Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Jun 2, 2014 10:32:48 GMT
Dear all,
I am new to observing meteors with video cameras. I have settled to use a Watec 1/2" camera. I would now need a lens. However, I have no knowledge on which lens to use. Some people say a "fast lens" is best. I can imagine that the field of view should be as large as possible to maximise the probability to catch a meteor. My plan is to setup a double-station system and then use UFOCapture and UFOOrbit to record and analyse the meteor event (hopefully caught by the two cams). Can anyone help me to advise me which lens to use and possibly let me know where to buy it? The lens problem is the biggest problem at the moment. Once I solve it I think its a matter of weeks to start observing. Hope anybody can help me.
|
|
|
Post by davy on Jun 2, 2014 10:35:48 GMT
Welcome to the forum. .carl should be along shortly to keep you on track..mccavity also is into this field of astronomy. .davy
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Jun 2, 2014 11:01:06 GMT
Hi and welcome. You will be having the same problem that I have. 1/2" C mount lenses are not so common as 1/3" CS mount lenses, and the choice is quite limited. I have several 1/2" cams and would also like to find a good lens for allsky. There is this one. Cheap enough to try, but no idea what the FOV would be. From what I have learned, a 4mm lens gives about 90degree FOV. rfconcepts.co.uk/lens-c-4mm.htmlThere are companies who do still sell 1/2" format lenses but are very expensive. I have tried a Canon lens at 18mm and it just about gets Ursa Major in the frame so not really wide enough, and wider dslr lenses get expensive. I have settled on using a 1/3" chip for allsky, but am still on the lookout for a wide fast 1/2" lens.
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Jun 2, 2014 12:33:28 GMT
Hi AllanUk,
thank you for your quick reply. Very helpful. Now I know that certain lenses (for example 1/3" format) only fits certain detectors (1/3" CCDs). That is useful to know. I have some follow-up questions: What is the difference between 1/2" and 1/3" in the imaging sensor? Is 1/2" better than 1/3"? Maybe a dumb question: What will happen if I put a 1/3" lens on a 1/2" camera? I mean the camera sensor is larger than the intended filter format, then the image should still fit, right? But maybe there is some optical problem coming into the picture?
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Jun 2, 2014 12:58:21 GMT
Hi AllanUk, thank you for your quick reply. Very helpful. Now I know that certain lenses (for example 1/3" format) only fits certain detectors (1/3" CCDs). That is useful to know. I have some follow-up questions: What is the difference between 1/2" and 1/3" in the imaging sensor? Is 1/2" better than 1/3"? Maybe a dumb question: What will happen if I put a 1/3" lens on a 1/2" camera? I mean the camera sensor is larger than the intended filter format, then the image should still fit, right? But maybe there is some optical problem coming into the picture? For those new to this type of "C/CS" mount Surveillance Video camera's, here are some basic facts you need to know. In the early days of this type of C mount video camera, 1/2" detectors were superior to 1/3" detectors. Over time this has changed with 1/3" detectors being equal to or superior in some cases, so slowly many 1/2" detectors are used in top end spec scientific/medical cameras because 1/3" detectors and lenses are so much cheaper to manufacture. This has resulted in many excellent 1/2" lenses no longer being made, such as some of the very fast F/0.8 Computar's that I have in a wide range of focal lengths, bought many years ago and prefer over the cheaper 1/3" lenses. The distance from the front flange on the camera with a 1/2" detector is 17.5mm, so lenses called "C" mount are designed with a back focal length to suit this distance of 17.5mm. The distance from the front camera flange with a 1/3" detector is 12.5mm and lenses designated "CS" have this back focal distance 12.5mm. My professional quality C/CS mount video Camera's (Sony, Panasonic) etc.have adjustable detectors to allow the detector to be moved forward or backwards to use either type of lens, depending on the FOV required This means in reality that a 1/3" CS lens will not come to focus on a 1/2" "C" CCD-not enough back focal distance. However, a 1/2" lens with a 17.5mm back focus distance will work on a 1/3" CD camera 12.5mm by the addition of the 5mm spacer (making up the 17.5mm distance) often supplied with C/CS mount video cameras. The C/CS thread is the same on all such cameras and lenses 1" x 32 TPI. The "C" designation comes from Cine camera days and the lens threads are the same. Hope this answers a few questions and helps prevent folks from buying mis-matching camera/lens combination. This link will show you some of what I have talked about: picasaweb.google.com/109921669020426367250/VideoAstronomy?authuser=0&feat=directlinkClear skies, Shevill
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Jun 2, 2014 14:07:16 GMT
Yep as Shevill has pointed out you cant put a 1/3" lens on a 1/2" sensor but you can put a 1/2" lens on a 1/3" sensor. Here is also a link to show the difference between what the different sensor sizes see, www.2mcctv.com/blog/2012_07_18-cctv-lens-guide-choosing-a-security-camera-lens/As Allan has said 1/2" lenses are more expensive and becoming harder to get. Depending on what way you are mounting the cams will effect what lens you may need. If the cams are in CCTV housings then around 2 - 4 mm maybe fine. When you go to 2mm or less then it maybe better suited to pointing straight up as in allsky as it will see as a fish eye. Basically you will want widest FOV to cover as much sky as possible. UFOCapture is an excellent program, I have used it myself. Hope this helps.
