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Light Leak?

Astrophotography DSLR Equipment Imaging
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#1 Ewentworth83

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Posted 08 August 2022 - 02:09 PM

Hello, 

 

I'm fairly new to Astrophotography, and been really enjoying the few cloudless nights I've had lately (I live in Phoenix, and it's monsoon season with blaring hot nights). I got the HEQ5 about 6 weeks ago, and I've been running through sessions in my back yard to work out all the bugs and kinks (Bortle 7 with 100+ degree nights won't give me great images, but getting the practice in before making a trip to the Bortle 2 desert). I've figured out a lot in the past few weeks, and while initially regretting trying NINA, it is proving to be a very helpful program once getting past the learning curve. There is still equipment I want to get/upgrade before going out on a real imaging session, but I also have an issue with the camera that I can't seem to fully figure out. 

 

I have a Nikon D5300 Full Spectrum and it was the 1st Astro Mod I did myself, so it's quite possible that I messed something up; however all of my images have much more light at the bottom. I figured light leak, so I grabbed some electrical tape to see if that made any kind of difference, and while taping up the viewfinder helped around the top of the image, I did not notice any difference at the bottom. I took some images with the cap on and bumped the exposure and whites in Camera RAW and I get some discoloring at the bottom of the image, fairly consistently. Once I saw that, I wrapped my camera in a blanket and placed it in the dark corner of my closet with the lights off, and checked in Camera RAW again. I still received the same discoloration at the bottom of the image, even with next to no light available to leak in. I'm not sure what else to try at the moment, so thought I would reach out to you helpful folks for advice. This is my first post on a forum like this, so if there is something I'm missing or would be helpful to know, please tell me and I'll get you the info. Thanks for any help you can provide! 

 

Celestron 130SLT

SkyWatcher HEQ5 Mount

Nikon D5300 Full Spectrum Mod

Running NINA

(No tracking scope or autofocus... yet)

(Will also upgrade the telescope soon)

 

light_test.jpg



#2 SpaceMax

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Posted 08 August 2022 - 07:37 PM

Others may comment but it looks a lot like amplifier glow. Can you switch on long exposure noise reduction and take another dark frame if the same duration? Put the camera with cap on in the bag and take a manual 30sec exposure in raw. It will take a subsequent exposure of equal length and subtrakt it from the first exposure. If it’s gone in the resulting raw file, then it is ampglow. Unless there are more weird things at play.

#3 Kevin_A

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Posted 08 August 2022 - 10:02 PM

Ampglow for sure.  



#4 jml79

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Posted 08 August 2022 - 10:58 PM

Ampglow, you will need to take the time to shoot some dark frames to get rid of it. If I shoot darks, I take my flats first while everything is still setup, then take my scope off the mount, plug in an intervalometer and let the camera sit there and shoot darks while I pack up. I hate wasting imaging time for darks so I try to find any way to be doing something else while the camera clicks away in the dark. Bias frames only take a few seconds to shoot so aren't as annoying.



#5 Michael Covington

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Posted 08 August 2022 - 11:00 PM

I seem to recall that my unmodified D5300 has something like that.  It is either amp glow or some kind of irregularity in the sensor, and it goes away when you take and subtract dark frames.  



#6 Michael Covington

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Posted 08 August 2022 - 11:01 PM

Unlike flats, darks don't have to be re-done at every session -- just when the ambient temperature changes appreciably.



#7 bobharmony

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Posted 08 August 2022 - 11:17 PM

Yep - I am using a modded D5300 and have the same glow at the bottom edge which is handled quite nicely by dark frames.

 

Bob



#8 Ewentworth83

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Posted 09 August 2022 - 11:01 AM

Thanks for all the replies! Ampglow makes sense, but I don't know why my darks aren't taking care of it. Here is a quick stretched image with overexposure to show the same spot. This is stacked with 40 darks taken immediately after my lights to match the shutter speed and iso, as well as 20 flats. matching iso and histogram. It looks like the same spot, which is creating a larger glow in the shots that also radiates to the left in a half circular pattern. This is showing on all my images, but not getting removed through stacking. I know I'm missing something here... 

