Skywatcher Esprit 100 star-shape

[lrt75914]

Hi everyone,

After months of bad weather I finally had the opportunity to give my new Skywatcher Esprit 100, which I bought last summer, a try. I was able to take a couple of pictures of NGC2023 and NGC2244 and I am quite happy that I was finally able to use my telescope for anything other than collecting dust. However, the shape of the stars in my test images look a bit weird to me. Maybe it's because I'm used to images from my newtonian telescope, but the brighter stars from my Esprit 100 look a bit bloated to me.

 

 

I used the following setup:

• Skywatcher Esprit 100
• Skywatcher AZ-EQ 6
• Borg Collective 50mm Guide Scope
• ZWO ASI 1600 MM Cool
• ZWO ASI 174 (Guide camera)
• Microtouch Focuser
• EKOS running on a Raspberry Pi 3

 

Both images are 600s Luminance subs with the Gain set to 200 and Gamma to 21. Hopefully you guys can give me any feedback on weather these images are acceptable or not.

Best,

Patrick

 

 

[Filroden]

Hi Patrick

First, congratulations on getting the clear night to test the scope

I suspect it's the combination of the higher gain plus long exposure times. The ZWO1600 does not have deep wells and will quickly saturate. I'd normally only push 600s subs for narrowband. At unity gain I'm still saturating the bright stars at 120s. So going 5 times longer is likely saturating their halos leading to the bloated shapes.

I'd give shorter subs a test. Your histogram is quite over to the right. Jon Rista has done a lot of testing with this camera and you don't need to get your histogram too far off the left to deliver similar results by integrating more shorter subs than less longer subs. 

Alternatively, try dropping the gain so you can recover a little dynamic range. Unity at highest (139?) but try 75 too.

It my require a combination of both.