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Jun 2, 2014 22:48:48 GMT
Be careful when considering using a very wide angle lens with ufoanalyser software. I gather that the distortion inherent in ultra wide angle lens can lead to unreliable mapping of a meteors exact track across that sky and thus unreliable orbital data. Many meteor videographers use 3.8mm to 12mm lenses.
Sent from my XT1032 using Tapatalk
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Jun 4, 2014 6:44:10 GMT
To Astrotasmania, michaelmorris and carl: thank you for your feedback. Very valuable information. Especially regarding wide angle lens and UFO software. This is what I am fearing so I think I will go for a little more narrower lens. By the way: field of view can be calculated as follows: If sensor size is 6.5mm (H) and 4.6mm (V) and the focal length of the lens is, say 6mm, then the horizontal field of view in degrees is = 2 x arctan(3.25/6) x (180/pi) = 56.9 degrees. Same formula applies to vertical field of view calculation. The 3.25mm comes from half the sensor size (not sure why exactly).
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Jun 4, 2014 8:04:12 GMT
Dear all, I am new to observing meteors with video cameras. I have settled to use a Watec 1/2" camera. I would now need a lens. However, I have no knowledge on which lens to use. Some people say a "fast lens" is best. I can imagine that the field of view should be as large as possible to maximise the probability to catch a meteor. My plan is to setup a double-station system and then use UFOCapture and UFOOrbit to record and analyse the meteor event (hopefully caught by the two cams). Can anyone help me to advise me which lens to use and possibly let me know where to buy it? The lens problem is the biggest problem at the moment. Once I solve it I think its a matter of weeks to start observing. Hope anybody can help me. Hi, It will help a little if you have read my recent posts of cameras and lenses to give you basic info to enable you to know what to look for. What is the distance from the detector to the front flange of your Watec? what model Watec is it? If the distance is not more than 12.5 mm then you can use a CS 1/3" lens. Keep in mind that the wider angle lens you use the smaller/shorter the meteor trail will be on the image and if near the horizon will be somewhat distorted too. A $10 lens is a $10 lens so do not expect anything fantastic. The wider the lens get the more depressing the fine detail gets, even with my expensive Fujinon & Computar f/0.8 and f/1.2 1/2" lenses. I am contemplating going from a 185 -degree FOV Fujinon lens 1.4mm f/1.4 CS lens to a Computar 2.8mm f/0.8, I will lose some FOV but get larger images (not down to the horizon) and better detail as a payoff. Remember all 35mm camera lenses are in effect telephoto lenses on a ting 1/2"-1/3" CCD unless it is an 8mm fisheye lens. When I get some time i will try my 8mm fisheye lens on one of my 1/2" C mount cameras so see what the quality is like. The problem there is that at f3.5 it is a slow lens. There are NO free lunches in optics/photography, there is always a trade-off/compromise somewhere in the chain. I have no experience with cheap lenses, the cheapest I ever bought was at least $350. the dearest was $7.5K I have no experience in capturing meteors with video but am setting up one of my all video sky camera's to give it a shot. I made a couple of housing for two of my DSLR's over the summer to use 8mm fisheye lenses and automatic interval exposures through the night. Winter weather has not allowed this yet. Clear skies, Shevill-"Down Under"
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Jun 9, 2014 7:17:41 GMT
