Weasner's LXD75-8"SC Reports

Last updated: 31 May 2006
LXD55 8sc logo

LXD75-8"SC Experiences

Jump to the start of today's update.

7 May 2006
I decided to upgrade from the LXD55 mount to the newer LXD75 mount. On Saturday, 6 May 2006, I picked one up from Oceanside Photo and Telescope. This new mount is sturdier due to the tubular legs and has a better gear mechanism. It is supposed to be better suited for astrophotography.

The next day I unpacked the LXD75-EC box and discovered to my surprise that a counterweight and rod were included. From the description I had expected to need to use the ones from my LXD55 mount. Since I got the EC model, it included the standard EC handcontroller. An "AT" model is also available that includes the Autostar, but I already had an Autostar, which I upgraded to 4.2Ed using AutostarX on my Apple PowerBook 17" with Mac OS X 10.4.5.

Setup is straight forward. There are a couple of differences from setting up the LXD55 mount. The accessory tray tripod leg spreader stays attached to the tripod with the LXD75. You just loosen it and rotate it horizontally to collapse the legs for travel. In addition, the central support rod is also used to attach the GEM head to the mount. This seems to make for a more secure mounting. Here you can see the LXD55 and LXD75 mounts side by side. Note the two leg extension tension knobs at the bottom of the tripod legs. Also you can see the larger rubber feet in the LXD75.

LXD75 mount

The LXD75 accessory tray has three 1.25" eyepiece holders (just like the LXD55 tray) but is considerably smaller, lacking in surface area on which to place other accessories. I had gotten use to the large LXD55 tray! Just like the LXD55 mount, the LXD75 mount does not include an Autostar holder. As I did with the LXD55 mount, I will be adding a strip of velcro to the top of each leg to hold the Autostar handcontroller.

Here you can see a close up of the two GEM heads. The LXD75 head has slightly larger axis lock handles than the LXD55. It has arrows machined onto the mount to indicate the HOME position whereas the LXD55 had arrows pasted on. I was surprised to see the DEC axis arrows would place the DEC motor housing on the East side of the mount. There has always been some controversy regarding whether the DEC housing should be on the West or East side. With my LXD55 I had always placed it on the West side. The LXD75 manual has photos that show it on either side. I will checkout the LXD75 with it on the East side.

LXD75 mount

Here you can see my 8" Schmidt-Cassegrain telescope attached to the LXD75 mount. The battery pack with the LXD75 is improved over the one included with the LXD55; it has a more substantial wire to the mount and a better case. The grey color of the LXD55 mount always looked a little out of place with the white tube telescopes from the LXD55 line so I'm glad the LXD75 mount is white and silver. It looks much nicer!

LXD75 mount

I document my LXD75-8"SC observations on my Oracle Observatory reports page. For most trips I used the 8"SC, although for a few I have used my ETX-90RA or ETX-105PE telescopes. I plan to try out the LXD75 mount for the first time on my next trip to Oracle Observatory, currently planned for 26-27 May. Check there for my report.

Start of today's update

31 May 2006
As planned, I took the new LXD75 mount with me to Oracle Observatory 26-27 May. The weather cooperated and even provided some strong winds as a stability test of the new mount!

Packing up the mount for the trip in my 2002 Toyota Prius Hybrid was essentially the same as for the LXD55 mount. I just rotated the DEC axis 90 degrees to line it up with the polar rotational axis (smallest "footprint" on the floor behind the front seats) and collapsed the tripod legs. With the LXD75 you don't have to remove the tripod leg spreader/accessory tray as you do with the LXD55. You unlock the locking knob and rotate the spreader bar to allow the legs to collapse. This works fine but there is a caution I need to make. As you can see in this photo,

LXD75 mount

the tips of the bars that contact each leg are pointed and somewhat sharp. One of these could easily rip a hole in a car seat or floor carpet or even your leg while moving it! I need to come up with something strong to wrap around the spreader bar when the tripod is collapsed in order to avoid damaging the upholstery or me.

