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ASTRO: Question on STL filter wheel
The filter wheel in my STL camera has suddenly decided to position the
lum filter at random. Never exactly the same spot but never too far off. Result is a flat fielded image that makes the donuts look 3D in the final picture. Each time I go back to the lum filter it is positioned just slightly differently. Though a couple times it was more than 2 degrees off. The other filter positions line up fine, just the lum filter that is screwy. Since I'm using a SCT I suppose I could take it out without much if any harm but I'd like to get this stabilized. Any ideas? Rick -- Correct domain name is arvig and it is net not com. Prefix is correct. Third character is a zero rather than a capital "Oh". |
#2
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ASTRO: Question on STL filter wheel
that seems odd Rick
the old CFW7/a had a friction drive wherein a rubber ring surrounded the outside of the carousel to make a compliant and high friction drive point which was pressed against a shaft of a motor as I recall I've not been inside an STL except once and can't remember if they did it the same way or not. Can you confirm the drive mechanism? If it is that way then possibly the friction isn't what it once was when the weather is truly cold or perhaps the friction on the bearings increases in the cold. It seems odd though that it only happens with the lum filter other than usually lum shows up these defects better than the other filters, are you sure that it isn't happening on the other filters too but they are just a bit too dense optically to show up as well on the image? if it truly is confined to the Lum filter then I would suspect it is moving inside the pocket of the filter wheel. I once had mine rattling around and experienced the same issue you described but it affected all of the filters free to rattle around. So I shimmed them by using a twist tie cut short and inserted as a bushing between the outside edge of the filter and the filter pocket in the carousel. that's how i keep mine from moving around "Rick Johnson" wrote in message ... The filter wheel in my STL camera has suddenly decided to position the lum filter at random. Never exactly the same spot but never too far off. Result is a flat fielded image that makes the donuts look 3D in the final picture. Each time I go back to the lum filter it is positioned just slightly differently. Though a couple times it was more than 2 degrees off. The other filter positions line up fine, just the lum filter that is screwy. Since I'm using a SCT I suppose I could take it out without much if any harm but I'd like to get this stabilized. Any ideas? Rick -- Correct domain name is arvig and it is net not com. Prefix is correct. Third character is a zero rather than a capital "Oh". |
#3
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ASTRO: Question on STL filter wheel
Yes it uses the same mechanism. I overlaid individual flat frames each
taken after rotating to other filters then back to lum and I'd have to rotate one by up to 2 degrees to get them to line up but the center of rotation had to be where the center of the wheel would be, well "above" the flat. Did the same with the other filter positions but they all line up fine. A couple times the lum frame stopped half way between filters so I had half lum and half something else. Can't recall which color is next to it other than my Halpha and it wasn't that one as at that exposure time it would have been nearly black. Next time it would be about but not exactly in position. I suspect cold is the problem. It was near zero (-17.5C per the uncooled camera) when the problem first showed. Today at 10F it was doing the same however but only about 1 degree off max. I suspect that rubber ring is slippery right at some point at this temp. I'll take it apart and see what I find. I could just remove it I suppose as I doubt the corrector in the scope would defocus IR to any significant extent. Monday I'll call SBIG and see what they have to say. I don't know how it senses where it is at but it gets the others right no matter which direction I rotate it. Last night I only got a couple quick test frames before the power went out. Some major sub station let go in the cold blacking out many square miles and two small towns. It came back on after many hours allowing me to lower the scope without having to disengage the worms but it went out again so I had to release the roof motor and close it by hand. Rolls very easily but a bit messy taking the chain off, not to mention cold. By morning it was snowing. First good seeing in months. I obviously angered some weather god. A day after a deep front goes through often leads to very steady seeing up here. Rick Richard Crisp wrote: that seems odd Rick the old CFW7/a had a friction drive wherein a rubber ring surrounded the outside of the carousel to make a compliant and high friction drive point which was pressed against a shaft of a motor as I recall I've not been inside an STL except once and can't remember if they did it the same way or not. Can you confirm the drive mechanism? If it is that way then possibly the friction isn't what it once was when the weather is truly cold or perhaps the friction on the bearings increases in the cold. It seems odd though that it only happens with the lum filter other than usually lum shows up these defects better than the other filters, are you sure that it isn't happening on the other filters too but they are just a bit too dense optically to show up as well on the image? if it truly is confined to the Lum filter then I would suspect it is moving