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Old 08-11-2015, 10:54 AM
brisen (Brian)
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Mid level CCD for C11 Edge HD

I am looking to increase my use of a C11 Edge HD and always intended moving towards astrophotography at some point. I would like opinions on what would be a good mid range CCD for use with an 11" Edge HD. I still have to get a guide scope to go with it and any advice on this would also be greatly appreciated.

I have been looking at the Atik mono range. I have the colour filters already and now looking to get the other bits and pieces progressively over the coming months.

Brian
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Old 08-11-2015, 11:24 AM
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Hi Brian,

It's great to hear you would like to get into astrophotography, and I am assuming not planetary imaging, but DSOs.

Your telescope has 2800mm focal length - so camera will need to have large pixels, and that usually means expensive cameras. Also, at that focal length you will need a VERY good mount.

To make things easier, you could reduce significantly focal length of your telescope with a good 0.5-0.6 reducer. Additionally binning pixels 2x2 could help.

With your telescope I would probably stay away from guide scopes and get an OAG instead.

When selecting the right camera for DSO imaging, aim first for about 2 arcseconds per pixel, in particular when getting started with astrophotography, and then look at cameras that will allow for such resolution.

I hope it helps a bit.
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Old 08-11-2015, 11:34 AM
brisen (Brian)
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Hi Slawomir

Thanks, yes that does help. I was referring to DSOs as opposed to planetary imaging.

Brian
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Old 08-11-2015, 05:18 PM
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agree with S. you need very big pixels at such a long fl.

Suggest that you get a 6.3 reducer (providing these work with the edge) and use an 8300 chipped camera with 2x2 binning. The 8300 does not do binning quite as well as some others, but such a setup would provide 10.8 micron effective pixels and at least allow you to use your existing scope with high resolution and reasonable sensitivity. The 8300 would then be suitable for a shorter scope when you decide to look at wider fields. Forget the Sony chips for now - their pixels are a bit too small for your focal length.

OAG would be the best way to guide - you should have plenty of back focus to fit one in. again, you will need big pixels and an SX lodestar might be best.

Last edited by Shiraz; 08-11-2015 at 05:49 PM.
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Old 08-11-2015, 06:00 PM
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I was also thinking that Atik 383L (or similar) is a very good value for money.

Another option would be to get a hyperstar, which I believe reduces FL to 560mm. Acquiring focus at f/2 would be a true PITA though, but at the same time you could pick from a wider range of suitable cameras (I think Atik 460 would be very good) and a real bonus with hyperstar is short integration time at f/2.
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Old 08-11-2015, 09:12 PM
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Binning a Sony 694 gives 9 micron pixels which is ideal at 2800mm focal length.

That ideal pixel/arc sec is 1 arc second not 2 arc seconds per pixel which is really slightly oversampling. Nyquist theorem says at least 2x sampling for an efficient sample. Stan Moore suggests .5 to 1.5 arc seconds per pixel. Short focal length scopes are often imaged at 3 arc seconds or more.
A 3X sampling seems to be close to ideal and when you consider most experience seeing around 3 to 3.5 arc seconds a 3X sample is simply 3 divided by 3 = 1 arc second per pixel.

1x1 binning will work on the smaller Sony chip at 2800. I have done 3 metres. It worked better than 8300 did at that focal length because its so clean and sensitive. Its a full 30% more sensitive than the 8300 and even more when binned 2x2. The main advantage of the 8300 is the wider field of view and slightly larger well depth.

Not only is the chip cleaner, it bins properly compared to the 8300. Its more sensitive to start with so a binned 694 would cut exposure time significantly over a binned 8300 sensor.

Also the 694 being smaller is less likely to have coma in the FOV from the fairly low quality Meade or Celestron reducer. I would not be surprised if the 8300 does not correct fully with that reducer but others would know for sure.

But if you are new to astrophotography trying to image at 2800mm focal length as your first imaging setup is likely to cause you grief as an SCT has mirror flop, the focuser is a bit sloppy, your mount unless very high end is going to lack accurate enough tracking and your autoguiding solution is not likely to be ideal. The usual advice is to start with short focal length refractors in which case the 8300 or 694 are both great sensors to use and guide scopes work. Guide scopes tend not to work at 2800mm unless for quite short exposures. Off axis guiders become vital above about 800mm focal length.

At the end of the day you will get excellent results from both the Sony 694 and the Kodak 8300 sensors. The 8300 tends to be the more popular sensor as it is also a bit cheaper and a larger field of view (about 50% more than the Sony 694), is quite sensitive with reasonably low read noise.

The Sony 694 on the other hand is much cleaner, about 30% more sensitive, even more when binned, 4.54 micron pixels binned 2 x 2 gives you 9 microns which seems about perfect for longer focal lengths but it will be even more challenging for tracking as the smaller sized sensor gives you a zoom effect so objects will appear larger on the Sony sensor than the 8300 sensor. This is good for galaxies and perhaps worse for larger nebula images.

Greg.

