Jump to content

  •  

CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.

Photo

Review: Meade LXD75 6" f/5 Newtonian OTA

This topic has been archived. This means that you cannot reply to this topic.
28 replies to this topic

#1 hottr6

hottr6

    Skylab

  • *****
  • topic starter
  • Posts: 4171
  • Joined: 28 Jun 2009

Posted 11 August 2012 - 02:39 PM

I've not seen any reports on this Chinese-made 'scope in CN. So here goes my mini-review. I'm pretty new to this so be gentle!

Inspection: I was after a RFT grab-n-go to complement my main instruments, and happened upon this used Meade LXD 75 6" f/5 Newtonian OTA. The deal was done and I soon received a Meade box. The 'scope appears to be well made with a lot of heft to it. No doubt the welded tube has something to do with it, and it is nicely painted with a slight pebble texture in a pale cream color. The tube end cap is a solid piece of metal. The split-rings fit well and are easy to use. The finder is very clear and accurate. The focuser is plastic, but looks and feels like alloy and is surprisingly smooth with no backlash, but there is some image-shift. Overall, this is a very attractive OTA. Collimation of the primary was OK, so I did a quick tweak of the secondary using a simple sight-tube. Not bad for surviving USPS.

Optics: I checked out the mirror with a Ronchi grating and it seems pretty good. Parabolic with a very slight turned-down edge, which appears to be the norm in good quality mass-produced mirrors. No other problems stood out, so I expect this mirror to be a good performer. Lots of coma is to be expected, but I am used to that in my f/4.5 with no coma corrector.

The views are heavily compromised by the big ugly plastic thing that pretends to be a spider. The vanes are 0.21" thick!! Even el-cheapo threaded rod vanes are no more than 0.12" thick, and the sheet vanes on my other Newt are 0.05" thick. The secondary holder measures 1.975" in diameter and holds an undersize-sized secondary of 1.8" (9% obstruction); I say undersize because the 9" from the secondary to the focal plane provides a fully illuminated field of 0.0", whereas a 2.15" secondary (13% obstruction) would be required to fully illuminate a field 0.5" wide (Mike Lockwood, http://www.loptics.c...iagonals.html).. What was going through Meade's head when they approved this design? Haven't they learned something from manufacturing telescopes for decades? Certainly no astronomer/engineer would have approved this, so it may have been an accountant. I can hear the Meade conversation now:

Meade Bean-counter #1: "Hey, I see on so-and-so company's website they are offering this OTA at $6.99 per unit less than our current supplier. It has a mirror guaranteed to 1/6 wave, 2" focuser and rings. Looks good too".

Meade Bean-counter #2" "Order 5,000 units and slap a LXD 75 label on it".

Handling: I spent some time with it at night and the stubby tube is a dream to handle on my small Polaris GEM though the 12.4lb heft of the OTA is a little much for the Polaris as I had to use an 11lb counterweight, and vibration die-out times are around 4 seconds. As long as viewing uses longer than a 12.5mm eyepiece it did fine. As a grab-n-go, I can easily carry the whole shebang, but it is a little on the unwieldy side. I have just a short walk from the workshop to the driveway, but no-way could one carry this up/down stairs. Bottom line is that this 'scope needs more mount than my light-weight Polaris.

Observing: Doing a star test was a bust. New Mexico is experiencing it's monsoon season right now and I was chasing bright stars through gaps in the clouds. I noticed that the in-focus images did not reveal anything overtly worrying, but the out-focus image was utterly destroyed by tube currents. I suspect the culprit is the mirror cell, as there is almost no way for air to move around the mirror. I waited over an hour but the mirror would not cool down. A fan would help things, or an alternative cell, or both!

At low powers (30x-60x) the views are lovely. Stars in M13 were just on the edge of being fully resolved. Low-power views of DSOs certainly beat my 4" 'fracs. Epsilon Lyrae was fully split at 160x but not 110x. This may indicate a better job of collimation is required.

