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xumaxer
super member
Reged: 01/30/06
Posts: 126
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Hi all
I could use a little help out here.
I finally got my WO ZS80FD piggybacked ontop of my C11 and tried to see how it would go AP speaking... So this is my first set of images taken with this rig. Mount is a G-11 gemini.
It was almost a full moon (2 days ago) and I aimed at M57, just to get the feel of the all package behaviour. I didn't really tried to pinpoint focus so bare that in mind.
I guided with PHD, which I have been doing for some time and with very good results (with my CG-5 GT).
This time I got a few 120 sec subs, shooting with my 350D+0.63x FR+Skyglow filter.
The first series was ok:
(cropped images)
http://img172.imageshack.us/img172/4998/m57redondasid7.jpg
Then, after a few shots I started to get this:
http://img296.imageshack.us/img296/1841/m57gota50sp5.jpg
Well, even though, I stacked the all subs (5x 120 sec + 19x 150sec) with 10 darks:
http://img49.imageshack.us/img49/5304/m57badpixreduzidard6.jpg
I know it's not sharp and most of the subs are "trailed" so...
But anyway, can some tell what might have gone wrong???
Urban skies
guided with DMK21AF
Thanks!
Ciao
xumie
--------------------
Ciao
xumie
________________________________
C11
WO ZS80FD
G-11 Gemini
ST2000XM + CFW10
DMK21AF04.AS
350D unmod
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Make-it Better
super member
Reged: 06/30/07
Posts: 110
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I guessing -- but your imaging scope is working at a focal length of 1760mm and your guide scope is working at about 1/3 of this focal length. So a small movement in the guide scope is much larger in the imaging scope. Try the other way around (image in the 80mm and guide with the C11) to rule out flexure, mirror shift and mount problems. If that works try using a 3x or 5x barlow in the 80mm when guiding to get the focal length close to or longer than the C11. I've been told that an off-axis guider is probably better for an SCT because of the mirror slop issues.
Note: You didn't say which scope you were imaging with but I assumed the SCT because of the image size on M57.
Hope this helps,
--------------------
Roy P.
CGE C11
ED 80
400D
Edited by Make-it Better (07/18/08 06:50 AM)
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stefsaber
Post Laureate
Reged: 06/24/06
Posts: 4459
Loc: Rainy Florida
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Maybe you need to adjust the rate at which PHD tracks...it may not be correcting for drift quickly enough. If polar alignment is off it will become more apparent as the sessions wears on, so what may seem like a good guiding correction will quickly become outpaced...
If you get the drifting issue fixed though it looks like you'll have a smashing image! 
--------------------
-Stefan
"It’s not the fall that kills you; it’s the sudden stop at the end." -Douglas Adams
Current Scopes: "Gator" William Optics 66SD---Black Swan William Optics Megrez 80 II ED Triplet---Zhumell 10" Dob
-Sirius Mount---Canon Rebel XT-
Past Scopes: ETX 90---Vixen ED80Sf
Fort Myers, FL
Edited by stefsaber (07/18/08 09:58 PM)
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DaemonGPF
Pooh-Bah
Reged: 03/22/08
Posts: 1120
Loc: New Mexico
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Quote:
Maybe you need to adjust the rate at which PHD tracks...it may not be correcting for drift quickly enough. If polar alignment is off it will become more apparent as the sessions wears on, so what may seem like a good guiding correction will quickly become outpaced...
+1
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-Josh
*Orion Starblast Imaging 150mm OTA
*Orion Starblast Imaging 114mm OTA
*Meade 50mm AR short tube OTA
*Meade DSI Pro IIc
*Orion Starshoot DSCI
*CG5 mount
http://cleardarksky.com/c/AlbuqNMkey.html
My AP Gallery
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xumaxer
super member
Reged: 01/30/06
Posts: 126
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Hey guys!
Something crossed my mind yesterday, as I reviewed the Gemini manual: maybe, and just maybe, I did change the Hand Control Setup from Photo Mode to Visual Mode, disableing guiding...
I'd have to try it out again...
Just have to wait for the moon to get out of the way!
Will come back to you later on.
THX
Ciao
xumie
--------------------
Ciao
xumie
________________________________
C11
WO ZS80FD
G-11 Gemini
ST2000XM + CFW10
DMK21AF04.AS
350D unmod
Edited by xumaxer (07/19/08 08:59 AM)
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Jared
Carpal Tunnel
Reged: 10/11/05
Posts: 1786
Loc: Piedmont, California, U.S.
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Well, the elongation is in right ascension not declination, so it's unlikely to be related to poor polar alignment. So that leaves the following:
1) Guide scope doesn't have enough focal length to provide corrections for a C11, even when using a 0.63 focal reducer. I doubt this is the case, but it's a possibility.
2) Mount wasn't balanced quite right. My old GM-8 needed to be every so slightly East heavy and perfectly balanced in declination or everything became too jerky for the autoguider to handle. Given the similar design, I would expect the same thing to hold true for the G11. And a C11 isn't exactly a light, small optical tube.
I'd lean towards the second explanation. To mitigate against this, make sure your balance is absolutely perfect (meaning a few ounces heave on the East side, and perfectly balanced in Declination.
Best of luck!
--------------------
- Jared Willson
- Fluorostar FLT-110 w/ TEC optics
- Vixen VC200L
- Astro-Physics Mach1 GTO
- Stellarvue SV80S
- Takahashi Teegul SP Mount
- STL-11000
Edited by Jared (07/19/08 07:44 PM)
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