Eta Carina; Missed it by that much

[Atmos]

I took this back on the first few days on Jan, its one that never quite turned out but I figured I'd post it anyway a few months down the track. It was used as a filler at the end of a night after I'd photographed NGC 2070 and for some reason after focusing it didn't quite centre itself on Eta Carina. With only 36 minutes of data taken from a suburban light polluted back yard I'm pretty happy with the overall detail.

Mewlon 250 F/10
ASI094
36x60s at Unity gain.

I'm pretty sure the issue came from having MaximDL having access to the mount as opposed to it just being used as a slave for camera and focuser control.
FWHM moves from 3.8 pixels to 4.3 out at Eta Carina which is noticeable due to the non-round stars. at 0.4"/pixel it means a FWHM of 1.5-1.7" which I'm pretty happy with. Much better than I was expecting to get. There is some triangular stars starting to show that I haven't bothered trying to fix, I'm assuming that shooting on both sides of meridian would leave me with perfectly round stars though.

Link for pixel peepers (https://www.astrobin.com/full/et18w2/0/)

[Placidus]

Nice timing. We watched the Maxwell Smart movie yesterday!

A great result for such a short exposure. Nicely nuanced. The HH jets toward 3 o'clock came out well.

Are the triangular stars something to do with the 6 diffraction spikes?

Best,
MnT

[codemonkey]

Nice one Colin. Great colour, nice and sharp!

[gregbradley]

That's quite an appealing image really. I think you are being overcritical of it.
The misshapen stars are only really visible in the full res image. A small amount of tilt is there as well as top right corner seems most affected.

Greg.

[Atmos]

Thanks MnT :)
Is the HH Jet around Mystic Mountain?

The 6 spikes come from the 3 spider veins in the older Mewlons. You get 6 fainter as opposed to 4 brighter. My hunch is that it is caused by collimation. I've removed the mirror a couple of times (the last time was to install the corrector) and so far all I've done is used a collimation scope to get it right. Haven't touched it under the stars yet. I get triangle stars with my RH200 and I know that's caused by trefoil astigmatism but that goes away if I shoot on both sides of meridian.
At 1.7" the stars are round, at 1.5" they start losing their shape. It's really easy to fix but I didn't feel it was worth the effort :)



Thanks Lee :)



Thanks Greg, you're right on both accounts :P It's mostly because it didn't point where I wanted it to :lol:
I do need to fix up that corner at some stage, I know it's the bottom left corner (I flipped the image and have the camera at the same orientation as the OTA) but I'm pretty lazy about it.

[Peter Ward]

Some technical quibbles...but really all said and done, a very fine Eta.

There is so much "good stuff "(and often invisible at shorter FL's) there that you have managed to bring to the fore.

Nicely done. :thumbsup:

[Andy01]

^+1 What Peter said - I like the framing too - it's really quite a nice image - well done! :thumbsup:

[Atmos]

Thanks Peter, having photographed this several times with smaller wider instruments I get what you mean. “The Finger” just naturally pops out and has detail where as, in the past, it’s taken quite a bit of processing to get the same look and feel.
Stars are also smaller which shows the nebulosity off more.



Thanks Andy :)
I’m personally not fond of the framing as it feels too heavy on the top right compared to the rest of the frame. You’re more atune to framing though!