Hi Shevill, thank you for your feedback. To answer your question: Can I ask you to point your browser to the following URL: www.wateccameras.com/Then mouse-over: "products" Then click: "cameras" Then click: "mono" Then click: "902 H2 Supreme" Then you find links to PDF files with technical specs of the camera including a drawing with dimensions. I have a hard time to find exactly what you are looking for and hope you can read off the numbers. Looking forward to hearing from you. Another issue: I have asked the question whether a C-lens can fit to a CS-mount camera to an US based optics online store. Their reply was the following: ################### This is true. There is a difference between the C-mount and the CS-mount. Although they are designed the same and a "C" will fit on a "CS" and vice versa, they are a slightly different lengths. So if you put a C-mount lens on a CS camera you can crush the sensor and destroy the camera. You can correct this via an adapter, but why purchase an adapter if you can get a lens that fits directly on the camera? Also, using an adapter would not allow the use of the "Auto" features like Auto-iris or Auto-focus. ################### Is it true what the "expert" is saying above? Best wishes, Tobias
|
|
|
Post by Dragon Man on Jun 9, 2014 8:00:08 GMT
Yes Tobias, because a C mount lens has a slightly longer threaded section, and screwing it in without an adaptor can force the longer threaded section straight into the sensor.
These are the lengths of the threaded sections:
C mount - 17.5mm
CS mount - 12.5mm
The 5mm adaptor stops the threaded section from crushing the Sensor.
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Jun 9, 2014 8:24:08 GMT
Yes Tobias, because a C mount lens has a slightly longer threaded section, and screwing it in without an adaptor can force the longer threaded section straight into the sensor. These are the lengths of the threaded sections: C mount - 17.5mm CS mount - 12.5mm The 5mm adaptor stops the threaded section from crushing the Sensor. Hi, I think there may be a little confusion here, if I can explain. Lenses can be divided into C-Mount Lens and CS-Mount Lens. They can be Manual or Auto Iris (DC & Video driven-with or without peak adjustment controls of the lenses) C-Mount Lens
The flange back (distance from the surface where the lens comes in contact with the camera to the focal point) of C-Mount lens is 17.526mm (0.69 inch). This is the only difference between the C-Mount lens and CS-Mount lens. C-Mount lens, as well as CS-Mount, is 1 inch diameter with 32 TPI (threads per inch). A C-Ring (5mm spacer ring) is required when a C-Mount lens is to be mounted to a CS-Mount camera unless the camera has built-in Flange-back Adjusting Ring. CS-Mount Lens
The flange back of CS-Mount lens is 12.5mm (0.492 inch). This is 5mm shorter than the C-Mount lens and you need a 5mm spacer ring (or, C-ring) when you mount a C-Mount lens to a CS-Mount camera. (So, CS-Mount camera is always compatible with C- or CS-Mount lens. But, C-Mount camera is not compatible with CS-Mount lens. Most professional cameras are C/CS-Mount cameras and include a 5 mm spacer ring or they have the means to actually move the detector closer the front of the camera. Some modern high end cameras do this adjustment electronically. picasaweb.google.com/lh/photo/BGhzIZkgiiG1xuPNGwJXINMTjNZETYmyPJy0liipFm0?feat=directlinkAlso: picasaweb.google.com/lh/photo/YFV6SFtZEUOfHEt4f7e6AtMTjNZETYmyPJy0liipFm0?feat=directlink I posted all this info just recently in a post on Camera's & C/CS Lenses Basic Facts. picasaweb.google.com/109921669020426367250/VideoAstronomy?authuser=0&feat=directlinkClear skies, Shevill Hopes this helps.
