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DBK 21AU618.AS vs Mallincam

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#1 Moromete

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Posted 28 March 2013 - 06:23 AM

Considering the big price difference in favor of the Imaging Source camera and maximum useful exposure time of up to 1 minute (to avoid autoguiding), isn't the DBK 21AU618.AS (with Sony ICX618AQA sensor) more appropriate for live video DSO than Mallincam for someone who uses only a PC for live viewing instead of a CRT TV?

Similarities:
- DBK 21AU618.AS and Mallincam have the same Sony ExView HAD CCD sensor
- long integration time of up to 60 minutes for both cameras
- live DSO viewing ability
- up to 36db manual gain increase for DBK 21AU618.AS
- resolution quite similar
- C-mount adaptation
- no IR filter.

Differences:
- much cheaper DBK 21AU618.AS
- Mallincam has double pixel size than DBK 21AU618.AS
- 1/2" sensor (Mallincam) vs 1/4" sensor (DBK21) => bigger FOV for Mallincam
- lack of active cooling for DBK 21AU618.AS in contrast with Mallincam
- DBK 21AU618.AS better for planets due to smaller pixel size
- DBK 21AU618.AS easier to operate from in house PC via USB cable extension.

For exposures of maximum 1 minute I see no important advantage for Mallincam other than double light gathering capability due to double pixel size. Considering the big price difference I can cope with half sensitivity and FOV of DBK 21AU618.AS.



Are my assumptions correct?

Does anyone know how much noise DBK 21AU618.AS has at maximum gain and 1 minute exposure?

#2 Moromete

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Posted 28 March 2013 - 06:39 AM

I forgot to mention that maybe due to the smaller sensor (1/4" vs 1/2")you can use stronger focal reduction with the DBK 21AU618.AS than Mallincam.

Imagine using a F/1.5 focal reduction (like mattlastro's reducer from another post) with the DBK 21AU618.AS without vignieting or significant optical aberrations visible!

Maybe with DBK 21AU618.AS an SCT user can use a cheap 1.25" x0.5 reducer after a Meade x0.33 reducer and get down to F/1.7 without vignieting or significant optical aberrations visible due to its diagonal of only 4.5mm!

#3 GlennLeDrew

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Posted 28 March 2013 - 09:30 AM

The smaller pixels and lack of cooling will play significant roles. Obtaining *actual* focal ratios of less than about f/2.5 using available reducers on telescopes will be difficult (as I pointed out in the thread mentioned.)

#4 Chris A

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Posted 28 March 2013 - 09:58 AM

The reason for the cost difference is because of the important extras you get with a Mallincam which make a huge difference esp. when viewing deepsky objects. Again these extras are.

- Mallincam has double pixel size than DBK 21AU618.AS
- 1/2" sensor (Mallincam) vs 1/4" sensor (DBK21) => bigger FOV for Mallincam
- lack of active cooling for DBK 21AU618.AS in contrast with Mallincam

You do not mention what your main interest are such as planetary or deepsky observing? The DBK 21AU618.AS is more suited for planetary and lunar where as the Mallincam is superior for deepsky.

This topic is flagging a dead horse and it has been discuss over & over. At the current time you just cannot beat a Mallincam for it's value, built quality and sensitivity for deepsky observations.

Chris A
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#5 Chris A

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Posted 28 March 2013 - 10:08 AM

I will add to the fantastic points that Glenn has previously mentioned to your post. Yes you can use a focal reducer to kind of makeup for the half size ccd sensor but you must remember that when using a reducer to such extremes, the DSO of interest (galaxies, planetary nebulas etc.) will start to become very small to observe on your screen unless you plan to look at it by putting a magnifying glass up to your screen :lol:

Also you have already lost the sensitivity by having much smaller pixels for DSO and now will lose the benefits of resolution when dramatically reducing your focal length.

Chris A
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#6 Moromete

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Posted 28 March 2013 - 12:02 PM

Chris I have specified in my first post that main interest is live video observation of DSOs.

I have to disagree with you regarding DSO size when using a strong focal reducer. In fact, in my humble experience, a 1/4" sensor will "magnify" the image 2 times more than a 1/2" sensor.

