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This is a Celestron CPC 800 XLT telescope. It doesn't seem to have charge-coupled device (CCD) attached. Can a CCD be attached separately to this 8" Schmidt-Cassegrain telescope even if it didn't come along with the package?

For astro-phtography how cheaper and cost-effective would a DSLR camera be than CCD? I think it is better to suit yourself with a CCD than a DSLR camera for quality photography.

Do excuse this novice who is here to learn.

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You will typically find that CCD cameras are sold separately to the telescopes. That way the telescope can be used visually or for astrophotography, by either fitting an eyepiece, or a camera. Most telescopes do ship with eyepieces, as they are much less expensive than a CCD and it is sort of expected, but most observers will typically replace this eyepiece with a better one anyway, so to all intents and purposes, when you buy a telescope you are just buying the Optical Tube Assembly and maybe a mount, and you add to that all the accessories you need to accomplish your objectives. Different CCDs will be used for different purposes, for instance planetary observations or deep space objects.

That telescope has a fork mount. Note that this constrains how much equipment you can put on the end of the telescope without getting in the way of the mount. It also is an Alt-Az mount, which means it is not polar aligned; stars will rotate in the field of view, requiring a field de-rotator in addition to a CCD.

It looks like a nice enough scope for visual observations, but if you are interested in astrophotography, you might want to hold off for a bit, maybe get a scope for visual use first, and maybe make use of well-set-up robotic astrographs that you can hire over the internet, like slooh.com and itelescope.net - get some experience using premium gear that you don't have to worry about setting up or maintaining, and while you do that, work out what gear you will be happy about getting for yourself. The fact you are asking this question about CCDs suggests you aren't yet ready to spend money on astrophotography gear...

Getting set up well for visual stuff can set you back hundreds... Getting set up for astrophotography can set you back many thousands, so you want to be well equipped to make good purchasing decisions. And you can rent a lot of time on some pretty good telescopes for that same $...

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  • $\begingroup$ it's already bought. but haven't got hold oof it yet.will do in a few weeks. so i was curious if a ccd can be attached.and as u pointed out abt astro-photography, we might just need a high quality camera like SLR, ryt? is there anything else? i shud probably edit the question as per ur answer ;) $\endgroup$ – MycrofD Jul 2 '14 at 8:56
  • $\begingroup$ You'll enjoy using it for visual observations I am sure. A CCD can be attached. It'd fit in place of the eyepiece. If you have a DSLR then give it a go (you'll need an adaptor); if you don't, then don't buy one for astrophotography. For the same money you could get a CCD that will be better for your purposes. But I'd hold off on any camera purchase for a bit yet. Learn a bit more first. $\endgroup$ – Jeremy Jul 2 '14 at 11:33
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Cameras are sold separately.

Fork mounted SCTs like the CPC run in alt-az mode (up/down left/right movements). Although the controlling software can track objects fine for visual use, because neither axis points at the celestial pole, tracking alt-az mounts suffer from an effect called field rotation.

Think of watching a point on the rim of a wheel as it rotates - you can track the point, but the direction to the centre of the wheel changes as it rotates. in images, that means that the field of view appears to gradually rotate around the object you're tracking, which causes trailing that increases as you move away from the object. This limits your maximum exposure time before the traiing becomes noticeable. Exactly how long varies with your latitude and where in the sky you're pointing, but around 30 seconds or so is a rough ballpark figure.

For longer exposures, you either need a field derotator (Meade used to do one, but as far as I know Celestron never have), or (more commonly) an equatorial mount. With one axis pointed at the celestial pole, tracking an object doesn't cause field rotation from the point of view of an attached camera - for the wheel example, think of a camera attached to an extension of the axle - now, the camera rotates with the wheel, so from the camera's point of view the wheel stays in the same relative position - so no trailing. This means that exposures are now only limited by tracking accuracy (and how long it takes for light pollution to saturate the image).

With a fork mounted SCT, the usual way to achieve this is something called an equatorial wedge. This bolts between the fork mount and the tripod, tilting it so that the the azimuth axis points at the celestial pole, and making the mount work as an equatorial mount.

DSLR cameras have the advantage of being relatively cheap (especially secondhand), and can be modified to be more sensitive to h-alpha light (the standard infrared cut filter in front of the sensor also blocks most h-alpha light - replacing this with something that passes h-alpha makes a big difference for images of many emission nebulae that have h-alpha. The other advantage of DSLRs is that the sensors are big. Downside is that they're not cooled cameras, which makes the images more noisy - especially in warmer weather.

Astronomical cameras (CCD or CMOS) for long exposure imaging usually include peltier effect coolers - this reduces the sensor temperature by a lot - often tens of degrees, to below freezing point in some cases. Dropping the temperature significantly reduces thermal noise, giving you less noisy images. You can also get monochrome cameras, which make working with narrowband filters easier. Downside is that cooled CCD/CMOS cameras can be very expensive, especially at sensor sizes comparable to DSLRs. Many of the more affordable ones have sensors significantly smaller, and with fewer pixels than DSLRs.

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