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Nexstar 90 mm f/10 refractor
I got this cheap Nexstar achromat refractor, other night looked at the Moon and Mars with it, quiet good!
At 110x power full Moon had a slight yellowish/green tint on it's edges, Mars looked good also, no color fringes, but 110x power just not enough for Mars to see it's full glory, any surface features. I think, it's a keeper for now for quick look around the sky in the back yard! Play with the NexStar Cosmos goto a bit too! Need a heavier tripod , hole set up jiggles too much! Wonder how good is it for tracking satellites or the ISS? |
#2
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Nexstar 90 mm f/10 refractor
On Friday, 23 November 2018 10:43:12 UTC-5, StarDust wrote:
I got this cheap Nexstar achromat refractor, other night looked at the Moon and Mars with it, quiet good! At 110x power full Moon had a slight yellowish/green tint on it's edges, Mars looked good also, no color fringes, but 110x power just not enough for Mars to see it's full glory, any surface features. I think, it's a keeper for now for quick look around the sky in the back yard! Play with the NexStar Cosmos goto a bit too! Need a heavier tripod , hole set up jiggles too much! Wonder how good is it for tracking satellites or the ISS? Can they even slew fast enough to keep up with the orbiting white elephant? |
#3
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Nexstar 90 mm f/10 refractor
On Friday, November 23, 2018 at 9:13:16 AM UTC-8, RichA wrote:
On Friday, 23 November 2018 10:43:12 UTC-5, StarDust wrote: I got this cheap Nexstar achromat refractor, other night looked at the Moon and Mars with it, quiet good! At 110x power full Moon had a slight yellowish/green tint on it's edges, Mars looked good also, no color fringes, but 110x power just not enough for Mars to see it's full glory, any surface features. I think, it's a keeper for now for quick look around the sky in the back yard! Play with the NexStar Cosmos goto a bit too! Need a heavier tripod , hole set up jiggles too much! Wonder how good is it for tracking satellites or the ISS? Can they even slew fast enough to keep up with the orbiting white elephant? Setting 9 = 4º / sec top speed Dude, like a Ferrari! ISS speed 4.76 miles/s, what ever is in angles? Bought this set-up on ebay for $90 incl. shp. Seller said not working, for parts. Only the 12V jack was broken, $2 part! Now works. Having fun with this thing, light, portable! LOL! |
#4
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Nexstar 90 mm f/10 refractor
On Fri, 23 Nov 2018 12:27:56 -0800 (PST), StarDust
wrote: Setting 9 = 4º / sec top speed Dude, like a Ferrari! ISS speed 4.76 miles/s, what ever is in angles? Not so simple, because the distance is changing continuously. Satellites don't have constant angular velocities when viewed from a fixed ground position. The range for LEO satellites, in particular, is very large. You can see that when you watch the ISS pass over- it's moving fast when overhead, and just creeps along the sky when near the horizon. Mounts that can track satellites use fancy software to vary the tracking rate continuously. |
#5
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Nexstar 90 mm f/10 refractor
On Friday, November 23, 2018 at 9:13:16 AM UTC-8, RichA wrote:
On Friday, 23 November 2018 10:43:12 UTC-5, StarDust wrote: I got this cheap Nexstar achromat refractor, other night looked at the Moon and Mars with it, quiet good! At 110x power full Moon had a slight yellowish/green tint on it's edges, Mars looked good also, no color fringes, but 110x power just not enough for Mars to see it's full glory, any surface features. I think, it's a keeper for now for quick look around the sky in the back yard! Play with the NexStar Cosmos goto a bit too! Need a heavier tripod , hole set up jiggles too much! Wonder how good is it for tracking satellites or the ISS? Can they even slew fast enough to keep up with the orbiting white elephant? ISS speed is 3.2 deg/s, Nexstar 4 deg/s! Bruhaha!!!! |
#6
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Nexstar 90 mm f/10 refractor
On Friday, November 23, 2018 at 3:14:38 PM UTC-8, Chris L Peterson wrote:
On Fri, 23 Nov 2018 12:27:56 -0800 (PST), wrote: Setting 9 = 4º / sec top speed Dude, like a Ferrari! ISS speed 4.76 miles/s, what ever is in angles? Not so simple, because the distance is changing continuously. Satellites don't have constant angular velocities when viewed from a fixed ground position. The range for LEO satellites, in particular, is very large. You can see that when you watch the ISS pass over- it's moving fast when overhead, and just creeps along the sky when near the horizon. Mounts that can track satellites use fancy software to vary the tracking rate continuously. Need the keplerian elements for tracking ISS or others before tracking. many websites has it! That's what the telescopes software reads. I have an EQ mount with SS2K, if the ISS flies west to east it has to flip at meridian. Alt/Az mount don't have this problem, can track continuously. |
#7
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Nexstar 90 mm f/10 refractor
On Fri, 23 Nov 2018 15:23:09 -0800 (PST), StarDust
