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ASI533 Bright Star Pattern in M45

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#1 Rab722

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Posted 23 September 2020 - 04:49 PM

I have noticed when a very bright star in my field a pattern from the camera will show up. In the image the brightest stars in M45 have a pattern around the star. What causes this and how can it be avoided or fixed.

 

The equipment is WO FLT110 and ZWO ASI533MC. Image 63 subs of 180 seconds and 0 gain with only BackgroundNeutralization and AutomaticBackgroundExtraction.

M45 Brightest Stars.jpg


Edited by Rab722, 23 September 2020 - 04:52 PM.


#2 SDTopensied

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Posted 23 September 2020 - 04:56 PM

Internal reflection in the camera.  It’s a ZWO thing.

 

-Steve



#3 RogeZ

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Posted 23 September 2020 - 05:04 PM

Any data to back that up?

#4 sharkmelley

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Posted 23 September 2020 - 05:19 PM

Internal reflection in the camera.  It’s a ZWO thing.

No. 

It's microlens diffraction.  It's a sensor thing.

 

Mark


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#5 Rab722

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Posted 23 September 2020 - 05:26 PM

Are there any filters that would help? I already have the camera at zero gain.  If it's microlens diffraction then reducing the exposure I think would not help because the pattern is still there but at a lower level and would just show up again as I stretch the image to show the nebulosity.

 

Rick



#6 sn2006gy

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Posted 23 September 2020 - 05:49 PM

Are you using a uv/ir filter? I’ve used the 533 and never saw this and I use the 2600 and don’t see this.

This is a bright target though. Maybe use shorter subs. You will blow out any camera here if not careful.

#7 sn2006gy

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Posted 23 September 2020 - 05:55 PM

The 533 does not have a treated window

Edited by sn2006gy, 23 September 2020 - 05:55 PM.


#8 sharkmelley

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Posted 23 September 2020 - 05:57 PM

Are you using a uv/ir filter? I’ve used the 533 and never saw this and I use the 2600 and don’t see this.

Very good point!  An IR/UV blocking filter might fix the problem. 

See this comparison for example:

https://www.cloudyni...sct/?p=10406677

 

Mark


Edited by sharkmelley, 23 September 2020 - 06:14 PM.


#9 Rab722

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Posted 23 September 2020 - 08:32 PM

Ordered the L-2 IR/UV blocking filter. Hope it helps.

 

Rick


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#10 telfish

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Posted 23 September 2020 - 08:46 PM

What scope are you using, This looks like the Iron Cross seen in some WO and other small refractors.


Edited by telfish, 23 September 2020 - 08:46 PM.


#11 sn2006gy

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Posted 23 September 2020 - 09:19 PM

Ordered the L-2 IR/UV blocking filter. Hope it helps.

 

Rick

When i used my 533, i ran the optolong uv-ir with great success.



#12 Rab722

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Posted 23 September 2020 - 09:36 PM

Scope is WO flt110 6.5 with TEC optics. I've seen the same pattern with my C8.

 

Rick



#13 don314

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Posted 23 September 2020 - 10:10 PM

Its a reflection off the microlens on the sensor.  This has been discussed on several posts, but the final answer (IMO, as these guys have degrees in math and optics) is at this post:

 

https://www.cloudyni...d/#entry8877448

 

It starts out with someone stating what they think it is, but starting at post 12 and going to post 24, they develop the math behind it, and even post a script you can download that has the math behind it.  



#14 sharkmelley

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Posted 23 September 2020 - 11:48 PM

It starts out with someone stating what they think it is, but starting at post 12 and going to post 24, they develop the math behind it, and even post a script you can download that has the math behind it.  

The PixInsight script is in this post.

An exercise for any interested reader is to convert it to Python.

 

Mark


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#15 sn2006gy

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Posted 24 September 2020 - 07:23 AM

It starts out with someone stating what they think it is, but starting at post 12 and going to post 24, they develop the math behind it, and even post a script you can download that has the math behind it.

It’s someone not using a uv ir filter. The 533 window is not treated.

I respect the math and those with degrees in optics.

This camera has had a pretty big shake down here before with tons of phots. I have experience with the sensor and never had this issue running it behind an Optolong uv ir, Optolong l-enhance or Optolong l-pro.

I don’t see these issues with bright stars on the 2600 either. The 2600 does have a treated window and I typically run a triad there. 2600 is the aps-c big brother.

Sadr had halos with the l-enhance but that star does halos for just about everyone. Certainly wasn’t the blocky reflective kind of halo though.

Once weather clears up I’ll give this region a try

Edited by sn2006gy, 24 September 2020 - 07:24 AM.


#16 sharkmelley

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Posted 24 September 2020 - 07:38 AM

The 533 window is not treated.

Do you have a reference for that information?  It surprises me because an untreated coverslip would be expected to reflect around 4% of visible light and it wouldn't make sense for any sensor manufacturer to risk that. 

