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Re: 6" Refractor on GM8 ?
Donald J. D'Egidio
David,
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I have the 150 and EQ4(CG5) just for the portability issue. All I did was to replace the aluminum tripod legs with homemade wooden legs and the scope is just fine. With the lower prices I would say go ahead and get one. I did install the dual axis drive. Don ----- Original Message -----
From: "The Gray Wizard" <dbell@...> To: <Losmandy_users@...> Sent: Tuesday, September 12, 2000 15:49 Subject: RE: [Losmandy_users] Re: 6" Refractor on GM8 ? I keep hearing this. I already have a G11. Use it with my C11 SCT. I was |
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Re: GM-8 RA problem...
Ray Porter
Paul,
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I think Chris's question is why his cheap CG-5 seems to perform so much better than his new GM-8. Actually, he has a very specific question. For those who have used the GM-8 for unguided CCD imaging, what is the longest unguided exposure he should reasonably expect (assuming a good polar alignment)? ================================================ Ray Porter Applications Analyst Programmer Administrative Information Services, UNC-CH Phone: 966-5878 email: ray_porter@... dragon@... Home Page: "Meddle not in the affairs of dragons, for thou art crunchy and taste good with ketchup." ----- Original Message -----
From: "Paul Sterngold" <psterngold@...> To: <Losmandy_users@...> Sent: Tuesday, September 12, 2000 4:19 PM Subject: Re: [Losmandy_users] GM-8 RA problem... If not, you might want to post this on one of the CCD lists on eGroups. |
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Re: GM-8 RA problem...
Paul Sterngold
I'm not seeing anything here involving Losmandy. Am I missing something? If
not, you might want to post this on one of the CCD lists on eGroups. Paul Sterngold --- ccwoodruff@... wrote: Hello, __________________________________________________ Do You Yahoo!? Yahoo! Mail - Free email you can access from anywhere! |
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Re: 6" Refractor on GM8 ?
Ray Porter
Actually the CG-5 is okay if you disassemble and re-grease the mount and
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replace the silly aluminum legs with wooden ones. A thump to the OTA will dampen out in a second or so (as opposed to 6 seconds or more with the aluminum legs). The mount itself (at least the late model ones) is pretty decent and is roughly equivalent to the Vixen Great Polaris Deluxe. I'm currently using my CR150 on a G-11 with the GM8 tripod which gives me excellent stability with a fairly portable configuration. I'm still debating whether to keep my CG-5 for an even more portable mount or to sell it and just take the G-11 and GM8 tripod everywhere I go. Heck, even the little polar alignment scope for the CG-5 works remarkably well once you figure out that the directions for calibrating and aligning it are missing some key parts. ;-) The Chinese made motors also track very well. ================================================ Ray Porter Applications Analyst Programmer Administrative Information Services, UNC-CH Phone: 966-5878 email: ray_porter@... dragon@... Home Page: "Meddle not in the affairs of dragons, for thou art crunchy and taste good with ketchup." ----- Original Message -----
From: "The Gray Wizard" <dbell@...> To: <Losmandy_users@...> Sent: Tuesday, September 12, 2000 3:49 PM Subject: RE: [Losmandy_users] Re: 6" Refractor on GM8 ? I keep hearing this. I already have a G11. Use it with my C11 SCT. Iwas thinking about picking up the CR150 mounted on a CG5 hoping for a moremuch for that mount. Mounting it on my G11 kills any hope of portability |
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Re: 6" Refractor on GM8 ?