inside the pocket of the filter wheel. I once had mine rattling around and experienced the same issue you described but it affected all of the filters free to rattle around. So I shimmed them by using a twist tie cut short and inserted as a bushing between the outside edge of the filter and the filter pocket in the carousel. that's how i keep mine from moving around "Rick Johnson" wrote in message ... The filter wheel in my STL camera has suddenly decided to position the lum filter at random. Never exactly the same spot but never too far off. Result is a flat fielded image that makes the donuts look 3D in the final picture. Each time I go back to the lum filter it is positioned just slightly differently. Though a couple times it was more than 2 degrees off. The other filter positions line up fine, just the lum filter that is screwy. Since I'm using a SCT I suppose I could take it out without much if any harm but I'd like to get this stabilized. Any ideas? Rick -- Correct domain name is arvig and it is net not com. Prefix is correct. Third character is a zero rather than a capital "Oh". -- Correct domain name is arvig and it is net not com. Prefix is correct. Third character is a zero rather than a capital "Oh". |
#4
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ASTRO: Question on STL filter wheel
"Rick Johnson" wrote in message ... Yes it uses the same mechanism. I overlaid individual flat frames each taken after rotating to other filters then back to lum and I'd have to rotate one by up to 2 degrees to get them to line up but the center of rotation had to be where the center of the wheel would be, well "above" the flat. Did the same with the other filter positions but they all line up fine. A couple times the lum frame stopped half way between filters so I had half lum and half something else. Can't recall which color is next to it other than my Halpha and it wasn't that one as at that exposure time it would have been nearly black. Next time it would be about but not exactly in position. I suspect cold is the problem. It was near zero (-17.5C per the uncooled camera) when the problem first showed. Today at 10F it was doing the same however but only about 1 degree off max. I suspect that rubber ring is slippery right at some point at this temp. I'll take it apart and see what I find. I could just remove it I suppose as I doubt the corrector in the scope would defocus IR to any significant extent. Monday I'll call SBIG and see what they have to say. Now you are starting to see some of the reasons why I just patently reject anything that SBIG mades after about 2003 or so. There's no excuse for putting light sources in filter wheels which they did with the CFW7/a and using those goofy friction drives is just being cheap when you can use a toothed drive that never slips in my opinion as a long time design engineer. There's no end to the things I can point out that I think are just bad design decisions in that STL you have but I will hold back for another day. It still amazes me that they have the following they do. The only rational explanation that I can see is that most people just buy what they see others doing. I've seen the same thing out deep sea fishing: one boat stops, then another comes in close thinking they are catching fish. Then that attracts a third and a fourth and a fifth and next thing you have 20 boats in the same spot and no one is necessarily catching fish, but it is easier to stop where you see the boats than it is to think for yourself. Be honest Rick, why did you pick the STL versus all the other choices? Was it because you see a lot of them in use or was it based on careful analysis of all the relevant parameters that are important for your imaging interests? |
#5
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ASTRO: Question on STL filter wheel
It was the only used camera covering the FOV of the scope that was at a
price I could afford. Bought it from a guy local for about half cost with the filters thrown in. The FLI 6303 with filters would have cost twice and had less field. It was my first choice but never saw a used one I could afford. I can get a friction band that will hold up in cold so shouldn't be hard to fix. I know several engineers in the aero-space industry. It's amazing what they can scrounge up. I sort of like such challenges. Compared to what it took to get a fraction of the results I'm getting now when I started in the late 50's with astro photography this is really simple stuff if you ignore image processing. The jury rigged stuff we used back then would blow your mind. No such thing as off axis guiders. You built nearly everything from what you could find in military surplus shops. Optics too often came from there. And if you adjust for inflation the cost of what you did put together was much much higher for a fraction the result. I'd get bored if it were too easy. My main challenge now is learning all the various ins and outs of processing the data. Mechanics of telescopes are easy for me but software -- that's very foreign to me. Rick Richard Crisp wrote: "Rick Johnson" wrote in message ... Yes it uses the same mechanism. I overlaid individual flat frames each taken after rotating to other filters then back to lum and I'd have to rotate one by up to 2 degrees to get them to line up but the center of rotation had to be where the center of the wheel would be, well "above" the flat. Did the same with the other filter positions but they all line up fine. A couple times the lum frame stopped half way between filters so I had half lum and half something else. Can't recall which color is next to it other than my Halpha and it wasn't that one