Last updated: 22 August 2007
This page is for user comments and information of a general nature or items applicable to all LXD55 and LXD75 models. If you have any comments, suggestions, questions or answers to questions posed here, e-mail them to me and I'll post them. Please use an appropriate Subject Line on your message. Thanks.
Subject: Polar axis alignment - Polaris - Kochab method Sent: Wednesday, August 15, 2007 14:46:59 From: Simon Harding (email@example.com) I`m just upgrading my 10"SN telescope with a new LXD75 mounting - I hope it`ll give greater stability and better tracking when appropriately aligned on the NCP ? I found your article about aligning Polaris - Kochab along the counterweight bar and setting the Polar axis telescope crosshair parallel . The thing that puzzles me is that the diagram shows the alignment as : NCP ------------ Polaris --------------Kochab Actually the alignment is : Polaris -------------- NCP --------------------- Kochab . Shouldn`t the crosshair be rotated 180deg from the diagram as shown here? how do you easily adjust thescrews on the polar scope collar - will I need to do this when I get my new LXD75 mount ? regards Simon HardingMike here: I assume you are referring to Mark Jordan's article. I'll let him respond. As to aligning the polar finderscope, essentially it is the same as with your older LXD55 mount, assuming you even need to adjust it.
From: M. J. The Madjordainain (firstname.lastname@example.org) This issue has been brought up before although more pointing out that doing the way it is outlined puts Polaris on the "wrong side of the PAS". Folks forget that the Polar Finder Scope is a straight through refractor and therefore the view is flipped actually putting the NCP & Polaris or Polaris & the NCP however you prefer to say it in the correct position and order! All the aligning of Polaris & Kochab along the CW bar is to do is to establish a straight line from Kochab to Polaris, because the NCP will always be along that line too. The Kochab's clock method of quick alignment is not my "invention", it's been around for a long time. The simplified method for the LXD75 and similar GEMs with a PAS is a way to get it to work for the relatively small FOV in the Polar Finder. Folks who ask this question have also obviously not yet attempted the method, as it works, providing you have accurately collimated your PAS to the R.A. Axis of your mount. Trust me when you get your LXD75 after collimating the PAS (that's the painful part) try it and you'll see it works pretty fair. You'll still need to drift align/check it for long exposure photography, but if everything has been done correctly you will only need very minor adjustments. Remember the only thing aligning Polaris and Kochab up on the CW bar is for is establishing a straight line in the correct angle or "clock" position from the NCP to Polaris. If you continued along that same straight line in the true direction of Kochab, you'd find Alkaid is also right along that same straight line, it's a great, quick, easy way to get things lined up correctly. For a better explanation of the Kochab's Clock method read the following article by Dr. Clay Sherrod, the simplified method for a GEM with a PAS is just my way of using it in conjunction with the relatively smaller FOV of the fairly standard economy PAS. http://www.weasner.com/etx/ref_guides/polar_align.html Read Dr. Sherrod's article and method to understand the Kochab's Clock system, it will all make better sense. It was after reading his article http://www.arksky.org/Kochab.htm that I came up with this way of making it work for the GEM PAS. As for collimating your LXD75 PAS Andy Raiford has an excellent video on his Shot Glass Astronomy site detailing a good method for collimating/aligning your PAS. He uses an Orion SVP GEM, but the method is still exactly the same for the LXD75 PAS, and if you intend to use the Simplified Kochab's Clock for the GEM method you'll need to align the long line with the Polaris home circle on it to the CW bar. It doesn't need to be dead on, super accurately in line with the CW bar, but the closer the better. http://www.andysshotglass.com/PolarAlignmentScope.html Be careful with the OEM Allen head PAS alignment screws, the heads strip out easily. Your better off to spring for a set of thumbscrews to replace them with to do the collimating, the thumbscrews make the whole process a lot easier too! Clear Skies and have fun with your new LXD75! From the mind of The Mad One; Mark Jordan The Star Deck Observatory "Oh my God! It's full of stars!!" http://cleardarksky.com/c/Indianapoliskey.html (The Indianapolis, IN Clear Sky Clock)
Subject: LXd55 mount Sent: Monday, August 13, 2007 04:29:28 From: Colin Martin (email@example.com) I have just acquired a LXd55 mount with autostar and am having difficulty setting it up. Firstly, in the polar home postion, which side of the scope should the dec motor be? One of the little arrows seems to be missing off mine so I am not sure. I thought it should be on the west side but I have seen an a photo showing the east side. When on west side and I setup autostar using suggested arturus and vega on easy alignment the stars are outside of the 26mm eyepiece view.. Also the RA setting circle seems to be way out, the dec reading is okay. . I set the ra circle for 2 hours on polaris Thanks Colin (West mids UK)Mike here: I have used the LXD55 with the DEC motor housing on either side, worked fine both ways. If you are using the AutoStar you don't need to use the Setting Circles; when using Setting Circles, the RA one has to be adjusted for the current time. If the first alignment star is way off, it could be that the Polar Axis is not pointed towards True North, the Latitude setting is off, the AutoStar has the incorrect settings (Date, Time, Daylight Saving, location), or that the telescope optical axis is not aligned to the polar axis.
