Aligning images

[Jeffkop (Jeff)]

Hi again to everyone.

I recently posted a couple of images M17 & M5 to be specific and it was unanimously agreed they needed more data. I have also understood this imaging process to be a long term thing where one gathers new data to be added to images every year perhaps as the celestial objects present themselves in your part of the sky. It wasnt until I tried to reimage M17 on a subsequent night that the complexity of this process was revealed.

I can get the camera very close to the SAME position it was when I took the first lot of images but NOT exact and so, when I try to align the new data with the old data ... well I cant successfully can I. The alignment process will only try and move the pic in UP/DOWN, RIGHT/LEFT when infact they need to be rotated a little to do the job.

So either everybody leaves the camera in the same position and never remove it from the scope OR is their software available that can rotate images to align them??

Otherwise how do you all take images year after year and add them together??

I'm hoping there is an easy answer to this.

Thanks for looking

Jeff

[iceman (Mike)]

Hi jeff

When people talk about adding more data, typically they'd just be referring to more subs (sub-exposures) on the one night. That is, instead of 3x5 minute exposures (for example), do 10x5 minute exposures.

Generally i'd say an hour of exposures minimum for a good signal to noise ratio on a deep space object.

There are people that do add data like you're describing - for example, going out the next weekend and grabbing another hours worth of data and adding it to the previous weekend. It would be unusual though for someone to add to data captured a year ago.

When adding data from multiple sessions, definitely the camera orientation is important, as is the focal length, sky conditions etc.
People with permanent setups (and camera permanently attached) have a huge advantage in this.

Otherwise, you can use a program like registar to align your images - it will take rotation into account and deal with it. Deep Sky Stacker (DSS) will also do it fairly well.

Hope that helps.

[Jeffkop (Jeff)]

Originally Posted by iceman

Hi jeff

Otherwise, you can use a program like registar to align your images - it will take rotation into account and deal with it. Deep Sky Stacker (DSS) will also do it fairly well.

Hope that helps.

Thanks for the information Mike, I was way off wasnt I. I thought for sure that most people would have non permanent setups and so have to remove their camera ets to do a drift align at the beginning of each session like I have to. Oh well, you definately learn something new in this game all the time. I will go look up registar now.

Thanks again

Jeff

[Geoff45 (Geoff)]

Registar is definitely the best software for combining images. It is a must for making mosaics. You can combine images taken in different orientations or taken with different focal lengths. It will correct field distortion that may be introduced when trying to combine images taken with different scopes or using barlows, field flatteners etc