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 Post subject: Re: Astrophotography...
PostPosted: Tue, 08-05-18, 19:08 GMT 
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Understood. And yes, the better mount has priority ;)


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 Post subject: Re: Astrophotography...
PostPosted: Sun, 13-05-18, 9:55 GMT 
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Consider the barred spiral galaxy pair NGC 3788 and NGC 3786 (Hubble type SBa) that is interacting gravitationally. Here is a photo of this pair from the SDSS survey:
Attachment:
n3788_n3786_SDSS.jpg
n3788_n3786_SDSS.jpg [ 33.8 KiB | Viewed 1405 times ]


In celestia.Sci these colliding galaxies render pretty well...
[click on imsge by all means]
Attachment:
Screenshot_20180513_115158.png
Screenshot_20180513_115158.png [ 331.87 KiB | Viewed 1406 times ]


Probably they are too small for your scope/camera, Stephen?

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Fridger

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 Post subject: Re: Astrophotography...
PostPosted: Sun, 13-05-18, 14:00 GMT 
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t00fri wrote:
Probably they are too small for your scope/camera, Stephen?


Too faint and quasi-stellar, in my opinion. As interacting pair to shot, I would suggest NGC 4656/57 (Hockey Stick galaxy) in Canes Venatici; the field maybe might cover also the nearby and former interacting NGC 4631 (Whale galaxy). The issues with subs should be the same like in the Needle galaxy, though. This shot should be very similar to that.

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 Post subject: Re: Astrophotography...
PostPosted: Mon, 14-05-18, 13:49 GMT 
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t00fri wrote:
Probably they are too small for your scope/camera, Stephen?


Yes, I'm afraid these are too small to capture any details.

fenerit wrote:
As interacting pair to shot, I would suggest NGC 4656/57 (Hockey Stick galaxy) in Canes Venatici; the field maybe might cover also the nearby and former interacting NGC 4631 (Whale galaxy).


Hockey Stick and Whale galaxy are definitely on my todo list. They should fit on one image, if I remember correctly. Still, I'm hesitating to try them with my old mount, as an upgrade to an EQ6 is becoming more and more tangible :-).

Steffen


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 Post subject: Re: Astrophotography...
PostPosted: Mon, 14-05-18, 20:04 GMT 
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Here is another classical configuration: M 81 and M 82:

Hubble Space Telescope photo:
=======================
Attachment:
Screenshot_20180514_215620.png
Screenshot_20180514_215620.png [ 847.1 KiB | Viewed 1359 times ]

Wow!

Now we are curious about what celestia.Sci can show:

celestia.Sci:
========
[click on the image by all means]
Attachment:
Screenshot_20180514_214543.png
Screenshot_20180514_214543.png [ 259.09 KiB | Viewed 1359 times ]


What I find remarkable apart from the correct spacial orientations and the proper opposite winding senses, is that the colors of both galaxies do match pretty well! This is not accidental, of course. The computer calculates the global galaxy color from the catalogued B-V color index: B-V near 1.0 gives the orange-brown color as in M 81, while B-V ~ 0.3 <<1 gives a mostly bluish appearance like in M 82...

Whenever I show an equatorial grid, North is towards the top.

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Fridger

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 Post subject: Re: Astrophotography...
PostPosted: Tue, 15-05-18, 7:50 GMT 
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Indeed, it's amazing how accurate the renderings from catalog data can be!

While the Hubble images are in their own league, at least the colors in my own shot are not totally off, I think :-)

Grüße,
Steffen


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 Post subject: Re: Astrophotography...
PostPosted: Tue, 15-05-18, 8:06 GMT 
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schreiberste wrote:
Indeed, it's amazing how accurate the renderings from catalog data can be!

While the Hubble images are in their own league, at least the colors in my own shot are not totally off, I think :-)

Grüße,
Steffen


Indeed, Steffen, I had forgotten about this great shot of yours earlier on. The color rendering is surprisingly good, I think. The displayed photos of galaxies, globulars etc. often show dramatically different colors. This is mostly due to the fact that in these cases "raw" color profiles are used that are very far from the standardized ones used in color-management (sRGB,...).

