M1 Crab Nebula ASI120MM C8

maurizio

The Crab Nebula from a hard light polluted urban sky during a "luky" clear night with even a good seeing.... 8-)

Scope: C8 / Foc.Red. 850mm

Camera: ASI120MM /IDAS LPS Filter /ZWO RGBL FilterWheel

Cooling: DIY Peltier TEC (DeltaT up to -18/-20°C @12V 2A)

Capture: Fire Capture

SW: Registax / Paintshop

70x R/G/B @T 5sec, Gain 85%, Bin 2x2, -Dark

100x Lum @ T 10sec, Gain 85%, -Dark

Sensor Temp: -8°C

Note:

To avoid dew formation on the optical window it was necessary to put some silica gel inside the nose of the camera between the optical window and the LPS filter. A few silica gel pellets can dry the small volume inside the nose for a long time (months) if you leave the LPS filter in place.

Clear Skies!

firstc8

Very nice. Mono clearly has much higher sensitivity.

I captured the same with my C8 F3.3 reducer. 32 sec 50 lights, 20 darks and 20 biases, gain 60 unguided. Average seeing condition with typical light pollution. DSS, Sharpcap and Photoshop.

maurizio

Thanks FirstC8.

What is your Mount? Mine is an ioptron ieq45pro. I'm not guiding too.

I'm assuming that your M1 is taken with a 120MC.

32x50 is 1600sec. Mine was 2050sec total exp and with higher gain but yours has a f.3 and mine an f.5 optic.

Nonetheless even in your picture the pulsar is visible. Good job! ;)

firstc8

AVX mount. I have since fine tuned my mount to track for up to 150s without star trail.

I said f3.3, actually I stacked f6.3 with f5. I will try prime focus next time. I suspect too many lenses might have impacted the seeing. Will also take shorter exposures and more frames.

Trying to find out how much I can do with the 120mc.

maurizio

I said f3.3, actually I stacked f6.3 with f5

Actually I'm stacking the standard Celestron f.3FR with a small achromatic doublet from a binocular used as a FR.

I put this lens inside the nose of the ASI camera between the LPS and the optical window and this combination provides a resultant FR of f.5 (measured on the picture). Thanks to the small size of the sensor the picture quality is not affected very much and the gain in luminosity and field is worth the added complexity IMO.

The C8 prime focus is f and is very dark and very sensitive to tracking error. My attempts on DSO were far less than average...