Horse Head with odd star glare

[bluesilver]

Hi, I have taken this with a Skywatcher Esprit 150 with a .77 reducer
Camera is a asi2600mc and filter is a OPTOLONG L-PRO Filter

I did a run of 90 x 20 second exposures for a test
All stacked with Darks, Flats and Dark flats in Deep Sky Stacker
Processed with StarTools.

I also tried the same target with 2 minute exposers and got the same odd star glare.

Tried another target completely different, the Dolphin Nebular SH2-308 and got the same effect on a different star.

I am just trying to find out if this is normal or is it something that i have to look into more deeply?
I removed the dew shield and put some flocking material inside to see if that had any effect, but no change.

I was planning to try the same target with the same 20 second exposures but without the filter and no reducer to see if there is any change, but clouds are now forecast here for the next week at least.

I had an image of the Orion Nebular a few months back and no odd rings around any stars there.

Any advice would be appreciated.
Cheers,
Peter.

[AdamJL]

Hi Peter. Try turning the filter around, it might be facing the wrong way. It can cause these sorts of halos

[bluesilver]

Thanks for the advice,
Didn't even think of that, sounds so simple.
Will give that a go next time the clods clear.
Very much appreciated.

[oska]

I'm interested in how you get on with this Peter, please update us with your results, good or bad.

[The_bluester]

The second test would be to remove the filter altogether.

[bluesilver]

I will update the results.
Might be a week or so though, shift work gets in the way a tad, plus cloudy weather most of this week.
Will go with flipping the filter over first and then remove the filter, hoping i can get all of this done in the one night.
I don't think i will worry about calibration frames though.
I did a check on just one single uncalibrated frame just to make sure and the glare was still there.

[bluesilver]

I had the chance to do about a hour of testing a few different things last night.
So tried flipping the filter over and got the same result.
Tried flipping it back over again just to make sure and same result.
Removed the filter all together and the issue is solved, no odd star glare.

So now just got to figure out what is going on with the filter.
I might have to get a ZWO filter wheel.

The filter OPTOLONG L-PRO, is a 2" filter and i am using the ZWO OAG/L
So it hasn't got the standard ZWO slide in slide out filter draw, it has one of those odd ZWO spacers where you screw the filter into.
Maybe this could be causing the issues.
If i can find a second hand ZWO filter wheel for 2" filters, this may be the answer.

[Bodon]

Peter, as you are using a colour camera no need for a filter wheel (unless you really want one); put a M54 filter draw on your train instead. On my ED72 I have the SW rotator. It also fits an SW Evostar 150 and a 2" filter can be screwed into that. Maybe it can fit on your scope as another cheaper solution. An email to SW will let you know if it fits. https://www.ozscopes.com.au/skywatcher-evoframe-rotational-adaptor.html
I use a 2" optolong ultimate and get a small halo on Barnard as well.....

[bluesilver]

Appreciate all advice.
I wasn't aware of a M54 Filter draw, i will look into that one.
At the moment i have the filter screwed into a M54 adaptor with a m54 -m48 adaptor
https://astronomy-imaging-camera.com/product/zwo-m54-adapter-replacing-efw
I was thinking that the filter might be sitting too far out or not far enough out from the camera itself.

[AstroViking]

ZWO also make an M48 filter drawer that takes 2" filters.

Just be wary if you order extra drawers - they changed the design of the drawers and drawer holders - where they used to have 2 drawers (one M54, one M48) they now have one drawer that fits both holders.

The new drawers are not compatible with the old holders. I found this out the hard way. Thankfully BinTel were able to provide me with an old drawer.

Also, aren't filters supposed to go as close to the camera as possible? I'm wondering if the star halo you're seeing is light passing through the filter then bouncing off the sensor's glass cover onto the back of the filter and then into the sensor...

Cheers,
V

[bluesilver]

Some very good theory ideas, anything will help.
I have some smaller 1.25" filters that i might try out.
Just means removing the OAG from the imaging train and using a regular guide scope if i want to do long exposures.
Worth a try with the smaller filters just to see if the effect is still there.
That way it will at least start eliminating a few things i am thinking.
I have found that to test all i have to do is take am image of one of the brighter stars, so that makes things just a bit quicker also.

[Bodon]

My bad, should have written M48 filter draw and not M54. The rotator is M54.