Modified DSLRs

[smr]

Hi,

I'm wondering whether to buy a modded DSLR. If so I'd probably buy a second hand 600D for around £160, and then get it modded for around £100. So £260 in total. If I decided to sell it I don't think I would lose too much money on it.

I shoot with an unmodified DSLR at the moment and have been happy shooting it with it but there are one or two targets I have tried to image which give to me, underwhelming results, and that's because it's blocking so much Ha. I'd estimate that it probably lets through 20-30 percent of Ha light, whereas a modded DSLR I assume lets in 100 percent of Ha emissions to pass through to the sensor.

Before going ahead with this though, I'd need to factor in any other costs which I may need... If I want to shoot Ha when the Moon is out I'd need an Ha filter for instance.

I'd really appreciate it if anyone could answer the following too please...

The colour balance - how easy is processing regarding this as I often see comments about modification affecting the colour balance of images. 

Star colours - I've read about modified cameras being affected by not being able to produce natural star colours.

Regarding ISO, I use my 80D at ISO 200 and because I use ISO 200 I can get 5 and 10 minute subs without overexposing or washing the image out, in a 10 minute sub the peak would be 50 percent on the histogram.. I think with the 600D I would need to use a higher ISO, which I think is probably ISO 800, so I'd need to use a light pollution filter if I wanted to do 5 minute subs?

Regarding calibration frames and darks; I don't take darks with my 80D, I just use dithering and BIAS along with my Lights. Can I do the same with an astro modded camera?

Star bloat - I think I'd need a UV/IR filter with a modified DSLR? What if I wanted to use say a Ha Filter, does this effectively replace the UV/IR filter? Likewise if I wanted to use a filter like the IDAS D2, would that replace the UV/IR filter ?

I know it's a lot of questions but I'd really appreciate any advice on them.

 

 

[Knight of Clear Skies]

A few thoughts.

1 hour ago, smr said:

The colour balance - how easy is processing regarding this as I often see comments about modification affecting the colour balance of images. 

Star colours - I've read about modified cameras being affected by not being able to produce natural star colours.

Sometimes it's a pain, sometimes not. I use DSS to stack and I find it's initial colour balance and levels to be very random at times. Probably has more to do with DSS than whether the camera is modded or not.

1 hour ago, smr said:

Regarding ISO, I use my 80D at ISO 200 and because I use ISO 200 I can get 5 and 10 minute subs without overexposing or washing the image out, in a 10 minute sub the peak would be 50 percent on the histogram.. I think with the 600D I would need to use a higher ISO, which I think is probably ISO 800, so I'd need to use a light pollution filter if I wanted to do 5 minute subs?

I believe ISO 200 is too low for this camera and you'd get better results with shorter subs at a higher ISO. ISO 200 is below unity gain which results in the camera discarding real photons.

1 hour ago, smr said:

Regarding calibration frames and darks; I don't take darks with my 80D, I just use dithering and BIAS along with my Lights. Can I do the same with an astro modded camera?

Yes, no difference. I don't take darks with my DSLR either.

1 hour ago, smr said:

Star bloat - I think I'd need a UV/IR filter with a modified DSLR? What if I wanted to use say a Ha Filter, does this effectively replace the UV/IR filter? Likewise if I wanted to use a filter like the IDAS D2, would that replace the UV/IR filter ?

A UV/IR filter is only required if the camera is 'full spectrum' modified.

1 hour ago, smr said:

Before going ahead with this though, I'd need to factor in any other costs which I may need... If I want to shoot Ha when the Moon is out I'd need an Ha filter for instance.

I'd recommend a clip in Ha filter anyway, even from a truly dark site it greatly helps to isolate nebulosity from the background. But this does require the right software to align the images, which is another cost. I've just bought Registar to do this.

Hope that's some help.

[smr]

Ok thanks very much for your reply. I was under the impression that the UV/IR filter was needed no matter the type of mod, but as I understand it the full spectrum mod is only necessary if you want to take IR photographs in the day time? If so then I wouldn't need that mod, just the filter removing is all as I'd be using the camera solely for deep sky imaging. 

[Knight of Clear Skies]

4 minutes ago, smr said:

Ok thanks very much for your reply. I was under the impression that the UV/IR filter was needed no matter the type of mod, but as I understand it the full spectrum mod is only necessary if you want to take IR photographs in the day time? If so then I wouldn't need that mod, just the filter removing is all as I'd be using the camera solely for deep sky imaging. 

Yes, that's right. Confusion over this is very common.

[smr]

So with just the filter removed star bloat isn't an issue? 

[Knight of Clear Skies]

Sorry, my reply was confusing. DSLRs typically have two IR filters in them and only one is removed for better Ha response. For full spectrum cameras both filters are removed. It's only full spectrum cameras that suffer from UV/IR star bloat, most lenses aren't designed to focus UV and IR light on the same point.

This link explains in a bit more detail, for Canon cameras the LP1 (UV/IR) remains in place.

[david_taurus83]

Get it modified but instead of then buying an Ha filter, you could always buy one of the new duoband filters that are popular with OSC cameras. See below images. The Veil in Ha was shot with an Astronomik 12nm Ha clip in filter in my old 600D. Naturally the image comes out all red when stacked so I split the channels and isolated just the red channel to present a mono image. My processing wasnt great then (it still isnt) and it was shot in warm weather so it's very noisy. Perhaps I pushed the camera too much as I was doing 10 minute subs at ISO800 and got about 10 hours worth.

 

The Heart and Soul image is more recent and shot with my modded 6D with an IDAS NB1 filter which is a duoband filter where it passes both Ha and Oiii(+Hb) at the same time so instead of throwing away both green and blue channels you can process the image as is, kind of like an Ha/Oiii bicolour. Of course it's not as good as mono but you can get an image like this in a shorter time. I believe this was around 6 hours worth of 5 minute subs. Again, processing was a bit, meh..

 

The bottom image is simply RGB, shot with the modded 6D and an IDAS D2 light pollution filter. I think it was about 5 hours worth of 60s subs at ISO1600.

I have to point out though that the 6D is less noisy and has bigger pixels, so more sensitive than the 600D, but below is an idea of what each different filter can do with a modded camera.

 

[Knight of Clear Skies]

On 06/05/2020 at 15:30, david_taurus83 said:

you could always buy one of the new duoband filters that are popular with OSC cameras.

Interesting. A shame this doesn't seem to be available as a clip-in filter.

[david_taurus83]

1 hour ago, Knight of Clear Skies said:

Interesting. A shame this doesn't seem to be available as a clip-in filter.

I agree. Fine if your using a scope as can use a normal 2" filter cell either in the nosepiece or in the reducer etc. but not much choice if you want to use your camera lenses. Astronomik do a comprehensive set of clip filters. The UHC filter looks fairly close to a duoband. Maybe a bit broader bandwidth and no IR cut off at the top but worth a look?

 

Edited May 7, 2020 by david_taurus83