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Better Planetary Cam?


Astrosurf

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I have an old ZWO ASI120MC cam I got second-hand which I don't think is USB3. The frame rate isn't great. I want to have a better cam but really don't want to spend more that £250. I would prefer a colour version as I can't be bothered to faff about with filters (no debate on the merits of mono over colour please! I know!) Not a bigger sensor as I don't want a bigger FOV. What would you recommend, and why?

Alexxx

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The ASI290MC might be worth a look, but I have the mono version rather than the colour one and don't really know how well the colour one performs, so it might be worth looking around to see what people are achieving with that.

James

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9 minutes ago, Astrosurf said:

Someone's selling a DBK21 for £75. Is that a good cam compared to the ones you've recommended?

There are two models of the DBK21 as far as I recall.  The one with the ICX618 sensor is the better one, but I believe the 224MC is more sensitive.  The DBK21 will probably also be USB2, so you're stuck with the lower frame rates again.

James

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2 minutes ago, JamesF said:

There are two models of the DBK21 as far as I recall.  The one with the ICX618 sensor is the better one, but I believe the 224MC is more sensitive.  The DBK21 will probably also be USB2, so you're stuck with the lower frame rates again.

James

Many thanks.

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I'm using a ZWO ASI290MM and I've found it excellent, and it doubles nicely as a guide cam. Last night on Mars I had around 350 fps. (red channel, usb3, laptop has 4gb Ram)

Also I had the colour version previously and found that excellent too. TBH when I switched to the mono I could see little difference though my technique probably wasn't 100% at that stage.

Bear in mind 290 has small pixels so need to think about image scale. I use it currently with Quattro 10 and x5 powermate. Probably oversampled, and dimmer targets need high gain to get sensible fps. esp in G an B. 

I'm guessing this would be about right £ for pre owned 

 

 

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FOV probably isn't something you need to worry about as you can configure the camera to crop the frame (at least with the ASI cameras).

The advantage of smaller pixels is that you don't need such a large focal length to achieve the same resolution image.  With the ASI120 and ASI224 a focal ratio of around f/18 to f/20 is probably optimal so you'd use barlows etc. to try to reach a focal length that put the focal ratio into that range.  The smaller pixels of the ASI290 mean you'd probably be aiming nearer f/14 to f/15 which is perhaps easier to achieve with (for example) your 200P.  The disadvantage is that all other things being equal, smaller pixels are less sensitive.

Of course all other things are rarely equal.  Improvements in technology can mean that smaller pixels on more modern sensors can be just as sensitive, if not more so, than larger pixels on sensors using older technology.

James

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  • 2 months later...

Hi Alex. Following on from my earlier comments, theoretically I would agree with Michael, but I think the ASI290 is a bit of an exception.

The ASI290 when barlowed would be - theoretically -  oversampled, and the resulting imaging could suffer from 2 problems. The image might be big, but blurry - the exposure time needs to be longer because of the higher F value, so you don't get so many frames per second and each individual frame may suffer blurring due to movement caused by turbulence.

However, because the ASI290 has such a high potential gain, in practice it seems possible to achieve good results even at F25. 

The image below was taken with a SW200PD and x5 powermate yielding approx F25, though probably nearer to F23. 

Couple of caveats. The powermate is bonkers for performance and probably a conventional barlow wouldn't perform quite so well. Also this is using the ASI290MM, but I had the colour version before and got similar results. Also, if you look at a dimmer target the FPS will drop off somewhat. Also with such a small FOV image location can be a problem! 

On the flip side, this was done with with Jupiter at only 34 degrees -  which reduced the signal compared to a higher elevations. (That said of course the planets are all a bit low ATM)

I think its a remarkable result for a scope that cost about £160!! Ahh one last thought - this is the the early 200P, not PDS, which has a smaller secondary so smaller central obstruction - I'm convinced this has a positive impact for planetary work. (52mm vs 58mm IIRC)

Whichever way you go, I think you'll get great results!

Edit - BTW even with USB 3 I struggle to get the theoretical FPS rates - ideally you would have a SSD also. Not sure how much difference that would make, but I'll find out later this week - Ive just ordered one!

2017-05-24-2129_4-R_pipp_g5_ap76RS-L20RGB_RS_PS.png

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I'm another vote for the 224MC, which has provided excellent some excellent results when I've had the chance to get out!

The camera delivers high frame rates, even at F20 on my 10" OO (TV 3x barlow with some extension), commonly over 120fps on  640x480 ROI.    The camera's sensitivity has been a big step up from my previous QHY5LII mono (ASI120MM equiv) and much less fuss with the processing - though worth stressing that best results do require the ADC (particularly for planetary imaging from UK Latitudes).     A capture laptop with USB3 and a decent SSD drive can also bump the price up if you don't already have them.

 

2017-05-09-2205_2-JG-L_web.png.738fcf590be273cb7b18d92adb133330.png

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5 hours ago, SnakeyJ said:

I'm another vote for the 224MC, which has provided excellent some excellent results when I've had the chance to get out!

The camera delivers high frame rates, even at F20 on my 10" OO (TV 3x barlow with some extension), commonly over 120fps on  640x480 ROI.    The camera's sensitivity has been a big step up from my previous QHY5LII mono (ASI120MM equiv) and much less fuss with the processing - though worth stressing that best results do require the ADC (particularly for planetary imaging from UK Latitudes).     A capture laptop with USB3 and a decent SSD drive can also bump the price up if you don't already have them.

Thats an excellent image - I might change my vote!

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