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 Post subject: Re: Astrophotography...
PostPosted: Wed, 16-05-18, 21:12 GMT 
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Steffen, here comes your mount ;-)
The scope is a good old 10 inch Orion

https://youtu.be/Wvb6wkqLTAM

enjoy, Fridger

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 Post subject: Re: Astrophotography...
PostPosted: Thu, 17-05-18, 11:07 GMT 
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t00fri wrote:
Steffen, here comes your mount ;-)
The scope is a good old 10 inch Orion

https://youtu.be/Wvb6wkqLTAM

Looks like an EQ6, although his link refers to an EQ6-R.
Well, I wouldn't mind getting any of the two ;-)


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 Post subject: Re: Astrophotography...
PostPosted: Thu, 17-05-18, 12:43 GMT 
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The prices he quoted over at the YouTube site were

~ $1280 for the mount (free shipping, Amazon)
~ $ 770 for the 10 inch scope (f:4 => Coma, no eyepieces included, Amazon)

My Celestron 8" (f:10) was far more expensive a long time ago. Being a physicist, I could not resist at the time to measure the shape of the 8" Schmidt corrector by means of laser interferometry. The shape was confirmed to be pretty bad, and after some tiring argumentation they gave me a brand new C8 after 10 years of use! The deal was that I never complain again :° The spherical aberration was better corrected but Coma was worse... :mrgreen:

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 Post subject: Re: Astrophotography...
PostPosted: Thu, 17-05-18, 21:49 GMT 
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Celestron SCTs corrected for coma are the EdgeHD serie. You C8 OTA in this serie is 1.745,00 €

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 Post subject: Re: Astrophotography...
PostPosted: Fri, 18-05-18, 6:53 GMT 
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fenerit wrote:
Celestron SCTs corrected for coma are the EdgeHD serie. You C8 OTA in this serie is 1.745,00 €


If I correctly remember, the "Coma corrector" used to be a simple Achromat (doublet) near the focal plane. While it was said to reduce the Coma somewhat, it tends to introduce pretty bad color seams, since near the focal plane the rays approach under a pretty big angle. Achromats can eliminate color in such cases only poorly.

Your quoted price sounds amazingly low. Celestron have apparently increased mass production substantially in the past...

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 Post subject: Re: Astrophotography...
PostPosted: Fri, 18-05-18, 10:25 GMT 
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t00fri wrote:
If I correctly remember, the "Coma corrector" used to be a simple Achromat (doublet) near the focal plane. While it was said to reduce the Coma somewhat, it tends to introduce pretty bad color seams, since near the focal plane the rays approach under a pretty big angle. Achromats can eliminate color in such cases only poorly.


The internal SCT design is that. The difference is the use of ED glass for the internal coma corrector (Extralow Dispersion, HD in Celestron's fashion). This variety of exotic glasses is used for the apochromatic refractors, either for visual or astrophotography. This glass in doublets - or better in triplets and up - virtually eliminate the chromatic aberration.

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 Post subject: Re: Astrophotography...
PostPosted: Fri, 18-05-18, 15:36 GMT 
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fenerit wrote:
t00fri wrote:
If I correctly remember, the "Coma corrector" used to be a simple Achromat (doublet) near the focal plane. While it was said to reduce the Coma somewhat, it tends to introduce pretty bad color seams, since near the focal plane the rays approach under a pretty big angle. Achromats can eliminate color in such cases only poorly.


The internal SCT design is that. The difference is the use of ED glass for the internal coma corrector (Extralow Dispersion, HD in Celestron's fashion). This variety of exotic glasses is used for the apochromatic refractors, either for visual or astrophotography. This glass in doublets - or better in triplets and up - virtually eliminate the chromatic aberration.


Makes sense, but when I bought my C8 these more fancy options were not offered yet.

Fridger

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 Post subject: Re: Astrophotography...
PostPosted: Tue, 31-07-18, 13:25 GMT 
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The total lunar eclipse from last Friday in Germany.
This is a stack of 50 images, a small part of a sequence that I actually captured to create a small time-lapse video.


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File comment: Total Lunar Eclipse, July 2018
Mondfinsternis_2018-07_4k.jpg
Mondfinsternis_2018-07_4k.jpg [ 1.12 MiB | Viewed 623 times ]
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