CCD or Sony a7s?

[vertigo262]

I do narrowband imaging with both the A7R and A7S, and previously with my Canon 60D.  One does not require a mono CCD to mount narrowband filters and capture subs.  A full spectrum camera "sees" the same spectrum width as a mono camera, it is simply split by the Bayer filter to three channels.  It is really not much different than using a mono camera or shooting IR with a modified DSLR/mirrorless camera.

The 1st nine images in Sony A7S & AT8RC - 2014Oct30+ were shot with a Baader Ha filter on Astro-Tech 8" RC using an A7S.  They are not the best of results due to cloud moving into the area later in the evening.

oh, I was told it had to be mono, to get any results. I tried some tests with an ha and my canon 7d, didn't seem right to me. and everyone told me that was wrong. So anyways. that one I am kind of confused on. I was asking if I could turn the firmware on to monochrome and then use the ha filter. but was told that would not work

[AnakChan]

oh, I was told it had to be mono, to get any results. I tried some tests with an ha and my canon 7d, didn't seem right to me. and everyone told me that was wrong. So anyways. that one I am kind of confused on. I was asking if I could turn the firmware on to monochrome and then use the ha filter. but was told that would not work

As far as I know, if one wants to convert their DSLR sensor into mono, it's a physical/manual work that involves not only removing the filters on the sensor but to then lightly sand off the Bayer filter from the sensor to expose the sensor array (which is mono).

Google up sensor Bayer filter removal & you'll see some DIY instructions around. Not to be done lightly (unless you're prepared to test & destroy a couple of sensors).

[giorgio_ne]

Before getting a QSI ccd I was seriously considering the A7S until I've learned it cooks its RAW files. a Google search would return many stories about this. After having owned a Nikon D70s, famous in the astrophotography circles for its star eating processing engine, I would never compromise on post processing limitations imposed by cooked raw files.

[vertigo262]

how do they taste? )

[Zakalwe]

The Misty Valley Ranch is about 150 km from the nearest serious source of light pollution so I'm relatively lucky that way.  I wouldn't want to try imaging from the center of Tokyo or any other major city !

bwa

I think that the important point is in bold.  Under dark skies, with a fast scope, a DSLR will sing. Something like an A7 will really shine....look at Fritz Hemmereich's work.  He is using a 14" Hyperstar (f2) and is operating at 1200m in Tenerife.

For someone like me, operating at sea-level, with rubbish weather and bad atmospheric conditions, then a DSLR would be, and is an awful choice.

[kalasinman]

I think that the important point is in bold.  Under dark skies, with a fast scope, a DSLR will sing. Something like an A7 will really shine....look at Fritz Hemmereich's work.  He is using a 14" Hyperstar (f2) and is operating at 1200m in Tenerife.

For someone like me, operating at sea-level, with rubbish weather and bad atmospheric conditions, then a DSLR would be, and is an awful choice.

Technically, can't argue with that. For those of us trying to start with a total kit of less cost than an A7s, it makes perfect sense.

[bwana]

oh, I was told it had to be mono, to get any results. I tried some tests with an ha and my canon 7d, didn't seem right to me. and everyone told me that was wrong. So anyways. that one I am kind of confused on. I was asking if I could turn the firmware on to monochrome and then use the ha filter. but was told that would not work

Whoever told you this was wrong...

bwa

[bwana]

As far as I know, if one wants to convert their DSLR sensor into mono, it's a physical/manual work that involves not only removing the filters on the sensor but to then lightly sand off the Bayer filter from the sensor to expose the sensor array (which is mono).

Google up sensor Bayer filter removal & you'll see some DIY instructions around. Not to be done lightly (unless you're prepared to test & destroy a couple of sensors).

There are people/companies that do this commercially, at least for Canon and Nikon cameras.  Not sure about Sony?

