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Re:M31

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M31 was created by Mohamed




PS: Will try mosaic next time as my f/6.3 cannot get the whole galaxy in one shot. Also, my 1st attempt with PixInsight


Processed with PixInsight (Pleiades Astrophoto)

ISO 800
Lights (filter Luminance) 14 x 300 sec
Darks 30 x 300 sec
Flats 50 x 0.05 sec
Bias 30 x 0.00025 sec
Total lights integration time 1:10 hours

Date Wed Oct 7th 2020
Seeing 3 / 5
Transparency 3 / 5
Sky Darkness #4 Rural/suburban transition - 6/9
Binning 1x1
Last edit: 3 years 5 months ago by Mohamed.
3 years 5 months ago #61445
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Replied by Gonzothegreat on topic M31

I use the tutorials from www.lightvortexastronomy.com/tutorials.html which are great.
Your stars look slightly bloated, have you use the autofocus or is it manual focus?
3 years 5 months ago #61453

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Replied by Mohamed on topic Re:M31


Thank you for the tutorial link. I shall spend the next few weeks on it...

I always use autofocus, unless I’m severely out of focus, or checking collimation, then I use auto focus again.

I shall be installing the Rowan belt mods after I get back from my trip and hopefully it will help tracking...


Thank you
Mohamed
3 years 5 months ago #61519

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Replied by Jose Corazon on topic M31


Agreed, they are out of focus.

Are you using the Linear or Polynomial focuser?

If your autofocuser has a backlash problem, the Linear focuser will take care of that, the polynomial won't. I had the same problem and it went away completely with the Linear focusing algorithm.
3 years 5 months ago #61521

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Replied by Mohamed on topic M31


I didn't change any of the options, so I guess it is the default. My focuser is the JMI MotoFocus+ Celestron C8 (farpointastro.com/shop/jmi-motofocus-celestron-c8/), and I don't know if it has a backlash or not...
3 years 5 months ago #61525

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Replied by Jose Corazon on topic M31


That's an analog focuser and yes, it has an enormous problem, which is caused by the differential loading of the motor when it is focusing in vs out. Those analog focusers will not yield a good focus with the polynomial focuser. I know from experience. I have the same one on an RC8.

Use linear. It will still not completely correct the problem, but it will get you there. You need a stepper driven focuser. Especially at that focal length. The focal plan is exceedingly narrow there. That requires precision an analog focuser just can't deliver.

Those analog focusers are good for visual observing when using a manual hand controller for the focus, not for automated focusing for astrophotography.
3 years 5 months ago #61526

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Replied by Mohamed on topic Re:M31


Now that make sense. I’m having hard times using the auto focused and in my last session I had to perform focus manually and adjust by autofocus.

Any recommendations for good auto focuser for the c8 that works with C8?


Thank you
Mohamed
3 years 5 months ago #61527

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Replied by Jose Corazon on topic Re:M31

In short, you need a stepper driven autofocuser with a strong motor, like a NEMA17. That should have no trouble pulling the weight of your light train when connected to the fine focus knob.

You can build one yourself, using for instance the MyFocuserPro instructions and the MoonLite Driver (as many others here have done as well) or you could buy a MoonLight focuser (expensive) or a Pegasus (some people I know have one and they are happy with it). Either way, I messed around for 2 years with analog focusers and since I put a stepper driven autofocuser together, all my stars are tack sharp in focus. No more bloated stars. Now I need to build one for my RC8 and for my ES102.
3 years 5 months ago #61528

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Replied by Mohamed on topic Re:M31


Thank you for this tip. Everyone I learn something new that make this hobby more interesting:)

The instructions I found online so far pretty old (2-3 years at best). Any reliable source of building it that include all required components and steps that you advise for a beginner like myself?


Thank you
Mohamed
3 years 5 months ago #61530

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Replied by Jose Corazon on topic Re:M31

indilib.org/media/kunena/attachments/4350/SolderlessFocuser.pdf

That’s the one I built. Pretty simple. I still ended up soldering everything to a Vero board, but it worked immediately. Use a standard NEMA17 Stepper motor (<$10) and DRV8825 controller. You can get them all from Amazon.

That’s what the prototype looked like:

indilib.org/forum/focusers-filter-wheels....html?start=48#54478


The electronics is actually the easy part, fitting the motor to the fine focus knob if your telescope requires more tinkering. That’s where having access to a 3D printer is priceless. I designed and printed all the brackets I needed.

But as you say, this is a rewarding hobby and you learn lots of different things all the time.
Last edit: 3 years 5 months ago by Jose Corazon.
3 years 5 months ago #61537

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Replied by Mohamed on topic Re:M31



That's Awesome!!! Thank you so much...
3 years 5 months ago #61599

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