Dark Frame Library With Nikon DSLR

[Juno16]

Hi All,

I was reading the post Dark Frame Library from Jockinireland viewtopic.php?f=22&t=3674.

I didn't want to add another post because my question is mainly concerning Nikon DSLRS.

Nikon dslr's do not display the camera sensor temperature in my imaging application (Astrophotography Tool) and I have heard that the temperature isn't available in other imaging software.

I always shoot darks, but I can never get a true sensor temperature. I have to rely on the ambient temp and I always shoot at the end of a session when the temperature is lower.

I did a simple test this afternoon with an image of M31 that I shot recently.

The image below was processed with the same flow in Startools. This image was stacked using lights, darks, flats, and bias frames.

Full res image

This image was stacked using lights, no darks, flats, and bias frames.

Full res image

I cannot tell any difference. Am I treading in dangerous territory?

Thanks,
Jim

[bladekeeper]

Hi Jim! You've got more what appears to be amp glow (not sure if that is a thing with a DSLR) in the non-darks image. It is prevalent in the corners especially.

[SkyHiker]

Hi Jim! You've got more what appears to be amp glow (not sure if that is a thing with a DSLR) in the non-darks image. It is prevalent in the corners especially.

Maybe that's caused by the darks; since darks usually are strongest at the center they have a gradient at the edges. If you subtract the darks you subtract that gradient and the image will be flat. Not doing so will show the gradient. Plausible? ...

[JayTee]

From what I'm able to find on the interweb, the D5300 does not suffer from amp glow. In fact, that camera body is praised across the board as a GREAT AP DSLR camera. So the hunt begins again for that discoloration.

JT

[EAGLE 5]

I agree with the others that the dark frames are noticeable in your images, not that the one without darks is bad.

Perhaps if you redo this test with just an "empty" star field the purple glow in the corners might seem more apparent.

[JayTee]

The D5300 does not report sensor temperature anywhere. You're only reasonable alternative is to get a TEMperHUM device (they're inexpensive) which records the outside air temperature and humidity. APT allows you to embed this information in the title of your image so that way, at least, you'll have a temperature on which to go by.
http://www.bbastrodesigns.com/diagonal.htm

Cheers,
JT

[Juno16]

Hi Jim! You've got more what appears to be amp glow (not sure if that is a thing with a DSLR) in the non-darks image. It is prevalent in the corners especially.

Absolutely Bryan, I do see that in the corners now. Thanks for pointing that out!

Thanks,
Jim

[Juno16]

Hi Jim! You've got more what appears to be amp glow (not sure if that is a thing with a DSLR) in the non-darks image. It is prevalent in the corners especially.

Maybe that's caused by the darks; since darks usually are strongest at the center they have a gradient at the edges. If you subtract the darks you subtract that gradient and the image will be flat. Not doing so will show the gradient. Plausible? ...

Maybe so. If that is the case, how important is the sensor temperature?

Thanks,
Jim

[Juno16]

I agree with the others that the dark frames are noticeable in your images, not that the one without darks is bad.

Perhaps if you redo this test with just an "empty" star field the purple glow in the corners might seem more apparent.

Possibly so. I was just messing around while I was watching football and the NLDS. I might give that a try if I can figure out how.

Thanks,
Jim

The D5300 does not report sensor temperature anywhere. You're only reasonable alternative is to get a TEMperHUM device (they're inexpensive) which records the outside air temperature and humidity. APT allows you to embed this information in the title of your image so that way, at least, you'll have a temperature on which to go by.
http://www.bbastrodesigns.com/diagonal.htm

Cheers,
JT

Thanks JT. Is that the right link?

Thanks,
Jim

[JayTee]

Don't know how that link got there.

Here's the one I use:
https://pcsensor.com/usb-hygrometer/temperhum.html
JT

[Juno16]

Don't know how that link got there.

Here's the one I use:
https://pcsensor.com/usb-hygrometer/temperhum.html
JT

That is a really nifty gadget JT!

That would definitely give me a better handle on the camera temperature since there is no actual sensor temp available.

Usually, I just take darks after imaging. Of course, afterwards is when the ambient temperature is always the same or usually lower
than the imaging temperature. If the temperature from the start to the end of imaging changes more than 5 degrees, should several sets of darks be used in the stacking process?

Thanks,
Jim

[JayTee]

Hi Jim,

When this device is set up correctly, APT will read the data directly from this device for each of your images.

JT

[Juno16]

Hi Jim,

When this device is set up correctly, APT will read the data directly from this device for each of your images.

JT

JT,

Do you attach this temperature sensor directly to the camera while imaging, or in the vicinity (like the mount)?
I’m sure that it would be best attached to the camera, but I rather not have another cable to manage unless you feel it is needed there.
Overall, it looks like I do need darks, however, due to the inability to measure the sensor temperature accurately, close will count.

The sensor does look like a great idea especially if it communicates with APT and can stamp the temperature to the image file name. Can’t beat the price!

Thanks,
Jim

[yobbo89]

I can see a substantial difference in the low signal areas and the corners from amp glow.

lovely image btw.

[Juno16]

I can see a substantial difference in the low signal areas and the corners from amp glow.

lovely image btw.

Yes, Bryan mentioned that also and I definately see it now too. I was getting distracted watching the ball game as it was the top of ninth inning and the Braves were down a run to the Cardinals. I definately need to shoot darks. I took JT`s advice and ordered the temperature probe. Close is my best shot at creating a dark library. Thanks for the nice comment on the image! Actually, the darks that I used to process the first image were shot at 'about' 75 degrees f. The lights were shot starting at 83 degrees and ended at 78 degrees. Sorry about the poor formatting! I am running on the treadmill and using the firestick remote one letter at a time. Thanks for your help! Jim

[yobbo89]

well it looks like your darks worked well even at differital temp difference , i guess you could do a category of temps for the darks/lights ie have like 3-5 deg tolerance instead of shooting at every 1 degree change for darks

[Juno16]

Hi Jim,

When this device is set up correctly, APT will read the data directly from this device for each of your images.

JT

Hi JT,

Thanks for the link to the TEMPerHUM. Got one from Amazon for $25.

I was kind of disappointed at first because I couldn’t calibrate the temperature in the software. Then I looked at Astrophotography Tool and saw that APT communicates directly with the TEMPerHUM and will even allow a temperature offset to correct for calibration. Got the temperature writing to the image filename also.

Just need a long usb extension cable and can put the camera in a box in the refrigerator and shoot some darks!

I know that this is a pretty crude method compared to an actual sensor temperature, but it my best shot.

Thanks for the help JT!

Jim

[JayTee]

In your case, an ice chest with those blue ice blocks might be the better way to go. I think you would have more control over temperature based on the number of blue ice blocks you had in the ice chest. Plus you won't need a long cable.

Cheers,
JT

[Juno16]

In your case, an ice chest with those blue ice blocks might be the better way to go. I think you would have more control over temperature based on the number of blue ice blocks you had in the ice chest. Plus you won't need a long cable.

Cheers,
JT

Great idea!

I will still need a cable because the one supplied with the TEMPerHUM is only about 24” long!

Thanks,
Jim

[JayTee]

I will still need a cable because the one supplied with the TEMPerHUM is only about 24” long!

Not if you put your laptop on the ice chest lid... almost seems like I've done this before.

JT