From: "doobisary" <tjp314@pacbell.net>
Date: November 3, 2012 10:16:05 AM MDT
To: Astro_IIDC@yahoogroups.com
Subject: Re: ONAG Review
Hi Milton:
That may be where I saw the instructions. I'll look that up, thanks!
Since the AO-2 isn't sensitive enough to track Saturn, it probably can't do the Galilean satellites either. I think it's rate was 30 times/sec. I don't remember how it's constructed, but it's all in a box about 2 or 3" square, with fittings for the focuser and an eyepiece or camera. There must be a barlow as well, as the image scale is pretty large and narrow without one.
I have an AO-7 that I bought with my ST2000XM and CFW-9 (or maybe that's a 10) filter wheel about 4 or 5 years ago. I haven't used it much, because it requires so much backfocus that I couldn't even use a focal reducer with my C-8 when using it. It worked on my Megrez SD 80 refractor and my 6" f/5 Jaegers refractor, though. But the 6" had tremendous stars in the blue and to some extent the green, so I only used it for AP one time. And the Megrez has collimation issues that I can't correct without rebuilding it, which doesn't seem worth doing.
I posted a question on the SBIG group the other day, where I've been pondering using the AO-7 as an active secondary in one of my Newt construction projects. I would mount the AO-7 and the SBIG camera on a sled focuser, so they're fixed with respect to each other. I was thinking about using a 12.5" f/3.5 mirror I have laying around, but it had a huge secondary, so the AO-7 probably isn't big enough not to vignette. I would think this should work, so long as the cable to the camera is long enough (or I could add an extension), but I hadn't gotten any replies last time I checked.
I corresponded with Terry Platt about their AO device when it was new. I think he said it wasn't fast enough for planetary, but he might have stopped at the fact that it was for use with their OAG, so couldn't guide on the target planet. But if it can correct as fast as you suggest, and one had an ONAG device,... Hm... But it is expensive. The AO-8 is currently about $800. I missed out last year when they had them on sale for $500 over the Holidays. Keeping my fingers crossed that they might do that again this year!
But these AO units only work with these company's cameras, right? Orion has one as well, so they must be workable with other cameras, I suppose. The AO-2 is completely self-contained. It must use either a beam splitter or track the planet via reflection off a window or something. It's a nice and tidy device, though. Wish it were more sensitive. It might be fun to try it out on a bright double star, though.
-Tim.
--- In Astro_IIDC@yahoogroups.com, Milton Aupperle <maupperl@...> wrote:
Hi Tim;
The instructions for the ONAG may have been from an article that Jim
Chung wrote in the RASC publication.
I'd love to see if your A02 makes any difference on Jupiter. Your best
bet is to use a moon as a turbulence / guide target so that it can use
a discrete object for centroid monitoring.
Darryl Robertson (Equinox and Equinox Image developer) was telling me
he could get the SBIG AO7 (used a mirror) running as high as 40 fps if
the guide star was bright enough. With the SBIG A08 (tilts a piece of
glass) - he was saying the mechanical limits were about 15 fps now.
While watching a hockey game (WHL) a month or so back, I was looking
at the "Starlight Xpress SXV AOL" (tilts a piece of glass) which
states it can do a tilt increment as fast as 5 ms (i.e. 200 fps). It's
RS232 based (9600 baud) so you can probably expect a 10 ms response
time (likely 100 fps) theoretical maximum movement. A few people that
posted frame rates for their own guiding were saying 10 to 20 fps -
but they were doing DSO imaging and most of these do not have bright
guide stars.
Not that I can afford a $1800 AOL - but it's interesting to look at.
One of the benefits of the ONAG would be no field rotation at all,
which is crucial for exoplanets. You want the same cluster of pixels
to be gathering starlight over the 2 to 6 hours your doing your run.
No matter how perfectly my Polar alignment is, I still get a 1 to 2
pixels (0.83 to 1.7 arc second) drift motion per hour with guiding. I
think it's due to field rotation because the OAG guide star is 20 to
25 arc minutes off axis. It would also be good for cometary /
asteroids too if you want to guide off the object.
TTYL..
Milton Aupperle
On 2-Nov-12, at 8:27 PM, doobisary wrote:
Hi Milton. I haven't read the article yet, but I remember seeing an
announcement of the ONAG some months back, probably also in S&T.
I'll poke around, but I think I saw instructions on how to make an
inexpensive version of the ONAG, obviously not as sophisticated, on
Cloudynights recently.
I don't think any of the AO units available today are fast enough to
account for turbulent motion of a planet. The only device like that
for amateur use that I know of is the AO-2, which came out 10 or
more years ago, from Stellar Products (Don Bruns). Antonio Cidadao
used one for planeatary imaging several years ago. After John
Sanford passed away this past spring, his son brought a truckload of
his astro gear to RTMC. John had an AO-2. I bought it from his son
for $100 (they were well over $1K when new). I fiddled with it
some, and quickly found it wasn't sensitive enough to hold Saturn
steady in an 8" telescope. I didn't try anything larger (10-12.5"
scopes I have) or brighter (Jupiter, Mars) with it, and I probably
should. I contacted Don Bruns via email, since I didn't have a
manual with the AO-2, which is essentially mint condition. He said
he no longer had any copies of the manual and that it was obsoleted
by fast frame rate cameras. So, Antonio graciously pr
ovided me a scanned copy of his manual.
Now that Jupiter's getting higher in the evening sky, I should pull
out the AO-2 and see how it does on the 12.5" Cave.
-Tim.
--- In Astro_IIDC@yahoogroups.com, "milton_aupperle" <maupperl@>
wrote:
Hi Folks;
If you don't have a subscription - pick up the December 2012 issue
of Sky And Telescope at your local news stand.
There is a really neat review on "Innovations Foresight's " ONAG
(On Axis Auto Guider" product on page 60. Not cheap at ~ $1000, but
interesting.
I'd never heard of it before, but it's basically a "cold mirror"
that reflects 350 to 750 nm light and passes all light above 750 nm
to the guide camera. So you can guide on the same or very close
to the same object your imaging with a single scope.
My Grasshopper EXHAD camera with Sony ICX285AL CCS would have about
50% sensitivity at 750nm and drops to about 5% at 1000 nm.
I also wonder if one could use that with an Adaptive Optics units,
for DSO / Photometry but also for imaging planetary targets to
remove turbulence.
TTYL..
Milton Aupperle