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Planetary camera to start.


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I would like to start with the photography of the Moon, Sun and planets and I have seen these planetary cameras from Svbony, the SV 105, the SV 89 and the SV 305, what do you think? Has anyone tried them?

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Not sure what the SV89 is - I'm assuming you mean the 205?

Like @AstroMuni said, it depends on what kind of telescope you plan on pairing with the camera. When it comes to planetary, it all starts with the aperture of your telescope (focal length actually doesn't really matter as much as one would think). Once you know the aperture of your telescope, then you can look at what kind of pixel size your camera of choice should have. The equation does change if you plan on using a Barlow, though.

But, of course, you can calculate it the other way around, starting with the cameras. This should be a useful exercise if you're planning a rig from the ground up and don't even have a telescope yet. I've put together a quick table outlining the differences between Svbony's planetary camera offerings (or what little info I could find) and some examples of telescopes that match. This is all assuming no intention of using a Barlow, by the way.

  SV105 SV205 SV305
Resolution 1920x1080 2592x1944 1920x1080
ADC 10bit 10bit 12bit
FPS 30 15 20
Pixel Size 3 1.4 2.9
Price $50 $90 $142
Rec. Aperture 7" 6" 7"
Ex. Scope Skymax 180 Explorer 150PL Skymax 180

If I were you, I'd go for the 305, based on the ADC alone (12bit is 64 times more colour gradations than 10bit).

The 205 may seem appealing because it's got more pixels, but those 1.4μm pixels are tiny and the 15fps much too slow for lucky imaging.

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7 minutes ago, raadoo said:

If I were you, I'd go for the 305, based on the ADC alone (12bit is 64 times more colour gradations than 10bit).

The 205 may seem appealing because it's got more pixels, but those 1.4μm pixels are tiny and the 15fps much too slow for lucky imaging.

Bit depth is rather inconsequential for planetary imaging as most imaging happens at 8bits anyway, and you'll be hard pressed to get saturation at planetary speeds with 10bit if you decide to go with higher bit depth.

As far as pixel size is concerned, here is F/ratio - pixel size relationship for critical sampling case:

F_ratio = pixel_size * 2 / wavelength

where pixel size and wavelength are in same units (meters, millimeters, nanometers - choice is yours).

Take wavelength to be either exact wavelength - like 656nm for Ha solar or if using Ha filter for lunar for example, or ~500-520nm in general case - for full spectrum / color imaging.

From above equation, we have following F-ratios for given pixel sizes:

3µm gives F/11.5

1.4µm gives F/5.4

2.9µm gives F/11.1

15 minutes ago, raadoo said:

(12bit is 64 times more colour gradations than 10bit).

Two additional bits give only x4 more levels (2^2 = 4).

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30 minutes ago, vlaiv said:

Bit depth is rather inconsequential for planetary imaging as most imaging happens at 8bits anyway, and you'll be hard pressed to get saturation at planetary speeds with 10bit if you decide to go with higher bit depth.

As far as pixel size is concerned, here is F/ratio - pixel size relationship for critical sampling case:

F_ratio = pixel_size * 2 / wavelength

where pixel size and wavelength are in same units (meters, millimeters, nanometers - choice is yours).

Take wavelength to be either exact wavelength - like 656nm for Ha solar or if using Ha filter for lunar for example, or ~500-520nm in general case - for full spectrum / color imaging.

From above equation, we have following F-ratios for given pixel sizes:

3µm gives F/11.5

1.4µm gives F/5.4

2.9µm gives F/11.1

Two additional bits give only x4 more levels (2^2 = 4).

I may be mistaken but it seems that all three cameras above are colour; so you’re right that it’s 4 times more gradations … per channel. 4*4*4 = 64.

Bit depth is probably not that important for planetary but for lunar I would always go for the most bits I can get. If nothing else, it gives one some added flexibility in post before things start to visibly posterize.

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2 minutes ago, raadoo said:

Bit depth is probably not that important for planetary but for lunar I would always go for the most bits I can get. If nothing else, it gives one some added flexibility in post before things start to visibly posterize.

Again - not important really.

Each time you stack two subs - no matter how many bits subs themselves have - you get x2 more bit depth in the data. Stacking couple of hundred subs which we often do in planetary (say 5% of 20000 subs will be 400 subs stacked) will increase bit depth by say 8ish bits (log base two number of subs stacked).

Even if you have 10bit or 12bit depth, what sort of gain will you be using? High gain to reduce read noise?

If you use very high gain and you have 12bit depth - you'll effectively record less than say 8bit "resolution" in reality.

Here are graphs for say ASI224:

image.png.25af156dc551cbe5d8860b52374df5a9.png

Most people will use gain of say 350 to reduce read noise to max. At that gain setting e/ADU will be around 0.125 e/ADU (for gain of 318 and less for gain of 350).

That is x8 or "three bits" multiplier. Say you capture some number that needs 12bits to record - like 3000ADU - in reality number of electrons that you recorded (and remember you can't record fraction of electron really - anything that is "fraction" is just noise as there is always integer number of electrons) 3000ADU * 0.125e/ADU = 375e - which is really 9bit number (12-3)

11 minutes ago, raadoo said:

so you’re right that it’s 4 times more gradations … per channel. 4*4*4 = 64.

There is no "per channel" in capture time - each pixel records single color.

Full three channel color information is restored after debayering. Regular debayering is just "making things up" really (interpolation) so for planetary it is better to do bayer drizzle approach (which again keeps original resolution from pixel size unlike interpolation that looses resolution) which restores color from stacking (and stacking increases bit depth).

In any case - bit depth of camera is not something that will lead to posterization if everything is done properly.

Using higher bit depth has some benefits in some special cases, but for planetary, for most part it is not necessary. 8bit capture is enough.

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8 hours ago, AstroMuni said:

Con quale telescopio pensi di usarli?

I bought a used Nexstar 8 SE with which I would like to do more serious things than the contemplative observations of the Moon & planets I have done so far.

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15 hours ago, Gonariu said:

I bought a used Nexstar 8 SE with which I would like to do more serious things than the contemplative observations of the Moon & planets I have done so far.

I would have gone for the SV305 as it allows longer exposure times and uses a better sensor. Personally I use the ASI224mc which @vlaiv has already mentioned above

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If considering the Svbony 305 be aware there are different versions. The SV305 PRO is USB3 and the standard SV305 is USB 2.

The ZWO cameras are the safer bet though as there will be no problems with software or drivers etc.

Edited by johninderby
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Posted (edited)

I thank everyone for the valuable advice; so far I have been a (almost) pure visualist, but for some time I have realized that to make contemplative observations of the Moon (I observe and search on a lunar map what I see at the telescope) the old Konus 60/700 achromatic refractor, bought in 1983 when I was a boy, was more than enough; a better telescope used only in this way is wasted. I think (and hope) that I will not have software problems as last year I got a second laptop, in fact the first one could fail and I would have had problems with distance learning (I'm a math and physics teacher).

Edited by Gonariu
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I used to have the sv105 for planetary and lunar and couldn't get on with the camera one bit and thought it was pretty rubbish Used it in my 150p and Skymax 127. Then I bought a zwo asi120mc-s though more expensive, it just works simple easy to use no issues whatsoever. I use this as my guidescope camera now. I agree with others and definitely go zwo cameras. 

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