First Light with Meade LXD75 SN-10AT UHTC
Posted 26 November 2005 - 06:16 PM
It has been awhile since I have been able to post on the forum let alone get out and do what I love best; observing the heavens. Thanksgiving night I had my first chance to take my LXD75 SN-10AT out for the first time (even though I had gotten it over a month ago). I have upgraded a few items on it like the finder scope (Right-Angle Antares 7 X 50mm) and added collimation knobs instead of the three screws for secondary adjustment. I had ordered the JMI Focuser upgrade as well but it is still backordered so for now it still has the stock focuser. I also have to say that I had seen an SN-10AT when they first came out and there are a few differences between that version and this one. On this version the tripod legs are beefier and there is an included extension to the counterweight bar, and I later found out that this extra extension is needed, especially once you load a dew shield and heavy 2'' eyepieces on the scope. So I took this as a positive that Meade is listening to those who say that the SN-10 is pushing the limits of the mount.
Now for the good part; I setup the scope during daylight so I could align the finderscope and train the drive trains not to mention having a little extra light does not hurt when setting it up for the first time in general for such pre-observing practices such as balancing the OTA. Once I got the finder aligned and the drives trained I left it until dark. Seeing conditions were not that great, transparency was about a 5 and there was a little high cloud cover here and there but overall it was decent enough to observe. I went out a couple of hours after darkness settled in and tried to use the Autostar GoTo feature by telling it to slew to Mars. Well it did not find Mars but it did slew to its general area. This is my first time using GoTo so I am sure that I am not doing something totally right in the aligning procedure so do not take it as a negative that it did not pin-point Mars. I just wanted to test it and for me it did ok by finding the general area it was in. The slewing of the drive train at high speeds is a little jerky at times (especially when it starts to slew) but at slower speeds (6 or less) there is no jerkiness or backlash at all. This impressed me a lot as I also have the Orion Sky View Pro Mount Drive Axis and it causes the mount to shake and has some backlash in it occasionally even when just tracking at slow speeds. Overall the stability of the LXD75 mount impressed me being that I have heard a lot of negatives about it. I have the mount on vibration suppression pads on my wooden deck and throughout the entire observing session I hardly noticed any shakiness whatsoever and there was even a little breeze going on to boot. I do have to say that the stability of the LXD75 mount blows away the stability of the Sky View Pro mount with an 8’’ OTA on it. I cannot even use my Sky View Pro mount on my deck as it shakes too much even with no wind.
I started the observing session by looking at Mars with the supplied 26mm 4000 series eyepiece. I do have to say that the image did impress me initially but getting it into precise focus is a bit of a hassle. The focuser just does not seem precise enough for fine focusing as many others have found out already. To me it seems like the gear sizes are to large and this maybe the reason why coupled with the fact that whatever grease they are using to lubricate the drawtube is sticky and not really lubricating that causes headaches when trying to get that last bit of focusing precision. I did have to adjust the focuser a bit as it was very tight out of the box. When using the supplied 26mm eyepiece anything in it has to be right in the center of view to look really good. It seemed to me that it had a smaller FOV than it should have as anything on the edge or just in was hard to get to look decent. I then tried my 15mm Orion Expanse eyepiece and what a difference it made. It really brought out the optical quality of this scope which I must say really impressed me. I could see definition on Mars even with just 15mm that I have never seen before. The rest of the night I just slewed around on my own looking for DSO’s, mainly globular clusters just to see how bright they compared to what I have remembered seeing with my 10’’ Celestron Starhopper. I was really impressed overall as I when I even went down to 10mm the brightness I was obtaining was nothing like I ever remembered obtaining with it before on any scope I have used it with. Overall the views I obtained were worth the price of the scope alone. I am not an advanced enough observer to give comments on what details appeared or did not appear (I am still learning about all the DSO’s) but I do have to say that compared to my 10’’ Celestron Starhopper the views obtained with this scope are much better even in the average seeing conditions I had. My observing session only lasted a little over an hour as clouds rolled in and covered anything worth viewing.
Overall I do have to say that I have found my new “baby” (until I get my C11 at the door) and I am sure once I get some better focusing precision that the observing pleasure will only increase. I just purchased a helical focuser today so if seeing conditions are good tonight I will give it a go using the helical focuser.
Excellent Optics – Brightness and clarity are nothing like I have ever experienced.
Excellent Drive Train System – Slewing is overall very good and free of backlash and vibration.
LXD75 Mount - Even though some may disagree I have to say the mount is a positive over my experience with the Orion Sky View Pro mount.
Illuminated Polar Finder – Even though I have not used it yet, this being included is a nice add-on.
Nice construction and finish to all components excluding the focuser.
