Category Archives: Uncategorized

Confirmed, the new RA worm is working well

Finally another clear night presented itself last night, and I replicated my testing of PE with the new RA worm block in place.

I tried data gathering with longer exposures, but didn’t like what it was telling me, then realized I was on the wrong track anyway;  I should keep my data gathering to short exposures and let the fact that I am averaging the PE over multiple worm cycles handle smoothing out the seeing.  This is consistent with all the advice in the Bisque support forum too.  So I increased to gathering more worm cycles – 7 cycles.

Uncorrected, the worm is averaging out at 1.2 arcseconds peak-to-peak, and even looking at the raw data, the worst case swing is 2.9 arcseconds. That difference shows the seeing jitter.  This is really good performance – the guaranteed spec from Bisque is 7 arcseconds, so the worm is ‘way outperforming that, and is below seeing.

Then another 7 cycles with PEC turned on:0.4 arcseconds peak-to-peak residual error with correction running (averaged out over the 7 worm cycles), with max including big seeing spikes of 2 arcseconds.


I tried a quick image with guiding turned on.  I’ve lost the guider log, but with 3-second guide exposures and light aggressiveness (40%) it was holding the image to under 1/2 pixel.  The resulting image in this 5-minute exposure has nice round stars:

This seems to be avoiding an obvious question: what does an unguided image of some substantial length look like? I didn’t see the point of doing that test yet, since unguided imaging is substantially enhanced by ProTack, which I haven’t configured yet.

Next clear night (several days away) i’ll do a small TPoint run to re-check polar alignment, then a large TPoint run to build a good model, then do some experiments with PEC, TPoint, and ProTrack all turned on, to see how long unguided exposures can be.

These TPoint runs will be much easier, and more accurate, now that I have installed the SkyShed’s PZT so I can roll the roof right out of the way.  Previous TPoint runs involved having to chase the scope around the sky with roof rotation – both inconvenient, and also likely introducing vibration.

Started Mount Refurb

Yesterday I removed all the gear from the mount, and removed the mount and adjustable mounting plate from the pier – per the previous post, to lower the mount to sit directly on the pier-top adaptor and not on those 3 threaded shafts.

This meant drilling new holes in the pier-top adaptor, as the mount’s mounting plate attaches to the pier-top adaptor with 4 1/2″ bolts.  I used stainless hex bolts with lock-nuts.  This procedure was delayed by one day because one of the lock nuts jammed during a test install, and it took a long time to get it off – I eventually had to break it off by putting a 1-metre extension on a ratchet handle and turning until the bolt broke.  The replacement, and all the other bolts, went on with no problems.

The plate and mount are now back on the pier, without the flex-inducing leveler bolts.


I remounted OTA, camera, etc., and re-balanced the mount on both axes. Tomorrow, I’ll go through a complete maintenance regime, cleaning and regreasing both gears then adjusting plunger springs, cam stops, mounting screws, etc.  Recabling everything will require some thought, as I was using the space under the mount as an equipment shelf for certain power supplies.  Instead, I’ll mount those to the pier with Velcro or find other places for them.

Then I’ll need a new polar alignment, having taken the mount off.  I’m looking forward to the first PE check after this is all done.

Mount adjustment: change mount-to-pier connection

Restarting after a year+ absence (various reasons, not for publication here).

In reviewing online support forums, I see another recommendation.  I’m using the SkyShed pier, and the supplied pier-to-adapter plate connectors, which is 4 long bolts the mount sits on, that enable leveling.

It’s pointed out that those are a (rather obvious) possible source of flexure. And they’re not really necessary – assuming the pier is reasonably level, proper polar alignment in the mount will overcome any fine-tuning of leveling.

So, new first step, that I’ll do on the first opportunity:  Remove those leveling bolts and mount the pier plate directly on the pier.  The only issue will be that the space between the pier and the plate has been a useful “cubby hole” for various cables, and those will have to be relocated.

Tune-up journal 3: more worm adjustments

Last night it was clearing up nicely, after a very hot humid day.  I opened up the dome about 1 hour before dark to let things start to cool, then used that time to continue tuning the mount gears.  I took the cover off both worm blocks, inspected belt tightness and pivot screw tightness.

The Declination pivot screw seemed a bit loose, so I tightened it slightly. (This is another screw that has a “right amount” of tightness and I can’t find any documentation that gives the appropriate amount for the MX+, so I just snugged it up a bit by feel.)   I also loosened the RA spring tension plungers another 1/2 turn, so they are now at 3.5 turns out-from-bottom, which is the loose end of the specified range.

To see what effect these changes made, I started to set up for another Periodic Error data gathering run.  I was having trouble finding the guide star, and was wondering why until it occurred to me to look up.  Sigh. The sky had completely clouded over.  In fact, shortly after I closed up the dome, it started to rain.  So no new sky data to test the results of these latest adjustments.


