Nikon D80 colour bloom

On Thu, 11 Dec 2008 15:16:11 -0000, in rec.photo.digital.slr-systems "Steve" wrote:

We’ve been having some clear moonlit nights here in the UK and I’ve been having a go at some long-exposure night shots. A problem I’ve encountered is colour bloom (heat bloom) in the longer exposures where ‘hot’ components in the camera are interfering with the images causing a light ‘glow’ to appear. The longer the exposure, the worse the bloom.

The Nikon site explains why it occurs but doesn’t seem to give much help in finding a solution other than to "…allow the camera to cool…". This doesn’t seem to do much good. Is there any other way of reducing/removing this bloom, perhaps some sort of subtraction method in post-processing, that I could try?

My D50 suffers a similar problem, although to a much lesser extent. Are the higher-end Nikons (D300, D700 etc) similarly affected or is this bloom something that I’ll have to live with until I get much longer pockets?

See page 83 of the fine manual.

"Steve" wrote in message

We’ve been having some clear moonlit nights here in the UK and I’ve been having a go at some long-exposure night shots. A problem I’ve encountered is colour bloom (heat bloom) in the longer exposures where ‘hot’ components in the camera are interfering with the images causing a light ‘glow’ to appear. The longer the exposure, the worse the bloom.

Have you tried taking multiple short exposures and stacking them in a program such as Registax ?

wrote:

On Thu, 11 Dec 2008 15:16:11 -0000, in rec.photo.digital.slr-systems "Steve" wrote:

We’ve been having some clear moonlit nights here in the UK and I’ve been having a go at some long-exposure night shots. A problem I’ve encountered is colour bloom (heat bloom) in the longer exposures where ‘hot’ components in the camera are interfering with the images causing a light ‘glow’ to appear. The longer the exposure, the worse the bloom.

The Nikon site explains why it occurs but doesn’t seem to give much help in finding a solution other than to "…allow the camera to cool…". This doesn’t seem to do much good. Is there any other way of reducing/removing this bloom, perhaps some sort of subtraction method in post-processing, that I could try?

My D50 suffers a similar problem, although to a much lesser extent. Are the higher-end Nikons (D300, D700 etc) similarly affected or is this bloom something that I’ll have to live with until I get much longer pockets?

See page 83 of the fine manual.

That’s presumable long exposure noise reduction which ought to be on as the default. It takes a dark frame of the same duration in the same temp conditions after your shot to subtract from the actual exposure. ‘Colour bloom’ does not sound like the right term unless you’ve got some samples of this problem to explain better.

—
Paul Furman
www.edgehill.net
www.baynatives.com

all google groups messages filtered due to spam

Steve wrote:

We’ve been having some clear moonlit nights here in the UK and I’ve been having a go at some long-exposure night shots. A problem I’ve encountered is colour bloom (heat bloom) in the longer exposures where ‘hot’ components in the camera are interfering with the images causing a light ‘glow’ to appear. The longer the exposure, the worse the bloom.

Could you post some examples please?

—
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"Paul Furman" wrote in message

wrote:

On Thu, 11 Dec 2008 15:16:11 -0000, in rec.photo.digital.slr-systems "Steve" wrote:

We’ve been having some clear moonlit nights here in the UK and I’ve been having a go at some long-exposure night shots. A problem I’ve encountered is colour bloom (heat bloom) in the longer exposures where ‘hot’ components in the camera are interfering with the images causing a light ‘glow’ to appear. The longer the exposure, the worse the bloom.
The Nikon site explains why it occurs but doesn’t seem to give much help in finding a solution other than to "…allow the camera to cool…". This doesn’t seem to do much good. Is there any other way of reducing/removing this bloom, perhaps some sort of subtraction method in post-processing, that I could try?

My D50 suffers a similar problem, although to a much lesser extent. Are the higher-end Nikons (D300, D700 etc) similarly affected or is this bloom something that I’ll have to live with until I get much longer pockets?

See page 83 of the fine manual.

That’s presumable long exposure noise reduction which ought to be on as the default. It takes a dark frame of the same duration in the same temp conditions after your shot to subtract from the actual exposure. ‘Colour bloom’ does not sound like the right term unless you’ve got some samples of this problem to explain better.

