Optical Tube Reflection with The Horsehead

[CapturingTheNight (Greg)]

Hello,

Imaged The Horsehead and The Flame Nebula this morning and after processing I noticed what looks like a reflection of the optical tube just to the top left of the bright star Alnitak. My question is- Is this common with a bright star that is not in the middle of the frame or was there something wrong with my setup like collimation??? I thought I had my collimation spot on (I use a laser collimator prior to each imaging session). Of course I should be able to clone it out of the image but I ideally don't want to do that if It can be avoided at the imaging stage. Any thoughts on what is the cause and how to avoid it???

Telescope used is a 10" F/4 Newtonian running on a NEQ6 Pro Mount, with guiding done with a Synguider through an 80mm ShortTube Guidescope. 12 X 5min exposures @ 800ISO with a unmoddified Canon EOS 1000D. Dark Frames (10 X 5min) subtracted.

Cheers

Greg

[RobF (Rob)]

That's a corker of an image Greg and certainly doesn't look like a beginner's image!
Very bright stars certainly can cause reflections and Alnitak is notorius for these problems. I'm not sure in your case exactly where the reflection would be - did you have a coma corrector in there?

[mithrandir (Andrew)]

Originally Posted by obsidianphotos

Hello,

Imaged The Horsehead and The Flame Nebula this morning and after processing I noticed what looks like a reflection of the optical tube just to the top left of the bright star Alnitak. My question is- Is this common with a bright star that is not in the middle of the frame or was there something wrong with my setup like collimation???

As Rob says Alnitak always causes trouble with reflections. Do you have a dew shield on the scope? That helps with keeping out of field bright stars under control.

[Alchemy (Clive)]

Clearly it's reflection off a coated surface somewhere.
I had a look through some of my images for halos, and those to the outer field are slightly off centre even in a refractor. It's probably trying to find which surface is giving you the grief and replacing it with a better quality one.

My 3c worth.......

[CapturingTheNight (Greg)]

Originally Posted by RobF

That's a corker of an image Greg and certainly doesn't look like a beginner's image!
Very bright stars certainly can cause reflections and Alnitak is notorius for these problems. I'm not sure in your case exactly where the reflection would be - did you have a coma corrector in there?

Awwww.... Rob. I really appreciate that. I'm not sure what to class myself as on here. I have only had my astrophotography setup for 4 months so very much just starting out, but prior to that I did a lot of fixed tripod astro work and home made barndoor tracker stuff as well as other general photography. I also did a heap of research on how to take and process astroimages before I started so I would hit the ground running so to speak and not be tearing my hair out too often. It still happens from time to time but I am very glad of all the research I did to be doing shots like this already.

Ah yes. I forgot to mention that yes I do use a Baader Coma Corrector. That might be it.....I'll try a few test shots without it one night and see if that's it. I'm pretty sure I need a Coma Corrector with the F/4 scope but if it is the cause I might need to track down a higher quality one.

Originally Posted by mithrandir

As Rob says Alnitak always causes trouble with reflections. Do you have a dew shield on the scope? That helps with keeping out of field bright stars under control.

I might have to look at getting a dew sheild for the reflector. I have not bothered with one yet as my guidescope gives into dew long before any dew makes it's way down the bottom of the newt. Thanks for the suggestion Andrew

Originally Posted by Alchemy

Clearly it's reflection off a coated surface somewhere.
I had a look through some of my images for halos, and those to the outer field are slightly off centre even in a refractor. It's probably trying to find which surface is giving you the grief and replacing it with a better quality one.

My 3c worth.......

Thanks for your thoughts Clive. It's good to know that it is as I thought it was and not a collimation issue. I'll try without the coma corrector one night and proceed from there.

[Alchemy (Clive)]

You can try without the coma corrector, as a test, but you will still need one at f4.

I had a reflection caused by the IR cutoff filter at the front of my camera, I replaced it with an astronomik one and it went away.

But in all honesty you only ever have a problem on the brightest stuff.... Try m45 and you will see what i mean.

Simplest way to test is just go and target the brightest star around and remove any reflective surfaces until you have a winner. Keep in mind it could be reflecting of the actual CMOS chip in the camera .... You cant remove that .

I wouldn't panic. It is as rob says common to have reflections, I've seen rgb images with three different colored halos around this very star due to reflections from the filter surface http://www.iceinspace.com.au/forum/a...se.php?a=83606
I only put this up to show how easy it is to get them and it's also a very similar composition as yours.

