Flat frame, PEC issues

Last night was a beautiful night, so I tried some more testing.

First, I reran the flats for the Canon using a target of 5000 ADU instead of the original 20000. Ran a number of M82 shots. The bin1 shots seem to be doing the flat correctly, but the bin2 images are still dark in the center.

Then, I saved the Narrow system setup and started getting the Wide system working. A lot of things have changed, since the cameras are switched from the original setup. The VCurves are still valid.

Basic problem: the filters aren’t working on the SBig. I will need to get that fixed. It also seems like the internal guiding function isn’t right somehow. I will need to look at that.

Tried doing some 5 minutes exposures to check guiding using the external guider. Guiding is working well, stars look good.

Tried doing the 5 minutes without guiding (ProTrack and PEC should work, right?). The stars are elongated in RA. Looking at the guiding graph, there is significant fluctuation in the RA, perhaps +/-3-4 pixels. If the image scale is 3.7 arcsec/px, then this is a fluctuation of 12 arcseconds – not good.

Tried again with PEC turned off. This is better! although still +/- maybe 2.5 pixels. Remembering that I had randomly flipped the PEC because I thought it made it better, I re-flipped the PEC curve and tried the flipped version. I think it looks better. Portions are very nice and flat, but there is a section where the graph wanders up and then back down again.


– Need to fix the filter wheel. I assume this is the UHC filter falling out again.

– it looks like I need to re-run the PEC curve, see if it looks any different.

– Need to check the flat process with the Canon. Something is still wrong there.

– The system still does not point accurately. It looks like it needs to be sync’d on some star to be correctly centered. Slewing to targets puts them off to the left of center. On the Canon, the target can be off the chip, off by 10-15 arcminutes. Certainly not the 6 arcseconds being reported by SkyX.


Dome checkout

Last Wednesday, Steve came over to the dome/clamshell and verified the operation as I opened and closed the dome. Everything seemed to be working fine. OK, maybe now I can get going.

So, Last night (Sat) I wanted to get going, weather looks good in NM. But, the computers are turned off! Both NM-Dome1 and RC16-Server are off. Don’t know why – perhaps they are doing some sort of maintenance or something. Called Steve, he didn’t know anything about it. Called Ron, no answer, left a message.

Well. maybe tomorrow I can do something.

Running Big Model

Got a couple of relatively clear hours last night, so I ran a Big Model (308 points).

Raw results indicates that both Alt and Az polar alignment are fine. Results were something like 130 arcminutes for the inner ring, 200 for the outer.

Supermodel results (after removing the one outlier):

308 point supermodel

Wow – 6.8 arcseconds.

Interesting, the polar alignment now wants a change:

************* Azimuth ************
Recommendation: Azimuth alignment is excellent. No additional adjustments are necessary.
Supporting information
MA = 30.7 arcseconds (0.5 minutes) Sigma = 1.22483 – Adjust Confidence-High.
For latitude +42° 55′ 47″, rotate the azimuth axis West 41.9 arcseconds (0.7 arcminutes).
Paramount ME: Loosen the West knob and tighten the East knob 0.3 knob tics.
Paramount MX: Loosen the East knob and tighten the West knob 0.7 knob tics.

************* Altitude ************
Recommendation: Make the following altitude adjustment…
Supporting information
ME = 65.7 arcseconds (1.1 arcminutes) Sigma = 5.35898 – Adjust Confidence-High
‘Ideal ME’ = -64 arcseconds (the refracted pole).
ME adjustment to get to above ‘Ideal ME’: 130 arcseconds (2.2 arcminutes).
The polar axis should be raised 130 arcseconds (2.2 arcminutes).
Paramount ME: Raise the polar axis 1.1 knob tics.
Paramount MX: Raise the polar axis 2.0 altitude tics.


Graphs for the 308 point Supermodel