Yes, there is coma, but I did not find it intrusive. My Meade 4000 and 5000 UWAs and HD-60 seem to keep it under control so that it was barely noticeable... I had to look for it to be aware.

Opinion: This is my first RFT (other than 80mm binos and a large finder) and I was a little disappointed in the experience. This may be due to the fact that I am not so used to such low magnifications, and most of my targets never need these multi-degree wide fields. When the New Mexico skies clear, I'll use it as an RFT among the Sag star fields.

Summary: It is a shame Meade dropped the ball on this instrument. The reasonable optics, good build and handsome looks are compromised by poor design. A longer tube enabling a low-profile focuser, smaller diagonal in a good spider with a well-ventilated primary cell would have made for a knockout little 'scope. Candidate for a make-over?

Attached Thumbnails

  • 5363524-MeadeN6.jpg


#2 jgraham

jgraham

    ISS

  • *****
  • Posts: 20118
  • Joined: 02 Dec 2004

Posted 11 August 2012 - 05:01 PM

Many years ago I bought an LXD75 N6. At the time you couldn't buy just the mount and the N6 was the least expensive way to go ($469 + $75 s/h). I used the N6 for about a year before replacing it with an SN6 from Meade's outlet store. The N6 was a good basic scope with an industrial 'spider' and an undersized secondary. I fixed that problem by extending the tube a bit to drop the mirror back and to pull the focal plane in a bit. for the price it was was nice scope.

My LXD75 N6 after a bitterly cold night of wide field imaging. Note the heavy coating of frost.

Attached Thumbnails

  • 5363703-Frosty.jpg


#3 jgraham

jgraham

    ISS

  • *****
  • Posts: 20118
  • Joined: 02 Dec 2004

Posted 11 August 2012 - 05:16 PM

This is my LXD75 in its younger days and a warmer night. I mounted the OTA from a DSX-90 shotgun. The OTA now serves as the guide scope on my LXD75 SN6. I hope to eventually remount my N6 on an altaz mount for observing satellites.

Attached Thumbnails

  • 5363721-LXD75-N6-DSX90.jpg


#4 dvb

dvb

    different Syndrome.

  • *****
  • Posts: 6734
  • Joined: 18 Jun 2005

Posted 11 August 2012 - 08:52 PM

Thanks, Shane and John, for sharing your experiences with this scope.

I had a Meade SN-8, which was optically very good, though the mechanicals were poor.

It does sound like Meade dropped the ball on this Newt. Too bad - a competently executed 6" f/5 would be nice.

#5 hottr6

hottr6

    Skylab

  • *****
  • topic starter
  • Posts: 4171
  • Joined: 28 Jun 2009

Posted 12 August 2012 - 12:56 AM

I spent the afternoon carefully collimating the N6. Turned out to be less than trivial, a side-effect of the spider-from-hell-designed-by-a-time-and-efficiency-expert.

And what a difference! We had a steady night tonight with a slight breeze. Perfect star-test images, in and out of focus, albeit a bit wacky from the 3 thick spider vanes. The Ronchi test was awesome, with perfectly straight and parallel bands. E1 and E2 in Lyra were easily split with a 7mm and increasing mag just added icing to the cake. The 13 mag star just to the east of M57 was easily seen with direct vision, and I could just catch the nearby 14.1 magnitude star when seeing really settled. Saturn would not show me the Cassini Division, though being low (about 25 degrees) in the West at twilight may not have helped.
M13 resolved into individual stars lining the "lanes", and it's central core looked like a pile of silver shavings heaped on black velvet.

My older Meade 4000 UWAs really shone tonight, giving nothing away to my Orthos, and managing the coma until about 90% towards the edge.

I was impressed with the optics tonight. I'd say that this mirror is very good to excellent.

#6 Locoman

Locoman

    Viking 1

  • *****
  • Posts: 781
  • Joined: 09 Mar 2009

Posted 12 August 2012 - 04:40 AM

Is This the same OTA? If so it looks like a pretty good deal for the price. In the Product Description they describe it as a Schmidt -Newtonian with a closed tube but I think that in error. They also sell the Celestron C6-N here which I got about a year ago and it is a very nice OTA. Very happy with it!

