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DSLR versus CCD

DSLR CCD Cameras

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#1 Neil

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Posted 04 February 2013 - 02:24 PM

One of the most common debate in amateur astronomy is this one! Which is best a dedicated ccd camera or a DSLR?

 

Well Canon added fuel to this debate a long time ago now when it produced its first camera for astronomy, the 20Da. Since then a lot of people have started to modify their camera's by removing the IR filter. The industry responded by producing a replacement filter that improved the camera's IR sensitivity whilst also maintaining its auto-focusing system for day light photography. The list of modifications is increasing more and more each day, with cooler boxes and complete replacement cooled aluminium housing now being made!

 

Canon is even planning to produce a new camera soon!

 

Attached File  DSLRvsCCD_API.pdf   1.55MB   2235 downloads

 

The question is why? Since a DSLR cannot hope to match a dedicated cooled ccd camera, can it? No, but its closer than you might think as indicated by the above article and given the decreasing costs of DSLR's it is an attractive proposition with only a minor modification. 

 

Personally I believe the real scenario is as follows although not many of us will admit it!!! :D

 

1) Imagine you have just gone out to your favorite astronomy outlet and spend the families saving on a dedicate ccd camera for your hobby costing 3-5k€ .Now you need to explain to your wife / partner that you have just bought a camera that you can only use on clear Moonless nights when attached to your telescope? :o Do you think they will understand! Good luck with that one.

 

2)You have just gone out to your favorite camera shop and bought the latest Canon DSLR (If anything can a Canon can! B) ) and you secretly have it modified by a reputable supplier, now her in doors need never know since with a custom white balance nothing appears to be different and you can now take pictures of the family and scenery on your holidays as well as stars and nebula's - its a win win scenario as we say in marketing...

 

Whichever way you go, you should find the attached article very interesting.

 

Clear Skies

 

 

 

Neil.

 

 



#2 SlipperySquid

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Posted 04 February 2013 - 03:28 PM

Same conclusion as I thought! After all that testing,numbers, graphs and figures dedicated cooled CCD's are better than DSLR's.

 

Though what happens when you cool a DSLR that's the question!

 

Matt.



#3 RickS

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Posted 05 February 2013 - 12:54 AM

Interesting article, Neil.  There's a lot of good material on Craig Stark's site: http://www.stark-lab...articles.html. The 4 part series on signal to noise is particularly good.

 

I'm pretty happy with my Starlight Xpress H-18, SBIG STL11K and Apogee U16M cameras.  My DSLR never gets attached to a scope :)



#4 DENEB

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Posted 06 February 2013 - 05:48 PM

I disagree with all you Lot ! ... :D

 

DSLR's are the way to go especially with this lousy UK weather, neils post - point 1. Yea ! Go & buy a CCD & explain to your Family, you've bought a £3-5K camera you can only use about 5 times in a year if your lucky.... Oh! Yea don't forgot there are dealers will help you part with your family cash !

 

It will be a long time before I decide to part with my cash for a mono ccd again.

 

Custom Cooled Canon DSLR's.

 

http://www.centralds.net/cam/


Edited by DENEB, 06 February 2013 - 05:53 PM.


#5 AndyBooth

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Posted 07 February 2013 - 02:19 PM

mmm.. very interesting article.

As I will never be able to justify a CCD, I do use my unmodified 450D, to , for me, good results.

However always looking to improve, I would like to understand then, the following.

 

Using in camera dark removal, is that subject to same artificial scaling?

If no, then choice is to use that for more accurate results.

If yes, then, in say, DSS, should we use optimized scaling or not, even if darks are different temperatures?

 

regards to all,

 



#6 Neil

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Posted 07 February 2013 - 03:17 PM

First of all welcome to the forum Andy.

 

You have raised a very interesting point, my opinion would be to turn off the in camera noise reduction, since its a compromised algorithm designed for daylight photography and improving the shadow details etc... Then, even though a DSLR isn't temperature stabilized I'd still take dark frames and then let DSS work it magic... With an appropriate cool down period between shot I believe this solution will get you the best results.

