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Can somebody please explain this to me?

Astrophotography Equipment
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#1 Stanford Cornelius

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Posted 26 September 2021 - 09:20 AM

I've recently been looking to buy a dedicated telescope camera. Through my search I've encountered this article; and I have tried to read it but I simply do not understand it. Could anyone explain this to in layman's terms, and maybe help recommend a camera for my telescope (Sky-Watcher 10" f/4.7 Traditional Dobsonian Telescope).

 

 

 

-Thanks



#2 kathyastro

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Posted 26 September 2021 - 10:11 AM

To be honest, I wouldn't worry about it.  It is way more technical than you need.

 

With a Dobsonian, I assume you will be taking planetary images.  A Dob mount is not suitable for taking images of deep sky objects.  There are lots of "planetary cameras" available.  That is what you should be looking for. 


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#3 RedLionNJ

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Posted 26 September 2021 - 10:38 AM

I've recently been looking to buy a dedicated telescope camera. Through my search I've encountered this article; and I have tried to read it but I simply do not understand it. Could anyone explain this to in layman's terms, and maybe help recommend a camera for my telescope (Sky-Watcher 10" f/4.7 Traditional Dobsonian Telescope).

 

 

 

-Thanks

Since this is in the planetary imaging forum, I would assume you want to do planetary imaging.  With a traditional (true) Dobsonian, this is going to be a little challenging, but having no personal experience, I'll leave this to others.

 

The primary, salient point from that article you linked is the advisement of somewhere between f/16 and f/22 for a camera with 3.76 micron pixels.  This is yet one more "explanation" of why the optimum f-ratio for hi-resolution imaging is considered to be between 5 & 7 times the size of the camera pixels.


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#4 drd715

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Posted 26 September 2021 - 10:39 AM

I think you are over thinking your camera parameters. Consider what is actually available to purchase in a camera for astrophotography use. Basically a dslr (un-modified, Ha modified, or factory made astronomy version), A cooled dedicated color camera or a cooled dedicated astronomy mono color camera (and several filters to create color images from the mono camera).

Cameras that pass the Ha band are desirable. Cooled cameras greatly lower electroic noise from the sensor and with a fixed sensor temperature you can use a pre-made darks library in processing, a real convenience. Mono versus One Shot Color is a whole other debate.

So what is on the market is what you get to chose from. Full Frame is great, but it is expensive especially in a dedicated cooled camera and it requires a larger "Flat " focus diameter created by the optics of your telescope. APS-C is a good place to be - it is good for wider framing compared to the smaller chip sensors. For specialty imaging such as planets a small imaging sensor size is good.

The newer imaging sensors refered to as "back illuminated " have much advantage in efficiency and don't have problematic noise such as "Amp Glow" (which calibrates out on sensors that do have it, but why bother if you don't have to). 16 bit vers 12/14 bits data has more dynamic range in your image. These mewer sensors have large well pixels (a plus to reduce saturation in stars. Keeps their color data better), better efficiency in collecting photons and low read noise without Amp Glow.

Arguments over pixel "pitch" and size in microns is somewhat mute as on the current era of sensors the spead in size of pixels available is quite limited. So you are probably going to end up with a pixel size of 3.75um - that's the main size available. Pixel size is related to the optics in your telescope and refers to how many pixels cover the maximum resolution of your optics (and resolution of your local seeing that night). You may see references to being "undersampled " or "oversampled" - follow up on that a bit, but don't get over concerned about it (at least don't think of it as a great problem). Undersampled you leave a small bit of potential resolution behind, oversupplied you don't gain more resolution in your image than the optics and seeing can provide - but for the range mix (at least on the average telescopes used by the amateur community) the current 3.75um pixels are fine.

I'm liking the Zwo Asi2600 pro cooled camera as a good performer at a resonable price. The asi533 is a good economy (relatively speaking) cooled camera with a bit smaller sensor in a sub 1K$ range. Mono is much more expensive especially considering the filters required may cost more than the camera - but there are those that can use the mono color sensors and filters to create the best images possible.

A DSLR can be a good economical place to start if you are imaging in relatively cool outdoor temperatures, but the advantages of a cooled camera in warm weather imaging are noticeable.

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#5 drd715

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Posted 26 September 2021 - 10:47 AM

For planetary imaging a simple non cooled camera works well, but a dslr with a shutter is not very good for high speed short exposure (video style) imaging.

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#6 Stanford Cornelius

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Posted 26 September 2021 - 10:54 AM

Thanks for the responses, everybody!




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