Another 350d mod!

[butlermike]

Hi, I am just about to mod a canon 350d to remove the IR filter.

i have read a number of threads and other people's experiences doing this but I can't find a reason why I need to put something else in its place.

Can I leave the sensor exposed? What effect will this have on other wavelengths (colours) outside of the red IR spectrum the filter is blocking, if any?

is it correct that the camera won't focus properly without the filter there, or is it that it won't autofocus? That is with a normal camera lens on for wide field astro work. I'm not intended to use the camera for normal photography.

[Freff]

When I converted mine I left out any filters. I'm not sure on the effect on colours other than red of which I was more concerned with.

The sensor is exposed, but should show no ill effects if the camera is always connected to the scope or has the body cap on.

It's correct the camera wont focus properly. It will go through the motions with a lens on and will look in focus TTL.

Unfortunately it wont be. For wide field check focus on camera display or better, a laptop.

[butlermike]

Thanks that good to know.

Why then do people go to the expense of putting a Baader ACF filter back in. There must be a good reason to include it other than being able to use it as a normal camera with custom white balance?

[Freff]

Here is a good explanation from Astronomiser. http://www.astronomiser.co.uk/eosmod.htm

[butlermike]

Many thanks for the link, I must have missed that part of the site or forgotten about it.

However, it looks like the 350d can only have the full spectrum mod and according to the website...

A camera modded thusly would require UV and IR filtering for use with anything other than a parabolic mirror system and would only normally be carried out if the photographer wishes to do either IR photography or spectrographic analysis using a diffraction grating

Does this mean if I hook this up to a refractor I will need to put some sort of filter back in anyway?

I think I might be confusing myself even more...

[Freff]

I'm not sure regarding a refractor, I used my 350D with the MN190 reflector. I supposed the primary on the reflector is a small parabolic. (perhaps not)

I'm not really into the tech side of this. Perhaps someone more knowledgeable will help out, or a bit more research my yield results.

[Freff]

This is a big thread, but very informative. Unfortunately, it's more on double filter cameras rather than the 350D specific. HTH. http://www.cloudynights.com/ubbthreads/showflat.php/Cat/0/Number/5567578/page/0/view/collapsed/sb/5/o/all/fpart/1

[butlermike]

Tony, Thanks for the reply and link.

Do you have any,or know of any, on-line photos that you've taken with the modded 350d with a bare sensor that I can have a look at?

[butlermike]

The link here is written by one of the guys in the discussion in Tony's link above. its obviously a slide show that he must talk over as a presentation due to the lack of detail in it but it is useful.

I think the consensus is that you don't have to replace with a Baader (or another make) filter but using a refractor like this might/does cause the brighter stars to 'bloat'.

http://www.rocklandastronomy.com/NEAIC/talks/Hap_Griffin.pdf

When I mod mine I'll leave the sensor free (with no replacement filter) and see how I get on. I can always get a clip in filter later if the bloating proves to be a problem.

[Freff]

Hap is one of the top lads regarding modding.

I think you have made the right choice having a refractor. You can add a filter if necessary.

[butlermike]

Well I finally got round to removing the filter today...successfully! The camera still takes pictures at least.

i followed the directions from a site called 12 dimensional string in case anyone reading this in the future needs some good clear instructions.

A couple of squeaky bum moments along the way, like a screw that would unscrew so I had to unsolder something else to get a circuit board out!

Putting the ribbon cables back in was DIFFICULT especially with my big clumsy hands.

I haven't used a soldering iron in years, so that was awkward making sure not to slip and crash through a circuit board.

well it's done now...and the beautifully clear evening it was earlier has now clouded over. I hope that's not an omen!

[billhinge]

From what I have read, and I could be wrong and I only comment because I am considering it ... (happy to be corrected)

My understanding (not through experience) is that if you only intend use a camera connected to a telescope then you don't need to use a filter, if you don't, you need to be careful to keep dust out

But if you intend to use a camera for normal photography then you need something, it could be a diy cut filter, a Baader filter or a diy cut quartz window to achieve autofocus but the result will be less good than before?

edit: I'm not specifically thinking Canon only, I'm thinking generically

[butlermike]

I'm just going to be using this for astro so have left the sensor with nothing on. I'll be getting a LP clip in filter to deal with the dust problem though and the LP problem too!

[Luis Campos]

Hello there,

The problem when removing the filter and leave it with the "naked" sensor is that the stars will bloat whit any type of telescope that uses lens in it's optical train, not only refractors but also accesories on newtonians such as coma corrector, barlows, field flatteners, etc...

Lens system usually have a poor IR correction, thay don't focus IR at the same plane as the other wavelengths, so that's why you will have IR bloat on the stars.

You can solve this issue easilly though, just buy a 2" IR/UV filter and screw it on the 2" nose piece or coma corrector or watever you are using and that's it Some LP filter also have integrated IR filtering such as the UHC CCD version, make some reshearch and you will find the best for your application.

Cheers,

Luís

[billhinge]

I often use an astronomiK UV/IR cut filter so I assume naked sensors are OK with that setup ?

[Luis Campos]

I often use an astronomiK UV/IR cut filter so I assume naked sensors are OK with that setup ?

Yes, no problem about that, You can also stack LP filters with that UV/IR cut filter for best results.

Greets,

[billhinge]

Cool, thanks - keeping an eye open for a cosmetically challenged camera on ebay