[Avodah] rega = sha`a / 58888

[Simon Montagu]

In Berachot 7a the gemara says that a rega is 1/58888 of an hour.

Are there any perushim that say where this number comes from? I assume
the Amoraim didn't pluck it out of thin air.

I gather from some internet research that there are variant readings:

http://web.nli.org.il/sites/NLI/Hebrew/collections/jewish-collection/Talmud/Pages/default.aspx?IsByManuscript=False&Im_Ms=222&Fr_Co=4&Fr_Tr=01&Pe_code=007&Mi_code=01&Li_code=-1
or bit.ly/O845Pk has a marginal note saying that it should be 13824,
which fits the Yerushalmi 5a: "an `ona is 1/24 of an hour; an `et is
1/24 of an `ona; a rega is 1/24 of an `et"; but the Yerushalmi then
brings another opinion that a rega is 1/56848 of an hour, which is
much closer to our gemara.

For the record, 58888 = 8 x 17 x 433; 56848 = 16 * 11 * 17 * 19.

Then http://books.google.co.il/books?id=Agw6AAAAIAAJ&pg=PA36&lpg=PA36&dq=58888+hour+moment&source=bl&ots=exVfiAaJr3&sig=OcfMDQb5mncNERyhHRjNSONrqiw&hl=en&sa=X&ei=WR0kUJvmD6ri4QTZnYD4AQ&redir_esc=y#v=onepage&q=58888%20hour%20moment&f=false
or http://bit.ly/Nqqfae has a footnote saying  "The correct number is
82,080; see Brodetsky in JR II p. 173". The reference seems to be to
Selig Brodetsky: Astronomy in the Babylonian Talmud in the Jewish
Review Vol. II No 8. July, 1911, but I wasn't able to find the article
online.

Any further insights welcome.

And a general question: I have been reading daf yomi and listening to
various online shiurim without going into great depth, but in most
dapim there are one or two issues like this one which catch my
attention and which I want to investigate further. What are good
places to look for more in-depth material? I usually look at the
Maharsha, Maharatz Hayes and Rashash, and then get stuck.