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Astrophotography and Sketching >> DSLR & Digital Camera Astro Imaging & Processing

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Hap Griffin
Vendor (Imaging Infinity)
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Reged: 04/15/08

Loc: Sumter, SC
Re: Question about canon modification. new [Re: Hap Griffin]
      #5574215 - 12/16/12 01:59 PM

Mike, your image is a good example of IR star bloating. May I use it in my talks on the subject, of course with credit being given to you?

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Mike C
scholastic sledgehammer


Reged: 03/05/08

Loc: Cornwall, UK
Re: Question about canon modification. new [Re: Hap Griffin]
      #5574582 - 12/16/12 06:10 PM

Justin and Hap, thanks for your responses.

Just to clarify, I did order a modification with Baader replacement from the UK vendor. However, the mod was taking longer than I wanted and a subsequent conversation led to me settling for a straight removal of the main filter, leaving the other in place. I can only assume that this is what was done, as I have not discussed the IR issue with the vendor. I am pleased with the modification overall, and am hopeful that the Baader IR/UV-cut filter I've purchased will solve the IR problem.

Hap, for this reason, although you are welcome to use my Pleiades image to illustrate the problem of IR not being filtered adequately, I'd prefer not to be credited!

Regards,


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Hap Griffin
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Reged: 04/15/08

Loc: Sumter, SC
Re: Question about canon modification. new [Re: Mike C]
      #5574585 - 12/16/12 06:11 PM

I understand. Thanks!

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nofxrx
Vendor (HyperCams & Mods)
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Reged: 07/12/05

Loc: Palm Bay,Florida
Re: Question about canon modification. new [Re: Hap Griffin]
      #5574691 - 12/16/12 07:50 PM

Mike, your image shows a LOT of IR star bloat.
I have never seen an LPF-1 only system show that much star bloat..even on bright stars, like in the HH and Flame FOV...

I dont think something is right here...but that is just imho..

I will be interested to see what happens with the external IR Block..

Hap..dont you think you should figure out exactly what is going on in this guys camera before using it as "proof" that an LPF-1 only system does not reject enough IR???

Also..so are you telling us that LPF-1 and a Baader/AstroDon is 100x better at blocking IR than an LPF-1 only system?
Really? 0.01% vs 0.0001%?
yep. LPF-1 only is absolutely dreadful and no one should use it.

Edited by nofxrx (12/16/12 08:17 PM)


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austin.grant
professor emeritus
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Reged: 10/18/10

Loc: Shreveport, LA
Re: Question about canon modification. new [Re: nofxrx]
      #5574706 - 12/16/12 08:06 PM

Before this gets locked, I'd like to add that that does seem like an extraordinary amount of bloat. My LPF-1 only 1000d never showed any symptoms of star bloat with refractive optics.

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nofxrx
Vendor (HyperCams & Mods)
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Reged: 07/12/05

Loc: Palm Bay,Florida
Re: Question about canon modification. new [Re: austin.grant]
      #5574709 - 12/16/12 08:11 PM

Quote:

Before this gets locked, I'd like to add that that does seem like an extraordinary amount of bloat. My LPF-1 only 1000d never showed any symptoms of star bloat with refractive optics.




I am so glad someone else thought so...I was beginning to think I am crazy..
wait. nope. still crazy

Why would the thread get locked?


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Hap Griffin
Vendor (Imaging Infinity)
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Reged: 04/15/08

Loc: Sumter, SC
Re: Question about canon modification. new [Re: nofxrx]
      #5574728 - 12/16/12 08:29 PM

Brent, when you put two filters in series, each with a transmission of, let's say, 1% at a particular IR wavelength...then, yes, the two together will pass 1% of 1%, which is 100 times more attenuation than through a single filter. Your detailed picture of the stove eye through an LPF#1 only mod on a 1000D shows clearly that a very significant amount of IR gets through it, as does Gary's test with IR LED's.

Filters in series act similarly to RF attenuators in series (for all the hams and RF engineers out there). A 10 dB attenuator drops the power at its input down to 10% of its value at its output. Putting two 10dB attenuators in series gives 20 dB total attenuation of the power, or 1/100th of the input power. In other words, putting two filters in series doesn't just double the attenuation...the equivalent attenuation is the mathematical product of the two attenuations.

As for Mike's image, I can only go on what he says was done to his camera. In any case, it is an obvious demonstration of IR caused star bloating.

Edited by Hap Griffin (12/16/12 08:41 PM)


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Hap Griffin
Vendor (Imaging Infinity)
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Reged: 04/15/08

Loc: Sumter, SC
Re: Question about canon modification. new [Re: Hap Griffin]
      #5574752 - 12/16/12 08:45 PM

The Pleiades (M45) is a great test for both star bloat and reflection halos...it has relatively bright stars which stress the IR attenuation of filters and the anti-reflection coatings. M45 is the target that clearly showed a faulty AR coating on one of my CCD filters once. And the blue stars will expose IR bloat as red (as in Mike's image) since IR shows up mainly in the red channel.

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nofxrx
Vendor (HyperCams & Mods)
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Reged: 07/12/05

Loc: Palm Bay,Florida
Re: Question about canon modification. new [Re: Hap Griffin]
      #5574817 - 12/16/12 09:29 PM

Okay, that makes a lot more sense..seriously.

But, I still do not see that amount of difference in transmission makes images like Mike's...but, I could be wrong.

Again, I go back to the facts that I know, that MANY people who use an LPF-1 only system experience little or NO IR star bloat..


I too have had many issues with reflections on objects like M45..maybe this is also attributing to Mike's issue..?


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Hap Griffin
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Reged: 04/15/08

Loc: Sumter, SC
Re: Question about canon modification. new [Re: nofxrx]
      #5574883 - 12/16/12 10:12 PM

That's why I chose Astrodon LRGB filters for my CCD. Unlike other brands, they do not exhibit reflections on M45 or other bright stars. Looking at images of M45 across the web, you can see that other lines of filters do commonly exhibit reflections. Your reflection problems make me wonder what type of coating the Edmunds clear glass has.

As for star bloat, I'd like to see some examples of LPF-1 only cameras with bright stars in the field. As I said before, you can have a lot of star bloat due to IR leakage, or just a little, depending on the brightness of the star, its IR signature and the amount of IR rejection in the system. Personally, I want to ensure that I have the most IR rejection possible so that I know that I'm not allowing my star images to be any larger than they are naturally.


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Hap Griffin
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Reged: 04/15/08

Loc: Sumter, SC
Re: Question about canon modification. new [Re: Hap Griffin]
      #5574898 - 12/16/12 10:23 PM

Also, you mention that some people experience little star bloat and that the difference of a few percent may not be noticeable. Bare in mind that we're talking about transmission numbers that determine the photons picked up by the sensor and becoming image data prior to contrast stretching. We often use curves and DDP in processing our images that will take an initial few percent difference in brightness in different areas of an image and stretch it into a much larger range so as to make it visible. So even if we only have a few ADU of star bloat in the RAW, by the time we stretch the histogram to a final presentation level, it can become very visible. So the appearance of IR effects is dependent on processing style and extent of histogram stretching.

Edited by Hap Griffin (12/16/12 10:27 PM)


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nofxrx
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Reged: 07/12/05

Loc: Palm Bay,Florida
Re: Question about canon modification. new [Re: Hap Griffin]
      #5575014 - 12/17/12 12:06 AM

Quote:

So even if we only have a few ADU of star bloat in the RAW, by the time we stretch the histogram to a final presentation level, it can become very visible. So the appearance of IR effects is dependent on processing style and extent of histogram stretching.




Actually, this makes a lot of sense to me! Good point


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gdd
scholastic sledgehammer


Reged: 11/23/05

Loc: N Seattle suburb, WA
Re: Question about canon modification. new [Re: Hap Griffin]
      #5575020 - 12/17/12 12:13 AM

Quote:

Also, you mention that some people experience little star bloat and that the difference of a few percent may not be noticeable.




Is it also possible some refractive OTA's are better corrected in the IR than others?

Gale


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mmalik
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Reged: 01/13/12

Loc: USA
Re: Question about canon modification. new [Re: Hap Griffin]
      #5575105 - 12/17/12 02:02 AM

Quote:

As for Mike's image, I can only go on what he says was done to his camera. In any case, it is an obvious demonstration of IR caused star bloating.




Hap, we are talking science and Mike's image is an uncontrolled test and/or for that matter an uncontrolled mod. I am for using empirical evidence before hastening to the point of citing it. To be fair, at this point I don’t think we have countered Brent’s point of replacing LPF-2 with expensive alternatives being wasteful science, if not the money. Regards


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LeCarl
super member


Reged: 03/16/11

Re: Question about canon modification. new [Re: nofxrx]
      #5575107 - 12/17/12 02:05 AM

To nofxrx

I'm totally agree (about the LPF-1) and...
I know, I know, (yes I learn something haha! )
But Primary! just want to keep this simple...
(I have experiences with peoples/material that don't want astrophotography complicated,
perfect sky balance at each shot, this is why we
choose the Happ's astrodon or baader filter, we found that full spectrum with filter is risky,
and mess a lot of nights, time, money... this is why we choose the DSLR...
(full spectrum for a first camera?...)

