M13 with different scaling/exposures - Starlight Live

[Robrj]

I did some experimentation with exposures on M13.  This was with an Orion ED80T-CF/AVX with the Ultrastar-C in Starlight Live.  I wouldn't typically use the X^0.25 non-linear scaling model on globs but decided to give it a shot and it worked great.

Typically, I'd do a shorter exposure.  Here's a 15x15s exposure (Linear).  The glob looks small, which in the past I just attributed to a smaller field of view.  I could brighten the image a bit but the core is easily blown out with linear.

Full size image:  http://www.astrobin.com/full/293934/0/

 

This time, I tried a longer exposure to bring out some of the fainter stars and get a bigger ball shape but it really blows out the inner stars.  However, with the X^0.25 setting instead of linear, I got a nice core and the fainter ones showed up giving a much more impressive image:

10x45s (X^0.25)

Full size image:  http://www.astrobin.com/full/293935/0/

My darks were set to 45s so a 15s exposure on X^0.25 didn't look very good.  Next time out, I'll try 15s at X^0.25 to compare it to the 15s linear shot directly.  See the section near figure 10a of Don's Lodestar Live manual for info on the non-linear scaling models.

[roelb]

Interesting Rob.

Did a post process of an earlier taken image of M 13, to see what ARCSINH can achieve with a globular.

LINEAR

 ARCSINH

[Martin Meredith]

Nice shots, both. Nonlinear is definitely the way to go for globulars. I tend to use nonlin for everything, although perversely I've found dark nebula sometimes respond best to linear...

Martin

[Robrj]

What is the best type of object for Arcsinh?   I've tried it on a few and seem to get better results with either Linear or X^0.25.

[roelb]

I use arcsinh for galaxies with a bright cores.