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Which LRGB Filter set?


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I'm looking to make a start on imaging and considering 1.25" LRGB kits to go with a manual filter wheel.

At the moment I've narrowed it down to a choice of two - the more expensive of the two baader kits and the similarly prices astronomik series II kit (both in the region of around £200 give or take a few quid either side).

Are there any particular benefits of one over the other please?

In time I will probably also add narrowband filters to the mix too but will probably need to get proficient with these in the first instance if that affects the decision in any way.

cheers all...

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I tested this with my Bahtinov mask.  Red, Green and Ha are absolutely bang on with the middle spike crack on in the middle.  With the Blue it is slightly offset from the middle but only very, very small amount.  Maybe I am being to exacting and in fact they are "parfocal enough".

EDIT: This was with the FSQ by the way.  Be interesting to check with my ED80 as well.

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I believe Mr Thomas Baader holds a number of patents for solar films and filter coatings... Could be a pointer ;) Astrodons are great in the advanced narrow-band. I have both brands, full LRGBHaO3S2, and they both perform. Some say the Baader ones are slightly nicer in LRGB. In other words, you cannot go wrong with the Baader set.

Parfocality? That's a myth, regardless of brand...

/per

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It's worth thinking ahead to which narrow band filters you might choose. Recently I bought an Astrodon Ha filter and put it in the filter wheel with my old (but perfectly OK) Astronomik LRGB set and now have an un-anticipated problem.

The Astrodon is 3mm thick compared to the Astronomik 1 mm. Obviously a fairly significant change of focus is required, but the problem I had not thought about was the difficulty of using my OAG. It's simple enough to refocus the imaging scope when moving to the thicker Ha filter, but that throws out the focus of the OAG camera, to the point where guide star images are poorly defined and can cause bad guiding. And of course it's not at all convenient to refocus the OAG camera between filter changes!

So I'm faced with probably having to replace my RGB filters just to get everything at least somewhere nearer parfocal so that the OAG works reliably. A much bigger expense than I had anticipated. :eek: 

Adrian

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I tested this with my Bahtinov mask.  Red, Green and Ha are absolutely bang on with the middle spike crack on in the middle.  With the Blue it is slightly offset from the middle but only very, very small amount.  Maybe I am being to exacting and in fact they are "parfocal enough".

EDIT: This was with the FSQ by the way.  Be interesting to check with my ED80 as well.

The same here. I use Bahtinov Grabber to check and the Blue is ever so slightly off. It's still within what Bahtinov Grabber defines as critical focus, so it's all good. The Baader hydrogen alpha is also near as damn it parfocal with the LRGB set too.

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The same here. I use Bahtinov Grabber to check and the Blue is ever so slightly off. It's still within what Bahtinov Grabber defines as critical focus, so it's all good. The Baader hydrogen alpha is also near as damn it parfocal with the LRGB set too.

Same for me. All spot on except the blue but it's close enough for me. I use a 150P Newt with the Baader MPCC so it could be the coma corrector messing with things.

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Hello

My LRGB set is not parafocal or could it be my Televue Powermate that causes this? It differs about 50 steps between each filter on my focus motor 200 step per round and it is geared down to 1:100. I got the Baader 2458470R/G/B series.

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Thanks for all the useful help and advice - I now have a set of LRGB and Narrowband filters inbound as we speak courtesy of DrRobin of this very parish (although obtained via astrobuysell) - cheers all and doubtless the current clouds will be with us for a while now.  :clouds1:

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It's worth thinking ahead to which narrow band filters you might choose. Recently I bought an Astrodon Ha filter and put it in the filter wheel with my old (but perfectly OK) Astronomik LRGB set and now have an un-anticipated problem.

The Astrodon is 3mm thick compared to the Astronomik 1 mm. Obviously a fairly significant change of focus is required, but the problem I had not thought about was the difficulty of using my OAG. It's simple enough to refocus the imaging scope when moving to the thicker Ha filter, but that throws out the focus of the OAG camera, to the point where guide star images are poorly defined and can cause bad guiding. And of course it's not at all convenient to refocus the OAG camera between filter changes!

So I'm faced with probably having to replace my RGB filters just to get everything at least somewhere nearer parfocal so that the OAG works reliably. A much bigger expense than I had anticipated. :eek: 

Adrian

How do you figure that? The OAG is in front of the filters usually. Isn't your's?

/per

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How do you figure that? The OAG is in front of the filters usually. Isn't your's?

 

/per

Not sure I understand, Per. It's a QSI wsg camera, so the filters are up close to the sensor and the OAG sees the unfiltered incoming light before it reaches the filters. That means that the OAG camera can only be in focus at one position of the focuser draw-tube ...... but I need to use two different focuser positions with the different filters for the imaging camera. So when I rack out the focuser to refocus after changing filter, the OAG camera moves too and so goes out of focus.

Adrian

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