Re: Catching up: Losmandy/ Gemini I and PEC
Hi John,
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>>? I've read Losmandy/ Gemini I doesn't play well with PEC because of the non-integer gear reduction in the stock Losmandy gear boxes.??
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That is incorrect. There's not even a remote possibility that gearboxes could produce a non-integer reduction. Here are some specs for gears and their ratios:
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As far as I know, MI-250 gearboxes were similar, except driving in the reversed direction, so Gemini gear reduction setting was negative for these mounts.
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I'm guessing that the non-integer reduction in this case really refers to the error introduced by poorly adjusted worm blocks, usually not seated straight. Same page by Mark Crossley addresses that, as well:
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The error that this type of mis-adjustment produces often manifests itself as a 76-78 sec periodic error that can't be corrected by Gemini PEC since it doesn't repeat with every worm cycle (hence a non-integer ratio). This only becomes important for PEC if your mount really has this error (by far not everyone has it) and if you can't adjust it out by properly aligning the worm blocks. I'm not sure how the worm is held on an MI-250, but I assume similar problems could occur if orthogonality is not adjusted properly. Easy enough to check with a PEMPro PE recording.
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>> Does Gemini I support PEC programming using a 2x worm cycle, or is that for Gemini II only?
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That feature was added in Gemini-II. If you're still thinking about the problem where your PEC playback phase shifted between sessions, the worm-block error can't do that. I've used PEMPro and PEC on Gemini-1 for many years with good results. The only thing you may need to check is that PEC programming with PEMPro doesn't introduce a linear drift -- that was something that could happen with PEMPro + Gemini-1. But that also wouldn't account for phase shift between sessions.
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Regards,
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? -Paul
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On Mon, Aug 19, 2024 at 06:49 AM, macdonjh wrote:
I'm catching up with twenty years of experience regarding PEC and Gemini I.? I've read Losmandy/ Gemini I doesn't play well with PEC because of the non-integer gear reduction in the stock Losmandy gear boxes.? Did that used to be true?? Is it still true?? Do the new gear boxes Losmandy sells have integer reductions, or are the McLennen gear boxes still useful mods?? Does PEMPro deal with non-integer reductions smoothly?? Does Gemini I support PEC programming using a 2x worm cycle, or is that for Gemini II only?
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I'd rather not train my mount (go-to MI-250 w/ Gemini I) the old fashioned way, so I'm interested in changes and advances which have happened while I've been using eye pieces.
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Catching up: Losmandy/ Gemini I and PEC
I'm catching up with twenty years of experience regarding PEC and Gemini I.? I've read Losmandy/ Gemini I doesn't play well with PEC because of the non-integer gear reduction in the stock Losmandy gear boxes.? Did that used to be true?? Is it still true?? Do the new gear boxes Losmandy sells have integer reductions, or are the McLennen gear boxes still useful mods?? Does PEMPro deal with non-integer reductions smoothly?? Does Gemini I support PEC programming using a 2x worm cycle, or is that for Gemini II only?
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I'd rather not train my mount (go-to MI-250 w/ Gemini I) the old fashioned way, so I'm interested in changes and advances which have happened while I've been using eye pieces.
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Re: RS-232 interface IC and RS-232 port replacement part numbers?
On Thu, Aug 15, 2024 at 08:09 AM, Brendan wrote:
You might want to grab a CR2450 battery and holder and replace the G1 CR2354 !
Oh, that's a great idea! Next time though. I replaced the CR2354, so I'll have a little time before it dies to order the upgrade battery holder.
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I just did a few hours of daylight testing with my laptop and then the telescope's mini PC. It wouldn't slew to point to anything in the eastern half of the sky with 1.0 deg set for the western goto limit. I'll dig into that more later. It seems to work perfectly well with the western goto limit set to 0.
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Here's a sped-up slew test video with several automated slew commands from NINA. (It's alive!)?
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There's a decent chance the skies will be clear enough tonight for some real testing. Once I'm satisfied it's back to 100%, I'll share all the part numbers I used for the repairs - just in case someone else needs them later.
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Thanks a ton for all the help, Brendan & Michael. I really appreciate the guidance.
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Re: RS-232 interface IC and RS-232 port replacement part numbers?
Well done Bryan. ?Good work. ?
One tiny observation. ? You might want to grab a CR2450 battery and holder and replace the G1 CR2354 ! ?
Why¡. The CR2450 are easier to get nowdays. The battery holders have same spacing and it¡¯s easy to fit. ? It¡¯ll give around 20-30% more battery capacity and since it¡¯s side ¡°claw clip¡±, easy to R&R with pwr on. ? ?This not lose system SRAM etc settings settings?
