Go Back   IceInSpace > Equipment > Astrophotography and Imaging Equipment and Discussions

Reply
 
Thread Tools Rate Thread
  #1  
Old 12-11-2014, 10:22 AM
Andy01's Avatar
Andy01 (Andy)
My God it's full of stars

Andy01 is offline
 
Join Date: Mar 2012
Location: Melbourne
Posts: 3,253
What the? Help please...Bizarre spots on flats

Hi everyone,

Here's a weird new problem
Check out these flats I took yesterday evening.
There appear to be strange black spots that move between frames and filters.

I use a QSI wsg-8 which has the OAG prism in front of the filters.
I used the same t-shirt I always use at dusk, yes it's clean!

I triple checked the image train for obvious dust or aliens, and removed and checked the flattener, LP filter and visually checked the objective and surface of the filters. Nothing obvious there.

Thinking maybe it's a light leak or flare I removed the OAG and replaced the cap - no change. I then wrapped all connecting image train elements in dark fabric - no change.

To try to i.d. the problem, I then varied both exposure times and filters.
In order l-r these are 1 sec Ha, .05 sec C, .05 sec SII, 5 sec Ha, 10 sec Ha, 30 sec Ha, 5 sec Cyan and 60 sec OIII.

I'm guessing it's a foreign body or dust BEHIND the filters or possibly on the CCD surface?

As it's a new camera, I'm reluctant to dismantle the camera & filter wheel to access the CCD.
Not sure how to open the shutter for a visual inspection of the CCD either.

Any ideas?

Darn shame as it was a rare clear spring night in Melbourne and I've now got these marks all over my subs from the night's imaging as well.

Cheers

Andy
Attached Thumbnails
Click for full-size image (1.jpg)
132.7 KB29 views
Click for full-size image (10.jpg)
129.9 KB35 views
Click for full-size image (11.jpg)
125.6 KB29 views
Click for full-size image (18.jpg)
168.4 KB26 views
Click for full-size image (20.jpg)
125.0 KB27 views
Click for full-size image (23.jpg)
148.6 KB31 views
Click for full-size image (24.jpg)
147.0 KB34 views
Click for full-size image (30.jpg)
171.8 KB25 views
Reply With Quote
  #2  
Old 12-11-2014, 10:55 AM
Merlin66's Avatar
Merlin66 (Ken)
Registered User

Merlin66 is offline
 
Join Date: Oct 2005
Location: Junortoun Vic
Posts: 8,904
Andy,
those bunnies are very sharp...to me that infers they are on the CCD chip or very very close to it.....
Reply With Quote
  #3  
Old 12-11-2014, 11:10 AM
RickS's Avatar
RickS (Rick)
PI cult recruiter

RickS is offline
 
Join Date: Apr 2010
Location: Brisbane
Posts: 10,584
You can calculate the distance from the sensor fairly easily: http://www.wilmslowastro.com/software/formulae.htm#Dust

This will tell you where to look...

Cheers,
Rick.
Reply With Quote
  #4  
Old 12-11-2014, 11:19 AM
Andy01's Avatar
Andy01 (Andy)
My God it's full of stars

Andy01 is offline
 
Join Date: Mar 2012
Location: Melbourne
Posts: 3,253
Quote:
Originally Posted by Merlin66 View Post
Andy,
those bunnies are very sharp...to me that infers they are on the CCD chip or very very close to it.....
Thanks Merlin

Quote:
Originally Posted by RickS View Post
You can calculate the distance from the sensor fairly easily: http://www.wilmslowastro.com/software/formulae.htm#Dust

This will tell you where to look...

Cheers,
Rick.
Oh cool, cheers Rick - so looks like around 6mm in front - now to pull the specs and see how to safely access/clean in front of the CCD.
Attached Thumbnails
Click for full-size image (Screen Shot 2014-11-12 at 12.16.12 PM.png)
47.3 KB19 views
Reply With Quote
  #5  
Old 12-11-2014, 12:28 PM
ZeroID's Avatar
ZeroID (Brent)
Lost in Space ....

