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 Post subject: Re: Astrophotography...
PostPosted: Sat, 24-02-18, 10:32 GMT 
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t00fri wrote:
this is a pretty good one! Incidentally, did you ever find some time to examine your mirror via a Ronchi grid or perhaps simpler: "mit der Foucault'schen Messerschneiden-Methode" ? From your shots I'd say the mirror must be very good, indeed!

Over the years, I did quite a few Moon shots with my C8, having an effective focal length of 2.0m. Yet I don't think the result was any better than yours. This is mainly due to the much more delicate requests for grinding and alignment accuracy of such catadioptric folded systems. Also --compared to simple parabolic mirrors--Coma becomes even more serious at somewhat larger angles...


Thank you. No I didn't do any measurements with my mirror - I couldn't do anything with these numbers anyway, as I wouldn't know what to improve based on them.
So it looks like I was very lucky with the telescope after all - if only I had a better mount to drive it.
But I think that apart from the optical quality, very much depends on the postprocessing as well. I aligned the source images using PIPP and then stacked and sharpened (wavelet-sharpening) using RegiStax. This helps with getting the optimum detail and compensates for errors caused by atmospheric turbulences.

fenerit wrote:
That's an experienced amateur shot. You did catch the "Werner X" feature!

Thanks!
As much as I would love to tell you that this was on purpose, the "Werner X" was purely accidental, and I didn't even know this feature until now. Seems like I was lucky again. :D


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 Post subject: Re: Astrophotography...
PostPosted: Mon, 26-02-18, 8:17 GMT 
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This is what I was actually trying to capture: a slightly improved version of the Leo Triplet.
I had to wait quite some time for the moon to set, but still the sky was brighter than I would have liked it to be. I took about 700 pictures over two nights, 9 hours of observation time in total. From those I kept just the best and finally got an integrated exposure time of just under an hour (111 x 30sec), definitely not enough for these faint objects. But still, the result is a bit better then my last attempt, I think, and about as much as I can get with my equipment under city- and moon light.


Attachments:
Leo-Triplet_2018-02_(111x30s-Iso800-calibrated).jpg
Leo-Triplet_2018-02_(111x30s-Iso800-calibrated).jpg [ 896.24 KiB | Viewed 1446 times ]
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 Post subject: Re: Astrophotography...
PostPosted: Mon, 26-02-18, 12:11 GMT 
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Amazing what you can get with your "mini" reflector by means of the stacking technique!
What kind of software are you actually using for this procedure? Is it openSource?

Fridger

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 Post subject: Re: Astrophotography...
PostPosted: Mon, 26-02-18, 12:39 GMT 
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t00fri wrote:
Amazing what you can get with your "mini" reflector by means of the stacking technique!
What kind of software are you actually using for this procedure? Is it openSource?

Thanks!
First, I calibrate my source images with Flat and Bias frames. Then they are registered (aligned) and stacked. The stacked result image is then further processed with background extraction (to remove gradients caused by light pollution) and color calibrated. All of these steps are done in Siril, which is a great open-source tool and easy to use with good tutorials and documentation.
The result image is an extremely dark raw (16 bit per channel) image, which I'm further processing in darktable. Usually, I heavily stretch the histogram using base-curve and tone-curve tools, increase color saturation a lot and maybe add some local contrast. Sometimes I also have to correct for some vignetting that was not completely fixed by calibrating the light frames with Flat images.

Steffen


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 Post subject: Re: Astrophotography...
PostPosted: Mon, 26-02-18, 12:59 GMT 
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Oh thanks, Steffen,

these two applications look well done and are certainly most useful ..and open-source!
Amazingly, I never heard of them before.

Fridger

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 Post subject: Re: Astrophotography...
PostPosted: Tue, 06-03-18, 12:18 GMT 
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M42, the Great Orion Nebula.

I didn't have much luck with imaging M42 this winter because of the bad weather. I only have a couple of images from a night with bright moon and far from ideal seeing conditions. But I decided to try combining these with some older images taken with my old camera in 2016 and 2017, also not under particularly clear skies.

Well M42 is very popular among beginners in AP, and I've seen a lot of better images than this - but also a lot of worse. So why not show it anyway? :D

Steffen


Attachments:
File comment: M42 Orion Nebula, 32+45+38 images of 30s each from 2016, 2017 and 2018
M42_Orion-Nebel-2018-02_(30s_32x2016_45x2017_38x2018).jpg
M42_Orion-Nebel-2018-02_(30s_32x2016_45x2017_38x2018).jpg [ 575 KiB | Viewed 1368 times ]
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 Post subject: Re: Astrophotography...
PostPosted: Tue, 06-03-18, 14:03 GMT 
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schreiberste wrote:
M42, the Great Orion Nebula.

Well M42 is very popular among beginners in AP, and I've seen a lot of better images than this - but also a lot of worse. So why not show it anyway? :D

Steffen


While being a standard target in astro-photography, M 42 is VERY hard to model in computer simulations (celestia.Sci). Since numerous years I am thinking about possible approaches that would be able to render whole catalogs with nebulae by computer (without human action!)

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Fridger

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 Post subject: Re: Astrophotography...
PostPosted: Sun, 25-03-18, 20:01 GMT 
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No amazing shots like schreiberste's ones this time; just two of a technical kind.

Attachment:
reg._03.27.46.jpg
reg._03.27.46.jpg [ 343.01 KiB | Viewed 1163 times ]

A screenshot of one of the monitors while autoguiding. The autoguider camera shows the star [s]BL Cam[/s]* Spica seen through the spectrometer's slit. Below there is the tracking error windows, range +/- 1 arcsecond. In this configuration the deviations/corrections looks messy because the slit does interfere with the "steady state" and the star's surface brightness required for this operation. The third panel is the camera control/options

Attachment:
Image-1.jpg
Image-1.jpg [ 129.43 KiB | Viewed 1163 times ]

This is a remote infrared shot of the environmental watching camera. The camera is a bit close to that scope, but it must check out also elsewhere by remote pan-scanning.

EDIT LATER:
* I know they were sampling BL Cam when ask for the screenshots... :|

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 Post subject: Re: Astrophotography...
PostPosted: Mon, 26-03-18, 11:06 GMT 
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Although I have to admit that I don't understand all of the above, I'm still amazed at the effort, high-tech and certainly money you guys are throwing at that topic ;)
I can only dream of tracking errors in fractions of an arcsecond.
And - speaking of high-tech tools - I recently shortened my drawtube using a hack saw :D.

What exactly is the "environmental watching camera" watching?


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 Post subject: Re: Astrophotography...
PostPosted: Mon, 26-03-18, 13:42 GMT 
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My latest image: M81 and M82.
Again, this image would need much more integrated light to become something good. Heavy stretching of the histogram and saturation was needed to get anything visible at all, and this shows in the amount of noise (and also color noise).

Steffen


Attachments:
File comment: The M81 / M82 couple, stack of 160 subs, 30s each
M81-M82_Bodes-Galaxie_2018-03_(driz_160x30s).jpg
M81-M82_Bodes-Galaxie_2018-03_(driz_160x30s).jpg [ 921.75 KiB | Viewed 1143 times ]
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 Post subject: Re: Astrophotography...
PostPosted: Mon, 26-03-18, 14:02 GMT 
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We are an association active from the middle of Seventies, all this was made step by step by us and with a little help from the municipality. Money indeed are the primary concerns, expecially after 2008, when the municipality stops founds for all the town's associations. As last step we are remoteizing the imaging-spectrograph-photometry section - a roof on roll area - in order to be used by other clubs or education institutes, and the camera is for checking out both the instruments and intruders when nobody authorized is there.

P.S.
That's is good too. You have catched the exended HII regions of M82 at glance, and this is a success. Those HII regions makes M82 visible also through a narrowband UHC filter, which for galaxies generally is unfitted. For example, through this filter M81 and near all the galaxies disappears completely from the eyepiece.

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 Post subject: Re: Astrophotography...
PostPosted: Mon, 09-04-18, 7:42 GMT 
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Photographed during two nights (April 6-7) with more than 1000 images of 30 seconds exposure time each. I stacked the best 173 of these to get the source image, which was then post-processed.
Best watched in full-screen to also see the faint and small other galaxies that can be found in this widefield (IC 4263, NGC 5169, NGC 5198, NGC 5173,...)


Attachments:
File comment: Whirlpool Galaxy (M51)
M51-Whirlpool_2018-04_(173x30s-drizzle-crop-hist-bgx-cc)_dt.jpg
M51-Whirlpool_2018-04_(173x30s-drizzle-crop-hist-bgx-cc)_dt.jpg [ 1.99 MiB | Viewed 916 times ]
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 Post subject: Re: Astrophotography...
PostPosted: Mon, 09-04-18, 10:40 GMT 
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Aha Steffen, you are presumably profiting from the nice April weather (including even Hamburg ;-)).
This is how the computer composes the Whirlpool galaxy (M 51) without human interference:

/home/t00fri/Screenshot_20180409_123945.jpg

cheers,
Fridger


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Screenshot_20180409_123945.jpg
Screenshot_20180409_123945.jpg [ 66.25 KiB | Viewed 913 times ]

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 Post subject: Re: Astrophotography...
PostPosted: Mon, 09-04-18, 11:11 GMT 
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t00fri wrote:
Aha Steffen, you are presumably profiting from the nice April weather (including even Hamburg ;-)).

Yes! Good weather with clear skies and weekend is a perfect combination!

t00fri wrote:
This is how the computer composes the Whirlpool galaxy (M 51) without human interference:

This looks fantastic and really close to reality!


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 Post subject: Re: Astrophotography...
PostPosted: Mon, 09-04-18, 19:49 GMT 
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That pair is incredible. Visually, when the seeing is good but the sky's transparency goes and went, they seem alive; M51/B seem to attract the interacting spiral arm like if were a black hole. I would suggest also a shot to the nearby galaxy NGC 4631 (Whale galaxy) still in Canes Venatici and NGC 4565 (Needle galaxy) in Coma, they are good subjects for your equipment. A good 2x Barlow linse maybe could be your next acquisition, inserted between the coma corrector and the camera it does extend the focal lenght of the scope and you will go closer. Do not choose multipliers >2x, those could be too much for your mount.

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