Last edited by gregbradley; 08-11-2015 at 09:22 PM.
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Old 08-11-2015, 09:13 PM
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The C11 Edge HD is a great, versatile scope for AP , Brian. As Ray and Slaw have mentioned, a reducer of some type would be the way to go.

For long FL the edge needs the x.7 reducer Click here this produces a FL of 1960mm F7 and cuts the integration time in half from the F10 ratio. You'll have 146mm of back focus so there's plenty of room for an OAG.

The Hyperstar lens will reduce the FL to 560mm and is super fast at F2 . Exposures of 30 sec to 90 sec are all you'd need to great SNR. A short guide scope like the Orion mini scope is perfect with this configuration.

SX Lodestar or equivalent is essential for F7 OAG guiding.

As for the camera, I haven't moved the CCD yet. I've only used the Canon 60Da with 4.3 pixels in both configurations. This gives an image scale of 0.45 arcsec/pixel at 1960mm (over sampled but results have been good) and 1.58 arcsec/pixel at 560mm (under sampled but drizzle in Pixinsight helps with this)

My Astrobin gallery has images taken with both set ups. Click here

For CCD, the Kodak 8300 for F7 would be good (for FOV) or if you only go the hyperstar path the SX 814 would be a great CCD at 560mm

Last edited by Rod771; 08-11-2015 at 09:27 PM.
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Old 08-11-2015, 10:33 PM
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I used a C-11 for many years on a Losmandy HGM100 and later a G-11.

I had no problems getting perfectly round stars...though... I was using a self guiding CCD camera (and still do )

C-11's are a great 'scope and the Edge versions should have better "edge" correction....but at around 3 metres focal length I'd also suggest you will need to use an OAG, plus have either a quality mount or something well tamed at least.
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Old 08-11-2015, 10:57 PM
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Quote:
Originally Posted by gregbradley View Post
a Sony 694 ....is a full 30% more sensitive than the 8300 ......

Greg.
Well....

I'd disagree. Sony don't publish absolute QE data, and it seems derived values vary a tad depending on who's website you want to believe.

So does Christian Buil...

....his testing indicates it's more like 20% at best.

http://www.astrosurf.com/buil/isis/noise/result.htm
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Old 09-11-2015, 07:37 AM
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Quote:
Originally Posted by Peter Ward View Post
Well....

I'd disagree. Sony don't publish absolute QE data, and it seems derived values vary a tad depending on who's website you want to believe.

So does Christian Buil...

....his testing indicates it's more like 20% at best.

http://www.astrosurf.com/buil/isis/noise/result.htm
...
Crikey Peter..... I thought that old myth had been put to bed years ago .

looking at the website you linked to, 66% QE (694) actually provides 50% better sensitivity than 44% QE (8300), which is way more than "like 20% at best". Greg was talking about the system sensitivity gain you get from the higher QE, not a subtraction of absolute quantum efficiencies.

However, the extra pixel size of the 8300 will partially compensate for the lower QE and higher read noise of the 8300 (though not totally from Greg's post) and at 2x2, the bigger pixels are a better match to a 2800mm fl than those of the more expensive Sony CCDs (it is still oversampled though). Agreed that it is far from an optimum solution, but a binned Atik8300, QHY9 or similar camera would be a relatively cost effective way to start imaging with Brian's setup.

Brian, you could also have a look at the 11002 based cameras, but check how big the corrected field is on the edge11. Also be aware that the 11002 has a very low absolute QE and will give you a much less sensitive system than other possible solutions - you will be scratching for sensitivity at f10, even with 9 micron pixels.

Last edited by Shiraz; 09-11-2015 at 10:11 AM.
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Old 09-11-2015, 09:21 AM
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Brian, you could also have a look at the 11002 based cameras, but check how big the corrected field is on the edge11.
42 mm diameter flat image circle.
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Old 09-11-2015, 02:44 PM
brisen (Brian)
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Thanks for all the information from all who replied. It gives me something to work with.

Brian
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Old 09-11-2015, 02:52 PM
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Quote:
Originally Posted by gregbradley View Post
Binning a Sony 694 gives 9 micron pixels which is ideal at 2800mm focal length.
Greg- according to my calculations 9 micron pixels at 2800 mm give 0.66 arc seconds per pixel; might be a little bit challenging in terms of tracking, optical alignment and length of exposures. That's why I suggested about 2 arc seconds per pixel.

Originally Brian mentioned a mid level CCD - 11002 based cameras are probably a little bit higher than mid level

I may be honestly mistaken, but hyperstar option with Atik 460 (clean images and smaller FOV) or Atik 383L (a little noisier images but larger FOV) seems to me as the most cost effective option allowing for fast imaging and potentially good results with some practice.
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Old 09-11-2015, 03:51 PM
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Although not now "cutting edge" I continue to use the ATiK 314L on my C11 (at f11) for spectroscopy.
Using a slit guider (basically on axis guiding) with a Lodestar I can hold the target star indefinitely on a 20 micron slit gap. Guiding using ArtroArt most of the time but PHD2 also works very well.
I use EQMod on my NEQ6pro mount.
HTH
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Old 09-11-2015, 06:46 PM
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Quote:
Originally Posted by Peter Ward View Post
Well....