 

Mark


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#17 sn2006gy

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Posted 24 September 2020 - 07:51 AM

Do you have a reference for that information?  It surprises me because an untreated coverslip would be expected to reflect around 4% of visible light and it wouldn't make sense for any sensor manufacturer to risk that. 

 

Mark

It is rather unfortunate they don't treat it. I have no idea why - maybe they had inventory they needed to burn??

 

The docs for the 533 say "Protective Window:  AR"

 

while the docs for the 2600 and 6200 say "Protective Window: IR Cut"

 

Beyond that, I don't have much more detail other than what was confirmed in the 533 megathreads where running without a filter does cause massive bloated stars and "blow out" of bright objects... not sure there is a better term :)


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#18 sharkmelley

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Posted 24 September 2020 - 10:04 AM

It is rather unfortunate they don't treat it. I have no idea why - maybe they had inventory they needed to burn??

 

The docs for the 533 say "Protective Window:  AR"

 

while the docs for the 2600 and 6200 say "Protective Window: IR Cut"

AR means anti-reflective

It means the glass used for the ASI533 protective window is treated with anti-reflective coatings.

 

Mark



#19 sn2006gy

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Posted 24 September 2020 - 10:32 AM

AR means anti-reflective

It means the glass used for the ASI533 protective window is treated with anti-reflective coatings.

 

Mark

If you run a UV-IR filters the stars come out fine. 

 

I don't have either issue on the big brother 2600 sensor... i don't have a 6200 to try myself, but what I see of my friends images they're not getting this issue either (MM or MC version). Similar sensor tech just larger format(s).

 

The manuals were recently revised  but I'm not entirely sure they 100% true. In the 1.0 manual for the 2600 i don't think it mentioned coating(s) so we talked about it extensively here until there was clarity. The 1.1 update says IR Cut now.

 

It's my NON EXPERT "what I read" view that an IR cut is REQUIRED on an OSC color camera because the sensor is overly sensitive IR which shows up as not only color (say in a pinkish hue for planets) but also it shows up as prismatic atmospheric dispersion aberrations.

 

I could be wrong about the science, but i've used the 533 and didn't have bad stars for reasons other than when my scope was poorly configured. I'm a computer nerd by day.

 

WHy are so many people so quick to judge ZWO on product quality these days?



#20 wxcloud

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Posted 24 September 2020 - 11:09 AM

I ended up getting some orbs in my m45 image with my ZenithStar 61, flattener and l-pro attached inside the flattener. Looks like reflections or flare to me. Haven't decided if it was filter, the flattener or just distance (it's a bit aways from the sensor).

Kind of sounds like I'll need to swap it out for an ir filter? Or maybe pop my filter wheel on and use the clear L filter in my zwo lrgb set? I kinda think I goofed picking up a broad band light pollution filter...

#21 sn2006gy

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Posted 24 September 2020 - 11:19 AM

I ended up getting some orbs in my m45 image with my ZenithStar 61, flattener and l-pro attached inside the flattener. Looks like reflections or flare to me. Haven't decided if it was filter, the flattener or just distance (it's a bit aways from the sensor).

Kind of sounds like I'll need to swap it out for an ir filter? Or maybe pop my filter wheel on and use the clear L filter in my zwo lrgb set? I kinda think I goofed picking up a broad band light pollution filter...

I used an L-PRO on my 533 on an Orion ED80 and an Esprit 120 and had no problems with that filter. The L-PRO has UV/IR Cut.

 

The clear L filter should UV/IR cut as well if you want to try that.

 

A quick search in astrobin and i see diffraction spikes and aberrations with ZenithStar 61 - lots of "chonky" stars when the stars are super bright.



#22 wxcloud

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Posted 24 September 2020 - 06:07 PM

I used an L-PRO on my 533 on an Orion ED80 and an Esprit 120 and had no problems with that filter. The L-PRO has UV/IR Cut.

The clear L filter should UV/IR cut as well if you want to try that.

A quick search in astrobin and i see diffraction spikes and aberrations with ZenithStar 61 - lots of "chonky" stars when the stars are super bright.


Hmmm... Maybe I should leave the filter in for a while. Kind of don't want to mess with things. Yeah I noticed some rasa-esqe stars when trying m45. Not horrible but kind of head scratchy.

#23 Rab722

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Posted 11 October 2020 - 04:40 PM

Ok, I got the Astronomik UV-IR Block L-2 filter and tried M45 again last night. Made some other changes I think helped with this bright target.

 

First attempt:

No Filter

180s exposure

0 gain

about 60 minutes total

 

Second Attempt:

L-2 Filter

60s exposure

0 gain

about 60 minutes total

Dither after every frame.

 

I'm happier with this attempt. Also think I will now dither after every frame to help with drizzle integration. Thanks for the ideas.M45 L2.jpg

 

Rick


Edited by Rab722, 11 October 2020 - 04:43 PM.

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