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Questar M13 image

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#1 mtr1

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Posted 15 June 2019 - 06:41 PM

I imaged M13 last night using a mono cam on my Q3.5.  It was my first guided Questar image in a while; it's more cumbersome than guiding with a go-to mount but it certainly works.  I started late and didn't really collect enough data to make this a great image but it's not terrible either.  

 

M13v2wmsm.jpg

 

Higher res and tech details here https://www.flickr.c.../in/dateposted/

 

Regards,

Mauri 


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#2 Astroman007

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Posted 15 June 2019 - 08:48 PM

I like it very much. smile.gif



#3 rolo

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Posted 15 June 2019 - 08:51 PM

Not bad!waytogo.gif



#4 rcwolpert

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Posted 15 June 2019 - 08:59 PM

Very nice!



#5 rcwolpert

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Posted 15 June 2019 - 09:01 PM

What camera, etc did you use?



#6 mtr1

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Posted 16 June 2019 - 01:39 AM

Thanks for the kind words, all!

 

Tech Stuff:  Questar 3.5" telescope at native 1400mm focal length (f/16)/QHY 163 mono/guided/8 second exposures captured in SharpCap live stacks/ L 14 min; R 14 min; G 7 min/G used in both green and blue channels/Processed with PixInsight and GIMP.  L, R, G, and B 1.25" filters are in a ZWO manual filter wheel and the camera/filter wheel is mounted in the EP port so that I can reach high declination targets (mounting the camera in the axial port improves quality but blocks the scope from imaging near the zenith).  Captured from my yard in Westchester County, NY.

 

I usually recommend that people try imaging with a color camera because the improvement in image quality that can be achieved with mono imaging comes at the expense of greater capture and processing complexity.  Indeed, in this case the target dropped into the trees before I could capture any data with the blue filter, so the colors here may be a bit off from a fully successful imaging session.

 

Guiding, btw, was handled the same way as my Questar deep sky imaging since 2015 -- SBIG sti guider mounted on a JMI Questar piggyback mount; using the Questar PowerGuide 2 and dec drive with a hacked hand controller, via PHD2.  Note that the PG3 controller has a port so no hacking is required; and the PG3 declination drive  performs better than the PG2 version.  But I switched back to PG2 for general use. A couple of years ago I also found that I got more consistent performance by using the ZWO USB to ST4 Adapter instead of a direct connection from the guide camera to the PG hand controller.  Guiding is pretty important if you're going to try imaging with the Q.  In my case, during the summer my view of Polaris is blocked by trees so I use guiding to perform a drift alignment.  I also thought that I'd be shooting 15 second exposures but my guiding was a little jumpy and stars were smearing a bit, so i dropped to 8 seconds, collecting these exposures in 7 minute stacks.  As you can see in the image, my stars were pretty good; I used some sharpening utilities in PI but did not need a morphological adjustment to round up the stars.  As mentioned in the discussion on Nicolas's fabulous M51 image, the short exposure techniques with CMOS cameras make it possible to image with the Q at native focal length.  When I started imaging with CCD cameras, incorporating a focal reducer made a big difference for image capture but also produced significant coma beyond the center of the image. 

 

SharpCap also allows for dark and flat capture and subtraction on the fly, but I hadn't set this up before starting imaging last night.  I did capture darks and flats after collecting the data and then manually subtracted them from the livestacks during processing with PI.   I think it's fair to say that achieving decent looking images from the Questar does require an intermediate/advanced level of processing skill and I couldn't do this without PixInsight. 

 

Probably more than you were looking for but I hope this is helpful!

 

Regards,

Mauri


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#7 Matt Looby

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Posted 16 June 2019 - 01:07 PM

Nice work!



#8 mtr1

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Posted 24 June 2019 - 09:01 PM

.... And here's the completed image.  Like Nicolas's fine M51 the extra hours of data (now 3 hours vs original 35 minutes) makes a big difference. 

M13lrgbv3wmsm2.jpg

 

Full resolution and details here https://www.flickr.c...in/photostream/

 

Regards,

Mauri


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