Again don't panic about it 99% of the time you will get nothing.

[ZeroID (Brent)]

That is one awesome image despite the wee reflection. The brilliance and diffraction spikes of Alnitak and the sharpness and colours of the whole shot are just amazing. That one would go up on the wall. Clone out the wee ring if you have to but take credit for a stunningly sharp and beautiful shot. I just love those crepuscular rays coming away from Alnitak
Well done.

[CapturingTheNight (Greg)]

Originally Posted by Alchemy

You can try without the coma corrector, as a test, but you will still need one at f4.

I had a reflection caused by the IR cutoff filter at the front of my camera, I replaced it with an astronomik one and it went away.

But in all honesty you only ever have a problem on the brightest stuff.... Try m45 and you will see what i mean.

Simplest way to test is just go and target the brightest star around and remove any reflective surfaces until you have a winner. Keep in mind it could be reflecting of the actual CMOS chip in the camera .... You cant remove that .

I wouldn't panic. It is as rob says common to have reflections, I've seen rgb images with three different colored halos around this very star due to reflections from the filter surface http://www.iceinspace.com.au/forum/a...se.php?a=83606
I only put this up to show how easy it is to get them and it's also a very similar composition as yours.

Again don't panic about it 99% of the time you will get nothing.

Thanks again for the reassurance and advice Clive I'm really not concerned about it now that I know it wasn't really my fault and as you say won't be an issue 99% of the time. It's the first time I have ever come up against a really bright star, so I thought I would pose the question. Prior to this I think the brightest star I have come up against in the field of view is the one next to the Orion Nebula http://www.iceinspace.com.au/forum/s...ad.php?t=80105 . The Pleiades is next on my wish list to image. Can't wait.

Originally Posted by ZeroID

That is one awesome image despite the wee reflection. The brilliance and diffraction spikes of Alnitak and the sharpness and colours of the whole shot are just amazing. That one would go up on the wall. Clone out the wee ring if you have to but take credit for a stunningly sharp and beautiful shot. I just love those crepuscular rays coming away from Alnitak
Well done.

Thank you so much for that lovely feedback Brent. I'm glad you like it. Don't get me wrong, I love how this turned out and I am very proud of it. Will certainly be gracing my wall soon. I was more curious as to weather it was an optical train issue or weather a lapse in my setup had caused it.

[RobF (Rob)]

The MPCC is pretty hard value to beat Greg. I think for 99% of objects you'll be a lot worse off without it, even if you do get the odd reflection from it. Once you step up from the Baader I'm pretty sure you start looking at much more expensive options with wider optical surfaces. Having said that I think there might be an Orion option now - I'd have to go digging for info.

This whole game tends to become an issue of getting cost effective pieces of the puzzle that work together. There's always something more expensive to lust after, but it's surprising how many other parts of your established imaging train can need upgrading as you fiddle

I'd be hanging that in the pool room BTW!

[CapturingTheNight (Greg)]

Originally Posted by RobF

The MPCC is pretty hard value to beat Greg. I think for 99% of objects you'll be a lot worse off without it, even if you do get the odd reflection from it. Once you step up from the Baader I'm pretty sure you start looking at much more expensive options with wider optical surfaces. Having said that I think there might be an Orion option now - I'd have to go digging for info.

This whole game tends to become an issue of getting cost effective pieces of the puzzle that work together. There's always something more expensive to lust after, but it's surprising how many other parts of your established imaging train can need upgrading as you fiddle

I'd be hanging that in the pool room BTW!

Thank you once again for your thoughts and feedback Rob There are plenty of things I am already lusting after *drool* but I think i'll stick with my current setup for a while. I'm planning to get a few things printed next weekend and yes this will certainly be one of them and if I had a pool room it would be there. Thanks again.

[A23649 (Nathan)]

it's the reflection off the coma corrector onto the secondary, trust me with this one.

[CapturingTheNight (Greg)]

Originally Posted by A23649

it's the reflection off the coma corrector onto the secondary, trust me with this one.

Thank you very much for that Nathan If it becomes to much of an issue i'll certainly be going to the MPCC first, but if it is as the others say and it wont be a problem for 99% of the objects I image, then I'm pretty happy at this stage to leave it as it is.