#7 jgraham

jgraham

    ISS

  • *****
  • Posts: 20118
  • Joined: 02 Dec 2004

Posted 12 August 2012 - 07:06 AM

The product description is wrong. It looks like it was cut'n pasted from the descrption of the SN/SC scopes.

#8 calan

calan

    Viking 1

  • *****
  • Posts: 805
  • Joined: 16 Jun 2007

Posted 13 August 2012 - 01:19 AM

And here is mine...

Posted Image

Antares RA finder, EV electric focuser, cam lever ring locks, full flocking, carry handle, etc. I wish it had a bit more light gathering; otherwise it is a fantastic little scope. Star tests are always excellent, and it provides some nice views.



Oh yeah... here is some of the LXD75 mount:

Posted Image

It's torn completely down at the moment for a complete rebuild and paint job. :grin:

#9 hottr6

hottr6

    Skylab

  • *****
  • topic starter
  • Posts: 4171
  • Joined: 28 Jun 2009

Posted 13 August 2012 - 06:48 AM

Yep, that's the same one. At that price, the optics are a bargain. For the price of a middle-ground eyepice, you can have a really sweet 'scope.

I'd suggest a CG5 mount for this 'scope, or one of the heavier alt-az rigs. YMMV.

#10 hottr6

hottr6

    Skylab

  • *****
  • topic starter
  • Posts: 4171
  • Joined: 28 Jun 2009

Posted 13 August 2012 - 07:01 AM

Agreed that the focusser, despite my original observation was quite nice, is quite poor with the drawtube being unable to maintain linearity throughout its travel.

I'll be replacing the spider with a thin metal curved vane.

#11 calan

calan

    Viking 1

  • *****
  • Posts: 805
  • Joined: 16 Jun 2007

Posted 13 August 2012 - 08:23 AM

At that price, the optics are a bargain.


Agreed.

Wish I could find an 8 inch of this quality at that price. :)

#12 AutoStarNM

AutoStarNM

    Lift Off

  • -----
  • Posts: 3
  • Joined: 11 Sep 2005

Posted 17 August 2012 - 01:42 AM

Help!

My 6 inch Meade Newtonian OTA just arrived from Woodland Hills. The plug that hides the spider adjustment screws had somehow worked loose and had been rattling around inside the tube for who knows how long? There are some marks on the mirror. I have a lot of experience in cleaning optics, but cannot find a hex wrench that will fit the 3 hex head screws that hold the mirror cell on the tube. Anybody know what the heck size is needed? It seems to be neither metric or SAE. I have all the common size allen wrenches and nothing fits. I will be calling Woodland Hills tomorrow to see what they have to say. Crud! Otherwise, it looks like a very nice little scope.

Rich

#13 AutoStarNM

AutoStarNM

    Lift Off

  • -----
  • Posts: 3
  • Joined: 11 Sep 2005

Posted 23 August 2012 - 12:23 PM

Update:

I did finally manage to get the mirror cell off the OTA. The heads did turn out to be hex heads under high power hand lens inspection. They were full of goo...possibly dried black paint. So I used a dental pick to clean them out. The size for the hex was non-standard. I had to modify a 3/32 inch hex wrench with a flat jewelers file. When the flats on the hex were about .086-.088 inches to the opposite flat, the fit was good enough to remove the 3 retaining screws. This would translate to a 2.25 mm metric or 11/128 SAE.

I was surprised when I went to the local Lowes hardware store and checked the thread size and pitch. I expected a metric machine screw, but it was an 8-32x1/2 inch SAE. I now have 3 Phillips style button top cap screws holding the cell in place. Almost all the marks left by the loose spider cap came off with soapy water, distilled water rinse and air can dry off.

