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I'm aiming for the best possible field illumination for my Explore Scientific PN208 f/3.9 imaging newtonian. The scope is 5 years old now and while doing maintenance I wanted to do something about the design flaws as well.
With the current secondary holder design it's impossible to center the mirror beneath the focuser. My question is: is this really an issue when the entire primary is visible? I read about optimal field illumination when the secondary is centered, but this isn't achievable with this telescope.
I attached an image showing the (very bad aligned and already degrading) secondary at the moment. This is as far down as I can go, I would need to replace the holder screws with longer threads to go further but I don't know if it would make any difference for field illumination?
Thanks in advance,
Hello, I am having a problem with a relatively expensive flat field eyepiece in a combination with a newtonian reflector. I am unable to achieve proper focus with that eyepiece because when I focus it on axis, the edges are blurry. When I focus it at the edge, the center field is out of focus. I don't want to mention the concrete type of this eyepiece because I received it with a spot on the bottom barrel, therefore I cannot be sure whether it has been dropped. This eyepiece has very good reviews on this forum. Optically it looks good and there is no rattle. My question is whether these flat field eyepieces are usable with newtonians as these telescopes doesn't generally suffer from the field curvature. Many thanks for help.
By Anthony RS
I'm selling my my 70mm secondary mirror I used with my 150mm F4 newtonian for 100$ (final price). Shipping expenses (from Beirut, Lebanon) on me for free provided I use LibanPost for shipping. We can discuss using other shipping methods and maybe splitting the cost.
The mirror is brand new, still have the original package and box, bought the telescope a month ago and used only twice. No scratches, not even dust (images attached). Excellent mirror, no issues whatsoever, 94% reflectivity and optimized for the offset of f / 4 Newtons, but it can be used up to f / 5. It's from TS, made in Taiwan, original price is 134 euros (including VAT) excluding shipping and custom fees. Link below:
It does not come with the tilt screws and center screw though unfortunately.
I can also sell you the spider vanes (1mm thickness) for 6 inch newtonian for 25USD. Also brand new but without the tilt screws and adjustment screws. https://www.teleskop-express.de/shop/product_info.php/info/p11056_TS-Optics-Spinne-fuer-6--Newtons---164-mm-bis-180-mm-Tubus-Innendurchmesser.html
Let me know if interested.
<private email address removed>
Having previously got some reasonable images by mounting a smart phone to the eyepiece. I thought I would try for a more sophisticated set up.
So last night I tried to get some pictures of the moon using a Canon Eos D450 connected to a Skywatcher 130p Newtonian via a T2 connection on the eyepiece holder.
As the camera has automatic focusing built into the lens I thought I would have to adjust the focuser on the eyepiece holder to manually get a sharp image.
Basically the telescope acting as a manually focused lens for the camera.
But no joy, I just got a bright light which seemed to fill the camera view finder. I tried various settings on the camera, adjusting ISO and aperture etc, I also had some extention rings for the camera lens so tired fitting those to extend the focal length but no better.
I sure there are many palms being slapped against foreheads reading this but as you can tell I have no idea, although I do have some of the gear.
Any pointers and/or advise would be gratefully received.
Hi, I recently looked into telescope's & dso's again due to an interesting sight in the night sky 😉.
I wanted to get into telescope's etc... but my budget and other things got in the way.
This time there's no budget limit (that doesn't mean I'm bill Gates though).
My main concern is size since I will carry the telescope with my bare hands (bag).
I don't have a local astronomy club or telescope shop around so I don't know if an 8" Newtonian is too bulky/big.
Can someone post comparison pictures, if you have an 8" telescope (preferably newtonian, width and length)?
Secondly I want to see dso's in the future (firstly beginner objects etc...) so the 8" is more adequate than the 6", but if an 8" is too big then I am okay with a 6" as long as it's much more portable.