Modded DSLRs for astro - still an option?

[vanwonky (Dave)]

Just gathering some thoughts about buying a modded DSLR for astrophotography. If the DSLR was to be used just for astro would it be better to get a dedicated CCD camera instead considering the prices have come down considerably over the years? Second hand modded DSLRs are cheaper of course but very hard to come by and then there is the whole cooling thing to consider. What about this option from these guys for a DSLR? I realise a dedicated astro camera will be a fair bit more than this BTW.

Also if modded is still a good option could you please tell me from where you bought (or modded) your camera and if you were pleased with the service and outcome.

I am still looking at scope options as well so am hoping to have enough info by the time I am ready to purchase to 'mate' the two correctly. My brain is hurting

Cheers
Dave

[[1ponders] (Paul)]

Hell yeah. I've only just moved my modded 20D on and only because it was just sitting collecting fungus. If you can get a modded 20, 30 or 40D somewhere for a few hundred dollars then I would suggest grabbing one. I can't vouch for the latest models (60D, I have one but aint modding it) but the previously mentioned models had good reputations. They may not be cooled CCDs but they certainly teach you about the importance of noise/dark frames. Great learning cameras. A genuine 20Da with live view would be fantastic if you could get one. I wouldn't consider a modded X00D or XX00D, noise looks to be a major issue in warmer weather and to be honest I thing pixel size on DSLR are becoming too small for AP. JMHO though.

There are probably many astrocameras around now that have cooling and you can pick up for a few (maybe a bit more than a few) hundred dollars, but what the X0Ds give you is realestate and decent sized pixels.

I bought my modded 20D privately but was originally modded by an IIS member who sold it on and I bought it off that owner. So mine is up to its 4th owner and still going strong!

Would a dedicated cooled astrocamera be better (assuming the same chip/pixel size), yes most likely. But will it be as cheap or as easy to learn to use (big consideration, DSLR we know can work on their own. dedicated CCDs need laptop) debateable.

signed
A long time Canon Devotee When it comes to Astrophotography

[vanwonky (Dave)]

Thanks for the reply Paul. Yes if I could pick up a 20Da that would be awesome. Didn't realise they have 'live view'. Really that is all I want for starters. Of course I have considered the upgraditis factor as well so I have been looking at a few steps above that as well .

[Merlin66 (Ken)]

I have and use a full spectrum modded 1000D.
It's much better than the old 300D I started with, and the Live view is very handy.
Astronomiser in the UK removed both filters for me. Did a great job.
HTH

[vanwonky (Dave)]

Originally Posted by Merlin66

I have and use a full spectrum modded 1000D.
It's much better than the old 300D I started with, and the Live view is very handy.
Astronomiser in the UK removed both filters for me. Did a great job.
HTH

"Also, the full spectrum conversion will allow the entire EM spectrum to be captured for Astrophotography" from the Spencer Camera website

So with your conversion you can still use it for normal daytime and IR photography as well as astro. Do you know if the full spectrum is a disadvantage for astro. They charge $150 extra for the 'H-Alpha Moderate Pass (630-680nm)' conversion. The filter is more expensive I guess.

[Merlin66 (Ken)]

I should explain further....
The newer Canon's have two filters build into them.
The colour compensating filter (#2) and a front (#1) anti-alias/dust filter.
It's usually only #2 filter that is removed to give a "full spectrum" camera mod. This dramatically improves the CCD response to the red region (ie Ha). This #2 filter can be replaced with a clear glass or a Baader UV-IR cut off filter ( 400nm to 700nm)
The claim is made if this filter is removed and NOT replaced that the Auto Focus (AF) is compromised. This is not true.
Also, the addition UV-IR cut filter is NOT required! I found by using the spectroscope that the remaining #1 filter is actually a very good UV-IR cut filter!!! This is never mentioned.

In my case I wanted a FULL, full spectrum coverage (380nm to NIR) for spectroscopy. By removing both the #1 and the #2 filters this can be achieved. Unfortunately by removing these filters, the body can no longer focus standard lenses ( There's 2mm of glass removed from the system). A solution, for EF lenses ONLY, is to add a clear clip in EOS filter (Astronomik MC) - this then allows EF lenses (and my old Zuiko lenses) to focus.

Summary:
Removing #2 filter still allows AF to operate
Removing #2 filter still leaves an effective UV-IR cut off filter
Removing #2 filter significantly improves the red response
Removing #1 & #2 filters gives "FULL, full spectrum" coverage (380nm-NIR)
Removing #1 & #2 filters and adding a clear clip in filter allows the body to focus with EF lenses (or other standard lens)

For "normal" astroimaging, I'd recommend removal of #2 filter.
The attached curves show the response curves of the two filters and clearly shows the UV-IR cut for the #1 filter.
HTH
EDIT: On the Spencer website, they mention the additional removal of the #1 filter - down the bottom of the page....
**** Canon & Nikon SLR users: The Dust Reduction System of some camera models will be removed during the conversion process. Please be sure to disable this function within the settings of your camera. Failure to do so may result in a temporary camera error. If your camera displays a Dust Reduction System error you can still disable the function within the camera menu. ****

[rcheshire (Rowland)]

Also, the addition UV-IR cut filter is NOT required! I found by using the spectroscope that the remaining #1 filter is actually a very good UV-IR cut filter!!! This is never mentioned.

That's interesting.

I understood that a reason for installing a UV/IR filter is to improve focus with straight through optics. Apparently not a problem with refractive/reflective optics.

Would this be true retaining only the low pass filter? The modification would be easier.

[Merlin66 (Ken)]

Yes. The #1 filter does the job of a UV-IR cut filter very well...no additonal UV-IR required.
Having the wavelength cut offs reduces the out of focus chromatic effects (blue and red "bloat") on astro images.
I have to refocus the spectroscope for each area of the spectrum.
HTH

[vanwonky (Dave)]

Thanks HTH. That goes a long way to clearing things up. Unfortunately now by trying to cram that info into my brain I may have forgotten where I live!

[bmitchell82 (Brendan)]

I do have a canon 40d thats a full removal system eg you cannot focus with a normal lense apart from with live view. It uses the UVIR filter cut worked a treat.