Astronomik CLS v CLS-CCD

[dlp]

Having recently bought an Astronomik CLS clip filter for my modded 1000D, I was interested to compare the difference between that and the CCD version. The Astronomik site (rather disingenuously I think) publishes graphs for both on different scales. So I rescaled and overlaid them in PS. It would seem there are slight differences in the visible light range, the CLS having a slightly larger incursion in to green/yellow, but the light pollution and nebula transmission figures overlay exactly. The major difference is that the CLS seems to extend > 700nm in to the IR range whereas the the CCD cuts off completely at 700nm. Unfortunately, they don't publish the data above 700nm so no idea where the CLS cuts off, or if indeed the CCD spikes again. The latter figures are interesting I think - the CCD version is pitched at modded cameras with no IR filter on the basis that the IR cut is 'better' than the camera's original one. However, it looks to me that 100% cut is very aggressive indeed?

The other major difference is that the CCD version claims 100% transmission in the bandpass, whereas the CLS is only about 95% in the VL range, so additional exposure is required, as I have found to my cost. Just pointing my camera at a white LCD screen requires one and two thirds extra stops to compensate.

Anyway, just thought I'd post my findings as of possible interest to others.

David

[dlp]

Would be particularly interested in comments about my interpretation of the IR cut for modded cameras!

[dlp]

Astronomik kindly sent me a link to the extended graph for the CLS-CCD, so here is the graph. Seems it cuts everything above 700nm...

[MartinB]

It is refractors with CCDs (and modded DSLRs I guess) that need the IR block. Reflecting designs are better off without IR block since the IR will also be brought to focus and will contribute to signal. I

[dlp]

Thanks Martin, that makes sense!

I asked the following question at Astronomik :

>I have read that the CLS-CCD is better for cameras that have had their

>IR filter removed. Looking at the transmission graph it looks like the

>filter is blocking the whole IR range, so would I be correct in

>assuming that use of this filter basically puts the camera back into an

>un-modded state spectrum wise?

Reply:

Hello David,

your assumption is absolutely correct! All filters with the addition ''CCD'' have a IR/UV blocking. This add-on is essential for cameras without inbuilt filter.

Best wishes

Oliver

My conclusion (particularly after Martin's comment above) - If you are using a reflector with a modded camera you would probably be best off using the CLS filter, not the CCD version, although the penalty is greater light loss in the VL range.

Other conclusions welcome!!

[NickRose2006]

Good thing I found this thread. I'm in need of a LP filter and I was looking at the two you are talking about. I have a un-modded Canon 300D Rebel, which one would work out better for my camera?

[GrantEb]

This is very interesting. Does this mean that I have the wrong filter?

Modded 1000d, Astronomik CLS CCD Eos clip, SW150PDS reflector?????

[Psychobilly]

If you can afford it I would always go for the CCD variant over the standard one... as it is more useful longer term...

Personally for my LP sources I prefer Hutech IDAS P2's anyday.. but a more costly option...

Billy...

[dlp]

Well, it looks to me that if you use the CCD version on a modded camera, you lose the benefit of modification - the filter blocks all IR. It blocks LP exactly the same as the CLS version. From what I can gather from other comments, it's more useful if you have a straight CCD camera and a refractor, where it stops 'star bloat' caused by IR.

[Psychobilly]

Depend on what scopes you using and if you have any glass elements at all in the imaging train...

If you don't control the UV and IR ends of the spectrum then your asking for trouble...

Unless your looking to do IR Pass the useful part of the mod is the improved Ha response ...

Billy...

[Starblazer]

So let me get this straight, if you are not worried about light pollution reduction and are using a reflector, then you might as well not buy a filter at all as everything will focus at the same point, unlike with refractors?

Reason I ask is that i'm considering modding the 1000d and would rather wait if I do require the filter. If not, then it's something I can make plans to do during the week.

Cheers.

Chris.

[dlp]

That's my understanding of the graphs for the CCD version Chris. The CLS version is I think more appropriate with a Newt/DSLR combination. Quite honestly though I'm thinking of not bothering to use the CLS with mine as it is a heck of an ND filter for an unguided setup. Think I'll just use PI to extract the LP, although that is more destructive to the image, but I will have some images at least.