Subject: how does AutoStar determine how to move the telescope? Sent: Sunday, August 12, 2007 10:05:55 From: Theodore Rafferty (firstname.lastname@example.org) This might be a question for Dick Seymour. I would like to know how and where the Meade LXD75 determines how to move the telescope in each direction of slow-motion. Under high magnification, if I move a star using the hand block in one direction of RA it will move and stop as soon as I lift my finger from the hand block button. But when I move it in the other direction, the speed is slightly slower and the star will continue to drift in the same direction slightly after I lift my finger from the button. I believe this behavior is causing an auto guiding problem that has started in the last month and a half. Using either AutoStar or PHD Guiding, I can see that the telescope is being moved rapidly slightly back and forth in RA enough to cause trailing on my images. I am using a DSI as the guiding imager with a 3x Barlow on a 700mm focal length guide scope. And the guide scope is mounted atop a LXD75 8-inch, f/4, SN with a DSI Pro 2 mounted to it. I have been using this setup for the last eight months and have excellent results until recently. Something has changed. Because of the different way the telescope is being move in RA depending on the direction, I believe the auto guiding calibration is determining a poor scale and when auto guiding it is under correcting in one direction and over correcting in the other. From the software side, as I said above, the problem is apparent when using the AutoStar or PHD Guiding software. I have downloaded three different versions of AutoStar to my hand block and the problem occurs with all of them. And I have done a Reset of the hand block. From the hardware side, I have checked that all the gears and encoder wheels are tight. I have taken the mount completely apart, cleaned, and regreased it. I have opened both gear heads on the motors, cleaned and regreased them. I have switched the two motor blocks on the mount, thus switching the RA and Dec motors, encoders, and the circuit boards mounted on the side of each block. I have also changed the balance in RA of the mount so that, in one case, it is slighting counterweight heavy and, in the other case, it is slightly telescope heavy thinking that the balance might affect the motion in RA. After making any change to the mount, I always do a "Calibrate Motors" and "Train Drives". None of these changes affected the problem (neither making it better or worse). I don't have a spare hand block and don't want to spend the $199 for a new one unless I am sure the problem is with the hand block (my scope is 2.5 years old, so well out of its warrantee). I am hoping that if I can understand how AutoStar is controlling the motions of the mount that I might know what part(s) to focus on. Ted RaffertyMike here: I doubt the AutoStar is defective. You may be seeing a normal effect of a non-precise polar alignment with the LXD75. You could also be seeing "periodic error", which you can correct for using the PEC mode of the AutoStar. You might want to try that.
The slight motion back and forth is very rapid (will trail star in a one-second exposure) and not the long period of the RA periodic error. And the rapid motion is only apparent when auto guiding. I have checked the polar alignment and it is very good. The difference in the behavior of the RA slow-motion that is dependent on direction is still my main concern, which was why I was asking about details of how "Train Drives" might affect that behavior. And as I have pointed out, the setup has produced excellent results until just recently. Thanks for your quick response. Ted RaffertyMike here: You could adjust the "percentages" (info on the Helpful Information: AutoStar Info page). You could also try overbalancing somewhat in the opposite direction (or the same if opposite doesn't help) to see if that helps. TRAIN DRIVES just counts pulses from encoders for a specific amount of travel.
I have adjusted the "percentages", as well as the "tracking rate". And as I mentioned in my first e-mail , I played with the balance; trying it slightly heavy on the counterweight side and then trying it slightly heavy on the telescope side. Nothing helped. I know that "Train Drives" counts the pulses from the encoders, but I am wondering if that would explain the behavior I am seeing (the difference in the way the telescope moves east and west) and where the calculations are applied; in the hand block or on the circuit boards mounted on the motor blocks.Mike here: There is some "slop" (backlash) in the movement. That is why some people recommend making the last slew to an object to the west.
