Is there a some way to determine how much back-focus a Newtonian will need to to achieve focus based on it's specs, I was looking at a Meade FS85 6" Newtonian, focal length is 750mm with
Thanks for any thoughts, this newbie thirsts for knowledge!
The other was an 8" celestron, the one I'm looking at now is a 6" Meade. Yourr answer on the celestron prompted the question. So it's the physical position of the mirror that's the issue.SkyHiker wrote: ↑Tue Feb 23, 2021 7:10 am Extension tubes do the opposite of what you need. A mirrorless DSLR will have a better chance of reaching focus especially if you can get a T minus adapter for it. Aside from that, try longer primary mirror screws to move the mirror up. A CC will not fit on that Newt, I think I mentioned that earlier.
I'm looking at the TPO 2", https://optcorp.com/products/tpo-2-Piet Le Roux wrote: ↑Tue Feb 23, 2021 7:07 am I dont think there are but if the coma corrector states that it needs at least 55mm it would depend on how much travel your focuser has, if your nomal focus point is midway with a focuser that has 50mm travel then you have a maximum of 25mm in and out focus. Normally a barlow needs back focus and a reducer needs in-focus, both Celestron and Meade makes a comma corector/focal reducer. What comma corrector/reducer are you looking at?
Ah my bad yes that was the 8". I wonder if you should slow down a bit and learn how to use the AVX first, or otherwise move up to a larger mount. It is easy to spend a lot of money then have to upgrade and lose money on the old gear. One of the best APers is Kathy, she has been using a cheap 8" astrograph with a Paracorr 2 forever, shooting great images. It convinced me to order a 12" Newt astrograph, I have the Paracorr 2 already. There are big quality differences between CCs so you may and up spending a few $100 on one then have to upgrade later. It's like motivating spending money on an 8" Newt by comparing what you would have spent on some other mount. It adds up. When you mention a ZWO, realize that the cheap ones give you a smallchris_g wrote: ↑Tue Feb 23, 2021 8:31 amThe other was an 8" celestron, the one I'm looking at now is a 6" Meade. Yourr answer on the celestron prompted the question. So it's the physical position of the mirror that's the issue.SkyHiker wrote: ↑Tue Feb 23, 2021 7:10 am Extension tubes do the opposite of what you need. A mirrorless DSLR will have a better chance of reaching focus especially if you can get a T minus adapter for it. Aside from that, try longer primary mirror screws to move the mirror up. A CC will not fit on that Newt, I think I mentioned that earlier.
I'm set on a fract setup forAP but was wanting to add a newt since I can get a discount on the tube in a package with the mount. The Newtonian would be for visual but if I can take pictures with it so much the better.
You mention a mirrorless, I'd eventually add one to the rig but the next camera will be something along the lines of a ZWO. Would I have the same issue?
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