buying advice for first planetary camera for C8 - Forums

Topic starter

Sep 27, 2020

Hi All,

I was recommended to buy the ASI178MC to use with my C8 based on fact that it had the highest resolution (6.4MB) when compared to ASI224MC (1.2) and ASI462MC (2.1).
However, using astronomy.tools/calculators/field_of_view/ it seems like the smaller sensors will "zoom" in more on planets than the ASI178MC sensor will when using my C8.
But the ASI178MC may allow me to get my feet wet capturing some DSO's with my reducer.
Any advice? Can I crop in with my ASI178MC when capturing the image or afterward? Or can I use a 5x barlow? Or does it make more sense to get the ASI462MC instead?
Thanks in advance,
Dave

Engaging

andrea tasselli

Frequent contributor

Sep 27, 2020

Hi,

I'd recommend the ASI224MC over the others. It's more sensitive and, coupled with a 2x Barlow, you'd get the sweet spot for planetary resolution at no expense to the signal to noise ratio. In fact I'm going to buy the same camera for fast rotators such as Jupiter. Plus, faster download times.

Cheers

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Michael von Berner-Purgstall

Sep 28, 2020

Hi Dave!
Clear advice - get the QHY462c.
It has more "reach", is almost as fast, 135 vs 150fps, but the younger generation sensor and you get for just a few bucks more two filters, the uv/ir cut filter and the IR filter.

Michael von Berner-Purgstall

Sep 28, 2020 · Edited: Sep 28, 2020

Michael S.:
Hi Dave!Clear advice - get the QHY462c.
It has more "reach", is almost as fast, 135 vs 150fps, but the younger generation sensor and you get for just a few bucks more two filters, the uv/ir cut filter and the IR filter.

Ups, the 178mc just has 30/
60fps...

Werner Stumpferl

Sep 28, 2020

Hi Dave,
don't compare Megapixels when you make planetary imaging. More then one megapixel is not necessary. What you need is a good framerate and less read noise to improve gain.
I have made good experiences with the ASI385MC. With a pixelsize of 3.75um the 385MC has 2.5 times the size of a 462MC-pixel. So also 2.5 times more light in same time. You can play with framerate and/or gain much better then with the 462.
An advantage of the 462 is that the picture is more cropped with same focal length but if you play with Barlows you can compensate this.
Also I think that a 5x Barlow with your f/10 is too much. Better you try a 2x or 2.5x Barlow.
You see … in astronomy you don't get easy answers.

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Michael von Berner-Purgstall

Sep 28, 2020

Werner Stumpferl:
With a pixelsize of 3.75um the 385MC has 2.5 times the size of a 462MC-pixel.

??? PLZ explain your math. How is 3.75 2.5 times the size of 2.9 microns the QHY462c does have?
Have you ever used the QHY462c?
I have, as well as 290mc,174 and still own the 178. For planetary (!) not one of those comes close. Solar and lunar imaging is an other topic.

Werner Stumpferl

Sep 28, 2020

You are right, I have calculated with 2.4um not with 2.9. So factor is 1.7
3.75*3.75 = 14 um2
2.9*2.9 = 8.4um2
So area is 1.7 times higher.

And no, I haven't the 462 but I have the 183MC and the 385MC and the 385MC makes very good pictures and I can play a little more with gain and exposure and framerate as with the 183MC (2.4um Pixels).

davenyc

Topic starter

Sep 28, 2020 · Edited: Sep 28, 2020

Thanks for the input. It certainly seems like there are no easy answers

I coincidentally discovered the QHY462c last night. Others apparently have already discovered it because it is sold out everywhere

I wanted to get a camera in time for the Mars opposition. Is the ASI462 recommended as well?

Michael: I'm new at this so can you tell me how do the filters that come with the QHY462c affect the image it produces?

To muddy the waters a little more, how does full well figure into the analysis? 224=19K vs 462=12K

Also do QHY cameras play nice with ASIAIR PRO?

Thanks much!

Werner Stumpferl

Sep 28, 2020

Anywhere in the web I have found a calculation of how much photons hit a defined area per second. With the short exposure times by planetary images, full well capacity has not really an effect for you. Full well has more effects with DSO and bright stars and dark nebulas with long term exposures.

Michael von Berner-Purgstall

Sep 28, 2020 · Edited: Sep 28, 2020

Michael: I'm new at this so can you tell me how do the filters that come with the QHY462c affect the image it produces?

Hi Dave!
UV/Ir block filter on during recording in visible light for Mars, Jupiter, Saturn... in colour, and changing to IR filter if you go for Venus, now without colour but with better seeing as you block out the shorter wavelengths of the visible light.
😊👍💡

And the "sold out" should give you a hint for your choice. Sorry, I don't use ASIAIR.

best regards

Jesco

Sep 29, 2020

Pixel size is irrelevant for planetary imaging. You adjust focal length with Barlow until the sampling in "pixels/Airy-Disc diameter" is best (i.e. usually 2). For a camera with small pixels you use less focal length than for a camera with large focal length. The usual guideline is to make your focal length so that the resulting f-ratio is about 5x the pixel size in micron.

An ASI224MC with 3.75um pixels would need f/19. An ASI462MC hast best sampling at f/15. And an ASI178MC with its 2.4um pixels is best at f/12.

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