A test sketch of M81

Friday night was clear with very good transparency.  I finished re-doing my TPoint calibration and, as part of that, confirmed that polar alignment is still good.  Then did a new, larger, data collection run for periodic error correction.  Something still not right there – the uncorrected error was higher than it should be (although not high).  Corrected it’s fine, but I still hope to get to the bottom of what’s going on there.

Autoguiding is also working fine now – not incorrectly calibrating on hot pixels – since I set up dark-frames and hot pixel elimination for the guide camera.

Messier 81

Messier 81

So, last thing before the sky went hazy, I did a test run of M81, just for fun.  This was 6 5-minute luminance frames.  Interesting: the mount is so stable with PEC and guiding running that I have a problem with dust spots that I’ve never had before.  In my former setup, the error and wobbling in the mount provided a sort of “auto-dither” that smeared out the noise (and the non-noise). Now it’s so stable that the pixel errors are always in exactly the same spot, and so are visible.  So, next time, I’ll start adding a several-pixel dither to the autoguiding.

Anyway, it’s a pretty image.  I think I’ll keep it, add data and colour, and work it into a finished product.  Not right away though: this object has almost rotated behind my tree, and I’ll soon lose it until autumn.

Restarting for a new Winter season

It’s been about 10 months since the observatory has been running, a lapse caused by some other priorities followed by a long spell of poor weather. Now I’m working through a checklist of things to get it back on the air.

  • Planning to do some wide-field imaging this winter, I dismounted the AT8RC and mounted the SV80S refractor, moved the focuser, and redid the counterweight and balancing for this lighter scope.
  • Replaced the observatory canvas cover, which had become tattered last year.
  • I repaired the mount for the flat-field light panel, which had become unglued during the heat of summer.
  • Numerous computer upgrades, bringing software, patches, licenses, etc., back up to date.
  • Just outside in the cold, I turned the PC internal heater on for the season.If the sky remains clear, I hope to calibrate the focuser tonight and maybe tune up the polar alignment.

Designing a PC for Outdoor Storage

I hope to keep a PC permanently installed in the observatory to speed setup, and avoid any more incidents where I drop and break my laptop when cold and stupid.

A PC stored in the observatory would be sheltered from rain, but would go through temperature and humidity extremes. I would think there could be trouble from

  • Starting it up when it has been sitting cold in the winter – possibly at temperatures as low as -15 to -20°C.  Moving parts will be tight, lubricants will be viscous, etc.
  • Shutting it down in the cold after it has warmed up. Will the cooling parts become damp with condensation, and what will such moisture do?
  • Performance of LCD monitor in the cold (I know from other appliances that LCD displayes fade in the cold).
  • Infiltration of insects into parts.

I’m going to try to design a PC that can work in these conditions, and will keep a diary of the attempt here.

Saturday, January 23, 2010

Removed the CCD camera and filter wheel from the imaging scope, brought it indoors, and let it warm up. Then I checked the filters for cleanliness – they seem OK and I decided not to muck with them other than blowing dust off. Disassembled the CCD camera and found the protective window to be quite dirty with microscopic dust spots, so I cleaned this with 99% isoprop alcohol, both sides. The CCD itself seems ok, and I didn’t clean it except for gently blowing off dust.

Saturday, January 9, 2010

Notes from Journal Page: January 9, 2010

It’s finally clear, but very cold.  Right now the outside temperature is showing (only) -12 but the forecast says it will drop to -21 tonight, hitting the low about 10:00 PM and staying there.

I went outside this afternoon to clear the snow and ice from the dome cover and shovel the deck clear around the dome door, and went into the dome and turned on the heater at the “keep from freezing” setting, which will very gently warm the interior of the dome just slightly, holding it a few degrees above freezing, which should make the startup of the mount, gears, motors, etc., a little easier.

Tonight’s plan is to gather more data for the B33 region that I started a couple of weeks ago.  I still need all three RGB colours, and would also like some straight luminance to serve as a base for the Ha capture I already have.  I will also do a quick RGB image of a G2V star, if I can find a convenient one quickly, to calibrate the colour mix. Continue reading

Thursday, January 21, 2010

Journal Page: January 21

It’s finally clear, and not very cold – about -3C. Been cloudy for weeks, and suddenly a good clear stretch. Quite warm – around freezing – the last few days so humidity will be high and probably poor transparency.

Tonight’s plan is to gather more data for the B33 region that I started a couple of weeks ago. I still need all three RGB colours, and would also like some straight luminance to serve as a base for the Ha capture I already have. I will also do a quick RGB image of a G2V star, if I can find a convenient one quickly, to calibrate the colour mix. Continue reading