Modify eos 40d or not?

[chouet]

I'm still a relative novice astrophotographer, but now have an obsy up and running. I've been using my eos 40d for deep sky (apt software) and am unsure whether to:

- modify the filter

- buy a 2nd hand eos body and modify that

- save the pennies for a good, cooled ccd camera

The 40d is used for general photography too and while I'm no David Bailey, I don't want to be disappointed with normal daylight photos on a modded camera.

Apart from the odd hot pixel, the 40d performs really well on long exposures with no amp glow at all - I wouldn't want to get a 2nd eos which didn't perform as well.

[brantuk]

Save for the ccd unless you need it now and on a tight budget or something. In which case get another dslr (possibly pre-mod'ed). Pretty subjective really and all down to personal criteria

Try astronomiser for good reliable mod'ed dslr's.

Edited May 14, 2011 by brantuk

[AndyUK]

Hi Chouet,

I was in the same position as you (I think) last December - a 40D, only DSLR in the house, lots of lenses kit to go with it etc. It was a VERY tough decision to have it modded, but I did eventually send it off to astronomiser to have the filter replaced at the cost of c. £200. I was really keen to get the red end of the spectrum...!

I have since used it for "terrestrial" use (using custom white balance to remove the now-pink colour cast on normal photos) and you really wouldn't know the difference. So it can be used very well for both [NOTE: If you didn't want to use CWB, then I see that Astronomik also sell an EOS clip filter to "revert" it back...]

I certainly agree with you about the performance of the 40D - it does indeed perform really well on long exposures with no amp glow, but when the weather started improving I found the exif temps had risen to 20C(+) on 10 minute exposures, and the noise / banding that started creeping in got really quite frustrating, even though I was using bias / dark frames etc. I know there's potentially ways around it (take more subs, dithering etc), but I finally took the plunge to save up for (and have since bought, but not got to grips with) a setpoint cooled CCD.

As the one I chose has a 285 chip, I still anticipate possibly using the DSLR for larger DSO's and certainly for widefield (lens only) shots. As Brantuk has said though, this is a bit of a subjective / personal decision and cash probably comes into it somewhere - I know I wouldn't have got "permission" to buy another DSLR for astro use only and then permission later on to buy a CCD, so that really made my mind up. Although I've had great fun with the DSLR (and learnt a lot!), I wanted (want) to get into narrow band imaging, and for that I deemed that I'd need a setpoint cooled CCD, not another DSLR...

(I'm not sure that helps...?)

[samir_ansari]

Hey Andy, did your terrestial photos really look the same with just a CWB? I would have thought you would get flat photos with no shadows because of the IR being let in?

[MjrTom]

Hello,

I am in a similar boat to you, just really considering the conversion of my second camera body which is a 40D.

I prefer to do very widefield imaging using my astrotrac and lenses upto 300mm.

However the main issue I have as well is Ha response.

The stock filter on the 40D is pretty poor, only about 25% of the total gets past the filter.

From what I have gathered the 40D makes a very good astro camera.

Suppose its time to send it off to astronomiser

[AndyUK]

Hi Samir - Yes... Well, I couldn't see any difference - There were certainly no apparent IR "artefacts" in the shadows that I could see. Obviously I can't take a "before / after" shot now, but I can try and take a pic of something with a "hot" shadow in it if you like (with CWB)?

@MjrTom - From my experience the modded 40D works very well - As I noted in my post above, the only real issue I've found is that when using longer exposures (ie 10mins) at higher ambient temps, the noise becomes evident... All my images to date have been taken with the 40D and EOS clip filter (gallery) - Mainly prime focus but I've also used it with a 180m/f3.5...

[samir_ansari]

Hi Andy, it would be great to see a shot you took with a harsh shadow as I too am considering modding my 450D.

[AndyUK]

Hi Samir - I'm not sure that this is such a good test, but it gives a comparison between a Custom WB (left) and an Auto WB (right) with my 40D (filter replaced). (If you can suggest a better test, please let me know and I'll have another go...)

[Beyond_Vision]

Hey Andy, did your terrestial photos really look the same with just a CWB? I would have thought you would get flat photos with no shadows because of the IR being let in?

This will depend on if you have the filter replaced or removed altogether. The replacement filter will have a UV/IR cut.

Regards

Kevin

[AndyUK]

Hi Samir - For further info on camera modding, have a look on the Astronomiser website. I chose to pay the extra £50 to have my filter replaced primarily to retain autofocus...

