Light leakage through Filter Wheel

[tomato]

After setting up an Atik 383 and EFW2 I noticed a bright band across the top of the subs, this was confirmed when taking darks the next day. By a process of elimination I traced this to light ingress on the FW, coming through where the USB and power connections are located. When imaging the observatory is not dark (lots of LEDs) so I am hoping that’s where the bright band was coming from when taking light frames.

I have fixed this by gluing a piece of floc material to the end of the casing, cutting small slots in it for the connectors to go through.

Is this normal or has something gone missing  internally in the wheel? I couldn’t see anything amiss when changing the filters.

[Skipper Billy]

Turn the LED's off !! 😉 

I get the same issue with my EFW3 - I traced it down by taking darks indoors in a dark room whilst shining a torch all around the camera and filter wheel. I cured it by putting strips of self adhesive aluminium tape over the affected areas which were the cable entry/motor housing on the EFW and the cooling vents of the camera.

[Physopto]

Surely that means the filter wheel is not fit for purpose ! Atik should be ashamed to produce such a device and such a well known name as well.

Derek

[Skipper Billy]

28 minutes ago, Physopto said:

Surely that means the filter wheel is not fit for purpose ! Atik should be ashamed to produce such a device and such a well known name as well.

It's not a problem when it's used in the dark - which I guess is what it's designed for 😉 

[RayD]

Have a look at a video I did on this subject.  It isn't just Atik, it's a common thing and why darks should ideally be taken in the dark.

 

Edited May 13, 2020 by RayD

[Physopto]

If I do have a problem, try this. 

I have an old light bag that I used to use to change out film from my cameras. It was used many times in the past to take out partially used 35mm cassettes from the camera and put in different ISO films  for different lighting conditions  The part used cassette could then be boxed up until needed later on and reinserted under the same conditions. If you don't know about these old ideas, the bag consisted of a double layer of dark light proof material. It had a zip bottom and two light cuffs. By that I mean it looked a bit like a black T shirt. Having  two arm holes with the zipped bit at the bottom(waist).  The arm holes were very tight as they used elastic to crunch them onto your arms. So you placed your hands into the bag through the arm holes  i.e. the  wrong way around so you could work on the camera inside the bag.

Anyway I used that old bag around the CCD camera and fitted two waste pipes into the arm holes. One pointing up the other down. That allows air flow for the ccd cooling. Doing this allows dark frames at any time of day without much  chance if any  of light leakage.

Very old idea but works if done carefully. Just paint the pipes black.

Derek

[tomato]

It is strange, the filter wheel was previously attached to an ASI 178 with no light ingress problem both in the dark and daylight. Maybe because the chip was a lot smaller, further down the light path?

Most of the LEDs in the dome serve a useful purpose (mount comms and status healthy, dome aperture location healthy, local voltage readout on the scopes) so I would be reluctant to cover them all up, they also help me to avoid walking into the rig, two Esprit 150s in a 2.2 m dome equals not a lot of room to manoeuvre. 
 

It’s no big deal to fix, and I guess have found a plus for integral filter wheels...

[RayD]

32 minutes ago, tomato said:

It is strange, the filter wheel was previously attached to an ASI 178 with no light ingress problem both in the dark and daylight. Maybe because the chip was a lot smaller, further down the light path?

Yeah it is a bit of a nuisance, and only needs the smallest bit of light.  I must admit I've never noticed it on my light frames, only darks, which I only redo every few months so is not too painful to make sure they are done when the obsy is dark.  I can only assume the level of lighting is fairly high if it is affecting it through these apertures, but are you certain is isn't through the objective end ie reflected light?  I have this when I leave my IR light on my camera at certain angles, so turn this off when I image.

Hope you get it resolved as small things like this are a proper annoyance.

[Gina]

I have the same problem with the ZWO full size wheel but not with the EFWmini.  I think all filter wheels should be light sealed and be suitable for taking darks and flat-darks in daylight with a metal cap on the scope or lens. (Plastic caps let light through, even black ones!!)

Edited May 16, 2020 by Gina

[tomato]

I am now not so sure there was sufficient light ingress to affect the lights. I am using SGP and on frame and focus the light band at the top of the frame was still present, but when the sequence was running with 300 sec subs the saved frames where perfectly OK. 
 

[MarkAR]

Could it be amp glow?

[tomato]

18 hours ago, MarkAR said:

Could it be amp glow?

I don’t think so, the artefact disappeared on extended subs, if it was amp glow this would get worse over time. Also, in my experience CCDs are less prone to amp glow than CMOS cameras.

[RayD]

18 hours ago, tomato said:

I am now not so sure there was sufficient light ingress to affect the lights. I am using SGP and on frame and focus the light band at the top of the frame was still present, but when the sequence was running with 300 sec subs the saved frames where perfectly OK. 
 

If using frame and focus in SGPro make sure the 'high speed download' box in unticked.

[Skipper Billy]

18 hours ago, RayD said:

If using frame and focus in SGPro make sure the 'high speed download' box in unticked.

Does that make a difference Ray??

One thing I found that made a difference was turning off the IR light on the obsy night vision webcam - much better with it turned off.

Edited May 18, 2020 by Skipper Billy
typo

[RayD]

5 minutes ago, Skipper Billy said:

Does that make a difference Ray??

One thing I found that made a difference was turning off the IR light on the obsy night vision webcam - much better with it turned off.

It does, David.  Only for frame and focus, not on a sequence.

I agree with the IR light.  I've used a Yi camera for some time now (I see you do too) which has the function to turn the IR light off remotely, which I do when imaging.

[tomato]

Previously I got these bloom artefacts from bright stars when using Frame and focus in SGP, again not there when in sequence mode.

 

[RayD]

Yes this can happen in frame and focus when using the high speed download function, and changes in severity depending on sensor.  With the 16200 it could be particularly bad, sometimes pretty much washing the image out.  Unchecking "use high speed download" in the camera module fixed this.  

None of the artefacts showing in frame and focus are there on the main sequence images.  If it isn't this then I'm not really sure, but it does seem odd otherwise that they are there for F&F but not in the main images.

Edited May 18, 2020 by RayD

[symmetal]

36 minutes ago, RayD said:

Yes this can happen in frame and focus when using the high speed download function, and changes in severity depending on sensor.  With the 16200 it could be particularly bad, sometimes pretty much washing the image out.  Unchecking "use high speed download" in the camera module fixed this.  

None of the artefacts showing in frame and focus are there on the main sequence images.  If it isn't this then I'm not really sure, but it does seem odd otherwise that they are there for F&F but not in the main images.

Hi Ray,

SGP 'High Speed Download' setting is only used during frame and focus, auto focus and plate solving. ie. temporary frames which aren't kept. Also the camera has to support this option for it to have an effect. For sequences it is ignored and the normal download speed is used. High speed download does give images with more noise.

Alan

Edited May 18, 2020 by symmetal

[RayD]

40 minutes ago, symmetal said:

Hi Ray,

SGP 'High Speed Download' setting is only used during frame and focus, auto focus and plate solving. ie. temporary frames which aren't kept. Also the camera has to support this option for it to have an effect. For sequences it is ignored and the normal download speed is used. High speed download does give images with more noise.

Alan

Hi Alan.  Yes that's what I'm trying to say, not very clearly, the artefacts which are there in F&F with high speed download checked, will not be there in the main sequence images.  My apologies as I may have read wrongly, as is often the case, but thought that is what is happening here.  

With the 16200 it was particularly bad, making it hard sometimes to frame images as they completely washed out, so unchecking high speed download for F&F was essential.

If the same artefacts are there during the actual sequence then I don't know why, as the bad artefacts are only there in F&F with high speed download checked, in my experiences.

[tomato]

Also, it doesn't appear to happen with the ASI178 CMOS cameras,  only with the KAF 8300 CCDs and then only on the Atik 383, not the Moravian G2-8300.

[Skipper Billy]

1 hour ago, RayD said:

Yes this can happen in frame and focus when using the high speed download function, and changes in severity depending on sensor.  With the 16200 it could be particularly bad, sometimes pretty much washing the image out.  Unchecking "use high speed download" in the camera module fixed this.  

Cheers Ray - I have learned something! 😉 

[symmetal]

35 minutes ago, RayD said:

Hi Alan.  Yes that's what I'm trying to say, not very clearly, the artefacts which are there in F&F with high speed download checked, will not be there in the main sequence images.  My apologies as I may have read wrongly, as is often the case, but thought that is what is happening here.  

With the 16200 it was particularly bad, making it hard sometimes to frame images as they completely washed out, so unchecking high speed download for F&F was essential.

If the same artefacts are there during the actual sequence then I don't know why, as the bad artefacts are only there in F&F with high speed download checked, in my experiences.

No problem Ray. To me it seemed you just implied that 'High Speed Download' wasn't used in sequencing but I thought I'd clarify that it definately isn't. At least the manual says it isn't. 😀

Alan