Thanks. I’ve got some samples but nowhere to put them up. There’s a pic of what’s happening on the Nikon Europe support site after I searched for "Amp noise" in the D80 section (they call it "Electrical component heat colour bloom"). I would paste the link but it’s huge! Using long exposure noise reduction does seem to remove some of the bloom but very long exposures still show evidence of it. I’ll have to have a fiddle with processing to try and get rid of most of the rest. Maybe there’s also something else in the manual that I’ve either missed or misunderstood!

Steve

Steve wrote:

"Paul Furman" wrote

wrote:

"Steve" wrote:

We’ve been having some clear moonlit nights here in the UK and I’ve been having a go at some long-exposure night shots. A problem I’ve encountered is colour bloom (heat bloom) in the longer exposures where ‘hot’ components in the camera are interfering with the images causing a light ‘glow’ to appear. The longer the exposure, the worse the bloom.
The Nikon site explains why it occurs but doesn’t seem to give much help in finding a solution other than to "…allow the camera to cool…". This doesn’t seem to do much good. Is there any other way of reducing/removing this bloom, perhaps some sort of subtraction method in post-processing, that I could try?

My D50 suffers a similar problem, although to a much lesser extent. Are the higher-end Nikons (D300, D700 etc) similarly affected or is this bloom something that I’ll have to live with until I get much longer pockets?

See page 83 of the fine manual.

That’s presumable long exposure noise reduction which ought to be on as the default. It takes a dark frame of the same duration in the same temp conditions after your shot to subtract from the actual exposure. ‘Colour bloom’ does not sound like the right term unless you’ve got some samples of this problem to explain better.

Thanks. I’ve got some samples but nowhere to put them up. There’s a pic of what’s happening on the Nikon Europe support site after I searched for "Amp noise" in the D80 section (they call it "Electrical component heat colour bloom").

OK, so these must be like 30 minute exposures I guess.

I would paste the link but it’s huge! Using long exposure noise reduction does seem to remove some of the bloom but very long exposures still show evidence of it. I’ll have to have a fiddle with processing to try and get rid of most of the rest. Maybe there’s also something else in the manual that I’ve either missed or misunderstood!

—
Paul Furman
www.edgehill.net
www.baynatives.com

all google groups messages filtered due to spam

On Thu, 11 Dec 2008 23:42:04 -0000, "Steve"
wrote:

"Paul Furman" wrote in message

wrote:

On Thu, 11 Dec 2008 15:16:11 -0000, in rec.photo.digital.slr-systems "Steve" wrote:

We’ve been having some clear moonlit nights here in the UK and I’ve been having a go at some long-exposure night shots. A problem I’ve encountered is colour bloom (heat bloom) in the longer exposures where ‘hot’ components in the camera are interfering with the images causing a light ‘glow’ to appear. The longer the exposure, the worse the bloom.
The Nikon site explains why it occurs but doesn’t seem to give much help in finding a solution other than to "…allow the camera to cool…". This doesn’t seem to do much good. Is there any other way of reducing/removing this bloom, perhaps some sort of subtraction method in post-processing, that I could try?

My D50 suffers a similar problem, although to a much lesser extent. Are the higher-end Nikons (D300, D700 etc) similarly affected or is this bloom something that I’ll have to live with until I get much longer pockets?

See page 83 of the fine manual.

That’s presumable long exposure noise reduction which ought to be on as the default. It takes a dark frame of the same duration in the same temp conditions after your shot to subtract from the actual exposure. ‘Colour bloom’ does not sound like the right term unless you’ve got some samples of this problem to explain better.

Thanks. I’ve got some samples but nowhere to put them up. There’s a pic of what’s happening on the Nikon Europe support site after I searched for "Amp noise" in the D80 section (they call it "Electrical component heat colour bloom"). I would paste the link but it’s huge!

You should try using Tiny URL http://tinyurl.com/

Using long exposure noise
reduction does seem to remove some of the bloom but very long exposures still show evidence of it. I’ll have to have a fiddle with processing to try and get rid of most of the rest. Maybe there’s also something else in the manual that I’ve either missed or misunderstood!

Steve

Eric Stevens

"Paul Furman" wrote in message

Steve wrote:

"Paul Furman" wrote

wrote:

"Steve" wrote:

We’ve been having some clear moonlit nights here in the UK and I’ve been having a go at some long-exposure night shots. A problem I’ve encountered is colour bloom (heat bloom) in the longer exposures where ‘hot’ components in the camera are interfering with the images causing a light ‘glow’ to appear. The longer the exposure, the worse the bloom.