[bwana]

Before getting a QSI ccd I was seriously considering the A7S until I've learned it cooks its RAW files. a Google search would return many stories about this. After having owned a Nikon D70s, famous in the astrophotography circles for its star eating processing engine, I would never compromise on post processing limitations imposed by cooked raw files.

All the Sony A7 cameras have proprietary RAW compression; known fact.  I've read a lot of articles on the "problem" and even tried to duplicate the problem, without success.  It is supposedly quite obvious around the edges of high contrast regions.  In astrophotography that should be on the edge of stars.  I pulled a 100% crop from a Star Trails image I had shot with the A7R.  The problem may exist but I haven't seen it.

bwa 

[bwana]

I think that the important point is in bold.  Under dark skies, with a fast scope, a DSLR will sing. Something like an A7 will really shine....look at Fritz Hemmereich's work.  He is using a 14" Hyperstar (f2) and is operating at 1200m in Tenerife.

For someone like me, operating at sea-level, with rubbish weather and bad atmospheric conditions, then a DSLR would be, and is an awful choice.

I really like the last paragraph of Fritz's interview:

"I could directly compare a cooled Canon 5DMarkIII and a cooled Sony A7s, both of CentralDS: I can not really compare them. These are two worlds. With a huge distance between them. Although the specifications of DxO didnt show a significant difference in the pure measures, in the practice of everyday life it differs between effort (Canon) and joy (Sony)."

Why would you consider a DSLR to be worse than any other camera at sea-level, with rubbish weather and bad atmospheric conditions?  I can't see a QSI or any camera, for that matter, functioning very well under those conditions.  The reason I like a good fast DLSR/mirrorless camera is that I can shoot relatively short imaging session between bouts of bad weather and/or cloud cover.  Shooting narrowband and/or using CCD's did allow me that luxury.

[bwana]

...Shooting narrowband and/or using CCD's did allow me that luxury.

Should have been "Shooting narrowband and/or using CCD's did not allow me that luxury."  Freudian slip?

bwa

[wuthton]

Should have been "Shooting narrowband and/or using CCD's did not allow me that luxury." Freudian slip?

bwa

Err... Mono/Narrowband cuts through LP like a hot knife through butter.

These days I would not consider using a OSC camera under even the slightest level of LP.

Actually data acquisition is quicker in mono so I'd stick with mono under dark skies too.

[Zakalwe]

I really like the last paragraph of Fritz's interview:

"I could directly compare a cooled Canon 5DMarkIII and a cooled Sony A7s, both of CentralDS: I can not really compare them. These are two worlds. With a huge distance between them. Although the specifications of DxO didnt show a significant difference in the pure measures, in the practice of everyday life it differs between effort (Canon) and joy (Sony)."

Why would you consider a DSLR to be worse than any other camera at sea-level, with rubbish weather and bad atmospheric conditions?  I can't see a QSI or any camera, for that matter, functioning very well under those conditions.  The reason I like a good fast DLSR/mirrorless camera is that I can shoot relatively short imaging session between bouts of bad weather and/or cloud cover.  Shooting narrowband and/or using CCD's did allow me that luxury.

A couple of reasons. DSLRs work well with fast scopes. A fast scope in my conditions (lots of moisture in the air and moderate LP) will quickly become sky-fog limited.

Err... Mono/Narrowband cuts through LP like a hot knife through butter.

These days I would not consider using a OSC camera under even the slightest level of LP.

Secondly, this ^^. Plus, it only seems to be clear nowadays when there is a full Moon. That means H-a time!

[sharkmelley]

I think it is likely that the Sony A7S is the best DSLR/Mirrorless camera out there in terms of astro-image quality.  Its high Quantum Efficiency full-frame sensor with large pixels means it mops up photons.  It has extremely low read noise - dropping to less than 1e which make the necessity for long exposures a thing of the past, possibly opening the way for unguided imaging.

