NB unmouted filters side matters!

GregGurdak
23 Jun, 2018 01:26
I am so surprise that Astrodon selling so expansive filters and saying nothing about the side direction of them , instructions or something … wow … is like buy it and beat it , find out  for yourself …  I wonder if they ever did any Astrophotography?  Looks like Astrodon has no clue what they are selling or how to use it … I lost like 4 hours to find out what is going on ….
I was having problem during flat frames "session " one of my filters act strange one corner was much brighter and few more reflections on the flat frame … so I open filter wheel and check those little "trouble makers" …so find out that one side is more shiny and gives you multiple reflections when you are holding a little screwdriver on the front of it … the other side is more absorbing… almost no reflections…
If one side appears much more shiny than the other, it would be better to have the shiny side opposite the camera to reduce internal reflections from any light leak on the camera side of the filter.  This would be a particular concern when taking dawn flats, where the area around the camera may be well lit with wide band twilight, and the only light for the flat is heavily narrowband filtered.
so check your unmouted filters guys for better results…. clear skies
Starminer68
23 Jun, 2018 01:39
smile Unfortunately, Astrodon was sold and a new owner is running company poorly. I did read a lot of complaints about really dirty (!!!) filters delivered, unresponsive customers service etc. I am changing my filters to Baader Planetarium, very reliable and excellent customer service. Sorry to hear about your troubles. Flipping sides may help, but if the filter surface is uneven (which is totally unacceptable), I advice you to return filters and request for refund, nothing else you could do here.
Edited 23 Jun, 2018 01:40
GregGurdak
23 Jun, 2018 02:18
Adel, can’t say anything bad about the quality, because mine came super clean and well packed… but they should  notice like -" before use you have to find out which side is good for you because we have no clue what we are selling and how to use it " …. then fine, done , I know what I am dealing with , and planing few night for experiments, cool everybody happy smile
Edited 23 Jun, 2018 02:24
morefield
23 Jun, 2018 16:49
The should be a little arrow on the side of the filter that points to the direction of the light path. That’s how I’ve always oriented them anyway.
WesChilton
23 Jun, 2018 23:06
This sounds like user error…
My 31mm unmounted Astrodon filters all have a label around the edge with a little arrow showing the direction to orient them.

Also, most if not all of the complaints about dirty filters were from before Astrodon was sold to the new owner. The new owner is apparently addressing those issues to most people's satisfaction.

There is no question that Astrodon filter are far superior in performance to Baader's. There are many, many threads across the web about reflections and ghosting due to Baader (especially OIII filters). I care much more about performance than customer service in this particular case.
GregGurdak
24 Jun, 2018 22:31
Nope,  No arrow on my labels … even side label are glued different directions on the OIII filter … upside down I mean … like I said you have to buy them with the knowledge how to find right positions…. if you have arrows on your label means that before they were marked but not on the new ones which I have delivered a week ago straight from OPT ….
Edited 24 Jun, 2018 22:35
hbastro
26 Jun, 2018 03:48
Might be true if the antirefeecton side was absorbing but it is not it is antireflecting, distructive interferance. Generaly a BBAR is on one side and a NBPF on the other for Gen 2 filters. This is done to spoil resonance in the filters that causes halos around bright stars. These halos were a major issue with early filters where the NBPF dielectric stack was split between the two sides resulting in a resonant cavity and halos from multiple reflections. Advancements fromTelcom filter deposition methods, IBS and enhanced spinners,  are now used in astro filters as the norm, lucky us.

The BBAR is likely not perfect or a VAR is substituted. In this case there may be additional reflection across the band from the AR coated side. Suggest you do the math, you will be surprised at the result. Likely the filter was not centered in the housing and light was leaking or the edges are not blackned and light is leaking through the filter edges. Are the edges blackened?
Edited 26 Jun, 2018 04:04
GregGurdak
26 Jun, 2018 04:19
Sure they are by Teflon rings provided by ZWO ASI  with filter wheel … can not been wrong housing because the opening is designed right on for 31mm …. when I turned  filter "upside down " problem was solved when I did my flats …. I am not talking about light frames … just the flats where is impossible to do it ( pure flats ) if the filters is placed wrong side ….
Edited 26 Jun, 2018 10:59
hbastro
26 Jun, 2018 04:25
I know a little bit about this… I am glad you found a solution, I understand why it is better and why it is likely not optimal.  Just attempting to help, good luck…

here is a link to Don's website… https://astrodonimaging.com/
Edited 05 Jul, 2018 10:22
morefield
26 Jun, 2018 06:01
I stand corrected on the arrows pointing in the direction of the lightpath - just opened my filter wheel and the Baaders have the arrow.  The Astrodons have a label but no arrow.  That said, this is the first time I've heard the side mattered.
 
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