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M3 core region at 1" resolution

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#1 Jan_Fremerey

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Posted 15 May 2020 - 05:20 AM

DSO_233823_lapl4_ap45_P75_lumi_itGr154x4_11K9-65K5_g201_mit RGB_01_15-255_800sq.jpg

 

Taken last night with 10" f/5 prime focus camera ZWO ASI178MM. L: 75% from 2,000x500ms - RGB: 75% from 500x1s each.

 

CS, Jan

 

 


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#2 happylimpet

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Posted 15 May 2020 - 06:39 AM

Autostakkert, some sharpening? WHat did you use? Looks like when I use iterative gaussian sharpening in FITSWORK.

 

Amazing image! Have you measured the FWHM then?



#3 Jan_Fremerey

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Posted 15 May 2020 - 07:14 AM

Autostakkert, some sharpening? WHat did you use? Looks like when I use iterative gaussian sharpening in FITSWORK.

Have you measured the FWHM then?

Thanks a lot for kind reply! As you say: AutoStakkert!3 without sharpening, but iterative gaussian in Fitswork at radius 1.54, x4, s150, further data documented in file name. FWHM less than 3 px, i.e. 7.2 µm / 1.27 m = 1.2 arcsec



#4 happylimpet

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Posted 15 May 2020 - 07:24 AM

Thanks a lot for kind reply! As you say: AutoStakkert!3 without sharpening, but iterative gaussian in Fitswork at radius 1.54, x4, s150, further data documented in file name. FWHM less than 3 px, i.e. 7.2 µm / 1.27 m = 1.2 arcsec

Funny that I recognised the process from the residuals! I use FITSWORK iterative gaussian a lot - it works very well, though it does leave those distinctive haloes around stars.

 

Your filenames also look like mine!

 

Thats a very impressive result - well done.



#5 Jan_Fremerey

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Posted 15 May 2020 - 08:57 AM

I use FITSWORK iterative gaussian a lot - it works very well, though it does leave those distinctive haloes around stars.

I didn't know where the haloes come from. Do you recommend another sharpening tool? In fact, I don't regard those haloes worse than spikes which astonishingly do not appear in spite of the massive camera holder (http://www.astro-vr.de/100901_3694.jpg), even on much brighter stars.



#6 sunnyday

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Posted 15 May 2020 - 09:00 AM

very pretty, it gives the impression that you go inside.
thank you .



#7 Quaternion

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Posted 15 May 2020 - 09:01 AM

Awesome.  May I ask what Gain you use relative to the max gain setting?  I made the awful mistake of trying 3sec “unlucky” DSO imaging at F5.4 with Unity Gain on an ASI1600 instead of closer to max analog gain, and basically got NO data on M81

except the central core, even with 80min...



#8 happylimpet

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Posted 15 May 2020 - 10:25 AM

I didn't know where the haloes come from. Do you recommend another sharpening tool? In fact, I don't regard those haloes worse than spikes which astonishingly do not appear in spite of the massive camera holder (http://www.astro-vr.de/100901_3694.jpg), even on much brighter stars.

No recommendations. The haloes arent a big deal - and the results are superb.

 

Is that the telescope used? Amazingly minimalist! Wow! You must be in a very dark location.



#9 Jan_Fremerey

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Posted 15 May 2020 - 11:54 AM

Is that the telescope used? Amazingly minimalist! Wow! You must be in a very dark location.

I'm working on our roof terrace under suburban skies, no problem with the open telescope as long as stray light doesn't directly enter the camera tube, i.e. from the terrace floor.
 


Edited by Jan_Fremerey, 15 May 2020 - 03:47 PM.


#10 Jan_Fremerey

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Posted 15 May 2020 - 03:35 PM

it gives the impression that you go inside.

You are right: it's like just passing through the foreground stars ...


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#11 Jan_Fremerey

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Posted 15 May 2020 - 03:41 PM

May I ask what Gain you use relative to the max gain setting?

Thanks for kind reply, I was at maximum gain setting on all channels.



#12 Jan_Fremerey

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Posted 30 October 2020 - 05:31 AM

Following a comment in another forum I investigated the current M3 image for limiting star magnitude in a first step by brightening the shadow areas:

 

M3_200514_vs_v2.gif

 

and then compared in CdC with a corresponding gaia2 map reaching down to mag-18:

 

M3_200514_vs_CdC.gif

 

It looks like the current image reaches another magnitude deeper, i.e. down to about mag-19.

