300D before and after modding comparison

[Chris]

I've followed a number of threads in the past where poeple have modded DSLR's and I've always thought I wouldn't mind giving it a go for myself. I already own a pre modded Canon 350D so rather than actually needing a modded camera I'm doing it more as a personal challenge and hopefully I'll learn a thing or two on the way:).

Well talking about learning, I've learn't since winning a bid on a 300D that if you do a full filter removal mod you may get a degree of chromatic abberation type star bloating when you use the camera with a refractor. This is because removing the IR cut filter allows all IR light to pass through to the chip not just Ha, and lenses don't bring IR light into focus at the same point as visible light, or something like that:D

Because after I've finished playing around with modding I will be selling the camera (probably very cheaply) I became a bit concerned that I would be limited to selling it to someone with a reflector because mirrors are not effected by the above problem, either that or I would have to buy a Baader replacement filter to make it work well with any scope although this would cost about as much as the camera again!

I decided to ask on the forum if anyone knew how much of an ACTUAL problem this starbloating was with fracs? The replies pointed towards it being a big problem with achromatic refractors but less of a problem with Apo's, so I basically thought it would be interesting to do a little experiment as I'm going along with this mod to see exactly how much of a problem it is with Apo?

I plan on taking some shots before and after modding using my little WO66 Apo refractor so as to help quantify how bad any starbloating is? I hope this will both add to knowledge and help me decide if its really worth bunging in a Baader filter or not (the benefits of daytime use aside).

I decided to make Pleiades M45 a target as its positioned nicely at the moment, theres plenty of stars of varying magnitudes to examine, and I can find it easily as I don't have Goto:D

I will try and reduce uncertainty as much as possible by keeping things the same before and after the mod, e.g. number and length of exposures, camera settings, and to keep things simple I'll do all the processing in DSS making a note of the settings used.

This is my before modding pic although I think my flat frames were a bit rubbish, well infact I know they were, but never mind as long as they are the same before and after modding. Also I've got the worst LP ever since our new neighbours moved in and insist on having all their 100W lights on all night without any curtains, they've been in a couple of months now so whats with the no curtains? Anyway, this is my way of excusing the gradient on the image below:D

20 x 90seconds at ISO 800 with 5 darks and flats, ambient temp 6C. Processed in DSS settings recorded on a piece of paper somewhere.

[alan potts]

To me it looks very nice and has not taken a massive time exposure to get some nebular showing, well done.

Alan.

[Beulah]

Good work - we seem to be living in a parallel universe with regards to neighbours. Same story here!

[Chris]

To me it looks very nice and has not taken a massive time exposure to get some nebular showing, well done.

Alan.

Thanks Alan:) I'm quite pleased that some Merope nebulosity is showing through considering I couldn't really stretch the image without the gradient going wild:D, still it will do as a control image to check for star bloating after modding my camera:)

[Chris]

Good work - we seem to be living in a parallel universe with regards to neighbours. Same story here!

Thanks Beulah:) I agree they probably haven't a clue that its even a problem for me, I'd ask him nicely if he could perhaps turn the odd light off late at night but I sense that I shouldn't go there. I don't need a torch for setting up at least:D I've been building an obsy at the bottom of my garden for the last 6 months, maybe I can add a big light polution blocking sail to it or something:D

[Chris]

I've just finished modding my camera and I'm pleased to say that all the settings and everything look to be working nicely, I look forward to testing it out with some astro work! Well, I definately got the challenge I was after, lots and lots of fiddly bits that require you to have microscopes for eyes, the last ribbon cable in particular was a nightmare to get back in, I think that one alone took me about an hour! In total it took me a good 6 hours, slow and steady wins the race:). I feel a bit tense and wired now, not ideal at 2am:D

[samtheeagle]

Heh heh Grats! I don't think I'd have the nerve to mod a camera myself...

[Chris]

Thanks Sam:), you had the nerve to build an obsy so I reckon you'd have the nerve to mod a camera:) You definately need good eyes and steady hands though:D

[Chris]

Its clear out at the moment so I'm out collecting data on M45 with the modded 300D, 20x90 sec subs ISO 800. I know this isn't the usual first target for a modded cam as theres no Ha but hopefully I'll be able to answer the above question. M42 will be well placed soon so hopefully then I'll put the camera through its paces either on my Apo or my Newt depending on what I find out:)

[heathenwoods]

Great idea for a thread - good luck with the results.

[Chris]

Well these are the visual results before and after modding to see how much removing the IR filter effects star bloating when used with an Apo refractor, same amount of data for both pics, plus roughly the same settings in post processing, I think I had better flats the second time around but still LP gradient to contend with.

