M20

Hi All

It's been a while since I posted here so here It goes: This shot was taken with a
WO 105 ED triplet through a SXV-H9C and the exposures were 120sec x 30 ,captured and aligned and stacked in AA3 and processed in PS7.

Cheers

Louie

Attached Image:

Great shot Louie! 8)

Nice work Louie! I love this object.... the combination of colors is so beautiful, and you captured it well.
Cheers,
Tyler

Just beautiful Louie. I sure wish I could work color like that.
Good to see another posting from you.
Larry

Welcome back, Louie, and well done on this image.

dan kowall

Hi Louie,

Good to see you back. Nice shot overall. It seems a little soft for some reason. Was your focus slightly off or was the stacking a bit off?

One thing I am finding with the one shot colour and I am assuming here it is the same for the SXV is that because of the Bayer matrix you can't rotate your images when aligning them or you can't extract the colours. So that means (if I have this right) that polar alignment becomes more critical. Even if you are autoguiding if your polar alignment is off you will get slight rotation between images. This seems to be enough to make it extremely hard to get the colour out and you'll have no choice but to align the images horizontally and vertical but not rotationally. Or you could convert to colour and align and stack the images using something like Images Plus in which case it is not a problem at all ( I think). But it would require a different approach and workflow.

So, if you then align the images and they have a slight rotation to them one to the next the resulting combined image could look a bit soft like that. In experimenting with a M20 shot similar to yours and the polar aligment was off a little bit that was what I found out. Also reading the Sbig application notes on how to process one shot colour brings up this point about the differences with one shot colour.

Do I have that right? This is new to me.

The WO105 is that the TMB lens? Also check the collimation. I had a WO 80mm triplet fluorite and it had coma off axis because the focuser was out of collimation with the lens. I had to fix it with a metal packer which worked. The lens should be one of the best on the planet.

Another recommendation from Sbig and it probably holds true for your SXV is best results come from longer exposures. Try 3 x 30 mins rather than 9 x 10mins. I assume that is because to get the signal to noise ratio on the same level as the mono you need to shoot approx 3-4 times longer due to the Bayer filter matrix on the chip.

The good news of course is you don't need a filter wheel, you don't need to refocus between filters and the colours as in balance rather than working out what the balance is for the tricolour images (its just time saving).

Have you found any advantage to splitting the image into 4 channels and then combining versus simply doing a Bayer convert on the final combined image? I haven't seen an adavantage yet in my limited testing but interested to know what your experience is.

These one shot colour cameras I think have unfairly been given a bad rap in the past. I quite like mine so far. I can directly compare its performance to a mono ST2000XM and I don't see much difference so far and it is a lot more convenient. The above seems to be the main consideration in handling these cameras. Otherwise they seem much the same.

Best,

Greg.