ZeroID is offline
 
Join Date: May 2010
Location: Auckland, NZ
Posts: 4,949
6mm, .. I'd say dew on the window in front of the sensor. Internal or external, ... dunno. They appear to move independently on longer exposures.
Reply With Quote
  #6  
Old 20-11-2014, 04:02 PM
MelD's Avatar
MelD (Melvyn)
Mel Davis

MelD is offline
 
Join Date: Apr 2008
Location: Sydney Australia
Posts: 34
By any chance, are they alive? They certainly appear mobile. My pier and mount seem to be very attractive to tiny ants, despite the multiple applications of surface insecticides that I spread around. Just a thought.
Mel
Reply With Quote
  #7  
Old 20-11-2014, 04:35 PM
leon's Avatar
leon
Registered User

leon is offline
 
Join Date: Apr 2006
Location: Warrnambool
Posts: 12,430
Tiny ants now that is possible, I have seen them that small one needs a magnifying glass to view them properly.

Leon
Reply With Quote
  #8  
Old 20-11-2014, 05:44 PM
alistairsam's Avatar
alistairsam
Registered User

alistairsam is offline
 
Join Date: Nov 2009
Location: Box Hill North, Vic
Posts: 1,837
hi Andy,

can't you keep your camera on a desk, start a 2 min luminosity frame and look through from the scope end of the wheel, that would open the shutter and you should be able to see through to the CCD surface.

Does it disappear when your cooling is off?

Cheers
Alistair
Reply With Quote
  #9  
Old 23-11-2014, 06:11 AM
Andy01's Avatar
Andy01 (Andy)
My God it's full of stars

Andy01 is offline
 
Join Date: Mar 2012
Location: Melbourne
Posts: 3,253
Quote:
Originally Posted by ZeroID View Post
6mm, .. I'd say dew on the window in front of the sensor. Internal or external, ... dunno. They appear to move independently on longer exposures.
Sure was weird. I just recleaned the glass in front of the CCD chamber again.

Quote:
Originally Posted by MelD View Post
By any chance, are they alive? They certainly appear mobile. My pier and mount seem to be very attractive to tiny ants, despite the multiple applications of surface insecticides that I spread around. Just a thought.
Mel
Maybe? Not sure... Interesting theory

Quote:
Originally Posted by leon View Post
Tiny ants now that is possible, I have seen them that small one needs a magnifying glass to view them properly.

Leon
There have been some infestations of flying ants around, and the scope is set up near my pool- but they're the normal 1cm size. Not sure about microscopic ones?

Quote:
Originally Posted by alistairsam View Post
hi Andy,

can't you keep your camera on a desk, start a 2 min luminosity frame and look through from the scope end of the wheel, that would open the shutter and you should be able to see through to the CCD surface.

Does it disappear when your cooling is off?

Cheers
Alistair
Hey Alistair, yep did that - it's the only way I could figure out how to access the ccd chamber window. I spied a teeny tiny dust mote that i was able to remove but that was all. Havn't tried testing uncooled, are you thinking the fan is sucking something in?

Thanks for all your input everyone. After exhaustive cleaning it's a big improvement but I'm still very wary of something odd going on!

Cheers
Andy
Reply With Quote
  #10  
Old 23-11-2014, 07:56 AM
Merlin66's Avatar
Merlin66 (Ken)
Registered User

Merlin66 is offline
 
Join Date: Oct 2005
Location: Junortoun Vic
Posts: 8,904
One of my guys found condensation droplets forming on his CCD....
Reply With Quote
  #11  
Old 23-11-2014, 09:45 AM
Peter Ward's Avatar
Peter Ward
Galaxy hitchhiking guide

Peter Ward is offline
 
Join Date: Dec 2007
Location: The Shire
Posts: 8,090
I ran some image processing routines over your data and...yes, I've seen this sort of thing before.

You can get rid of the problem by purchasing a two axis joystick for the host PC....
Attached Thumbnails
Click for full-size image (pacman.jpg)
85.6 KB24 views
Reply With Quote
Reply

Bookmarks

Thread Tools
Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT +10. The time is now 03:01 AM.

Powered by vBulletin Version 3.8.7 | Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Advertisement
Bintel
Advertisement
Testar
Advertisement