DrJohnH
member
Reged: 07/27/08
Posts: 35
Loc: West Seattle, Washington
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I'm modifying a Logitech QuickCam Pro 9000 for imaging and was wondering where to put the IR filter: Is it OK to put a 1.25" screw-in filter ahead of it in the 1.25" barrel OR should I try hard to put a small piece of filter glass right over the top of the sensor (well not right on the sensor itself, but just on top of it using the sensor housing to sit the filter on).
The first method is the easiest, while the second would I suspect be better optically, but I'm afraid of messing up the sensor with any out-gas from the adhesive.
Do I need an IR filter at all if I'm imaging the planets and moon?
Thanks -
John
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C130 MAK (Modified)
Astro-Tech Voyager ALT-AZ Mount
Logitech QuickCam Pro 9000
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Chris_H
Carpal Tunnel
Reged: 11/24/03
Posts: 2859
Loc: Norway
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Screw it to the barrel  Webcams are sensitive to IR so yep, you should use one
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Chris
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DrJohnH
member
Reged: 07/27/08
Posts: 35
Loc: West Seattle, Washington
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OK, I suspected I needed the filter, but is it better to put it right in front of the sensor or in the 1.25" barrel?
- John
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C130 MAK (Modified)
Astro-Tech Voyager ALT-AZ Mount
Logitech QuickCam Pro 9000
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clitherowclan
professor emeritus
Reged: 02/23/05
Posts: 527
Loc: Fife Scotland
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For what its worth I use that camera with an Astronomik IR/UV cut filter screwed into the 1.25" barrel front-end. I sometimes, when the seeing is bad, use a narrow-band IR pass filter instead and in the same place. This may not be the absolute ideal place for such a filter but it's a very practical option that works well. 99% of the time you won't improve on it.
Cheers,
Alan C.
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Scottish Astronomer, Firstlight Instruments 10 inch F6.3 Newtonian, Helios 8inch F5 Newtonian and ED80 Apo on driven EQ5. Various cheap cameras.
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DrJohnH
member
Reged: 07/27/08
Posts: 35
Loc: West Seattle, Washington
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Alan -
What adapter did you use to connect to the webcam? I'm going to glue a 1.25" barrel extension to the front of the plastic housing.
John
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C130 MAK (Modified)
Astro-Tech Voyager ALT-AZ Mount
Logitech QuickCam Pro 9000
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clitherowclan
professor emeritus
Reged: 02/23/05
Posts: 527
Loc: Fife Scotland
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OK John, when I ordered the webcam I also ordered the appropriate 1.25" adapter with it. There are a number of companies who make these web-cam telescope adapters so try looking around before you start super-gluing your new camera. With some models you have to separate the two shells that protects the innards and unscrew the original-fit lens assembly. The new adapter has the same screw-thread as the lens assembly and screws back in its place. Now I come to think about it I don't think I even had to open the case of my last webcam (a philips)as the lens assembly could be unscrewed externally. Any way, whichever you need for your particular camera the idea is to replace the original lens with a screw-in 1.25" adapter. Try doing a google search for suppliers that serve your area with these adapters then give them a call specifying your exact camera; they will be able to send the correct adapter. You may find this link useful.
http://webcaddy.com.au/astro/adapter_old.htm
Cheers,
Alan C.
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Scottish Astronomer, Firstlight Instruments 10 inch F6.3 Newtonian, Helios 8inch F5 Newtonian and ED80 Apo on driven EQ5. Various cheap cameras.
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DrJohnH
member
Reged: 07/27/08
Posts: 35
Loc: West Seattle, Washington
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Alan -
I think the camera you have is different than the Pro 9000. The Pro 9000 has no screw-in lens assembly - there's an auto-focus module that is screwed on over the CMOS chip and must be de-soldered to get completely off. See:
http://ghonis2.ho8.com/Pro9000mod.html
There are no stock adapters AFAIK.
Right now the plan is to use a short barrel extension (0.375") and epoxy it to the camera casing, then screw the IR filter into that. Last night I taped a 1.25" barrel from an eyepiece to the lens housing and used it to look a the moon and a few stars - it's apparent that my FOV is too small and I'm going to get a 0.5x reducer to put in front of it as well. The moon looked fine without the IR filter.
