Re: unequal brightness in image
Posted: Sun Jun 21, 2020 11:34 pm
Joe,
I grew up in Hillsdale, NJ which isn't too far from you. The NYC light dome wasn't too bad in the 1970's but I could definitely see it to the south-east. I have no I idea how bad it is today.
Looking at sky charts I see that the Veil Nebula is directly east and 55 degrees above the horizon at 1am tonight. The NYC light dome should be off to the right. It is a factor but how much I can't say. The other thing you need to worry about is what lies directly across the river: Hastings, Ardsley, Elmsford, Yonkers, White Plains. So looking east is problematic for you, unfortunately. Looking west should be better, correct? Hopefully there are no trees blocking your view.
One thing you can do to minimize light domes in your images is to wait for the target to move higher in the sky. Unfortunately 1am is already late. You could wait until 2am to begin imaging. That would give you a solid 1 hour worth of data before hitting the meridian. Question: with your mount can you image through the meridian? With my scope I have to do what is called a "meridian flip".
There is another possibility, and that is to choose a different target, something like M57, the Ring Nebula. It is small but bright and colorful. It rises two hours before the Veil Nebula so you can retire earlier. If you begin imaging at say 11:45pm then you can get in a solid 1 hour. It will be high in the sky so light domes will be at a minimum.
Joe, I just re-read your earlier post. 30 degrees above the horizon is too low. You definitely need to wait for it to get to a minimum of 45 degrees. That, I think, will be your secret to success. I can't guarantee that it will completely eliminate light domes but they should be significantly less of a problem. Of course you have the option of imaging towards the west. Hopefully no trees there.
BTW, I have Bortle 5 skies. I refuse to go below 30 degrees. The atmosphere is just too thick and full of LP. I prefer to start at 40 degrees. In your case I think you should wait for at least 50 degrees.
Good luck!
Brian
I grew up in Hillsdale, NJ which isn't too far from you. The NYC light dome wasn't too bad in the 1970's but I could definitely see it to the south-east. I have no I idea how bad it is today.
Looking at sky charts I see that the Veil Nebula is directly east and 55 degrees above the horizon at 1am tonight. The NYC light dome should be off to the right. It is a factor but how much I can't say. The other thing you need to worry about is what lies directly across the river: Hastings, Ardsley, Elmsford, Yonkers, White Plains. So looking east is problematic for you, unfortunately. Looking west should be better, correct? Hopefully there are no trees blocking your view.
One thing you can do to minimize light domes in your images is to wait for the target to move higher in the sky. Unfortunately 1am is already late. You could wait until 2am to begin imaging. That would give you a solid 1 hour worth of data before hitting the meridian. Question: with your mount can you image through the meridian? With my scope I have to do what is called a "meridian flip".
There is another possibility, and that is to choose a different target, something like M57, the Ring Nebula. It is small but bright and colorful. It rises two hours before the Veil Nebula so you can retire earlier. If you begin imaging at say 11:45pm then you can get in a solid 1 hour. It will be high in the sky so light domes will be at a minimum.
Joe, I just re-read your earlier post. 30 degrees above the horizon is too low. You definitely need to wait for it to get to a minimum of 45 degrees. That, I think, will be your secret to success. I can't guarantee that it will completely eliminate light domes but they should be significantly less of a problem. Of course you have the option of imaging towards the west. Hopefully no trees there.
BTW, I have Bortle 5 skies. I refuse to go below 30 degrees. The atmosphere is just too thick and full of LP. I prefer to start at 40 degrees. In your case I think you should wait for at least 50 degrees.
Good luck!
Brian