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Plus changing CR2450 batteries is easy compared to the CR2354. ?
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it¡¯s up to you. I like the CR2450 and even fit them to older G1s that have CR2032s. ?Just a few holes and PCB rivets and a small jumper wire?
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Users love the extra battery capacity and ease of changing them?
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FWIW
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Well done indeed. ?Your a champ !
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cheers
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Brendan
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Re: RS-232 interface IC and RS-232 port replacement part numbers?
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From: [email protected] <[email protected]> On Behalf Of Bryan Duke
Sent: 15 August 2024 09:06
To: [email protected]
Subject: Re: [Gemini_users_io] RS-232 interface IC and RS-232 port replacement part numbers?? I replaced the serial IC, C19, C21, C44, and the RJ22 port. The bench smoke check was good and my laptop seems to talk to it ok. I¡¯ll test it connected to the mount and the mini PC soon.
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Re: RS-232 interface IC and RS-232 port replacement part numbers?
I replaced the serial IC, C19, C21, C44, and the RJ22 port. The bench smoke check was good and my laptop seems to talk to it ok. I¡¯ll test it connected to the mount and the mini PC soon.
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So far, so good.
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Re: Part number for L1 in Gemini-1 47uH
Bren Smith came up with the answer (thank you Bren)! ? Wurth series WE-PD2 ferrite core 5.2 x 5.8 x 4.5mm. mrn: 744774147 ? David ? ?
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From: [email protected] <[email protected]> On Behalf Of David C. Partridge
Sent: 14 August 2024 05:09
To: [email protected]
Subject: [Gemini_users_io] Part number for L1 in Gemini-1 47uH? The schematic specifies 47uH, 0.7A.?? It¡¯s about 6mm square with a round bobbin.? Could it be Bourns SDR0604-470KL? ? Thanks David
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Part number for L1 in Gemini-1 47uH
The schematic specifies 47uH, 0.7A.?? It¡¯s about 6mm square with a round bobbin.? Could it be Bourns SDR0604-470KL? ? Thanks David
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Re: RS-232 interface IC and RS-232 port replacement part numbers?
On Mon, Aug 12, 2024 at 06:42 PM, Brendan wrote:
Well picked up. ?I think I looked at one data sheet got the specs and another place showed slightly different specs particularly capacitance
I think I did the same thing. The parts are on the way - progress soon!
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Re: RS-232 interface IC and RS-232 port replacement part numbers?
Well picked up. ?I think I looked at one data sheet got the specs and another place showed slightly different specs particularly capacitance
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The ¡°L¡± is low capacitance, the ¡°N¡± nickel plate the ¡°S¡± ?packing. ?
I must have looked at a wrong one to compare.?
You are doing great ! ? Kudos
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cherrs
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bren?
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Brendan
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Re: RS-232 interface IC and RS-232 port replacement part numbers?
Thanks Brendan,
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I'm glad you're helping chew on this with me. Looking deeper into the spec sheet, it seems like they might be the same actual part with the only difference being what sized reel they ship on (if you buy the whole reel). The attached image shows their numbering scheme. That's from here:
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The way I read that, the T comes on a 13" reel and the H comes on a 7" reel. Everything else is the same. It's strange that the product page is slightly different between the two...gotta love other people's databases, I guess.
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Like you suggested, I'll skip replacing them for now as long as they look ok. I do plan on ordering some with the rest of my Mouser order just to have them on hand.
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Thanks again!
Bryan
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Re: RS-232 interface IC and RS-232 port replacement part numbers?
Cheers Bryan
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happy yo help. ?Anything needs just ask. ? I would have thought low capacitance would be best ?to less encoder wave shape interference?
But maybe more could help, I¡¯m not sure. ?If it¡¯s ok atm leave them. Unless you feel they are charred!?
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I feel the V5.5MLA0805LNH is way to high in capacitance compared to the other 3500pf to 400pf. ?Last the LNH is 5V DC rated the other is 5.5V
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cheers
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Brendan
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Re: RS-232 interface IC and RS-232 port replacement part numbers?
You're right about the dirt & grass inside. I think it'll clean up fine. I'll take an extra look at F1 & the RVs.
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Thanks for the clarification on pin 8. I misread the schematic on the Gemini FAQ and was looking at the wrong thing. That's a great tip on the RJ22 port catch tabs too.