I had to use a hammer and wooden dowel to tap the cell off the end of the tube. It is a tight fit. It also took a rubber mallet and several tries to get the cleaned mirror back in place. The best approach was to set the tube on end resting on the tube cover and carefully tap the cell back on. Now to wait for a clear night to see how it does.

Of course, it required a new collimation.javascript:void(0)

Rich

#14 JasonKendall

JasonKendall

    Lift Off

  • *****
  • Posts: 11
  • Joined: 31 Jul 2009

Posted 02 July 2013 - 03:03 PM

I just got one of these used. Looks to be pretty good. I do observing in New York City with public outreach. I tried a test with a mEade 8mm Ultra-wide (80 deg fov), and indoors the magnification across the long hall has quite nice. It's true that the focuser is a bit yucky, but it'll serve as a grab-and-go scope for the City when I go to the High Line. I've paired it with my DM-4 and its tripod. The weight is right, and for kids and family, when I don't want to trot out my Tak or my Obsession, it's perfect. collimation is quite a chore with it. I'm trying to keep the whole rig dirt cheap so I can do subway-astronomy with it. For that purpose it works. But I do get the impression I will be futzing with collimation for a long time with it...

#15 jgraham

jgraham

    ISS

  • *****
  • Posts: 20118
  • Joined: 02 Dec 2004

Posted 02 July 2013 - 03:44 PM

Yeah, it is a nice scope. I've got one of the original N6s plus two SN6s. The focuser doesn't bother me, but I've been kicking around the idea of a modification. I am pondering installing two small Nylon screws offset from each other opposite if the rack & pinion. The idea they would serve as adjustable glides in a 'Y' pattern that would take up the slack and reduce the focus shift. Until then, I've snugged the locking screw and I always set the focus moving in one direction, inwards.

Just for yucks... my twin LXD75 SN6s...

Attached Thumbnails

  • 5951707-LXD75 SN6 Twins-1j.jpg


#16 hottr6

hottr6

    Skylab

  • *****
  • topic starter
  • Posts: 4171
  • Joined: 28 Jun 2009

Posted 03 July 2013 - 07:27 AM

I finally figured out why the N6 is so heavy; it uses exactly the same OTA components as the SN6. The SN6 does have a faster mirror, and the spider/tube ring of the N6 is replaced by the corrector/cell on the SN6. This explains the uber-heavy 0.80" steel tube that is necessary to support the corrector plate and cell on the SN6.

Over the past year I have been impressed with the night-time performance of this 'scope. The views are significantly brighter than 5"-class of Newts, but it has to lose a lot of weight to match the 5" ease-of-handling!

#17 jgraham

jgraham

    ISS

  • *****
  • Posts: 20118
  • Joined: 02 Dec 2004

Posted 03 July 2013 - 11:54 AM

Hmmm, both the N6 and SN6 are f/5's. Many years ago I had a chance to compare images taken through my N6 and first SN6. The N6 was nice, but the field through the SN6 was sooo much flatter.

Yeah, these are hefty scopes. The SN8 is a monster. I can't imagine what the SN10 must be like. The SC8 is relatively light in comparison. The SN10 and AR-5 are the only two LXD75 scopes that I don't own. You can never have too many. :)

#18 Heavensboy

Heavensboy

    Lift Off

  • *****
  • Posts: 14
  • Joined: 11 Jul 2013

Posted 29 August 2013 - 08:05 AM

Good post on this meade 6 f/5 I noticed that there was some negative feedback on the size of the secondary. The consensus was that the 1.83 secondary was too small and that a 2.14 would be best for ths scope. I have a home built 6 f/5 using a 1.83 and get great views with no issues. Just curious maybe the placment of the primary was not as it should be???

#19 jgraham

jgraham

    ISS

  • *****
  • Posts: 20118
  • Joined: 02 Dec 2004

Posted 29 August 2013 - 11:52 AM

Given the long back-focus designed into the focuser to accommodate a camera the secondary does seem to be a tad small. On my original N6 I moved the mirror back about an inch to pull the focus in a bit and give a larger fully illuminated field. For visual work I'm not sure that you'd notice the difference.

