light leakage into OTA - common ?

[powerlord]

Hi chaps, I noticed today that my darks I was taking were blown out. Which explains why they didn't work yesterday in processing! duh. should have checked histogram.

I traced the light leakage into the ring where the focuser tube moves in and out of the bottom of the OTA. This is an ED72.

Is this a common thing with a simple fix, or is it either a dismantle and try and trace and try to fix ? washer/oring ?

alternative, is insulating tape around the tube there - that works as it's how I found the light leakage, but hardly ideal.

I doubt it was making much difference during shooting at night, but can't help.

stu

[Chefgage]

5 minutes ago, powerlord said:

Hi chaps, I noticed today that my darks I was taking were blown out. Which explains why they didn't work yesterday in processing! duh. should have checked histogram.

I traced the light leakage into the ring where the focuser tube moves in and out of the bottom of the OTA. This is an ED72.

Is this a common thing with a simple fix, or is it either a dismantle and try and trace and try to fix ? washer/oring ?

alternative, is insulating tape around the tube there - that works as it's how I found the light leakage, but hardly ideal.

I doubt it was making much difference during shooting at night, but can't help.

stu

I have an ed72 but have not come across this problem. But thinking about it when I used to take darks I used to put a black pillow case over the camera/focuser end which maybe stopped the light leakage from happening?

[tooth_dr]

36 minutes ago, powerlord said:

Hi chaps, I noticed today that my darks I was taking were blown out. Which explains why they didn't work yesterday in processing! duh. should have checked histogram.

I traced the light leakage into the ring where the focuser tube moves in and out of the bottom of the OTA. This is an ED72.

Is this a common thing with a simple fix, or is it either a dismantle and try and trace and try to fix ? washer/oring ?

alternative, is insulating tape around the tube there - that works as it's how I found the light leakage, but hardly ideal.

I doubt it was making much difference during shooting at night, but can't help.

stu

I have found light leakage to generally be an issue for me, and so I only shoot darks and flats and bias etc at night.   As an alternative to covering everything and fixing the light leak, you could just remove the camera and screw on the metal cap over the opening then take your darks.

[Starwiz]

36 minutes ago, powerlord said:

Hi chaps, I noticed today that my darks I was taking were blown out. Which explains why they didn't work yesterday in processing! duh. should have checked histogram.

I traced the light leakage into the ring where the focuser tube moves in and out of the bottom of the OTA. This is an ED72.

Is this a common thing with a simple fix, or is it either a dismantle and try and trace and try to fix ? washer/oring ?

alternative, is insulating tape around the tube there - that works as it's how I found the light leakage, but hardly ideal.

I doubt it was making much difference during shooting at night, but can't help.

stu

Yes, it's common.

I have the same with my SW200P.

I found light leakage at the focuser and at the primary mirror.  I use dark cloth shrouds.

The best way to find where it's getting in is to have your camera running in a dark room, then go around with a torch or mobile phone and note where the image changes.

John

[powerlord]

Ah fair enough. I just took the camera off and stuck cap on for darks. easy enough. But of course, could be affecting night lights for long exposures, so want to fix. I was shooting 60 seconds with asi224 on high gain so even a small leakage from ground light might be affecting it. I'll just make up a wee cover around there - I reckon a velvet 'scrunchy' hair band will work ideal.

stu

[ollypenrice]

I don't do darks with the camera on the scope. Having compared on-scope and off-scope darks I found a significant difference between the two. Given that I'm not particularly persuaded by darks anyway, I certainly have no interest in using inaccurate ones. I take off the camera and use the screw-on metal chip cover provided by Atik when I do use darks. When I don't, I use a master bias as a dark, a bad pixel map and a hot pixel filter.

If you do want to do on-scope darks, do them in the dark.

Olly