Anyone know what is causing this?

[Astroblagger]

Got out last night to test my newly modded canon 450D after its filter replacement with the baader filter by astronomiser, just wandered what might be causing these strange halos around the stars? There was no dew on the lens, and the star was definately focussed, the image was taken through a megrez 72 with sky watcher field flattener, iv never had any problems like this before with the same set up, prior to the mod.

The stars in all my images seem abit bloated? i though the baader replacement filter was suppose the stop star bloating. Should i be getting in touch with astronomiser or is this normal and/or is there any way to get rid of these halos? Im wandering is it a telescope issue or a camera issue. the photos are 10sec exposures.

[themos]

Well, you should probably try it on some other optics (you list a few!) first, and if they all show the same behaviour, take it back!

[Astroscot2]

Ive seen this sort of reflection before caused by my own corrector, I would say that is the culprit rather than the camera. Stars dont look too bloated in the images.

The reflections can be quite difficult to clean up when processing, avoid imaging bright stars or look at a higher quality corrector which I did and the halos vanished..

[Astroblagger]

yes will try it out with my other scopes next chance i get, with corrector in and out, Funny that i had no problem with the field flattener before?

[Merlin66]

Try rotating the camera relative to the reducer/ flattener....see if the halo always appears in the same position...could be the reflection from one of the surfaces (now you have a more sensitive chip they may be showing up, whereas they were suppressed by the poor response pre-mod.)

[Astroblagger]

Managed to get out tonight when there were afew clear spells to test the camera through a different scope these photos are taken through a SW 120ED and the problem is still present. Tried with flattener in and out and it still happens. It is definately worse the redder the star is. I tested it on sadr and vega. Can anyone think of anything else? or im i going to have to send it back to astronomiser?

[JimStan]

I am going to bet that the two faces of the filter are not parallel, so you are getting an internal reflection off of one side, as compared to the other. If the two faces were parallel, the internal reflection would be suppressed by the transmitted light from the other side .

Don't know if I am being clear, or not, but it sure does look like the problem is with the filter.

Good luck! Jim S.