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Old 18-12-2019, 11:45 PM
HeavyT
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Where to place 2 inch filter in imaging train?

Hi all

I'm trying to work out my imaging train after collecting a reducer and oag recently. Haven't had great skies to work this out.

Tonight I screwed my trusty UHCS 2 inch filter on to the dslr t adapter, then screwed the reducer on to the filter, and the reducer on to the focussed. I have other connectors on the way to bring the oag into the train.

I didn't get much time in as cloud moved in to stay. But I noticed the filter glass is loose now. When I squeeze the metal ring, it stops moving. It's also rather hot lately.

Anyway, I had been concerned about hanging all that weight off of the filter, but have no other way to bring it in to the train until the new connectors arrive. In my previous imaging session I had the filter between the reducer and oag, which in turn was t mounted to the dslr. This of course had the reducer way too far from the sensor so my dso entered hyperspace.

Should I discontinue placing all that weight on the filter and just wait for the connectors?

Ultimately for dslr imaging I intend to have a t piece connecting the oag to the scope using the "push in" method, so there won't be any weight hanging off of the filter.

Thanks and clear skies
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Old 19-12-2019, 12:09 AM
Xeteth (David)
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My light pollution filter screws on to the front of my field flattener, which is then inserted into the end of the scope and clamped. Is this possible in your setup? (Ie. It screws on to the front of your focal reducer). This also means it won't affect your back focus.
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Old 19-12-2019, 06:40 AM
HeavyT
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Thanks mate, yes I'd like to get mine in front too, and it looks like I'll have to buy a third t ring (M48 this time) to achieve the correct backfocus for the flattener. Naturally, the reducer/flattener also is threaded M55 - so not getting an M48 filter onto that

My focusser thread is M55, so I have an M55-M42 adapter on the way which will allow connection to the OAG, then I'll screw an M42-M48 adapter on to that to push it in to the plastic eyepiece holder that is usually screwed on to the focusser - which sounds the same as what you're doing?


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Originally Posted by Xeteth View Post
My light pollution filter screws on to the front of my field flattener, which is then inserted into the end of the scope and clamped. Is this possible in your setup? (Ie. It screws on to the front of your focal reducer). This also means it won't affect your back focus.
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Old 19-12-2019, 06:46 AM
Imme (Jon)
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If at all possible always screw your connections
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Old 19-12-2019, 07:21 AM
HeavyT
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Yep I hear you, but do you know if filters are designed to handle the weight of the camera, reducer etc?


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If at all possible always screw your connections
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Old 19-12-2019, 07:50 AM
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The_bluester (Paul)
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If it is anything like the M48 filter I use then no, they are often designed so you could stack filters but my ZWO M48 filter has about 1mm of female thread before you hit the lock ring, when I first tried it out I had my OAG and camera hanging off it but it was a tense sort of night hanging a kilo or more of 1 turn of thread. Once I was sure it was going to work I had the adapter that fits my reducer to the focuser drawtube remachined to put the filter in front of the reducer inside the drawtube.
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Old 19-12-2019, 08:32 AM
HeavyT
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OK thanks mate, think I'd better just try unfiltered for awhile until I can get the oag on the front of the reducer, then I can screw a t adapter on the front of the oag, and push it in the draw tube.

Good excuse to see how long an exposure I can manage in Bortle 5 without light pollution blowing everything out. When i started 6 months ago, I was doing 30s subs unfiltered. Been using the UHCS exclusively for about 4 months, so it will be nice to have proper star colours again at least.

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Originally Posted by The_bluester View Post
If it is anything like the M48 filter I use then no, they are often designed so you could stack filters but my ZWO M48 filter has about 1mm of female thread before you hit the lock ring, when I first tried it out I had my OAG and camera hanging off it but it was a tense sort of night hanging a kilo or more of 1 turn of thread. Once I was sure it was going to work I had the adapter that fits my reducer to the focuser drawtube remachined to put the filter in front of the reducer inside the drawtube.
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