Just to say to don't forget about the distance for focusing on focusing,
Aboy wants to use his nikons lens with an adapter... full spectrum, (no glass/LPF-1) will not work, focussing distance will not be good


The cost/bill of material is near the same full spectrum or not...
(if done by yourself, because not complicated...)


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Aboy
sage
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Reged: 07/17/12

Loc: Thousand Oaks, CA
Re: Question about canon modification. new [Re: LeCarl]
      #5575270 - 12/17/12 07:18 AM

Quote:

Just to say to don't forget about the distance for focusing on focusing,
Aboy wants to use his nikons lens with an adapter... full spectrum, (no glass/LPF-1) will not work, focussing distance will not be good






Yes. I'll use an adapter.. But up to I know it's possible to use it manual, that is in theory.. But I'll find out in real life soon.

Ps. I am learning a lot with this thread

Edited by Aboy (12/17/12 07:21 AM)


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Hap Griffin
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Reged: 04/15/08

Loc: Sumter, SC
Re: Question about canon modification. new [Re: mmalik]
      #5575506 - 12/17/12 10:45 AM

Quote:

Quote:

As for Mike's image, I can only go on what he says was done to his camera. In any case, it is an obvious demonstration of IR caused star bloating.




Hap, we are talking science and Mike's image is an uncontrolled test and/or for that matter an uncontrolled mod. I am for using empirical evidence before hastening to the point of citing it. To be fair, at this point I don’t think we have countered Brent’s point of replacing LPF-2 with expensive alternatives being wasteful science, if not the money. Regards




Agreed. I'd like to see more images taken with LPF#1 only modified cameras through refractive systems with bright stars in them. As for the money, as I said before, the difference between a clear glass mod and a Baader or Astrodon mod is minimal when compared to the entire cost of the modification and shipping and the value of your imaging time if you find, as Mike did, that you have IR induced star bloat (which is what his image really looks like). Like I stated before, we spend lots of time and money on our scopes, mounts, observatories, travelling to dark sky sites, etc. If we want the absolute most pinpoint star images that our optics are capable of, we need to minimize IR leakage. The stock Canon's have two layers of IR rejection. By removing one of them, you are leaving the camera with less IR rejection than it had in stock condition. Brent's test image of a stove eye that is invisible with both LPF#1 and LPF#2 in place, yet is clearly visible with only LPF#1 in place shows that IR light definitely goes through LPF#1 in amounts sufficent to make a clear photograph. Do you want to have that amount of IR reaching your sensor? It's up to you.

Edited by Hap Griffin (12/17/12 11:01 AM)


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Mike C
scholastic sledgehammer


Reged: 03/05/08

Loc: Cornwall, UK
Re: Question about canon modification. new [Re: Hap Griffin]
      #5575858 - 12/17/12 03:00 PM

Sorry my post was not as informative as I had hoped! I am told that the main filter was to be removed, and not the second (LPF-1 in the terminology used here); however I cannot prove what was done.

Regarding Brent's suggestion that reflections could be partly to blame, I'm hopeful this is not the case. I have imaged the Pleiades with the same 'scope and CLS filter previously, though with a different (and unmodded) camera, with no internal reflection issues.

I'm looking forward to trying out the 2" Baader IR/UV-cut, but alas there is no clear sky on the radar at the moment.

Regards,

Edited by Mike C (12/17/12 03:52 PM)


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mmalik
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Reged: 01/13/12

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Re: Question about canon modification. new [Re: Mike C]
      #5576262 - 12/17/12 07:19 PM

Quote:

I am told that the main filter was to be removed, and not the second (LPF-1 in the terminology used here)




Mike, sorry, but you are repeating the ambiguity most of us are trying to avoid. There is no such thing as "main filter" and your sentence is confusing at best as to which one was removed, LPF-1 or LPF-2?

Please confirm with a statement, e.g., “LPF-2 was removed, although you are doubtful”. Thx


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Hap Griffin
Vendor (Imaging Infinity)
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Reged: 04/15/08

Loc: Sumter, SC
Re: Question about canon modification. [Re: mmalik]
      #5576299 - 12/17/12 07:47 PM

One way to tell if LPF#1 is installed is to see if the camera is doing a dust cleaning when you turn it off. If it is and isn't throwing an error code, then LPF#1 is probably in place. If the "front filter", otherwise known as LPF#1, is not in place and the camera is set to do automatic dust cleanings, it should generate an error code ( I know it does with some models).

You can tell if LPF#2 has been removed by setting the automatic white balance to daylight and shooting a JPEG of an outdoor scene. If the overall tint is reddish, then LPF#2 is missing.

Mike, please do these tests and let us know the outcomes and we will have a better idea of the actual status of your camera.

Edited by Hap Griffin (12/17/12 08:06 PM)


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