Focuser – Very hard to get objects finely focused, decent if one uses a helical focuser in combination.
Supplied Finderscope – I do not know what Meade is thinking here but I could never use the supplied finderscope due to the large size of the OTA in combination with being used on an EQ mount (height), a right angle finderscope upgrade is a must.
Supplied Eyepiece – I found that objects must be centered to look decent, anything not centered was impossible to get focused.
Instruction Manual – This could be improved some as for the beginner to intermediate some instructions are hard to understand or vague. (This is why we have Cloudy Nights though.. )
Posted 27 November 2005 - 01:49 AM
The best sight of the night was the Orion Nebula (M42). I was blown away at how much detail showed up, even with the instability due to the wind. I could easily make out the detail between the gas clouds and the dark background. I started viewing it at 35mm but went all the way up to 6mm with no problem at all with not enough light (and I live in a pretty light polluted area). Of course the 6mm view was dimmer but the detail that showed up was still stunning. The Orion Helical Focuser made a huge difference in getting that last bit of focusing precision especially with the higher power eyepieces.
The only downside like I said was the instability of the mount in the wind. I would say the wind was coming in at about 10-15 MPH when the OTA would shake. I do not know what is acceptable for viewing in regards to wind speed so this may have been to much to observe.
Overall I am still impressed with the entire package and the optical quality still has my jaw dropped.
Posted 27 November 2005 - 07:20 AM
Posted 27 November 2005 - 10:42 AM
Nice writeup of a nice scope. Your experience with the LXD75/SN-10 combination mirrors mine very closely, from the bright and sharp views all the way to the wind shake.
You didn't mention calibrating the motors, which you should do before training the drives. If you initialize properly for your location, time, date, and daylight savings time status, you'll find go-to accuracy to be quite good.
Good alignment will help with getting targets in your field of view. You may have to adjust the motor drive gear mesh with the driven gear to provide smooth slewing. If you do, be sure to recalibrate motors and retrain drives.
It sounds like you'll be enjoying your scope for a long time to come. Clear skies!
Posted 27 November 2005 - 02:08 PM
You may have to adjust the motor drive gear mesh with the driven gear to provide smooth slewing. If you do, be sure to recalibrate motors and retrain drives.
I am still learning all about the alignment procedures as you can tell from my experience when trying GoTo to Mars.
When you say I may have to adjust the motor drive gear mesh is there instructions somehwere on how to do this? Thank you for letting me know about this!
Posted 27 November 2005 - 03:48 PM
It's been discussed in the LXD55 and LXD75 mailing lists on yahoogroups.com. You might also find some tips on astronomyboy.com's website in his CG-5 teardown. Hope this helps.
Posted 28 November 2005 - 01:02 AM
I carefully looked at the slewing\tracking of the mount tonight and noticed that my RA did have backlash when moving downwards so I took the motor assembly out and tightened the two outer allen screws below the worm gear assembly BUT it was not enough to to get rid of the backlash.
Here I found that the entire RA assembly seemed like it was loose a bit as it had a hitch in it even though the RA lock lever was locked. It was just a small hitch but this was causing the backlash. The issue seemed to be that whoever installed the RA worm gear assembly installed it to low, the worm gear was way to easy to move and when moving the gear in an upward direction it was skipping (of course this was with no counterweights, etc.).
So I had to loosen the two allen screws holding the worm gear assembly and move it up towards the RA gears a bit. Not to much though because I wanted the two allen screws on the bottom to finish off the pushing the worm gear assembly closer to the RA drum. I tightened the two allen screws on the bottom of the worm gear assembly just to the point that it was tough to turn the worm gear then I tightened the middle one to make the worm gear a little easier to turn.
The worm gear was way to easy to turn before I did all this, to the point that the upward RA was skipping (not enough gear contact between the worm gear assembly and the RA gear drum). Now the worm gear it is tougher to turn but no more skipping, no more backlash, and no more hitching RA assembly!! What is funny about the hitching RA assembly is when I first put the OTA on the mount when assembling everything for the first time I had thought the OTA was going to fall off on the other side of the mount (like I had not tighted the dove tail screws enough). It caught and stopped moving and ever since then I was wondering what caused that to happen.
Thanks again for pointing this out about the gear assemblies. Hopefully I won't have to do this to often as it is no fun taking all the OTA and all the counterweights off, adjusting the worm gear assembly, and then putting everything back on to test it.
Posted 28 November 2005 - 07:48 AM
Adjusting that once should be all you need to do. The LXD75s are pretty reliable once you do the QC work that Meade should have done. My LXD55 and LXD75 both had to go back under warranty because of slipping gears on the drive motors. At the time, I was new to EQ mounts and didn't want to open them up myself. In retrospect, and knowing about common problems of LXD55/75 mounts, all I had to do was tighten up the set screws holding the gears to the drive motor shafts.
