Author Topic: Leo Triplet  (Read 115 times)

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NoelC

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Leo Triplet
« on: Feb 10, 2018, 16:58:38 »
A rough cut of  the Leo Triplet (about 29 5 min subs - L only).
Hopefully will get some RGB to go with it soon...


My tracking seemed rough at 0.6" rms (the occasional excursion taking it out to +/- 2px), the edge stars seem a little elongated (rotation?).  Sigma 2 stacked and rejected on 1.3px.  Lots of hot pixels coming through (suspect darks are out of date - and not learned to dither yet). Anyone else out last night? was it good or turbulent?

Cheers
Noel
Synta mount, a bunch of telescopes and a shed (on wheels).

Carole

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Re: Leo Triplet
« Reply #1 on: Feb 10, 2018, 18:26:50 »
Well done Noel, nice to see an image from you.

What scope/mount and camera?

A very good effort, but a couple of points, it looks slightly out of focus to me on close inspection.  I think you may be right about rotation, was your PA as good as you could get it?

Carole

NoelC

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Re: Leo Triplet
« Reply #2 on: Feb 11, 2018, 00:12:01 »
Thanks Carol
EQ6R-Pro using an Atik One 6.0 with OAG on an AltairRC8.
Your right; I spent ages focussing in and out; next time will try the Bahti mask, this is at 0.9"/Pixel.
Didn't check PA (set previously using SharpCap), but Dec is see sawing a bit, so will re-check.
Synta mount, a bunch of telescopes and a shed (on wheels).

The Thing

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Re: Leo Triplet
« Reply #3 on: Feb 11, 2018, 08:41:43 »
Hi Noel,
Looks like an image with potential. It rained here most of last night but around 4pm the sky was stunning but I couldn't muster the energy to go out. Must automate the obsy roof...

0.6" RMS is good going, I can get that on my mount if the seeing is excellent. Always use a Bahtinov mask and the original Bahtinov Grabber for focusing, I find that eyeballing or even using FHWM or HFD measurements not nearly as accurate and I can never seem to get automated focusing to work whatever method I try.

I also get a bit of rotation showing up in the corners and my PA is around 2.5' according to PHD2 Guiding Assistant. I thought it was coma on my newt but I've nailed that. I think it might be the fact the OAG is guiding off stars at the very edge of the FoV and this is introducing rotation as it not close enough to the image centre.

For the DEC swings I would check the balance and make it a bit more tail heavy on that axis to counter stiction and gear bounce, I get it after I've fiddled with the scope load e.g. taken off a finder scope and camera and not bothered to rebalance.

HTH

Duncan

NoelC

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Re: Leo Triplet
« Reply #4 on: Feb 11, 2018, 16:39:00 »
Duncan
Your up at 4 am checking the weather - that's keen!

Thanks very much for your pointers, it really helps, my guide star was right in the corner of the chip. 
Looking at it again I have to agree with Carole it looks out of focus.
They are forecasting a clear night, have APT loaded will give it a go....
Synta mount, a bunch of telescopes and a shed (on wheels).

The Thing

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Re: Leo Triplet
« Reply #5 on: Feb 11, 2018, 16:40:43 »
Nah. Taking the puppy out.

The Thing

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Re: Leo Triplet
« Reply #6 on: Feb 11, 2018, 16:43:05 »
Try dithering with apt. Easy. Under the Guide button connect to PHD.

NoelC

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Re: Leo Triplet
« Reply #7 on: Feb 12, 2018, 11:51:47 »
Spent some time on APT (Bhati Grabber works very well) and seemed to be able to repeatably set my focus point on each filter (which was different to the point I set by eye). PA was within 2' az, but 3+ on alt using drift align on PHD (but as I say the stars were moving a bit).  Guiding stats were 1.03"RMS, but results were the same (very blurry subs).

Spent 4 hours achieving nothing and gave up at 01:30 - windy, 0° to -1°, stars jumping around 2".  There seems to be some noise on the guidecam image (Oh no...not again....).

Otherwise a delightful night under the stars - I guess thats it for the month now.
Synta mount, a bunch of telescopes and a shed (on wheels).

Carole

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Re: Leo Triplet
« Reply #8 on: Feb 12, 2018, 13:26:19 »
According to my forecast Noel, it will be clear again Tuesday evening and possibly some clear skies next weekend.

Carole