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Old 17-04-2019, 08:27 AM
Paulyman (Paul)
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Location: Unanderra
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Read the damn manual

I had an extremely successful Monday night, where my guiding was by far the best and most consistent ever and the new auto focus made focus a breeze throughout the night. I managed a Ha image of the Lagoon and Trifid that I am most pleased with, posted in the beginners forum.

Tuesday night was the polar opposite. It took about an hour to get polar aligned and in focus thanks to the one bank of cloud in the whole sky that just stubbornly sat over Octantis. Finally swung over to the Tarantula but guiding was not playing nice, for the most part guiding was sub 1Ē rms but unlike the night before there were large swings in the dec access every now and then which put me up and sometimes over 1.5Ē rms. But this is just the unpredictable life of a HEQ5 user I think.

The story really goes sideways when after 2 hours I noticed the focus was progressively getting worse after each 600s frame. Now I had painstakingly taken notes about temperature and focus position the night before so that I could work out how to setup the internal temperature compensation and I had set that up before starting the run. I stopped imaging and attempted to swing to Alpha Centauri to refocus. The RA axis obliged but the DEC axis didnít. Okay so I attempted to park the scope and nothing. After an hour of computer and mount restarts, no joy. EQMOD could manually slew the axes but would not slew to coordinates I have it or park to home. I also noticed my battery pack was showing less than 12v even though it was charging while running everything! So I packed up in defeat and tried not to stew while also trying to sleep.

This morning I set everything back up and all was playing nicely, of course... Well at least it is nothing major. The only thing that changed between nights was the temperature compensation so it must be that. I had set it to move 12 steps with every 1 degree change in temperature... except I hadnít. On re reading the manual I had actually set it to move 12 steps for every 0.1 degree change! That explains the loss in focus. Given the focus motor was apparently constantly moving 12 steps in and out during the more rapid temperature drops of the early evening that also hopefully explains the power drain and subsequent mount connection issues.

Crossing fingers and next time reading the manual more closely.

Last edited by Paulyman; 17-04-2019 at 08:33 AM. Reason: Spelling
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  #2  
Old 17-04-2019, 11:36 AM
Startrek (Martin)
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Join Date: Dec 2017
Location: Sydney
Posts: 1,364
Paul
Donít be too crazy about your guiding figures, my images are the same at 0.90 arc sec error as they are at 1.50 arc sec error after 5 minute subs
Sub 1 arc sec guiding is excellent and 0.50 arc sec guiding is in unbelievable
Seeing conditions make all the difference
I was guiding on Friday night t 0.83 to 0.90 arc sec with my 8Ē f5 wind sock with nearly 14 kg on board only because of seeing conditions. The next night back to 1.30 to 1.50

My focusing is primitive but it works for me, I use the FWHM read outs on BYEOS. I avoid bright stars and always pick a dimmer star at 1.80 to 2.50 magnitude and stand there for 2 minutes tweaking the focuser until I get the lowest reading , then take a 30 sec test image to confirm
Never used a Batinov mask
Your producing some really nice images
Cheers
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  #3  
Old 17-04-2019, 07:36 PM
Paulyman (Paul)
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Location: Unanderra
Posts: 99
Thanks for the compliments Martin much appreciated. I agree it’s not about the numbers, I was more concerned with the random excursions of the dec axis given the majority reasonable guiding.

Good news is the system is working tonight. The dec axis was still playing up. But I realised I was wrong, I did make another change yesterday. I added a 3 port cigarette lighter adapter with USB charging ports to one side of the scope. Sacrificing a sub I just went out and moved it onto the tripod. Instant improvement.
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