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Jun 9, 2014 8:38:08 GMT
Hi Shevill, thank you for your feedback. To answer your question: Can I ask you to point your browser to the following URL: www.wateccameras.com/Then mouse-over: "products" Then click: "cameras" Then click: "mono" Then click: "902 H2 Supreme" Then you find links to PDF files with technical specs of the camera including a drawing with dimensions. I have a hard time to find exactly what you are looking for and hope you can read off the numbers. Looking forward to hearing from you. Another issue: I have asked the question whether a C-lens can fit to a CS-mount camera to an US based optics online store. Their reply was the following: ################### This is true. There is a difference between the C-mount and the CS-mount. Although they are designed the same and a "C" will fit on a "CS" and vice versa, they are a slightly different lengths. ((So if you put a C-mount lens on a CS camera you can crush the sensor and destroy the camera )). INCORRECT. The threads are the same length on all C/CS video lenses, please read my posts from last week on selecting camera types & lenses.You can correct this via an adapter, but why purchase an adapter if you can get a lens that fits directly on the camera? Also, using an adapter would not allow the use of the "Auto" features like Auto-iris or Auto-focus. INCORRECT. The adaptor is only the bring the back focal distance to the right position when using a 1/3" CS lens on a 1/2" CCD camera, and has NO effect on using an auto iris lens. ###################Is it true what the "expert" is saying above? I am familiar with all those lenses, I have more lenses & cameras in my store than I should have, here are just a few. picasaweb.google.com/109921669020426367250/VideoAstronomy?authuser=0&feat=directlinkI have also just posted an answer to a question via Dragon Man (Ken)Clear skies... ShevillBest wishes, Tobias
|
|
|
Post by Dragon Man on Jun 9, 2014 8:45:30 GMT
You are absolutely correct Shevill. My apologies Tobias. I have always mistaken the Flange Back as the Threaded length because I have a C mount that does hit the sensor if I don't use the spacer, because it is longer in the threaded section. Here's an image showing what Shevill has described:
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Jun 9, 2014 8:49:14 GMT
Dear all, I am new to observing meteors with video cameras. I have settled to use a Watec 1/2" camera. I would now need a lens. However, I have no knowledge on which lens to use. Some people say a "fast lens" is best. I can imagine that the field of view should be as large as possible to maximise the probability to catch a meteor. My plan is to setup a double-station system and then use UFOCapture and UFOOrbit to record and analyse the meteor event (hopefully caught by the two cams). Can anyone help me to advise me which lens to use and possibly let me know where to buy it? The lens problem is the biggest problem at the moment. Once I solve it I think its a matter of weeks to start observing. Hope anybody can help me. Hi Astrotoby,
Yes, a fast lens is very desirable, however, the fast lenses made by Computar the 2.6mm f/1.0, the 6mm f/0.8 and 12mm f/0.8 ( which I bought many years ago, are no longer made) They stopped production around 2007.
You may be lucky and find one second hand but I think they will be far & few between, they were expensive lenses back then. A 'fast lens these days is usually f/1.2, f/1.4 and start at around 2.6mm. A 2.1 is nice which I have but not in auto iris unfortunately.
I will add some more images of 1/2" & 1/3" video lenses to my Video Astro album, then you will see a physical size difference, thus the expense. Any top quality Auto Iris Computar, Fujinon, Pentax video lenses are not exactly cheap either, certainly the 1/3" lenses are a lot cheaper.
The other reason for the fast lens is so that the camera can run at its normal video speed, non integrating, otherwise you do not get an actual meteor trail but a series of broken dots or lines.
Clear skies, Shevill
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Jun 9, 2014 8:54:08 GMT
You are absolutely correct Shevill. My apologies Tobias. I have always mistaken the Flange Back as the Threaded length because I have a C mount that does hit the sensor if I don't use the spacer, because it is longer in the threaded section. Here's an image showing what Shevill has described: Hi Ken,
Thanks for posting the pic, I see I should unearth some of my video books which have all these images in, a picture is worth a thousand words. There certainly is a lot of confusion out there about video C/CS camera & lenses, many bog standard shop assistants don't know the difference either if it is a second hand store etc.
Clear Skies... Shevill
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Jun 10, 2014 4:36:25 GMT
Hi Ken & Shevill,
your feedback is absolutely fantastic, competent and to the point (however, Shevill your last link brings me to a bunch of images, there is no real text to read. Maybe a wrong link?).
However, I got a much better idea about the mounts and their differences. The WATEC camera I am having my eye on has a CS mount. So, C (with spacer) or CS mount lenses will do just fine according to your feedback. I have many other questions, but for now let me ask the following question: What is the maximum length of a 1) BNC cable and 2) S-video or 3) composite-video cable from the back of the camera to the computer (in between there will be a video converter)? In my case the distance between the cams and the computer will be around 50m. Is that still OK? Here I am thinking of that the longer the cable the larger the resistance and hence the signal might deteriorate. Maybe the cameras are build such that a maximum length is allowed? If that is the case which of the specification parameters of the camera should I look out for? Any feedback/advise/watchouts about the maximum length is welcomed. Also, I noticed that the old WATEC cameras have BNC outputs, while the new WATEC cameras only have S- or composite video outputs. Is S-/Composite better than BNC cable?
