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ABG or NABG? 16803 vs. 16801 chip

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#1 prefetch

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Posted 08 July 2014 - 09:25 AM

hi all.

i'm thinking about taking the plunge and buying a 'high(er) end' camera with a larger CCD - but I'm sort of stuck on this particular decision.

here's my situation: i live in a red zone in salt lake city.

the 16803 has a QE in the 50-60 range, with ABG
the 16801 is a bit higher in the 60-70 range, with NAGB

so my question is, is the difference in QE going to be noticeable? given my light pollution problem, is it worth giving up anti-blooming for a 10-20% increase in QE?

i'm not sure how to make this decision. i've read the "pretty pictures vs. photometry" idea, and i don't have interest in photometry - but i do have interest in mitigating my light pollution as much as possible, and i plan on doing a fair amount of narrowband imaging because of it.

so in this case, the 16801 would make sense, but i'm sort of freaked out by blooming. i've been using an atik 460, and so i just haven't had to deal with blooming and i'm not sure if it's going to be a major regret of mine. how crummy is blooming?

any guidance would be very much appreciated.

#2 garret

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Posted 08 July 2014 - 09:45 AM

the 16803 has a QE in the 50-60 range, with ABG
the 16801 is a bit higher in the 60-70 range, with NAGB


That is only 10-20% more QE, or... just take 10-20% more subs or exposure time with the ABG camera and you have the same signal to noise ratio (+/-) as with a NABG camera.
Take the ABG camera.

Garrett van der Veen

#3 Konihlav

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Posted 08 July 2014 - 09:48 AM

prefetch: which CCD camera you think of in terms of 16801 chip? this one:
http://telescopes.ne...1e-grade-1.html
?

#4 jrcrilly

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Posted 08 July 2014 - 10:25 AM

I may not be typical, but I always shoot as much time as I have budgeted for an image. NABG gets me more/better data in the same time so it's a positive for me, especially when using narrowband filters. The only reason I'm using ABG now is that I wanted a larger chip than my ST-10 but didn't want to pay for a 6303.

#5 blueman

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Posted 08 July 2014 - 12:00 PM

I don't like dealing with blooming. Yes there are programs that can remove them, more or less. But if the bloom goes through an object of a field of stars, well it can remove the bloom but can not replace the data behind them.
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#6 Jared

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Posted 08 July 2014 - 12:39 PM

I've never bought the argument that you can just increase your integration time to cover the loss in sensitivity. Almost all of us can benefit from increased integration time on almost all of our images--that applies equally to ABG and NABG cameras.

The real question is whether the increased sensitivity is worth the pain of dealing with blooms. For most people the answer is no. Blooms are not much of an issue if you are going after galaxies and planetary nebulae, but they can be a real hassle for emission nebulae, open clusters, etc.. I took an image of the Elephant's trunk on Friday night, for example, and ended up spending about an hour cleaning up the blooms. The automatic routines do an OK job, but they don't really stack up to manual corrections if you are stretching hard at all.

For me the choice was actually pretty easy. I wanted to measure transits for extra solar planets, and having a perfectly linear CCD was a big plus. That meant NABG. I ended up with a 6303 based camera and have been very happy. The additional QE is a bonus. Since I would otherwise have been looking at an 11002 based camera, the jump in QE was a lot more than 10%, also. I just don't mind dealing with the blooms. Others hate it.

Oh, I should mention that while a NABG camera is very helpful for photometry/extra solar planet transits, it isn't strictly necessary. It is possible to determine the linear range on any given camera and stick to exposure durations that leave target stars in that range. You just get a wider range with an NABG camera.

I don't know whether your "freaking out" over blooming is justified or not. I can fix a typical bloom in Photoshop in, say, 30 seconds or so. If it's in the middle of a really dense star field where, for example, a diffraction spike/bloom is overlapping a background star that 30s may go to a minute. If you have six/eight/ten blooms in an image this is a pretty small penalty for the increased sensitivity. If you have 100?

I'd recommend looking taking a hard look at your favorite types of targets. Do you do much wide field imaging? Lots of emission nebulae and star clusters? I'd probably stick with the ABG camera. If you hate post processing and Photoshop, then the ABG is the way to go. Interested more in galaxies, planetary nebulae, and smaller objects? Longer focal length imaging--particularly at f/7 and above? Take the extra QE of the NABG camera. If you think that photometry is in your future, I'd also stick with the NABG camera.

#7 jrcrilly

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Posted 08 July 2014 - 01:30 PM

The additional QE is a bonus. Since I would otherwise have been looking at an 11002 based camera, the jump in QE was a lot more than 10%, also.


Yup. I went from a full frame NABG ST-10 to an interline ABG STL-11000 and the difference was substantial. Too much wasted surface. After a few months I went back to an ST-10 (would have MUCH preferred the 6303!).

#8 woodworkt

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Posted 08 July 2014 - 05:09 PM

I recall looking at this a year or so ago. There have been enough advances in chips that the sensitivity of the ABG 16803 is reasonably comparable to the NABG 6303.

