Comet

[Fay]

I did an image of the comet with the Canon, last night.
I seem to have a fainter version of the comet just below the main one. Do you think the images have not aligned correctly? I have tried to see if any stars are duplicated, but can't see any.
Is it possible the comet could throw a reflection somehow?

Fay

[Ian]

can you post the image? It does sound like some sort of internal reflection...

[JohnP]

Fay - when you stack the image are you aligning on the comet or the stars (they move at different rates) - if stars then I suspect it is just movement of the comet over the time you were taking the images...

John

[Fay]

17 x 30 secs Comet Holmes. Taken with Canon 350D. Showing slight reflection below comet. 

[JohnP]

Umm... maybe just one misaligned frame & only bright comet shows up... Great imae though - was it through ZS66 or ED80...

John

[Ian]

I'm with John, I don't think the stars are quite bright enough to show up. Except the one at around 7 o'clock but it's reflection would be off frame at the bottom.

To be sure, if it was a reflection, it'd be evident on all of subs...

[Fay]

I have looked at all the subs & cannot see a reflection. I have compared the star patterns on the subs & they seem ok. 

[Mike]

What about a galaxy or small nebulae?

[Fay]

Yes, I thought about that as well Mike.

[mickw]

OK, this weeks dumb question.
Do you stack the subs then process the result ?
Could an internal reflection be present on the subs but only visible when adjusting levels ?
Mick

[Fay]

Mick,

I am going to delete last night as I had a few strange things happening. I used the Canon & when I looked at the subs, there were quite a few that had the same capture time, all RAWS no JPEGS. Don't know if anyone knows the reason for this. Even 2 of the darks had duplicated

[mickw]

I assume you set the cameara to take RAW only.
Did you set up the camera to take bracket exposures, should be able to tell if you look at the RAW data.
Clutching at straws here 
Mick

[Fay]

RAW only. Never heard of bracket exposures

[mickw]

Bracket exposures should be in the cameras menus somewhere.
The idea is that for one release of the shutter, the camera takes extra images either side of the chosen settings - usually exposure plus or minus 1 or 2 stops.
Can be quite handy, unless you are taking 17x30  -  That could end up 51x30 
Mick

[Mike]

I am going to delete last night....

NEVER delete astronomical data !!!  Noooooooooooooo!!!!!!!!!!!!!! 

[Fay]

I will have a look at that in the Canon book, Mike.

[Fay]

Mick

[Rick]

NEVER delete astronomical data !!!  Noooooooooooooo!!!!!!!!!!!!!! 

Even if it appears to be in a mess, don't delete the original data. You may be able to un-scramble the mess at a later date, and when something is changing as rapidly as this comet you may have the only raw data that captures a particular event at a particular instant.

[Fay]

I have not deleted the comet info. I just wrote off the night