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#1 Emanuel

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Posted 23 October 2020 - 03:55 PM

How do you choose the correct Cmos camera for your telescope? By its focal length?

I will by a new camera, as soon as the new Red Cat 71 is out. I believe that is F/4.9, at 350mm. Ive been looking into the new ZWO 533 MC, but at the same time, there`s the 294 and the 183; i am even considering the 2600. So, what is the criteria to decide between them? Pixel size? tongue2.gif


Edited by Emanuel, 23 October 2020 - 03:56 PM.


#2 bobzeq25

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Posted 23 October 2020 - 04:41 PM

All those cameras can work.  Experienced imagers sweat this decision a lot, and bring in many considerations.  They're likely not all that relevant to you.

 

Chip size is a biggy, that sets your field of view.  The tiny pixels of the 183 will work well with your 350mm F4.9 Redcat.  I use my 183s (I have both) with a 400mm F2 C8 RASA.  It's pretty much a niche camera, the others are more general purpose.

 

The 2600 is an excellent general purpose camera, at a cost.  The 533 is the same, but with a smaller chip.  Those would be my recommendations.


Edited by bobzeq25, 23 October 2020 - 04:41 PM.

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#3 Emanuel

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Posted 24 October 2020 - 02:08 AM

I see. The odd is that ZWO now has three cameras that basically have the same price tag, so it makes things a little difficult to choose.

I think that the 2600 is from another level , but its way more expensive. And another odd thing to me, is that the 533 has a square field of view, it is a good thing or its just me? Im used to the NikonD5300 field , and when i simulate any target on Stellarium, looks odd. I dont know...tongue2.gif


Edited by Emanuel, 24 October 2020 - 02:09 AM.


#4 Stelios

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Posted 24 October 2020 - 02:51 AM

Image scale is a good *initial* guide. With a 350mm scope you have:

 

ASI533MC: 206.3*3.7/350 = 2.22"/px  undersampled

ASI183MC: 206.3*2.4/350 = 1.414"/px well sampled

ASI294MC: 206.3*4.63/350 = 2.72"/px undersampled

ASI2600MC 206.3*3.7/350 = 2.22"/px undersampled

 

Undersampling is not fatal--you get square stars, but you can recover by dithering (during acquisition) and drizzling (in processing). You need to take a lot of exposures for good results though.

 

Other criteria: Field of view (Go to astronomy.tools (imaging mode) and put in your camera and scope F/L, and see how various DSO will frame). The ASI533 and ASI183 are roughly the same size (but one is square and the other rectangular), the ASI294 is larger, and the ASI2600 is largest.

Additionally, the ASI533 and ASI2600 are latest technology with no amp glow (amp glow can be calibrated out, but no amp glow allows scalable darks).

 

The ASI183 is a 12-bit camera, the ASI533 and ASI294 are 14-bit, and the ASI2600 is 16-bit. The more bits the better the resolution, *but* you can compensate by shooting a *lot* of images with lower-bit cameras. If your total integration time is in multiple hours, it probably doesn't matter (much), if it is smaller then the higher bits have a distinct advantage.

 

Hope I didn't add to the confusion. If you want a recommendation: The ASI183 is the perfect match for a 350mm scope, but if you have bigger scopes as well, you will like it less. The ASI2600 is a standout in this group, but a pricey one. If you can't afford this, then it becomes a tradeoff between the extra under-sampling of the ASI294 (a minus) and the smaller FOV of the ASI533 (a minus). As the 350mm rates to give me an adequate FOV anyway, I might go with the ASI533, but check out the calculator above and make up your own mind.


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#5 Emanuel

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Posted 24 October 2020 - 03:21 AM

Excellent Stelios! Your informations are precious! Im re-fitting all my gear, to be , first, highly portable, and then fully automated, with PC free. Sold my Ioptron Ieq45 and bought the RST135. Now i will sell my Tak 106 and buy the Cat 71 and i will sell my NikonD5300 and go for a CMOS. Why im doing this? Exactly what you said, my total exposure time on any given target rarely goes beyhond 1h, 2h or a little more. So, im eager to change this situation, to improve my images quality.



#6 dan_hm

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Posted 24 October 2020 - 10:24 AM

The only thing I would add to Bob's and Stelios's advice is that you should consider whether you want a mono or OSC camera. There are tons of threads on this topic so we don't necessarily need to go into it, but it's an important consideration.


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#7 sn2006gy

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Posted 24 October 2020 - 11:24 AM

I'd say the 533 can't be beat if you want ultra portable, quick set up and short-ish integrations.  Get an Optolong L-Extreme for NB and a L-PRO for LP filter (if needed) and just let it rip. The 533 is super forgiving, even though under sampled is the same under sampling the 2600 or even 6200 would have so it can be re-sampled in software and dithering (which you want to do anyway!)

 

2600 gets into some tilt/image circle issues, the 183*.* really needs more integrations to over come its noise and ampglow in comparison and i have no experience on the other camera.

 

Just can't recommend the 533 enough.


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#8 rgsalinger

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Posted 24 October 2020 - 12:35 PM

I'd recommend an IR/UV filter rather than an LP filter if you are going to a dark sky site. When I switched to one with my ASI071, the images were greatly improved. I guess that the consensus is that it's more likely that an LP filter is the thing to get but you don't need one at a dark site.

 

Even at 1.4 arc seconds per pixel, I suspect that you will still be under-sampled so look into dithering and drizzling your images once you get the hand of the camera. Those techniques can really make the results much nicer.

 

Rgrds-Ross


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#9 Emanuel

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Posted 24 October 2020 - 02:52 PM

Color for me!! I had my share of mono, and its not suitable for my current work situation, Maybe in the future.

And not only that! With the evolution of these new cameras, more and more is justifiable to go for a color camera over the mono.

I do have a Optolong L-Enhance filter, that im using on the NikonD5300, with excellent results. I always dither every image, so, that situation of under-sampling should not be a issue. Im just a little worried about the square sensor of the 533. Its odd, isnt it? Or in the real world is not that strange??



#10 sn2006gy

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Posted 24 October 2020 - 05:07 PM

I found it wasn't that strange. No reason to worry about framing much as its square and you don't crop much if anything because it fits the prime image circle of just about any scope you throw at it.


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#11 Michael Covington

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Posted 24 October 2020 - 06:08 PM

A square field of view is a good thing.  The image formed by the telecope is round -- not elongated.  A square sensor makes the most of it.

APS-C sensors are 1.5x as wide as they are tall, not because of any law of optics, but because they are scaled down from a full 35-mm frame.

 

35-mm film frames are 1.5x as long as they are wide because Oskar Barnack, building the first 35-mm still-picture camera about a century ago, decided that a 35-mm movie frame was too small, so he used two of them together.

1.5x is the longest and narrowest aspect ratio that has ever been standard for photography.  There is a much older photographic tradition of using square negatives (e.g., Rolleiflex, Hasselblad) because they are a better match to the round area covered by a lens.  There are also formats that are somewhat but not extremely elongated, such as traditional movies and TV (1:1.33) and the 6x4.5-cm format used by some cameras on 120 film.


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#12 AhBok

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Posted 24 October 2020 - 06:50 PM

Another nice thing about the square format is much less need for camera rotation.
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#13 Emanuel

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Posted 25 October 2020 - 08:12 AM

OK, it looks that we have a winner. The 533  flowerred.gif


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