That might not have been enough to sway me, all by itself. But, the fact that you have to pay an obscene ~$15,000 extra for the privilege of getting the NABG version of the same chip did. Even if that amount were in the realm of consideration, I personally would rather put it into larger/faster optics to make up the difference instead. Or perhaps, a permanent roll-off-roof observatory shed to provide more nights on which to collect photons.

Just my two cents, of course...

#9 Jared

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Posted 08 July 2014 - 05:51 PM

Yeah, if I were looking at a really large chip camera there is no question the 16803 would be at the top of my list--probably the only item on the list. It's less clear cut, though, if you are comparing a 6303 to an 11002 or a 16803 to a 16801. For most people, though, the ABG camera will be the better fit.

I'd still recommend the original poster look at what the typical imaging targets will be. Narrow field? The advantages of ABG may be worth the extra hassle. Wider fields or clusters? No question NABG is the way to go.

#10 WadeH237

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Posted 08 July 2014 - 07:14 PM

...Narrow field? The advantages of ABG may be worth the extra hassle. Wider fields or clusters? No question NABG is the way to go.


Did you reverse these? I would be fine with NABG on narrow fields, but prefer ABG on wide fields.

The acronyms are a bit strange to read at a glance because NABG is a double negative (Non-Anti Blooming Gate).

#11 Jared

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Posted 09 July 2014 - 12:15 AM

Yes, I said it backwards. Wide fields are generally a better match to ABG cameras and narrow fields to NABG cameras. Thanks for the correction.

Obviously, with wider fields you are likely to have more foreground stars and therefor more blooms, hence the preference for ABG.

#12 prefetch

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Posted 09 July 2014 - 12:23 AM

i appreciate everyone's input. still not exactly sure what i'm going to do. i gotta do some price checking to, because the only 16801 i've found an online price for is $29k, and i should factor that in to my decision, since that's sort of a lot of money. not sure why it costs so much more than an 16803 - i suppose it has something to do with volume perhaps?

anyway, thanks again for the food for thought. very much appreciated.

#13 blueman

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Posted 09 July 2014 - 12:25 AM

The cost of efficiency can be very high.
Blueman

i appreciate everyone's input. still not exactly sure what i'm going to do. i gotta do some price checking to, because the only 16801 i've found an online price for is $29k, and i should factor that in to my decision, since that's sort of a lot of money. not sure why it costs so much more than an 16803 - i suppose it has something to do with volume perhaps?

anyway, thanks again for the food for thought. very much appreciated.



#14 Konihlav

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Posted 09 July 2014 - 01:34 AM

prefetch: you are welcome. The price point is the reason why I asked you that question.

Anyway, at the moment, if one wants a really big chip (which is a great thing) then the only reasonable (counting price tag) option is the widespread KAF-16803. The "only" downside of big chips is that you need a high quality optics to make a full use of it.

#15 prefetch

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Posted 09 July 2014 - 01:40 PM

>The "only" downside of big chips is that you need a high quality optics to make a full use of it.

this makes me think about the large image circle size as well as the corresponding corrected optics to fully take advantage of the size.

are these the two primary considerations?

#16 blueman

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Posted 09 July 2014 - 01:58 PM

Of course, not to mention the size of the subs at 32 megs each from the camera. This means you need a nice computer to work with a lot of data.
The image circle needs to be large to fully cover the chip. This is found with most scopes made for astrophoto used though.
The weight and cost of the camera with the cost of the associated filters is also a big consideration. Have you priced the 50mm square filters? :shocked:
Blueman

>The "only" downside of big chips is that you need a high quality optics to make a full use of it.

this makes me think about the large image circle size as well as the corresponding corrected optics to fully take advantage of the size.

are these the two primary considerations?



#17 Konihlav

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Posted 09 July 2014 - 05:26 PM

the price of big 50mm square filters (I use only Astrodons as the one and only best and only everytime everywhere) was a reason for me to get 36x24mm chip instead of 36x36mm (as well as I do not like square format and it is problematic for an OAG to get good star definition at the edge of the image circle and good signal as there is always increasing vignetting at the corners). Latest issue of a friend of mine with 36x36mm chip and 3" focuser and 3" corrector giving 50mm image circle is that this combination has 50% of vignetting at the corners so he has to crop significantly... therefore in case you go with 36x36mm chip like reasonable KAF-16803 then do really take this into account. If you want big aperture scope (which is good decision as well as the big size chip) then it would probably be a reflector and that one is *best* guided with an OAG. Do get 4" corrector in such a case!

as you can see nothing is simple here :) I've been "investigating" CCD cameras and market for last 5 years, but now I do not care any more, I found what I was looking for and am waiting for a new stuff to come hope within a year or so and then maybe I make some leap forward. Until then I stick with two CCD cameras one with tiny but beautiful Sony ICX694 chip and one with very big but very ugly bug giving great results except of narrow band with KAI-11002 (price point of view).

:) good luck ;)

#18 Konihlav

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Posted 09 July 2014 - 05:31 PM

another rule of thumb that I figured out:

the price of the CCD camera is kinda equal (proportional) to price of the Astrograph which is equal to the price of the reasonable quality mount to drive that scope :) but here I am off topic now...






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