The Nikon site explains why it occurs but doesn’t seem to give much help in finding a solution other than to "…allow the camera to cool…". This doesn’t seem to do much good. Is there any other way of reducing/removing this bloom, perhaps some sort of subtraction method in post-processing, that I could try?

My D50 suffers a similar problem, although to a much lesser extent. Are the higher-end Nikons (D300, D700 etc) similarly affected or is this bloom something that I’ll have to live with until I get much longer pockets?

See page 83 of the fine manual.

That’s presumable long exposure noise reduction which ought to be on as the default. It takes a dark frame of the same duration in the same temp conditions after your shot to subtract from the actual exposure. ‘Colour bloom’ does not sound like the right term unless you’ve got some samples of this problem to explain better.

Thanks. I’ve got some samples but nowhere to put them up. There’s a pic of what’s happening on the Nikon Europe support site after I searched for "Amp noise" in the D80 section (they call it "Electrical component heat colour bloom").

OK, so these must be like 30 minute exposures I guess.

Around 10 minutes, although if I ramp up the ISO the effect is more obvious in less time as you would expect. It’s my first real attempt at long exposures so it could well be something I haven’t set right or something I’m not doing (or am doing but shouldn’t). Plan-B is stick to daylight!

I would paste the link but it’s huge! Using long exposure noise reduction does seem to remove some of the bloom but very long exposures still show evidence of it. I’ll have to have a fiddle with processing to try and get rid of most of the rest. Maybe there’s also something else in the manual that I’ve either missed or misunderstood!

—
Paul Furman
www.edgehill.net
www.baynatives.com

all google groups messages filtered due to spam

"Steve" wrote in message

Thanks. I’ve got some samples but nowhere to put them up. There’s a pic of what’s happening on the Nikon Europe support site after I searched for "Amp noise" in the D80 section (they call it "Electrical component heat colour bloom"). I would paste the link but it’s huge!

try www.tinyurl.com

I really shortens links and they have a long retention.

—
Peter

Here’s a link to an example of the heat bloom phenomenon:

http://tinyurl.com/5v9psd
or
< http://nikoneurope-en.custhelp.com/cgi-bin/nikoneurope_en.cf g/php/enduser/std_adp.php?p_sid=_VNrtgnh&p_lva=&p_fa qid=1141>

—
Mike Russell – http://www.curvemeister.com

In rec.photo.digital.slr-systems Paul Furman wrote:

wrote:

On Thu, 11 Dec 2008 15:16:11 -0000, in rec.photo.digital.slr-systems "Steve" wrote:

We’ve been having some clear moonlit nights here in the UK and I’ve been having a go at some long-exposure night shots. A problem I’ve encountered is colour bloom (heat bloom) in the longer exposures where ‘hot’ components in the camera are interfering with the images causing a light ‘glow’ to appear. The longer the exposure, the worse the bloom.

The Nikon site explains why it occurs but doesn’t seem to give much help in finding a solution other than to "…allow the camera to cool…". This doesn’t seem to do much good. Is there any other way of reducing/removing this bloom, perhaps some sort of subtraction method in post-processing, that I could try?

My D50 suffers a similar problem, although to a much lesser extent. Are the higher-end Nikons (D300, D700 etc) similarly affected or is this bloom something that I’ll have to live with until I get much longer pockets?

See page 83 of the fine manual.

That’s presumable long exposure noise reduction which ought to be on as the default. It takes a dark frame of the same duration in the same temp conditions after your shot to subtract from the actual exposure. ‘Colour bloom’ does not sound like the right term unless you’ve got some samples of this problem to explain better.

It seems to me that if the camera’s electronics heat the sensor more in some places than others, then starting out with a cold camera and doing this long exposure dark subtraction method wouldn’t work properly if the sensor started out cold for the first real long exposure because when the camera does the second long exposure for the dark subtraction it would already be warmed up. If we want both exposures to catch the sensor in the same state both should be taken when the sensor has warmed up to a stable state. Which would mean doing enough of a long exposure prior to the real shot to warm the sensor up to that state.

How long does it take to warm up to a stable state? Keep taking successive long exposures of say 30 secs with dark subtraction off until the effect no longer gets any worse. Then before doing your critical long shot with dark substraction set on do an exposure of half that length (the dark subtraction will do the other half) and then immediately do your critical shot.

