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to fill in the small gap. Several are avail-

able online and work well.

The IMX 455 CMOS chip is the first

to capture data in true 16 bits. Most cam-

eras use chips that capture data in 14 bits

and interpolate up to 16 bits. True 16-bit

data has an incredible number of tonal

values so stretching can be performed

without the image falling apart. By cap-

turing in 16 bits, you have the full range

of 65535 density levels, which allows you

to pull out more detail during process-

ing. If you’re simply stretching 8-bit data,

it doesn’t look good because of the lim-

ited number of tonal values.

The QHY 600 is available in both

mono and color versions, and in a variety

of configurations depending on how you

plan to use the camera. I spoke at length

about shooting color versus mono in my

review of the QHY 410C color camera,

which appeared in the February issue.

To sum it up, traditionalists like myself

prefer shooting mono with separate fil-

ters for the RGB and narrow bands.

It does get a bit more complicated,

however. A color camera records all

colors simultaneously utilizing a Bayer

matrix. This makes creating colored

images a lot easier and can be an advan-

tage for imaging certain objects, like

comets. If you are used to working with

a mono CCD camera, the switch to a

CMOS mono camera should not be

difficult.

The one difference that I have found

between the two is that because CMOS

has such low noise, you only need RGB

exposures to create an image, with no

luminance exposure required. If you feel

you do need a luminance, you can fabri-

cate one by averaging all the color data.

Due to the large size of the files and

the fast download

speeds, QHYCCD built

in a 2-gigabyte DDR3

image buffer to smooth

data transfer to the host

computer. The data

from the QHY 600, in

addition to its real 16-bit depth, are also

true raw data, meaning the recorded

data have undergone no adjustments,

such as noise suppression or hot pixel

removal. It is the original signal, which

can be processed and manipulated as the

situation necessitates. The camera has

one other great feature: There’s zero

amplifier glow even with extended expo-

sure times.

Dew, condensation, and ref lections

have always been problems with digital

cameras. The QHY 600 addresses them

with a desiccant plug for the hermetically

sealed CMOS chamber, high-end anti-

ref lective coatings on all glass surfaces,

and a heater to keep external windows

moisture-free. The sensor is cooled by a

regulated two-stage thermocouple device

to maintain a constant temperature.

Creating images

I try to keep my processing as simple

as possible, yet I sacrifice nothing in

producing the final results. I use MaxIm

DL for my initial processing: the creation

of master darks, f lats, and bias frames. I

also use it to reduce and combine all my

data files. I find that the sigma combine

function works great to maintain as

much information as possible and still

remove outliers like hot pixels. Be careful

with these. Some hot pixels change value

so that the dark frame does not remove

them completely. You need outlier rejec-

tion and at least five frames to affect

their removal.

After creating the master files, I save

them as a 16-bit TIFF file. I then import

it into Photoshop, stretching it with

curves or levels to bring out all the detail.

CMOS data have such low noise that cer-

tain plug-ins work wonders. These typi-

cally are Luminar, Topaz II, and the real

secret weapon, the sharplet filter in the

Redfield suite. There are numerous star

reduction methods, which include Russ

Croman’s Star Shrink and the minimum

filter in Photoshop. In all cases, I use

these powerful tools with the stars

selected and feathered.

Large stars can be reduced using the

liquefy filter and choosing the pucker

tool. If it sounds like there are a lot of

tricks to make striking images, you’re

right. But the challenge can be part of

the fun.

If noise does show up in your image,

it’s usually in the shadows. Make a dupli-

cate layer, generously apply the noise

The optional filter

holder is seen here,

attached to the

QHY 600. QHYCCD

PRODUCT

INFORMATION

QHY600PH

Sensor: Sony IMX455 back-illuminated

Sensor size: 36mm x 24mm (full frame)

Image buffer: 2 gigabytes

Pixel size: 3.76x3.76 micrometers

Effective pixel area: 9576x6388

Output: 16-bit with 65535 levels

Exposure range: 40ms to 3600s

Computer interface: USB 3.0

Weight: 30 ounces (850 grams)

Dimensions: 5.2 x 3.5 inches

(131.8mm x 90mm)

Price: $4,599