M57 - Experiments in thick fog!

[CKemu]

Clear night, no work - perfect! Well apart from the fact that my field site away from the lights had extremely localised weather, with rolling fog and strange temperature differences, the ground felt icy cold, yet above the initial layer of fog/mist it was much warmer.

Tonight was a test run to see if I could effectively barlow in on a small DSO like M57, and get reasonable tracking, exposure and any gain in detail. My scope is the 8" LX90 with an f/10 tube @ 2032mm f/l - so a 2x barlow takes that to f/20 @ 4064mm f/l - excluding the cropping/magnification factor of my Nikon D300's CMOS sensor.

Now my lens was covered in thick dew, so this test isn't 100% representative - however I did note:

Tracking / guiding was "reasonable" my stars started looking a little "eggy" between the 10-15 minute "zone". The magnification provided was far more significant than I expected, however exposure of 15 minutes @ ISO 1600 (the mid point ISO on my DSLR) was extremely noisy, this combined with eggy stars caused DSS to tell me it couldn't find stars.

So I am not entirely convinced that the pay-off will be there if I ever did manage to stack the images.

Below are two sub frames - untweaked, just cropped to 100% original size.

Frame #1: ISO 1600 at 2 minutes - no barlow

Frame #2: ISO 1600 at 10 minutes - 2x barlow

Any feedback and thoughts regarding the "worthwhile-ness" of attempting an imaging run with a barlow and this object (sans dew)?

[Gina]

Quite good without the barlow - should be good enough to collect a dozen or two to stack and get some good results Dump the Barlow - f10 is quite enough