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Nikolas74

Astrodon 36mm...which side to camera ?

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Anyone knows which is the correct side to face the camera when using 36mm Astrodon filters ?

I don't see any indicators...

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I have Baader filters which have an arrow on the side but I am sure I have seen other threads saying it doesn't matter with Astrodons, hopefully someone else will confirm this.

From reading many threads the majority of opinion says that of one side is shiney, like a mirror, then that points towards the direction of incoming light, that is the scope side. But oddly enough on the Baader website I read that this was true unless you had a flattener, or reducer in the optical train and then you may have to reverse them so the shiney side points towards the camera.

I did ask whether other members followed this rule in a thread but didn't get a firm reply.

Steve

Edited by teoria_del_big_bang

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1 hour ago, teoria_del_big_bang said:

From reading many threads the majority of opinion says that of one side is shiney, like a mirror, then that points towards the direction of incoming light, that is the scope side. But oddly enough on the Baader website I read that this was true unless you had a flattener, or reducer in the optical train and then you reverse them so the shiney side points towards the camera.

Could you please point us to a link (reversing Baader filters) where this information is posted?  Otherwise it means that 99% of all imagers have been doing it wrong for many years (including myself), as practically every optical system requires a flattener or reducer for imaging ;)

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6 minutes ago, Uranium235 said:

Could you please point us to a link (reversing Baader filters) where this information is posted?  Otherwise it means that 99% of all imagers have been doing it wrong for many years (including myself), as practically every optical system requires a flattener or reducer for imaging ;)

unmounted-filters-which-side-should-face-the-telescope

The website states:

Always put the more reflective side towards the telescope side. On these filters were the position matters. This arrow indicates which face of the filter should be directed towards the sky (telescope-sided). All cell-mounted filters are already oriented in a way that the most appropriate filter face is facing the sky when the filter would be mounted directly on the front end of the nosepiece of a camera. 
If you mount your filter the other way, any reflected light would have a short to the camera sensor, resulting in a higher risk of getting some kind of back-reflections inside the camera field. Many sensors have highly reflective areas near the light sensitive area.

But:  this is true only for instruments without optical elements near the focal plane. If you have a coma corrector, field flattener, focal reducer, focal extender (to a lower degree due to concave surface), or in extreme cases a whole lens group for more complex field corrections a few centimeters in front of the filter it could be useful to flip the filter against the rule from above (thus having the arrow pointing away from the telescope). Cause in such cases the likelihood of reflections from the sensor could be better then fort and reflections from such glass-surfaces. If in doubt, it helps to make some test images from a star field with bright stars, using the filter in both ways for comparison.

 

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In the end I too have the arrows pointing to the telescope, as this is what other people seemed to do, and also it is a bit vague saying a few centimeters in front of the filter rather than specifying any distance.

My thoughts being if I got halos then I would then try to reverse them and so far I do not seem to have suffered with them.

Steve

Edited by teoria_del_big_bang

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Follow the reflection on the filters, if there is spacing or kind of double reflection or ghosting then this is the telescope side, i think i also saw another link where it shows the reflections of those unmounted to tell which side to use.

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2 hours ago, Nikolas74 said:

Anyone knows which is the correct side to face the camera when using 36mm Astrodon filters ?

I don't see any indicators...

Astrodon are a level above Baader and so while the baader filters have an anti-reflection coating on only one side the Astrodons have the coating on both sides. Hence it should not make a difference. However, having said this in their mounted filters the shiny side is facing the scope assuming your filter wheel screws in from the scope side.

Adam

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I asked the vendor this question when my unmounted Astrodons arrived..  the response was that it doesn't matter

Dave

Edited by Laurin Dave

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3 hours ago, Uranium235 said:

Could you please point us to a link (reversing Baader filters) where this information is posted?  Otherwise it means that 99% of all imagers have been doing it wrong for many years (including myself), as practically every optical system requires a flattener or reducer for imaging ;)

Well, you learn something every day!

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I have read too about the Baader filters.....with the Astrodon's both sides look exactly the same , that's why i posted the question in case someone else experienced the same dilemma....

Anyway i will make my tests and see the result....

Thank you all 😀

  • Thanks 1

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6 hours ago, Tim said:

Well, you learn something every day!

Well I haven't 🙂 

As a novice I was looking on line for an answer to which way round they went and found this link

unmounted-filters-which-side-should-face-the-telescope

And as it had the Baader name attached to it thought that was Gospel but also searched a little more and found nobody else adhered to this odd rule so went with the flow and mounted as normal with arrows pointing towards the scope.

As I said as far as I can see I do not have issues although being relatively new to all this do not see as many issues as some more experienced imagers do.

The reasoning for the shiny side being towards the telescope I understand but what it says in the link just confused me really.

Steve

 

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9 minutes ago, Nikolas74 said:

I have read too about the Baader filters.....with the Astrodon's both sides look exactly the same , that's why i posted the question in case someone else experienced the same dilemma....

Anyway i will make my tests and see the result....

Thank you all 😀

Yes I thought the Astrodons were pretty clear cut in that it did not matter. And I guess from how people praise them they are head and shoulders above other filters and maybe worth the extra money just to stop the confusion I had have 🙂 

Steve

Edited by teoria_del_big_bang
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Hmmm interesting reading! I guess this could (in theory) apply to mounted filters since it takes little effort to remove one from its cell and flip it over. Might be something worth trying if you are getting large halos on your particular setup - I wonder if this applies to narrowband filters? (probably not, but its worth asking)

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Just a follow up since my two posts seems to connect to each other....

Here you can see my post about FLATS Problem , maybe somehow its related to filter wrong side placement . the topic is here :

 

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So i experimented by flipping the filter sides....

In the photo REFLECTION is the Oiii lets say A side

In the photo REFLECTION 2 is the Oiii lets say B side

What you think ????

Which photo has more info ?

Why the pattern/gradient changed ?

Which one is the correct side ?

REFLECTION.jpg

REFLECTION 2.jpg

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