Lastly, maybe for you such topics are like dead horses because you have lots of money to spend on astro gear and already have a Mallincam. Lucky you than! ;)
I'm not interested in Mallincam's value or built quality but just in its price/performance ratio.

#7 Dwight J

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Posted 28 March 2013 - 12:51 PM

The DBK camera is less than ideal and an economical alternative is the Samsung line of cameras which are proven performers.

#8 Moromete

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Posted 28 March 2013 - 01:49 PM

I agree with you Dwight but Samsung CCTVs have too short exposures of only 8/10s and you don't reach mount's limits without autoguiding of 30-60s.
Secondly Samsung has AGC which must be kept on Low to avoid washing out the image.
Otherwise a Samsung SCB-2001 seems quite attractive for the money and having a Sony Super HAD II CCD sensor.

Mallincam sensor has a sensitivity of 1400mV.
DBK's sensor has a sensitivity of 1000mV.
SCB-2001 has a sensitivity of 2250mV.
In my understanding 1000mV=6dB.
DBK has manual gain adjustable between 0-36dB.
Considering you have to keep AGC on Low on SCB-2001 than DBK will equal Samsung's sensitivity after a 7dB gain increase and after this it has a gain advantage of roughly ~25dB (or a 4000mV sensitivity gain) without washing out the image and keeping the colors.

#9 Dwight J

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Posted 28 March 2013 - 03:09 PM

Not having seen a DBK in action, it is hard to compare cameras. I have seen the Samsung ones on NSN. Screen shots just don't convey what the particular camera can really do. I wouldn't be afraid to try out the DBK to see what it's capabilities are as we are often limited by what equipment we have on hand.

#10 jonbosley

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Posted 28 March 2013 - 03:40 PM

The DBK21AU618 is an excellent planetary imager. The small sensor and pixel size makes it much more limited for DSO. It has no cooling and has very high noise levels for long exposures. Outside of planetary imaging in no way can it be-compared to a Mallincam.

#11 Ed Wiley

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Posted 28 March 2013 - 03:59 PM

I tried a bit of live view with my DMK21AU618. Great for Luna and Jupiter. I haven't tried a Mallincam, but the DMK is not the tool for live viewing of DSOs IMHO. It is great for another imaging task not mentioned, double stars.

Clear skies, Ed

#12 Moromete

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Posted 28 March 2013 - 04:13 PM

Ed, can you shares with us why your DMK21AU618 is not good for live viewing of DSOs?
As an owner of such a camera your opinion is valuable. Thx.

#13 jgraham

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Posted 28 March 2013 - 05:54 PM

Hmmm, I've used my older DBK21 to observe deepsky objects using 15 second exposures and I was impressed. It is no Hubble, but not at all shabby. If you have an Imaging Source camera there is no reason not to give it a try, but I wouldn't buy one with the idea of using it as a deepsky camera.

#14 Chris A

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Posted 28 March 2013 - 07:03 PM

Sorry I did not realize that you mentioned your interest on another post, I really do not read all the posts on the forum. Your title specifies "DBK 21AU618.AS vs Mallincam "
and to me that includes value & built quality.

When I said flagging a dead horse is because it seems to come up often comparing a certain camera to a Mallincam for DSO observations and they all have their pros and cons.

Chris A

#15 Ed Wiley

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Posted 30 March 2013 - 10:57 AM

I think John said it all -- yes 15 second exposures will show you something and not bad for this kind of camera, but that is not live viewing its AP. On the other hand, I consider my DMK21AU618 and outstanding high-resolution camera and suspect it will beat the socks off the large pixel Mallincam for imaging doubles that at 1" separation or the craterlets in Plato. Different cameras, different functions different strengths.

Ed

#16 Moromete

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Posted 30 March 2013 - 12:12 PM

Chris, no problem. But I still think the horse is not dead yet.

Ed, could you post a single exposure of 20s of Running Man nebula with your DMK21AU618 and WO66ED with AGC Max?

This way I'll be able to compare it with mine taken with ST80 and my CCTV at 20s exposure.

