Re: [ap-gto] 1600 mount tracking/guiding test


Sep 14, 2017

 


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#58282 Sep 14, 2017

OOps! That should read 5 x 20 minute exposures.



Rolando







-----Original Message-----

From: chris1011@... [ap-gto] ap-gto@yahoogroups.com>

To: ap-gto ap-gto@yahoogroups.com>; ap-ug ap-ug@yahoogroups.com>

Sent: Thu, Sep 14, 2017 4:12 pm

Subject: [ap-gto] 1600 mount tracking/guiding test





Hi All,

Had a calm night of good seeing, did some testing on the 1600 mount with 17" F8 astrograph. Guider scale is 1 arc sec per pixel. Guide subs were 20 sec. each. Note RMS guide values(peak values include dither moves).

www.astromart.com/common/image_popup.asp?image=/images/forums/835000-835999/835867.jpg&caption=

Resultant image:

www.astromart.com/common/image_popup.asp?image=/images/forums/835000-835999/835866.jpg&caption=

 50 x 20 minute exposure in H-a, scope was the AP 17" F8 astrograph, STL11K camera, 1600 mount.

Rolando



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#58286 Sep 14, 2017

At 0.2 sec min move in Maxim, the mount gets a move command of 3 arc sec (0.2sec x 15 arc sec/sec). The min move in Maxim is in seconds. Is PHD in seconds or in arc seconds?



Rolando







-----Original Message-----

From: Bill Long bill@... [ap-gto] ap-gto@yahoogroups.com>

To: ap-gto ap-gto@yahoogroups.com>

Sent: Thu, Sep 14, 2017 4:36 pm

Subject: Re: [ap-gto] 1600 mount tracking/guiding test





Wow, I think PHD has minmo set to .2 for each axis by default. I may have to try the 5 second calibration and these min/mo settings. 

Does MaximDL have aggressiveness settings? 



From: ap-gto@yahoogroups.com ap-gto@yahoogroups.com> on behalf of chris1011@... [ap-gto] ap-gto@yahoogroups.com>Sent: Thursday, September 14, 2017 2:28 PMTo: ap-gto@yahoogroups.comSubject: Re: [ap-gto] 1600 mount tracking/guiding test 



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#58287 Sep 14, 2017

By looking at their documentation it is in pixels it seems.





From: ap-gto@yahoogroups.com ap-gto@yahoogroups.com> on behalf of chris1011@... [ap-gto] ap-gto@yahoogroups.com>

Sent: Thursday, September 14, 2017 2:47 PM

To: ap-gto@yahoogroups.com

Subject: Re: [ap-gto] 1600 mount tracking/guiding test 



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#58288 Sep 14, 2017

In that case then 0.2 makes sense.If you have a very steady night you can probably lower it to 0,1.



Rolando







-----Original Message-----

From: Bill Long bill@... [ap-gto] ap-gto@yahoogroups.com>

To: ap-gto ap-gto@yahoogroups.com>

Sent: Thu, Sep 14, 2017 4:53 pm

Subject: Re: [ap-gto] 1600 mount tracking/guiding test





By looking at their documentation it is in pixels it seems.



From: ap-gto@yahoogroups.com ap-gto@yahoogroups.com> on behalf of chris1011@... [ap-gto] ap-gto@yahoogroups.com>Sent: Thursday, September 14, 2017 2:47 PMTo: ap-gto@yahoogroups.comSubject: Re: [ap-gto] 1600 mount tracking/guiding test 



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#58289 Sep 14, 2017

may have to try the 5 second calibration

I use 5 seconds with my 17" because of the 3450mm focal length. In the case of smaller scopes with shorter focal lengths I would advise going at least 10 seconds and even up to 20 seconds. This will produce the most accurate calibration result.



Rolando





-----Original Message-----

From: Bill Long bill@... [ap-gto] ap-gto@yahoogroups.com>

To: ap-gto ap-gto@yahoogroups.com>

Sent: Thu, Sep 14, 2017 4:36 pm

Subject: Re: [ap-gto] 1600 mount tracking/guiding test





Wow, I think PHD has minmo set to .2 for each axis by default. I may have to try the 5 second calibration and these min/mo settings. 