The Gray Wizard
I keep hearing this. I already have a G11. Use it with my C11 SCT. I was
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thinking about picking up the CR150 mounted on a CG5 hoping for a more portable scope. The consensus, however seems to be that the OTA is too much for that mount. Mounting it on my G11 kills any hope of portability however. David David E. Bell The Gray Wizard dbell@... www.graywizard.net "Wisdom begins in wonder." - Socrates -----Original Message-----
From: Chase McNiss [mailto:cmcniss@...] Sent: Tuesday, September 12, 2000 3:22 PM To: Losmandy_users@... Subject: [Losmandy_users] Re: 6" Refractor on GM8 ? My Groups | Losmandy_users Main Page | Start a new group! I have a friend in my astronomy club who has a CR150 and and AP130 f8, which he mounts on his GM8. The scopes are OK for visual usage. I would prefer the G11 myself for any scope that size., The GM8 works, but if you have a low tolerance for shaky mounts go with something bigger. Overall I would recommend the G11 for anything over a 4" F8 Refractor. You will have a lot more flexability for any future scope purchases and once you mount your scope on something rock solid, you will wonder how you ever put up with anything else. I have a 6" SkyWatcher, but I built my own Alt-Az mount for it and use it exclusively for deep sky and public skywatches, keeping the magnification under 150X in most cases. Clear skies, Chase -- In Losmandy_users@..., "James Grigar" <pt19@m...> wrote: I have a 6" Skywatcher, I think about purchase a GM8 system. willGM8 handle this scope well? the OTA weight 20 lbs. Plan to use CCDShould I get the G11 instead of GM8? Any Comment welcome . To unsubscribe from this group, send an email to: Losmandy_users-unsubscribe@... |
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Re: Digest Number 39
David A. Silva
Hi Ray
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Edward at Lumicon once suggested a quick process to resolve this kind of issue. Move one axis 360 degrees and watch the encoder position numbers on the DSC. When the encoder resolution is off, the encoder number will be way off when you get to the 360 position. You can then gauge / guess what it should be and test again. Luckily both encoders should be the same, so once you've found it on one axis you're home free. I did this on a Gibralter mount with encoders, it should work the same on any mount. -David On 12 Sep 2000 09:53:02 -0000, Ray Porter wrote:
Trying the procedure you recommend had already occurred to me and I plan to |
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Losmandy Meade Field Tripod Adapter
Chase McNiss
I am looking to put a pier in my yard and I have ordered the Losmandy
MA adapter to adapt my GM8 head to the pier. Is there anybody out there that has done this. What size pier did you use and how did you attach the MA adapter to the pier? Also what pier material did you use and did you attach the pier to the cement base via a flange or did you sink the pier right into the concrete? Last of all, where did you get the MA adapter, I am having trouble ordering one, nobody seems to have any in stock and a shipping date is not available. I would like to get the pier set up before the ground here in Northern New England freezes. Thanks in advance for the help, Chase |
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Re: 6" Refractor on GM8 ?
Chase McNiss
I have a friend in my astronomy club who has a CR150 and and AP130
f8, which he mounts on his GM8. The scopes are OK for visual usage. I would prefer the G11 myself for any scope that size., The GM8 works, but if you have a low tolerance for shaky mounts go with something bigger. Overall I would recommend the G11 for anything over a 4" F8 Refractor. You will have a lot more flexability for any future scope purchases and once you mount your scope on something rock solid, you will wonder how you ever put up with anything else. I have a 6" SkyWatcher, but I built my own Alt-Az mount for it and use it exclusively for deep sky and public skywatches, keeping the magnification under 150X in most cases. Clear skies, Chase -- In Losmandy_users@..., "James Grigar" <pt19@m...> wrote: I have a 6" Skywatcher, I think about purchase a GM8 system. willGM8 handle this scope well? the OTA weight 20 lbs. Plan to use CCDShould I get the G11 instead of GM8? Any Comment welcome . |
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GM-8 RA problem...
Hello,
This is my first post here so please be patient! I have been imaging with a CG-5 and a Vixen GP using a C8 @ fl 630 and a TV 101 @ fl 400. Using an ST-7 UNGUIDED I have achieve 1x1 binning images of a duration at ~40 sec (C8) and ~60 sec (TV101) with about 75% good image rate using the CG-5 (with Vixen Drives) and ~50 sec (C8) and ~70 sec (TV101) using the Vixen GP (with Vixen Drives). I purchased the GM-8 mount becasue it is supposed to be a better mount (which I assumed in every way) than the CG-5 and the Vixen GP. So far the best I can do UNGUIDED with this mount is ~20 sec with the TV101 keeping only 50% of the images! Wow! At fl 400 using an ST-7 I am seeing stars that do not move over the course of 5 minutes (so I know my polar alignment is at least pretty good) but are either short lines or egg shaped. Here are the things I have done to the mount to try and correct this (which in the end did help as my results before were even worse!). 1. Took apart, re-lubed. 2. Re aligned worm gear. 3. Swapped the RA / DEC motors. 4. Swapped the RA / DEC worms. 5. Tried overloading to the East. Once again the best I could do is 20 sec. I have heard of people using the Vixen GP-DX @ fl 1000 for 3 minutes UNGUIDED and I am wondering if since I like to do unguided work maybe that is the mount I really want for the scopes mentioned, at this point my CG-5 kicks this mounts butt! Anyways, I guess what I'd like to know is am I expecting too much out of this mount? What kind of UNGUIDED results are the group getting? Thank you very much for listening!!! Sorry for the ranting!! Chris Woodruff www.ccwoodruff.com |
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Re: GM-8 stepper motor and CCD
Paul Sterngold
I'm not sure what "torque and swing" means. The stepper motor rotates a
worm, which in turn rotates a worm gear, which in turn rotates the polar shaft. I believe this is how all quality mounts drive their polar axis, including Astro-Physics, Takahashi, Mountain Instruments, Parallax, etc. The size of each step is important, and so is the amount of vibration introduced. If the steps are too large, then they are visible (either to the naked eye or to the camera). The size of the steps on the GM8 and G11 is small enough so that this isn't a problem, either visually or when imaging. I have found that the vibration from the steps can be seen IF: 1) I don't have enough weight on the mount. When my 4" f/8 refractor is the only thing on my GM100 (similar to G11), images at high magnification are not sharp, due to the vibration from the stepping. 2) The load is not well balanced, with a slight bias to the east. I have not yet seen this problem on my GM8 but it's new and hasn't been used yet for high power observing. Hope this helps. Paul Sterngold --- John Ford <pattern120@...> wrote: I looked through all previous EGroup posts and sci.astro.ccd-imaging, __________________________________________________ Do You Yahoo!? Yahoo! Mail - Free email you can access from anywhere! |
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Re: Thanks...
