City DSLR astrophotography-25hrs on NGC5139

[Phisci (Ryan)]

1500 x 1 min subs at ISO 100 using Samsung DSLR on 80mm refractors at F7.5 or thereabouts. Johannesburg white/red zone; Stacked and processed in Pixinsight;

Running 4 80mm is parallel so equiv aperture is 80*Sqrt(4) and equiv focal ratio is F7/Sqrt(4) (160mm at F1.9).

[Atmos (Colin)]

Nice stars and nice resolution, only so much that you can get with a 80mm + DSLR.
Looks like you have some nasty gradients imaging from your heavily light polluted suburban backyard

What you can do is use the PhotometricColorCorrection utility and set it to G2V star colour and it may help with the blue bias. It is a very red star cluster but it is looking pretty good so far.

[Phisci (Ryan)]

Thanks Atmos, here is the result of the photometric calibration using the average galaxy option

[Imme (Jon)]

Interested to see the imaging rig....can you post a picture?

[Lognic04 (Logan)]

I don't think 25 hours would help a cluster... But nice image anyway

[Phisci (Ryan)]

Thanks for the comments; Agree 25 hours on clusters is overkill but have seen in the past that imaging from the city requires about 25x more time than imaging at a dark site about 120km outside joburg, hence the decision to try and see what the outcome would be.

I've attached some pics of the setup.

[Imme (Jon)]

Originally Posted by Phisci

I've attached some pics of the setup.

....just wow

[Atmos (Colin)]

Impressive looking setup

[cometcatcher (Kevin)]

Strewth!

Nice image. 1500 frames.... I think I know someone else that does that...

[Phisci (Ryan)]

I setup the QUAD scopes because achieving a similar signal:noise ratio in the city vs a darksite required a 25 fold increase in number of images.

So saves on acquisition time by a factor of 4 but then stretches processing time by a factor of about 5.

In total I estimate it takes me 5x longer to capture and process images from the city than from the dark site (assuming a 3:1 process vs acquisition time ratio). But for the city using 4 scopes reduces total time by about 25% vs 1 scope.

The refractors are all entry level doublets (Skywatcher 80mm and William optics) and post Samsung's withdrawal from the DSLR market their nx500 model went very cheaply for a while.