as at that exposure time it would have been nearly black. Next time it would be about but not exactly in position. I suspect cold is the problem. It was near zero (-17.5C per the uncooled camera) when the problem first showed. Today at 10F it was doing the same however but only about 1 degree off max. I suspect that rubber ring is slippery right at some point at this temp. I'll take it apart and see what I find. I could just remove it I suppose as I doubt the corrector in the scope would defocus IR to any significant extent. Monday I'll call SBIG and see what they have to say. Now you are starting to see some of the reasons why I just patently reject anything that SBIG mades after about 2003 or so. There's no excuse for putting light sources in filter wheels which they did with the CFW7/a and using those goofy friction drives is just being cheap when you can use a toothed drive that never slips in my opinion as a long time design engineer. There's no end to the things I can point out that I think are just bad design decisions in that STL you have but I will hold back for another day. It still amazes me that they have the following they do. The only rational explanation that I can see is that most people just buy what they see others doing. I've seen the same thing out deep sea fishing: one boat stops, then another comes in close thinking they are catching fish. Then that attracts a third and a fourth and a fifth and next thing you have 20 boats in the same spot and no one is necessarily catching fish, but it is easier to stop where you see the boats than it is to think for yourself. Be honest Rick, why did you pick the STL versus all the other choices? Was it because you see a lot of them in use or was it based on careful analysis of all the relevant parameters that are important for your imaging interests? -- Correct domain name is arvig and it is net not com. Prefix is correct. Third character is a zero rather than a capital "Oh". |
#6
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ASTRO: Question on STL filter wheel
i bet the lum filter is what is used the most and so you have a 'dent' in
the band... "Rick Johnson" wrote in message ... It was the only used camera covering the FOV of the scope that was at a price I could afford. Bought it from a guy local for about half cost with the filters thrown in. The FLI 6303 with filters would have cost twice and had less field. It was my first choice but never saw a used one I could afford. I can get a friction band that will hold up in cold so shouldn't be hard to fix. I know several engineers in the aero-space industry. It's amazing what they can scrounge up. I sort of like such challenges. Compared to what it took to get a fraction of the results I'm getting now when I started in the late 50's with astro photography this is really simple stuff if you ignore image processing. The jury rigged stuff we used back then would blow your mind. No such thing as off axis guiders. You built nearly everything from what you could find in military surplus shops. Optics too often came from there. And if you adjust for inflation the cost of what you did put together was much much higher for a fraction the result. I'd get bored if it were too easy. My main challenge now is learning all the various ins and outs of processing the data. Mechanics of telescopes are easy for me but software -- that's very foreign to me. Rick Richard Crisp wrote: "Rick Johnson" wrote in message ... Yes it uses the same mechanism. I overlaid individual flat frames each taken after rotating to other filters then back to lum and I'd have to rotate one by up to 2 degrees to get them to line up but the center of rotation had to be where the center of the wheel would be, well "above" the flat. Did the same with the other filter positions but they all line up fine. A couple times the lum frame stopped half way between filters so I had half lum and half something else. Can't recall which color is next to it other than my Halpha and it wasn't that one as at that exposure time it would have been nearly black. Next time it would be about but not exactly in position. I suspect cold is the problem. It was near zero (-17.5C per the uncooled camera) when the problem first showed. Today at 10F it was doing the same however but only about 1 degree off max. I suspect that rubber ring is slippery right at some point at this temp. I'll take it apart and see what I find. I could just remove it I suppose as I doubt the corrector in the scope would defocus IR to any significant extent. Monday I'll call SBIG and see what they have to say. Now you are starting to see some of the reasons why I just patently reject anything that SBIG mades after about 2003 or so. There's no excuse for putting light sources in filter wheels which they did with the CFW7/a and using those goofy friction drives is just being cheap when you can use a toothed drive that never slips in my opinion as a long time design engineer. There's no end to the things I can point out that I think are just bad design decisions in that STL you have but I will hold back for another day. It still amazes me that they have the following they do. The only rational explanation that I can see is that most people just buy what they see others doing. I've seen the same thing out deep sea fishing: one boat stops, then another comes in close thinking they are catching fish. Then that attracts a third and a fourth and a fifth and next thing you have 20 boats in the same spot and no one is necessarily catching fish, but it is easier to stop where you see the boats than it is to think for yourself. Be honest Rick, why did you pick the STL versus all the other choices? Was it because you see a lot of them in use or was it based on careful analysis of all the relevant parameters that are important for your imaging interests? -- Correct domain name is arvig and it is net not com. Prefix is correct. Third character is a zero rather than a capital "Oh". |
