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M16 Eagle Nebula: first light with a Mach2 mount

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I have a new mount, an Astro-Physics Mach2. It is supposed to be installed in my future observatory. But the observatory construction has not yet started as Covid19 has slowed down the approval process substantially. Of course the new mount and a buddy finishing his observatory (no approval necessary for him - lucky [removed word]) has brought us torrential rain. We need it so I won't complain.  On Monday it looked like a clear week was coming up, so I put the Mach2 outside on the Eagle pier. Since I am familiar with the Astro-Physics mounts and software this went without a surprise. But I always guide - until now that is. I wanted to try unguided imaging with a pointing model. 


The first evening I played around building a model and taking some unguided subs. The subs looked rather bad, elongated stars although Sharpcap reported perfect polar alignment. But on closer inspection I noticed that after slewing to a target close to the meridian, I was off more than I had expected. My precision or rather lack of it was not good enough for unguided imaging. Being perfectly polar aligned at the pole does not mean I am perfectly polar aligned at my target! I gave up around midnight and did some calculations the next day. Drift rate as a function of polar alignment error, what an eccentricity tolerance of 0.42 meant in terms of drift rate etc. etc. I will spare you the details but the result was clear. If I wanted nice stars I would need to dramatically improve my polar alignment. 

The second evening I worked until 21:15 to get a good polar alignment with the added help of PEMPro. The model was ready at 22:00 and I had a great hour imaging before it got too moist. 

The third evening I was getting better. At 20:15 I had a good polar alignment and a 50 point model running! I captured some nice data, before a fog layer emerged like a screen over the city at 22:00. 



Eagle Nebula, 60x60s Red, 45*60s Green, 26x60s Blue, 130mm APO @ f/4.5, A-P Mach2 unguided

Higher Resolution Image

First impressions:

Polar alignment, balancing and HW setup must be very precise for unguided imaging. 

Unguided imaging produces very nice stars when it works. 

For a non-permanent setup getting perfect alignment and a good model consumes valuable imaging time and it is probably smarter to choose guided imaging.

Imaging unguided with a model means you have nothing to do after setting everything up. With guiding, you can watch the guide graph (I do) and contemplate tweaks to improve RMS etc. With the model, nothing happens. You can watch SGP but its rather uneventful. Rather watch a cosmology lecture on YouTube.  

I could use 95% of my subs, no bad subs due to big jumps in FWHM or eccentricity! 


I like this mount and I think we will become very good friends. 


Clear skies,


Edited by Camissa
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Good write up and a great image. 

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