PS: I agree 15s is not quite live viewing but Mallincam owners go up to even 2 min or more. Problem is current video technology available to us is has it's shortcomings and needs prolonged exposures. I'm ok up to 30-60s.

#17 mclewis1

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Posted 30 March 2013 - 06:33 PM

I can't believe we're still having this discussion. The DMK isn't even in the same league as the Mallincam on DSOs.

The Mallincam starts with a sensor that's 60% more sensitive (comparing an EXView HAD in both cameras) ... and the sensitivity comparison only gets worse if you want color images. The larger fov from the larger sensor in the Mallincam also makes for a more enjoyable viewing experience.
The DMK is an 8 bit camera, the Mallincam is a 12 bit. The gain circuitry in the Mallincam is optimized for low light operation. Then there's the built in cooling. All of which means much better sensitivity and signal to noise ratios in those low light conditions. It's also part of the reason why the Mallincam is almost 3 times the price of the DMK.

To answer your question ... the Mallincam would actually be more appropriate for live viewing. The better sensitivity means shorter exposures to achieve the same image density, and the shorter exposures mean more accurate tracking. Yes you have to handle a more complex setup (video through a frame grabber, separate control and power connections) but you're getting substantially better sensitivity as the trade off.

What would be more interesting to me is a comparison between the $500 video cameras with their shorter integration times and the DMK. High quality planetary cameras like the DMK have come a long way (especially when using the great Sony sensors) and are certainly much more versatile than the older webcam derived technologies ... but just because they can perform longer exposures doesn't mean that they're comparable to cameras specifically designed for that type of work.

#18 jgraham

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Posted 30 March 2013 - 08:05 PM

"that is not live viewing its AP"

Huh? Where did that come from? Does exposure time determine live viewing vs AP? If it does then most of the cameras that are discussed in this forum aren't live viewing either. Live viewing with an Imaging Source camera is like live viewing with any other camera; spontaneous and in real-time.

Is the DBK21 'better' than some other camera? One would hope that a camera costing many times as much would be 'better', but no one can make that judgement for someone else. This vs that is an invitation to compare and contrast, not to pontificate which is 'better'.

There are any ways to participate in camera-assisted observing. The DBK21 is certainly capable and it would be interesting to give it a thorough testing in this role. It would be neat to be able to offer this as an option for someone on a budget (my hand is up). In contrast, the Mallincam is purpose-built for this activity and by all accounts it does a fine job.

So much to try, so few clear nights...

#19 Ed Wiley

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Posted 30 March 2013 - 08:32 PM

Hi Moromete: I only do high resolution imaging with my DMK21, sorry, no Running Man. I am running at F22.5 and the little 66mm is in the box right now as I do not guide the DK. I would try the Image Source web site, there are probably DSO images there.

Ed

#20 Lorence

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Posted 31 March 2013 - 01:57 PM

"that is not live viewing its AP"

Huh? Where did that come from? Does exposure time determine live viewing vs AP? If it does then most of the cameras that are discussed in this forum aren't live viewing either. Live viewing with an Imaging Source camera is like live viewing with any other camera; spontaneous and in real-time.


A while ago I would have said the main difference between live viewing and astrophotography was the image processing involved in AP. A live or near live viewer just sees what the camera sees.

A few recent developments have changed that idea somewhat. I use Deep Sky Stacker Live to stack images as they are downloaded from my Universe. The stacking acts like a filter to clean up noise generated by the camera. I watch the stacking process on the screen as it take place. I'm viewing near live but with some image processing taking place between the camera and the screen. Where does that fit into viewing? It's not video but I view it as though it was video. It's not AP because I don't save the images and post them for all to see.

If that wasn't enough to cloud the issue there is software available that processes live video as you are viewing. Similar to the type of processing done by the astrophotographers but the processing is taking place as the image is being viewed. No longer just seeing what the camera sees but using processing to see the video image the way you want to see it.

It's called Video and Electronically Assisted Astronomy. At what point is it no longer video but electronically assisted viewing. Personally I don't care what it's called, I just enjoy it more and more with every new development.