#7
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ASTRO: Question on STL filter wheel
If it stops snowing I'll go out and see. I suspect I'll find something
about that band is the problem. I want to see it in the cold rather than bring it in the house. Warm it may behave very differently. Rick Richard Crisp wrote: i bet the lum filter is what is used the most and so you have a 'dent' in the band... "Rick Johnson" wrote in message ... It was the only used camera covering the FOV of the scope that was at a price I could afford. Bought it from a guy local for about half cost with the filters thrown in. The FLI 6303 with filters would have cost twice and had less field. It was my first choice but never saw a used one I could afford. I can get a friction band that will hold up in cold so shouldn't be hard to fix. I know several engineers in the aero-space industry. It's amazing what they can scrounge up. I sort of like such challenges. Compared to what it took to get a fraction of the results I'm getting now when I started in the late 50's with astro photography this is really simple stuff if you ignore image processing. The jury rigged stuff we used back then would blow your mind. No such thing as off axis guiders. You built nearly everything from what you could find in military surplus shops. Optics too often came from there. And if you adjust for inflation the cost of what you did put together was much much higher for a fraction the result. I'd get bored if it were too easy. My main challenge now is learning all the various ins and outs of processing the data. Mechanics of telescopes are easy for me but software -- that's very foreign to me. Rick Richard Crisp wrote: "Rick Johnson" wrote in message ... Yes it uses the same mechanism. I overlaid individual flat frames each taken after rotating to other filters then back to lum and I'd have to rotate one by up to 2 degrees to get them to line up but the center of rotation had to be where the center of the wheel would be, well "above" the flat. Did the same with the other filter positions but they all line up fine. A couple times the lum frame stopped half way between filters so I had half lum and half something else. Can't recall which color is next to it other than my Halpha and it wasn't that one as at that exposure time it would have been nearly black. Next time it would be about but not exactly in position. I suspect cold is the problem. It was near zero (-17.5C per the uncooled camera) when the problem first showed. Today at 10F it was doing the same however but only about 1 degree off max. I suspect that rubber ring is slippery right at some point at this temp. I'll take it apart and see what I find. I could just remove it I suppose as I doubt the corrector in the scope would defocus IR to any significant extent. Monday I'll call SBIG and see what they have to say. Now you are starting to see some of the reasons why I just patently reject anything that SBIG mades after about 2003 or so. There's no excuse for putting light sources in filter wheels which they did with the CFW7/a and using those goofy friction drives is just being cheap when you can use a toothed drive that never slips in my opinion as a long time design engineer. There's no end to the things I can point out that I think are just bad design decisions in that STL you have but I will hold back for another day. It still amazes me that they have the following they do. The only rational explanation that I can see is that most people just buy what they see others doing. I've seen the same thing out deep sea fishing: one boat stops, then another comes in close thinking they are catching fish. Then that attracts a third and a fourth and a fifth and next thing you have 20 boats in the same spot and no one is necessarily catching fish, but it is easier to stop where you see the boats than it is to think for yourself. Be honest Rick, why did you pick the STL versus all the other choices? Was it because you see a lot of them in use or was it based on careful analysis of all the relevant parameters that are important for your imaging interests? -- Correct domain name is arvig and it is net not com. Prefix is correct. Third character is a zero rather than a capital "Oh". -- Correct domain name is arvig and it is net not com. Prefix is correct. Third character is a zero rather than a capital "Oh". |
#8
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ASTRO: Question on STL filter wheel
"Rick Johnson" wrote in message ... If it stops snowing I'll go out and see. I suspect I'll find something about that band is the problem. I want to see it in the cold rather than bring it in the house. Warm it may behave very differently. I agree. Most likely you have what we call a "materials problem" in that the materials chosen for the job don't work over the full range of environments that it will be used. Rick Richard Crisp wrote: i bet the lum filter is what is used the most and so you have a 'dent' in the band... "Rick Johnson" wrote in message ... It was the only used camera covering the FOV of the scope that was at a price I could afford. Bought it from a guy local for about half cost with the filters thrown in. The FLI 6303 with filters would have cost twice and had less field. It was my first choice but never saw a used one I could afford. I can get a friction band that will hold up in