Black Clipping in Nikon D7000 Dark

[Carole]

In terms of overall noise reduction it is very slightly better to shoot the R,G & B through separate filters with 2x2 on chip binning

I agree but needs must with so little clear skies.  
So 2 x 2 binning is better for noise Mark?  

I tried binning once but found it too much faff with having to do separate calibration files and then re-sizing for combining with Luminance.  Not had a chance to use NB or LRGB since.

[MarkS]

In terms of overall noise reduction it is very slightly better to shoot the R,G & B through separate filters with 2x2 on chip binning

I agree but needs must with so little clear skies.  
So 2 x 2 binning is better for noise Mark?  

Actually, there is only one good reason for using 2x2 hardware binning - do it when the the read noise is the dominant source of noise.  If you shoot normally (i.e. without binning), then you always have the flexibility of performing a Gaussian blur on the R,G,B layers during processing, if that's what you wish to do.

Mark

[MarkS]

I've been oscillating over this Nikon D7000 for a while now but I've finally come to the conclusion that it's really not going to suit my purposes i.e. stacked exposure astrophotography.  It's a shame because I really wanted to like this camera.  The sensor is noticeably superior to the entry level Canons, having higher QE, very low read noise across the ISO range and much lower dark current.

So I'm going to get a Canon 550D (they're going very cheap now) which I'll mod for H-alpha and almost certainly later I'll do a Peltier cooling mod to deal with the dark current.

Mark

[Carole]

What will be the advantage of this Mark, a better sensor?

Also are you aware they are selling already modified and peltier cooled DSLRs, but they are not cheap?
http://www.centralds.net/en/index.htm

Carole

[MarkS]

The 550D is a better sensor than my present 350D and will give me plenty of megapixels to play with.

Its sensor is not as good as the Nikon D7000 but the Canon doesn't clip the pixels in dark frames or in light frames that are very dark (e.g. narrowband or very slow F-ratios).

Actually, that CDS-600D on the Centralds site is very tempting:
http://www.centralds.net/cam/?product=cds-600dx-cooled-eos-600d-2

USD $1000 for this "Frankenstein" conversion or USD $1800 brand new (with Baader filter) is not an unreasonable price compared with dedicated OSC astro-cameras.  The "Frankenstein" conversion is very similar in appearance to Julian's !

What makes me really laugh is that they charge extra to fit a "lens adaptor" i.e. the ability to use a standard Canon lens!
The downside is that they are removing a lot of what make it a real camera (look at the list of things removed).

Mark

[Carole]

Yes I guess it's really intended for astro use.  I know some-one who has bought one, but like us is besieged by clouds so hasn't had a chance to try it out yet. 

Carole

[MarkS]

I know some-one who has bought one

What, a CDS-600D ?

[Carole]

One of the Cooled and modded DSLRs not sure which model, do you want me to ask?

She hasn't had a chance to use it yet due to cloud same as us, but lives in Herne Bay, so if you wanted to take a look I am sure she would be obliging.

Carole

[MarkS]

My Canon 550D arrived today so I'll shortly put it through the usual batch of tests before I pull it to bits to mod it and to investigate how to add a cold finger.

I've also got a Starlight Xpress SXVF-M25C to test.  I won't be pulling that one to bits though!

BTW - someone on the Cloudy Nights forum sent me some Pentax raws from the K-01 which uses the same IMX071 sensor as the Nikon D7000.  The Pentax is clipping pixels to zero in a very similar way to the Nikon. 

So it really does appear that Canons are the only mainstream DSLRs that are suitable for long exposure stacked astrophotography.

Mark

[Rocket Pooch]

QED?

[MarkS]

QED?

No - the exact opposite in fact. 

I set out to prove that Nikons had got an edge over the Canons by using superior sensor technology and that it was about time we seriously considered using them for astrophotography.  I really didn't expect to discover the "clipping to zero" problem.  So I'm forced to conclude that the Canons are still overall the best choice for entry level DSLRs - at least for stacked astrophotography.

But for single long exposures and for making astro-videos the low noise of the Nikon sensor definitely gives it the edge.