* Astronomy

Members Login
Post Info TOPIC: Meade #930 2" Diagonal


Posts: 130085
RE: Meade #930 2" Diagonal

As a follow up on last weeks review, the 2" Meade #930 90-Degree Mirror Diagonal has proved to be excellent at doing what it's supposed to do - it delivers bright, clean, flat and undistorted views. But not anything more than a comparable 1.25" diagonal that was obviously discernable to my eyes.

The all metal (rather than polycarbonate) body is well constructed and can support heavy eyepieces, or D/SLR cameras, without flexing.

Testing with a standard 1.25 inch 40mm Plossl eyepiece provided clear edge-to-edge pinpoint images without any edge darkening. But the Mirror Diagonal is quite capable of delivering panoramic views with 2" wide-angle eyepieces.

A small note is that the standard eyepiece adaptor on Skywatcher/Helios refractors (should you wish to use it) have a deep bevel and cannot be secured with the rather short single locking screw on the diagonal; luckily the locking screw has the same thread as the flexible slo-mo controls, and can be simply swapped to stop any looseness, (The Diagonal does come with a standard 1.25" eyepiece adaptor).



Posts: 130085

Meade #930 90-Degree Mirror Diagonal (2") 

The #930 Meade 2" surface Mirror Diagonal with UHTC coatings is designed to be used with any Meade LX series telescope. This diagonal is compatible with any refractor having a 2" focuser and held in place with a grub screw. The #930 also works with the #1209 MicroFocuser installed on a SCT. 
Mirror Diagonals, or Star diagonals, render images which are upright but laterally reversed and allow the eyepiece to be placed at a convenient angle for viewing of astronomical objects.
The Mirror Diagonal 2" barrel attaches to the Focuser allowing for the use of wide-field 2" eyepieces.  An important (negative) point is that the barrel is not recessed to stop the diagonal from slipping out of a standard refractor focuser.  The Diagonal has a simple locking screw, rather than a compression ring. The diagonal will also accept 1.25mm (1-1/4") eyepieces (using the included 1-1/4" adapter).

The optical-flat mirror is of Pyrex glass, and is UHTC (Ultra High Transmission Coatings) coated. The enhanced aluminium, multicoated with layers of titanium dioxide and silicon dioxide, increases the mirror reflectivity to 97%, compared with the 89% reflectivity of a standard aluminium mirror.
The Diagonal is threaded to accept standard photographic, or astronomical application, 48mm filters and the interior is matte black for increased contrast. 
The weight of the Diagonal is a rather hefty 545g, which may lead to balancing problems with small telescopes.

The 2" only offers a wider field of view with 2" eyepieces


Ed ~ So the most notable aspect is that this is a 2" diagonal allowing the use of low powered wide angle eyepieces without vignetting of the view (ie increases the maximum possible true field). It should be noted that there is no discernable difference, using similar quality 1-1/4" or 2" diagonals, with eyepieces (up to 40mm) with 52 degrees Field of view.

The UHTC coating is a bonus, as essentially the aluminium surface is sealed under a layer of glass and will not deteriorate or lose its reflectivity. Having said that, it should be noted that only very experienced observers would be able to notice (if at all) any difference between a standard coating and the enhanced UHTC coated diagonal. The difference between this and the even more expensive dielectric coatings (99% reflectivity) is minimal and would be impossible to detect visually. 

Astroptography use of the diagonal is possible, but rather pointless as cameras can be fitted directly to focusers and extension tubes (omitting the reflecting mirror).

The bottom of the Diagonal has four fixing screws which can be adjusted (using DIY paper spacers) for proper optical alignment (ie collimated correctly). 

USD 119.00

See more

Page 1 of 1  sorted by
Quick Reply

Please log in to post quick replies.

Create your own FREE Forum
Report Abuse
Powered by ActiveBoard