Thanks -
John
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C130 MAK (Modified)
Astro-Tech Voyager ALT-AZ Mount
Logitech QuickCam Pro 9000
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clitherowclan
professor emeritus
Reged: 02/23/05
Posts: 527
Loc: Fife Scotland
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Thanks John, I see your problem. I'm sorry but I'm not sure from your posting if you intend to follow the most important step from that link, which is to remove the original lens assembly. You can get results using eyepiece projection with the original in place but it will never match the results attainable with the original lens removed and the bare chip placed at prime focus of the telescope. You should also then find that your field of view is more reasonable; certainly better than most webcams used for astro-imaging because of the relatively large chip used in this camera. At the moment your field of view is rather complicated to determine (at least for me) but I suspect the original lens plus the eyepiece lens will be causing the limited view. Incidentally the original lens assembly will contain a number of colour balance filters including an IR cut filter in order to match the images produced by the chip to something approaching what the eye might see. Your extra screw-in IR filter is only necessary once the original lens assembly has been removed in order to cut the unfocused IR light which would otherwise soften detail in your images. Most people using colour webcams colour-balance in post processing using data from a bare IR (and sometimes UV) protected chip.
Cheers,
Alan C.
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Scottish Astronomer, Firstlight Instruments 10 inch F6.3 Newtonian, Helios 8inch F5 Newtonian and ED80 Apo on driven EQ5. Various cheap cameras.
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DrJohnH
member
Reged: 07/27/08
Posts: 35
Loc: West Seattle, Washington
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The autofocus assembly has been permanently removed and I took the webcam for a spin with my C130 Mak. I temporarily taped a 1.25" barrel from an unused eyepiece to the existing plastic housing (it just so happens that a 1.25" barrel fits just right so that it naturally gets centered over the opening). Like you said, the lens assembly had an IR filter as the last element in front of the sensor. It was cold and I didn't let the scope cool down at all (plus the seeing wasn't all that great), but it worked pretty well on the moon - except for the limited field of view (about 1/4 of the moon was visible). I'll be getting a focal reducer (0.5x) as well as an IR filter.
Overall the project took about an hour to get it disassembled , the lens assembly removed, and up and working again.
- John
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C130 MAK (Modified)
Astro-Tech Voyager ALT-AZ Mount
Logitech QuickCam Pro 9000
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clitherowclan
professor emeritus
Reged: 02/23/05
Posts: 527
Loc: Fife Scotland
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Sounds like you now have a good workable solution. I don't know of many people who use a focal reducer with webcams to increase field of view because of the drop in resolution this causes. You may find you get better wide images by making a mosaic of separate smaller images; this is what most people do. With my own webcam my field of view is significantly narrower than yours due to it's tiny sensor so I do use the mosaic approach; as in this example in which two images are clearly stitched together.
Cheers,
Alan C.
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Scottish Astronomer, Firstlight Instruments 10 inch F6.3 Newtonian, Helios 8inch F5 Newtonian and ED80 Apo on driven EQ5. Various cheap cameras.
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DrJohnH
member
Reged: 07/27/08
Posts: 35
Loc: West Seattle, Washington
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Alan -
One of my main goals is to make it easier for my twin girls to use the telescope - they have a really hard time looking through the eyepieces (they're only 5 yrs old) - plus they want to look at the same time. So I'm trying to get the camera working well enough to view most of the moon and get a good view of the Jupiter/Saturn on my 17" laptop - so a focal reducer is helpful for that (the moon that is).
- John
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C130 MAK (Modified)
Astro-Tech Voyager ALT-AZ Mount
Logitech QuickCam Pro 9000
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clitherowclan
professor emeritus
Reged: 02/23/05
Posts: 527
Loc: Fife Scotland
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Good idea John, hope you have more luck getting your girls interested than I have with my four daughters. In my household even the dog is female!
Best wishes,
Alan.
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Scottish Astronomer, Firstlight Instruments 10 inch F6.3 Newtonian, Helios 8inch F5 Newtonian and ED80 Apo on driven EQ5. Various cheap cameras.
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