To be honest, autoguiding is usually used for larger sensors which would be obstructed by a 1,25"-focuser anyway, and most focusers which are strong enough for a flip mirror, a camera, a guiding camera and maybe even an eyepiece are 2"-focusers, so we preferred a larger mirror.
To test this, take a look through the eyepiece and move the mirror slightly up - if the star moves in the desired direction (or contrary to it), then you need to adjust the brass pins. Please see page 11 in the manual (chapter 3 - Adjusting the mirror). If it moves sideways instead, things get complicated. But that's most probably the solution.
For the eyepiece on the upper port, we'd recommend
#2956242 M42i x 0,75-ClickLock (Astro T-2 System) with a height of 36,6mm.
Please note that the upper port is limited by the diameter of the T-2-thread, so it is a little bit less than 40mm, and there will be some vignetting with 2"-eyepieces with long focal lengths.
For the camera, you can use e.g.
#2956220 SC / HD (2")-Clicklock (5" SC, 6" SC/HD, 8" SC/HD and 9¼" SC)
with a height of 47mm.
If I understand the description of ZWO correctly, the larger camera has 6mm of backfocus when used with either T-2 or a 2" nosepiece; the smaller camera should be similar and also include a 2" nosepiece (if doesn't, but has got a female T-thread, you can use Baader 2" nosepiece to T-2 / M48 # 2408150; if it has got only a 1.25" nosepiece, there is Baader Pushfix Reducer 2" to 1¼" # 2408151 with only 1mm of optical height).
We'd recommend to use these two clamps and to determine the focus position of the eyepiece. You shouldn't need to insert it completely into upper port, as that clamp is shorter. If desired, you can add T-2-extensions later to get to the right distance. Or you focus your telescope now with the cameras to find out how much the focus differs between eyepiece and cameras, then you can determine the required T-2-extensions in advance.
For connection to the telescope, we'd need to know the available thread at the telescope. T-2 or M48 work out of the box, for other threads, an adapter would be required.
For further information, please also take a look at this blog post: https://www.baader-planetarium.com/en/blog/using-the-flipmirror-the-correct-working-distances/
Do you think it is feasible? may you send me a tech drawing with ring holes on the three sides?
I thank you in advance for your kind answer.
- Nikon Z6 - 16mm
- Baader Wide-T-Ring Nikon Z (for Nikon Z bajonet) with D52i to T-2 and S52 # 2408335 (8.3mm)
- optional Reducing piece S52 / M48 # 2958552 (zero length) (for a wider clear aperture; not necessary, if you use T-2 on the telescope side)
The field stop of the eyepiece should be in the same distance from the FlipMirror as the camera sensor. That's ca. 24mm, if you attach the Wide-T-ring directly to the FlipMirror. Then you can use
- Baader Focusing Eyepiece Holder 1¼" / T-2 (T-2 part #08A) # 2458125, 29-35mm for the eyepiece
- Baader T-2 / 7.5 mm Extension Tube (T-2 part #25C) for the camera # 1508155
This gives you a working distance of 31,5mm for the camera and 29-35mm for the eyepiece. With this setup, you should reach focus with most eyepieces - usually, the field stop is at the transition between eyepiece body and 1.25" nosepiece, but it can vary. (We all know, that eyepieces are not parfocal...)
The length of the setup is then:
31,5mm for camera (and eyepiece)
59mm for Baader FlipMirror II Star Diagonal # 2458055 when used with T-2
15mm for Baader T Adapter (BTA) for SC and MAK Telescopes (T-2 part #21) T-2 Part #: 21 # 2408160
=> 105,5 mm
Optimum back focus is 127mm, so you need an additional 21.5mm extension, e.g.
Baader VariLock 29, lockable T-2 ExtensionTube 20-29mm with spanner tool (T-2 part #25Y) # 2956929,
if you want to be precise. (a 20mm extension should work good enough, and there is always Set: T-2 Fine-Adjustment rings (0,3 / 0,5 / 1 mm) - Aluminium #2457910) If you want to use the Off Axis Guider, you should place one 211mm-extension in front of the camera and one in front of the eyepiece holder, this will give you more back focus fur the guiding camera. If you don't use the off-axis-port, you can save money and put the extension between flip mirror and telescope. Fortunately, a Schmidt-Cassegrain is a userfriendly telescope, so that you don't have to keep to distance to a tenth of a millimeter.
The sortest adaptation to the telescope would probably be 2" / S52 Nosepiece # 2958551
The field stop of the eyepiece mus be as far away from the flipmirror as the camera sensor, so it also depend on whether you use a planetary camera, a DSLR or a mirrorless camera. We recommend Baader Focusing Eyepiece Holder 1¼" / T-2 (T-2 part #08A) # 2458125 with a length of 29-35mm, so it should be no problem wit a video module for images of the planets - especially with an eyepiece like the Baader Classic Orthos, where the field stop is inside of the nosepiece. Or you use a low-profile eyepiece clamp like Ultrashort 1¼" / T-2 Clamp # 2458121, which might be the better choice.
For photography with a larger sensor, you'll probably want to use a coma corrector instead of the flip mirror.
