Hi ! I am new to this group and this is my first question (there might be others to come !)

I am a bit confused about the use of my Meade F/D 3.3 focal reducer and the effective reducing factor.  I have read many post and other stuff like the instruction sheet that came with it.

I have an old LX-50, 10 inches and my camera is a DSI Pro I (I am waiting for a DSI Pro II at the moment)  I have read some post regarding the effective reduction that I have with this reducer and it doesn't give the same data that the instruction sheet.  I do understand that the slide bar of the DSI pro contribute to add some distance between the reducer and the DSI chips itself. I do undertand also that this change the effective focal reduction.

 

So here's the question :

What is the effective reduction when I use the reducer only with the T-adapter directly onto the reducer, leaving the 15mm and the 30mm extension out of the configuration, the slide bar would then be the only contribution to the distance between the ccd chips and the focal reducer ?

What is the effective reduction if I add the 15mm extension to this set up ?

What is the effective reduction if I add the 30mm extension and only this one ?

Can I use both extension (the 15 and the 30mm) ? If so, what is the effective reduction  of this set up?

What is the maximal reduction can be use without having some distorsion on the picture ?

I also have the 6.3 focal reducer, I have stack the 6.3 and the 3.3 reducer and was able to almost catch the entire first quarter of the moon on the computer screen with my Meade LX-50 10 inches. Does this set up is usable (it seems that the perfect focus was hard to obtain but that wasn't that bad) and what is the effective focal reduction of both reducer stack one to another ?

I hope this will also help newbie to ccd like myself :)

Guy Campeau wrote:

Hi ! I am new to this group and this is my first question (there might be others to come !)

==> Welcome aboard, and ask away :-)

I am a bit confused about the use of my Meade F/D 3.3 focal reducer and the effective reducing factor.  I have read many post and other stuff like the instruction sheet that came with it.

I have an old LX-50, 10 inches and my camera is a DSI Pro I (I am waiting for a DSI Pro II at the moment)  I have read some post regarding the effective reduction that I have with this reducer and it doesn't give the same data that the instruction sheet.  I do understand that the slide bar of the DSI pro contribute to add some distance between the reducer and the DSI chips itself. I do undertand also that this change the effective focal reduction.

==> I started with the same setup (only on LX200 mount). you can do great images with this!

So here's the question :

What is the effective reduction when I use the reducer only with the T-adapter directly onto the reducer, leaving the 15mm and the 30mm extension out of the configuration, the slide bar would then be the only contribution to the distance between the ccd chips and the focal reducer ?

==> .5x (~F5)

What is the effective reduction if I add the 15mm extension to this set up ?

==> .33x (~F3.3)

What is the effective reduction if I add the 30mm extension and only this one ?

==> .3x (~F3.0) ==> Not recommended!

Can I use both extension (the 15 and the 30mm) ?

==> No

If so, what is the effective reduction  of this set up?

==> "too much" ;-)

What is the maximal reduction can be use without having some distorsion on the picture ?

==> F3.3 with the Pro, F5 with the Pro-II

I also have the 6.3 focal reducer, I have stack the 6.3 and the 3.3 reducer and was able to almost catch the entire first quarter of the moon on the computer screen with my Meade LX-50 10 inches. Does this set up is usable (it seems that the perfect focus was hard to obtain but that wasn't that bad) and what is the effective focal reduction of both reducer stack one to another ?

==> I used it some that way...it never seemed "quite right" to me. No idea what the reduction factor is.

I hope this will also help newbie to ccd like myself :)

==> I hope so too - good luck!

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Chuck Reese
CDIP Certified: Nebula, Galaxy, Solar System, Stars & Clusters Imager
CDIP Mentor: Nebulae & Solar System Categories
For information on the Certified DSI Imager Program, see:
http://autostarsuite.net/forums/1427/ShowForum.aspx

Thanks so much Chuck for this quick answer (and clear also)

I have just discover (on another thread) that the IR filter has to be used in conjunction with the RGB filter.  Before this discovery (for me), I was imaging this way, L, R, G, and B.  without the nose piece, the DSI was directly attach to the T-adapter with the 15mm extension into the focal reducer.  The IR filter wasn't used with the R_G_B images. As you must have seen before, the IR Filter was inserted into the slide bar like the other three, which now I understand was a mistake. Now I understand that this has to be this way, L, L+R, L+G, L+B.

To get this, I now know that I have to put the IR filter on the nosepiece of the DSI, then, insert the DSI pro nosepiece into the 1,25 eyepiece holder, without the diagonal. This setup change again the effective focal reduction of the Focal reducer F/D 3.3

The instruction sheet of the focal reducer is telling that this setup would give a F/3 effective focal reduction, but I know that the DSI Pro has a slide bar holder that change all this.  With the addition of the additional space caused by the slide bar, what happen to my effective focal reduction. If I do understand right, the extra space would reduce more the effective focal ratio, which is already at F/3, giving me an even faster system than F/D = 3, which is not recommanded if I am right. 

So I am wondering why do I have to have this focal reducer if not usable with the DSI Pro?

In other word, did I make another mistake when I bought this focal reducer, was it compatible with the DSI pro ?

To be more straight to the point, how does the focal reducer F/D 3.3 has to be used with a DSI Pro or a Pro II in conjunction with the filter bar and LRGB imaging ?

Hi, Guy

I recommend you use a 3rd party IR filter, such as the Baader UV/IR cut filter. Buy it in 1.25", and get a TF Filter adapter from the Webcaddy site (Steve Mogg's site in Australia). Leave the Meade IR iun the filter bar so all 4 filters are parfocal, and using the TF filter holder, but the new IR filter on top of the bar, under the T-thread extension tube or adapter. This adds no distance to the setup at all.

The other way of course is to get a 2" IR filter, and place it in the 2" barrel in front of the reducer. Again, no change in distance.

I have used both of these methods, and both work well for me.

Chuck

---

Chuck Reese
CDIP Certified: Nebula, Galaxy, Solar System, Stars & Clusters Imager
CDIP Mentor: Nebulae & Solar System Categories
For information on the Certified DSI Imager Program, see:
http://autostarsuite.net/forums/1427/ShowForum.aspx

Thanks again Chuck, I'll go this way,