Darren, Larry, thanks for your toughts - precisely the kind of info I'm
looking for, from hands-on knowledge.
Darren, I have used my phone's level and a compass to set the camera
for Iridium trail photos and to look for comets, and am near the equator
- no real need for a latitude wedge, just some tripod leg tuning until
I'm close to 4deg tilt in the right direction. since I intend to keep
the exposures as short as possible (yet longer than my current 2 sec
limit), some small errors should be acceptable - and from what I
understand, the Polarie is not plagued by the tracking error a
tangential barn door drive is famous for. the need to manually track
between exposures with the O-GPS is part of the reason why I am
interested in the Polarie/ barn door drive, added to the possible use of
a smallish reflector.
the calibration proccess - in theory - does not frighten me. I will
have a setup to make either way. one question, for you users - this
O-GPS 1 calibration holds with the camera sleeping (not off but after
the metering time-out)? for me, the best about the O-GPS is both size
and faster setup/ calibration - or am I wrong about the real world
calibration?
last night, talking to Larry, it did pass my mind a curious notion -
that **IF** the O-GPS1 actually communicates with the camera by means of
the flash contacs, **AND ASSUMING** said comm would still happen through
a TTL flash cable, would it be possible to align the O-GPS1 with a
telescope tube and get the correct tracking? context: under 1000mm
tubes, most likely in the 500 to 650mm. anyone with the O-GPS and a TTL
flash extension willing to make a field test?? it could also open the
way to some sideways traking and curious images.
thanks yet again, and not only for the ideas, those pics ARE
outstanding!!!
--
luiz felipe
luiz.felipe at luizfelipe.fot.br
history
Date: Fri, 8 Jun 2018 23:17:41 -0500
From: Darren Addy <[email protected]>
To: Pentax-Discuss Mail List <[email protected]>
Subject: Re: Vixen Polarie - not Pentax, but I'll use with Pentaxes -
any toughts?
I have the Vixen Polarie. I had an O-GPS1 for a time, but sold it. I
now
have the AstroTrack built into the K-3ii.
The biggest differences are:
No annoying calibration necessary with the Polarie, but it must be
polar
aligned. (I built an adjustable wedge for the latitude part of the
equation, so if your tripod is level and the wedge angle correct, the
only
thing you need to dial in is the azimuth alignment.)
https://flic.kr/p/pVVUTv
Both systems will face limitations at longer focal lengths, but you
can do
a lot with 200mm or less. This was taken with a 90mm Tokina AT-X macro
on
the jankity set-up above.
https://flic.kr/p/qzf4Xi
The O-GPS will track during an exposure, but the camera will need to
be
repositioned as the earth?s rotation moves it out of frame. The
Polarie
will track the object whether you are taking exposures or not (meaning
you
can use an intervalometer to take multiple exposures (for later
stacking,
for example)
I think the biggest problem with my current Polarie set-up is flex.
Even
with a high quality ball head, it can be frustrating to think you have
your
object framed properly, tighten the bullhead down, let go, and find
your
object is no longer framed as you like. This problem gets greater the
more
weight you try to hang of of it.
Both solutions are more for wide field astrophotography. But nice
things
can be done with the O-GPS and the DA* 200mm f2.8 as this French
Pentaxian
shows:
http://poirierstephane.free.fr/photos/index.php?/category/132
However, it is worth pointing out that the same lens on a polar
aligned
Polarie could achieve the same results.
Hope this helps.
Darren Addy
Kearney, NE
On Fri, Jun 8, 2018 at 3:15 PM luiz felipe <[email protected]>
wrote:
pretty much divided between the Vixen Polarie and the O-GPS 1. just
because if I get to use a small newtonian reflex, the camera will be
pointed at 90 degrees from the subject, and I don't think de astro
function of the O-GPS 1 can handle that.
the Vixen Polarie is small, and seems able to handle both the APS
Pentaxes and a small reflex telescope - and as long as it's properly
aligned, the pics should be ok.
as far as money goes, it's one OR the other, and that's why I'm looking
for advice. building a barn door star tracker is the third option, but
I'm not really with time to make a proper unit. toughts? ideas?
thanks!!!
--
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