From: Mark Gaffney <markgaffney@me.com>
Date: September 13, 2010 8:09:53 PM MDT
To: Astro_IIDC@yahoogroups.com
Subject: Re: [Astro_IIDC] new guiding log...
Milton,
The grinding noise has pretty well disappeared altogether now that I`ve loosened the knob below the tripod a little (whilst keeping the rocking play of the mount on top to a minimum) & wasn`t there at all before, unless I stopped slewing & started again when bringing the RA index marks together going west to east.
The adjustment of this knob requires a compromise between the two.. the rocking or the grinding. I think I presently have it set at best for both..
You say in a version of the Manual I`ve printed out that if using long focal lengths, larger Min RA & Dec Dist`s should be used.
I only had these set at 25 for RA & 15 for Dec.
Should I increase them dramatically next time?
I realise that you`re guiding through your reducer & OAG & not a guidescope & would be using cameras by & large of smaller pixel size..
I don`t understand if the guiding in my set-up based upon the focal length of the Kwiq scope or of the C9.25 or is it again, some sort of compromise between the two?
Would the FL of the Kwiq be (at 9 x 50 mm) a FL of 450 mm..?
How much slop would be reasonable..?
I know from your log you`ve sent me you`re getting 2 arc second differences (but this is probably an excellent result obtained from much practise at doing this on your part..?). You`re saying you have the distances set at 40 + for just an 1125 mm focal length so what would I need for 2350 mm if this is the case...?!
I`ll try what you suggest & slew back & forward between targets to see if I`m turning up at the same position as before.
The weather`s pretty dodgy again here so I don`t know when this`ll be possible...
I was very pleased with the results of the Precise Go To this time though..!
Mark.
On 14/09/2010, at 10:43 AM, Milton Aupperle wrote:
Mark;
It's not much better than the last one, as you can tell from reading
the 10th to 16th line into the file (which I explained the last 2
times too).
CalibX4: R Dist 321.48 X1: 1204.78 Y1: 487.89
CalibX5: L Dist 368.46 X2: 1501.97 Y2: 705.71
CalibX6: R Dist 166.42 X1: 1383.21 Y1: 589.12
CalibX7: L Dist 509.31 X2: 911.26 Y2: 397.65
CalibX8: R Dist 494.75 X1: 1336.64 Y1 650.29
CalibX9: L Dist 196.94 X2: 1259.86 Y2: 468.94
One time its 166 pixels, the next time it's 509. That's grossly out of
whack and you much have at least 40 arc seconds of slop on the mount
in the RA. As I said before, when I do my guiding at 1150 mm focal
lengths, my R and L distances for the calibration are < 1% different
(i.e. L and R distances are 40 +/-2 pixels / arc seconds for all
passes).
The Dec did not complete reliably either and had to re-try multiple
times, which also tells me your Dec is not really good either.
If you have a grinding noise, then your gear position or tension needs
adjustment. Not only will it track like crap (as evidenced above and
in your log with jumps of +/- 60 pixels), it will also not do star
alignment reliably either. Slewing back and forth between a few
targets (i.e M42 to M46 to M42 to M46 to M42) and see if it's still
centered on the last change. You might need to give it a bigger range,
but if the targets are not' centered between runs then you have slop
in the mount.
So you still have the same mechanical issues I mentioned last time and
have not resolved them yet so it simply will never track well.
I would not even bother putting a DSLR camera on until you sort out
the Mechanical issues and get some decent calibrations.
Milton Aupperle
On 13-Sep-10, at 5:37 PM, Mark Gaffney wrote:
>
>
> Milton,
> I got out & attempted to image M 42 early this morning (4 am) but rain
> closed me down before I took any shots with the DSLR..
> M 42 was just above the tall trees I have at the new site in the
> north-
> east.
> Above is the guiding log for the brief session..I hope it`s improved
> over previous excursions?
> I`ve realised I`d do better in future using my f6.3 reducer with the
> Nikon D5000 & C9.25 but the above is with my Kwiq guidescope (9 x 50
> mm) & Scorpion camera guiding the complete 2350 mm FL of the scope.
> I`ve set the autoguide rate on the mount at 75 % of sidereal (Azm &
> Dec) & loosened my tightening of the knob below the tripod a little so
> there`s less of a binding noise..The rocking of the mount on the
> tripod is still virtually non existent..
> The backlash settings should be still all at noughts- I haven`t
> touched them since the re-set. ( mentioned below)
> My Precise Go To (nearby star Altinak) is much better since I did a
> factory reset of the mount (due to somebody running over my leads with
> a car & causing an intermittant connection which led to erroneous
> slews with with my new 240 volt- 12 volt power adapter..) I thought at
> first there was something wrong with it..!
> I appear to be actually seeing the nebula in the FOV of my 25 mm EP at
> least.
> I did a 2 star, 1 star callibration alignment & All Star PA earlier in
> the night, this time using my 12 mm illuminated reticle EP for all
> alignments & got the "Display Align" (which is the measure of PA
> accuracy available after doing an All Star PA) down to Azm : 00* 00'
> 01" & Alt : 00* 00' 01"
> The Up & Right direction buttons were used for finalising the earlier
> alignments as usual..
>
> Mark.