Donald J. D'Egidio
Paul,
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They are not based on powers of 2. It's just a matter of how many lines are on the codewheel. US Digital has a 540 count encoder. That is the encoder Mark has that gives him the 2160 count. It is only a physical parameter that sets the encoder resolution. Check out this URL for a more detailed explanation. Don ----- Original Message -----
From: "Paul Sterngold" <psterngold@...> To: <Losmandy_users@...> Sent: Tuesday, September 12, 2000 0:22 Subject: Re: [Losmandy_users] Re: Thanks...
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GM-8 stepper motor and CCD
John Ford
I looked through all previous EGroup posts and sci.astro.ccd-imaging,
but was unable to find "final" details about this potential problem. My GM-8 has been a flawless performer, and I am anticipating the purchase of a CCD(STV)to be used primarily at f=650mm. A few people have told me that the Losmandy stepper motors are a constant tribulation due to the "torque-and-swing" action of the stepper motors, and do not allow good imaging. Some have said that in spite of good tracking accuracy, this sub-arc- second swing constantly "smudges" the image. Say it ain't so... Thanks, John |
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Re: Encoder resolution
Charles Taylor
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From: Charles Taylor <chucktaylor3@...> Oops, Let me add a bit of clarification to my earlier post I wrote: Therefore, no matter what ther "resolution" is at the encoder or at the DSC, you could disconect the encoder, hook it up to a motor and spin it for days and days and send "billions and billions" of impulses. It should read: Therefore, no matter what ther "resolution" is at the encoder or at the DSC, you could disconect the encoder FROM THE TELESCOPE MOUNT, LEAVING IT CONNECTED TO THE DSC, hook THE ENCODER up to a motor and spin it for days and days and send "billions and billions" of impulses TO THE DSC. THE NUMBER OF PULSES WOULD NOT BE LIMITED BY BYTE SIZE. Thank you for your patience (This is what happens when I write late at night after tearing apart a couple of printers to get steppers ;-) One Barn door mount to go please... Chuck Taylor |
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Re: Encoder resolution
Charles Taylor
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From: midniterider@... <midniterider@...> Chuck: The resolution of an optical encoder is determined by how many, and how small the light/dark slots are on the wheel. My point is that DSC's are digital, which means they are binary, which means that total resolution, or any number in between, will be divisible by two. That's why I questioned the number used previously. The resolution that was stated could not be divided by two continuously without fractional numbers. There are no fractions in binary. We can use digital/binary to represent numbers in another base system, i.e. octal, decimal, hexadecimal, or even degrees, minutes, and seconds. Did I clear it up, or did I merely "muddy the waters"? Bruce Inscoe ****<end quote>** Hi Bruce, The DSC's are binary at some point in their operation, But not in the manner you are thinking. They are not receiving impulses from the encoders in a byte. The pulses are received separately and sequentially (as in a serial port) and not in a byte (like a parallel port) which would limit their number to 2 to the xth where x equals the number of bits in the byte. Therefore, no matter what ther "resolution" is at the encoder or at the DSC, you could disconect the encoder, hook it up to a motor and spin it for days and days and send "billions and billions" of impulses. There is no limit to the number of impulses. (This of course assumes the DSC is smart enough to figure that at 360 degrees you go back to zero --- or at 24 hours you go back to zero --- depending on which axis) If the encoder stored up all of the pulses and sent them in one byte then the byte size would limit the resolution and as you said, it would increase as two to the xth power where x equals the number of bits in the byte (which I think is what you are looking for) In effect, you actually have two places where resolution can be limited. The first is in the physical construction of the encoder and the gear ratio connecting it to the mount. The second limit is set by the DSC and is determined by how big a turn it will register for every pulse. If the DSC were to interpret every pulse as indicating a one degree turn, then you would only have a resolution of one degree. If it interprets every pulse to be a millionth of a degree, the DSC would "limit" resolution to that level. Of course, the encoders and gearing ratios would then have to feed it a pulse for every millionth of a degree. But internally (as far as the electronics go) even through the DSC uses binary circuitry, you are handling the pulses one by one. They are not accumulating into bytes which would supply the 1-2-4-8-16-32-64-128... sequence you are looking for. Does this help? It is late at night so I am probably not very clear. Take care, Chuck Taylor lurker at large (and if I keep eating, even more at large) |
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Re: Thanks...
