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Re: Reflections in Images

Roland Christen
 

I believe from the images that I see that the reflections are close to the camera, somewhere inside the small parts that connect the camera to the main scope. You will need to remove the camera and look up the optical train, but not up the main tube, rather up the areas inside the small parts (focuser drawtube, field flattener, filter wheel etc.).
 
The reflections are coming from nearly focused images of bright star just outside the field of the camera, but still inside the small parts that connect the camera to the main tube. They cannot really come from the large parts that make up the main scope, they would be way too diffuse by the time they came down to the camera itself.
 
Rolando
 
 

-----Original Message-----
From: 'Steven Reilly' sreilly24590@... [ap-gto]
To: ap-gto
Sent: Wed, Feb 3, 2016 11:33 am
Subject: RE: [ap-gto] Reflections in Images



I was hoping to see a reply from you Roland. Yes, I’ve done that too. The dovetail rails that are installed on the ota have plates that are threaded that the bolt screws into from the dovetail side. These were shiny black and I have long ago covered them with the adhesive backed flocking paper. I’ve taken a few images of the inside of the ota and noticed stainless steel hex head screws that hold the spider vanes to the ota. I’m going to see if I can cover these with the flocking paper just in case. I’ll have a page posted soon.
 
 
Thanks,
 
Steve
 
From: ap-gto@... [mailto:ap-gto@...]
Sent: Wednesday, February 03, 2016 11:36 AM
To: ap-gto@...
Subject: Re: [ap-gto] Reflections in Images
 
 
Forget about blackening the edges of filters, these are never in the optical path.
Best to remove the camera, point the scope to a brightly lit wall, and LOOK with your eyeball up the optical train. You will soon see where the reflections are, and you will probably see somewhere a shiny black anodized surface. At low grazing angles it will reflect like a mirror. Painting the surface with a grainy flat black paint will go a long way to reduce reflections. Alternative you can cover the surface with adhesive backed black felt.
 
Rolando
 
 
-----Original Message-----
From: Stuart Heggie stuart.j.heggie@... [ap-gto] <ap-gto@...>
To: ap-gto <ap-gto@...>
Sent: Wed, Feb 3, 2016 10:25 am
Subject: Re: [ap-gto] Reflections in Images
 
Kent, I too think it is his filters but the positioning of the flaring from the very edge of the field suggests to me it is the edge of the filters not the coatings (else this would be on all bright stars IN the field). There was a distinct debate about the filters not having blackened sides and later sets shipped with the sides of the filters blackened. 
 
I think that is the problem.
 
Stuart
 
On Wed, Feb 3, 2016 at 11:15 AM, Kent Kirkley kgkirkley@... [ap-gto] <ap-gto@...> wrote:
 
Steve:
 
How old are your filters?
Astro imaging filters have gone through two evolutions, hence in the case of Astrodon filters, Series 1 and Series 2. I believe Baader filters have also done this. The later series have much better anti reflection coatings and on both sides. Your reflections appear to be of your mirror and secondary....much like what you'd see with an eyepiece and an out of focus position. If your filters are before the improved coatings I would suspect them.
 
Kent Kirkley
 
-----Original Message-----
From: 'Steven Reilly' sreilly24590@... [ap-gto] <ap-gto@...>
To: ap-gto <ap-gto@...>
Sent: Wed, Feb 3, 2016 9:26 am
Subject: RE: [ap-gto] Reflections in Images
 
 
At this point there is no OAG in place. I had one when I had the flattener in place though but removed and tried with the same results. I guess I could remove the filter carousel and see if that makes a difference. I’m using Baader 50mm unmounted filters in my FW8.
 
Thanks,
 
Steve
 
 
From: ap-gto@... [mailto:ap-gto@...]
Sent: Wednesday, February 03, 2016 10:13 AM
To: ap-gto@...
Subject: Re: [ap-gto] Reflections in Images
 
 
Steve, the reflection could be from inside your filter wheel or adapters for connecting it. Or from an OAG. I recall years ago that some people complained of flaring and odd artifacts that were traced to the fact that their filters' uncoated, unblackened edges were exposed and the solution was to take a thick sharpie and colour in the sides of the glass filters.
 
Stuart
 
On Wed, Feb 3, 2016 at 10:09 AM, 'Steven Reilly' sreilly24590@... [ap-gto] <ap-gto@...> wrote:
 
Joel,
 
The ota tube is carbon fiber and a dull black interior. There are two small dovetail bars mounted near the end of the ota for additional counter weights if needed. I guess I could remove them and see if that makes a difference. Other than that there is just the spider vane holding the secondary and its stepper motor. It is baffled well. I’ll try this and see if that make a difference. I have a 3-pound weight that I can find another way to attach for balance.
 
Thanks,
 
Steve
 
 
From: ap-gto@... [mailto:ap-gto@...]
Sent: Tuesday, February 02, 2016 11:49 PM
To: ap-gto@...
Subject: Re: [ap-gto] Reflections in Images
 
 
Steve,
I've seen this kind of reflection caused by a bright object just off the field of view.  If your date is correct then NGC3521 was very close to Jupiter and Sh2-263 was rather close to Bellatrix.  The reason the reflection seems to change is because as time goes on the relative position of your camera orientation and slight differences in the camera sky position can change how intense the reflection is.  I've had cases where I moved the scope just a tiny distance away from the bright star or object and the reflection went away.  Yours is pretty extreme though.  I don't know if I've seen one quite that bright.
 
But that may only be half the problem.  I suspect your scope may have something shiny in it that is reflecting.  Is there any silver metal somewhere in the tube?  Is it baffled well?  Is it painted black?  
joel
 
On Tue, Feb 2, 2016 at 10:12 PM, 'Steven Reilly' sreilly24590@... [ap-gto] <ap-gto@...> wrote:
 
Back a few months ago I posted a webpage with some reflections I was getting in some images. The link to that page is http://www.astral-imaging.com/reflection.html Since then I have removed the flattener lens from the RC and am again seeing some reflections I had thought were from the lens. The latest images to show this strongly are of NGC3521 and seen here  http://www.astral-imaging.com/reflections.html Any ideas how to track down the source of these reflections would be great. The telescope is a OGS 12.5” RC with a Pyxis 3” rotator, STL-11002M w/fw8.
 
Thanks,
 
Steve
 
 


 
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