Does MaximDL have aggressiveness settings? 



From: ap-gto@yahoogroups.com ap-gto@yahoogroups.com> on behalf of chris1011@... [ap-gto] ap-gto@yahoogroups.com>Sent: Thursday, September 14, 2017 2:28 PMTo: ap-gto@yahoogroups.comSubject: Re: [ap-gto] 1600 mount tracking/guiding test 



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#58290 Sep 14, 2017

Interesting. 

So on my AP1100 with my TOA130 refractor (700mm with reducer on it) I should use 10-20 second guide exposures for calibration? How about for actual guiding 3-5?





From: ap-gto@yahoogroups.com ap-gto@yahoogroups.com> on behalf of chris1011@... [ap-gto] ap-gto@yahoogroups.com>

Sent: Thursday, September 14, 2017 3:05 PM

To: ap-gto@yahoogroups.com

Subject: Re: [ap-gto] 1600 mount tracking/guiding test 



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#58292 Sep 14, 2017

10-20 second guide exposures for calibration

That is not a guide exposure. The 10 to 20 seconds is the calibration move command. The exposure of the guide star is up to you and can be anything. If it's a bright star then 1 second exposure is just fine.





Rolando





-----Original Message-----

From: Bill Long bill@... [ap-gto] ap-gto@yahoogroups.com>

To: ap-gto ap-gto@yahoogroups.com>

Sent: Thu, Sep 14, 2017 5:20 pm

Subject: Re: [ap-gto] 1600 mount tracking/guiding test





Interesting. 

So on my AP1100 with my TOA130 refractor (700mm with reducer on it) I should use 10-20 second guide exposures for calibration? How about for actual guiding 3-5?



From: ap-gto@yahoogroups.com ap-gto@yahoogroups.com> on behalf of chris1011@... [ap-gto] ap-gto@yahoogroups.com>Sent: Thursday, September 14, 2017 3:05 PMTo: ap-gto@yahoogroups.comSubject: Re: [ap-gto] 1600 mount tracking/guiding test 







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#58295 Sep 14, 2017

Is the 1600 that much better than the 1100GTO? I can only get around .4RMS for Dec and RA on a good night of seeing? Am I going to have to upgradeJ.  From: ap-gto@yahoogroups.com [mailto:ap-gto@yahoogroups.com] Sent: Thursday, September 14, 2017 4:03 PMTo: ap-gto@yahoogroups.comSubject: Re: [ap-gto] 1600 mount tracking/guiding test



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#58296 Sep 14, 2017

Thanks Roland.

This move command thing either does not translate well to PHD or 20 seconds (20,000 ms) is too high of a value for it to use. 10,000 seems to be the max? 

Andy?





From: ap-gto@yahoogroups.com ap-gto@yahoogroups.com> on behalf of chris1011@... [ap-gto] ap-gto@yahoogroups.com>

Sent: Thursday, September 14, 2017 4:02 PM

To: ap-gto@yahoogroups.com

Subject: Re: [ap-gto] 1600 mount tracking/guiding test 



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#58300 Sep 14, 2017

Tonight is a good night for imaging, but not as good as last night. I'm getting .25 RMS on my guiding and 2.2 arc sec FWHM stars in a 20 min exposure. Last night the seeing was exceptional with 1.6 arc sec FWHM stars in 20 minutes. The RMS guide values are very much affected by seeing. The 1100 mount is every bit as capable as the 1600. A lot depends also on your scope. What is the FWHM of your guide star in a typical guide exposure?



