Thanks! I thought I had seen an unverified report that 81mm was the back focus
distance for the Antares.
That means I need to find a way to come up with the 37mm I need for my
EFW/ASI1600 combo. Hmm. That should be fun! :-)
Whoops! It’s not 37mm for the adapter. I was thinking my EFW/ASI had 44mm to
match my Canon. But it matches the Canon’s spacing when I have the EOS EF
adapter in the train. Without it, the distance from the EFW’s flange to the
sensor is 37.5mm. That means I need a 43.5mm adapter. Even more fun! :-)
And the Starizona SCT Corrector’s 52.8mm adapter will also be fun to find. At
least it specifies a +/-2mm tolerance.
That 61mm distance for the Celestron reducer probably matches the length of
their SCT T-adapter.
Mike McDonald
mikemac@xxxxxxxxxxx
On Jun 3, 2019, at 12:26 PM, David <ddillmore@xxxxxxx> wrote:
Dear Mike,
Try this link,
http://www.astrotarp.com/Focal_Reducer_Distance_to_Sensor_Page.html
I had the same or similar problem. I recently set up my focal train with
focuser, focal reducer, filter wheel, then Nikon D5600 DSLR camera. My
images were horrible. Stars on the outside were severely bloated and looked
more like shuttlecocks. To correct the problem I had to remove the filter
wheel and change camera adaptor to a shorter one I found in my parts bin.
This brought my camera about 2 inches close to the focal reducer.
________________________________
From: az-observing-bounce@xxxxxxxxxxxxx <az-observing-bounce@xxxxxxxxxxxxx>
on behalf of Michael McDonald <mikemac@xxxxxxxxxxx>
Sent: Sunday, June 2, 2019 6:32:43 PM
To: az-observing@xxxxxxxxxxxxx
Subject: [AZ-Observing] Re: Playing last night
Does anyone know what the “back focus” distance is for these reducers? What’s
the proper distance from the male threads to the focal plane? Or don’t I
understand how they work/should be connected? Starizona’s SCT Corrector II
specifies a 90.3mm +/- 2mm. My EFW to ASI1600 sensor back focus is 37.5mm.
Means I’d need a ~2” adapter for the Starizona. But the
Antares/Celestron/Meade f6.3 reducer doesn’t say anywhere I’ve found.
Mike McDonald
mikemac@xxxxxxxxxxx
