Dedicated "planetary" camera vs general purpose astro camera

Yes, yes you can. Smaller pixels are an advantage too; they should give you finer detail. Mostly the advantage for planetary camera is they are cheaper and simpler; smaller resolution, no cooling. But if you already have a camera that matches those specs, just use that instead.

You should probably also not use the reducer when doing planetary video. Well, depending on whether you'd want the moons in a capture of Jupiter :-)

+1

Smaller pixels are better for lunar/planetary work. I just picked up a qhy5111715C and it has a pixel size of just 1.49 microns. This means that on my 8" SCT I won't need a Barlow to get the correct oversampling. I'm chuffed with the idea of eliminating that element from the imaging train.

Rick Veregin:
You also want to have an f-ratio of 5 to 7x your pixel scale. So with 2.4 micron pixels you want to be at f12 to f17, I would suggest a 1.5X barlow as a good point, the higher the f-ratio the dimmer the image, a 2X barlow would be too much. At 3.87 micron pixels you need something like a 2 to 2.5x barlow to get to the same point. Either is fine in this regard, either way you get a similar signal to each pixel.

I'm not well versed in planetary imaging, but shouldn't focal lenght be the focus here and not the f-ratio? Or are you giving f number that correspond to the OP telescope?

Frame rate matters little if the seeing isn't good and if it is really good then it matters little (let's say above 30 fps). Bit depth isn't that important, if at all.

TiffsAndAstro:
I recently got a C6, attached my 533 to it with a Barlow barely screwed on nose piece.

With a tight ROI on Jupiter it kicks out 160fps.

As a noob, My images rubbish images are limited by my ability to focus (or not) and my astro surface processing skils

Give it a try and see. You can always upgrade to a smaller pixel camera later.

Not a bad image at all! Lots of color in the bands. You should check out Wavesharp2 for sharpening, it's the successor to the widely known Registax which is no longer available or supported. There are some great tutorials on Youtube.

I'm still not following you.

5 to 7 times the pixel sizes for your focal ratio will put you way past the Dawes/Rayleigh limit of you telescope.
I agree that focal length (and sensor size) is important since it determines your FOV, but I still don't see how, assuming ~3.75micron pixels, a 160mm f/22.5 would be adequate while a 600mm F/6 wouldn't be.
They both have a focal length of 3600mm giving  0.21arcsec per pixels.
The Rayleigh limit for the 600mm would be ~0.23arcsec
For the 160mm it would be ~0.86arcsec

Like I said, I'm still a newbie so I may be getting stuck up on something unimportant, but focusing on f-ratio instead of f-length seems wrong

Médéric Hébert:
I'm still not following you.

5 to 7 times the pixel sizes for your focal ratio will put you way past the Dawes/Rayleigh limit of you telescope.
I agree that focal length (and sensor size) is important since it determines your FOV, but I still don't see how, assuming ~3.75micron pixels, a 160mm f/22.5 would be adequate while a 600mm F/6 wouldn't be.
They both have a focal length of 3600mm giving  0.21arcsec per pixels.
The Rayleigh limit for the 600mm would be ~0.23arcsec
For the 160mm it would be ~0.86arcsec

Like I said, I'm still a newbie so I may be getting stuck up on something unimportant, but focusing on f-ratio instead of f-length seems wrong

I am correcting some of my comments, I'm sorry if some of them may have led you astray.

I think I can show you how this arises and how it works, by showing the math.

A star is spread into the Point Spread Function, PSF, by diffraction through the aperture. In terms of sampling theory from Nyquist-Shannon, for image the FWHM is the best metric to use with the width of the PSF.  Another metric often used is the diameter to the 1st minimum, or one could even include the other minima in the spot size, these can make the spot size much bigger.

If you look at the angular Airy Disk, the angle theta(@FWHM) = 1.03 lambda/D, lambda is the wavelength, say 0.55 microns, and D is the aperture. So the angular size of the PSF depends on aperture. Note one must be careful in using this equation, as all the units have to rationalized, so there is a constant term not shown that depends on what units you want your angle to be in.