The RA clock drive serves as a nice "slop" remover, if you have the telescope balanced correctly. But when doing the "Train Drives", the RA clock drive is turned off.Mike here: I was referring to slewing to an object during observations, not TRAIN DRIVES. Sorry about the confusion.
The problem is affecting every object I try imaging and just started in the last month and a half. In the 2.5 years I have been using the LXD75 for imaging, I have never had the problem until now. Something as changed.Mike here: Since you have reloaded the AutoStar and done everything you could there and since you have checked the motors and gears, I'm not certain what else is left to check. You might try adjusting the axis friction bolts.
I am not sure what you mean by the "axis friction bolts". Maybe you are referring to the axis clamps, which I have adjusted. At this point, I am open to any suggestions. Once again, I am grateful to your quick replies.
I was looking through the numerous entries in your very useful web site and found one that does a pretty nice job of explaining how the "Train Drive" works: http://www.weasner.com/etx/autostar/opt-train.html One comment caught my eye about the "Calibrate Motors" step: "The 'CALIBRATE MOTORS' stage is quite important - especially at any point where you switch to a different power source for your scope." I wonder if I am having a power supply problem. It is worth checking.Mike here: Might be a power supply problem; have you tried an alternative? As to adjusting the friction bolts, the RA ones are on opposite sides under the caps next to the polar finderscope cover cap and the DEC ones are in the mounting rail slot (which you can see with the telescope OTA and its mounting rail removed from the GEM head).
I don't have a spare power supply. I used contact cleaner on the connector and socket for the power supply and will see if that helps. The friction bolts you describe are what I assumed where just mounting bolts, where the two bolts next to the polar-finder scope cover cap hold the Dec housing to the RA shaft and the two bolts under the scope mounting rail slots hold the end piece onto the end of the Dec axis. When I took the mount apart last week, I removed these bolts to take things apart. They were all tight when I removed them and when I put the mount back together, I tightened them again. I did not notice any change in the friction to rotate either the RA or Dec axes. It appears to me that you would not want these bolts to be loose. I'll have to check your web site to see if there is any description of adjusting the friction bolts. Thanks for the information. TedMike here: Have you tried a different set of D-batteries?
Subject: DEC GEAR SET SCREWS Sent: Saturday, August 11, 2007 08:14:31 From: Pete Sherman (email@example.com) Hi there I'm having a little trouble with the set screws on the Declination gears on the LXD 55 mount. I have tryed a 1/16"& a 1.5mm Alan Key and they both seem to large could any one tell me the correct size of Alan Key (hex wrench) I need. Many thanks, All the best. Pete.Mike here: I know that I used a standard size when I tightened mine a few years ago but I don't have a way to measure it. So I'll let Dr Clay Sherrod respond.
From: P. Clay Sherrod (firstname.lastname@example.org) The screw size is a 0.05" standard. Dr. Clay ------------- Arkansas Sky Observatories Harvard MPC/ H43 (Conway) Harvard MPC/ H41 (Petit Jean Mountain) Harvard MPC/ H45 (Petit Jean Mtn. South) http://www.arksky.org/
Subject: LXD 55 latitude adjustment wobble point Sent: Wednesday, August 8, 2007 12:56:55 From: Walsh, Kevin @ DISPLAYS (kevin.l.walsh@L-3com.com) I was wondering if you knew of a way to tighten the bolt (?) that connects the sections of the LXD 55 mount at the latitude adjustment point. The entire scope wobbles about this point when it gets bumped. I think that if I could tighten this connection the wobble would go away. My scope is permanently mounted in an observatory, so now that the polar axis is set I don't need to be able to adjust the scope in altitude any more. See the attached sketch. Thanks. Kevin Kevin.L.Walsh@L-3COM.com Alpharetta, GAMike here: My LXD55 tripod is packed away (for a pending move) but I suspect that the covers will come off, allowing access to the axis. From there you could probably see what the problem is. Just how to get the covers off, I don't know. If you are successful and are willing, document the process with photos and I'll post it.
Subject: Re: LXD55 Mount Sent: Wednesday, August 8, 2007 03:49:50 From: Marco Santos (email@example.com) This how all end-up. I Contact Meade in Europe ( Germany ), and they will send me for free, all the RA Motor. Anyway, i talked to an electronic engineer on www.fixya.com , and im going to send im the other one for repair. Thats a cheap solution and i will be able to have a spare part for future accidents. Thanks for your kind help, and all the best for you and keep on your nice work. http://www.fixya.com/support/t178946-meade_lxd55_electronic_control_panel Best regards, marco
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