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Astrosurf

Better Planetary Cam?

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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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I think perhaps the ASI224MC would fit your requirements.  A very capable planetary camera.  Not sure what you might find for a similar price that is better.

James

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

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Doubtless slightly rude but... I’m looking for a 120mc if you are interested in selling...

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Just now, Mr niall said:

Doubtless slightly rude but... I’m looking for a 120mc if you are interested in selling...

Lol! I'll want to keep it I think. Might try it as a guide cam if colour is OK. Sorry!

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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 had the monochrome DMK21 (ICX618 version) and replaced with the ASI120MC for planets, and the ASI174MM for solar H-alpha, and never looked back. The DMK/DBK cameras were excellent in their day, but they are older technology

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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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Thanks guys. I want a small FOV so would small pixels be best? This is something I don't really understand.

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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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Actually a decent FOV is quite handy when you're trying to find the target, too :D

James

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I've got a bit more dosh so am undecided about the 224MC or 290MC. I want to do planets to improve quite a bit on my 120. I would be using a 3x Barlow on my 200P, so a FL of 24. And USB 3. Any further advice? 

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The 200P plus 3x Barlow yields F/18, which matches the pixel size (3.75 micron) of the ASI224MC better than that of the ASI290MC (2.90 micron). I have the former, and like it a lot.

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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

Edited by Tommohawk

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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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Rats!

This thread is convincing me I need a basic tracking base so I can do planets with my 10" dob at silly magnifications...

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