Baader SC / HD Ultra Short T-Adaptor, 7mm optical length # 2958500B
to attach it to the T-2-thread of the FlipMirror.
But removing the 1.25"-extension from the ZWO mini should be sufficient. If you then need a shorter 1.25"-extension so that the camera fits better into the Off-Axis-Guider, you can use Baader 1¼" - 31.8mm nosepiece extension with 1¼" filter thread on both sides # 1905130 or an empty 1.25" filter cell as extension (Filter cell 1¼" classic (8mm height) # 2459251 or Filter cell 1¼" Low Profile (6mm height) # 2459251L
I also have a DSLR with the T2 adapter for Astro photography. Can you tell me specifically what additional adapters i will need to connect the flip mirror to the 2” opening on the Meade and to allow 2” eyepiece plus the DSLR?
Please note that the upper port is restricted by the T-2-thread and the diameter of the diagonal. The usable field is 32mm, equal to our 32mm T-2 prism diagonals.
You can screw a standard DSLR with standard T-ring directly to the back of the BFM-II. There are small set screws to adjust the rotation of the camera with a screw driver or an allen key. The distance from the sensor to the flip mirror is then 55mm (the standard flange distance of T-2).
On the upper port, you can use the M42i x 0.75-ClickLock (Astro T-2 System) #2956242 with a height of 36,6mm. Then you need a T-2-extension of ca. 18mm to bring eyepiece and camera to the same focal distance. It might be the best to use the shorter Baader T-2 / 15 mm Extension Tube (T-2 part #25A) # 1508154 and let the eyepiece stick out a little bit, or to use a 7.5mm or 15mm extension between camera and flip mirror and a Vari Lock for the eyepiece holder. We can't give a final anser to this, because not all eyepieces have the same focus position - it is often at the top of the 2" nose piece, but it may vary. For 1.25" eyepieces, you have to take the length of the 1.25"-adapter into account, too. The shortest solution is Baader Pushfix Reducer 2" to 1¼" (T-2 part #15a) # 2408151.
For more about this, please take a look at this article: https://www.baader-planetarium.com/en/blog/using-the-flipmirror-the-correct-working-distances/
You ned to place the field stop eyepiece at the same distance from the BFM-II as the camera; and it is easier to vary the eyepiece positin than that of the camera.
Baader FlipMirror II Star Diagonal
Various ports – variable work
Telescope auxillary instruments cover a wide range of interests, from a sole eyepiece, via camera use, to high end spectroscopy. Unfortunately every telescope just features one exit port. This causes relentless manual exchange of parts in the dark, causing huge time loss, wear on the parts - and "nerves". And whenever you start controlling your telescope remotely - the single port becomes a painful reality.
Improving workflow, especially during astrophotography is the goal set out for the BFM II. This is not just a simple flip mirror but much more, as there are three ports to be put into action.
BFM II makes your single telescope port variable - to suit your various interests.
The FlipMirror II Star Diagonal allows a variety of permanent adaptations to your telescope 1 . Use the rotary knob 2 to switch between the rear port 3 and the top port 4; you can use an optional toothed belt to operate it with a motor (not included). An autoguider or a calibration lamp can be connected to the bottom port 5.
General Function of the FlipMirror II Star Diagonal
The BFM II lets you switch between a straight light path (Position A) for a camera or other measuring instruments and an angled light path (Position B), e.g.
for an eyepiece. The following figure shows how it works. In addition, a calibration lamp for spectrographs or an Off-Axis-Guider pickoff-prism (that is not affected by the mirror position) can be connected at the AUX-port on the bottom
Scope of Delivery of the Baader FlipMirror II Star Diagonal:
- Baader FlipMirror II Star Diagonal – with fine-optically polished, movable mirror
- Laterally adjustable T-2a top ring
- 2x M48i / S52 Dovetail ring made of hardened stainless steel # 2958552
- Reducing ring M48a / T-2i # 2958553
- Reducing ring M48a / T-2a # 2958554
- Inverter ring M48a / M48a # 2958555
- Pin type face wrench for M48 / T-2 and M4 counter nuts
- 3 mm screwdriver for M 4 brass adjustment screws
- 4x hex keys (2.5 / 2.0 / 1.5 / 1.3 mm). The 2.0 mm wrench has a ball head to reach screws even when accessories are mounted by holding the wrench at an angle.
- Bottom flange (laterally adjustable 1mm) for off-axis guide or calibration lamp for spectroscopy
- Dust cap for bottom flange
- 2 x M48 dust caps
- T-2 dust cap
|Optical length (mm)||55 mm with S52, 59 mm with M48/T-2|
|Dimensions||63 x 77 x 69 mm|
|Inner Connection (lens sided)||Thread, Dovetail ring clamp, S52, T-2 (M42 x 0,75), M48|
|Weight (kg)||195 g|
|Inner Connection (eyepiece/-camera-sided)||Thread, Dovetail ring clamp, M48, S52|
|Outer Connection (eyepiece/-camera-sided)||Thread, M48|
|Type of Adapter||Variable|