Paul Sterngold
--- midniterider@... wrote:
Mark:I think they're all powers of 2, as is everything in the computer world: 256 = 2^8 (one byte) 1024 = 2^10 2048 = 2^11 4096 = 2^12 Paul Sterngold __________________________________________________ Do You Yahoo!? Yahoo! Mail - Free email you can access from anywhere! |
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Re: Encoder resolution
Donald J. D'Egidio
Bruce,
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Forget about binary when talking about optical encoders. The counts per revolution are a physical characteristic determined by the amount of lines on the codewheel. Check out this page for a more detailed operational description. Don ----- Original Message -----
From: <midniterider@...> To: <Losmandy_users@...> Sent: Monday, September 11, 2000 21:09 Subject: [Losmandy_users] Re: Encoder resolution
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Re: Thanks...
--- In Losmandy_users@..., Mark Simmons <msimmons@d...> wrote:
wrote: regardingJust wanted to say thanks to all of you for your input my seemsencoder problem. It appears that the correct encoder resolutionsettingis 4320. Apparently the encoders I have are 2160 instead of thenormal2048 shipped with the Losmandy kit. The DSC unit now is set upMark: Ifthat it should be binary. In other words, for every bit position, wouldit had two bits, the number of possible combinations of on/off 512,be four. You can carry this on out...8, 16, 32, 64, 128, 256, this1024, 2048, etc. and see how it doubles every time, thus all oflogic results in fractional numbers, which causes me to wonder.Bruce, codes/rev. For reasons I don't understand, my encoders have 540counts per revolutions, which is then multiplied by 4 by a mechanical functionwithin the encoder. the end result is 2160. US Digital makes encoders from50 to 1024 counts per revolution that can be used resulting in encoderresolutions of 200 to 4096. This is then multiplied by the gear ration of 2 to 1Mark: Like you, I don't understand how they can make encoders with weird counts/revolution. I'm an electronics type and understand digital just fine, so the odd numbers just don't seem right. Maybe it's the mechanical gearing thing.:-0 Bruce Inscoe |
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Re: Encoder resolution
--- In Losmandy_users@..., "Charles Taylor"
<chucktaylor3@i...> wrote: Hi,Chuck: The resolution of an optical encoder is determined by how many, and how small the light/dark slots are on the wheel. My point is that DSC's are digital, which means they are binary, which means that total resolution, or any number in between, will be divisible by two. That's why I questioned the number used previously. The resolution that was stated could not be divided by two continuously without fractional numbers. There are no fractions in binary. We can use digital/binary to represent numbers in another base system, i.e. octal, decimal, hexadecimal, or even degrees, minutes, and seconds. Did I clear it up, or did I merely "muddy the waters"? Bruce Inscoe |
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Re: 6" Refractor on GM8 ?
Ray Porter
Actually the mount that comes with is okay. I've had mine apart when I
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re-greased it and it is very well made. I found none of the metal burrs and shavings Jeff DeTray talks about polishing away on his CG-5 overhaul page. All I had to do was remove the glue-like lubricant and my CG-5 started working very well indeed. IMHO, the later model CG-5 is probably closer to the Vixen GP Deluxe rather than the GP. Even so the mount is still probably marginal with the long refractor. The extruded aluminum tripod that comes with this mount is another matter all together. It's useless for anything much heavier than a short-tube 80 refractor and it is totally ludicrous with the long f8/150. Of course, now that I have a G-11, the whole CG-5 debate is irrelevant for me. ================================================ Ray Porter Applications Analyst Programmer Administrative Information Services, UNC-CH Phone: 966-5878 email: ray_porter@... dragon@... Home Page: "Meddle not in the affairs of dragons, for thou art crunchy and taste good with ketchup."
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