Putting the light pollution gradient to one side can anyone see any extra star bloating on the right hand image when compared to the left? I don't have a great eye for detail and it will help me answer this the hypothesis.

[Chris]

My opinion on the results are that using a full spectrum modded camera with an Apo refractor doesn't increase star bloating by a noticable amount. I think the stars are brighter on the pre modded image and I think this is down to differences in processing i.e. how much the image was stretched, I don't think I stretched the post modding image as much because the mod is showing more LP perhaps due to the increased sensitivity across the spectrum, therefore I stretched it less to try and keep the LP under control which I have clearly failed to do:D

[Chris]

Thanks very much Andrew:) I'm pleased with the results so far, however I would really like peoples opinions on the before and after images to help solidify a conclusion.

[Chris]

I'm think that before I go around recommending full spectrum modded cameras for both Newts and Apo fracs I should reprocess both sets of data this time with exactly the same settings like I'd originally planned before losing the piece of paper with my setting written down:D, I can't be absolutely certain of the result until I've used a better scientific method.

[Chris]

ok here are both sets of data pre and post modding with exactly the same processing.

I used the same darks and flats on both images ambient temp was pretty much the same at around 6C. All processing was performed in DSS with the following settings: Lum: 0, 100, 8, 26, 0, 74.6. Saturation 24% and RGB was alligned at the same distance from the left hand edge of the curve. Both images were then imported into PS just for the purposes of cropping and saving as Jpeg.

I can't really see a significant difference in the size and tightness of the stars between the two images, I cannot see any halos around the brighter stars on the image taken with the camera after IR filter removal. I conclude that you don't particularly need to replace the IR filter with a Baader style filter in order to use these modded cameras with Apo refractors, just removing the IR filter making the camera full spectrum results in stars that are not so different to the ones obtained prior to modding.

[Chris]

Edit: I should probably comment on the focus before and after modding:) A Bahtinov mask was used both times in order to obtained equidistant diffraction spikes, although I can just make out a slight black dot in the centre of some of the stars of the modded image therefore if anything I could be underestimating the results as slightly better focus might have been achieved creating tighter stars.

[Gina]

That's a good comparison Chris Clearly shows that there are no ill effects. Now if you take a similar pair with Ha in the image... oh... you can't you've done the mod I guess I could though - I have an unmodded 1100D (Rebel T3). At least I may be able to when we get a clear night... hmmm...

[Chris]

Thanks Gina:) I'm quite surprised by the results after hearing so much about the need to use a replacement IR cut filter with a refractor. I was expecting the quality of the stars to go down hill by some degree, but as we both can see this simply isn't the case:) Really good news for people wishing to mod the older single filter Canons as its a win win situation regardless of whether you use Mirrors or lenses, still good stars but vastly better Ha sensitivity!

Like you say, I was intending on a before and after Ha test using M42, although I was so itching to play with my new soldering iron and do the mod it kind of went out the window:D Still if it still hasn't sold by the time we get a good night which is not on a work night, I might still get to do the after Ha test:) I remember Mark doing a before and after test on the Rosette with is 350D and the difference was quite profound!

edit: now you mention it a before and after with the 1100D would be very interesting wouldn't it, you'll have to add that one to your long list of projects:D

[Chris]

I thought I might combine both sets of data: although I'm fairly sure I both clipped and over saturated it in order to bring out the Merope nebulosity and reduce the LP, I need to take some processing lessions:D

[SplintUK]

Having recently picked up a "filter removed" modded 300d myself, but being unable to get out due to the clouds or events (mainly clouds) I couldn't resist having a play with your image on my photoshop. Using GradientXterminator with 2 simple passes (as described here) http://www.rc-astro....r/tutorial.html I turned your "after" image to this...

It only took a couple of minutes and did what I think is a really good job. Off the back of that I've turned my trial license to a full one on GradientXTerminator

If you happen to be plagued by vignetting and gradients, and want a quick fix inside photoshop, it was quick, easy and at £30 worth the cash for me - so I thought I would share ;-)

[Chris]

Thats amazing! thanks so much Splint:) what a great tool! like you say well worth the 30 quid, I'll be looking into it myself. In the mean time feel free to run it over my combined data image if you feel like it:D

edit: oh yes thanks for the link and I hope you get the chance to use your 300D soon, its a nice solid easy to use camera in my opinion, enjoy:)

[Gina]

Interesting Must give GradientXterminator a go myself - seems a reasonable price if it works well Thanks