wrote: On Friday, November 23, 2018 at 3:14:38 PM UTC-8, Chris L Peterson wrote: On Fri, 23 Nov 2018 12:27:56 -0800 (PST), wrote: Setting 9 = 4º / sec top speed Dude, like a Ferrari! ISS speed 4.76 miles/s, what ever is in angles? Not so simple, because the distance is changing continuously. Satellites don't have constant angular velocities when viewed from a fixed ground position. The range for LEO satellites, in particular, is very large. You can see that when you watch the ISS pass over- it's moving fast when overhead, and just creeps along the sky when near the horizon. Mounts that can track satellites use fancy software to vary the tracking rate continuously. Need the keplerian elements for tracking ISS or others before tracking. many websites has it! Yeah, that's what you need (didn't know that mount had the satellite tracking feature built in... nice). I have an EQ mount with SS2K, if the ISS flies west to east it has to flip at meridian. Alt/Az mount don't have this problem, can track continuously. Lots of equatorial mounts can track all the way across the sky. That's why I like fork mounted equatorials. The problem with all mounts is that they have a tracking singularity. With equatorial mounts it's the pole; with alt-az mounts it's the zenith. Tracking through those requires one of the axes to rotate infinitely fast. Plus, given that no scope has perfectly perpendicular axes, there is a small region around those points which is inaccessible to the mounts (although with a well made mount, that area is sufficiently small to be insignificant). |
#8
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Nexstar 90 mm f/10 refractor
On Saturday, November 24, 2018 at 6:00:14 AM UTC-8, Chris L Peterson wrote:
On Fri, 23 Nov 2018 15:23:09 -0800 (PST), On Friday, November 23, 2018 at 3:14:38 PM UTC-8, Chris L Peterson wrote: On Fri, 23 Nov 2018 12:27:56 -0800 (PST), wrote: Setting 9 = 4º / sec top speed Dude, like a Ferrari! ISS speed 4.76 miles/s, what ever is in angles? Not so simple, because the distance is changing continuously. Satellites don't have constant angular velocities when viewed from a fixed ground position. The range for LEO satellites, in particular, is very large. You can see that when you watch the ISS pass over- it's moving fast when overhead, and just creeps along the sky when near the horizon. Mounts that can track satellites use fancy software to vary the tracking rate continuously. Need the keplerian elements for tracking ISS or others before tracking. many websites has it! Yeah, that's what you need (didn't know that mount had the satellite tracking feature built in... nice). Most mount don't have sat. tracking built in, it has to be hooked up to a PC and software does the trick! I think, the SS2K hand controller can receive sat. tracking data direct through serial port and track sats, without PC's.! I have an EQ mount with SS2K, if the ISS flies west to east it has to flip at meridian. Alt/Az mount don't have this problem, can track continuously. Lots of equatorial mounts can track all the way across the sky. That's why I like fork mounted equatorials. The problem with all mounts is that they have a tracking singularity. With equatorial mounts it's the pole; with alt-az mounts it's the zenith. Tracking through those requires one of the axes to rotate infinitely fast. Plus, given that no scope has perfectly perpendicular axes, there is a small region around those points which is inaccessible to the mounts (although with a well made mount, that area is sufficiently small to be insignificant). |
#9
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Nexstar 90 mm f/10 refractor
On Saturday, November 24, 2018 at 7:16:22 AM UTC-8, StarDust wrote:
Most mount don't have sat. tracking built in, it has to be hooked up to a PC and software does the trick! My 25" dob is equipped with ServoCat and Argo Navis and can track satellites without needing a computer... but the AN *is* a computer, of sorts. From the manual... "Argo Navisâ„¢ has a powerful 32 bit CPU at its heart that will guide you continuously to keep track of satellites. The sophisticated software even accounts for precession and atmospheric refraction." |
#10
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Nexstar 90 mm f/10 refractor
On Saturday, November 24, 2018 at 1:52:11 PM UTC-8, palsing wrote:
On Saturday, November 24, 2018 at 7:16:22 AM UTC-8, StarDust wrote: Most mount don't have sat. tracking built in, it has to be hooked up to a PC and software does the trick! My 25" dob is equipped with ServoCat and Argo Navis and can track satellites without needing a computer... but the AN *is* a computer, of sorts. From the manual... "Argo Navisâ„¢ has a powerful 32 bit CPU at its heart that will guide you continuously to keep track of satellites. The sophisticated software even accounts for precession and atmospheric refraction." I guess, that's why the Vixen SS2K hand controller is much more expensive , because it's not just a dumb hand controller , but a computer also. I read about it long time ago in S&T, after the telescope set-up, aligned, sat data downloaded into the hand controller and activated, the mount goes into tracking mode. Means, position it's self, point where the sat will appear on the sky. Once the time comes for the sat appearance, a minute or two before it's start beeping to get ready. Once the set is visual, telescope start tracking it. I heard people track sats manually successfully , using a guide scope and pushing the OTA by hand, broomstick attached (LOL) keeping the sat in the cross hair of the guide scope. |
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