Astro-camera Quandry

[wimvb]

3 hours ago, Jp114 said:

I recently tried using a Canon 70-200 f/4 at 200mm, with and Atik 314L+ (6.4 micron pixels), so I was severely over sampling. 

Your sample rate was about 6.5"/pixel, which is undersampled. You can also tell by the star shapes in your image. All but the blown out stars look square, which is a sign of undersampling. Still, a very nice picture.

[vlaiv]

5 minutes ago, wimvb said:

Your sample rate was about 6.5"/pixel, which is undersampled. You can also tell by the star shapes in your image. All but the blown out stars look square, which is a sign of undersampling. Still, a very nice picture.

It's probably me, but I don't see any square looking stars?

Here - this is 400% zoom:

Does any of these stars look square to you?

Also, I'm really not sure that 6.5"/px is "seriously oversampling", especially with camera lens. F/4 lens with 200mm focal length has 50mm of aperture. Size of airy disk of perfect 50mm aperture is 5.13" alone.

Next - this is lens - here look at this:

6.4µm pixel size is equivalent of 1000/6.4 = ~156 LPMM. This lens has MTF below 80% even on axis for 30+ LPMM

[Jp114]

35 minutes ago, vlaiv said:

Does any of these stars look square to you?

I can see the results of my guiding issues, hopefully now resolved... 

My sampling status is based on CCD Tools calculator.

Apart from the guiding, the stars looked ok to me. 

[vlaiv]

21 minutes ago, Jp114 said:

Apart from the guiding, the stars looked ok to me. 

Indeed.

That calculator is not very good in results it gives, so don't rely on it. For example - 0.7"/px is going to be oversampling for 99.99% people in amateur community (and by factor of x2 for 90% of people) - yet it will say it is "OK".

[rnobleeddy]

 

On 17/09/2021 at 09:48, wimvb said:

I think that it very much depends on what you wish to achieve. With the European weather being the way it is, you really have to plan photo sessions. That extra night where you had thought to also collect Oiii for an object, may never materialise during one season. Osc with dual band may just be simpler than mono and a filter wheel. Only you can make that decision. I find that the development we have seen in astro cameras forces us to reevaluate old truths. What was an obvious choice yesteryear is no longer so.

just a few years ago, coming from dslr, a mono camera seemed the obvious way to go for me. But my next camera will be an osc.

I've been there, and have a folder with a number of targets that are half finished. However....

With LRGB data I can buy the OSC over mono debate, because it's easy to not complete an LRGB image, there are lots of choices (how much L vs RGB) and there's a certain simplicity to processing the OSC data. 

However, for narrowband with only H/O, it's not that cumbersome to ensure that you capture both with mono. And mono cameras are almost always more efficient, so the maths is clearly in favor of the mono camera. And mono allows you to add an S filter too, which is very inefficient to do with OSC.