Zeroing In

Last night was a nice transparent night, the moon about a day from full.  Jupiter hovered an inch from the Moon’s head.  A good night for fooling with the system.

My polar alignment should be pretty good, but the scope still doesn’t know where it’s pointing.  My Meade finder scope often has a mind of its own and can be off enough that the target is not even close to being on the camera’s chip.  The coverage of the chip is only 17 x 11.5 arc minutes so it can be painful to locate an object with the camera. Once you find it, and sync the mount, you’re good until you crash into the counterweights with your head and knock everything out of alignment, or make changes to polar alignment, or rebalance equipment, etc. Usually I take off the camera, put in an eyepiece, find the thing I’m looking for, put the camera back on, center the image, and re-sync.  PEMPro has a “Find Star” feature that takes images in a spiral around the current position, and when it hits the target, you can right-click the frame and it will center it so you can sync properly.  I’d thought I’d give that a try.  I will say that it worked like a charm, except I was so far from the target that I grew weary of waiting.  Also, as PEMPro accumulated images — its default limit is 100 — my fairly ancient PC began to act like it was choking with low memory.  I also had trouble connecting remotely, and eventually had to kill PEMPro with the task manager.  So I disconnected the camera, installed an eyepiece, centered Vega, reconnected and centered Vega on the chip, re-synced the mount, recentered the finder, and was back to normal.

I used the TheSky to go to the double-double, centered on one of the pair on the chip, then a look at M57, which centered up perfectly.  Probably won’t stay perfect since the 12″ mirror has a bit of play that will show up as we slew around the sky.  I made a 300 second uncalibrated luminance image just to get an idea where we stand.


M57, uncalibrated, unguided, Meade 12″ at f/10, 300 seconds luminance; ST-10.  Fair transparency, bright moon light.

The oval stars  show there’s a bit of tracking error in RA, which could be periodic error, and I’ll get into PEMPro to see if I can improve that, next full moon.  I would like to, and believe I can, do 5 minutes unguided.  But anyway, that error will certainly guide out. Getting the guiding cleaned up is next, along with auto-focus.  I have been using the guide chip on the ST10, but want to set up the new Orion SSAG autoguider, which I think will work better for narrow band imaging.  The focus is also off, and I will get the auto-focus routine down.  I get fairly good focus manually using a mask, but auto-focus will probably do better than I can, and for remoting, auto-focus absolutely has to work.  Also, there’s vignetting and dust donuts which will disappear with a flat field.  I need a good, repeatable flat-fielding method.  I have a white target set up in the hut I have used successfully and wonder if it would work if placed in the Park 1 target zone.

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