Focal length Vs F stop Meade 90

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AnthonyGraham Forum Member • Posts: 75
Focal length Vs F stop Meade 90

Thank you all in advance for your help and opinions.

equipment being used


Meade 90mm old one 20 years plus

prime focus adapter with and without extension tube

NO auto trackerĀ  Here come the issue

Target --  Orion Nebula plan on using stacker program and photoshop and lightroom

My question is...

Since I am not using an auto tracker .

1. Use the prime focus adapter without the extension tube at 1250mm F 13.8..


2. Use extension tube and shoot at 1450mm at F16..

I'm trying to balance the rule of 500 with zoom and ISO

Basically is it better to be 18% closer and loose the F stop and have to drive the ISO up or stay at 1250 and be 18% further and have a lower ISO and tiny I know very tiny longer exposure?



 AnthonyGraham's gear list:AnthonyGraham's gear list
Nikon D5600 Nikon AF-S Nikkor 14-24mm f/2.8G ED Nikon D100 Nikon D200 Nikon AF DX Fisheye-Nikkor 10.5mm f/2.8G ED +6 more
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Nikon D5600
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