I would like to see figures for its QE at the H-alpha wavelength and for its dark current after say 2 hours of solid imaging but it's more or less impossible to get such information for any DSLR.  This would give some insight into its optimum operating conditions i.e. scope speed required and ideal upper limit for night time operating temperature.

The main negative is that the Sony lacks astro-software support at the present time.   Obviously if you might want to do narrowband imaging then a cooled mono CCD is the way to go instead.

Mark

[bwana]

A couple of reasons. DSLRs work well with fast scopes. A fast scope in my conditions (lots of moisture in the air and moderate LP) will quickly become sky-fog limited.

Secondly, this ^^. Plus, it only seems to be clear nowadays when there is a full Moon. That means H-a time!

Everyone seems to forget that a DSLR/mirrorless camera like the A7S works quite well with narrowband filters and scopes in the f/6 to f/10 range.  Narrowband filters are not (somehow) limited to mono CCD's!!

[bwana]

I think it is likely that the Sony A7S is the best DSLR/Mirrorless camera out there in terms of astro-image quality.  Its high Quantum Efficiency full-frame sensor with large pixels means it mops up photons.  It has extremely low read noise - dropping to less than 1e which make the necessity for long exposures a thing of the past, possibly opening the way for unguided imaging.

I would like to see figures for its QE at the H-alpha wavelength and for its dark current after say 2 hours of solid imaging but it's more or less impossible to get such information for any DSLR.  This would give some insight into its optimum operating conditions i.e. scope speed required and ideal upper limit for night time operating temperature.

The main negative is that the Sony lacks astro-software support at the present time.   Obviously if you might want to do narrowband imaging then a cooled mono CCD is the way to go instead.

Mark

Since I don't use astro software for image capture I don't view this as a problem; however, I do realize a lot of people can't do astrophotography without a computer.  I'm not sure why?  It is so much easier without the added hassle.

As for guiding, I haven't used guiding since I acquired the A7R back in Nov. 2014 and even require it less with the A7S.   Even if I did require guiding I can use my standalone LaCerta MGEN and still not have to use a computer...

I do like my mono ATIK 428Ex for narrowband imaging but it does mean I have to use a computer and fire up guiding because I'm shooting much longer subs.  I much prefer to use the A7S in place of the ATIK 428Ex and do my narrowband imaging with it; much easier.  I'm not sure why people think it is necessary to use a mono CCD when narrowband imaging.  Maybe it is a holdover mindset from the days of B&W film or something?  It's not as if narrowband wavelengths won't penetrate a Bayer filter.

bwa

[sharkmelley]

I'm not sure why people think it is necessary to use a mono CCD when narrowband imaging.  Maybe it is a holdover mindset from the days of B&W film or something?  It's not as if narrowband wavelengths won't penetrate a Bayer filter.

There are a number of reasons why cooled mono outperforms a typical modded DSLR for narrowband:

1)  For H-alpha, the DSLR Bayer matrix means that only the Red pixels pick up any signal whereas all pixels of a mono camera are responsive.  So, like for like, a mono camera picks up 4x as much data. Analogous arguments apply to the other narrowband wavelengths.

2)  Using NB filters, there is very little background sky signal.  This means that the DSLR thermal noise is the main source of image noise especially on warm summer nights. A cooled CCD does not have this constraint.

However, those arguments only really apply when you are comparing similar size sensors.  When comparing the massive full frame sensor of the A7S against the tiny ATIK 428EX sensor, the photon collecting ability of the full-frame sensor is a massive win.

Mark

[vertigo262]

Whoever told you this was wrong...

bwa

I went out trying to get ha with my 7D, in several posts on multiple topics I was told taking ha with a rgb wouldn't work. so now I have no clue if it will or wont

[sharkmelley]

I went out trying to get ha with my 7D, in several posts on multiple topics I was told taking ha with a rgb wouldn't work. so now I have no clue if it will or wont

If your 7D is unmodified then it will be relatively insensitive to H-alpha because the internal filter will be cutting out 80% of the H-alpha light.  Even so,  you might be pleasantly surprised with what is achievable.

