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Old 12-02-2018, 04:47 PM
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LewisM
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Filter reflections

I believe I am having reflection issuees with my Baader UHC - LP filter. These same issues on brighter stars occured in both the TSA-102 I had, and now the FSQ-85. Without the filter, I do NOT get star flaring/ghosting like this.

My cam is a newer STF-8300C (imported from USA 3 months ago, and working just fine. My old one failed completely after a third SBIG repair, so I gave up on it after spending WAY too much on it). The imaging train is a Baader 2" nosepiece held in a Baader Click Lock, with a Baader 2" UHC filter on the nosepiece and an SVBONY UV/IR cut stacked in front.

I thought the SVBONY being stacked may have been the issue, but removing it has NO effect at all on the flaring. Removing the filters entirely elicits well controlled star profiles.

So, would moving the filter CLOSER to the sensor exacerbate or improve this flaring? I am thinking further away from focus might be better? Or perhaps bringing it nearer focal point?

I have ordered an IDAS LP DI as I believe them to perform better for my OSC applications anyway, but thoughts on this?

Images of concern linked to - look at the ghost/flare on the stars.

https://www.astrobin.com/full/333249/0/?nc=user

https://www.astrobin.com/full/329469/0/

https://www.astrobin.com/full/333248/0/
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  #2  
Old 12-02-2018, 05:33 PM
glend (Glen)
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Lewis, reflections such as those are fairly common when Alnitak is in the shot, and can occur with other cameras as well. There is a thread on CN about it happening with ASI1600 cameras. I have had it happen to my images too. The detectives on the case are pursuing the sensor cover glass as the source of the reflection. Sensor makers are not including anti-reflection coatings on sensor cover glass used in the manufacturing process. A fix is to replace the stock sensor cover glass with something like the Astronomik MC-Clear but few are willing to do that mod as it risks destroying the sensor. ZWO know about the problem but Panasonic is unwilling to spec a new multi coated cover glass due to the limited number of mono sensors they produce. Panasonic is just mentioned in my example because they make the 1600 chips, but 8300 spec sheets that i check show that the cover glass used is not multi-coated.
So it is a sensor cover glass issue imho.

Last edited by glend; 12-02-2018 at 07:10 PM.
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Old 12-02-2018, 05:41 PM
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LewisM
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This is an SBIG 8300 with the Kodak chip, nothing to do with Panasonic. It does NOT have the issue when the LP filter is removed (well nowhere near as evident). Plus it is not just Alnitak as I showed with ETA Carina (see red ghosting top right and mid bottom).

I think there is bouncing light between cover plate and Baader filter
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Old 12-02-2018, 06:37 PM
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Striker (Tony)
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I used to get the exact same halo using all the baader filters Narrowband and LRGB on the bright stars, I then changed to Astrodon it fixed the problem. and I use the ASI16000mm-c
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Old 12-02-2018, 07:17 PM
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LewisM
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That is what I am thinking too Tony.

I ordered the IDAS LPS-DI filter today, so will see if that alleviates this VERY annoying issue. When I used IDAS before with the same camera type and same scope type, NO ghosting whatsoever.

Watch the classifieds for a cheap UHC Should be fine for visual.
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