Other than this concern, the LXD75 mount performed up to expectations. The wind on Friday night was very strong (reportedly 25 MPH with gusts to 40 MPH). With the 8"SC attached there was never any concern that the tripod would blow over (but I did keep the legs at their non-extended length and I did remove the telescope from the mount during the daytime just out of an abundance of caution). Whenever a gust of wind would hit the telescope the image would briefly jiggle and then dampen out within a second, even when viewing using the 6.4mm eyepiece (312X).

I spent the first night (the 26th) checking out the mount for visual use. Unlike how I set up the LXD55 mount, for the LXD75 mount I placed the DEC motor housing on the East side of the mount. Before sunset I did a CALIBRATE MOTOR and TRAIN DRIVES. First up was a manual swing of the telescope to view the planet Mercury shortly after sunset. The movement in the new mount was smooth. Mercury was a bright disk but affected by its low altitude and so presented lots of color refraction. After some stars began to appear about 2020 I decided to do my first alignment with the LXD75. I did a One Star alignment to align the polar axis on True North. Then I did an Easy Two Star alignment to refine the pointing accuracy of the Autostar (version 4.2Ed). First GOTO was to Jupiter and the LXD75 placed it directly in the center of the 26mm (77X) eyepiece. I spent some time just looking at Jupiter in 26mm (77X), 12.4mm (161X), and 6.4mm (312X) eyepieces. I used a Meade #905 Variable Polarizer Filter to reduce the glare from the planet, which helped a lot in seeing details in the cloud bands. Easily seen were multiple cloud bands, some dark spots, and of course, the four Jovian moons. I then did a GOTO Saturn, which was west of the Meridian (Jupiter was east at this time); it was placed just offcenter in the finderscope field of view (FOV). Saturn was too low in the sky to observe using the 6.4mm eyepiece but it was nice in the 12.4mm eyepiece. One cloud band and the planet's shadow on the Ring system were visible.

Next up was Mars; small red disk with no features visible. I then did a GOTO to M13, the Great Globular Cluster in Hercules. It was centered in the 26mm eyepiece (it was east of the Meridian at this time). Very pretty with lots of stars visible in the 26mm eyepiece. I then switched to a Tele Vue 35mm Panoptic (57X) 2" eyepiece. It was a beautiful sight! I then did several other GOTOs to the galaxies M101, M81, M82, and M51. All were centered in the 35mm FOV and were really nice objects. Now that twilight had finally ended I did a "Tonight's Best" guided tour. I looked at many galaxies and star clusters. All were basically centered in the 35mm FOV. I was able to observe the Omega Centauri globular cluster, which was very low in the southern sky and just visible through some tree branches. It was still an exciting object to see since I rarely get to view it. I then took a look at M57, the Ring Nebula. Just lovely. Last for the night was Jupiter, which was centered again after the GOTO. By this time the Great Red Spot had rotated into view and was easily seen. But I didn't see its new "baby brother".

The second night was mostly devoted to some 8"SC Prime Focus astrophotography with my Nikon D70 DSLR using RAW imaging. Guiding was smooth when I did it. With the LXD75 mount there was no backlash (unlike what I experienced with the LXD55 mount). Tracking was so accurate most times that for exposures of 1 minute no manual corrections were needed. You can see the best of the astrophotography from this night on my Oracle Observatory report.

Based on this initial experience with the DEC motor on the East side and my experiences with it on the West side on my LXD55 mount, I believe that the side is inmaterial to the Autostar. Only the alignment arrows matter if you want to use them. The Autostar just counts pulses from the encoders so the side of the motor doesn't matter (in my opinion).

Overall I am impressed with the LXD75 improvements. I don't like those sharp points on the spreader bar but that is the only negative I could find in an otherwise outstanding upgrade from the LXD55 mount. For my next trip I plan to take an extra counterweight to proper balance the system when attaching the ETX-90 OTA piggyback as a guidescope. Without this extra weight the system was just slightly out of balance due to the extra weight.

Stay tuned for more updates...

Return to the top of this page.

Go to back to my LXD55/75 Home Page.

Go to Weasner's Mighty ETX Site.

Copyright ©2006 Michael L. Weasner / mweasner@optcorp.com
URL = http://www.weasner.com/lxd/8sc/lxd75.html