Need Help With This Strange Gradient?

[acharris77]

Hey all, so after nearly 3 months of not getting out with my scope I managed last night to get out and try and do some imaging. I wanted to capture the M42 primarily and I also tried the triplets in Leo. First up is my M42, I knew Orion was low so I thought I would use my Skywatcher LP Filter. I noticed the last time I used it a strange effect from the light pollution, but didn't get a chance till last night to try it again. And it is there again. It is the strange gradient on the right

The same effect can be seen in Leo Triplet (yes I am missing the third one...oops) not as obvious as the objects were more away from the street light.

I have check the filter for smudges and it is clean, so why the filter gives that effect I have no idea. Can anyone offer me a solution as it is only 4 months old bought from FLO.  Thanks in advance.

[happy-kat]

In lost is the lp filter on a camera lens?

[acharris77]

Hey, I should have mentioned the setup. I got a 2" LP filter on a 2" nose piece on my DSLR. Then I insert into my focuser on my Skywatcher 130P DS.

[Oddsocks]

When the camera nose-piece and filter is inserted into the focuser and the camera is at focus, looking into the front aperture of the 130P can you see the filter exposed in the focuser draw tube? can off-axis light from a nearby source like a street lamp, house light etc, shine onto the face of the filter, directly or indirectly via reflections inside the draw tube? if so, extending the OTA tube with a wrap around dew shield to shelter the filter from stray light might fix it.

Do you cap the optical viewfinder on the DSLR when used on the telescope?

There is a path possible for stray light to enter the camera sensor cavity via the optical viewfinder window, 35mm film SLR and earlier DSLR cameras had a flip up blind in the viewfinder window to block the light path but I notice many modern DSLR's these days do not have them.

[acharris77]

Thanks for the reply. The possibility of light entering could have been a possibility on the M42 one it was low and close to the street light at the time of imaging. The Leo triplet one weren't really near a light to get stray light in. Also no I don't cap the view finder but that weren't pointing near a light source. But I will take a look the next time I get the scope out as it could very well be possible.

Thanks again for the advice.