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Jun 10, 2014 5:28:02 GMT
Hi Ken & Shevill, your feedback is absolutely fantastic, competent and to the point (however, Shevill your last link brings me to a bunch of images, there is no real text to read. Maybe a wrong link?). However, I got a much better idea about the mounts and their differences. The WATEC camera I am having my eye on has a CS mount. So, C (with spacer) or CS mount lenses will do just fine according to your feedback. I have many other questions, but for now let me ask the following question: What is the maximum length of a 1) BNC cable and 2) S-video or 3) composite-video cable from the back of the camera to the computer (in between there will be a video converter)? In my case the distance between the cams and the computer will be around 50m. Is that still OK? Here I am thinking of that the longer the cable the larger the resistance and hence the signal might deteriorate. Maybe the cameras are build such that a maximum length is allowed? If that is the case which of the specification parameters of the camera should I look out for? Any feedback/advise/watchouts about the maximum length is welcomed. Also, I noticed that the old WATEC cameras have BNC outputs, while the new WATEC cameras only have S- or composite video outputs. Is S-/Composite better than BNC cable? Hi Astroboy, If you click on each image there is a description about each image. I never just post images without all relevant information, no point in posting the images otherwise, as some folks often do.
If it is a B&W camera, composite cable (good quality if running 50m.) If colour,Y/C 4-pin mini DIN is better as the luminence and colour are on separate lines, so less interference. No point if a B&W camera. Also Y/C (S-Video) will not run those sorts of distances without losing quality if it will go 50m?
Yes, you will need an image grabber/converter between camera and computer, again a cheap one will not produce top results. An Imaging Source converter costs about $350 and takes both Y/C & Composite. Composite out comes in either BNC and RCA connectors. BNC is the industry standard, RCA is more the standard on domestic gear.
Keep in mind, with any electronic gear, cables, connectors, adapters, cameras, lenses etc. cheap is cheap with often less than hoped for results, so do not expect a Rolls Royce ride from a Mini, even though they both do the same job. I understand that for most people, this is a hobby, so cost is always the main factor in most cases. I am lucky in that having once had a scientific/medical imaging business, apart from being a med lab scientist in pathology, and 5 years additional tertiary study in this type of imaging, most of my gear came at trade price from professional suppliers, and I can see the difference in the image quality. In fact I often tested camera' s on stars and dark skies to assess its quality. Over the years, many astronomical suppliers sent me camera's, lenses & telescopes to test & review, which often I got to keep as payment-nice.
Hope this helps.
Please check my photo links to confirm there is a description under each photograph, thanks.
Clear skies... Shevill
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Jun 11, 2014 3:54:31 GMT
Hi Shevill, your feedback is all informative and very useful. I am following up on your last question to check your link (picasaweb.google.com/109921669020426367250/VideoAstronomy?authuser=0&feat=directlink). Attached to this post I add a screendump that shows your link. But there is little informative text. Only a few lines at the top-right corner. There is no "post on Camera's & C/CS Lenses Basic Facts." to my knowledge. Maybe I am missing something?
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Jun 11, 2014 6:12:53 GMT
Hi Shevill, your feedback is all informative and very useful. I am following up on your last question to check your link (picasaweb.google.com/109921669020426367250/VideoAstronomy?authuser=0&feat=directlink). Attached to this post I add a screendump that shows your link. But there is little informative text. Only a few lines at the top-right corner. There is no "post on Camera's & C/CS Lenses Basic Facts." to my knowledge. Maybe I am missing something? Hi Toby,
Something strange with the links, I click on a link it takes me to an album and I can go through each image with its details underneath each one.
picasaweb.google.com/109921669020426367250/VideoAstronomy?authuser=0&feat=directlink
So I will post this and see what happens when I read this as a recent post.
Also search for this, I think I posted it in three different places:
"Basic facts about "C/CS" Video Camera's & Lenses"
Clear skies... Shevill
|
|