Flat frame after Canon filter mod?

[rcheshire]

Hi.

I have just finished modifying my 1000D. Replacing the factory filter with an Astrodon Inside filter bought from Hap Griffin.

Following Gary Honis' instructions was straight forward enough - getting the job done without too much trouble.

I took a few quick flats. One of which is posted below. It is quite different to previous flats taken with this camera because of the new filter. But to me it looks a bit odd. Could it be representative of the filter coating?

I've added a grey scale (oops inverted) of the same flat for comparison - which looks OK to me.

Many thanks

Rowland.

[bmitchell82]

is the camera attached to the scope?

[rcheshire]

It is. 200mm lens

[leon]

I'm not so concerned about the flat, however there is quite some dust in between the filter and the sensor, did you give it a good air blow before assembling it.

Leon

[bmitchell82]

I guess i don't have the overall experience, but my 40D never looked like that. it was nice and round (on my scope) with a good gradient moving out

[rcheshire]

I did give it a good air blow and spent a lot of time inspecting it closely. I'm not so concerned with the big round motes as I am with the overall appearance. I was very particular with each surface - sensor, filter and low pass.

[bmitchell82]

you know what it reminds me of, when you clean something and there is residue left on it because i wouldn't have expected that type of abberation to appear from addition of a UV IR plate.

[leon]

Rowland just to add another thought, did you face the pinkish side of the filter that you replaced facing outward, and not into the sensor.

Leon

[rcheshire]

Hi Brendan and Leon. I pulled it all down and with a jewelers glass and see smearing and dust. Minute - well I am starting again.

I have the red facing out - I got that bit right.

Thanks again.

[bmitchell82]

ahhh crafty little beggar! CCD and CMOS sensors are soooo damn sensitive. before I sorted my pelican case out with rechargeable dessicant canisters i had a little bit of issue with frost forming on the slip cover of the CCD, you could see it creeping on the images, quite disturbing really liquid slopping around in amoungst the electronics:eyepop:

[leon]

Rowland, you can take this advise or leave it.
The filter you are replacing is not a touchy as made out to be, and can be cleaned up with a good lens pen, and a dry air blower, not that canned crap, never use it.
A Giotto air blower is the best.
Don't be afraid of it mate, hold the edges of the filter just before placing it into position and give it a gently wipe with the lens pen, one strok at a time alone the lenght of the filter, dont worry about the side that will be facing out yet, you can do that later.
Give the sensor a quick blow only, and sandwich them together.
The lens pen will not scratch the filter at all, I have replaced 3 filters on the Canon 5D's with success, and still clean the filter when necessary with a good quality lens pen.
I have seen the results of the Canon Service Centre after a clean and they come back worse after there supposed cleaning.
Anyway as I said don't take this advice if you are not sure, or game.

Leon

[rcheshire]

Thanks Leon. They are pretty tough filters by the look of it. This one has taken a bit of a bashing, but I managed to clean it as you suggested.

I think the big mistake I made, after fixing the new filter into its frame, was leaving it overnight for the silicon to cure. It was the devils own job to remove the dust that then accumulated.

Getting the new filter in place as soon as possible is the trick, and once in place and the most important surfaces protected, add a drop of silicon at the corners of the new filter and leave it to cure. Cleaning the top surface of the filter is much easier than the bottom with the seal in the way.

That little seal behind the factory filter is a pain to handle if it comes off as mine did.

I have some smear free cleaner, so dust removal is easy with a slightly damp micro fibre cloth followed up by the lens pen and blower.

Should have it finished tomorrow. Not that it matters, as clear nights are few and far between at the moment in Geelong.

[leon]

Have a look at this link this is how i did my Canon 5D, I know it is not the same as your camera but may give you a couple of tips.

Leon :thumbsup:



http://www.lifepixel.com/tutorials/infrared-diy-tutorials/canon-5d

[rcheshire]

Thanks Leon. Hope to have better results tomorrow.

[rcheshire]

Huge improvement. Stripped it down and started again. Surprising how much microscopic contamination is left behind by microfibre cloths. I washed the lot thoroughly and used isopropyl alcohol as a cleaning agent. No smears and no dust... except the inevitable accumulation on the face of the low pass filter. Alcohol seems to act as a mild anti static agent.

Thanks Leon for your advice.

[bmitchell82]

Now thats what i would have expected! Well done on the resolution of the issue :)

[leon]

Well that is certainly a hell of an improvement, well done.

Leon

[rcheshire]

Thanks guys. The next one should be a breeze. Learned a lot from this experience. For anyone tackling this mod, proper cleaning method is the key.