Eta Carina; Missed it by that much

[Atmos (Colin)]

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

[Placidus (Mike and Trish)]

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 (Lee)]

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 (Colin)]

Originally Posted by 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

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

Originally Posted by codemonkey

Nice one Colin. Great colour, nice and sharp!

Thanks Lee

Originally Posted by 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.

Thanks Greg, you're right on both accounts It's mostly because it didn't point where I wanted it to
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.

[Andy01 (Andy)]

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

[Atmos (Colin)]

Originally Posted by 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.

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.

Originally Posted by Andy01

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

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!