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ARP 299 / Two colliding galaxies

Posted: Fri May 22, 2020 8:17 am
by Menno555
ARP 299 / Two colliding galaxies

I was random wandering around in Ursa Major until I got a little blob. So focused on it and it looked interesting.
Turned out to be ARP 299. Two colliding galaxies 😊
Also some smaller galaxies in view: above on the right a two armed galaxy called PGC 35345 and on the left of that a galaxy called PGC 2580146. Looked that up ofcourse.
Processing was a kinda challenge: I used another method of making flats and that didn't work that well. But managed to get this capture 😊

Ioptron CEM25EC mount (no guiding)
Meade LX65 8" f/10 ACF OTA
Optec Lepus Standard 0.62x reducer
Baader Neodymium Skyglow Filter
Zwo ASI385MC camera

Captured with SharpCap: 160 x 30 sec. / Gain 240 (out of 600) / 10 darks / 100 flats / no guiding
Stacked in DeepSkyStacker
Processed in PS: Levels and Curves, color saturation, noise reduction, unsharp mask.


Re: ARP 299 / Two colliding galaxies

Posted: Sat May 23, 2020 1:25 pm
by oopfan
Very nice! Not an easy target given its size of only 2.4 x 1.9 arcmin:

Via Hubble: ... 04-24).jpg

Given your telescope and camera stats:

Effective focal length 1260mm
Pixel size: 3.75um
Resolution: 0.61 arcsec/pixel

Camera/Telescope Suitability as a function of Seeing:

Very Poor, Poor, and OK seeing: Oversampled
Good seeing: Neither Oversampled nor Undersampled
Exceptional seeing: Undersampled

How would you rate your seeing?

Personally I prefer to be Oversampled as I think you are unless you are high atop a mountain somewhere or a desert :-)

The downside to oversampling is that the photons are spread over more pixels which requires longer integration times. That plus the demands it puts on your mount's tracking.


PS: I hope you don't mind my analysis. It's just the way my brain works. Some people think I am being critical of their work but that is not my intent.

Re: ARP 299 / Two colliding galaxies

Posted: Sat May 23, 2020 1:47 pm
by oopfan
I am thrilled to see you are using an uncooled camera for AP.

Before purchasing my cooled Atik 314E CCD I was using an uncooled Altair 290M. A big problem with uncooled cameras is dark noise which can vary significantly during a session in the summertime, not so much of a problem in the winter. My images were OK but I wanted better. There was still residual noise that I could not integrate out. One way to mitigate it is to capture your darks before capturing lights. The theory is that the ambient temperature becomes cooler as the night progresses so it is better to capture darks under higher temperature conditions. That helped but an even better solution is to build a darks library that you partition by ambient temperature. That is the technique that I used here:


By the way that big fat star to the right of the nebula is a bright blue spectral class "B" star. Unfortunately my achromat refractor does a terrible job of focusing blue. It is an embarrassment.


Re: ARP 299 / Two colliding galaxies

Posted: Sat May 23, 2020 3:56 pm
by Menno555
Thanx for your analysis, don't mind at all :)
Just found out today though that I am more in the neighborhood of f/7.0. I am using the distance Optec is giving for their reducer but going to use 5mm less and see how that works.
The seeing here is a a lot. I am in the middle of a city (Bortle 8), so for me it's almost always Very Poor,, Poor, and Ok. But I don't know how it will be in the winter.
As for Over- and Undersampled: never heard of that before, so looked it up. That's how my brain works: I am oblivious of all the terms and requirements. I got my whole setup with planetary in mind, did found out that the OTA has great optics and does Deepsky also, upgraded my mount (still working Unguided, the mount just Rocks!) and just started capturing things. In a way you could say that I don't know what I am doing, I just do it and will see if it works :D
And the way of taking darks as you describe was logical to me, so I did it that way from the start.