JanH

I don't know. But I'm definitely not touching this sensor any soon. There are two working chips around with same issue (but worse, one or two pages back) and on one I tried more polishing without making it better. I felt as I'm digging through layers, some are brighter, some dimmer, stains were moving but not disappearing. I can try more, no problem, it's gonna be cloudy for rest of the season anyway (dark sky departs within a month). Strange that newer sensor (16mpix in Nex 5N) doesn't do it, CFA is tougher but once it's gone there is decently flat surface (I can see some brighter areas but it's comparable to normal falloff). And since there is little hope for clear sky any soon I processed Heart nebula also (the last image I have...). Unfortunately just 5hours Ha, 45min OIII and that's it. Ha=red, Oiii=blue, Ha 25%+Oiii75%=green.

and matching flat.

Here is 2hour exposure of horsehead taken with mirrorless Sony Nex5, 14mpix sensor, Baader 7nm Ha filter, smc A* 645 300/4 10min frames, 2hour total, flats, darks, bias, Processed in DSS as superpixel (thus 3.5Mpix = full resolution). Notice vertical lines along the left edge and slightly also on the right and there is massive inconsistency in bottom 20% of the frame. There is more detail in the files (I hope) just to get it. I overstretched the file to make it obvious. It's pitty as right now I have just 2 cameras, much better Nex5N (very flat flats and overall better sensor) is on 8" newton and on 300mm lens is older nex5 but I'm constantly messing up with that newton so this telelens was piggybacked to tube ring and guiding with OAG on newton (shooting M42) but as I discovered after 2 hours of clear sky Newton was out of focus!? Shooting at 300mm FL and guiding at 800mm FL. Hmmm.

I recently noticed that glass removal (soldering iron method) works much better when the sensor is frozen. At least on sony Nex5 14mpix cmos sensor it worked perfectly (it was struggle every time before on that type of sensor and glass from this last one came of in one piece and undamaged). This sensor is not suitable for polishing method though (leaving stains, waves... not sharp but disrupting structures visible in narrow band). Now I'm having some trouble processing files. This time I managed to use DCraw -> DSS method (still don't know why it rotates some frames = I have to rotate them back manually before feeding DSS). Stacking went well (decently) but there are some FLAT issues. I have some lighter strokes visible on the sensor (and "waves" along longer sides) and flatening doesn't touch it. I must say that I don't dither as I didn't work this out yet (in Lin_Guider). And another issue - I can't open files generated by DSS (never had this problem before with colour images or super pixel grayscale or Bayer Drizzle). I tried to save it in different formats (tiff 32, 16, rational, integer) and some works at least in image viewer but none of them is recognized by RawTherapee or GIMP.

So far no success in processing the data. First I tried to create linear tiff files with DCraw (same flags as Gina published some time ago) but DeepSkyStacker failed to find any stars. Strange as I can mark stars manually... And when I fed it with raw files the final image is rubbish. I'll try later after some sleep and work. and thinking about changing settings and such.

Mono astro camera with sensor this big costs far more than most of us can afford to spend. Cheapest Mono astrocamera I know SBIG STF-8300M with large sensor costs 2500eur and yet the sensor is only 18x14mm in size having 8Mpix resolution. No doubt it has better parameters for astroimaging (it's cooled CCD after all). When considering this mod keep in mind that resolution will be reduced by about 0.5mm on each site (I don't dare to go closer and risk destroyed sensor for gaining 5 more pixels). This loss is bearable with aps-c sensor - it can be as little as 50px per site. Do this with VGA camera or even with HD the loss would be too great not talking about practical issues like how to get there (on the other hand for planets you don't need the corners, just center...). On aps-c I can do long strokes, circles. Here goes dark, Nex 5N, ISO 1600, 520s, room temp, color image from raw, just cropped (for some reason camera generates JPGs in reduced panoramic resolution, old firmware??). with some luck I give it a try tonight (after midnight might be 2hour window).

It's nothing else but success! Despite one broken foot of sensor housing (camera had impact damage), in one corner I scraped too far over the edge when polishing and plastX paste flooded some golden wires in quite many places. But sensor still works, area loss is about 150x100px leaving about 15Mpix and no stains visible!!! This is "flat" taken with coma corrector and Ha 7nm Baader filter (I didn't bother to point the camera against evenly illuminated area thus there are some inconsistencies but nothing to worry about). Non-debayered in Rawtherapee choosing "mono". Once I close the camera dark frame will follow.

