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Redcat 51 III with the ASI533 MC Pro?

ZWO ASI533MC Pro William Optics Redcat 51 CMOS Refractors
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Dan Shallenberger avatar
Dan Shallenberger avatar
I see redcat and 533 questions all over the place, but I haven't seen my question answered.

I used to have a killer setup about 10 years ago and I was spoiled with it, but sold everything because my job just didn't allow me any imaging time at all. Recently, though, circumstances have changed and I am slowly getting back into it.

I have a redcat 51 III and I experimented slightly with my old dslr, but I am getting a dedicated camera very soon. For some reason I just don't like astro imaging with a dslr, especially when it's warm out (which it is here now and most of my time imaging will be summer). I want the 533 MC because of the price and reputation and I love the square sensor actually, and how it works with the ASI air (which I plan to get next as well). Everything I've read says the resolution should be between 1 and 2, but this combo is 3.1. No one seems concerned about undersampling though.

Am I overthinking this?
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Dave B avatar
Dave B avatar
I believe people drizzle the data to compensate, also there is now a 585mc pro with slightly smaller pixels that marry better to this focal length, worth looking into slightly smaller chip though.

Dave
AndreaMarini avatar
AndreaMarini avatar
Hi.
i don’t know why I don’t see your posts. Sorry for that.
if you are going to undersample you images I know there are some technics to adjust it in post production, for example with drizzle file. It is very strange because I see a lot of shots done using red cat and asi2600 that has same pixel size of the asi 533. I have that asi 533mc pro and it is a great camera. I use as newton 150/750.
some resources(you can find a lot of those)
https://youtu.be/A10YSZ2Z8-U?si=xXy05B9iKXd6v1uQ

https://youtu.be/ItmrAZyLeek?si=nSxRYd6GBsC0H3Dl

https://youtu.be/Ytyl1c-6uU0?si=mIY6dDpTPZ-Nddao
Johnny_Utah9 avatar
Johnny_Utah9 avatar
I use the 533 with the Redcat 51. Undersampling was also one of my concerns when I purchased the camera. Most people told me that I was overthinking it as well. After using it for about 6 months, I have no complaints. It is an amazing camera. As others have commented, when stacking your photos in Pixinsight, you can drizzle undersampled pixels (that is if you have Pixinsight).
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Andrew Hazon avatar
Andrew Hazon avatar
I use the asi533mc pro on both my skywatcher 130pds and Rasa 8, I dither and drizzle so images come out great although on the rasa I’ve notice the stars are starting to be a bit blocky so I’ve just purchased an asi183mc pro for the rasa which will give be better resolution.
Bronco Oostermeyer avatar
Bronco Oostermeyer avatar
Although I have no experience with this combination (I use an Espit100ED), but I do know if you want to compensate for under sampling, make sure that you dither. I Love my 533MC  pro with its square sensor!
Daniel Tomcej avatar
Daniel Tomcej avatar
I have a Redcat 51 III (WIFD), and use it with my ASI533MC Pro. I too overthought the situation. TL;DR: Its a great combination, and is super forgiving. Dithering your subs, and then drizzling in post can (and does) yield even better results. I will be upgrading to the ASI2600MC Pro soon, which has the same size pixels, but will give a bigger FoV. I don't have any reservations about the pixel size (as noted earlier, the 533 and the 2600 have the same pixel size).

This is definitely a case where the math say that it isn't "optimal", but I guarantee you that you won't be disappointed.
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David Foust avatar
David Foust avatar
I use this combo (though with the redcat II) and you can see how the combo works with all the pictures on my gallery. I don't drizzle my images, but I dither. I think they turned out good enough. Don't overthink it!

Using the dedicated cam with the Asair+ is so much more convenient and easy to use than with a DSLR (I started with an EOS R) and I'm getting much better results.
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Dan Shallenberger avatar
Dan Shallenberger avatar
Thank you so much everyone. I appreciate the comments. I will stop over-thinking and just go for it!
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Jonathan avatar
Jonathan avatar
Short answer, you're likely overthinking it. With the small aperture of the redcat51, you're more at the mercy of things like Rayleigh's limit, so smaller pixels won't necessarily mean better resolution. 

In practice, I used to shoot with the 183mc/mm with tiny 2.4µm pixels, but I ultimately switched to the 533mm because of the amp glow of the 183 sensor. Now that I've been using the 533 sensor for a few months, I haven't noticed much of a difference in resolution. Even when comparing shots on the same target, it was pretty hard to make out any real difference between them.
As long as you're fine with the square sensor, the 533 is great. There's always trade offs in this hobby, and the trade off for the portability/relative light weight of the redcat51 is the small aperture and all that comes with it.
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AoP avatar
AoP avatar
I really wouldn't dwell on the sampling. I use the 533 and the 2600 on my Redcat and they both produce wonderful images. I do dither every third image when shooting 180 seconds or more and maybe every five when shorter. I did however use the 183 a lot with the Redcat and i felt it produced sharper images. This may be due to my sky conditions which are bortle 7-8 and almost never good seeing.
Stick with the 533. You'll love it.
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Oscar avatar
Oscar avatar
if you're getting the 533, go for the 2600 instead

you'll regret not getting the bigger FOV
Levi avatar
Levi avatar
As messierman3000 said, the 533 is a great choice but the bigger fov with the 2600 is definitely a big step up. Big price difference though.
Jeff Fishman avatar
Jeff Fishman avatar
I use the 533 with the Redcat 51. Undersampling was also one of my concerns when I purchased the camera. Most people told me that I was overthinking it as well. After using it for about 6 months, I have no complaints. It is an amazing camera. As others have commented, when stacking your photos in Pixinsight, you can drizzle undersampled pixels (that is if you have Pixinsight).

I use same setup and have had no issues.
Ryan Faulkner avatar
Ryan Faulkner avatar
if you're getting the 533, go for the 2600 instead

you'll regret not getting the bigger FOV

A Redcat is already a very wide FOV, and the 2600 is twice the price.

With that being said, I have the 533 that I use with a William Optics GT71 and FLT-120. I will eventually move up to the 2600 on the FLT-120.

If you want to compare FOVs, check out https://astronomy.tools/calculators/field_of_view/ or enter your telescope and sensor into Stellarium. That's what I use to figure out which scope to use each night.

If you're not fully committed to the ASIAir, I would suggest checking out some alternatives. Personally, I don't like how ZWO claims open source technology for its own and then locks out other manufacturers.
If you link to tinker, you can build a very similar setup using a Raspberry Pi and StellarMate, or roll your own Linux setup.

NINA and a micro pc are also extremely popular.

As for undersampling/oversampling, we're not given much choice from the manufacturers. SONY (which most cameras use) seems to be standardizing on the 3.76 pixel size. Yes, you can find other cameras with smaller or larger pixels, but 3.76 is becoming the "standard."
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