Baader Maxbright

[bosun21]

I have just ordered a new Baader Maxbright II binoviewer and was wondering which corrector to get for it. I was thinking the 1.7x purely for the magnification purposes. With me using a 1.7x corrector is it still desirable for me to attach a separate prism/ mirror diagonal directly to the T2  connection on the Maxbright? to shorten the light path? I had no clue of these complexities.

[Franklin]

I've got the older Baader Maxbrights (not II) and use them with the 1.7x GPC and 32mm prism diagonal. They all come to focus well with my refractors in this configuration.

[bosun21]

18 minutes ago, Franklin said:

I've got the older Baader Maxbrights (not II) and use them with the 1.7x GPC and 32mm prism diagonal. They all come to focus well with my refractors in this configuration.

Thanks. That’s what I wanted to hear as I bought it primarily for my 102 f7. Have you directly attached the prism diagonal by means of the T2 connection? This may sound like a silly question but where have you inserted the GPC? I think you can tell that these will be my first binoviewers.

[josefk]

Hi @bosun21 i only got binoviewers myself last week so i'm a complete newbie BUT the math is fresh in mind :-). Do you know the backfocus (in-focus) for your scope?

The MBII alone (not considering any diagonal) requires 110mm without GPC, 92mm nominally with 1.25x GPC and 77mm with 1.7x GPC.

I have 270mm back focus. My focuser takes 107mm and the T2 diagonal takes 38mm (145mm sum) plus MBII at 110mm is 255mm and that is less than 270mm so it comes to focus with about 15mm of draw tube extension.

I also have a 1.7x GPC on order. The sum will then be 107mm plus 38mm plus 77mm so not only will it come to focus it will come to focus in a similar draw tube range to a mono eyepiece in my set up (107mm focuser and 110mm diagonal in my case).

Hope that helps rather than hinders.

Cheers

 

[bosun21]

4 minutes ago, josefk said:

Hi @bosun21 i only got binoviewers myself last week so i'm a complete newbie BUT the math is fresh in mind :-). Do you know the backfocus (in-focus) for your scope?

The MBII alone (not considering any diagonal) requires 110mm without GPC, 92mm nominally with 1.25x GPC and 77mm with 1.7x GPC.

I have 270mm back focus. My focuser takes 107mm and the T2 diagonal takes 38mm (145mm sum) plus MBII at 110mm is 255mm and that is less than 270mm so it comes to focus with about 15mm of draw tube extension.

I also have a 1.7x GPC on order. The sum will then be 107mm plus 38mm plus 77mm so not only will it come to focus it will come to focus in a similar draw tube range to a mono eyepiece in my set up (107mm focuser and 110mm diagonal in my case).

Hope that helps rather than hinders.

Cheers

 

Thanks for your findings with the MBII. How do I find the back focus for my telescope? It’s a Starfield 102 f7. I am also going to attach a Baader prism diagonal by means of the T2 connection.

[josefk]

5 minutes ago, bosun21 said:

Thanks for your findings with the MBII. How do I find the back focus for my telescope? It’s a Starfield 102 f7. I am also going to attach a Baader prism diagonal by means of the T2 connection.

...well for an important item of OTA spec it seems not to be always declared in the user manual/datasheet. For my scope i found a drawing of my scope online for the 270mm number (i think on cloudy nights) and i found the focuser spec (the 107mm number) in another drawing online. I'm afraid i don't know your scope but perhaps google it or someone helpful on here will chip in. Just be sure to be clear on whether the number "whatever it is" applies after the focuser or before it so you can do the maths above. Good luck.

[Franklin]

2 hours ago, bosun21 said:

Thanks. That’s what I wanted to hear as I bought it primarily for my 102 f7. Have you directly attached the prism diagonal by means of the T2 connection? This may sound like a silly question but where have you inserted the GPC? I think you can tell that these will be my first binoviewers.

The GPC screws into the top of the Baader 32mm prism (no eyepiece holder) and then the Maxbrights screw directly via T2 onto the diagonal. At the other end of the diagonal either a 1.25" or 2" nosepiece (recommend 2" for stability). It is also possible to fit the GPC into the nosepiece of the diagonal rather than immediately before the binos. This will increase their magnification factor, by what amount I do not know, in fact I did contact Baader regards this and they didn't know off hand but suggested counting roof tiles to determine the increase which is on my "to do" list as we speak. Maxbright II, nice binos!

[Ricochet]

5 hours ago, bosun21 said:

How do I find the back focus for my telescope?

Focus on a star with an eyepiece you plan on using with the binoviewer. Read the number off the scale printed on the focuser. If you are using a different diagonal to the one you will be using with the binoviewer you will need to take the difference in their light paths into account. Compare that number to the table in the maxbright 2 manual.