 

FULL-STACK-FIREWORKS-GALAXY-NGC-6946.jpg

 

 

 

 



#9 Ewentworth83

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Posted 09 August 2022 - 12:14 PM

Here's a less exaggerated version so you can see what it is actually doing to my image. This is just a quick stretch with bare minimum PS work. The light at the bottom washes out most of the lower half of the image and creeps into the Fireworks Galaxy. 

 

FULL-STACK-FIREWORKS-GALAXY-NGC-6946-(2).jpg



#10 asanmax

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Posted 09 August 2022 - 01:36 PM

That amp glow is not typical for a D5300 sensor. I've personally modified and tested hundreds of D5300 cameras and have never seen that effect.

I am on my fourth full spectrum D5300 now and I don't use darks at all. 

Question for you. Do you shoot in live view or do you use the mirror lockup?



#11 asanmax

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Posted 09 August 2022 - 01:37 PM

By the way, your latest image seems to look like it's the light pollution gradient and not the amp glow.



#12 Ewentworth83

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Posted 09 August 2022 - 02:05 PM

I connect the camera through NINA with a 1 second delay after the shutter. I'm also covering my eyepiece to avoid any leak there. Phoenix is to the south of me, and I'm shooting to the North. I know I'm getting light pollution regardless, but would it still be so uneven? 


Edited by Ewentworth83, 09 August 2022 - 03:01 PM.


#13 asanmax

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Posted 09 August 2022 - 03:20 PM

I connect the camera through NINA with a 1 second delay after the shutter. I'm also covering my eyepiece to avoid any leak there. Phoenix is to the south of me, and I'm shooting to the North. I know I'm getting light pollution regardless, but would it still be so uneven? 

Well, my images look exactly the same when I shoot with a UV/IR cut filter. I image from the city from a Bortle 8 zone.

All you need is to learn how to get rid of that gradient. You may want to look up  something like 'light pollution gradient removal' etc.

Also, I don't think you need that 1 sec delay because the shutter shouldn't really cause any problems.



#14 Ewentworth83

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Posted 09 August 2022 - 07:09 PM

Great, well thanks for the help! I'll give it a shot and see how it turns out. I appreciate all the feedback! 



#15 vidrazor

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Posted 10 August 2022 - 09:04 AM

I connect the camera through NINA with a 1 second delay after the shutter. I'm also covering my eyepiece to avoid any leak there. Phoenix is to the south of me, and I'm shooting to the North. I know I'm getting light pollution regardless, but would it still be so uneven? 

Try shooting with a different camera if you can and see if you get the same sky glow at that location. Amp glow like that seems unusual for a D5300. I don't know if it would do something like that, but could there be some kind of undue pressure on the sensor on that side? Are there any IR LEDs inside the camera?


Edited by vidrazor, 10 August 2022 - 09:09 AM.


#16 asanmax

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Posted 10 August 2022 - 11:38 AM

Try shooting with a different camera if you can and see if you get the same sky glow at that location. Amp glow like that seems unusual for a D5300. I don't know if it would do something like that, but could there be some kind of undue pressure on the sensor on that side? Are there any IR LEDs inside the camera?

Good suggestions. In addition to this, do you happen to remember if you removed the rubber gasket that sits on top of the sensor? It serves as a filter holder as well as a protection from stray light that may enter from the sides of the sensor.



#17 BPoletti

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Posted 10 August 2022 - 02:25 PM

Have you considered shooting exposures on the camera from inside a cardboard box blackened of 5 sides?  If the problem persists shoot exposures from inside a completely blackened on all 6 sides.  If the problem still persists, then it's inside the camera.  If the problem is removed shooting the five-sided box or six-sided box, then the problem may be a leak around the lens munt or elsewhere from external light.  But the box orientation may give you a hint abut the source of the problem.