I tried to re-polish the sensor but with little success. It might be better in some places but I added some scratches too so it's time to leave it. Next time I'll try polishing&rubbing method alone without scraping. Sensor from Sony Nex 5N is ready. 16.1Mpix CMOS sensor, ISO up to 25600, it's a good sensor, better than old 14mpix in original Nex 5. Nex 5N seems to have much weaker epoxy - first time I got the cover glass off in one piece, it's chipped in several places though but only at the very edges so I believe it's reusable. I didn't have to force it and heating with soldering iron went fast and smooth. Strange as others report that newer sensor = stronger bound.

It is in red only. I just made a test showing that with no filter, CLS filter and OIII the pattern is unnoticeable or extremely weak. in Ha and SII - bad. That very first composition frame yesterday was made with CLS.

I see trouble. Composition frame at ISO 6400, 10s. Processed from raw to mono in rawtherapee, some curves applied. Even background illumination. Flat I took after some time this evening. Compare with scraping pattern from 28th of January (red, second sensor of that day). Second sensor (first on 28th January, those blue-brown images): ISO 1600, 520s, filter Sii, some clouds obscured the view for most of the time - there is not much to see (but it's easy to find M42 on the right, 300mm FL, first is 800mm). Scaled JPG, no post process. Flat, same data (iso 1600, t=520s), it's not flat-flat but light frame with clouds (only brightest stars are visible). And when I combined these two frames in rawtherapee I got this: I had to set "blur" to 0 for flat filed. As default is set 32px - just moving the pattern and not eliminating it. Looks brighter but that's because rawtherapee applied some exposure correction I didn't notice. I don't understand why this pattern didn't show up on short exposure at high ISO (both cameras, marked S-silver, B-black in image names). Does DSS or other stacking software blur flat fields? Scraping wasn't probably the best option after all...

It showed up that there was similar issue with my other cameras too thus I was so amazed with results from Nex 5N - LED is there too but it's not glowing during exposure, just when writing to memory card (or during start up...). This internal light pollution is not a problem when camera isn't moded - AA/IR cut filters and piezo element protect the sensor from this light. All these things are gone leaving empty space. Apply to both Sony nex 5 and Nex C3. With this diode blackened out the dark frames are really dark (and it gets better outside or with cooling). Nex 5 mono, 520s, ISO 1600, room temperature, colour image, WB "daylight".

it is stray light. I sealed the sensor with electricians tape (black), it's not totally light tight but in total darkness the result is cleaner without any patterns. There is a red LED on card reader glowing constantly during exposure. I suspected that before (together with AF light and IR remote control), now confirmed. Gotta work now.

dark didn't look good at all so I turned to next sensor. This one will be for normal shooting in daylight. Same approach as earlier. Looks usable. 9min dark frame at room temperature doesn't show any major inconsistencies but it's a pity I didn't take a dark frame before I started. after scraping: flat (not exactly, fridge door and opened camera body = light leaking all over) and dark, 520s, ISO 1600, (bed)room temperature, no heatsink, no cooling.

taking dark frame now but sensor no.6 is working. As i mentioned yesterday first I scraped some layers away but it was a mistake to start from the edges. I just didn't find the right angle and pressure to remove microlenses and to disturb CFA. I got it right just when I moved to the center. brown layer around are smashed microlenses (or some hard layer beneath), dark brown in the middle is CFA alone and blue is clean sensor (sorry for colours, there was some custom white balance...). Removing CFA with plastX went well in the center but brownish areas were tough and there are some stains left exactly in the same places. And I can see a small scratch at the center-bottom. Loss in resolution is decent 100px in both directions (50px average per edge). Dark doesn't look so good, making some more samples (could have been light leakage). Eyes are fine btw.

I wanted to bring a good news tonight but business as usual. Still I made great progress. Sensor no. 4: scraped with wooden stick - a lot of CFA left all over, but still working. I taped "no go zones" with office tape (transparent adhesive tape) and flooded active area with that plastX. CFA went of immediately (or within a minute) but only where I scraped away microlenses. There were some spots of sensor surface untouched and polish didn't manage to penetrate this top layer. I made a test with no. 5 with same result - Plast X doesn't get through microlenses and I have a feeling that I started removing CFA only after scraping off microlenses with polishing tool having trouble reaching the corners. No. 4 was still working after polishing, resolution dropped from 14 to about 12.5Mpix. In the center of the sensor were some "shadows" of CFA (I didn't polish the center as much as the edges) and the very edges deserved some final touch so I repeated taping and flooding procedure while delicately scraping some more durable spots along the edge. Polishing went well, no stains left but sensor passed away. I probably scratched too close to the edge or something. doesn't give error, just white screen. Good news before bedtime is that I succeeded with no. 6, at least sensor is glass-less and still working (cover glass shattered and I might have some bits in my eye but we are alive). Tomorrow I'll try and scrape it gently from edge to edge leaving CFA more or less intact and then making swimming pool with plastX disolving CFA. Plan sounds good, reality might be different.