The Gabriela Mistral Nebula

nebulosity. (Jo) · #1 11-02-2014, 08:25 AM

Was able to get another image this morning, haven't got the guiding sorted yet so just 40x 40 second subs with the Canon 1100D at ISO 6400 and the 8 inch f6 newt.

Hope you like it, the large version is Here.

Cheers
Jo

PS, could anyone tell me what is making the stars on the left side of the image out of focus

as far as I know everything was in good collimation.

rcheshire (Rowland) · #2 11-02-2014, 09:36 AM

One of my favourites. I may have this all wrong, but the CA on many of the brighter stars is to one side and the elongation increases with distance from the bottom right corner which looks almost concentric - is the camera in alignment?

EDIT: it looks like one or some subs may have been subject to vibration or a knock.

blink138 (Pat) · #3 11-02-2014, 10:28 AM

thats nice jo............. i have never even heard of that one, its quite pretty!
what is its designation?
pat

DavidNg (David) · #4 11-02-2014, 10:46 AM

Hi Jo,

Good image and color despite limited data.
The copyright right in the middle of your image has ruined this fine image

perhaps place at the bottom somewhere?

I dont think they are out of focus stars at edges, you will probably need a field flatterner ?

Regards
David

cometcatcher (Kevin) · #5 11-02-2014, 11:10 AM

Hi Jo, that is a beautiful shot. *Edit, found NGC3324 NGC3293.*

The bloated stars on the left hand side of the frame is due to the secondary mirror being slightly out of collimation so the light strikes the focal plane at an angle, making the focus different for each side of the frame.

One of the "joys" 'cough' of making one's own newtonian scope (I've made a dozen and still have trouble getting them perfect) is getting the secondary in the correct position. They look okay for visual use, but the slightest shift will show on a photo. For photography they have to be perfect! In your case it looks like the secondary may be too far from the primary. Screw out the center screw on the secondary holder a couple of turns, re-collimate and do a quick single frame to test. Or I might have that backwards LOL. We're only talking maybe 1 mm or so here.

Here is a pic through my 6 inch F6 home made Newt of Miaplacidus with the same problem but opposite side.

For perfect stars all across the frame an F6 Newt still needs a field flattener but it won't be as extreme as a faster scope.

cometcatcher (Kevin) · #6 11-02-2014, 11:33 AM

Another example. My secondary is also not quite in the middle so the corner is out. I made the secondary holder / spider as well which is why everything is crooked on it lol.

multiweb (Marc) · #7 11-02-2014, 11:33 AM

Lovely colors.

nebulosity. (Jo) · #8 11-02-2014, 12:17 PM

Quote:

Originally Posted by rcheshire

One of my favourites. I may have this all wrong, but the CA on many of the brighter stars is to one side and the elongation increases with distance from the bottom right corner which looks almost concentric - is the camera in alignment?

EDIT: it looks like one or some subs may have been subject to vibration or a knock.

Thanks Rowland, from what Kevin is saying it might be the secondary mirror,

Quote:

Originally Posted by blink138

thats nice jo............. i have never even heard of that one, its quite pretty!
what is its designation?
pat

Thanks Pat! I think it's called NGC 3324, its just above and to the right of Carina nebula.

Quote:

Originally Posted by DavidNg

Hi Jo,

Good image and color despite limited data.
The copyright right in the middle of your image has ruined this fine image

perhaps place at the bottom somewhere?

I dont think they are out of focus stars at edges, you will probably need a field flatterner ?

Regards
David

Thanks David, the copyright thing was done automatically by astrobin, unfortunately it can't be moved, I'll see if I can get rid of it.

Quote:

Originally Posted by cometcatcher

Hi Jo, that is a beautiful shot. *Edit, found NGC3324 NGC3293.*

The bloated stars on the left hand side of the frame is due to the secondary mirror being slightly out of collimation so the light strikes the focal plane at an angle, making the focus different for each side of the frame.

One of the "joys" 'cough' of making one's own newtonian scope (I've made a dozen and still have trouble getting them perfect) is getting the secondary in the correct position. They look okay for visual use, but the slightest shift will show on a photo. For photography they have to be perfect! In your case it looks like the secondary may be too far from the primary. Screw out the center screw on the secondary holder a couple of turns, re-collimate and do a quick single frame to test. Or I might have that backwards LOL. We're only talking maybe 1 mm or so here.

Here is a pic through my 6 inch F6 home made Newt of Miaplacidus with the same problem but opposite side.

For perfect stars all across the frame an F6 Newt still needs a field flattener but it won't be as extreme as a faster scope.

Thanks Kevin! Great to hear your diagnosis

should be easy to fix. I was starting to worry that the focuser was tilted or something.

by the way, I like your diffraction spikes! how come there is six?

Quote:

Originally Posted by multiweb

Lovely colors.

Cheers