—
Chris Malcolm

Chris Malcolm wrote:

It seems to me that if the camera’s electronics heat the sensor more in some places than others, then starting out with a cold camera and doing this long exposure dark subtraction method wouldn’t work properly if the sensor started out cold for the first real long exposure because when the camera does the second long exposure for the dark subtraction it would already be warmed up. If we want both exposures to catch the sensor in the same state both should be taken when the sensor has warmed up to a stable state. Which would mean doing enough of a long exposure prior to the real shot to warm the sensor up to that state.

Point sources of heat remain point sources of heat with one area having the advantage of dissipation while the other has constant heat applied to it at one location. The differential will remain.

From the posted image; for the exposure time the shooter is making there is no way he will not get this effect.

He would be better to shoot multiple frames and then stack them in s/w.

—
— r.p.e.35mm user resource: http://www.aliasimages.com/rpe35mmur.htm — r.p.d.slr-systems: http://www.aliasimages.com/rpdslrsysur.htm — [SI] gallery & rulz: http://www.pbase.com/shootin — e-meil: Remove FreeLunch.
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On Sat, 13 Dec 2008 12:06:02 -0500, Alan Browne
wrote:

Chris Malcolm wrote:

It seems to me that if the camera’s electronics heat the sensor more in some places than others, then starting out with a cold camera and doing this long exposure dark subtraction method wouldn’t work properly if the sensor started out cold for the first real long exposure because when the camera does the second long exposure for the dark subtraction it would already be warmed up. If we want both exposures to catch the sensor in the same state both should be taken when the sensor has warmed up to a stable state. Which would mean doing enough of a long exposure prior to the real shot to warm the sensor up to that state.

Point sources of heat remain point sources of heat with one area having the advantage of dissipation while the other has constant heat applied to it at one location. The differential will remain.

From the posted image; for the exposure time the shooter is making there is no way he will not get this effect.

He would be better to shoot multiple frames and then stack them in s/w.

The sensors used in DSLR cameras aren’t designed to take exposures of that duration. To take long night exposures, you should use a camera that is designed for that purpose.
I use a Starlight Express camera that is designed for my telescope. It has a built in cooling system that keeps the sensor cool, plus the sensor is designed to take long exposures. It does this by not having a shutter. You use software to turn the sensor on and off.
You should also use stacking software that someone mentioned because of heat inversions. If you look through a telescope at some planet….say Jupiter, and you look at it long enough, you will notice that is will be in focus, then for a brief time become blurry, then become focused again. This is due to heat inversions. It’s the same effect as when you look down a hot road in the summertime and you see the heat rising up off of the road and making the scene behind the rising heat look blurry.
This happens frequently as you view the night sky, so if you were to take one long exposure, you would invariably get some heat inversioins which would blur your picture somewhat. By taking mulitple short exposures, you can eliminate those that are blurry and only use the ones that are sharp. Then using stacking software, you stack the pictures to create one good picture.
One last point….if you are taking night shots of the sky, you need to factor in that the Earth is rotating, so if you take one long exposure with the camera mounted on a fixed tripod, the picture will show a light trail from the object you were photographing. To prevent this, you need a de-rotator which will rotate the camera in the opposite direction of the Earth.

Talker

Talker wrote:

show a light trail from the object you were photographing. To prevent this, you need a de-rotator which will rotate the camera in the opposite direction of the Earth.

Doh! and I though a de-rotator stopped the earth from turning while you took your shot.

—
— r.p.e.35mm user resource: http://www.aliasimages.com/rpe35mmur.htm — r.p.d.slr-systems: http://www.aliasimages.com/rpdslrsysur.htm — [SI] gallery & rulz: http://www.pbase.com/shootin — e-meil: Remove FreeLunch.
— usenet posts from gmail.com and googlemail.com are filtered out.

"Alan Browne" wrote in message

Talker wrote:

show a light trail from the object you were photographing. To prevent this, you need a de-rotator which will rotate the camera in the opposite direction of the Earth.

Doh! and I though a de-rotator stopped the earth from turning while you took your shot.

Never heard it called that. I always called it a clock drive.

The earth would stop turning if my wife bought me a D3x, or even a D3.

