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Marin

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  1. They aren't really triplets, if my memory dosen't lie to me; they are classic cemented doublets + one negative lens as flattener in front of prisms. They should provide better definition at the edge of the field but I presume it would be a nightmare to collimate.
  2. Thank you for sharing and please do try to get hands on a full frame camera, while the quality across a crop sensor is great we need to know how well it performs on larger sensors. For pixel peepers, here is an image of double cluster i took with my Fuji xt-4, 10x1s stack.
  3. @heliumstar: Yes, I use it on EQ mode but with the original tripod. It's OK for visual, for photos I'm still on research about what mount to buy. The images were selected from a pretty large pile of mostly useless ones. @Chris: Thanks, I thought there is not much information out there about this scope and some might find my finds useful.
  4. After almost three weeks of bad weather, last evening the seeing cleared up for a few hours so, after showing it to the stars, i can share my thoughts about the 90mm Stella Mira triplet. I am into astronomy since childhood, my first telescopes were build by myself using spectacle lenses and cardboard sheets and they were terrible; finally, eight years ago I bought my first real telescope, a 4.5" reflector and... you all know where that kind of thing leads. For the last three years my main tool is an 8" dob with excellent optics and is covering most of my needs, but is hassle to move outside the yard so I started thinking of adding something more portable to my collection. 90mm seems to be the maximum aperture for a light weight refractor that can be used mainly for visual observation and some photo experiments. The Stella Mira 90 EDT seemed to tick all the boxes so, within two hours since the official announcement, the order was placed. Next Tuesday, the boxes containing the telescope, the reducer/flattener and the camera adapter landed on my workbench and I spent five agonizing hours before reaching home and finally taking a glance at the black beauty. The built quality is excellent, with touching attention to details like the snug fit of the tube rings or the small bumpers that prevents the dew shield from getting scratched. The 2.5"diameter long travel focuser was the giveaway that the telescope is intended mainly for visual use but, to my surprise, don't cut away much of the light path; even using the reducer is not much darkening towards the edge of a 44mm light circle. The objective lens looks like a Hastings triplet, the adjacent surfaces of lenses have the same curvature so you will see only four reflected images but the lenses don't seems to be cemented, you can clearly see the inner surfaces are anti-reflex treated. Oil spaced, maybe? I popped in the reducer and my Fuji camera and took some pictures of a tree waving in the wind. While it was moving quite energetic, some twigs came in focus so I could evaluate the resolution and the amount of C.A. The image is sharp across the whole 28mm circle of a crop sensor and, even with aggressive processing, you'll see fringing only on out of focus parts of the image and is easy to remove on post processing. There is a caveat: the dedicated astronomic cameras are sensitive to a larger spectrum of light so you might feel the need of a UV / IR cut filter. I also tried it visually on the first decent seeing night and it performed over my expectation: the field curvature was inducing some artefacts towards the field stop of the eyepieces - you'll want some quality ones for wide field view - but adding a barlow lens changed things. Jupiter showed an unexpected amount of detail despite the turbulence, it outperforms my 5" mak by a thin margin. Last night the seeing was finally good so I tried to make the final tests. As the AZ-GTi mount was misbehaving, the telescope had enough time to reach thermal equilibrium so the pictures taken could be considered representative for its quality. In the end I performed a star test and, while the intra focal image was slightly more contrasty than the extra focal one, they showed no darker regions and I was surprised by the small amount of CA. In the end, is not a cheap telescope but delivers for the money, all I can count as "not perfect" would be the storage case - not solid enough for transport and the feel of the focuser - the fine adjust knob is a bit springy, tends to push back but this is maybe just me.Just after deliveryUnpackedThe image circle with reducer/flattener1:1 bottom right corner, originalSame, agressively processedAuto defringedDouble cluster 2x2 binned and cropped ISO 3200, 7x1secBottom-left corner of original image1x30s ISO 3200 binned and cropped
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