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For the RVs, it looks like there's a V5.5MLA0805LNT & V5.5MLA0805LNH currently available with LNH seemingly the more popular one (i.e. the higher stock at suppliers - and a slightly higher capacitance spec). Is the LNH the one I'd want there? (I think the drives are working fine, but they look really easy to swap too.)
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Thanks again,
Bryan
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Re: RS-232 interface IC and RS-232 port replacement part numbers?
Bryan many thanks great images...they tell all, "the rude Gemini"hahaha Imgur does this just to cover their legal ass .? Its like a bug has got in and done its thing all around the bottom of the board.? Really needs a good clean bottom half.
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U6 pin 8, "the black pin" goes to R44 and is "R1in" which is Pin 3 of J7.??? Pin 4 of of J7 is "T1out" from U6 pin 13.?? I think its just been marked with a black permanent marker to identify.?? But there is a lot of detritus and dirt on the PCB...use a and cleaner spray (electronic or Isopropyl 70%/Distilled water 30% mix)?
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Clean the board replace that socket.?? Cut away old as much of the socket as you can with side cutters.?? Don't worry...its going, so don't be nice about it.?? Leave the pins sticking up? though.?? Then heat these pads to melt (with solder iron), pull pins out, one at a time (with pliers, tweezers).? If any solder is left, clear holes with soder wick dipped in flux or rub flux on it....it sucks solder up much more quickly when heated with an iron.?? Ensure iron tip is clean and a little solder on it to start the process of "wetting" sucking up the old solder.?? If any solder "is still left" in holes...small hand drill and 0.7mm drill out.?? Clean up as above with flux cleaner or Isopropyl 70%/Distilled water 30% mix and brush.
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Seat new socket "fully so tabs go thru PCB"...solder in...use flux!?? Then with an air heat gun (or what ever you have) ....heat those little black tabs underneath and once they soften, stick a small screwdriver blade in between "its slit" and press or force this slit apart till it cools.?? This helps the tabs grip the PCB better so it won't move!??
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Oh the bottom part near the PWR sockets and fuse F1...looks a little like corrosion on bottom half F1 and maybe around the base of the board...just check...if so get back I can help how to clean fix.?? F1 check it...looks dull on bottom upper pad.?? Just sayin, if it works, leave it.?? Lastly the motor sockets are wearing around the top plastic.?? Be careful plugging in Plugs as twisting trying to find the location lug, tears at the plastic.?? I do have "new sockets".....but not many (6) and these are not available anywhere, and i mean anywhere, unless you want to buy them by 10,000 lots.??
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Lastly the RV1/2/3/4 are looking slightly "been hot".?? They are to protect the the encoder lines.?? They are varistors and can go bad.?? FTM, if its running ok...leave them.? But if you get any runaway drive or drive issues...take them off or replace them. ?? V5.5MLA0805L.? Frankly I usually take them off (if they short out they can damage motor encoders) , but as said if you don't have any drive issues...leave them
Anyway...lets see how you go....the board isn't in bad condition just looks like some critter been using it as a play area around the Serial port and socket!?? Thanks for great images...they really help
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Cheers
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Get back if any help needed, only happy to do so
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Brendan
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Re: RS-232 interface IC and RS-232 port replacement part numbers?
Thanks Brendan.
I was curious about the black pin 8 too. That¡¯s not just a photo oddity. The Gemini-2 FAQ showed that as an NC pin, so I wasn¡¯t overly concerned about that specific pin. It is strange though. I didn¡¯t see any melted SMC case bits anywhere, so I¡¯m not sure where the black came from.
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The 5520257-2 is the exact part I was eyeing last night on Mouser. Thanks!
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That's good to know about the CPU. It looks like there are still some on eBay available.
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I'm leaving on a business try today, so it'll be mid-week before I get back to this. I'll order the MAX, RJ22 port & a pile of caps then do some more testing when I get home.
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I took some more pix of the PCB last night, but only the top. I was planning to put it under a USB microscope to inspect further. There are a few grass/dirt/dust bits I need to clean up on the PCB. Here's a link to the current pictures (oddly, Imgur gave me a "this may contain erotic material" warning after I uploaded those images....erotic PCBs...hmmm.) https://imgur.com/a/xrre6Q5
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Thanks!
Bryan?
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Re: RS-232 interface IC and RS-232 port replacement part numbers?
you can use a usb to rs232 ?converter (install it¡¯s driver) and like terra term or to communicate with the Gemini and see if its working?? It usually loses one line the Rx or Tx
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Send basic commands ASCI, HEX or Echo commands...or even listen to port data in hex or serial
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But the IC is easily available but i do ask what is pin 8 looking "black"??? Is it a photo effect.? The PCB does appears to have some mottled or water moisture marks.? Definitely needs a good clean up....and clean corrosion from small traces, by scrubbing off PCB resist...coat with solder and coating with UV dry PCB resist.
