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Moving up from Skywatcher Star Adventurer

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#1 KevinFH

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Posted 14 June 2018 - 11:23 AM

I dipped my toes into the astro-imaging pond and I want to get into deeper water.   I don't want to dive in to shallow end without knowing how deep it is though.

 

My plan is to follow the advice of many who suggest putting more money into your mount in the beginning and start with a smaller refractor.  I am watching the classifieds for both.  I want a goto capable of a minimum of 30lbs, but I might go for a mount in the 40;b load range.   I like the Orion and Skywatcher models for the money.

 

When it comes to an OTA, I want to increase my focal length a little from the 300mm f4 Nikkor lens I have been using.  I think something in the range of 450mm +/-50mm is about right.  I am thinking no bigger than an 81mm APO.  I have read many good things about some of the doublets, but I would go for a triplet if I can find one priced right.  

 

Here's where I don't have a clear understanding of my OTA requirements:

My camera body, I will be shooting with a Nikon D850, is full frame.  How do I know about the image circles of the scopes?  Some scopes will say, but most leave me guessing.

 

Thanks

Kevin



#2 KevinFH

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Posted 14 June 2018 - 01:10 PM

I am looking at a Williams Optics GT81 OTA.  How can I determine the image circle?



#3 Adun

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Posted 14 June 2018 - 01:52 PM

My camera body, I will be shooting with a Nikon D850, is full frame.  How do I know about the image circles of the scopes?  Some scopes will say, but most leave me guessing.

 

My camera (IMX224) has a sensor with a ~6mm diagonal.

 

I've noticed the TFOV it provides is somewhat similar to a 6mm eyepiece that had a ~50ยบ AFOV

 

Edit: There are also useful calculators here: http://astronomy.tools


Edited by Adun, 14 June 2018 - 01:57 PM.

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#4 KevinFH

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Posted 14 June 2018 - 02:12 PM

Thanks Surveyor 1

I emailed WO to ask them about scopes I am interested in.  




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