· Get a Cloudy Nights T-Shirt · Submit a Review / Article    Click here if you are having trouble logging into the forums Cloudy Nights - Official Forums of the 2009 International Year of Astronomy Privacy Policy | Please read our Terms of Service | Signup and Troubleshooting FAQ | Problems? PM a Red or a Green Gu.... uh, User   You are not logged in. [Login] Forum Archives · Entrance · Main Index · Search · New user · Who's Online FAQ · Calendar Astrophotography and Sketching >> Beginning and Intermediate Imaging Previous   Index   Next   Threaded   Pages: 1 Kenny2004 Pooh-Bah Reged: 08/17/04 Posts: 1476 Loc: Toronto, Canada Difficulty of imaging near Zenith       #3355504 - 09/25/09 08:20 AM Edit   Reply   Quote Quick Reply   Imaging an object near Zenith does result for me a degree of elongated stars. As the night proceeds on, this effect disappears as the objects starts to settle down in Declination. Do you all share the same observations? I have read papers stating that imaging near Zenith does have these problems and extremely critical to have good polar alignment, etc., However, even if one has the best possible equipment, alignment, etc, is this condition entirely avoidable? -------------------- Skywatcher Black Diamond 80ED /w HEQ5 Pro Celestron 8" SCT /w XLT Celestron CPC800XLT Meade DSI-C on a homebrew guidescope ATik 314L+ Philips SPC900NC Webcam Post Extras:       DaemonGPF Post Laureate Reged: 03/22/08 Posts: 3576 Loc: New Mexico Re: Difficulty of imaging near Zenith [Re: Kenny2004]       #3355557 - 09/25/09 09:06 AM Edit   Reply   Quote Quick Reply   Sometimes I can be an effect of slack in the gears in the mount. When your scopes are pointed towards one side or the other, you generally have some weight on the gears to keep them tight. This situation is avoidable even with entry level gear. I seem to have obtained some of my best images near zenith with my GC5 and LXD75 mounts. -------------------- -Josh http://cleardarksky.com/c/AlbuqNMkey.html My AP Gallery Post Extras:       cdndob professor emeritus Reged: 07/28/06 Posts: 658 Loc: The Great White North Re: Difficulty of imaging near Zenith [Re: DaemonGPF]       #3355631 - 09/25/09 09:53 AM Edit   Reply   Quote Quick Reply   My best guess would be to check your balance near zenith, make sure its a little "east heavy". Next time imaging bring out a small weight you can attach to the east side once you see the elongated stars and see if the problem goes away. If that doesn't fix it I'd look for a flexure issue next. Does this show up when imaging with your ED80 or only with one of your other scopes? Steve Post Extras:       jgraham Postmaster Reged: 12/02/04 Posts: 6763 Loc: Dayton, Ohio Re: Difficulty of imaging near Zenith [Re: cdndob]       #3355832 - 09/25/09 11:42 AM Edit   Reply   Quote Quick Reply   Yep, that's what you get sometimes if you pass through a region where the ballance shifts from one side to another. Polar alignment becomes increasingly important the closer you get to the pole (imaging NGC188 can be real fun). -------------------- -John ================================================ Homebuilt scopes from 4.25-16.5" Meade LXD75-N6/SN6/SC8, DSX-90, ETX-60BB, ETX-125PE, DS-2130 Orion StarBlast, BinoViewers, Coronado PST Rebel XT/XTi, DSI Pro (I, II, & III), DSI, LPI, Electronic Eyepiece, Phillips SPC900NC Tasco 60mm Refractors Post Extras:       Footbag sage Reged: 04/13/09 Posts: 466 Loc: Scranton, PA Re: Difficulty of imaging near Zenith [Re: jgraham]       #3355854 - 09/25/09 11:50 AM Edit   Reply   Quote Quick Reply   With the CPC 800? I had noticed that I have poor sessions when I don't ensure that the knobs are tightened all of the way into the base of the scope. When the weight is that high up, it's much more likely to shift. -------------------- Adam Celestron CPC 800, Celestron HD Wedge Hyperion 17mm, Celestron 40mm Plossl, TMB 9mm WO 66, SSAG Modded Canon XS Lackawanna Astronomical Society My Gallery Post Extras:       yock1960 professor emeritus Reged: 06/22/08 Posts: 980 Loc: SW Ohio, USA Re: Difficulty of imaging near Zenith [Re: cdndob]       #3355981 - 09/25/09 12:52 PM Edit   Reply   Quote Quick Reply   Why haven't I thought of this! Steve -------------------- LXD75 GEM Orion Starblast 4.5" Imaging Reflector William Optics Zenithstar 66 SD APO Meade DSI II OSC Meade DSI III OSC Orion Starshoot Autoguider Televue Powermate 2.5x Discovery 6" Dobsonian Nikon Action Extreme 10x50's Gallery Post Extras:       russ_watters Pooh-Bah Reged: 11/24/04 Posts: 1277 Loc: Trappe, PA Re: Difficulty of imaging near Zenith [Re: yock1960]       #3356671 - 09/25/09 07:04 PM Edit   Reply   Quote Quick Reply   I have the same issue and it doesn't seem to have anything to do with my polar alignment (it is pretty consistent no matter how good my alignment is). For me, with my heavily loaded mount, I'm guessing flexure. -------------------- Equipment: Orion Atlas 11, ED80, DSI-C, DSI II Pro, Dell Inspiron Laptop. www.russsscope.net Post Extras:       Pages: 1 Previous   Index   Next   Threaded   Extra information 4 registered and 2 anonymous users are browsing this forum. 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