Triangle based stars

[ajh499]

Does anyone have any ideas what could cause the triangular bases on the stars in the attached image?

The points don't line up with the direction to the ground as far as I can tell and they are consistent across subs taken with different filters and different durations.

The attached image is a crop of a single 1min sub, but the points seem to be the same all over the frame. CCD Inspector in ASTAP suggests a tilt of 6-8% but not in the same direction, and the field looks to be flat.

These were taken with an ASI183MM Pro and EFW Mini on a SW ED80 scope with the 0.85x FF/FR.

I've not seen this effect with this scope when previously using a Sony a6300 on it.

This was first light for this camera and I was just testing to make sure that everything was connected and working, I didn't notice this issue until later and I haven't had a chance to try experimenting to track down the cause of the problem yet. Any suggestions of things to try would be much appreciated.

Thanks

[Star101]

Have you moved the scope to do any work on it?

My new TS65Q had a very similar issue that was caused by the lenses being too tight. 

https://www.youtube.com/watch?v=Sj_IyhRspTM This video helped me. But if the scope is ok with the other camera then maybe its something else!!

Dave.

[ajh499]

8 hours ago, Star101 said:

Have you moved the scope to do any work on it?

My new TS65Q had a very similar issue that was caused by the lenses being too tight. 

https://www.youtube.com/watch?v=Sj_IyhRspTM This video helped me. But if the scope is ok with the other camera then maybe its something else!!

Dave.

I pack it away each time I use it, so it gets moved around all the time, but that was true when using the other camera too. 

It certainly sounds like it could be pinched optics, but the only thing that I've changed is to attach the new camera with the filter wheel and new spacers.

[sonnymoon]

Hello,

I have had similarly slightly pointed stars which I have been seeking advice from FLO about. I have the sw ED80 with FF. They think it may be to do with the distance between sensor and flattener, which has to be 55mm, or 56 with the filter wheel and a mono camera. 

Might be worth checking the distance and adding/removing a 1mm spacer to see if it makes a difference. 

 

[ajh499]

I've got it set to 56mm spacing following the image at the bottom of the product page on the ZWO website. 

Wouldn't a spacing issue show up as different across the frame though? 

Next time that I get a chance I'll try to work out where along the imaging train the issue is coming from

Edited September 5, 2019 by ajh499

[ajh499]

Strange, I seem to have fixed the problem, but I'm not sure why.

I realised that I had the 2mm adapter between the EFW and the camera rather than joining them directly and having the adapter in front of the EFW as in the picture. Making that change seems to have fixed the issue.

I don't understand why, it hasn't changed the backfocus spacing to the camera

[retret66]

this is 99.99% pinched optics. Start removing flattener if you have it and see if it disappears then loosen the flattener lens retainer. If it still there, then loosen the objective lens retainer . You must use a "Lens Spanner Tool".

Edited September 16, 2019 by retret66
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