90mm f/7 APOs

Robin Lee · Post by **Robin Lee** » Fri Nov 10, 2006 11:09 pm

wucheeyiun wrote:Kim Miau, you can check with Airconvent for his ZS66 Petzval ....he is selling it...

Thanks for your information.

ariefm71 · Post by **ariefm71** » Sat Nov 11, 2006 10:08 am

I say the 90 will win. The 80 may have better glass, but I believe the superiority of that glass will only be very obvious (compared to the 90) on very good nights.

For most nights, you will enjoy the extra aperture better.

Thanks Vin for the advice :-)

Anat, how's the color correction of your friend's Borg 77ED? I can probably get a used Borg 100ED f/6.4 from Japan for about the same price as Meg90.

Arief

anat · Post by **anat** » Sat Nov 11, 2006 10:18 am

I have never viewed through it. Note that the helical focuser placed between an OTA and a diagonal is not easy to use for visual purpose. But if you place a smaller helical focuser between a diagonal and an eyepiece, it is very easy to use and smooooooth.

jermng · Post by **jermng** » Sat Nov 11, 2006 3:26 pm

Sorry for going slightly OT. Could you recommend a good helical focuser to go between diag and EP? Thanks!

MooEy · Post by **MooEy** » Sat Nov 11, 2006 3:29 pm

the borg's helical focuser does not turn the diagonal when focusing. rough focusing is done by moving in and out the drawtube. fine focusing is done with the helical focuser. this might be annoying for those with eyepiece that have very big focusing difference. but still, the range of focus of the helical focuser is quite big.

colour correction of the older borg 76ed is very gd. unless one start looking for it, one would not notice it. definately a big jump over all the semi-apos out there.

i can't comment on the CA of the borg101ed though, although i can tell u that i have always wanted to own one due to the small size and light weight. not to be used as a planet killer though, more of deep skies and maybe play ard with a binoviewer.

~MooEy~

anat · Post by **anat** » Sat Nov 11, 2006 3:46 pm

When the helical focuser is placed between a diagonal and an OTA, the focuser bends due to the weight of the diagonal and eyepiece. You begin to notice friction, slip, backlash, etc.

Jeremy, I am using the Borg M42 Helicoid T focuser (#7839) + some adapters.
http://www.tomytec.co.jp/borg/product/p ... index.html

Anat

jermng · Post by **jermng** » Sat Nov 11, 2006 4:04 pm

Thanks anat. It doesn't fit straight into 2" diags right? Is there one that does? Or is this the best one (smoothest?) which is why you use it?

MooEy · Post by **MooEy** » Sat Nov 11, 2006 4:17 pm

oo, maybe i have more luck. the one on the series 80 borgs are 7835.

~MooEy~

anat · Post by **anat** » Mon Nov 13, 2006 8:18 am

Reviews of WO 90 Megrez and Flourorstar 110 in SkyNews Astronomy Magazine by Terrance Dickinson.

http://www.skynewsmagazine.com/pages/re ... csnd06.pdf

Robin Lee · Post by **Robin Lee** » Fri Nov 17, 2006 10:57 pm

Thanks for sharing this. I just discover a free magazine.