 

Clear Skies

 

 

Neil.  



#7 DENEB

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Posted 07 February 2013 - 03:33 PM

On some occasions I have made a Dark Library for a certain area of the sky where I am imaging in. Like for example I would create a Library of Darks of ISO1600 of 5mins Subs for a particular region of the sky, such if I was imaging within the Orion region, with roughly in the same temps I can rely on just getting more RAW data of the object. A Library of Flats can be applied the same way.



#8 AndyBooth

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Posted 07 February 2013 - 06:56 PM

High Deneb, glad to join the forums!

i also currently construct a library of darks, clumping them in groups of temp within a 2 degree spread.

I don't have a issue with this approach, and it works well for me, but the article certainly tweaked my 

though processes.

I didn't realise the in camera setting also was 'weighted' in some way.

 

What ISO do you shoot at? and typically how many light frames and at what exposure do you use?

 Do you find less but longer, or more but shorter works best for you?

 

You can tell I'm a newbie!

 

here are my results so far, ignore the 2005 date I fudged the data entry.

http://www.astrobin....sers/AndyBooth/

 

regards,



#9 DENEB

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Posted 07 February 2013 - 07:26 PM

Andy, I tend to use mostly ISO800 on a few occasions I have used ISO1600.

 

When shooting at ISO800, my subs range from 4-10mins, but mostly 5mins.

 

At ISO1600 around 4mins. Regarding how many lights, depends on the object im imaging, the more data you have, the better.

 

The longest project was IC63, that was around 7hours of data via DSLR on a MN190.

 

Cheers

Nadeem.



#10 RickS

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Posted 07 February 2013 - 09:55 PM

There are two disadvantages of in camera noise reduction that I can think of.  The first is that you lose half your exposure time.  The second is that subtracting a single dark frame won't remove noise as well as a master dark constructed from multiple dark frames (the single ICNR dark frame will add some extra noise of its own!)  The advantage of ICNR is that the temperature of the sensor will be very similar between the light frame and the corresponding dark frame.

 

On balance, I reckon you'd be better off taking a set of conventional calibration frames rather than using ICNR.  Especially if you're using clever calibration algorithms like the ones in PixInsight that do scaling based on a noise analysis of the frames.



#11 Greg

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Posted 10 February 2013 - 09:48 PM

I have two CCD cameras and also a Nikon D3100 -- absolutely no argument in my mind which is the best! I regard my D3100 as a bit of a "boo-boo" (ie waste of money). If anyone insists on working with DSLR then go for a Canon - but if you can afford it go for a CCD.



#12 Carastro

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Posted 11 February 2013 - 08:41 AM

I have been using a DSLR for a couple of years and I loved it (450D), but got to the point where even with 7 hour exposures, I still could not get the noise down despite doing darks and dithering, so in August I bought myself an Atik383L Mono.  I was absolutely flabbergasted at the difference in sensitivity and amount of detail showing.  In September I went to Kelling Heath and did alternate nights with the Canon and the Atik using an Ha filter for comparison.  So much more showed up in the Ha than the DSLR images, so what i did was combine the two and got a nice coloured image with detail.  OK, it will take a while to learn how to combine the two and get decent colour. 

 

So whilst I really love the DSLR the Mono CCD wins.  Still learning to do filters, but have been combining some Ha images with previously done DSLR images where you can blur the colour (to smooth out the noise) and use the ha (or luminance) filter image for the detail. 

 

Obviously not every-one can afford to have both.

 

Carole



#13 Neil

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Posted 11 February 2013 - 10:03 AM

I have been using a DSLR for a couple of years and I loved it (450D), but got to the point where even with 7 hour exposures, I still could not get the noise down despite doing darks and dithering, so in August I bought myself an Atik383L Mono.  I was absolutely flabbergasted at the difference in sensitivity and amount of detail showing.  In September I went to Kelling Heath and did alternate nights with the Canon and the Atik using an Ha filter for comparison.  So much more showed up in the Ha than the DSLR images, so what i did was combine the two and got a nice coloured image with detail.  OK, it will take a while to learn how to combine the two and get decent colour. 

