StellaLyra · 6-inch f/12 M-CRF Classical Cassegrain
A closer look at the Moon, planets and double stars.
The StellaLyra 6-inch Classical Cassegrain combines a 153mm aperture with an 1836mm focal length at f/12. Its folded optical layout puts a long focal length into a relatively short tube, making it an appealing choice for observers who enjoy spending time on individual targets.
Build the observing kit around a steady mount, a suitable diagonal and a small selection of eyepieces. This is an optical tube assembly, with the freedom to choose those accessories for your own observing habits.
Choose it for the detail within the field.
On the Moon, explore how changing illumination reveals crater walls, ridges and shadows near the terminator. For planets and double stars, concentrate on accurate focus and moments of steady air rather than increasing magnification as far as possible.
The long focal length makes moderate and higher powers easy to obtain with ordinary eyepiece focal lengths. It also narrows the field compared with a shorter-focal-length telescope using the same eyepiece. Think about the targets you enjoy: a whole wide star field and a close study of a lunar feature ask for different kinds of framing.
Give the optical system time to settle.
The open front shows the secondary support and internal baffling. Both mirrors are quartz, but the telescope still benefits from time to approach outdoor conditions before critical observing.
Judge sharpness after cooling and careful focus, with the target well centred. If alignment needs attention, use a procedure appropriate to a Classical Cassegrain and confirm the result on a star. Make small, recorded adjustments so that you can identify what improved the image.
Plan the mount and balance as part of the purchase.
Published tube weight is 5.8kg, with a Vixen-style rail underneath. Add your diagonal, eyepiece or camera and any finder when assessing the complete working load.
At higher magnification, vibration after touching the focuser is particularly noticeable. Choose support that settles promptly, check the saddle fits securely and balance with your actual accessories attached. Equipment behind the tube changes the balance point, so confirm there is enough adjustment on the rail and clearance around the mount.
Fine focus with the primary mirror held fixed.
The rotatable 2-inch dual-speed Crayford focuser moves the accessory position while the primary stays fixed. Coarse and fine controls help you approach focus and then refine it.
Support a heavy diagonal or camera while securing the connection. Check that cables do not pull on the focuser as the telescope moves, and allow any vibration to settle before judging the final adjustment. A motorised setup needs a compatible bracket and coupling; establish those details before choosing a motor.
A useful starting point for eyepiece choice.
Divide the telescope’s focal length by the eyepiece focal length to calculate magnification. For this telescope:
| Eyepiece focal length | Approximate magnification |
|---|---|
| 25mm | 73× |
| 15mm | 122× |
| 10mm | 184× |
These are calculated examples; eyepieces are purchased separately. Begin at lower power to find and centre a target, then increase magnification while the view remains sharp and useful. A higher number does not ensure more visible detail when the atmosphere is unsteady.
Three extension rings, chosen to suit your setup.
Two 25mm rings and one 50mm ring are supplied. They let you position the focuser to accommodate different accessory arrangements.
A diagonal and eyepiece occupy a different optical path from a camera attached directly at the rear. Select the arrangement you intend to use, then fit the extension combination needed to reach focus with adjustment remaining. Installing every ring is not the starting point for every configuration.
Keep a note of the combination that works for each setup. That makes a change between visual observing and imaging easier to repeat.
Moving from visual observing to lunar or planetary imaging.
Start with the camera at the native focal length and practise acquiring the target on the sensor. An accurately aligned finder and steady tracking make a small field much easier to work with.
Use short test captures to refine focus and exposure before recording a longer sequence. Choose any Barlow around the camera’s pixel size and the seeing; extra amplification increases the demands on tracking and focus and is not automatically an improvement.
For long-exposure deep-sky work, consider the narrow framing, f/12 focal ratio and guiding requirements together. Compare the complete setup with other imaging designs if wide nebulae or a first deep-sky system are your main objective.
Included and purchased separately
| Supplied with the OTA | Choose separately |
|---|---|
| Classical Cassegrain optical tube and focuser | Compatible mount and stable tripod or pier |
| Vixen-style rail and finder base | Finder or pointing aid |
| 2-inch to 1.25-inch adapter | Diagonal and eyepieces for visual use |
| Two 25mm and one 50mm extension rings | Camera and its required connection adapters |
Specifications at a glance
| Optical design / aperture | Classical Cassegrain / 153mm |
|---|---|
| Focal length / ratio | 1836mm / f/12 |
| Mirror material | Quartz primary and secondary |
| Focuser | 2-inch dual-speed rotatable Crayford |
| Published tube length / diameter | 437mm / 193mm |
| Published tube weight | 5.8kg |
Before ordering
Does it arrive as a complete observing package?
No. The telescope needs a separately chosen mount, diagonal and eyepieces for a visual setup. The fitted finder base is an attachment point; a finderscope is not included.
Do I need all three extension rings?
That depends on the actual diagonal, eyepiece or camera arrangement. Use the combination that places focus within the focuser’s travel. If you are unsure, send Dark Clear Skies the exact accessory models before ordering.
How should I compare it with the smaller Mini?
Compare the complete kit’s size, mounting load and intended targets. The 4.5-inch Mini Classical Cassegrain offers a smaller alternative. Include the mount and accessories in your storage and transport plan for either model.
Availability reflects supplier stock and may change. Contact Dark Clear Skies to confirm dispatch timing if you need the telescope for a particular date.