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M13 RGB with QHY5III-178C and Tele Vue NP127is

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#1 james7ca

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Posted 20 May 2017 - 03:37 AM

I'm working on a RGB set for M13 and here are the initial results from the subs I collected last night. So, as I'm still collecting subs I did this preview using just one sequence from an uncooled QHY5III-178C. This is just over 60 minutes of integration (50 x 80s) at a gain of zero under my normal red/orange zone light pollution using a Tele Vue NP127is at prime focus (660mm, f/5.2). I may try to go deeper than this using my ZWO ASI178MM-Cool to collect some luminance, but that won't happen for another day or two (assuming that the skies stay clear, I have to replace the desiccant tablets in my ASI178MM because it is showing moisture on the sensor when it it cooled -- this is after about one year of use, so that could indicate the likely lifetime for those tablets).

 

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  • M13 with QHY5III-178C.jpg

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#2 gunny01

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Posted 20 May 2017 - 08:08 AM

A nice shot for that amount of integration James.  Stars don't look mushy as I've seen with other cmos based cameras. 

 

   I'll be curious to see how the ZWO does, as I've been looking at these cameras for ff guiding with an if onag and imaging. Still, hard to switch from ccd based mind set. 



#3 james7ca

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Posted 20 May 2017 - 08:19 AM

A nice shot for that amount of integration James.  Stars don't look mushy as I've seen with other cmos based cameras. 

 

   I'll be curious to see how the ZWO does, as I've been looking at these cameras for ff guiding with an if onag and imaging. Still, hard to switch from ccd based mind set. 

Thanks. You can see what the ZWO ASI178MM-Cool did with a red filter on M13, done a few weeks ago at the following link (1:1 or full resolution of 0.75 arc seconds per pixel):

 

  https://www.cloudyni...l/#entry7858373



#4 james7ca

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Posted 21 May 2017 - 09:52 AM

I managed some luminance frames with the ZWO ASI178MM-Cool and on a night with good seeing I measured a median FWHM of 1.96 arc seconds for the full stack (160 x 45s). I want to combine these with the RGB I took earlier with the uncooled QHY5III-178C (see above) so eventually I'll have an LRGB that has a few hours each of RGB (with the one-shot-color QHY) and plain luminance as shown below (with the ZWO). I also have some subs that were exposed for 10s to fill in the core detail, as at 45s the core was just slightly blown out.

 

If I'm really lucky I may even get one more clear night, but I doubt it because that would be a record for me with four nights in a row that had mostly clear skies (if you ignore the smoke from the local fires and the jet contrails that seem to be getting worse each year -- see the image in my next post, a sample of this morning's sky and it looked like this in nearly every direction).

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  • M13 with ZWO ASI178MM-Cool and Tele Vue NP127is.jpg


#5 james7ca

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Posted 21 May 2017 - 09:56 AM

And the jet contrails...

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  • Jet Contrails Just Before Sunrise.jpg


#6 james7ca

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Posted 22 May 2017 - 08:59 AM

Well, as I feared I didn't get another night of clear skies, so my all time record of three consecutive days with clear skies remains intact. We even had fog last night, so San Diego's May Gray is back.

 

In any case, I did process the 10s subs that I took the other night and that allowed me to do an HDR to recover the core of the cluster (to my taste, still bright but slightly mottled rather than the pure featureless white in the 45s integration set). I could even go to a less bright and more "resolved" core but I think globular clusters look best with kind of a "glow" toward the center.

 

 

So, here is the second version with the 10s integration to produce an HDR result. This is about a 50% reduction from the original to get under the CN posting guidelines. I'll be working on adding the RGB next.

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  • M13 with ZWO ASI178MM-Cool and Tele Vue NP127is.jpg

Edited by james7ca, 22 May 2017 - 09:07 AM.

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#7 elmiko

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Posted 17 April 2019 - 01:32 PM

Nice image James!



#8 james7ca

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Posted 17 April 2019 - 09:27 PM

Nice image James!

Thanks, it’s a fairly old offering and I really need to go back and finish the color version. However, I now have the ASI183MM camera which would give me over twice the field coverage meaning that I may want to go back and start over (since a wider field would be useful on this subject).


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#9 pyrasanth

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Posted 18 April 2019 - 05:47 PM

That's a good image. I think the stars would benefit from being slightly softer as the image looks quite harsh and you may wish to lift the background a little as it is slightly too dark for my taste. Globular clusters are a pig to process so I applaud your effort!



#10 james7ca

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Posted 19 April 2019 - 12:02 AM

That's a good image. I think the stars would benefit from being slightly softer as the image looks quite harsh and you may wish to lift the background a little as it is slightly too dark for my taste. Globular clusters are a pig to process so I applaud your effort!

Thanks for the input.

 

The color image is a little "over cooked" but the background level is around 20 units which is usually what I consider to be pretty good. The mono image is slightly darker (ranges around 16 units) so that could probably be lifted slightly, however, there are faint background stars and slight textures almost everywhere so to my eyes the average background doesn't seem too dark. These images also have to be viewed at full size with a subdued background, not just from the small preview that is embedded directly within the bright yellow background of the CN thread.

 

There might also be gamma and brightness differences between our displays and web browsers.




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