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M45 - First Light Astro-Tech AT8i

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Despite being on my sick bed (sick couch actually) I could stand it no longer ... My brand new Astro-Tech had been waiting in the garage for first light since Christmas Eve and now finally clear skies outside with Orion rising over the roof! I swallowed another round of Vitamin I (Ibuprofen) made a cup of tea and put on my ski-pants. -4C outside said my thermometer.

I set up the CG5 ASGT Mount and polar aligned. I left the C8 in its case and put the 8Ti on the mount (with some fiddling) instead. The C8 is very capable but even with the 6.3 reducer its still, well, F/6.3. I wanted to try the fastest scope I could get my hands on. The AT8iN is F/4 and 800mm Focal Length versus the C8 at F6.3 (with reducer) and 1281 FL.

I don't guide as I don't want the extra equipment and time to setup. I prefer to enjoy visual observing then throw my camera on the scope and do an imaging run.

My first target was M45 and this is 10 subs at 60 seconds. Its very noisey at ISO 3200, but I wanted to see how much light I could pull down inside a minute. I'm right under the streetlights on my driveway and the Astro-Tech is ideal for this situation as the secondary mirror is recessed down the tube around 6 inches. There are also several light baffles ahead of the secondary.


I've read that the supplied 35mm extension may not be enough to bring some eyepieces to focus. I found the same thing, but by pulling the 35mm extension part way out (still leaving more than an inch inside the focuser) I was able to focus all my 2" and 1.25" E.P.s. There's no counterweight supplied and my single 6Kg is too light for the OTA. I hung my tool bag over the counter shaft to level things out for tonight.

I wasn't expecting a good view visually, because of the oversized secondary mirror, but I found a great view of Andromeda with my 2" 42mm Skywatcher eyepiece. I could see M31, M32 and M110 all in the same view. Stars were nice and pointy. M42 was also very impressive - the star cloud looked huge. Once or twice when out of focus I could see the dark spot of the secondary, but generally it was not an issue.

I ran some images at 60 seconds and ISO 3200 and I could immediately see the difference from the C8's light capture times. I was pulling down much more light in the same time.

The focuser is solid and precise and the drawtube has two incremented scales for focusing. Didn't use the fan as my garage is also freezing! Collimating was easy and I pulled the primary into line with a few half turns of the dark adjusting knobs. My camera screen dewed up, but no problems with the scope - it stayed clear. A nice advantage as the SCT is horrible for dewing up.

First time out and I'm impressed. Will be interesting to see how it handles high power for the planets. Oh yes, one other thing, the scope weighs around 20 lbs versus my C8 at 12 lbs. Its a fair handful to attach to the mount.

I had a good new year's eve on the driveway in my garden chair with tea in my hand watching the scope, camera and timer snapping away at the sky overhead while I checked out various star clusters with my 15x70 binos - better than watching TV for sure ...

Edited by James4

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Thats a very impressive result for unguided work, stick with it, the noise level does not seem bad at all, unguided work gives you lots of experience before you start guiding. check my site, lots of stuff can be imaged without doing guiding.


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Thanks Nadeem, nice pics on your website - like the M81/M82, a pair of my favourites.

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Like the tight stars with well defined spikes. Looks like the scope is performing well.

Definatly worth some more time it will make an Excellent image.

Well done.

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A couple more pics from my first outing with the Astro-Tech AT8iN:


(Above) A stack of 9x60 second subs from DSS - unguided - Nikon D500 - ISO 3200


(Above) Stretched in Nebulosity2


(Above) My stack of 7 aimed at the Horsehead looked hopelessly blasted by a combination of street light and Christmas lights reflected of my frosty roof ...


(Above) I was quite pleased to pull this image out of the light washed stack. This bodes well for next time out when I'll be more careful in letting Orion rise away from any intereference ...

Overall the F/4 scope showed a dramatic increase capturing DSO over the F/6.3 SCT.

The edge of field stars are quite distorted but I can crop or get a flattener. My main fun right now is capturing these objects on camera when I can barely see them visually because of light poluttion. James

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