Flaming Star - "Reprocessed"

[JohnH]

EDITED

I have now reprocessed and removed my L data and using Ha (image time now 3hours 15mins). The weird spikes are disguised - they are still in the GRB layer.

This is the result:



This was the previous version:



I had a go at this nebula on Thursday night after an effort to collimate my Sharpstar 15028 HNT properly and have a go at the tilt. The collimation seems better but I think there is still a tilt diagonally across the image. Usual problem with diffraction spikes present although, to my eyes, slightly less obtrusive. I think it could have done with being centred slightly to the left to get more of the fainter Hydrogen cloud.

Something obviously went wrong as there were no clouds and no Moon!

HaL HaRGB (I hope that that makes sense).
Location: Bromley (Bortle 7)
Total imaging time: 4 hours
ASIAir Pro control (a version PHD guiding software with multistar guiding is built in)
Mount: iOptron CEM25P

The image is about 1.8" per pixel, I have not checked the PHD log but it looked as though even in my hands guiding was within about 0.3 to 0.5 pixel.

The Flaming Star Nebula (Caldwell 31) is an interesting object. It appears to be a cloud of Hydrogen gas but there is illumination from star Auriga AE (bright star in the middle of the image) which is passing through the cloud having been ejected from Orion.

Regards,

John

[ApophisAstros]

Nice target and processing here of but shame about no star colour.
Roger

[JohnH]

Hi Roger,

I was disappointed about that. The RGB combination had star colour but I lost it at some stage. I will probably take a deep breath and re-process slowly. I also noticed that I had left a bit of vignetting top right and will see if I can remove that.

Regards,

John

[ApophisAstros]

Hi Roger,

I was disappointed about that. The RGB combination had star colour but I lost it at some stage. I will probably take a deep breath and re-process slowly. I also noticed that I had left a bit of vignetting top right and will see if I can remove that.

Regards,

John

I find it a tightrope sometimes when trying to get everything right.
Still well done getting something as imaging time is getting as rare as Hens teeth these days.
Roger

[Carole]

That's come out really well john albeit the star spike issue is still to be sussed out.  But in general the stars seem much better processed than your previous results.

I don't live far from you and I could easily pop down and take a look and also discuss processing.  Though I am really only experienced with photoshop. 

Send me a PM with your E mail address so we can discuss further.

Carole

[Roberto]

Great result John!  Very well framed.  The diffraction spikes still seem weird to me.  Can you post images of a defocused star? That will help ascertain what is causing them.

Roberto

[JohnH]

Thanks Roberto. I will try to do do a defocused star next time out.

In the meantime, I have nearly finished a re-process of my data with a different strategy which I will edit into my original post. Strangely, I omitted my Luminance data and used the Ha instead. This has almost completely eradicated the errant diffraction spikes. It has also retained the star colour data.

Regards,

John

[Carole]

Aha, maybe you have a hair or something accross your Ha filter.

Carole

[JohnH]

I have posted a re-processed image by editing my original post.

My theory is that the Ha images I used for luminance were under exposed (120 seconds) and therefore whatever was causing the spikes is much less obvious.

Regards,

John

[Carole]

Yes a defocussed star image would be very useful. It showed up my focuser protruding into the light path.

Carole

[Carole]

The new process is much better John, much better colour and much better star colour.

However I think you may have some coma there showing up much worse in the red channel.  If you look to the corner stars the red is enlongated towards the corners and much better in the middle.  This is normally caused by the spacing not being correct with the coma corrector.  Though this seems worse at the bottom two corners than the top two corners, so there could also be some tilt going on.  Don't you just love this hobby!!!!
Taken me years to get this right.

Carole

[JohnH]

Carole, I believe that you are correct on both counts!

Logically, I imagine that I should try to clear the tilt first, then I can get a grip on the spacing.

In my mind there is also the thought that removing tilt will make focus more consistent. II do not know where bin the field the system selects a star for autofocus. I there is tilt, this must introduce variation.

Where would the fun be if it was easy ...

John

[The Thing]

Hi John, what capture software runs on the ASIair. You should be able to configure the autofocus to use the central section of an image rather than the whole thing and also limit the number of stars used. It's basically a Raspberry Pi so it must be either Kstars/Ekos or CCD Ciel.

[JohnH]

"Hi John, what capture software runs on the ASIair. You should be able to configure the autofocus to use the central section of an image rather than the whole thing and also limit the number of stars used. It's basically a Raspberry Pi so it must be either Kstars/Ekos or CCD Ciel."

Hi, the ASIAir Pro has its own software. Some of it his licensed from elsewhere (eg PHD2) but the most of it is their own. They emphasise ease of use for dummies like me! As far as I know star selection is automatic but I will have a deeper look.

In the meantime, I have been collimating with a new laser collimator (I have checked its own collimation and it seems good, the result is confirmed by my Cheshire collimator). This laser self centres in the focuser and the beam has a crosshair to make centring the dot more precise. The point of all of this is that this is what the beam looks like:



You can see the crosshairs but also other spikes which are similar to those in my images. I have absolutely no idea whether this is significant or mere coincidence.

Regards,

John