—
Peter

Talker wrote:

The sensors used in DSLR cameras aren’t designed to take exposures of that duration. To take long night exposures, you should use a camera that is designed for that purpose.
I use a Starlight Express camera that is designed for my telescope. It has a built in cooling system that keeps the sensor cool, plus the sensor is designed to take long exposures. It does this by not having a shutter. You use software to turn the sensor on and off.

Ah, at last, an authoritative response!

Thank for that, Talker.

j

Alan Browne wrote:

Talker wrote:

show a light trail from the object you were photographing. To prevent this, you need a de-rotator which will rotate the camera in the opposite direction of the Earth.

Doh! and I though a de-rotator stopped the earth from turning while you took your shot.

It helps to have a sky-hook, too.

Steve wrote:

We’ve been having some clear moonlit nights here in the UK and I’ve been having a go at some long-exposure night shots. A problem I’ve encountered is colour bloom (heat bloom) in the longer exposures where ‘hot’ components in the camera are interfering with the images causing a light ‘glow’ to appear. The longer the exposure, the worse the bloom.

The Nikon site explains why it occurs but doesn’t seem to give much help in finding a solution other than to "…allow the camera to cool…". This doesn’t seem to do much good. Is there any other way of reducing/removing this bloom, perhaps some sort of subtraction method in post-processing, that I could try?

My D50 suffers a similar problem, although to a much lesser extent. Are the higher-end Nikons (D300, D700 etc) similarly affected or is this bloom something that I’ll have to live with until I get much longer pockets?
TIA,
Steve

Without wishing to start another turf war, CCD sensors are intrinsically susceptible to heat problems with long exposures. This is one of the reasons that Canon use CMOS sensors, which generate much less heat. Some Nikons appear to use CMOS also, so if long-exposure shooting is important to you, you might need to buy a CMOS-equipped Nikon, or even a Canon for the job.

Colin D.

On Sat, 13 Dec 2008 17:20:19 -0500, "Peter"
wrote:

"Alan Browne" wrote in message

Talker wrote:

show a light trail from the object you were photographing. To prevent this, you need a de-rotator which will rotate the camera in the opposite direction of the Earth.

Doh! and I though a de-rotator stopped the earth from turning while you took your shot.

Never heard it called that. I always called it a clock drive.
The earth would stop turning if my wife bought me a D3x, or even a D3.

If you are using a telescope, you would choose either a
de-rotator or a wedge. I use a wedge since it’s more accurate than a de-rotator.(plus it’s one less thing that can break.) A wedge simply positions your telescope so that it’s angled at a precise angle that will allow the telescope’s own motors to turn the scope in the same plane as the Earth is turning. This keeps the telescope camera moving in the opposite direction as the Earth is moving. It’s basically just a piece of steel that is placed between the telescope and it’s mount. I have heard them referred to as a clock drive also, but in the catalogs, they are referred to as a de-rotator.
I guess my daughter is going to be very happy this Christmas since I got her a Canon 5D Mark II camera body, a Canon 70-200mm f/2.8L IS USM zoom lens, and a SanDisk Extreme IV 16GB Compact Flash Card. I broke the bank getting it but I know she will put it to good use.(she’s a staff photographer for the House Of Representatives, plus she does volunteer work for the animal rescue mission, taking pictures of the stray dogs and cats and posting them on the web in hopes of getting them adopted.).

Talker

"Talker" wrote in message

On Sat, 13 Dec 2008 17:20:19 -0500, "Peter"
wrote:

"Alan Browne" wrote in message

Talker wrote:

show a light trail from the object you were photographing. To prevent this, you need a de-rotator which will rotate the camera in the opposite direction of the Earth.

Doh! and I though a de-rotator stopped the earth from turning while you took your shot.

Never heard it called that. I always called it a clock drive.
The earth would stop turning if my wife bought me a D3x, or even a D3.

If you are using a telescope, you would choose either a
de-rotator or a wedge. I use a wedge since it’s more accurate than a de-rotator.(plus it’s one less thing that can break.) A wedge simply positions your telescope so that it’s angled at a precise angle that will allow the telescope’s own motors to turn the scope in the same plane as the Earth is turning. This keeps the telescope camera moving in the opposite direction as the Earth is moving. It’s basically just a piece of steel that is placed between the telescope and it’s mount. I have heard them referred to as a clock drive also, but in the catalogs, they are referred to as a de-rotator.

