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Celestron Regal 65ED M2
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Celestron Regal 65ED M2: My review
It's about two months that I'm playing with a Regal 65ED M2. Yes, it's a spotting scope, a well-made one, not too expensive and compatible with standard 1.25" eyepieces. Here my impressions.
A spotting scope is a refractor plus a 45° erecting prism in a rugged and lightweight package: nothing prevents to point it at the sky. However, the 45° prism is not as comfortable as a 90° star diagonal to observe (but it is much better than a straight through binocular), there is no (easy) system to add a finder or a red-dot and you are limited to 1.25" eyepieces. I think a spotting scope excels if you need a travel, sturdy, grab&go refractor to be used for both nature & sky observations (even if the sky part will get most of the use).
How small all the package (tripod + scope) is. The ES 5.5mm 62° is for comparison]
Specs A 65mm ED spotting scope, with internal focusing and a magnesium housing. Sort of mid-quality zoom: 40°- 62° but with a large eye-lens and a much better eye-relief than the cheap models (20mm spec, can be used with my not-too-thick glasses). Need refocusing when changing magnification. Weight is incorrectly specified: a bit more than 1600gr, and not the stated 1327gr.
The scope has a major mechanical problem: it is back-heavy and it cannot be balanced with a short dovetail. The unbalance is severe, and it makes challenging using the scope on whatever mount, unless with a payload (and weight) that largely exceeds the scope's one. However, the problem can be solved. You need at least a 15cm long dovetail (I use an Arca Swiss one). Luckily, the dovetail can be fixed to the scope using two thumbscrews, so it stays firm once fixed.
The scope with the long dovetail bar
Note (i) the two thumb-screws to connect the scope to the dovetail
and (ii) how far back the clamp locks the dovetail
Changing eyepiece is not as easy as in a traditional diagonal. There is a self-centering ring and, once you have turned it, some force should be used to pull-out the eyepiece. I think that's normal, as in that way all the system remains waterproof (there is at least one O-ring where the eyepiece is inserted).
Very nice the metal made "case" for the eyepiece, which screws directly on the scope’s body and fully cover the zoom eyepiece (and whatever smaller eyepiece you put there).
The back part (diagonal + eyepiece) can be rotated. Hence, it is possible to mount the scope on a ball-head (see below).
I have tested:
1) The zoom eyepiece (it is obviously compatible). Works best up to 30x (more or less), then the image gets softer.
2) Wide field. A 16mm 68°, for (almost) 24x and 2.85° FOV. It focuses at infinity. This FOV is greater than the maximum FOV provided by the zoom eyepiece (2.5° @16x). All the field is illuminated (I have tested it using two stars with a separation slightly greater than 2.8°). However, there is some vignetting: the edges are not as bright as the center. As I can detect it visually, the vignetting should be equal or greater than 20%. If someone has the same scope and it can test a 20mm 68° or something similar, I would love to see the results. I guess the scope can arrive at least up to 3°, more or less
3) Max magnification. I have tested a 5.5mm 62° for (almost) 70x. It works as it focuses at infinity and the image is usable. Not so good on low contrast targets like Jupiter (but Jupiter always wants low mags w.r.t. the scope diameter), very good on the moon (the moon is entirely framed, barely) and on bright stars.
In another discussion, someone suggested that "If your spotting scope has a collar ring that can be rotated by 90 degrees then a 36-44mm Arca-Swiss ballhead used in alt-az config (rotated into the notch) is solid and cheap."
I agree. I bought a relatively unknown Chinese tripod on Amazon, and it works perfectly up to 70x magnification. With the long arca swiss plate I have, I can perfectly balance the scope. Movements are fluid and I do not have to lock the ball to fix the scope in a given position. The ball head (a clone of the Benro B1) has the main lock and a friction adjustment, plus the pan lock.
The friction adjustment (which is gradual and works as you can expect) is useful. You do not need that when the tripod is perfectly levelled on a flat surface but, as my garden is not flat, when the tripod is not levelled it's useful to have a small amount of friction. I do not have that on the pan movement and, as a result, sometime there is a little slip (The pan-lock is a sort of on-off).
Very good. Star test using the zoom eyepiece at about 30x is surprisingly good (at least at the low magnifications used). Intra and extra focal images are similar, the diffraction concentric rings can always be seen.
The scope is collimated (checked with a cheshire).
Flashlight test: the scope works at full aperture (65mm). NB: the 65mm is an f5.9. The 100mm has a more obtuse light cone at f5.4, not sure if that might stop down a little bit the aperture of its bigger cousin.
The scope (and/or the zoom eyepiece) is very sensitive on your eye's position: if it is not perfectly perpendicular, it introduces some CA. If the head is perpendicular, CA is low (at relatively high magnifications) to almost non-existent (at low magnifications). This effect can clearly be seen on Jupiter for example: if the head is not perpendicular and at 48x with the zoom eyepiece, there is a light violet halo on one side of the planet which disappears when you put the head in the proper position: I have never seen such thing before. PS: on Jupiter you can see NEB and SEB plus the 4 satellites, and the zoom at 30-35x is better than the ES5.5mm at 70x.
Star test #2
I checked again the star test, using the ES 5.5mm 62° at 70x. I confirm the scope is collimated. No color in focus using a bright star. Both inside and outside focus, the concentric rings can be seen, even close to the optimal focus position. Here, the external concentric disk is thicker. There is a very slight green color inside focus. Overall, IMHO the star test is good, especially for a spotting scope.
Very good. No CA (at least for normal targets, I have not tried to look at antennas or similar things, more at birds, trees and landscape).
Very comfortable to move around on the tripod. For daytime, I only use the zoom, it is not convenient to change the eyepiece every time. I still have to do some serious birdwatching with it.
There is at the moment a heated discussion on Cloudynights about spotting scopes. I can only confirm my initial impressions: for a dual day&night scope, a good quality spotting scope is, IMHO, a very good choice. The scope performs nicely also for astronomy, and not only for daytime use. I do not agree with people that says a spotting scope cannot be used for astronomy.
It is true, a 60-72 ED doublet with a 45° erecting prism and a zoom eyepiece can also be used for daytime observations, and of course with a 90° star diagonal it is more comfortable during the night.
1. I know they exists some very expensive astro-quality 90° erecting prism, but I do not know of very good quality 45° erecting prisms which can be used with a telescope. The risk of losing optical quality in daytime is there.
2. A telescope is less robust, heavier and not waterproof. For daytime use those are important weakness.
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