Re: G11 Mount Not Tracking Correctly
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Sorry to read of your headache getting proper performance. It seems that your G11 has a very light payload, as your lenses seem very light compared to the strength of this G11 mount.? So? something is mis-set... let's try a checklist to "round up the usual suspects" to steal a line from Casablanca. 1. COLD BOOT your Gemini.? ?You have not mentioned this, so I'll put it first on the list.? Remember that the Gemini always reads its Model values and offers first to Warm Boot.? The Model parameters are a bunch of corrections to a perfect mount.? The values consist?of error corrections for polar alignment, counterweight bar flex, errors in AZ and ELevation.? Warm Boot sounds like a great idea, if you have not moved anything.? But as soon as you shift anything...the Elevation knob, the AZ rotation, to polar align, the prior model data is worthless?and even worse... the mount will be making the wrong corrections.? So when any pointing goes awry, first suspect the Model data is bogus.? Do a Park at CWD, torn off the Gemini, and reboot it in Cold Boot mode. 2. Is something slipping?? It sounds absurd that such a strong mechanical system could ever slip, but if you've ever tried to drive a car with a worn out clutch, you know the problem.? The clutch system uses thick plastic disks, one each in RA and one in DEC, to hold position.? You can clean these disks rather easily, but it means removing your scope first, then counterweights and bar, then pulling out the DEC axis from the RA axis, then pulling out the?RA axis from the mount head.? Then yank out the clutch disks, cleaning them and the metal mating surfaces in something like isopropyl alcohol. while those 1.25 inch shafts are out, it's sensible to see if you can rotate the needles of the needle bearings with your finger.? If those are sticking, due to "gummed up" old lubricant, it is time to use some nasty degreasing chemical to remove all the old grease. [Nasty means it must be done outdoors with rubber protective gloves and a face mask...something like an automotive degreaser like Berryman B-12 works well...you spray in some of that and catch the residue in a metal bucket...this stuff will dissolve a plastic bucket.? ?Just be very careful.]? ?I'll add that I make a high friction clutch disk for our mounts that holds much better than the stock plastic clutch pads and also retards or prevents oil migration on to those plastic and metal clutch surfaces.? Let me know if you need such things.] 3. Other things can get loose and move or shift.? Be sure to tighten down your RA and EL hold down bolts after polar aligning!? The stock thumbscrews are 3/8-16 thread.? They have only got flat washers under the bolt head.? When you loosen those AZ bolts, the mount head is only held by a central rotation bold under the middle center under the mount head.? That likewise also only has a flat washer...or even No washer at all.? So I put in (you guessed it) 3/8 Belleville spring washers bounded by flat washers in those 3/8-16 bolts locations.? Then when you loosen the AZ or EL, the bottom bold is always being held with some spring force in the bottom center, and the AZ bolts also have some now-adjustable force to hold the AZ in position.?? 4. I found one of my tripod legs was slightly?slipping?length over time.? The problem was the heavy weight of my scope, and the huge hand knobs that hold the legs position started to loosen over time and temperature.? Be sure those legs adjusters are really tight.? This was the last thing in the world that I ever suspected...in your case, with such? a light load on the mount, it seems unlikely but I'll leave it on the checklist.?? 5. Others already mentioned that the data entry for Latitude and Longitude use a decimal point entry.? But it is NOT a decimal point!? It is instead a European style comma!? So you enter Degrees.Minutes? ?not Degrees.Fraction.? ?(If your minutes are near zero, of course, it will not matter.? I can't imagine what devilish havoc is caused if you enter something?over 59 in the degrees entry...maybe you can't?? Something like longitude "122.97" ?? )? (No... IO won't try that to see!) 6. The polar scope...? ?this is a wonderful invention.? But it is prone to difficulty.? The Losmandy style polar scope is better than others like the one in the Orion Atlas/Synta EQ6... but none of them are perfect.? The problem is that the glass "reticula" is held by 3 tiny metal screws that must always be somewhat loose from the round glass reticule plate inside.? If too tight,the glass will get cracked.? As you rotate the RA or the plasr scope around to get the stars lined up,, the glass plate can shift and mess up the visual point of the NCP (or SCP) point.? So I use a drift align to follow up and check polar alignment?before deep sky imaging.?? There are other polar alignment gadgets these days that are highly praised.? I don't yet have one but it's on my shopping list.? Another local group member came by to pick up a Gemini-1 I just fixed for him, and he told me he has some recommendations for this... as others?on this forum have praised.?? 7 As Paul mentioned in his following email, beware of GPS data.? I always hand enter UTC time, not local time.? [The entry coding is:? YYMM.DD?HH:MM:SS? like 2008.18 20:15:59? ] you mentioned that you checked and found your local time was UTC -5 hours.? That's nice to see, but given the crazy way daylight savings time dates get changed these nutty times, always enter only the UTC time (from a website giving the current UTC time of course).? And if your Latitude and Longitude are correct, the local sidereal time (LST) will be correct.?? 8. Related to this is the problem with some GPS units (namely older GPS models don't' read the latest GPS codes right and get the wrong UTC time or maybe wrong position data.? There was a whole?discussion of this problem... leading some to say their old GPS unit could not read the latest satellite information being sent.? Anway, the bottom line is:? also suspect GPS provided information and double check that.? ? 9. As Paul mentioned (in the email following), you?may easily have left your Gemini?in some tracking mode like Lunar, or maybe Solar (we have sunspots again, yeah!).? So double check the tracking rate is really Sidereal.?? That's about it... try this checklist first, and let us know if the problem went away! All the best, Michael On Tue, Aug 18, 2020 at 2:43 AM Jamey Jenkins <jameyljenkins@...> wrote:
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Michael Herman