ASI 585mc - halo's

[edjrgibbs]

I managed to get a few nights out with the Asi 585mc paired with a samyang 135mm and Optolong L-eNhance. I'm getting some odd halos on stars. Any advice on what might be causing them?

[PeterCPC]

Have you tried without the filter?

[edjrgibbs]

57 minutes ago, PeterCPC said:

Have you tried without the filter?

I havent but it looks clear tonight so i might try with my Altair triband to see if any difference. 

[PeterCPC]

7 minutes ago, edjrgibbs said:

I havent but it looks clear tonight so i might try with my Altair triband to see if any difference. 

Good idea. Some filters can cause bloat.

[Elp]

The Samyang I assume you're using at f3 or so, it might be a case the light coming in is bending/refracting out of tolerance for the filter due to the speed of the lens setting, I don't think the older optolongs were designed for fast systems, I get weird light patterns when using such filters with fast optics.

Also for the Pleiades (reflection nebula/star cluster) and Andromeda (broadband galaxy) shooting with this filter is counter productive as it's use is for emission nebula strong in hydrogen alpha and o3, though you have got good results.

Edited January 30, 2023 by Elp

[edjrgibbs]

12 minutes ago, Elp said:

The Samyang I assume you're using at f3 or so, it might be a case the light coming in is bending/refracting out of tolerance for the filter due to the speed of the lens setting, I don't think the older optolongs were designed for fast systems, I get weird light patterns when using such filters with fast optics.

Also for the Pleiades (reflection nebula/star cluster) and Andromeda (broadband galaxy) shooting with this filter is counter productive as it's use is for emission nebula strong in hydrogen alpha and o3, though you have got good results.

Cheers, will give it a go this evening

 

[Budgie1]

The halos are being caused by the filter. It's a common effect of the likes of the L-eNhance & L-eXtreme filters and I get the same halos with these filters on my ED80 DS Pro scope. Fortunately they're normally left behind when you do a star removal process with StarNet2 or StarXTerminator (if you have either of these), and you can remove the halos from the background image.

As said above, using these OSC narrow band filters on galaxies and reflection nebula is generally not a good idea because you're blocking some of the main wavelengths you need for these targets. There's nothing wrong with combining data taken with & without the filter, to enhance some of the Ha in the likes of the Horsehead nebula.

So try M45 & M31 again, but just use a UV/IR cut filter, and see what a difference it makes.

[newbie alert]

4 hours ago, PeterCPC said:

Good idea. Some filters can cause bloat.

It would bloat all stars not just the bright ones.. bloat and halo's are  caused by different things

[sharkmelley]

The halos are caused by the filter.  For a small percentage of the light rays, a double internal reflection takes place within the filter glass and then the rays continue onwards to the sensor where they arrive out of focus because of the extra distance travelled.  The diameter of the halo is therefore proportional to the thickness of the glass and the (inverse) focal ratio of the optics.  

 

[Adam J]

On 30/01/2023 at 10:49, edjrgibbs said:

I managed to get a few nights out with the Asi 585mc paired with a samyang 135mm and Optolong L-eNhance. I'm getting some odd halos on stars. Any advice on what might be causing them?

Its almost certainly caused by the L-eNhance filter, they are known for it. 

Its a feature not a defect as such. 

Adam 

Edited February 2, 2023 by Adam J

[Adam J]

On 30/01/2023 at 11:58, edjrgibbs said:

I havent but it looks clear tonight so i might try with my Altair triband to see if any difference. 

and so is the Altair triband...

I recommend a UV/IR cut for broadband targets like M45 and the triband on emission nabula, honestly I would not find much use for a L-eNhance. 

Adam 

Edited February 2, 2023 by Adam J