Help needed with filter setup for reducer/camera

[sneaks]

Hello. I have pretty much decided to get an optolong enhance or extreme, with a preference for the extreme. The extreme only comes in 2".

Below are images of my reducer, including a screenshot of the product description. I don't see how to attach the filter to this?

https://flic.kr/s/aHsmTXNBFv

The M48 thread is apparently 2" (48mm equals 2" huh?!?), but if I screw a filter to the T-ring, that will ruin my back focus right?

There are some threads INSIDE the reducer behind the lens, but I have no idea what type or size. And the only access to those is through the T-ring adapter hole in the end which is NARROWER. So the filter won't fit in that way - if it even would have.
Or am I supposed to remove the end piece, thread a filter in, and put the end piece back on...?

As you can see, I'm not sure what to do here.
A clip in is possible, but they are more expensive again, and only available for the enhance.

Maybe I'm missing something obvious here, but your help is much appreciated. :)

[Merlin66]

According to the info on the Agena site, a 2" (48mm) filter can be fitted into the reducer...
https://agenaastro.com/sharpstar-61mm-f-5-5-ed-triplet-apo-refractor-telescope-with-0-8x-reducer-flattener.html

[sneaks]

"The reducer also includes a female M48x0.75 thread for attaching a filter"

Oh nice find, thanks.
So I guess that thread inside the rear of the reducer is the one it is talking about, meaning the end is designed to be removed for this purpose. Seems a bit fiddly, but if it works I'll be happy.
Appreciate it!

[The_bluester]

Just remember that if you fit a filter in between the lens set of the reducer and the camera sensor it will slightly increase the required physical back spacing to the camera. You might need to fit a spacer washer between the reducer and T ring adapter.

The general rule I have seen bandied about is one third of the thickness of the filter glass.

[sneaks]

Huh... more gotchas. Thanks for the warning.

[TareqPhoto]

Good tips, maybe i have to think about this if i place filters to reducers flatteners and correctors for example, something i thought that it doesn't matter because it will count distance from the reducer/flatCorr glass and not from the filter mounted on them.

[The_bluester]

It depends where the filter is placed.

I have a filter in between my flattener and camera at the moment and it made a small difference to the focus point, and the images suggest that my corrector to camera distance is no longer quite correct.

I did a similar thing a year ago with a borrowed scope, that one had a filter thread in front of the corrector (between the corrector and the objective) and all that required was a slight change to the focuser position to achieve focus.

[TareqPhoto]

Ok, that will need experiment then, i will do that with my Newt first, and with my awaiting new scope, hope i will make it right.

[The_bluester]

Basically, a filter added anywhere in between a corrector that needs a specific spacing, and camera will increase how much physical spacing you need. A filter before a corrector you can generally just change the focuser position a little.

[ChrisV]

Agree, the filter between the reducer and camera will muck up the spacing and affect the image. But I suppose depends on the tolerance of your reducer?

Safer to put the filter on the telescope side of the reducer. But is 2" big enough at that distance and your focal ratio - I dunno ...

[Merlin66]

Getting an adaptor to suit a 48mm filter which fits the front of the reducer may be an issue.

[NewBee101]

Hi Guys, I am in similar situation with filters, my focal reducer for my Saxon 127 arrived awhile back I had to order some extra adaptors for it they have just turned up. My situation is that I have reached the max back focus with just the tee ring on my camera (DSLR) to the focal reducer, now the only spot for filters is at the frount of the focal red buy screwing it into the nose piece or using a filter draw in which case will depend on overall focus, I would rather use the filter draw it would save altering the camera position when I want to change a filter.
After reading through the other posts, would it be fair to say there does not seem to be a hard and fast rule in where to place the filters anyway, focus is the important part of the equation.

[RyanJones]

Just to add another piece to the puzzle. If you have a fast ratio telescope then the angle of incidence of light arriving at the filter can reflect instead of passing through. In this case the filter is better placed between the corrector and the sensor once the light path has been altered to a lower angle or incidence.

Cheers

Ryan

[Merlin66]

Ryan,
After a reducer the field angle is actually increased.
It is reduced after a barlow.....

[RyanJones]

I was referring to coma corrector or field flatterers. I was under the impression that they straightened the path of the rays. Happy to be corrected if I’m wrong though.

[Merlin66]

The original OP mentions the reducer.....hence my comment.