend the money on a MN190 which should pair well with the DSLR.

Keep this thread going its fascinating

Have a look at Mike's 2nd light post here

[ollypenrice]

Star colour -- just guessing.

Olly: have you made any DSLR images... perhaps you could do one yourself and compare against one of your CCD images?

Derek

Hi Derek, I haven't tried DSLR imaging myself and it really doesn't appeal to me. When I see people doing it it seems pretty confusing! Sometimes I look after the mount/guiding for guests using their own cameras and I don't know how they remember all the stuff that needs doing... Probably familiarity, in part.

George, you say,

The obvious choice for my very LP sky's would be mono but I also live in one of the cloudier parts of the UK and messing about with filters, mosaic's and multiple nights on 1 image would put me off imaging for good.

Let's think about this. The fastest cameras are mono CCDs. If you want a given image in the shortest time a mono CCD is the one. An hour of Luminance and 3x5 mins per colour in Bin 2 will not get you an APOD but it will beat anything else you can do in under two hours in any other camera. In second place an OSC CCD. In LP I'm told the mono advantage increases but I can't comment on that.

Also with a mono CCD you can do lovely narrowband work and do it also in the moonlight.

'Messing about with filters' means stopping the shoot, turning the wheel, changing the file name and restarting the shoot. I don't think that is much by way of messing about. If you are in a rush you don't even need to refocus if using, say, Baader filters.

Yes, the chip remains small but an Atik 314L is fast and quiet and the software is a peach so you are grabbing photons in a trice.

Olly

[cgarry]

Does each pixel on an OSC chip produce a pixel in the corresponding image or does it take 4 pixels to produce 1 colour pixel in the final image? Does a 3000 x 2000 QHY8 camera only produce a 1500 x 1000 pixel image?

Cheers,

Chris

[MikeWilson]

Does each pixel on an OSC chip produce a pixel in the corresponding image or does it take 4 pixels to produce 1 colour pixel in the final image? Does a 3000 x 2000 QHY8 camera only produce a 1500 x 1000 pixel image?

Cheers,

Chris

An OSC camera has a Bayer matrix covering the sensor. The colours are usually R, G, G, B.

Ha is Red. So you'd get only the red pixel getting signal as the green and blue pixels would filter the Ha out.

OIII is blue and green.

This is why mono is better than OSC for narrowband as all pixels are collecting data.

[cgarry]

An OSC camera has a Bayer matrix covering the sensor. The colours are usually R, G, G, B.

Ha is Red. So you'd get only the red pixel getting signal as the green and blue pixels would filter the Ha out.

OIII is blue and green.

This is why mono is better than OSC for narrowband as all pixels are collecting data.

Thanks, I understand that. I am not thinking about narrowband imaging though.

Is it the case that a QHY8L used to generate a single shot RGB image, would produce a 1500 x 1000 pixel image?

Chris

[MikeWilson]

Thanks, I understand that. I am not thinking about narrowband imaging though.

Is it the case that a QHY8L used to generate a single shot RGB image, would produce a 1500 x 1000 pixel image?

Chris

Hi Chris,

All OSC chips (that is to say sensors with a bayer matrix sat on them) produce full resolution images. During processing the bayer matrix is 'removed' from the .fits image and the remaining colours interpolated.

It's how all colour digital cameras work.

All the best,

Mike

[cgarry]

Thanks for that Mike, it all makes sense now.

Cheers,

Chris

[MikeWilson]

Thanks for that Mike, it all makes sense now.

Cheers,

Chris

It confused the heck out of me when I moved from DSLR to CCD. For the DSLR gives you a RAW file showing RGB values in each pixel to give a colour image. The .FITS files that come out of the CCD don't - it's quite literally a rawer raw. Deep Sky Stacker handles the interpolation to give the image at full resolution and it does a great job, imo

All the best,

Mike