Cygnus Loop with Full Frame ASI6200MM

w7ay

Cropped HOO Image of Cygnus Loop from a full frame ASI6200MM with William Optics Pleiades68 and 5nm Chroma H and O filters. 30x180 sec each at 10 dB (HCG) gain (3 hours total image acquisition, Bortle 5 to Bortle 6 skies); stacked and combined using AstroPixelProcessor. No calibration frames (no bias, no darks, no flats.)

The original stacked frame is this wide before cropping and post-editing with Affinity Photo:

Less scaled crop of the Western Veil:

and Eastern Veil:

There is no attempt at sharpening nor star substitution, the star colors and shapes are what the sensor saw. Autoguided RST-135e mount.

I did spend some effort adjusting the backfocus -- needed to get the backfocus to within 0.05mm for the fast optics. Albeit, my copy of the Pleiades68 is not 260mm/f3.8, but more like 273mm/f4.0 (some hanky-panky marketing by William Optics).

Wide field can be quite addictive.

Chen

Astrop

Some good detail in that image.

How are you finding the scope, I was looking at it but then read all the stories about BF issues and then WO needing to send customers a new BF spacer adaptor. Does the focus remain stable throughout a session?

w7ay

Astrop How are you finding the scope, I was looking at it but then read all the stories about BF issues and then WO needing to send customers a new BF spacer adaptor.

The fast optics just needs very precise backfocus. Even 0.05mm off (not typo -- less than 0.1mm off) can cause corner stars to be bad. I have this adjuster permanently installed to achieve the precision needed:

https://www.sharpstar-optics.com/Products_1/83.html

I step 0.025mm at a time once I get close to the correct backfocus. Mine came out to be about 0.15mm from the advertised "55mm," once the filter glass thickness is accounted for.

Those who complained on Cloudy Nights are probably just stepping 0.1mm at a time using washers. Too rough for an f/4 -- I think they are used to slow scopes such as the Askars and RedCats.

(By the way, the scope also comes with a built-in tilt adjuster.)

Does the focus remain stable throughout a session?

Donno. Because I am used to the Baby-Q's requirement of accurate focus to achieve its small spot size, out of reflex action, I always refocus when I see a 1ºC ambient temperature change.

Some good detail in that image.

Very small stars once you have the backfocus adjusted.

The details are not as good as that from the 1.01x flattener of the FSQ-85 -- but then, the Baby Q can barely frame the east and west veils in the same plate! (The Baby-Q definitely has smaller star FWHM, with star colors only a true fluorite can produce.) I am waiting for the new QB 0.73x reducer from Takahashi, which should give me a 44mm image circle at 330mm focal length (the current reducer from Tak has an abysmally small usable image circle). The Pleiades 68 will probably not hold a candle to it, and will likely be retired when that reducer arrives. In the meantime, the speed of the scope, together with the sensitivity of a monochrome camera is providing me with lots of fun.

Chen

Astrop

I've got that adjuster for this exact purpose, it makes for an excellent tool where as you say, spacer adjustment isn't fine enough. I'm running my Zenithstar 61 at F3.8, but haven't messed around fine tuning, but may get around to it eventually, whether it will flatten the field at the edges is another matter.

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