Now, what is the resultant spot size on the camera sensor? Well the angle theta is small, so theta = sin(theta)=x/F, where x is our spot diameter on the sensor, and F is the focal length. We now can write: 
Theta=x/F = 1.03 lamda/D  or spot FWHM  x = 1.03 lambda * F/D or x = 1.03 lambda * FR. Now we have no angles here, so if lambda is 0.55 microns, the x is in microns and the focal ratio is unitless.

Spot FWHM = x = 1.03*0.55*FR= 0.5565 * FR. AT f22 we get 12.5 micron for the FWHM of the spot size. Sampling theory says we need at least 2 to 3 X pixels within the FWHM, so 12.5 micron spot size here would be good with 4 um pixels. Note the full spot size especially if we include some extra minima is larger. Still, the FWHM is appropriate for sampling. 

The conclusion is the spot size on the sensor depends only on the F/D ratio and the wavelength. The spot size is the same no matter what the aperture is at a given FR.

Now Rayleigh resolution is the difference in angle between two equal intensity stars each with overlapping PSF, at that point the two FWHM are nearly touching, while at the Dawes resolution the FWHM essentially are touching. This is the slippery slope because it is very easy to fall into the trap (as I did) that the PSF spot size in the sensor is so large that you cannot reach the resolution of your setup. The resolution is determined by two overlapping PSF, and not directly just taking the width of the PSF. 

A very good reference for the Rayleigh and Dawes resolution and telescope resolution compared to the FWHM of the Airy disk is: Telescope resolution That reference has some very nice clear figures as well to show the PSF.

Again, hope this helps, and sorry for any confusion I may have caused.
Rick

Fabian Butkovich:
@Rick Veregin Thank you so much for the plentiful detailed advice!

I hadn't thougt about taking Jupiters rotation into account, for my most recent capture:


Jupiter February 28th 2025

I captured 10k frames @ 28fps as shown in the Touptek camera specs above, this would equate to 10k/28 = 357 / 60 ~ 6min of video, which is above the rotation threshold as you suggest. I will keep that in mind during my next acquisition. 

I have considered trying with a 2X Celestron Omni Barlow I have in my kit, however this would make collimation and focusing even more tricker. It's worth a shot.

A great start, Fabian, looks good! Glad if I could help.
Rick

TiffsAndAstro:

Fabian Butkovich:
Wavesharp2

i will have a look at it ty. i think my biggest issue right now is know if the video im taking is even in focus

If you don't have a bahtinov mask yet, that's a good investment and they're cheap.

wow, ty for this. that final result is amazing. to be fair, my stacked unprocessed image doesn't look a million miles away from yours. but my final result does  

i've been trying upping gamma and using focus helper in fire capture which might help a bit.

would i recognise good seeing if i saw it?

TiffsAndAstro:
wow, ty for this. that final result is amazing. to be fair, my stacked unprocessed image doesn't look a million miles away from yours. but my final result does  

i've been trying upping gamma and using focus helper in fire capture which might help a bit.

would i recognise good seeing if i saw it?

Yes upping gamma helps. Also for focussing you could change color balance to look at only the red channel, that one is less affected by seeing, or only the green channel, that is the strongest signal--in either case this reduces color blur due to atmospheric distortion, unless the planet is very high in the sky.  One just needs to remember to switch settings back before your acquisition though. And make sure you fix color alignment in Autostakkert in your processing, it works great.

I think one could use a Bhatinov mask, but it is a pain. You need to slew to a bright star, do the focus, then slew back. And if your camera has a small FOV this can be challenging. And if you need to adjust focus again if you are doing mutliple videos it is a pain. Personally I do my alignment, then use the mask on a star, then go to the planet and use that as a base for focus.

The mask also helps with umderstanding the seeing, the better the seeing the sharper the diffraction spikes and the more stable the spikes. In poor seeing the spikes will be moving around a lot, hard to tell when you are properly centred with the spikes, and the spikes also go thin, then fat in random fashion, or just look really fat. Once on the planet if seeing is good you will see some details, that should go in and out of focus when you tweak your focusser, just go back and forth so any detail seems clearest. If you can't see much detail and it almost doesn't seem to matter with small tweaks in focus, so you can't tell if you are focussed, seeing is poor.
Rick

….oh, and don't forget to use a UV/IR cut filter if you are shooting OSC!