Jump to content

  •  

CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.

Photo

NexStar 6SE - M33 with a Weird Semi Circle Shadow along the Bottom when Imaging

astrophotography
  • Please log in to reply
5 replies to this topic

#1 lkannard

lkannard

    Explorer 1

  • -----
  • topic starter
  • Posts: 63
  • Joined: 12 Jul 2016

Posted 21 October 2019 - 12:01 PM

I took the images with a Celestron NexStar 6SE, the 6.3 Focal Reducer, and a Nikon D7100.  This was my first time to use the Focal Reducer.

 

I stacked thirty two, 25 second subs of M33 in DeepSkyStacker and out popped this when I was processing in Gimp. I see a Weird Semi Circle Shadow along the Bottom. 

 

I never got a shadow like like until I tried the Focal Reducer.  I have tried to use my Colombo like investigation skills to try and figure out want is causing the shadow, but I can't.

 

Could it be collimation and the semi circle line is the secondary mirror?  Any help would be much appreciated.

 

M33 with Weird Semi Circle Shadow along the Bottom

 



#2 cmooney91

cmooney91

    Vostok 1

  • *****
  • Posts: 155
  • Joined: 18 Sep 2017
  • Loc: Massachusetts

Posted 21 October 2019 - 12:33 PM

Only thing I can think of is a hair on the reducer lens causing a shadow


  • lkannard likes this

#3 Gary Z

Gary Z

    Apollo

  • *****
  • Posts: 1444
  • Joined: 26 Jan 2012
  • Loc: New Mexico

Posted 21 October 2019 - 01:24 PM

 

 

Have you looked closely at the FR?  Which Focal reducer are you using, Celestron? Do any flats?  Were your camera settings the same as they are without the FR?

 

Gary


  • lkannard likes this

#4 junomike

junomike

    Hubble

  • *****
  • Moderators
  • Posts: 17189
  • Joined: 07 Sep 2009
  • Loc: Ontario

Posted 21 October 2019 - 02:46 PM

Second the "hair" theory.  Looks like it to me.


  • lkannard likes this

#5 lkannard

lkannard

    Explorer 1

  • -----
  • topic starter
  • Posts: 63
  • Joined: 12 Jul 2016

Posted 21 October 2019 - 08:57 PM

Only thing I can think of is a hair on the reducer lens causing a shadow

I like the Hair Theory.  I will investigate.  Einstein might not have figured this one out.



#6 lkannard

lkannard

    Explorer 1

  • -----
  • topic starter
  • Posts: 63
  • Joined: 12 Jul 2016

Posted 25 October 2019 - 02:41 PM

The verdict is in, and yes, it was a single strand of hair. 

 

On Wednesday I was taking daytime images of the Moon.  I had my head under a towel for darkness.  When I turned on Live view on my Nikon D7100, what did I see?  That pesky semi circle shadow in the display.  So I knew the obstruction was on the DSLR and not in my 6SE or on the Focal Reducer.  

 

So after removing the T-Adapter and T-Ring and looking on the sensor with the mirror being up, I could make out the hair laying across the sensor.  Using a squeeze bulb, I was able to get the hair removed.

 

All is well with the world again.


  • saguaro likes this


CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.


Recent Topics





Also tagged with one or more of these keywords: astrophotography



Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics