Light Leaks and Filter Orientation

[Stevekerr]

I'm fairly new to astrophotography and this is my first season imaging with new equipment. I seem to go from thinking I'm making progress to then hit more snags. I guess that's the same for a lot of people. Three questions if I may.

1. After an imaging session last night under a very bright moon, I noticed a light gradient on my Ha images. I had taken a few shots a week or so ago under less moon and there was no obvious gradient. I took flat frames this morning and noticed they had a similar gradient. I took the flat frames again later in the day with the curtains drawn and the gradient had disappeared. I'm thinking therefore that  this may be caused by light leaking in somewhere. My question is,  would this explain the issue as seen in the attached images and is this something to worry about or is it inevitable if there is too much light around?

2. When I image in narrowband I often get less colour than I expect when I combine the HSO data. I've noticed a pattern of concentric curves in my flats, especially Sii and Oiii. I am concerned I may have installed them the wrong way round. Has anyone come across a pattern like this in their flats? Does anyone have any thoughts on the cause?

3. I experienced a lot of splodges on my Oiii images which didn't appear in the Ha or Sii lights or

the Oiii flat frames. I can't think what might have caused these

Thanks

Steve

WO GT71 with 6Aiii reducer/flattener

ASI1600MM Pro

ZWO 7 position filter wheel

ASI120MM-S

ZWO 55mm Guide Scope

ASIAIR Plus

HEQ5 Mount

[Realtimedoctor]

Did you wipe your primary lens or any of the optical surfaces with a cloth, to remove dirt or debry? 

 

[Stevekerr]

I cleaned it with a lens cleaning kit recently.

[Realtimedoctor]

1 hour ago, Stevekerr said:

I cleaned it with a lens cleaning kit recently.

Thought so. 

I think the aberrations you are seeing are, the circular motions one does while cleaning the lenses or optical surfaces. 

I suspect you have residue or marks left on the surfaces from the cleaning. 

When I clean my optical surfaces, I usually leave them to dry on their own, and pick of any water droplets with a cotton bud. 

Hope this helps. 

Cheers, 

Nish 

[scotty38]

I am not sure those sort of marks on the front element of the scope would show so clearly on an image like that. I'd expect them to be much closer to the sensor, on the filters at least but who knows....

[Stevekerr]

I’ll check that out thanks RD.

Still hoping someone else may have experienced these specific patterns.

[davew]

Those marks remind me of polishing / grinding marks that have been seen on some Sony chips. I realise the 1600 is a Panasonic but I'm sure they follow roughly the same process.

The marks were first brought to my attention by Mark Shelly ( Sharkmelly on SGL ) who discovered that some larger Sony chips were in fact smaller chips that were stitched together and so had marks that didn't align.

These may not be the same thing so treat what I'm saying as a place to start and not a definitive answer.

Dave.

[Stevekerr]

Thanks Dave. That's a possibility. There's only about 12 weeks here before we enter perpetual twilight so I think I'm going to work with it just now then strip down, clean and check the orientation of the filters before I do anything else.