 

Which maps do you recommend for lower than mag-18 ?

 

CS, Jan



#13 pejorde

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Posted 30 October 2020 - 07:01 AM

That is a mighty impressive image!

I also admire your telescope!

Years ago I built a similar, open 10" Newtonian, but using a conventional mirror. This was also mounted on a Vixen GPDX:

 

teleskop.jpg

 

This was to see if I could reach the brighter trans-neptunian objects with my 245 "Cookbook" CCD-camera. It suceeded: reaching about mag 19.8 on the faintest object, (55637) 2002 UX25: https://en.wikipedia...5637)_2002_UX25

 

I have since returned the optics to its Dobsonian base, where it now collects dust while I'm devoting the few clear evening that are to imaging, using a much smaller telescope. Still using the GPDX mount, now fitted with the Synscan EQ5 goto upgrade kit which adds autoguiding capability.

 

Regarding star map/catalogues for faint stars: I understand it that the Gaia dr2 database goes down to about mag 21?

https://sourceforge....ogs/Stars/GAIA/

 

Regards,

Per Erik


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#14 Jan_Fremerey

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Posted 30 October 2020 - 08:08 AM

Thanks, Per Erik, for your kind and instructive response, and for sharing a view on your open 10", a real eye-catcher, indeed! Congrats for having identified (55637) 2002 UX25 with the above equipment, do you remember respective exposure times ? Thanks also for linking to Gaia star catalogs. Gaia v3 release has been announced for December 2020,.

 

CS Jan


Edited by Jan_Fremerey, 30 October 2020 - 08:13 AM.


#15 pejorde

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Posted 30 October 2020 - 08:46 AM

Jan:

 

The TNO was imaged by adding 23 exposures of 240s each, unguided, for about 1.5 hours total. Still, its just a pixelated speck barely above the noise level so clearly this was just at the limit of what I could reach with that equipment. Looking though my notes I don't have an image of M3 with that telescope but I do have one of M5 (from April 17. 2005):

 

m5_s60.jpg

 

This is a single 60s exposure. Clearly, it is not comparable at all to your fantastic image! Nevertheless, it was great fun seeing what I could capture with mostly homebuildt equipment (telescope, tripod, CCD camera, and stepper motor driver for the mount).

 

Regards,

Per Erik

 

 


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#16 Jan_Fremerey

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Posted 30 October 2020 - 10:55 AM

Thanks, Per Erik, for sharing your exposure data and nice M5 capture! Image resolution obviously improves by short exposure and image stacking. In my current M3 image you will find stars at distances of 1" and closer while seeing at our suburban location is typically much larger. Homebuilding telescope components is real fun, you did a lot on that. What type of CCD chip and pixel size did you run on your 10" Newton and what is the f-ratio of your primary mirror?

 

CS Jan


Edited by Jan_Fremerey, 30 October 2020 - 10:56 AM.


#17 pejorde

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Posted 30 October 2020 - 01:04 PM

Jan:

 

The primary mirror is f/6.4 and I bought it around 1980 but did not put in into a finished telescope until a decade later. The CCD chip is a Texas Instruments TC245 with 378x242 non-square pixels (17 by 19.7 microns). It was built from parts and plans offered in the CCD Camera Cookbook: https://www.amazon.c...r/dp/0943396417

I build the camera in 2003 and was probably among the last ones to do so as it was pretty obsolete even then. I had a lot of fun with it until it died about 5 years later.

 

Your high resolution image is very inspiring, and I might try using shorter subexposures myself and see how it improves resolution. If the rain ever stops...

 

Per Erik



#18 Jan_Fremerey

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Posted 30 October 2020 - 07:52 PM

Thanks for sharing your camera chip data. So with your f/6.4 prime focus mirror and 17+ µm camera resolution you may have inserted a 5x Barlow or eye piece projection for high resolution imaging at that time?


Edited by Jan_Fremerey, 30 October 2020 - 07:53 PM.


#19 Voyager 3

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Posted 31 October 2020 - 01:34 AM

Now this is what you call a cluster-buster 😎. thanks for sharing .

#20 Jan_Fremerey

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Posted 31 October 2020 - 07:37 AM

Voyager 3: Nice and apt wording! - Thanks and CS Jan




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