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This is the first lights of my ASA 12"N f/3.62 (purchased in 2007) with my Moravian G4-16000 CCD camera using one KAF-16803 chip of 36mm x 36mm (4K x 4K).
The adjustments, collimation, ASA OK3-Z pression screws, asked a lot of attention.
For a precise collimation, i use the CATSEYE XL & XLKP kit.
This is the first 3hrs of exposures taken the last weekend in one night. The second night was too windy unfortunately.
Full Resolution image in 4K x 4K here :
Full Resolution Annotated image here :
All the information below :
Hope someone with more experience than I, which basically means anyone that has successfully collimated a Newtonian, can answer a couple of compound questions I have based on my first and only attempt at secondary collimation of my SkyWatcher Flextube 250.
1) All three of my secondary collimation screws were extremely snug before I did anything and I was only able to comfortably turn them counter-clockwise. Is this normal? Do I need to loosen all three screws first before I can properly start collimation? Should I be turning any screw beyond "snug"?
2) Before collimating, I placed a yellow sheet inside my OTA opposite my focuser tube and I placed a red sheet between my secondary and primary. The view this gave through my focuser tube was of a red circle surrounded by a partial yellow ring (the secondary mirror stalk blocking a portion of this yellow annulus). While independently turning each of the secondary collimation screws counter-clockwise I looked down the focuser tube (both with and without a sight tube installed) expecting to see some change in the shape of the red area (more or less circular) and/or the yellow area (less or more even thickness). I turned the screws no more that 2 complete revolutions. I did not perceive any appreciable difference in what I saw and I turned each screw back (clockwise) to their original tightness before working with another of the screws. Does it make sense that I didn't perceive any change? Should I have turned the screws more revolutions? Should I have loosened more than one at a time?
Very confused and looking for your help. Thanks
As some of you know, I postponed the purchase of a Dobson for a few good years. Now that things in life are a bit more stable, I am in the market for this Dobson.
It will take a bit before I press the button, as I still need to understand a few things about dobsonians.
I've been contemplating a classic truss 12"-12.5" f5.5-6 for a while, as this would offer me a trade-off among portability, focal length, power, DSO, planetary, no coma corrector, and standup observing.
Mirror and mount are equally important to me. I haven't yet decided, but I'm leaning towards an Astrosystems or Teeter 12.5" f5.5-6.
Yes, customs and shipping won't be cheap. It's a telescope to last though.
Any thought is welcome of course.