My telescope was mounted on a syncronous motor that was called a clock drive. I simply never heard of that term.

But then I bought the scope used, sight unseen, from a friend who told me he had a good six inch telescope for sale. I thought my kids would learn a lot from using it, so I bought it. I didn’t even know that a six inch scope meant six inches in diameter. Was I surprised. It caqme with the moter, tripod mount, instructions and spotting scope.

I guess my daughter is going to be very happy this Christmas since I got her a Canon 5D Mark II camera body, a Canon 70-200mm f/2.8L IS USM zoom lens, and a SanDisk Extreme IV 16GB Compact Flash Card. I broke the bank getting it but I know she will put it to good use.(she’s a staff photographer for the House Of Representatives, plus she does volunteer work for the animal rescue mission, taking pictures of the stray dogs and cats and posting them on the web in hopes of getting them adopted.).

You must be very proud of her.

—
Peter

John J wrote in news:s62dnQ-
:

Alan Browne wrote:

Talker wrote:

show a light trail from the object you were photographing. To prevent this, you need a de-rotator which will rotate the camera in the opposite direction of the Earth.

Doh! and I though a de-rotator stopped the earth from turning while you took your shot.

It helps to have a sky-hook, too.

And if your image is being taken anywhere near a body of water, several yards of shore line are a must.

On Dec 13, 8:06 pm, Talker wrote:

On Sat, 13 Dec 2008 17:20:19 -0500, "Peter"

wrote:

"Alan Browne" wrote in message

Talker wrote:

show a light trail from the object you were photographing.  To prevent this, you need a de-rotator which will rotate the camera in the opposite direction of the Earth.

Doh! and I though a de-rotator stopped the earth from turning while you took your shot.

Never heard it called that. I always called it a clock drive.

The earth would stop turning if my wife bought me a D3x, or even a D3.

     If you are using a telescope, you would choose either a de-rotator or a wedge.  I use a wedge since it’s more accurate than a de-rotator.(plus it’s one less thing that can break.)  A wedge simply positions your telescope so that it’s angled at a precise angle that will allow the telescope’s own motors to turn the scope in the same plane as the Earth is turning.  This keeps the telescope camera moving in the opposite direction as the Earth is moving.  It’s basically just a piece of steel that is placed between the telescope and it’s mount.      I have heard them referred to as a clock drive also, but in the catalogs, they are referred to as a de-rotator.
     I guess my daughter is going to be very happy this Christmas since I got her a Canon 5D Mark II camera body, a Canon 70-200mm f/2.8L IS USM zoom lens, and a SanDisk Extreme IV 16GB Compact Flash Card.  I broke the bank getting it but I know she will put it to good use.(she’s a staff photographer for the House Of Representatives, plus she does volunteer work for the animal rescue mission, taking pictures of the stray dogs and cats and posting them on the web in hopes of getting them adopted.).

Talker

No the wedge allows you to position your telescope according to latitude so that you only rotate it in one direction while you are tracking objects. You adjust it according to latitude, usually against the North Star.

Once this is done, you can add a clock drive to do the precise driving of the telescope or camera lens according to siderial time or the rate the stars move. This keeps stars in position. for exposures.

rule of thumb, buy the best mount and drive you can afford if you’re going to get into this seriously. And they are expensive, the best go for thousands and can take months to order, but results are worth it. You also need a good tripod to set this on.

Never heard the term derotator used. And yeah, I have an astronomy degree and have tracked professionally. With CCD tubes costing $50k and up. Don’t ask about the optics and computer support and staff and all that.

Talker wrote:

On Sat, 13 Dec 2008 17:20:19 -0500, "Peter"

The earth would stop turning if my wife bought me a D3x, or even a D3.

If you are using a telescope, you would choose either a
de-rotator or a wedge. I use a wedge since it’s more accurate than a de-rotator.(plus it’s one less thing that can break.) A wedge simply positions your telescope so that it’s angled at a precise angle that will allow the telescope’s own motors to turn the scope in the same plane as the Earth is turning. This keeps the telescope camera moving in the opposite direction as the Earth is moving. It’s basically just a piece of steel that is placed between the telescope and it’s mount. I have heard them referred to as a clock drive also, but in the catalogs, they are referred to as a de-rotator.

A de-rotator is a completely different device.

