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Gerry Casa Christiana

Halos on Astronomik Ccd clip

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Hello all

I just did a full spectrum mod on my Canon 550d myself! Phew! Anyway I'm using the Astronomik CLS Ccd clip which is not supposed to have halos. I tried last night on the ngc 7000 which was nice to finally see but I noticed red halos around the stars. 

So my question is. 

Do I have to adjust my coma corrector now it's full spectrum (with clear glass mod) and change it by some amount? If so how much. I'm using type iii baader  

Or can it be a problem with the filter from Astronomik? On their site they say they have no issues now from halos. Couldn't be my EOS clip is from a old batch?

Ill try and post a stacked picture later but it's red halos basically. 

Please help guys and girls. 

Thanks

Gerry

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Full spectrum mods need an IR/UV filter otherwise you can get star "bloat" - maybe that's what you are seeing.

Peter

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11 minutes ago, PeterCPC said:

Full spectrum mods need an IR/UV filter otherwise you can get star "bloat" - maybe that's what you are seeing.

Peter

The CLS filter blocks this too:

 

IMG_6734.PNG

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I, too, suggest trying a UV/IR-Filter, and see if that doesn't fix you right up.

In a telescope, you can just screw one filter onto the other filter and attach to scope. Not sure of what your set-up looks like and methodology. But it shouldn't be difficult.

I like the Astronomik CLS-Filter. Just for visual wanderings! Astronomik makes great filters!

Enjoy -

Dave

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1 minute ago, Dave In Vermont said:

I, too, suggest trying a UV/IR-Filter, and see if that doesn't fix you right up.

In a telescope, you can just screw one filter onto the other filter and attach to scope. Not sure of what your set-up looks like and methodology. But it shouldn't be difficult.

I like the Astronomik CLS-Filter. Just for visual wanderings! Astronomik makes great filters!

Enjoy -

Dave

Hi Dave

He's using a clip in filter so he wont have anything to screw onto?  Maybe I'm missing something but why would you block the same thing twice?

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Not sure of the method with those. But I'm saying you want to introduce a filter that will block UV/IR somewhere in the optical-pathway. Perhaps one that can be attached directly in front of the camera-lens?

Dave

Oh I see what you mean. Check the specs from Astronomik - I know they make both filters for visual and imaging. Maybe the CLS is a visual model?

Edited by Dave In Vermont

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4 minutes ago, Dave In Vermont said:

Not sure of the method with those. But I'm saying you want to introduce a filter that will block UV/IR somewhere in the optical-pathway. Perhaps one that can be attached directly in front of the camera-lens?

Dave

Oh I see what you mean. Check the specs from Astronomik - I know they make both filters for visual and imaging. Maybe the CLS is a visual model?

The CLS clip filter goes onto the camera itself, when the lens fits on.  They dont make a visual version of that, plus he says in his opening post its the CCD version :D

Edited by tooth_dr

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Hi all

Yes the CCD Astronomik clip in filter is made for full spectrum so it shouldn't produce halos at all it has a cut off at 700nm so it's doing the same as a Baader filter. 

If I remove the filter then I will for sure have halos as I'll be using full spectrum. 

Im sure there must have been others after doing full spectrum that had the same problem?

Thanks

Gerry

 

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Not entirely sure of the ground here, nor of what you have in the imaging train, but I have found it is quite difficult to get the red and blue at the same focus point, once the Canon IR blocking filter is removed.

One suggestion I've read is to concentrate on focusing the red as sharply as possible (may not be where the Bahtinov says it ought to be) and accept that a slight blue halo may result, the theory apparently being that a blue halo is less intrusive than a red one?

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An image would be useful here as its hard to say without one. What I do know is that I don't get reflections from mine and my 550D full spectrum + MPCC MKIII on a 130PDS.

I can also confirm that so long as its a CLS CCD and not the normal CLS then you will not need an additional UV/IR cut.

Edited by Adam J
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On 28/09/2017 at 13:58, almcl said:

Not entirely sure of the ground here, nor of what you have in the imaging train, but I have found it is quite difficult to get the red and blue at the same focus point, once the Canon IR blocking filter is removed.

One suggestion I've read is to concentrate on focusing the red as sharply as possible (may not be where the Bahtinov says it ought to be) and accept that a slight blue halo may result, the theory apparently being that a blue halo is less intrusive than a red one?

Someone else said that to me. They said aim to get the green focused first then the red. I think I have that in the right order. 

Im just hoping that I haven't put the sensor back as it should. At the moment it's raining so I'm going to have to wait anyway. 

My imaging train is just Dslr coma corrector and Astronomik CLS CCD clip. 

Thanks I'll try what you said. 