cold so shouldn't be hard to fix. I know several engineers in the aero-space industry. It's amazing what they can scrounge up. I sort of like such challenges. Compared to what it took to get a fraction of the results I'm getting now when I started in the late 50's with astro photography this is really simple stuff if you ignore image processing. The jury rigged stuff we used back then would blow your mind. No such thing as off axis guiders. You built nearly everything from what you could find in military surplus shops. Optics too often came from there. And if you adjust for inflation the cost of what you did put together was much much higher for a fraction the result. I'd get bored if it were too easy. My main challenge now is learning all the various ins and outs of processing the data. Mechanics of telescopes are easy for me but software -- that's very foreign to me. Rick Richard Crisp wrote: "Rick Johnson" wrote in message ... Yes it uses the same mechanism. I overlaid individual flat frames each taken after rotating to other filters then back to lum and I'd have to rotate one by up to 2 degrees to get them to line up but the center of rotation had to be where the center of the wheel would be, well "above" the flat. Did the same with the other filter positions but they all line up fine. A couple times the lum frame stopped half way between filters so I had half lum and half something else. Can't recall which color is next to it other than my Halpha and it wasn't that one as at that exposure time it would have been nearly black. Next time it would be about but not exactly in position. I suspect cold is the problem. It was near zero (-17.5C per the uncooled camera) when the problem first showed. Today at 10F it was doing the same however but only about 1 degree off max. I suspect that rubber ring is slippery right at some point at this temp. I'll take it apart and see what I find. I could just remove it I suppose as I doubt the corrector in the scope would defocus IR to any significant extent. Monday I'll call SBIG and see what they have to say. Now you are starting to see some of the reasons why I just patently reject anything that SBIG mades after about 2003 or so. There's no excuse for putting light sources in filter wheels which they did with the CFW7/a and using those goofy friction drives is just being cheap when you can use a toothed drive that never slips in my opinion as a long time design engineer. There's no end to the things I can point out that I think are just bad design decisions in that STL you have but I will hold back for another day. It still amazes me that they have the following they do. The only rational explanation that I can see is that most people just buy what they see others doing. I've seen the same thing out deep sea fishing: one boat stops, then another comes in close thinking they are catching fish. Then that attracts a third and a fourth and a fifth and next thing you have 20 boats in the same spot and no one is necessarily catching fish, but it is easier to stop where you see the boats than it is to think for yourself. Be honest Rick, why did you pick the STL versus all the other choices? Was it because you see a lot of them in use or was it based on careful analysis of all the relevant parameters that are important for your imaging interests? -- Correct domain name is arvig and it is net not com. Prefix is correct. Third character is a zero rather than a capital "Oh". -- Correct domain name is arvig and it is net not com. Prefix is correct. Third character is a zero rather than a capital "Oh". |
#9
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ASTRO: Question on STL filter wheel
In message , Richard Crisp
writes using those goofy friction drives is just being cheap when you can use a toothed drive that never slips in my opinion as a long time design engineer. Weird coincidence department - I'm having exactly the same problem in my day job with a microplate reader (used in medical research). They allegedly went from a gear system to friction drive because customers complained about the noise, but why they didn't use a stepper motor or an encoder to make sure the wheel is in the right place escapes me. |
#10
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ASTRO: Question on STL filter wheel
"Jonathan Silverlight" wrote in message ... In message , Richard Crisp writes using those goofy friction drives is just being cheap when you can use a toothed drive that never slips in my opinion as a long time design engineer. Weird coincidence department - I'm having exactly the same problem in my day job with a microplate reader (used in medical research). They allegedly went from a gear system to friction drive because customers complained about the noise, but why they didn't use a stepper motor or an encoder to make sure the wheel is in the right place escapes me. no doubt the friction drive was cheaper to make these days it seems that it is only about delivering to the spec at the absolute minimum cost, unfortunately so you get substandard capacitors being substituted by unscrupulous fixed price contract assemblers to boost their operating margin, you see designers cutting corners to save a nickel here and there. It is really pretty distressing to pay nearly $10,000 for a piece of limited production camera gear and then find that it has problems with the filter wheel, doesn't cool worth a damn on a hot night, has higher read noise than similar products using the same sensor made by competitors, has to shim a nosepiece to get the sensor orthogonal to the optical axis and the list goes on and on and on. |
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