[vertigo262]

it's full spectrum, but what confused me and what was told was that I was getting rgb with ha is mixing channels. I was removing the red channel. although it didn't look that great. I'm not sure if I was doing it right. but I guess at that point, I was told it should be done in mono and it's pointless to do narrowband with an rgb or osc camera

[vertigo262]

also, this was another thing I asked in another topic was about turning my firmware on the camera to mono, then trying ha, was told that would cause problems as well.

[sharkmelley]

If all you want is the H-alpha and you are using a narrowband filter then removing the red channel is exactly what you want to do.  However, I think it is generally preferable to use a DSLR for what it does best i.e. taking full colour images.

Having said that, it is certainly possible to do NB imaging with a DSLR. I have seen some good examples.    However, this works best with fairly fast optics and cool night time temperatures because of the limitations of DSLR cameras.  I certainly wouldn't describe it as pointless.

Mark

[ollypenrice]

Let me ask it another way. If for example astro magazine came to you (name made up of course), and said. We want you to take a picture of this nebula for the cover of our magazine, would you use a mono ccd and narrowband, or the a7s?

Without any doubt whatever I would use a monochrome CCD whether it was for natural colour, colour enhanced by Ha or possibly O111 or full narrowband.

Regarding the Atik 11000 I have lots of images using that camera. Some examples...

http://ollypenrice.smugmug.com/Other/Best-of-Les-Granges/i-SHnPvp3/0/O/M33%203SCOPE%2030HR%20HaLRGB%20ODK%20CoreV2..jpg

http://ollypenrice.smugmug.com/Other/Best-of-Les-Granges/i-3bjPNHd/0/X3/Mopdified%20Straton%20FIN%20web-X3.jpg

http://ollypenrice.smugmug.com/Other/Best-of-Les-Granges/i-ZBmVMGT/0/X3/M45%20final-X3.jpg

I must say, though, that DSLRs are getting better. It is absolutely vital, when comparing images, to note the F ratio of the instrument. In very fast scopes DSLRs do well. Down at F7, as in this example, I don't know how well they'd do.

Small   http://ollypenrice.smugmug.com/Other/Best-of-Les-Granges/i-XqpRhfL/0/X3/SAG%20TRIPLET%20TEC%20MOSAIC-X3.jpg

Full  (large file) http://ollypenrice.smugmug.com/Other/Best-of-Les-Granges/i-XqpRhfL/0/O/SAG%20TRIPLET%20TEC%20MOSAIC.jpg

Olly

[ollypenrice]

oh, I was told it had to be mono, to get any results. I tried some tests with an ha and my canon 7d, didn't seem right to me. and everyone told me that was wrong. So anyways. that one I am kind of confused on. I was asking if I could turn the firmware on to monochrome and then use the ha filter. but was told that would not work

Whoever told you this was wrong...

 

bwa

 

No, I'm sorry but  they were right - in this sense: turning the camera onto to mono does not make it a mono camera because it does not remove the Bayer Matrix. The Ha filter, in whatever mode you run the camera, will be blind to three quarters of the pixels - namely those under the blue and green filters. While it is still possble and worthwhile to use an Ha filter under a Bayer Matrix nothing is going to alter fact that it is a highly inefficient thing to do since you lose vast amounts of signal and resolution.

 

A monochrome camera is a camera which records all the colours all of the time. This is never possible under a Bayer Matrix.

 

Olly

[Xplode]

I went out trying to get ha with my 7D, in several posts on multiple topics I was told taking ha with a rgb wouldn't work. so now I have no clue if it will or wont

Here's your answer:

10x600s taken with 6Da through my TS 100Q and Baader 7nm Ha filter.

Split into separate colors after stacking, green and blue channel have been discarded so this is just the red channel.