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On 29/09/2017 at 18:34, Adam J said:

An image would be useful here as its hard to say without one. What I do know is that I don't get reflections from mine and my 550D full spectrum + MPCC MKIII on a 130PDS.

I can also confirm that so long as its a CLS CCD and not the normal CLS then you will not need an additional UV/IR cut.

I'm getting on my computer now to post a picture since the conversion. I think I'll get a more specific answer if people can see. Give me 30 minutes. Yes my computer is slow! 

Thanks for helping. I do actually need to take a photo without any filters. Maybe it's something else. 

Gerry

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On ‎9‎/‎29‎/‎2017 at 18:34, Adam J said:

An image would be useful here as its hard to say without one. What I do know is that I don't get reflections from mine and my 550D full spectrum + MPCC MKIII on a 130PDS.

I can also confirm that so long as its a CLS CCD and not the normal CLS then you will not need an additional UV/IR cut.

Here is the picture. NG 7000 ISO 400 5 x 20 x 20.TIF

 

NG 7000 ISO 400 5 x 20 x 20.TIF

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Not sure I am seeing any reflections in this image, the extra spike in the stars will most likely be focuser ingress. Can you point out what you think are reflections in the image?

I did a little work on this and converted it to a jpg so no one else has to download a 100mb file ;)

59d133459716b_NG7000ISO4005x20x20.thumb.jpg.dd1be8d612c5fdc943ca73e53098648c.jpg

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35 minutes ago, Adam J said:

Not sure I am seeing any reflections in this image, the extra spike in the stars will most likely be focuser ingress. Can you point out what you think are reflections in the image?

I did a little work on this and converted it to a jpg so no one else has to download a 100mb file ;)

59d133459716b_NG7000ISO4005x20x20.thumb.jpg.dd1be8d612c5fdc943ca73e53098648c.jpg

I think I'll send you all my pictures. I think what it was is because I looked through my camera screen in zoom. Can you see though that the star shapes in the corners are all pointing towards the center. Is this in your opinion the coma corrector spacing that could be incorrect after modification? When I measured from the clear glass up to the outside edge I measured 40mm (but I'm not sure if the measurement needs to be to the sensor?) anyway plus the T2 which is 10mm plus the 2.5mm spacer which makes 52.5mm instead of 55mm. 

Thanks for converting it. I should have done that :) 

Any suggestions would be helpful. 

Thanks

Gerry

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1 minute ago, Gerry Casa Christiana said:

I think I'll send you all my pictures. I think what it was is because I looked through my camera screen in zoom. Can you see though that the star shapes in the corners are all pointing towards the center. Is this in your opinion the coma corrector spacing that could be incorrect after modification? When I measured from the clear glass up to the outside edge I measured 40mm (but I'm not sure if the measurement needs to be to the sensor?) anyway plus the T2 which is 10mm plus the 2.5mm spacer which makes 52.5mm instead of 55mm. 

Thanks for converting it. I should have done that :) 

Any suggestions would be helpful. 

Thanks

Gerry

Well i dont think you have any reflection issues.

You could have an issue with the focuser tube in the light path, you can fix that by either cutting the focus tube to shorten it or by moving the primary mirror up the tube slightly on its adjustment screws which will push the focus further out.

Removing the filter will not change the cc distance too much. I am not convinced that the bottom right has the same amount of coma. Its possible that you need to make a spacer to move the sensor a couple of mm further away from the sensor but I am not totally convinced that you are perfectly colimated here so its worth making sure that is correct before messing with the spacing.

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15 minutes ago, Adam J said:

Well i dont think you have any reflection issues.

You could have an issue with the focuser tube in the light path, you can fix that by either cutting the focus tube to shorten it or by moving the primary mirror up the tube slightly on its adjustment screws which will push the focus further out.

Removing the filter will not change the cc distance too much. I am not convinced that the bottom right has the same amount of coma. Its possible that you need to make a spacer to move the sensor a couple of mm further away from the sensor but I am not totally convinced that you are perfectly colimated here so its worth making sure that is correct before messing with the spacing.

Thanks Adam 

So can the focus tube cause stars like that? Or only collimation? I did check the collimation and it was ALMOST bang on. 

I never used to get stars like that before. I'll definitely move the main mirror first. 

 

Gerry

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no the focus tube is only causing the 5th diffraction spike, as i am sure you know you should only have 4. Normally you will only see that on the brightest stars.

I can only say that from the image the center of the field looks like its towards the bottom right of the image and not the center indicating the collimation being out. One other thing that can cause that is if the camera is not seated correctly on the focuser or sensor tilt or a combination of all three.

I would take a look at the collimation first though then tilt then once that star distortion pattern is perfectly centered on the center of the image you can try adding a spacer between the cc and the t-ring.

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