New FSQ106, maintenance


Have obtained a new-to-me FSQ106EDIII. After some false starts I have the adapters from OPT and Texas Nautical. Built another bracket to attach the EZFocus motor.

While testing the focuser for slippage the wall wart died. Very hot, no voltage. Replaced it with a cable to the old 12V power supply, seems to be working now.

Odd issue – while running the VCurves and ACP Focus Offset script, I notice that the focus position seems to be consistently changing. If I run multiple focus runs in a row, as quickly as possible, the resulting position seems to shift by about 35-40 focuser tics. This shift is probably roughly the size of the crtical focus zone.

So, when Focus Offsets runs, it seems like the focus position of each filter is off by n*35 tics. When HAlpha comes up with an offset of 189 tics, it may actually be off by 140 tics!

I don’t know what is causing this shift. The scope certainly doesn’t shift temperature that fast. I thought maybe the focuser was slipping, but measuring the position of the camera with a dial caliper shows to slippage. I ran the focuser back and forth 5 times (1000 pulses each way) and it ended up back at the correct position each time.

I did find that the backlash was off; I changed from 200 to 500 pulses. I will re-run the Focus Offset script again.


Updated ACP to 8.1, including updating the web system.Cleaned up the web menu system a bit, added a couple of items (AstroCalc).

Updated FM to


Drizzle Kernel Function Note

Playing with Drizzle again.

Saw a mention on the PixInsight forums about Drizzling with factor 1. Apparently this can help reduce the noise in your stacked image? Odd idea, I will have to try that sometime.

Tried varying the drizzle Kernel function. There are several possibilities, primarily Square (default), circular, and Gaussian. Potentially Gaussian can provide better results, but needs a larger number of subs to work well.

So, I tried doing 16 subs (Blue filter of M100, binned x2, 15 minutes each), using each of the 3 functions. I used a 0.9 drop size for each, drizzling by a factor of 2. The hardware was the STF8300M / Edge 11 combination. Measured the noise of the integrated image using the Noise script.

Kernel Noise (e-4)
No Drizzling 2.590
Square 1.511
Circle 2.015
Gaussian 2.580

Clearly in this case the default Square function performed the best. The Gaussian took significantly longer to calculate and was no better than not drizzling at all..