I'd disagree. Sony don't publish absolute QE data, and it seems derived values vary a tad depending on who's website you want to believe.

So does Christian Buil...

....his testing indicates it's more like 20% at best.

http://www.astrosurf.com/buil/isis/noise/result.htm
I've used both sensors extensively and also notice exposure times on this site. Its at least 30%. That link simply goes to an ad for his publications. I thought he measured DSLRs mainly. I am not sure what equipment you need to measure QE but he is not a professional and I doubt he has the gear to do it with properly.

And its more like 40% - 50% plus more sensitive in narrowband where its even more sensitive in O111 than the venerable 6303 sensor. 66% QE in O111 is unique. 70% in Ha is also unique. You can get a pretty clean 10 minute Ha sub from this sensor. What is the KAF8300's QE in Ha or O111? At a guess 45% and 25% versus 70% and 66%

My experience is the KAF8300 is a very poor match for focal lengths greater than around 2 metres. The Sony is not bad, not quite 9 micron performance but it does allow genuine 2x2 binning which takes it to another level with only a modest drop in resolution. The higher QE and low read noise seems to make up for the mismatch in pixel size and focal length to a large degree.

But there is a reason the KAF8300 is the most popular sensor, its quite versatile and suits your average astrophotographers telescopes and imaging conditions quite well, its got a reasonable FOV without too demanding of the optics so its a good fit for most.


Greg.
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Old 11-11-2015, 10:06 AM
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Quote:
Originally Posted by gregbradley View Post
That link simply goes to an ad for his publications. I thought he measured DSLRs mainly. I am not sure what equipment you need to measure QE but he is not a professional and I doubt he has the gear to do it with properly.

Greg.
Sorry for going off on a tangent Brian, can't let that stand.

Greg, from what I could find, Christian Buil works in a professional capacity for CNES, the French equivalent of NASA - apparently on the design of space-borne electro-optical systems. Researchgate lists 96 of his research publications in the professional literature, so he doesn't just make the coffee.

As an amateur, he has participated in pro/am research on the big scopes at PicduMidi, discovered 5 asteroids (one named after him), lead the team that developed the Audine camera in the late 90s (70%QE, TE cooled), wrote the comprehensive IRIS (image processing) and ISIS (spectra) software packages and has a website full of really good info.

He is indeed a professional who knows in depth what he is talking about - if he says something about electro-optics, it will be right. And what he did not say was that the 694 is only 20% more sensitive than the 8300 as Peter incorrectly claimed - his data clearly show that it is 50% better.

Last edited by Shiraz; 11-11-2015 at 12:39 PM.
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Old 11-11-2015, 12:41 PM
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Quote:
Originally Posted by Shiraz View Post
the 694 is only 20% more sensitive than the 8300 as Peter incorrectly claimed - his data clearly show that it is 50% better.
It comes down to semantics...I was, albeit not very clearly, referring to differences in absolute QE ( that's also why I find relative QE curves to be meaningless)

In the last derived data table on Christian's web page, he comes up with peak QE's 73% for re Sony and 58%. for the KAF. so a difference of....15%....

50% would be impressive! ....over 100% QE

I'll let you check the arithmetic
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Old 11-11-2015, 02:48 PM
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Quote:
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Sorry for going off on a tangent Brian, can't let that stand.

Greg, from what I could find, Christian Buil works in a professional capacity for CNES, the French equivalent of NASA - apparently on the design of space-borne electro-optical systems. Researchgate lists 96 of his research publications in the professional literature, so he doesn't just make the coffee.

As an amateur, he has participated in pro/am research on the big scopes at PicduMidi, discovered 5 asteroids (one named after him), lead the team that developed the Audine camera in the late 90s (70%QE, TE cooled), wrote the comprehensive IRIS (image processing) and ISIS (spectra) software packages and has a website full of really good info.

He is indeed a professional who knows in depth what he is talking about - if he says something about electro-optics, it will be right. And what he did not say was that the 694 is only 20% more sensitive than the 8300 as Peter incorrectly claimed - his data clearly show that it is 50% better.

Thanks Ray. I stand corrected. An increase from 58% to 73% is a 25.9% increase not 15%.

Greg.
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Old 11-11-2015, 06:47 PM
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Quote:
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Thanks Ray. I stand corrected. An increase from 58% to 73% is a 25.9% increase not 15%.

Greg.
OK . 15%. absolute, 26% relative

Too-mate-oh. To-mart-o. Not fussed either way .
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Old 11-11-2015, 07:35 PM
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Brian: There is also a NextGen 0.33X Telecompressor from Optec - it would bring your telescope's focal length to about 900 mm and thus speed it up considerably. There probably would be significant vignetting but this reducer is relatively inexpensive and at that focal length should be a nice match with 8300 chip based camera, such as Atik 383L.
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