Let me know how your go-to works after your modifications. Go-to accuracy depends on your alignment accuracy, but the worm gear sloppiness sure couldn't have helped.
Posted 28 November 2005 - 10:55 AM
My only concern with adjusting the "tightness" of the worm assembly to the RA Drum is just how easy should it be to rotate the worm assembly. There is differing opinion on this out there, some say it should be easy and some say it should be tight. Though the overall consensus out there is that it should rotate with no binding occuring over the entire axis of movement.
To me it does seem kind of tight, but right now it is at the point where the is no more skipping and the RA assembly hitch is gone like I mentioned before. Anymore loose and the skipping and RA assembly slop (hitch) occurs again. At max speed (9) the OTA assembly does bounce a tiny bit when movement stops but I hope this will go away once I break it in more. Overall the sound of the motor is good at high speed, a little whirring but nothing different than before, and at low speed (5 and below) and during tracking it is nice and quiet so I think it is ok with the tightness.
Posted 28 November 2005 - 09:14 PM
I keep my mounts in quiet slew only, specifically to avoid that bounce you mention. I got a 26" counterweight shaft so I could balance my SN-10 with only 20# of weights, but that increases the moment arm, so I use quiet slew.
If your tracking is smooth, that's what counts. I lean toward the "looser" worm drive school. It sounds like you're fine from the way you describe your clearances. You made it better. That rates a great big smile!
Posted 28 November 2005 - 11:51 PM
Ah, I never thought about using quiet slew, I will have to try that next time. Yep, it sure is better, I just worry not having the torque specs whenever adjusting any kind of gear clearance. I wish Meade would publish technical documents like we can get for fixing up cars or other electronics. I would be in heaven if that were the case as I am a major tinkerer. LOL!
Posted 04 December 2005 - 01:21 PM
I did not have any real problems with the shaky shakies with the mount, even though both scopes are definitely on the upper limit for the LXD-75 head. I have an Antares pedestal/pier that I will be putting the LXD-75 head on a little bit later on. That should stabilize it even more. I did notice balancing the OTA is a bit touchy with this mount. It took me several tries to get it to the point where I was happy with it.
Posted 04 December 2005 - 04:53 PM
Yep, my experience matched yours too a tee. The detail I saw in M42 and some other DSO's really threw me for a loop. I was not expecting that level of detail at all. The shakes with the mount only occurred when the scope was low on the sides and there was a good wind gust, other than that it never shook. I will also be putting the LXD75 head on an Antares pier soon so that should help like you mentioned.
I am going thru withdrawal not having it here this weekend, lol! Oh well gave me time to get more goodies for the LXD75 head (replacement bolts, etc.) and other accessories for the OTA from Scopestuff.com.
Posted 04 December 2005 - 09:14 PM
Posted 05 December 2005 - 04:36 AM
The SN 10 inch is a fine instrument, and once you have learned all the little tricks that make the scope a comfort to set up and use, you will be amazed at what the scope can do beyond your 6 inch. If you could carry the 6 inch refractor on the mount, then this scope should ride at least as well. I don't know the setup re the length of the dovetail bar that mounts your SN, but a clue is that balancing longer tubes via a long dovetai setup is much nicer than trying to balance the scope by sliding the tube back and forth (I have an MN66 and am going to make changes in my mounting-balancing hardware for this reason). Secondly, I just purchased a single felted retaining ring that holds the scope in place in front of the ring assembly so your can rotate the scope without it scooting backward for comfortable viewing when you find your focuser and finder in wierd positions. And, of course, you will want to practice getting your scope in precise collimation before every viewing session. Once learned, you will not mind doing it and it will beome routine. One last item is the finder. I have four straight-through finders stored somewhere. I just can't understand why anyone would want to crane their necks to find things that are backward from the true views. I use the Orion 9 X 50 right-angle, correct image finder on my MN66, even though it barely fits the tube rings that were on the scope. It makes finding a pleasure rather than a chore. Good luck with your new scope. You will find that mirrors do wonders.
Posted 05 December 2005 - 09:19 AM
My 8 inch newt is not usable right now. It needs a mirror recoat. It was handed down to me from my grandfather and is about 40 years old. I am trying to restore it.
Posted 05 December 2005 - 11:02 PM
I just can't understand why anyone would want to crane their necks to find things that are backward from the true views.
Exactly, I purchased an Antares RA Finder right when I got the scope as I laughed when seeing the straight-thru on there when first setting it up. Whenever I see that "Hummer" commerical with that short fellow making the suggestion to design it smaller I dream of a short fellow at Meade making the suggestion to put an RA finder on the SN10.