A comuter-controlled alt-azimuth mount can track objects throught the night without any difficulty, but the field of view as seen through the eyepiece will rotate as the scope turns to follow the object. That makes it unusable for long-exposure astrophotography.

A field de-rotator attaches to the eyepiece and turns the camera to compensate, allowing people to use an alt-azimuth mount for long exposures.

—
Ray Fischer

John J wrote:

Talker wrote:

The sensors used in DSLR cameras aren’t designed to take exposures of that duration. To take long night exposures, you should use a camera that is designed for that purpose. I use a Starlight Express camera that is designed for my
telescope. It has a built in cooling system that keeps the sensor cool, plus the sensor is designed to take long exposures. It does this by not having a shutter. You use software to turn the sensor on and off.

Ah, at last, an authoritative response!

Thank for that, Talker.

The real point is that with stacking s/w, expensive cooled sensors are not required – you can use a DSLR (or even a P&S). Many multiple short exposure images stacked have higher snr than any ‘enthusiast’ level cooled sensor.

—
— r.p.e.35mm user resource: http://www.aliasimages.com/rpe35mmur.htm — r.p.d.slr-systems: http://www.aliasimages.com/rpdslrsysur.htm — [SI] gallery & rulz: http://www.pbase.com/shootin — e-meil: Remove FreeLunch.
— usenet posts from gmail.com and googlemail.com are filtered out.

Bryon Lape wrote:

John J wrote in news:s62dnQ-
:

Alan Browne wrote:

Talker wrote:

show a light trail from the object you were photographing. To prevent this, you need a de-rotator which will rotate the camera in the opposite direction of the Earth.

Doh! and I though a de-rotator stopped the earth from turning while you took your shot.

It helps to have a sky-hook, too.

And if your image is being taken anywhere near a body of water, several yards of shore line are a must.

And if taken from an airplane be sure to wash the windows with prop-wash.

—
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Colin.D wrote:

Steve wrote:

We’ve been having some clear moonlit nights here in the UK and I’ve been having a go at some long-exposure night shots. A problem I’ve encountered is colour bloom (heat bloom) in the longer exposures where ‘hot’ components in the camera are interfering with the images causing a light ‘glow’ to appear. The longer the exposure, the worse the bloom.
The Nikon site explains why it occurs but doesn’t seem to give much help in finding a solution other than to "…allow the camera to cool…". This doesn’t seem to do much good. Is there any other way of reducing/removing this bloom, perhaps some sort of subtraction method in post-processing, that I could try?

My D50 suffers a similar problem, although to a much lesser extent. Are the higher-end Nikons (D300, D700 etc) similarly affected or is this bloom something that I’ll have to live with until I get much longer pockets?

Without wishing to start another turf war, CCD sensors are intrinsically susceptible to heat problems with long exposures. This is one of the reasons that Canon use CMOS sensors, which generate much less heat. Some Nikons appear to use CMOS also, so if long-exposure shooting is important to you, you might need to buy a CMOS-equipped Nikon, or even a Canon for the job.

The newer Nikons are CMOS, at least the D300 & D700, probably D90. The D50, D70, D80, D200 are CCD. I don’t think I’ve ever done more than 30 second exposures but it’s supposed to be fine with all of these models for normal landscape photography at like 5 or 10 minutes. Looking at a black sky is much more challenging though.

"Peter" wrote in message

"Talker" wrote in message

On Sat, 13 Dec 2008 17:20:19 -0500, "Peter"
wrote:

"Alan Browne" wrote in message

Talker wrote:

show a light trail from the object you were photographing. To prevent this, you need a de-rotator which will rotate the camera in the opposite direction of the Earth.

Doh! and I though a de-rotator stopped the earth from turning while you took your shot.

Never heard it called that. I always called it a clock drive.
The earth would stop turning if my wife bought me a D3x, or even a D3.

If you are using a telescope, you would choose either a
de-rotator or a wedge. I use a wedge since it’s more accurate than a de-rotator.(plus it’s one less thing that can break.) A wedge simply positions your telescope so that it’s angled at a precise angle that will allow the telescope’s own motors to turn the scope in the same plane as the Earth is turning. This keeps the telescope camera moving in the opposite direction as the Earth is moving. It’s basically just a piece of steel that is placed between the telescope and it’s mount. I have heard them referred to as a clock drive also, but in the catalogs, they are referred to as a de-rotator.