Rolando







-----Original Message-----

From: 'Tony Benjamin' tonybenjamin@... [ap-gto] ap-gto@yahoogroups.com>

To: ap-gto ap-gto@yahoogroups.com>

Sent: Thu, Sep 14, 2017 9:59 pm

Subject: RE: [ap-gto] 1600 mount tracking/guiding test





Is the 1600 that much better than the 1100GTO? I can only get around .4RMS for Dec and RA on a good night of seeing? Am I going to have to upgradeJ. From: ap-gto@yahoogroups.com [mailto:ap-gto@yahoogroups.com]

Sent: Thursday, September 14, 2017 4:03 PM

To: ap-gto@yahoogroups.com

Subject: Re: [ap-gto] 1600 mount tracking/guiding test



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#58356 Sep 16, 2017

I was surprised of your guider integration time (20s).  I observed with my previous mount (Losmandy G11) and with my present mount (AP Mach1GTO) that I get usually better results at 3s integration time than at 1s where I believe I chase the seeing.  I never tried though integration times longer than 5s. I believe I should record a PEM curve with PemPro, look at the fastest variation of the PE in the worm cycle, and calculate my maximum integration time according to the maximum deviation I can accept depending on focal length and seeing conditions.  How do you choose your integration time likely to give best results ?  Clear skies  Antoine  De : ap-gto@yahoogroups.com [mailto:ap-gto@yahoogroups.com] Envoy. : vendredi 15 septembre 2017 00:05. : ap-gto@yahoogroups.comObjet : Re: [ap-gto] 1600 mount tracking/guiding test



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#58357 Sep 16, 2017

My rule of the thumb is an absolute minimum 50 pixels move for accurate calibration.  If you calibrate at equator, with 700mm focal length and say 5.4um pixel size as example, you get a resolution of 206*5.4/700=1.6arcsec/pixel.  This means you need to move an absolute minimum move on the sky of 1.6x50=80arcsecs, which at 1x guide rate says you need more than 80/15s => 6s calibration time minimum.  Longer moves will only improve the calibration results, upper limit being to not move the calibration star too close to the edge of the CCD chip.  Then review the calibration results : If the calibration move speeds are very close in +Y versus –Y and +X versus –X and the angle between X calibration vector and Y calibration vector is close to 90. you have a good calibration. If the angle is significantly different from 90. restart the whole process, this may mean the detection jumped to another star entering the field of your CCD. I often subframe a region so that there is a clear brighter star in the field and around it.  If +Y move and –Y move are significantly different, you have backlash in your gear train and calibration speed will be inaccurate. You can improve the calibration using a longer move time so as to offset the backlash but your guiding results may be poor since there will be latency at guide direction reversal. Better to adjust your backlash.  Clear skies  Antoine  De : ap-gto@yahoogroups.com [mailto:ap-gto@yahoogroups.com] Envoy. : vendredi 15 septembre 2017 00:20. : ap-gto@yahoogroups.comObjet : Re: [ap-gto] 1600 mount tracking/guiding test



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#58365 Sep 16, 2017

Hi Antoine,     There is a lower limit perhaps on guiding time, based onwhich guider camera sensor (CCD chip),  and guider f/number is used ( if aseparate guide scope is used instead of the imaging camera.s own internalguider).     I feel 3 seconds is borderline for say, SBIG.sexternal  RGH camera, where there is a fair amount of readout noise at lowexposures. Perhaps 5 to 10 seconds is better. That may be one of the bettercameras, considering it is TEM cooled, whereas some other newer one.s are not.Some of the latter may be less noisy perhaps because they are CMOS based. I use,5 sec. on my RGH, which seems tolerable.     Then again, there is a difference between the time usedduring initial Calibration run . where the exposure chosen can even be fairlylarge . and normal guiding after calibration which is a trade-off between largejumps in mount correction with longer guiding exposures, and perhaps getting aframe central dim star to remain measurable, or even visible,  duringperiods of bad seeing if one chooses shorter exposures. I would think 3 sec. isborderline for say,  the RGH. The CCDSOFT default of 5 sec. for bothoperations seems tolerable. Although, I sometimes get guide star drifts as highas a few RGH pixels (depending on the guider.s focal length) in poorer seeing.






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