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NA and Pelican - First light with a vintage 135mm lens

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#1 Al_N

Al_N

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Posted 01 October 2020 - 03:59 PM

NGC7000 ssmall.jpg

 

So we finally had some clear skies here on Vancouver Island. The internet tells me that the moon was~95% full when I shot this on 29 Sept. Fortunately, this target was far enough away from the moon to get reasonable contrast with the Ha filter.

 

Guiding was terrible on this object. I think my ASI290mc guide camera really struggled with the bright sky. I weeded out about a third of subs. Probably should have tossed a few more based on the oblong stars.

 

Anyway, this is first light on an old Pentax Takumar 135mm f/2.5 that I got from eBay a month or so ago. With the ASI178mm camera, this lens provides a calculated image scale of 3.65"/pixel. Despite my carping in the first couple of paragraphs I'm quite happy with this lens, and the picture. Stars on the left appear rounder than those on the right. We may have a few clear nights next week - I'll try again with darker skies and improved guiding.

 

Equipment

    Camera: ASI178mm uncooled

    Lens: Pentax 135mm f/2.5 closed two clicks to f/4

    Mount: Celestron Nexstar SE alt-az, homemade equatorial wedge

    50mm guide scope

    ASI290mc guide camera

    SVBONY 7nm H alpha filter

 

Acquisition

    24 x 300 sec light

    12 x 300 sec dark

    125 flat

    125 dark flat

 

Software/Processing

    Sharpcap for polar alignment and acquisition

    PHD2 for guiding - Dithered every frame. Due to huge backlash, guiding and dithering is in RA only.

    DSS for stacking 2x drizzle applied

    Post processing in GIMP

  •     stretch
  •     curve adjustment
  •     crop stacking artifacts
  •     layer duplicated and combined using "multiply" option, 80% opacity. **This is something I'm playing with in GIMP. It seems to greatly remove noise from dark areas, but dims the whole image and adds a bit of noise to lighter areas. Sliding the opacity slider really allow you to change the effect. I settled on 80% opacity today.**
  •     stretch
  •     Anisotropic smoothing (noise reduction)

 

Thanks for looking.

 

Al


  • F.Meiresonne, elmiko, deepwoods1 and 7 others like this

#2 mackiedlm

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Posted 03 October 2020 - 03:01 AM

That's a really nice image. I also have a few vintage lenses (Pentacon 135mm and the 200mm Takumar) and get great satisfaction out of producing Astro images with them. Keep it up!



#3 elmiko

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Posted 03 October 2020 - 08:20 AM

Nice image! 135 mm is a great fl for these larger objects! Have fun with your new lens!



#4 Al_N

Al_N

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Posted 03 October 2020 - 10:55 AM

That's a really nice image. I also have a few vintage lenses (Pentacon 135mm and the 200mm Takumar) and get great satisfaction out of producing Astro images with them. Keep it up!

Thanks.

 

I also bought a 200mm f/4 Takumar that I received last Friday. I'll get a chance to try it out on some smaller targets Monday. Hopefully either the Wizard or Bubble nebula.



#5 alphatripleplus

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Posted 04 October 2020 - 08:53 AM

Excellent shot. I have used an ancient vintage Chinon 135mm f/2.8 and a 7nm H-alpha filter on this and similar targets, and had a lot of fun.




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