 

So whilst I really love the DSLR the Mono CCD wins.  Still learning to do filters, but have been combining some Ha images with previously done DSLR images where you can blur the colour (to smooth out the noise) and use the ha (or luminance) filter image for the detail. 

 

Obviously not every-one can afford to have both.

 

Carole

 

That's a very nice idea... going back and supplementing your original DSLR images with additional CCD data to lift the details etc...



#14 astrodoc71

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Posted 11 February 2013 - 10:18 AM

Forgetting about the noise properties for a second though, doesn't the DSLR have the same kind of bayer matrix in the sensor that a one shot color ccd does? If so then there are no clear pixels and with the bayer matrix 3 out of 4 pixels are totally blind to red......which is a kind of important color in the universe? So you are missing quite a bit there. 

The other important negative not discussed is that if you are imaging an object less than about 60 degrees altitude your resolution with a color sensor will degrade significantly due to the differential refractive properties of the color pixels. It's a very interesting article by Craig Stark but the conclusion has to be the same every time in my opinion as Carole has elegantly discovered!

Regards,

Dave


daveandtelescope.wordpress.com


#15 Captain Tweaky

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Posted 11 February 2013 - 12:27 PM

Is there an issue taking narrow-band images with a DSLR? I have a mono Atik 314L+ so there is no colour influence at all - it's all done with a filter-wheel. How does the sensor with the Bayer Matrix deal with narrow-band data and what sort of filter change system would you use? Or does it have to be a manual change between each one?

 

Yours aye - Cap'n


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#16 RickS

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Posted 11 February 2013 - 01:04 PM

Is there an issue taking narrow-band images with a DSLR? I have a mono Atik 314L+ so there is no colour influence at all - it's all done with a filter-wheel. How does the sensor with the Bayer Matrix deal with narrow-band data and what sort of filter change system would you use? Or does it have to be a manual change between each one?

 

You could use ***** in filters or a filter wheel to do NB with a DSLR or OSC.  The problem is that it's much less efficient that with a mono sensor.  With Ha and SII filters any photons that get through the filter can only be seen by the red pixels in the Bayer matrix, so you're only using 1/4 of the sensor.  It's somewhat better with OIII since you'll probably find both blue and green pixels will be sensitive at 501nm, or 3/4 of the sensor.

 

So, you can do narrowband with a DSLR or OSC but it's definitely not the ideal way to do it.

 

Cheers,
Rick.



#17 RickS

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Posted 11 February 2013 - 01:07 PM

What I attempted to write above was "s-c-r-e-w in filters" but it got filtered :)



#18 The rev

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Posted 11 February 2013 - 05:13 PM

I use both. CCD for my interacting galaxies and DSLR for star trails, constellations and creating wide field videos.

#19 JNieto

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Posted 11 February 2013 - 10:00 PM

Interesting debate. My experience goes pretty much with Carole's: I had (still have) a modified Canon 40D for many years, and really got to the limit with it: in noise, in sensitivity, and very important for me, in capability to deal with light pollution: for this I need to use narrow band filters. And, I can assure you I did try. I bought the Astronomik EOS-clip filters (the three of them, H-a, Oiii and Sii) and spend many many hours with the Canon + NB filters (that's when I got used to the multi-dozen hours images) and well... it was too much effort for a modest reward. So I got into the monochrome CCD world, and although I still invest many hours, the CCD makes a huge difference. For wide field astrophoto from remote locations, I still use the Canon, and it is fantastic. So, both options are desirable and possible, in my view.. just for different circumstances.

 

regards

Jesús



#20 Tinman

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Posted 16 February 2013 - 02:34 PM

I use a CCD/w filters. Got good results, but there is a bit more "learning curve" with one.

I have a friend who uses a DRSL for shots, and has got some stunning images..

The biggest thing with either, is tracking of the mount.

I think in my opinion, "If it aint' broke, don't fix it".

 

Tinman


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