#20 BigC

BigC

    Fly Me to the Moon

  • *****
  • Posts: 5775
  • Joined: 29 Sep 2010

Posted 29 August 2013 - 01:46 PM

Hmmm, both the N6 and SN6 are f/5's. Many years ago I had a chance to compare images taken through my N6 and first SN6. The N6 was nice, but the field through the SN6 was sooo much flatter.

Yeah, these are hefty scopes. The SN8 is a monster. I can't imagine what the SN10 must be like. The SC8 is relatively light in comparison. The SN10 and AR-5 are the only two LXD75 scopes that I don't own. You can never have too many. :)

I like your philosophy!
The SN-10/LXD55 is a big setup;I found moving one as a unit not within my back's capabilities!Close to a 100 pounds :OTA,mount,and counterweights each around 30 pounbds !Mine get little use because other scopes are easier and quicker to set up even though I love the SN view.I can carry out an 8" SCT fully assembled in one trip but the SN needs three trips.

#21 jgraham

jgraham

    ISS

  • *****
  • Posts: 20118
  • Joined: 02 Dec 2004

Posted 29 August 2013 - 04:20 PM

Yeah, that's how it is with my Atlas. Even with a hand truck it's at least 3 trips. My LXD75s are lightweight in comparison. I mean really lightweight. :) Since getting my Atlas for imaging I tend to get my LXD75s out more often for visual as they are so much easier to setup.

#22 GeneT

GeneT

    Ely Kid

  • *****
  • Posts: 15474
  • Joined: 07 Nov 2008

Posted 29 August 2013 - 05:01 PM

The vanes are 0.21" thick!!


:question: :question: :question:

#23 Starman1

Starman1

    Vendor (EyepiecesEtc.com)

  • *****
  • Vendors
  • Posts: 42012
  • Joined: 23 Jun 2003

Posted 29 August 2013 - 05:23 PM

Some judicious use of a flat file can reduce the thickness of the spider vanes significantly. I see no reason, given the weight they support, why they couldn't be reduced to, say, 0.125" each.
Off-hand, it seems like a reasonable upgrade would be a standard spider and a 2.14" secondary.
A slightly more expensive upgrade would be to drop the primary mirror and change the focuser.

I owned a commercial 6" f/5 in the mid '80s and then built one from scratch in the late '80s. The commercial one had a 1-vane stalk (over 1/4" thick) to support the 2" secondary, and a fairly unique sled-style focuser (yes, it was a Celestron).
The one I built had a super low-profile 2" focuser and a 1.83" secondary
and a mirror cell with springs instead of push-pull bolts.

The size is nice. With a judicious choice of eyepieces, you can get up to a 3.2 degree field at low power. Even a 1.25" eyepiece can yield up to a 2.1 degree field. And my home-made one handled a 3.8mm eyepiece very well (197X) though didn't do all that well with that eyepiece and a barlow (expected, of course).
It's a nice size of scope and works well on the light duty mounts so common in the used market (Vixen Polaris or Super Polaris, Celestron CG5, Meade LXD 55 or 75, iOptron Mini-Towers, etc.).

#24 jgraham

jgraham

    ISS

  • *****
  • Posts: 20118
  • Joined: 02 Dec 2004

Posted 30 August 2013 - 06:34 AM

I think of them more as supports than vanes. :)

#25 donnie3

donnie3

    Mercury-Atlas

  • -----
  • Posts: 2712
  • Joined: 15 Dec 2004

Posted 30 August 2013 - 09:14 AM

this is my meade 6" f/5. I got it (I think) from meade when they were discontinuing the scope and selling them off ebay. I did some modifications in order to use it for astrophotography. cutting 1 inch off the bottom to move the mirror up, replacing the cheap focuser and making a rotating ring to move the scope to different positions. it worked out very nice.donnie

Attached Thumbnails

  • 6054105-DSCN0823.JPG



CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.


Recent Topics






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics