What's wrong with my Lum subs

[Mark72]

Hi,

Just wonder if anybody have some thoughts about this dark band in the corner of the images.

Flats seem to be correcting everything else but this part  remains uneven on all subs and each object.

You can see it here in the right/top

www.astrobin.com/59214/?mod=none

In the attached image (stretched to show this artefact) it's low/right.

Mark

[ollypenrice]

Sorry, are you saying that this band appears in all images taken with the setup? If so I'd maybe start by reading this; https://www.sbig.com/about-us/blog/flat-fields-the-ugly-truth/

Olly

[opticalpath]

Mark, if this happens with every image and assuming you have eliminated the possibility of bad flats causing it ..... if it's practical, I would try taking a sequence of shots, then immediately another set with nothing changed except the camera (+ filters) rotated 90 degrees. If you suspect internal reflections, the comparison might help to narrow down whether the problem is to do with the optical tube or originates in the imaging train.

Adrian

[Mark72]

Thanks guys, looks it was a spider web.

Mark

[ollypenrice]

Thanks guys, looks it was a spider web.

Mark

Of course! Not the first time. I must get a better memory.

Olly

[opticalpath]

Ha!  The blighters get everywhere ... and it's that time of year!

Adrian

[Uranium235]

Same has happened here too, Ive either had a spider web inside the dew shield or something very small actually crawling across the reducer (could see it move from one shot to the other). It always pays to have a quick peek down the dew shield before starting

[Sp@ce_d]

Hehe.. I keep a vacum  (now that would be neat)   hoover in my obsy for such occasions..