My telescope was mounted on a syncronous motor that was called a clock drive. I simply never heard of that term.

But then I bought the scope used, sight unseen, from a friend who told me he had a good six inch telescope for sale. I thought my kids would learn a lot from using it, so I bought it. I didn’t even know that a six inch scope meant six inches in diameter. Was I surprised. It caqme with the moter, tripod mount, instructions and spotting scope.

I guess my daughter is going to be very happy this Christmas since I got her a Canon 5D Mark II camera body, a Canon 70-200mm f/2.8L IS USM zoom lens, and a SanDisk Extreme IV 16GB Compact Flash Card. I broke the bank getting it but I know she will put it to good use.(she’s a staff photographer for the House Of Representatives, plus she does volunteer work for the animal rescue mission, taking pictures of the stray dogs and cats and posting them on the web in hopes of getting them adopted.).

—
Peter

will you adopt me too?
I need a new camera

You must be very proud of her.

YES lovely

(nice of you Dad >>>Merry Xmas)

On Sun, 14 Dec 2008 07:19:16 -0500, "Peter"
wrote:

"Talker" wrote in message

On Sat, 13 Dec 2008 17:20:19 -0500, "Peter"
wrote:

"Alan Browne" wrote in message

Talker wrote:

show a light trail from the object you were photographing. To prevent this, you need a de-rotator which will rotate the camera in the opposite direction of the Earth.

Doh! and I though a de-rotator stopped the earth from turning while you took your shot.

Never heard it called that. I always called it a clock drive.

This is why I referred to it as a de-rotator…
http://www.astronomics.com/main/product.asp/catalog_name/ast ronomics/category_name/552Q3PMHDHXR8LT2TA3BXQ0QG5/product_id /1220

The earth would stop turning if my wife bought me a D3x, or even a D3.

If you are using a telescope, you would choose either a
de-rotator or a wedge. I use a wedge since it’s more accurate than a de-rotator.(plus it’s one less thing that can break.) A wedge simply positions your telescope so that it’s angled at a precise angle that will allow the telescope’s own motors to turn the scope in the same plane as the Earth is turning. This keeps the telescope camera moving in the opposite direction as the Earth is moving. It’s basically just a piece of steel that is placed between the telescope and it’s mount. I have heard them referred to as a clock drive also, but in the catalogs, they are referred to as a de-rotator.

My telescope was mounted on a syncronous motor that was called a clock drive. I simply never heard of that term.

But then I bought the scope used, sight unseen, from a friend who told me he had a good six inch telescope for sale. I thought my kids would learn a lot from using it, so I bought it. I didn’t even know that a six inch scope meant six inches in diameter. Was I surprised. It caqme with the moter, tripod mount, instructions and spotting scope.

I guess my daughter is going to be very happy this Christmas since I got her a Canon 5D Mark II camera body, a Canon 70-200mm f/2.8L IS USM zoom lens, and a SanDisk Extreme IV 16GB Compact Flash Card. I broke the bank getting it but I know she will put it to good use.(she’s a staff photographer for the House Of Representatives, plus she does volunteer work for the animal rescue mission, taking pictures of the stray dogs and cats and posting them on the web in hopes of getting them adopted.).

You must be very proud of her.

Yes I am. Years ago, I let her use my Pentax 35mm camera to play with. She became very proficient at taking pictures and ended up becoming her high school’s newspaper photographer.
When she went to college, she majored in photogrpahy and had a short video she made, considered good enough to be submitted to the Cannes Film Festival for consideration.(she didin’t win, but still…..)

Talker

On Mon, 15 Dec 2008 16:19:19 -0500, "KatWoman" wrote:

will you adopt me too?
I need a new camera

You must be very proud of her.

YES lovely

(nice of you Dad >>>Merry Xmas)

Well, I can’t afford to adopt anyone….my daughter keeps me broke.<g> When you consider that I paid for her college education, 4 new cars, her one month trip to Brazil, her one week trip to Europe, down payments on her two houses, three computers for her, and a myriad of other expenses (real estate school, her upcoming wedding, repairs for her car, etc., I guess I’ve spent over$150,000 on her needs so far. That’s enough to keep me broke.<g> It never bothered me to spend the money on her…..I enjoyed it. She’s my only child and I love her dearly.
Anyway, Merry Christmas to you and thanks for the good will!

Talker