Borg 0.7x Super Reducer

huerbsch
07 Mar, 2018 19:01
Anyone used the super reducer with other brand triplets? Threaded connection to 2.5" focuser, full frame correction and preset markings on barrel for focal length of the scope look great.  But 130mm of backfocus is even more than the Riccardi reducer : (

It would give me two more useful focal lengths of 295mm @ f/4.1 with my GT71 (super wide-field) and 637mm @ f/4.9 with the AT130

For example, SH2-240 requires 4 panels for me to do right now, but I could fit it in 2 panels with the super reducer, and at f/4.1 instead of f4.7 would be able to integrate sooner as well.

http://www.sciencecenter.net/hutech/prices/borgparts/html/7870.htm
Edited 07 Mar, 2018 19:07
whwang
08 Mar, 2018 00:56
Hi,

There are a few things for you to worry.  First, it's an old product.  It may not be available now.  The BORG website no longer lists it.  The two reducers listed on BORG's website are optimized for its current FL series refractors, and they don't have continuously adjustable lenses to match the focal length of many different objective lens.

Second, I am not sure what the 130mm backfocus means.  It may not be what you think.  If you look at the website you mentioned, you see two example configurations listed.  For example, for the DSLR, you need two additional adapters, 7923 and 5005.  Both are very thin.  There isn't too much additional distance between the reducer and a DSLR.

Finally, this reducer (and all other BORG reducers) is optimized for doublets, not triplets.  BORG refractors are doublets, so this is very understandable.  The catch here is, for the same focal length, a doublet and a triplet may have different field curvatures, and therefore different optimal configuration for a reducer or a flattener. The reducer may still work on your triplet, but the required lens position may not be the focal length indicated on the reducer tube.  You may need to try several different positions and find out which one works the best for your triplet.

Good luck.
Edited 08 Mar, 2018 00:57
huerbsch
08 Mar, 2018 17:19
thanks for your comments! The description reads for triplets, while the 7072 is optimzed for two of their doublets. I was able to source one for an excellent price so will be testing next week  smile

I saw some AB photos with it on Tak scopes and it looked good
Edited 08 Mar, 2018 17:21
whwang
09 Mar, 2018 00:29
I think the word triplet on the page means that this reducer has three lenses. It doesn’t mean it is optimized for a triplet objective lens.

Anyway, if you can find one with a good price, it is worth a try.
 
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