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#1 sberrada


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Posted 14 December 2013 - 04:04 PM


I would appreciate any comments from users of the BORG 125SD for astrophotography.

I have 3 refractors that I am quite happy with: ES102, WO GTF81, AT 65Q; all are APO triplets that perform very well.

I am however looking for a refractor that would have a faster F-stop, and also be very portable for travel.

My key questions are:
- I understand that the BORG is a doublet; how does it perform for astrophotography (are stars very sharp with no color issues); is there any data on performance (star size etc)
- There are several reducers for the BORG125SD - F3.9, F5.1, F6; I am thinking of F5.1 because I need the extra focal length (vs F3.9)
- There is a feathertouch focuser and helical focuser; any recommendations ?

I would appreciate any experience and recommendations as this is a big investment; alternative ideas for telescopes meeting same objectives would be great.


#2 skullpin



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Posted 14 December 2013 - 05:23 PM

I have this scope, though I use it visially. Perhaps I could still be of some use:

1. Some data on optical performance here: http://www.sciencece...125sd/index.htm

2. The feathertouch is nice for visual use, greater travel and faster to rack in and out. I also have the helical, which in some ways I believe would be better for photography: very fine adjustments, scale for repeatable focus, and stable focus (an accidental bump or extra weight will not shift focus whatsoever). The negative on the helical is that it has no option for motorizing.

Visually, I love the scope. Manually, it handles so nicely as it weighs so little and is very compact.


#3 Paulimer


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Posted 14 December 2013 - 09:19 PM

See my other thread:

The image speaks for itself, with the TS2.5" flattener. I did not have the F/5 reducer so I can't comment on that, and I haven't tried the F4.2 reducer as well.

I've custom ordered the moonlite focuser for it, and I think Hutech can provide all the necessary adaptations. Nothing to complain about. I might someday get the helical focuser just for the light weight though.


#4 fetoma



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Posted 15 December 2013 - 05:23 PM

David Rosenthal images with one. Check out his posts.


#5 MooEy



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Posted 15 December 2013 - 09:20 PM

I have one and liked it alot. I have both the 0.85x(7887) and the 0.66x(7704) reducer. I'm mostly using the 7704 reducer and it works pretty well on the st-8300m.

You will want both focuser, the 7835 and the ftf-m57 focuser. The 7835 is a lightweight helical focuser which works very well for those grab and go sessions. The ftf-m57 is heavier and works well for imaging.

If you have intention of getting the 0.66x(7704) reducer, avoid any other focusers, the 7704 comes in 2 parts and must be used with either 7835/ftf-m57.

I bought mine with the shorter tube. With the drawtube and focuser removed, it measures 22" or so. It fits into one of those 24" padded bags, allowing you to bring a big 5" refractor for travelling.

Overall the scope is very light, on the sxd mount, I could balance it with just a piece of 1.9kg counterweight, all the way up. For grab and go sessions, I just use a small manfrotto 055 tripod and an Astroslew alt-az head.

Binoviewing wise, you need the short tube. Might barely reached focus with the baader binoviewer and t2 diagonal. No ocs is required.


#6 Astronewb



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Posted 19 December 2013 - 10:40 AM

I image with a Borg 125SD/F3.9 with the 7704 reducer/corrector. You would never know the ota is just a doublet.

Posted Image
the Final Mission, M31 Andromeda by Astronewb2011, on Flickr

I have the Feathertouch M57 focuser, and it works fine with the 7704 but, if you use this setup, because of the short travel, it does have light leakage around the focuser tube.

Take some darks inside and check for leakage before imaging. I had to wrap gaffer's tape around the focuser tube to eliminate some nasty light leakage. Once done, it's perfect.

Here's a link to a short video demonstrating the issue with the Borg Feathertouch: http://youtu.be/VezfV9ggyzI

Having used the Borg 125SD for a few months now, the only fault I can find is that I didn't purchase it two years ago..:)

Hope the info helps...Paul

#7 sberrada


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Posted 19 December 2013 - 07:31 PM

Thanks very much to each of you, the comments are very helpful. Seems like the 125SD has an excellent performance.


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