DSLR mod vs no-mod, Ha imaging

[Ken Mitchell]

During my first narrowband imaging a couple weeks ago, I decided to do a short test with my modded d90 vs my unmodded dslr d610 and 7nm 2" Baader Ha filter.

This is the gear used :

-Camera:  modded Nikon d90(1 filter), stock Nikon d610

-Optics: TS-Optics Photoline 72mm f/6 FPL53+TSflat72

-Mount: Skywatcher Star Adventurer

-Guidescope: TS-Optics Optics 50 mm DeLuxe Mini 

-Guidecamera:  ZWO ASI120MC-S

-Filters: Baader 7nm 2" Ha 

-Software: Photoshop

I decided to use exact the same settings on both cameras so not compensating for the light loss with the unmodded camera, exposure and iso were the same.

Camera settings for both were: 180sec subs at iso1600

 

First the single subs: These are the raw images with a minor stretch to reveal details. No other editing was done. 

Stock Nikon d610 (ff)

 

Modded Nikon d90 (aps-c)

First observations: Yes it is possible to image with an unmodded dslr + Ha filter, there is actually some data even with such a low exposure for Ha! 

                              Noise is more visible with the d610. I believe this is because of the low SNR and with 4 or 5min exposure it would probably be a lot less.

                              The amount of detail/data captured is perhaps one of the most obvious differences.

 

Next stacking: I was only able to get 9 images with the d610 so it gave me a total of 27min. For the d90 I selected 9 random images to get the same total amount of exposure.

                       In both stacks all the calibration files were added. The image was slightly stretched just as in the single subs, no other editing was done. 

Stock Nikon d610(ff)

 

Modded Nikon d90 (aps-c)     

       

First observations: roughly the same as with the single subs. Noise is slightly improved for the unmodded stack with the use of calibration frames.

 

Conclusions:

The amount of data gathered with the unmodded dslr just can't match the modded dslr.

The 27min unmodded stack is imo very similar to the 180sec single modded image in terms of data capturing.

As I said before, yes it is possible imaging with an unmodded dslr+narrowband(ha) but is it worth it? Well that's up to you, personally if I wouldn't have a modded dslr I would rather use that imaging time to capture extra RGB data.

 

As extra I made a separate stack of 28min(7x240sec) RGB data, without Ha filter, taken with the stock d610. Just a slight stretched, no other edits were made.

and the colored version

 

When time permits I want to do some more testing with this configuration, how long a single unmodded sub has to be to match a modded sub for example.

I know it's not much but hopefully this can be of help to some.

Thank you.

 

Ken

[OJ87]

Thank you very much, very useful topic. I know what I'm doing now, modifying my 77d ✌

[aatdalton]

Nice examples! In your second picture it almost looks like there's distinct levels of brightness like a posterize filter was used. Is that just from the single frame or a visual coincidence? 

[Alien 13]

If anything I think this experiment shows that modding a camera might not be necessary depending on the particular model, I cant speak from experience on Nikon cameras but certain Canon models have plenty of Ha without introducing the negative effects modding brings.

Alan

[ollypenrice]

When preparing the images for comparison I think the background level should be brought to the same value in each.

Olly

[fireballxl5]

1 hour ago, Alien 13 said:

introducing the negative effects modding brings.

Other than making the camera more difficult to use for regular daytime photography what other negative effects are there?

I'm interested as I have a modified Canon 40D that I use as my primary travel astro camera.

[Alien 13]

Just now, fireballxl5 said:

Other than making the camera more difficult to use for regular daytime photography what other negative effects are there?

I'm interested as I have a modified Canon 40D that I use as my primary travel astro camera.

It depends on the mod but some destroy the auto sensor clean and the ability to auto focus with camera lenses, other negatives are increased star bloat when using lenses or some refactors that were not designed to correct the infra red end of the spectrum and as you say most mods render the camera useless for daytime photography.

Alan

[fireballxl5]

7 minutes ago, Alien 13 said:

It depends on the mod but some destroy the auto sensor clean and the ability to auto focus with camera lenses, other negatives are increased star bloat when using lenses or some refactors that were not designed to correct the infra red end of the spectrum and as you say most mods render the camera useless for daytime photography.

Alan

yes, I've lost auto focus and maybe the cleaning function (though not 100% certain about this). 

Star bloat may be a problem I have with one imaging config. I sometimes get 'red bloat' around stars. Could this be unfiltered IR light not focusing and being detected by the R pixels? Or it could be poor focusing though😬

Andy

[Alien 13]

1 minute ago, fireballxl5 said:

yes, I've lost auto focus and maybe the cleaning function (though not 100% certain about this). 

Star bloat may be a problem I have with one imaging config. I sometimes get 'red bloat' around stars. Could this be unfiltered IR light not focusing and being detected by the R pixels? Or it could be poor focusing though😬

Andy

The red bloat will be the inability to bring the red and IR to the same focus point can be cured with an additional filter but that kind of defeats the object.

Alan

[fireballxl5]

19 minutes ago, Alien 13 said:

The red bloat will be the inability to bring the red and IR to the same focus point can be cured with an additional filter but that kind of defeats the object.

Alan

But as I use an Astronomik CLS-CCD clip-in filter shouldn't this remove the IR?

Andy

[Alien 13]

3 minutes ago, fireballxl5 said:

But as I use an Astronomik CLS-CCD clip-in filter shouldn't this remove the IR?

Andy

It should but it would still allow more IR through then the original factory fitted camera filter..

Alan

[fireballxl5]

Ok, thanks Alan. I need to try LRGB imaging through this combo with a mono CCD to see if my (Baader) filters better control the IR.

Regards, Andy

[Alien 13]

4 minutes ago, fireballxl5 said:

Ok, thanks Alan. I need to try LRGB imaging through this combo with a mono CCD to see if my (Baader) filters better control the IR.

Regards, Andy

Hi Andy, that is the big advantage of a mono camera and filters, you can focus each band separately.

Alan

 

[Ken Mitchell]

2 hours ago, ollypenrice said:

When preparing the images for comparison I think the background level should be brought to the same value in each.

Olly

Right, I didn't take that into account. 

Made some new side by side comparison, only used the background slider to adjust the values. So when I measured the background brightness values were the same. Hope this is better.

 

Value 4 and 5

 

Value 10 and 20

 

Value 20 and 30

 

Ken

[Ken Mitchell]

3 hours ago, aatdalton said:

Nice examples! In your second picture it almost looks like there's distinct levels of brightness like a posterize filter was used. Is that just from the single frame or a visual coincidence? 

Also noticed that yes, not sure what caused this, the only adjustment I made were the levels. 

Ken