[Guest]

This is very interesting. Does this mean that I have the wrong filter?

Modded 1000d, Astronomik CLS CCD Eos clip, SW150PDS reflector?????

Yes you have the wrong one, as the canon 1000d has a second filter in camera that is left in place during the mod, it has IR cut, so you only need CLS not CCD version

Stewart

[RAC]

I have both and as long as you leave the anti aliasing filter in you wont notice a difference between them. I would get the cls-ccd if i was to have olny one of them but it doesn't really matter as long as you leave that front filter in when moding the camera. There is no reason to not have a cut off at the top for any of our type of imaging.

Even in a reflector you will get bigger stars if you use a cls filter without the front filter in the camera, its still better to have the cls-ccd.

[Daan]

Is use the following image train: Reflector, Full spectrum modded DSLR (all filters removed) , Coma corrector.

Am i right in concluding that an Astronomik CLS-CCD filter would be a better choice compared to the Astronnomik CLS filter? 

[Gina]

Is use the following image train: Reflector, Full spectrum modded DSLR (all filters removed) , Coma corrector.

Am i right in concluding that an Astronomik CLS-CCD filter would be a better choice compared to the Astronnomik CLS filter? 

Yes - you will need the CCD version to cut out the IR and UV.  With a purely reflective optical system the IR and UV will focus the same as other spectral components but as s oon as you put some glass in this is no longer the case.  I believe the coma corrector will change the focus for these out of band wavelengths.  OTOH I don't know by how much - maybe more of an expert could advise you.

[MartinB]

I think the coma corrector will introduce very little CA.  

[malc-c]

Deleted - wrong thread

[sharkmelley]

Well, it looks to me that if you use the CCD version on a modded camera, you lose the benefit of modification - the filter blocks all IR.

No - the usual reason for modding is to let through the H-alpha (656nm) which Canon's internal filter severely attenuates.  Both versions of the CLS filter pass this wavelength so you are not losing the benefit of modding.  The CCD version cuts out longer wavelength IR.

Mark

[Craigyboy3542]

From reading this post am i correct with thinking the following, i am wanting to mod my 1100D (filters removed as solely using to astrophotraphy) i have a Skywatcher Evostar 80ED DS and will also be using the camera for wide field shots (using standard lens) so the best option for me would be the Clip-Filter (EOS) with ASTRONOMIK CLS??

Sorry i am not that great at understanding all the technical stuff :(  

[malc-c]

From reading this post am i correct with thinking the following, i am wanting to mod my 1100D (filters removed as solely using to astrophotraphy) i have a Skywatcher Evostar 80ED DS and will also be using the camera for wide field shots (using standard lens) so the best option for me would be the Clip-Filter (EOS) with ASTRONOMIK CLS??

Sorry i am not that great at understanding all the technical stuff :(

Basically the Astronomik CLS has no cut off for the IR, so for imaging with a normal DSLR camera or one that has been modified and that still has the rear IT cut filter in place this is fine.  If the camera has been modified by having both the front filter and the rear filters removed, then you need the Astronomik CLS CCD version as this has been made to cut the IR wavelength above H-alpha.

If you use a Astronomik CLS with a fully modded camera you will tend to have out of focus red area's on your images because the camera can not focus the IR due to the longer wave length. - at least that's what I found

[Rico]

I presume, most here are talking about clip filters for their DSLR. Is it possible to buy a regular filter used in CCD imaging, and use some form of adapter on the DSLR to future proof the purchase?

[sharkmelley]

Depending on your adapters, you may well find they are threaded to accept filters.  Alternatively you may be able to include a filter drawer in the optical train.

Mark

[MattJenko]

There is always this : http://www.firstlightoptics.com/adaptors/baader-protective-t-ring-for-canon-eos.html

I have a modded 450d, but it is not the full spectrum and I am getting big halos which I suspect is off the internal ir/uv filter or the replacement filter. I am thinking of removing them all completely and using the Baader with the IR/UV instead.