Ha Swan

Peter Ward · #1 02-08-2019, 12:08 PM

Murphy's law is such when if it isn't cloudy then the seeing has to be as calm a pot of boiling water. Anyway despite the 3 arc sec stars I was happy to finally give my languishing AstroDon's and external guider a bit of a run.

Have to say the un-attenuated guide stars made life so much easier.
Guide stars a plenty

The field is very similar to M&T's recent post...but the exposure is a little longer.

Interestingly the 50mm square AstroDons give brighter stars orthogonal spikes to the secondary spider variety, something I had not really noticed with 65mm filters...but they do not seem to suffer much from halos or reflections, which was nice to (not) see.

My take of M17 is here

gregbradley · #2 02-08-2019, 02:27 PM

Hmm, a bit soft for your Alluna there Peter. Nice overall but not at the level of your usual top notch. That's more like something I would pump out hehehe.

Poor seeing?

Greg.

Peter Ward · #3 02-08-2019, 03:05 PM

Quote:

Originally Posted by gregbradley

Hmm, a bit soft for your Alluna there Peter. Nice overall but not at the level of your usual top notch. That's more like something I would pump out hehehe.

Poor seeing?

Greg.

Ta Greg.

The seeing wasn't just poor, it was tragic.

My system usually guides within 0.5 pixels or so. I was watching excursions in RA and Dec of 3 pixels
(which BTW is exactly why I think direct/absolute encoder drives have dubious benefits...i.e. if the Dec axis is not driven,
how does it correct 3 pixel atmospheric wandering without guiding? )

gregbradley · #4 02-08-2019, 04:21 PM

I thought it must have been seeing. Its a good image by normal standards just not at the level you normally do.

The seeing here at my dark site at nearly 800 metres last night was magical. But I was doing nightscapes so a bit unutilised. The Milky Way was mesmerising. So vivid.

Greg.

Peter Ward · #5 02-08-2019, 06:15 PM

Quote:

Originally Posted by gregbradley

I thought it must have been seeing. Its a good image by normal standards just not at the level you normally do.

The seeing here at my dark site at nearly 800 metres last night was magical. But I was doing nightscapes so a bit unutilised. The Milky Way was mesmerising. So vivid.

Greg.

Ah. Yes. A dark site. That would be nice.

I've been looking for something similar a while, but so far no joy.

Placidus (Mike and Trish) · #6 02-08-2019, 08:54 PM

Excellent depth, especially for the exposure x aperture x bright city lights.

Peter Ward · #7 02-08-2019, 09:32 PM

Quote:

Originally Posted by Placidus

Excellent depth, especially for the exposure x aperture x bright city lights.

Thanks M&T

I just replaced the image file with fresh data from tonight's imaging run...could be better, but much mo' snappier...

As for city lights...with a 5nm filter I believe you could image from Pitt Street
or for less foot traffic, Observatory Hill and still get the same S/N.
..i.e. they are essentially immune to light pollution.

Andy01 (Andy) · #8 03-08-2019, 09:23 AM

That’s looking great, good separation between the dark dust (bottom left) & space, plenty of nice details. Will be interesting to see it in colour

Slawomir (Suavi) · #9 03-08-2019, 01:10 PM

Quote:

Originally Posted by Peter Ward

As for city lights...with a 5nm filter I believe you could image from Pitt Street
or for less foot traffic, Observatory Hill and still get the same S/N.
..i.e. they are essentially immune to light pollution.

I have noticed a significant improvement in SNR after moving from Brisbane’s inner city to a small town. For example - good flats were essential even for 10-minute 3nm Ha subs on a moonless night, while in Prossy, as long as the bright one is not up, I can easily get away without flats when shooting 20-min 3nm HA subs, unless I’m chasing the faintest bits and stretching like mad. Background noise is much less here in Prossy in subs taken through 3nm filters, with the same scope and camera. Good narrowband filters like Astrodons help big time, but from my experience are not immune to strong light pollution. I strongly recommend a dark, or at least a darkish site

gregbradley · #10 03-08-2019, 02:59 PM

Ah yes, the latest version of the image is very nice. Lots of sharp detail there.

Greg.

Peter Ward · #11 03-08-2019, 04:48 PM

Quote:

Originally Posted by Slawomir

I have noticed a significant improvement in SNR after moving from Brisbane’s inner city to a small town. For example - good flats were essential even for 10-minute 3nm Ha subs on a moonless night, while in Prossy, as long as the bright one is not up, I can easily get away without flats when shooting 20-min 3nm HA subs, unless I’m chasing the faintest bits and stretching like mad. Background noise is much less here in Prossy in subs taken through 3nm filters, with the same scope and camera. Good narrowband filters like Astrodons help big time, but from my experience are not immune to strong light pollution. I strongly recommend a dark, or at least a darkish site

LP spectral emissions are almost non-existent in the H-alpha spectral region. In fact depending on where in the spectrum you want to image, (e.g. deep IR) daylight is fine...so long as you have good transparency and low humidity. The major attenuation effect I find is simply sky transparency...which, sure, away from urban aerosols/air pollution is likely to be better.

I know you Banana benders also have a penchant for burning coal (who said Adani ? )

.... but can't say my local aerosol exposure is the same.

The air quality in southern Sydney and sky transparency is surprisingly very good, with significant green space in the Royal National Park to the east, Heathcote and Holsworthy reserves to the south and south west.

But as for my Northern sky......