DSLR Vs CCD confusion

[TobyW]

Hi all,

Can someone give me some basic level advice?

I am looking at getting an evostar 80ed and I am confused at the DSLR Vs CCD camera route. I am looking at getting pictures of things like Nebulae etc but also like shooting the moon in high detail or grabing pics of Saturn. At the moment I have a 18Mp Canon DSLR and it shoots perfectly fine and yet I see a lot of people talking about and using CCD cameras and they are taking awesome shots with those. My question is this, why would you use a CCD that only has 2 - 8Mp over a DSLR that has a really high Mp (18 - 24) rating?

 

What am I missing here? Sorry if it sounds a bit basic but I wanted to get some input as to why you would use a CCD over a DSLR. 

 

Thanks

Toby

[Merlin66]

I use an ED80 with an ASI 1600MM CMOS camera, the cooled version is much superior to the colour DSLR.

I would recommend if you’re comfortable with the mono path.

 

[Skipper Billy]

In astroimaging Mp doesnt count for much.

The main advantage of a colour CCD over a DSLR is that they usually have cooling - the cooler the sensor the less noise in the images

The main advantage of a mono CCD over DSLR is the cooling again but with massively increased sensitivity and speed. But it comes at a price - you will also need a filter wheel and a set of filters and a PC to control everything.

I am over simplifying this but that's the bones of it. To start with your DSLR will serve you well and there are many great pictures taken with a DSLR. Personally I would jump straight from DSLR to Mono CCD/CMOS.

The requirements for imaging nebulae and plants are very different - nebulae can be pretty big whereas planets are tiny and require longer focal length and often video is sued to image planets followed by stacking the video frames whereas nebulae usually require lots of long exposures and a shorter focal length.

Hope that helps - shout out if you need help.

 

[CraigT82]

Hi Tony,

Im not really a DSO imager but I'll chip in some points to consider:

NEVER BUY A CAMERA BASED SOLELY ON HOW MANY MEGAPIXELS IT HAS!!!

1) DSLRs are designed for daytime photography, whereas astro CCDs/CMOS cameras are design for astro imaging. Use the right tool for the job. Not to say that you cant get good astro images from a DSLR. It's just not the optimum tool.

2) Astro cameras have cooling (mostly) to keep the noise low in long exposures. DSLRs dont usually have this. 

3) DSLRs have big sensors, if the image circle formed by your scope cant cover this big sensor then it's a waste of space, not to mention the severe vignetting you'd get.

Most astro imagers start off with a DSLR (as they already have one) then move over to mono CCD/CMOS cameras at some point. This forum is full of posts from people who wished they made that move earlier.

[TobyW]

16 minutes ago, CraigT82 said:

Hi Tony,

Im not really a DSO imager but I'll chip in some points to consider:

NEVER BUY A CAMERA BASED SOLELY ON HOW MANY MEGAPIXELS IT HAS!!!

1) DSLRs are designed for daytime photography, whereas astro CCDs/CMOS cameras are design for astro imaging. Use the right tool for the job. Not to say that you cant get good astro images from a DSLR. It's just not the optimum tool.

2) Astro cameras have cooling (mostly) to keep the noise low in long exposures. DSLRs dont usually have this. 

3) DSLRs have big sensors, if the image circle formed by your scope cant cover this big sensor then it's a waste of space, not to mention the severe vignetting you'd get.

Most astro imagers start off with a DSLR (as they already have one) then move over to mono CCD/CMOS cameras at some point. This forum is full of posts from people who wished they made that move earlier.

Thanks for the info. So am I right in thinking if I went for a mono CCD its only a B&W pic? Might sound daft / obvious but I am trying to grasps this CCD thang.

 

Cheers

Toby

[Knight of Clear Skies]

22 minutes ago, TobyW said:

Thanks for the info. So am I right in thinking if I went for a mono CCD its only a B&W pic? Might sound daft / obvious but I am trying to grasps this CCD thang.

A mono camera is typically used with filters in front of it to produce a colour image, the separate channels are combined in software. The explanation here may help.

[TobyW]

3 minutes ago, Knight of Clear Skies said:

A mono camera is typically used with filters in front of it to produce a colour image, the separate channels are combined in software. The explanation here may help.

Ahh ok, I understand. Thats a great explanation. Thanks for the info.

[Cornelius Varley]

17 minutes ago, TobyW said:

Thanks for the info. So am I right in thinking if I went for a mono CCD its only a B&W pic? Might sound daft / obvious but I am trying to grasps this CCD thang.

 

Cheers

Toby

To create a colour image using a mono camera you take three sets of images, one set through a red filter, one through a green filter and one through a blue filter. Another set of images are also taken through a luminance filter. After individually stacking the R,G,B and L sets the images can then be combined to create a colour image. The camera can only record in mono so the filters are used to record the levels of red, green and blue as values of grey which then produce a full colour image when the different values are combined together. One shot colour cameras (OSC) use a matrix filter above the sensor, known as a Bayer matrix, to create the colour image. OSC cameras have a disadvantage of mono camera in that the values of RGB over the bayer matrix whereas a mono camera uses the full sensor each time to record the RGB levels.

[TobyW]

10 minutes ago, Cornelius Varley said:

To create a colour image using a mono camera you take three sets of images, one set through a red filter, one through a green filter and one through a blue filter. Another set of images are also taken through a luminance filter. After individually stacking the R,G,B and L sets the images can then be combined to create a colour image. The camera can only record in mono so the filters are used to record the levels of red, green and blue as values of grey which then produce a full colour image when the different values are combined together. One shot colour cameras (OSC) use a matrix filter above the sensor, known as a Bayer matrix, to create the colour image. OSC cameras have a disadvantage of mono camera in that the values of RGB over the bayer matrix whereas a mono camera uses the full sensor each time to record the RGB levels.

OK, that makes sense. Thanks for the input. I am guessing to go down the route of mono CCD and all the filters (x4) required isnt going to be a cheap solution to get into?

 

Thanks

[alacant]

10 minutes ago, TobyW said:

a cheap solution to get into?

Hi

If you have a permanent setup in an observatory, time to do the processing and sufficient clear nights to justify the expense, then do it.

Otherwise, use your -very capable- canon. If you decide you like it, then perhaps would be a better time to make a decision.

Cheers.

[TobyW]

Just now, alacant said:

Hi

If you have a permanent setup in an observatory, time to do the processing and sufficient clear nights to justify the expense, then do it.

Otherwise, use your -very capable- canon. If you decide you like it, then perhaps would be a better time to make a decision.

Cheers.

Always good to some sound advice. Thank you.

 

Toby

[ollypenrice]

Just be aware that LRGB with a mono camera is faster than OSC. The LRGB system was invented to save time. (A colour filter over each pixel means that the two other colours are blocked so the total light per pixel is reduced. During the luminance phase of the capture all the colours are reaching the mono camera's chip, so saving time.) Shooting through 4 filters is not 4x slower than shooting through the three fixed filters of an OSC. It's generally considered to be about 20% faster.

Olly