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

[WolfieGlos]

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?

Hi, bit of a thread revive thanks to a Google search, but I’m wondering if you ever managed to resolve this?

I have the ASI 585mc and using the Askar C1 Ha/OIII filter or Optolong l’enhance, I am getting these same star halos too.

But I am getting them with both the Samyang 135 (at f2) but also, oddly, with the Starfield 102 at f5.6 with a reducer.

I’m actually wondering if the camera is also at fault here. I never had these halos with the lenhance using a DSLR on the same scope.

[Elp]

I'd err toward a filter being the issue but when I had the 485 and did short sessions on M45 and M42 I still had the halo issue around the brightest stars, was still using a lum filter, never tried without one.

[StevieDvd]

Yes likely to be the filter as explained in this YouTube video placement of the filter can affect the halo apparently, though I have not tried that myself (yet).

 

[WolfieGlos]

5 hours ago, Elp said:

I'd err toward a filter being the issue but when I had the 485 and did short sessions on M45 and M42 I still had the halo issue around the brightest stars, was still using a lum filter, never tried without one.

Everything I read suggests it's the filter. I've had the Askar C1 for a while now, well beyond the returns period, and I found this problem during the summer months with the 585mc.

Having used the l'enhance (clip-in) filter with the DSLR and never having any issues, I've just purchased the 2" version (to also go with the 2600mc when I upgrade) and I expected it to work again. But nope, same issue as the Askar filter, and also the same type and look to the halos. They are actually a pinkish colour, and only using SCNR (then invert, SCNR, invert back) on the star layer can I remove that horrific colour - as below example.

This has caught me by surprised, as I've heard of the l'extreme producing these halos, but not the l'enhance.

But I find it odd that 2 different filters (similar bandpass to be fair) - but they have the same effect on 2 different optical systems at different f-ratios - with the only item that remains unchanged being the camera. I wonder if the l'extreme f/2 filter would make a difference.

5 hours ago, StevieDvd said:

Yes likely to be the filter as explained in this YouTube video placement of the filter can affect the halo apparently, though I have not tried that myself (yet).

That's very interesting.

So when I had previously used the l'enhance clip-filter with the DSLR, being a clip-on it is positioned in the camera body directly over the sensor.

With the 2" filters, they are held in a ZWO filter drawer further up the imaging train.

According to the video at 6 mins and on, he explains that the closer the filter is to the sensor, the more reduced the halo will be from the reflections. So this would explain why the halo's are more prevalent, and possibly I've purchased the l'enhance 2" filter for no reason. I suppose the question now, is how can you move the filter closer to the 585's sensor to test this without messing up backfocus!

I suppose another option is to find a better (£££) filter that has better anti-reflective coatings.

Perhaps I should stick to broadband. Or shoot RGB stars, instead of the SCNR/Invert trick with dualband stars.

Edited August 30 by WolfieGlos

[StevieDvd]

16 minutes ago, WolfieGlos said:

.....

That's very interesting.

 

So when I had previously used the l'enhance clip-filter with the DSLR, being a clip-on it is positioned in the camera body directly over the sensor.

With the 2" filters, they are held in a ZWO filter drawer further up the imaging train.

According to the video at 6 mins and on, he explains that the closer the filter is to the sensor, the more reduced the halo will be from the reflections. So this would explain why the halo's are more prevalent, and possibly I've purchased the l'enhance 2" filter for no reason. I suppose the question now, is how can you move the filter closer to the 585's sensor to test this without messing up backfocus!

I suppose another option is to find a better (£££) filter that has better anti-reflective coatings.

Perhaps I should stick to broadband. Or shoot RGB stars, instead of the SCNR/Invert trick with dualband stars.

My take on his setup was that the closer to the sensor the filter is positioned the smaller the halo is - but it's brighter! So he has the filter furthest from the sensor so  that it's so feint it is not visible (or is removal in post processing).

 

 

[Elp]

39 minutes ago, WolfieGlos said:

I wonder if the l'extreme f/2 filter would make a difference.

I've used the standard lextreme at F2 and it works reasonably fine, I don't think it's halo proof though, haven't really tried it near a bright star... (Edit, yes I have with the 294 on Navi when trying IC63, halo for sure).

Didn't try it with the 485 though.

Edited August 30 by Elp

[WolfieGlos]

12 minutes ago, StevieDvd said:

My take on his setup was that the closer to the sensor the filter is positioned the smaller the halo is - but it's brighter! So he has the filter furthest from the sensor so  that it's so feint it is not visible (or is removal in post processing).

Yeah, he kind of explained both scenarios to be fair. What he said for the filter closer to the sensor ties up with my findings, although I'd not necessarily say the halos were brighter. I'll have to look at my data later on and have a look to be sure.

But what I never used to get was the "egg" or doughnut halo around the star that I'm now getting. I don't mind removing a few halos in post, but the sheer number of them in my current work-in-progress will take hours to remove. Annoyingly, some are removed with star removal, others not. It'll probably require more "finesse" to stamp them out than I'm perhaps willing to do.