I'm not going to the SPSP, I should have been better organized eh? Next year I hope! Have a great weekend, capture those photons and post the results I'm veeeery close to getting a 40d of my own.
Get it Rob, the 40D is a killer. Ive played with several DSLRs and CCDs. The features and software that come with it cant be beat, SO much more connvienient to use than previous DSLRs, a real pleasure to use. And the spec is impressive.
Maybe next year for the SPSP then (you could have seen a 40D in operation, doh).
Eric. as here for the 350D (the 40D would be similar) the green and blue channels are unaffected by filters, they both pass through (the removal of filters is just to extend red response) red and green colours are presnt in both moded and unmoded versions (so images are still RGB). What makes the colour balance so strange with no filter is the over all extra red sensitivity and big green and smaller blue response spikes at 7000 (and another blue spike at 8200), which causes red, green and blue all to accept IR light as extra data at 7000 and beyond, causeing a washed out effect way out side normal balance. The huge red curve gives the overall red hue with something like 3 times ( more than GB) the light collection over a large frequency range.
The UV/IR blocker cuts out the 7000 and above spikes and returns colour balance with just a slightly extended red response to just before 7000. Green and blue response is then back to normal as in an unmodded cam. This is what you want for astro RGB, normal GB and a bit higher red respose to capture Ha.
Totally agree with you. I wouldn't want the red to be overly exposed but slightly more than GB which is why the UV/IR filter works best.
The 350D filter is different from the 40D filter because the 40D has 2 filters which makes things more complicated.
I have ordered a Hutech Daylight front filter should be coming shortly. Will test with this on. I don't have a UV/IR filter so i can't test with this filter but my IDAS LPS2 filter blocks the UV/IR range that is why with it infront of my lense, it looks more normal.
will keep you updated when the daylight filter arrives. im hoping soon
Yes, good, I think, in the end, iether Ive stuffed up my mod, or you dont have the shaker filter (causing the over-red hue due to the spike at 1100). Iether way, you definitly have the optimal situation really, so theres no need for concern (for you, for me, well I might have), you can use the IDAS LPS2 filter for astro, and the daylight filter for terestial and no filters for IR. I will test my 40D mod at the SPSP (the rig is packed away now).
I note tho, that OPT recommend a UV/IR filter for use with the IDAS LPS2 filter, you may still be bothered with the 1100 spike. It will be interesting to see our respective imaging results.
Yes, good, I think, in the end, iether Ive stuffed up my mod, or you dont have the shaker filter (causing the over-red hue due to the spike at 1100). Iether way, you definitly have the optimal situation really, so theres no need for concern (for you, for me, well I might have), you can use the IDAS LPS2 filter for astro, and the daylight filter for terestial and no filters for IR. I will test my 40D mod at the SPSP (the rig is packed away now).
I note tho, that OPT recommend a UV/IR filter for use with the IDAS LPS2 filter, you may still be bothered with the 1100 spike. It will be interesting to see our respective imaging results.
The shaker on my 40d still works. Bobby only removed the phaser filter and replaced it with the BCF filter (see his tutorial). Ive tested the shaker manual, auto etc even get that buzzing sound coming out of it. i don't know but definitely both our 40d's are different. what firmware is yours? im using the latest v1.0.5
LOL totally agree. I think both our 40d's are correct though but it just that my has a BCF filter that is why it turns out different. goto bobby's website, he posted some astro pics taken from the cam.
The only other person i know who has a modded 40D is Steve (Skwinty) on IIS.
Sheesh Steve, thats a bit of a tease . No comprehensive pic description.
But, going by the pic file names, the 2nd pic is a CWB, well that looks normal, fits my understanding that CWB compensates any colour (filter) imbalance to create a normal pic, AND the 3rd pic is an AWB, see the green grass Eric, similar to my pic, what do make of that !.
Hi Fred
Sorry for the tease but i thought the file names were a big clue as you found.
My filter is hutech 1b.Attached is a pic of keyhole total of 75 sec exposure.15 by 5 sec summed at 400 iso.
I couldnt imagine what the pic would look like if the filter didnt cut off at about 700nm.
OK Steve, nice pic, but its all red (although the stars are white), so cant tell in detail much of the filter drama from that (I dont doubt your mod BTW). Anyway Eric, the only other explanation, as you say, is that the shaker filter reponse has humps/goes up after 700nm and the alows the BCF 1100 bump through. Let the image test begin ;-).
OK Steve, nice pic, but its all red (although the stars are white
Hi Fred
Isnt that the reason for the modded filter? To allow the Ha wavelength of 656nm through and show the red.
Thats my interpretation, but then I am a noob!
Good luck in resolving your filter issue and have a great weekend. Hope to see some stunning images from you next week.
Yes Steve, but its the response of filters after the initial wanted cutoff that maybe of issue here. I wasnt critising your pic, it looks fine, its just I cant judge filter response from your red pic (other than white stars, which is a good indicator).
Hi Fred
Any criticism is welcome as I have loads to learn. Perhaps I didnt understand what you were saying. If it will help I will make a copy of the Hutech supplied graph and post that for you.
A question however, If the filter blocks from a specific wavelength upwards, then how can any filter down stream of the optical chain have an effect other than attenuation of the initial passband?
Or am suffering from the ready fire aim syndrome?
Eric, the 1st pic is a 40D with a hutec fiter, the 2nd a 350D with no filter at all, no comparison, bit random . AND, are you going to the SPSP?.
Steve, yes a low pass filter with a flat nil response after the wanted frequency is ideal in this case and would negate futher other filter responses, but some filters have bumps after that, this is the area of doubt in this thread.
. Ill have a go tommorrow at the SPSP. You going Rob?, and Eric?.
Next year I hope! Have a great weekend, capture those photons and post the results 
I'm veeeery close to getting a 40d of my own.
. Take some astro pics Eric, and I will, then we will proceed 
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