Telescope or telephoto lens - advice / recommendation welcome

Started 2 months ago | Questions thread
EricTheAstroJunkie Contributing Member • Posts: 821
Re: Telescope or telephoto lens - advice / recommendation welcome

Focal length is not your friend with a lightweight, portable tracking mount like the Star Adventurer. You MIGHT get lucky and have a decent copy of the mount with periodic error less than 40 arc-sec and you MIGHT be good enough to get great polar alignment and great weight balance such that you can execute exposures in the 2+ minute range with a telescope/lens that has a focal length above 200 to 250mm, but realistically you won't for any of those. So, stick to K.I.S.S. and maximize the capabilities of your mount, which is by far the biggest factor for getting high quality astro images. A mount like the Star Adventurer is designed and engineered to offer portability and reasonable performance (accounting just for periodic error, not even all the other issues like a lack of motorized declination axis) up to ~200 to 250mm focal lengths. Going longer in focal length will highly restrict your exposure lengths and will result in a higher percentage of tossed out exposures due to tracking imperfections (not to mention the frustrations with things like target framing). Going longer will require a guiding setup to get the most out of your mount which will add cost and complexity.

So having said that, a scope like the Redcat or something like a Sharpstar 61EDPHii is ideal for your setup, they will connect easily to your camera, offer easy to use focusing mechanisms, are lightweight with good image quality with minimal aberrations and at very reasonable prices. Obviously supply might be an issue, with COVID comes HUGE supply shortages everywhere, but take a look on the used classifieds at cloudynights (and post a wanted ad). I highly recommend passing on the zoom lenses, I've used them, they are big and bulky, they offer shortcomings like zoom creep and front heavy glass, sometimes aren't well corrected for coma/LoCA, and really don't give you much beyond the flexibility of alternative uses besides astro. Astrophotography is an insanely demanding type of photography, shortcomings become immediately obvious during exposures and when you stack a ton of exposures you see those shortcomings really stand out.

So, a scope in the 250mm range is really ideal for the Star Adventurer, they are reasonable weight, with practice in polar alignment and weight balance you can get a good keeper rate without guiding, are reasonable in price, and have good to great performance (apertures in the f4 to f4.5 range with minimal aberrations and good to great sharpness). You'll learn over time that astrophotography demands certain tools for certain purposes and if you want really really good results you need to maximize your capabilities with those tools and understand their limitations based upon their purpose build. Small tracking mounts can deliver fantastic results bearing in mind their build limitations, so work within those confines and get the most out of them.

 EricTheAstroJunkie's gear list:EricTheAstroJunkie's gear list
Nikon D200 Nikon D7000 Nikon D800E Nikon D5300 Sony a7S +14 more
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