· Get a Cloudy Nights T-Shirt · Submit a Review / Article Click here if you are having trouble logging into the forums 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] Entrance · Main Index · Search · New user · Who's Online FAQ · Calendar Equipment Discussions >> Mounts Previous   Index   Next   Threaded   Pages: 1 Grouptele sage Reged: 08/11/07 Loc: Qcy, IL PE on EQ-G       #3149181 - 06/06/09 04:13 PM Attachment (51 downloads) Edit   Reply   Quote Quick Reply   Dang it... deleted the original post due to an error on the PecPrep analysis. OK... After a little over 1 yr of using an EQ-G, I have finally joined the "guiding" bandwagon; thus, proceeded to evaluate the pe. Following analysis were done with a C8 + finder scope + 6.3fr + Phillips webcam + PDH module (the webcam was installed on the C8 for ease of the exercise. The below screen shot is for the unguided run. Basis my scant experience with guiding, looks like the pk-pk pe is 6 arcsec for a little over 1 complete worm cycle, and it also looks like there are lots of higher frequency events going on, as evidenced by the rippled raw data dnd the FFT survey. Unguided images (less than 2min typ) at 1200fl show fairly round stars, yet my guided images (3min typ) show some irregular star distortion (but no tails). Thus, the aim of this exercise was to find if the source of star distortion is the mount pe or the guiding set-up. So far, I have used the default PDH set-up, except for agressivness (80%). Any comments are appreciated. Victor Edited by Grouptele (06/06/09 05:57 PM) Post Extras:       Grouptele sage Reged: 08/11/07 Loc: Qcy, IL Re: PE on EQ-G [Re: Grouptele]       #3149340 - 06/06/09 05:59 PM Attachment (41 downloads) Edit   Reply   Quote Quick Reply   Here's the guided screen shot. Victor Post Extras:       Dennis Sakva Pooh-Bah Reged: 10/19/04 Loc: Kiev, Ukraine Re: PE on EQ-G [Re: Grouptele]       #3150418 - 06/07/09 12:41 PM Edit   Reply   Quote Quick Reply   Victor, look at your DEC axis. PECPrep allows that to do. It will show you how atmosphere is behaving. If it is close to +/-1" then there's not much you can do. Also look carefully at 10.2 seconds cycle. Is it relatively large? It causes the most problems with guiding. Longer cycles are guided out much more easily. Regards, Dennis. Post Extras:       Dennis Sakva Pooh-Bah Reged: 10/19/04 Loc: Kiev, Ukraine Re: PE on EQ-G [Re: Dennis Sakva]       #3150426 - 06/07/09 12:45 PM Edit   Reply   Quote Quick Reply   One more thing. How do you guide? Separate guidescope or OAG? If it's a separate guidescope differential flexure (when main scope and guidescope flex relatively to each other) can be the reason for distorted stars. If it's OAG then check how securely the guidecam and main cameras are attached. Post Extras:       Grouptele sage Reged: 08/11/07 Loc: Qcy, IL Re: PE on EQ-G [Re: Dennis Sakva]       #3150611 - 06/07/09 02:33 PM Edit   Reply   Quote Quick Reply   Dennis, Freq spectrum shows little amplitude at 10.2sec, but slightly higher at 5sec. After worm cycle, largest amplitude visible is the stepper gear, at 125sec. At 1sec, amplitude is also very small. I do not recall bad seeing during the capture session. How do you view the DEC axis trend on PECPrep? I have been using the default settings, which show the "Y" axis. As to your question about how I was guiding, for this particular run I was guiding through the main scope (8" SCT) and was not imaging; thus, no flexure problems. When I image, I use a side-side set-up and guide through a 66mm refractor. Victor. Post Extras:       Levente sage Reged: 01/20/04 Loc: Budapest, Hungary Re: PE on EQ-G [Re: Grouptele]       #3150957 - 06/07/09 06:22 PM Edit   Reply   Quote Quick Reply   Victor, are you absolutely sure that your evaluation is correct? I think +-2.8" periodic error unguided is too optimistic even for a Tak or Astrophisics mount. Post Extras:       Grouptele sage Reged: 08/11/07 Loc: Qcy, IL Re: PE on EQ-G [Re: Levente]       #3151193 - 06/07/09 08:43 PM Edit   Reply   Quote Quick Reply   Levente, That is a good question. The answer is: I am not sure. The basic input to PECPrep [using PDH] is correct (e.g., 1282mm focal length (C8 at f6.3) and 5.6um pixel size (NC9000 webcam]. Otherwise, I used the default values for PECPrep. I agree that my raw data looks optimistic when compared to other EQ6 data, but I just do not know what the error might be. Victor Post Extras:       Dennis Sakva Pooh-Bah Reged: 10/19/04 Loc: Kiev, Ukraine Re: PE on EQ-G [Re: Grouptele]       #3151644 - 06/08/09 02:29 AM Edit   Reply   Quote Quick Reply   There's an option like Open DEC data, next to where your load your RA data. Post Extras:       Tapio Pooh-Bah Reged: 09/24/06 Loc: Tampere, Finland Re: PE on EQ-G [Re: Dennis Sakva]       #3151680 - 06/08/09 03:39 AM Edit   Reply   Quote Quick Reply   I agree, 6" peak-to-peak sounds too good to be true. However if you get pretty round stars with 1200mm focal length and 2 min exposures it tells that you have a good mount. I get about 12" peak-to-peak values with my HEQ5 Pro (aka Sirius mount). Post Extras:       Grouptele sage Reged: 08/11/07 Loc: Qcy, IL Re: PE on EQ-G [Re: Tapio]       #3153009 - 06/08/09 08:30 PM Attachment (29 downloads) Edit   Reply   Quote Quick Reply   With the help of other fellows, just found that I did not compensate for the declination of the guide star (e.g., it was nearby Mizar, at about 55deg DEC). Re-ran PECPrep with this new information, and the pe now came to 12.7" pk-pk, which seems to be more in line with the typical EQ-G - see the attached screen capture. Thanks for the comments and hints with this issue. Victor Post Extras:       Pages: 1 Previous   Index   Next   Threaded   Extra information 17 registered and 39 anonymous users are browsing this forum. 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