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Do check the rest of the PCB
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There are many vertical 4P4C jacks but this one will do.? TE (previously AMP) mrn 5520257-2, flanged 4P4C plastic thru hole socket RJ22, .? Digikey
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You can see plenty that will fit. . Just unshielded, Rj22, 4P4C vertical with or without panel flanges.?? You can see the ones that fit, l.?
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Lastly RS232 also is CPU related and yes I have seen these go bad.?? They go from U6 pins 11/9? to pins 71/72 of CPU.?? Pin 9 (R1 out) to pin 71.? Pin 11 (T1 in) from pin 72 CPU.?? U6 pin 8 (R1in) comes from serial socket pin 3.?? U6 pin 13 (T1 out) goes to serial socket pin 4.
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Test the caps by using a multimeter across them.? then reversing the leads...you get a very short "tick sound"
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Use plenty of flux...I guess you are ok at SMD ICs R&R....as these IC pads lift easily.? U6 is an MB3221 or ICL3221 in SSOP16 package for this version, make sure its SSOP16 or SSOPW. ??? Send some other PCB pics and underneath...so i can check the PCB condition.? If you want
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cheers
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Get back on how you go
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Brendan
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RS-232 interface IC and RS-232 port replacement part numbers?
Hi everyone,
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It looks like I have a dead RS-232 chip and I'm planning to replace it. For some details on this, my 2007-vintage Gemini-1 G11 started acting up a few days ago. It intermittently stopped responding correctly to slews commanded through the ASCOM driver, got worse over the night, and now has issues even connecting through the RS-232 port. I first tried different cables, then computers, USB-to-Serial adapters, swapped the battery, cleaned the RS-232 port's pins, etc. When I can get it connected to a computer, it will respond to ASCOM driver hand controller movements, but will not accept any slews to RA/Dec.
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Per the Gemini-2.net Gemini 1 FAQ, I tested the voltage across C21 and it shows near 0 (even immediately after waking it up by requesting GPS coordinates). Voltage across C19 is 5.0. Seems like a textbook failure.
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Also, I'm thinking of replacing the RS-232 port at the same time. It seems to be working fine, but there is a little corrosion that I couldn't clean up. Does anyone have a good part number for that?
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Thanks for the help,
Bryan
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Oops,
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As an OG star hopper living under the L.A. light dome the Nexus DSC is a great solution IME.?
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Chip Louie Chief Daydreamer Imagination Hardware?
? ?Astrospheric - South Pasadena?
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On Mon, Aug 5, 2024 at 02:09 PM, Teran, Mark wrote:
Hi everyone,
Would anyone recommend a DSC system, perhaps Nexus, that would work with Losmandy drive motors? I think I might prefer that to Gemini 1 go-to. Is one in better touch with finding objects, as I always had with star hopping, than go-to.
Mark
Whittier, CA
Hi Mark,
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For visual work I have always MUCH preferred to use Losmandy mounts because they were designed? to be used as PUSH-TO mounts. When a Losmandy mounts is combined with Astro Devices Nexus DSC this is the ultimate visual mount setup IME.?
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The Losmandy Porter slip clutches are so much more elegant in use. With a polar aligned, well balanced mount and the clutches free you simply push the telescope tube to an object. You can use a visual finder or DSC and the RA drive will take over and track once you stop pushing the telescope. If needed you can use the hand controller to center objects for high magnification observation.?
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This way of observation is so much nicer than having to keep flipping levers to engage and disengage the locking clutch levers as all commodity mounts require. The problem with disengaging the clutches on virtually every commodity GOTO mount is that the computer loses track of where the mount is pointed. The next GOTO is up to you to manage manually or you will need to sync the mount by doing an 2 or more star alignment again.?
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I have been using the Nexus DSC for many years on my Losmandy mounts. I used to use it on my Gemini equipped G11Gs and GM8Gs but finally found a NOS early 90s GM8s for use as a lightweight tracking mount that can carry any of my visual scopes.?
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Chip Louie Chief Daydreamer Imagination Hardware?
? ?Astrospheric - South Pasadena?
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Re: Worm phase changed, Gemini I L4
Thank you Paul Kanevsky and Benjamin White.? I'll keep my finders crossed my hardware is in good condition and start with a new PEC curve.??
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Paul Kanevsky
David C. Partridge
Chip Louie