#21 Moromete

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Posted 01 April 2013 - 10:59 AM

Mark, John said his old DBK21 does a good job on DSOs with longer exposures. I think he knows what he is speaking as a DBK21 user.

Yes, the new DBK21 with ExView sensor is 60% less sensitive than Mallincam and is only 8bit vs 12bit. But neither the price is the same. For a 60% difference Mallincam is 3-4 times more expensive which is too much for me. Nobody says Mallincam is not the best for live video astronomy.
So Mark don't be so surprised we are comparing DBK21 to Mallincam under these circumstances. Nobody said DBK21 is better or the same with Mallincam.
But don't forget that price is very important for some of us and the planetary bonus DBK21 has.

The question is how much worse is DBK21 compared to Mallincam considering the big price difference.

I know there is more noise with the new DBK21 than Mallincam due to lack of cooling especially but I wonder how much more noisy is in practice DBK21 after 1min exposures.

I just feel the new DBK21 has DSO potential for the money but I don't know how much. That's all.

Don't forget that due to smaller sensor one can use stronger focal reduction with the DBK21 than Mallincam without vignetting and DBK21 can recuperate its sensitivity handicap this way.

John could you help us with some answers regarding:
- for live viewing on my laptop of DSOs with DBK21 at exposures of say 1 min each, do I have to record movies on my HDD or that's not mandatory?
- could you show us some images or an Youtube movie of Running Man or M51 (or other faint DSOs) taken with 1 min exposure and maximum Gain to see how much noise the camera generates?

#22 mclewis1

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Posted 01 April 2013 - 12:42 PM

I never suggested that the DBK can't do DSO work or that it isn't a great value as a planetary camera that can do some other work too. I was primarily focused on your comment/question about the DBK being "more appropriate for live video DSO than Mallincam ...".

I think it is very valid to question "how much better" or "how much noise" and to look into actual comparisons.

Your point about the smaller sensor being able to handle more aggressive focal reduction is a very valid point for small objects. This would be very apparent on smaller galaxies for example.

I don't think John said it would do a "good job on DSOs", he did say he was "impressed" and that it's "not at all shabby" ... but he also said he wouldn't suggest buying a DBK specifically for DSO work. But if the DBK capabilities worked out for you I think that would be great because I think we need more DSO cameras in this price range.

I'm totally in line with your desire for a reasonably sensitive, easy to use camera with a 30-60s maximum exposure capability that priced in the $500-700 range. I see this as a really under served "sweet spot" in the market. There are tons of alt az goto or small gem mounted scopes around that were purchased by folks who have very restricted budgets (for example high end Mallincams are out) but would still love to do near live viewing. This would be a very strong market for a good 30 second camera at a reasonable price.

I'm also very curious about the upcoming Starlight Xpress SX Video camera.

#23 Ed Wiley

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Posted 01 April 2013 - 08:13 PM

I'm not about to get into a debate parsing what is live view and what is AP and what is video observing. Everyone can have it their way so far as I am concerned. :grin:

Ed

#24 akjudge

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Posted 02 April 2013 - 08:18 AM

Interesting thread... I have a DMK that I use mainly for lunar/planetary viewing. Have not tried it on DSO's since I use my Stellacam3 for DSO's.

But getting back to the idea of a cheaper alternative to the Mallicam (great camera), has anyone tried the ASI120MM camera? Specs say it has a resolution of 1280x960 @ 35fps. Exposure range up to 1000s (16 minutes). It is USB and sells for less than $300.

Here is a link to the specs:

http://www.zwoptical...SI120/index.asp

More interestingly, here is a link to actual images. While most are lunar/planetary, there are several DSO images that look very impressive (middle of the page):

https://www.google.c...ch&tbo=u&amp...

I am just curious whether anyone has any DSO experience with this camera (which is priced at 1/6 of the Mallicam)?

Jim


#25 jgraham

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Posted 02 April 2013 - 12:17 PM

I was just going to make a comment about the ASI120MM. This looks like a very interesting camera along the same lines as the Imaging Source and Point Grey cameras. I'm waiting to hear whether a bid I placed on a scope was successful or not. If not I may have to drown my sorrows by picking up one of these. :)






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