A little LXD-75 maintainance

After the last imaging session I had I noticed a little bounce in my mount on the RA axis.  I decided I could live with that for the night and then resolve it at a later date.  The following weekend I spent with my parents and my kiddos at a local kids resort with an indoor water park.  The weekend after that we were all sick with one strain or another of common cold.  Most of us had different symptoms and a different duration but we’re all still recovering two weeks later.

Today I decided I was well enough to tear into the mount and deduce what was going on with the RA axis.  A quick disassembly also uncovered a problem with the Dec housing.   It cracked at the screw holes when it whacked into the mount after being left unattended during my M42 imaging run.  The WarpsDrive mod certainly didn’t fail and everything is as tight as it was when I finished the mod.  I have uncovered the source of the mount’s RA challeneges though.  The preload bearing for the worm gear needed to be tightened just a smudge.  I’d say less than 1/16th of a rotation to take all the lag out of the RA axis.  The mount seems to respond without any noticeable drag on either axis so I’d say I have it licked.  I need to get it outside and recalibrate the drive motors but that can wait for another day.

Back in the saddle

It’s been fairly eventful the last couple of weeks.  With the Christmas holidays there was of course little time for observing with anything more sophisticated than Ye Olde Mk. 1 Eyeballs.  After Christmas I took advantage of a warm night and set my mount up for a little testing after installing my Warps Drive upgrade to replace the factory gears with a toothed belt system.  Many people have used them with a great deal of improvement over the factory Meade gears but I’m not entirely convinced yet.  So far they’re a bit springy at tensions that actually permit the mount to move easily but I digress.

I’ve had some recent electrical issues to compound the mechanical ones which did nothing to help my esteem.  With the obvious mechanical issues resolved I managed to blow the Declination axis circuit board.  I didn’t particularly care to send Meade a reported $130 to $150 for a new drive assembly but I didn’t see much choice.  A quick look at AstroMart.com showed that there was traffic in the Meade LXD drive motor assemblies but nothing had been posted in over a month and they all seemed to go pretty quickly.  It seems the Dec axis fails more frequently that the RA axis.  I’ll have to ponder that one later.

Right now I’ve got the mount set up and snapping pictures of M42, the Great Orion Nebula.  I know this target is challenging to process.  There is a wide range of intensity across the expanse of the nebula which makes it difficult to visualize the scope of the actual object.  A common process is to take several sets of exposures at different lengths and lay one on top of the other in a technique called High Dynamic Range.  In previous attempts at M42 I used a specialized astronomical camera.  This time I’m using my DSLR.  I’ve taken the short exposures necessary to highlight the Trapezium at the center of the nebula and the dark frames needed for that set.  I took a longer set to highlight the middle of the nebula.  The center of this frame will be covered and blended with the short exposure of the Trapezium.  I’m now taking the longer exposures to (*hopefully*) show more of the extended nebula.  Unfortunately my home made shutter control cable seems to have picked now as it’s time to fail.  I really should have taken it off the prototyping board but it was working well and I didn’t want to jinx it.  I’ve got the manual bulb shutter cable plugged into it and the camera set to its maximum 30 second exposure.  It should happily click away until I unlock the button to release the shutter.  I figure I’ll let it run for 40 minutes or so and get about 70 exposures total of which I expect I’ll be able to use about 60.  That should give me good detail for what I can get with only a 30 second exposure.  I was planning on running 60 seconds to get a more full view of the nebula but it doesn’t look like that will pan out this time.  Oh well, maybe I should just opt for a commercial cable or put it in a proper case.  At least I’m not at a dark site where I could be getting 120 or 400 or 800 second exposures.

And to boot, my alignment is absolutely perfect.  Naturally it’s going to rain tomorrow so the mount must come back inside.

M42 from last year

M42 taken December 2008 from Dallas, TX.  While the local skies aren’t the worst I’ve seen in a city they’re still far from perfect.  The large population of high pressure sodium and mercury lamps from city streets and local shops floods out most of the stars.  M42 is only visible with the naked eye on the best of nights, about twice a year.

M13 – Globular Cluster in Hercules


M13 is a favorite subject for many observers, myself included.  I’ve looked at it from the backyard with my own eyeball.  I’ve seen it through my 8×50 binoculars.  I’ve looked at it in a Dobsonian with a photomultiplier.   This globular cluster contains over 100,000 stars that are all held in this fuzzy ball by the weak force that sucks.  Gravity.  From studying the spectral lines of various stars and the red shift of those stars scientists have derived an approximate distance of 25,100 light years from Earth.  It has an angular size of 20 arc minutes or 1/3rd of a degree.  One degree is 60 arc minutes, 1 arc minute is 60 arc seconds.  At a distance of 25,100 light years that means the globular cluster itself is 145 light years wide.  Keep in mind that light travels the same distance as seven and a half times the circumference of the Earth every second.  It takes about 8 minutes for light from the Sun to get to earth.  Light leaving one side of the Hercules Cluster will take 145 years just to get to the other side of it.  It will take another 25,000 years to reach your eyeball.  Huge, HUGE distances and this is a relatively close object.  In looking at M13 over the years I never seem to stop enjoying this object.

I took this image with my 6″ Meade Schmidt-Newtonian reflector on a LXD-75 mount.  It was autoguided with a Meade DSI Pro and imaged with an unmodified Canon Digital Rebel.  I used some really clever free software to stack 71 subexposures of 30 seconds and after some processing got this image.  The process of stacking adds data together in a magical way to increase the signal without radically increasing the background noise level.  If I were a mathematician I could explain it to you but I’m sure you’d fall asleep.  I sure would.  After stacking I typically run the resulting image through yet more software to increase the contrast, brighten things up and enhance the color.  It seems I always spend more time processing the image than taking it but that’s honestly half of the fun.  In the end, what you see is what you get.  I sure had fun taking it.  I hope you have fun enjoying it.

UrbanAstronomy.com v1.1

My mission is to get people in urban areas to think about what’s in the sky above them. Just because you’re in the city doesn’t mean the stars don’t exist or that you can’t see or understand really cool celestial events.