Edited by BPoletti, 10 August 2022 - 02:25 PM.


#18 Kevin_A

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Posted 10 August 2022 - 09:02 PM

One thing i noticed while testing ampglow on a D5300 was that iso200 was vastly better than Iso400 for ampglow. Anything higher was much worse. Heat is the enemy here but darks should get rid of it. In the winter months i use either 200 or 400 but in the summer I use only iso200 and sometimes if it is really hot I will use LENR. It does waste time but the heat just cooks my sensor. Recently however i have just been using cooled cameras in the summer. 
the top photo was iso200 for 120s stretched 5ev

secondbphoto was iso400 for 60s stretched 5ev
 

iso200_120s.jpg
iso400_60s.jpg

Edited by Kevin_A, 10 August 2022 - 09:05 PM.


#19 Michael Covington

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Posted 10 August 2022 - 10:10 PM

There may be an actual change in sensor mode between ISO 200 and 400.  DSLRs have been known to do such things.

(Although, looking at photonstophotos.net, I don't see any clear indication that the D5300 does this.)



#20 bobharmony

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Posted 10 August 2022 - 10:12 PM

Here is a screen shot of one of my darks from a session last week with the D5300.  Temp was 20C or 68F and I was shooting ISO 200.  To me it looks suspiciously like the dark shared by the OP in post #1 of this thread, although not stretched as hard.  From later posts it appears there is also some sort of gradient in the lights that goes well beyond this, but darks will remove at least this issue from the lights and let the OP deal with just the lights issues.

 

Bob

 

Screenshot 2022-08-10 230949.jpg


Edited by bobharmony, 10 August 2022 - 10:14 PM.


#21 Ewentworth83

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Posted 11 August 2022 - 12:57 AM

Thanks everyone! I'll definitely jump to iso200 for my next shoot. Even at night, it's often still over 100 F here. I know the darks should be pulling this out, but for some reason it's not. I'll have to review my settings in DSS and make sure everything looks good. I've been working on light pollution gradient removal, and between some free techniques and GradientXterminator (still on the free trial) things are looking better, but still not great. I may just need more practice. I think I overdid it with this one today,  but I'll get there. Still pretty new. 

 

Screenshot_20220810-225458_OneDrive.jpg


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#22 vidrazor

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Posted 11 August 2022 - 05:26 AM

Thanks everyone! I'll definitely jump to iso200 for my next shoot. Even at night, it's often still over 100 F here. I know the darks should be pulling this out, but for some reason it's not. I'll have to review my settings in DSS and make sure everything looks good. I've been working on light pollution gradient removal, and between some free techniques and GradientXterminator (still on the free trial) things are looking better, but still not great. I may just need more practice. I think I overdid it with this one today,  but I'll get there. Still pretty new.

Check out Siril to process your data as well. Siril has to ability to do gradient removal on a per-sub basis, and remove gradients before stacking (as the gradients shift during the course of the evening as you track across the sky), as well as having the recently introduced GraXpert gradient removal tool embedded into the app, among other processes like photometric color calibration, Asinh transformation, histrogram stretching, and the recently added generalized hyperbolic transformation.


Edited by vidrazor, 11 August 2022 - 05:28 AM.

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#23 Challenger75

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Posted 11 August 2022 - 09:57 AM

Check out Siril to process your data as well. Siril has to ability to do gradient removal on a per-sub basis, and remove gradients before stacking (as the gradients shift during the course of the evening as you track across the sky), as well as having the recently introduced GraXpert gradient removal tool embedded into the app, among other processes like photometric color calibration, Asinh transformation, histrogram stretching, and the recently added generalized hyperbolic transformation.

Thanks for this GraXpert link. Never heard of that one before. 



#24 vidrazor

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Posted 11 August 2022 - 11:37 AM

Thanks for this GraXpert link. Never heard of that one before.

That's the link for the standalone app, it's already incorporated into Siril.


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