[samir_ansari]

Ah ha, I believe I was mistaken. I forgot that the baader conversion filter is just a steeper cut off to UV rather than letting it all in.

Thanks so much for those photos Andy, I can see its just a colour difference with the mod which isn't a problem as I normally shot all my photos in RAW anyway.

This will depend on if you have the filter replaced or removed altogether. The replacement filter will have a UV/IR cut.

Regards

Kevin

[AndyUK]

No problem Samir - I always shoot mine in RAW too...

[Merlin66]

Guys,

You should be aware that even when the "filter" is removed the dust shaker filter left behind acts as a UV-IR cut filter.

I have done some tests with a stock 450D and a "full spectrum modded" 1000D and the spectroscope definately shows the cut-off.

So, if you mod a camera you definately don't need an additional UV-IR filter.

[AndyUK]

Hi Merlin - But what about if wishing to maintain autofocus on the camera? The Astronomiser website states that if you wish to retain this, you really need to have a filter replacement...(?)

(If not, I spent £50 I needn't have!)

[MjrTom]

Hiya,

According to the astronomiser website AF is still retained.

Astronomiser - Automated Astronomy and AstroImaging Solutions

Also info regarding UV/IR cutoff available via this link.

It all depends upon if you have one of the newer EOS bodies with dual filters it would seem.

[Merlin66]

Good question!

In the older models pre 450D the filter removed was 3mm thick and this caused a shift of almost 1mm in the focus. I could not get a standard lens to focus on a 300D with the filter removed.

On the new cameras the filter is only 0.8mm thick so when it's not there the focus point will only change by less than 0.3mm.

If anyone has a "filter removed" mod they can confirm AF still works.

(My 1000D was claimed by the seller to be "filter removed" - I can focus very well with the AF - but I don't know of anyway of confirming the filter has actually gone -other than stripping the camera - which I don't want to do. I was hoping that the spectroscope tests would show an extended coverage out into the NIR but this was not the case!)

[AndyUK]

I just re-read Andy's statement on Autofocus:

A majority of people who have their cameras modified for astronomy only use them for this purpose, so retaining the autofocus is not important as focussing is done manually either through a lens or telescope, so removing the rear filter is generally the better option for these people when modifying a dual filter camera. As it is, the filter that is removed is only 0.8mm thick so the difference in the focus point when considering the refractive index of glass vs the refractive index of air is very slight. In practice, this means that the difference is practically unnoticeable when taking everyday snaps. When using very 'fast' lenses or ones with a very short focal length, i.e., for macros and fish-eye shots, this slight mis-focus becomes more noticeable.

I guess it depends on how much you're willing to accept "practically unnoticeable" ... It would indeed be interesting to hear from someone who's had a dual filter camera modded with a filter removal to see what they say about using it for "terrestrial" use...

[MjrTom]

Yeah I agree "practically unnoticeable" is a bit vague

[Merlin66]

I asked my wife (the extreme tester!!) to take some shots around the garden with the 450D and then with the modded 1000D (CWB set)

When I mixed and presented the results she couldn't tell the difference. Colour and focus - close-ups and wide were very acceptable.

So I'd have to say that the majority (ie family) won't notice any problem.

[AndyUK]

Cheers Merlin (that was quick!)

[MjrTom]

Yes thanks for the info!

I really do need to get my act in gear and send the 40D off for modification...

[samir_ansari]

Has anyone here attempted it themselves? After looking at a couple of guides on how to do it, it seems quite straight forward.

[AndyUK]

Not me, that's for sure. I can't spell DIY and it looked way to complicated for me, especially as It's my only dslr. Still, I know that some do / have done this mod themselves, so if you're confident at taking it on, then you'll save yourself 150.00!

[Psychobilly]

Your camera your choice .. only you can decide.. I have done my own cams... I always follow the Gary Honis guides...

Edited May 17, 2011 by Psychobilly

[Antique Restorer]

Hi guys, Being on a tight budget I have just bought a 40D to use for starting out in Astro photography, and was horrified when reading a different forum that there were a lot of negative comments about the 40D for this use, I was wondering if I had bought a bit of a "pup", however your comments here have reassured me somewhat, thanks, I am now thinking that perhaps they were just "gear snobs" as I have to admit the 40D is starting to show it's age, I am as I said only starting out so the whole removal of components thing is a little way off yet for me, but thanks for not being negative about the camera...lol