Meade provided me with an unusual telescope for testing – the Meade 70mm f/5 ED quadruplet apo astrograph. This is a four-lens (quadruplet) apochromat telescope with a built-in field flattener. The use of low-dispersion glass FPL-53 and a working field with a diameter of 42 mm are declared. The main convenience of the quadruplet is that you don’t have to select the backfocus. All you need to do is connect a camera to the telescope via a T-ring or an astronomical camera and get focus. The special features of the telescope include its exceptional photographic directivity, since due to the short travel of the focuser it will not be possible to focus with the diagonal mirror and eyepiece installed. Additionally, there is no visual adapter or eyepiece included. That is, it is only a photo telescope. However, I managed to make it work with the eyepiece, and I will also talk about it in this review.
The telescope is supplied in a case measuring 40.5 x 25 x 18 cm, which reliably protects the tube from damage.
– optical tube in rings with mounted mounting plate
– metal covers for the lens and focuser
– adapter M48-M42
A few measurements:
Optical tube length: 320 mm
Width: 160 mm
Hood outer diameter: 88 mm
Hood travel: 44 mm
Focuser travel: 32 mm
Lens light diameter: 70mm
Light output diameter: 44.5 mm
Weight of tube in rings with covers 2.28 kg
Tube weight with suitcase: 3.9 kg
Focuser 2.5-inch, two-speed with helical rack. The focuser handles are metal, ribbed. It is possible to rotate around the optical axis. The outlet thread is M48. There is a slight lateral play when rotating the focuser tube.
The lens is fully coated, the coating color is green. Lens adjustment screws are hidden under the hood, but custom adjustment is not provided and is not recommended.
There are several lenses inside the pipe that perform the function of field flattering. They are rigidly fixed inside the tube relative to the lens and do not move with the focuser.
How to connect a camera to a telescope?
You will need an adapter ring from the M48 thread to the camera mount (for example, M48-Canon EOS). It is especially recommended to use the M48 ring for full frame cameras to reduce vignetting.
For cameras with a smaller sensor size (for example, APS-C format), you can use the included M48-M42 adapter in connecting with a T2 ring (M42x0.75>camera mount).
Where do you screw in the filters?
When using SLR cameras, I used clip-on filters, which are installed directly into the camera between the sensor and the bayonet mount. When using astronomical cameras, you can use adapters or adapters with the necessary thread for a filter, or a filter wheel with a T2 or M48 interface.
What’s in the stars?
On-axis sharpness is excellent and diffraction limited. The field is large, but the stars at the edges of the field of view are not entirely even, they look like small comets with their tails inward. Chromatism correction is good, although there are small halos of residual chromatism.
Example frame with a Canon 550Da camera (APS-C format sensor):
Flat field frame. No vignetting!
Example image from a Canon 5D MK II full frame camera:
Flat field frame:
There is little vignetting, even on a full-frame sensor. Great!
Test frames in RAW format from Canon 550Da and Canon 5D MK II cameras, including those with various filters, are available here.
What mount is suitable for this telescope?
The optimal mount for this telescope would be a heavy-duty equatorial mount – such as the Meade LX85. In one of the configurations, the telescope comes with this mount. She carries an optical tube with a large reserve.
Although the telescope was originally designed to photograph deep space objects, it can also be used to photograph the Sun, Moon, and planets. For this task, you can use any alt-azimuth mount with GoTo and a load capacity of up to 4 kg. When photographing the Sun, be sure to use ONLY an aperture solar filter. It will not be possible to focus with a Herschel wedge due to the slight offset of the focus point.
How to observe through it?
For visual observations, you will need a visual adapter with an M48 or M42 thread and an output of 1.25 inches, a 2x Barlow lens, a diagonal mirror and an eyepiece. Screw the visual adapter to the telescope, insert the Barlow lens, the diagonal mirror, and then the eyepiece. Turn the focuser knob to get a clear image and begin observations. It is also possible to focus with an eyepiece without using a Barlow lens and a diagonal mirror – insert the eyepiece directly into the visual adapter, but then observations will be uncomfortable due to the lack of a bend in the optical axis.
Lightweight and compact astrograph telescope with built-in field straightener. Great for deep sky photography. With an optional visual adapter, diagonal mirror, Barlow lens and eyepiece, it can also be used for visual observations.
Examples of processed images obtained with the Meade 70mm f/5 ED quadruplet apo telescope.