A question about oversampling with the Quark

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HAL
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A question about oversampling with the Quark

Post by HAL »

Sorry for my millions of newbie Quark user questions. I plan to take it out for first light tomorrow weather permitting.

I am using it with a Skywatcher 80ED (focal length = 800 mm) and a ZWO ASI174MM (pixel size = 5.86 µm). I know that the Quark has an internal 4.2x Barlow which seems very big to me. Crunching the numbers tells me that I will be oversampling by quite a lot. The ideal focal length for this camera/aperture/wavelength comes out as 1429 mm and the focal length of the system with the integrated Barlow will be 3360mm.

Any thoughts? I feel like a lot of people's set-ups are going to end up oversampling? Does it really matter? Is everyone using a focal reducer?

Thank you to anyone who can help with my confusion!


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Re: A question about oversampling with the Quark

Post by Alto »

Watching with interest. :geek:

I'm torn between an f11 or an f5.6 as the 'scope. I see the Quark leaflet gives a 'scope range of f4 to f9. I'm not necessarily interested in FDs but I'm sure I've seen longer scopes used than f9....?

I guess if I use the f11 it's possible with a ZWO 174, perhaps binned 2*2.
But nothing's perfect, just the best one can do!?

Seeing rules, though!


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Re: A question about oversampling with the Quark

Post by Alto »

Meanwhile Cloud rules!


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Re: A question about oversampling with the Quark

Post by marktownley »

There is a little oversampling with this system, but if the seeing is supporting the 80mm aperture you should be fine, 80mm in Ha you should be fine with seeing most of the time.

If the seeing does not support the aperture try a 0.5x reducer on the nose of the camera.

I wouldn't recommend the 2x binning with the 174 chipped camera.


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Re: A question about oversampling with the Quark

Post by HAL »

Thanks both. I'll see how I get on today.


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Re: A question about oversampling with the Quark

Post by Alto »

HAL wrote: Sat Aug 06, 2022 10:34 am Thanks both. I'll see how I get on today.
You have Sun!? :o


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Re: A question about oversampling with the Quark

Post by HAL »

Alto wrote: Sat Aug 06, 2022 11:21 am
HAL wrote: Sat Aug 06, 2022 10:34 am Thanks both. I'll see how I get on today.
You have Sun!? :o
Yes!!! First light achieved. I'm very happy with the view for a first go but suffered terrible Newton rings. I think there's an adaptor I can get?


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Re: A question about oversampling with the Quark

Post by Radon86 »

HAL wrote: Fri Aug 05, 2022 7:40 pm Sorry for my millions of newbie Quark user questions. I plan to take it out for first light tomorrow weather permitting.

I am using it with a Skywatcher 80ED (focal length = 800 mm) and a ZWO ASI174MM (pixel size = 5.86 µm). I know that the Quark has an internal 4.2x Barlow which seems very big to me. Crunching the numbers tells me that I will be oversampling by quite a lot. The ideal focal length for this camera/aperture/wavelength comes out as 1429 mm and the focal length of the system with the integrated Barlow will be 3360mm.

Any thoughts? I feel like a lot of people's set-ups are going to end up oversampling? Does it really matter? Is everyone using a focal reducer?

Thank you to anyone who can help with my confusion!
Hello Hal,
Can you check your focal length as I thought the Skywatcher 80ED had a focal length of 600mm (as 800mm makes it a very long scope F10, which is unusual for a ED refractor).
If that is the case, your telescope is F(600/80)=F7.5. After the Quark, you will get an approx FR=7.5x4.2=31.5, so you will be oversampling I think slightly with your ASI 174mm with its 5.76um sized pixels.

I think if you have Newton rings, you can try the basic ZWO T2 tilter or the new one. I found a 2mm tilt was enough, maybe you can get away with anywhere between 1-2mm tilt on the Tilter.

Enjoy the imaging!

Magnus


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Re: A question about oversampling with the Quark

Post by HAL »

Radon86 wrote: Sat Aug 06, 2022 5:27 pm
HAL wrote: Fri Aug 05, 2022 7:40 pm Sorry for my millions of newbie Quark user questions. I plan to take it out for first light tomorrow weather permitting.

I am using it with a Skywatcher 80ED (focal length = 800 mm) and a ZWO ASI174MM (pixel size = 5.86 µm). I know that the Quark has an internal 4.2x Barlow which seems very big to me. Crunching the numbers tells me that I will be oversampling by quite a lot. The ideal focal length for this camera/aperture/wavelength comes out as 1429 mm and the focal length of the system with the integrated Barlow will be 3360mm.

Any thoughts? I feel like a lot of people's set-ups are going to end up oversampling? Does it really matter? Is everyone using a focal reducer?

Thank you to anyone who can help with my confusion!
Hello Hal,
Can you check your focal length as I thought the Skywatcher 80ED had a focal length of 600mm (as 800mm makes it a very long scope F10, which is unusual for a ED refractor).
If that is the case, your telescope is F(600/80)=F7.5. After the Quark, you will get an approx FR=7.5x4.2=31.5, so you will be oversampling I think slightly with your ASI 174mm with its 5.76um sized pixels.

I think if you have Newton rings, you can try the basic ZWO T2 tilter or the new one. I found a 2mm tilt was enough, maybe you can get away with anywhere between 1-2mm tilt on the Tilter.

Enjoy the imaging!

Magnus
Magnus you are correct! I wrote down 600 mm and then randomly changed it to 800 mm when I was calculating. This brings down the amount of oversampling significantly. Thanks for pointing out my error.


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Re: A question about oversampling with the Quark

Post by Alto »

HAL wrote: Sat Aug 06, 2022 5:19 pm
Alto wrote: Sat Aug 06, 2022 11:21 am
HAL wrote: Sat Aug 06, 2022 10:34 am Thanks both. I'll see how I get on today.
You have Sun!? :o
Yes!!! First light achieved. I'm very happy with the view for a first go but suffered terrible Newton rings. I think there's an adaptor I can get?
Great news. Meanwhile the cloud continues to dominate over me! Not too bad in a way, it's taken me a while to source a 2inch UV/IR filter and hopefully it'll arrive this coming week.

Adapter, yes - tilt adjuster.


Call me Geoff.

I do what I do because I want to, and because I can....

Doesn't mean I know what I'm doing, though!
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