Horsehead from the Queensland Astrofest and 3 nights at Leyburn

[TimberLand (Justin)]

After stacking, would tell me that values went to high and caused an integer value to go so high that it started back at zero.

This would be possible in basic software for stacking but PI does this in 32 bit floating point as standard so shouldn't be a problem with too higher value.

Still a mystery.

For the meeting this week I will be out of town again, but on a plus note I will be clearing and levelling the site for the observatory and a couple of concrete pads beside it instead.

Justin

[firstlight (Tony)]

Well I've reproed this image again. I think the problem was that I didn't have enough subs from the Astrofest, and PI wanted to use "percentile clipping" for thiose subs, while wanting "Windsorized Sigma Clipping" for the rest (changed from one then it would ask for the other).

The long and the short of it is that I dropped the subs from the Astrofest, which were only half a dozen or so 5 minute subs, and I seem to have been able to extract a bit more detail in the bright regions. Once again the colours seemed more natural to me, although I boosted the saturation a bit to deepen the emission nebula colour.

I think I'll rest on this repro until I get more data... maybe another dark weekend at Leyburn next month?

[firstlight (Tony)]

Actually looking at it again this morning I think I liked the result without the saturation boost.

Any opinions?

[TimberLand (Justin)]

Nice repro Tony. I don't know which one I like the best. That is a great effort, and good catch on the clipping in the processing, imagine how hard that sort of image would have been to get 20 years ago. I was looking at some of my old film attempts in this area the other day, and yours smashes the old film out of the ball park.

I use median stacking with the old DSI to keep the random hot pixels under control. It also seems to keep the background a bit smoother, but that could just be me. A better camera might change my mind but we will see in the future.

Justin

[firstlight (Tony)]

Thanks Justin. I'm fanging out to image this area again and add to the capture. The nebulosity seems to go on forever.

How did the concrete pour go? You going back to the farm this weekend, or are you able to make the Combined Meeting tomorrow night??

We have a few options for the next dark weekend, we just need to decide.

[alpal]

Hi Tony,
I think you've done an excellent job with the processing.


I assume you used:

NEQ6 , Williams Optics 110 Megrez, WO type 2 0.8x field flattener,
fl 524mm, Modded Canon 450D.

How were you guiding it?
There seems to be field rotation.
It looks like the mount was not polar aligned.

cheers
Allan

[firstlight (Tony)]

Originally Posted by alpal

Hi Tony,
I think you've done an excellent job with the processing.


I assume you used:


How were you guiding it?
There seems to be field rotation.
It looks like the mount was not polar aligned.

cheers
Allan

I know what you are saying, however I am guiding on Alnitak, with a side by side setup with an Orion 80mm guidescope and a QHY5. I have drift-aligned and the stars don't move out of the reticle after 15 minutes. I'm thinking there might be some flexure in the rig perhaps.

[alpal]

Originally Posted by firstlight

I know what you are saying, however I am guiding on Alnitak, with a side by side setup with an Orion 80mm guidescope and a QHY5. I have drift-aligned and the stars don't move out of the reticle after 15 minutes. I'm thinking there might be some flexure in the rig perhaps.

Yes Tony,
It's strange because the center stars are round.
Maybe an OAG would help?

cheers
Allan

[gregbradley]

I find there can be quite a difference in autoguiding accuracy depending on the star. Very bright stars are not good choices as the CCD will bloat and as the software calculates the centroid point that would be hard.
Pick a single star (not a binary which are common) mid brightness, not too bright so it is oversaturating the wells of the camera.

The first thing I do if I get worse guiding errors is pick another guide star and see how that goes. I often see errors halve.

But apart from that flexure is going to be problematic unless you use an OAG.

By the way a single run of HLVG plugin for Photoshop would enhance your image a tad. It gets rid of excess green.

Greg.