Baader FCCT (Filter Changer Camera Tilter) for RASA 8" and QHY cameras

Baader FCCT (Filter Changer Camera Tilter)

The Baader FCCT was designed  exclusively for Celestron's RASA 8 Astrograph and QHY cameras. It is a filter changer with camera adjustment mechanism for covering the largest possible field size that the RASA8 can suppply, enabling sharp image corners and ultimately fast fine corrections to the optical plane. The Baader FCCT (Filter Changer Camera Tilter) allows quick filter exchange as well as very easy correction of field any existing tilt – without having to remove the camera from the RASA 8" each time.

FCCT I with QHY 163M on RASA 8

Celestron's most transportable astrograph, the RASA 8" – Rowe-Ackermann Schmidt Astrograph, ccan capture spectacular deep-sky wide-angle images in seconds. This incredibly fast f/2.0 system is the perfect telescope for modern astronomical CMOS color cameras, smaller CCD cameras and mirrorless cameras. What would otherwise require several nights of exposure time can be accomplished with the RASA in a single night – in principle. Until now, the most severe obstacle was to get the stars in each corner of the chip really round and minimized in size. To do this, the camera had to be removed in order to reach the adjustment screws in the front of the Schmidt plate. But whenever the camera is put back in place, unavoidably this will result in a small lateral offset of the mechanical image train, which causes another corner of the image to show slightly distorted stars. This problem is solved by using the FCCT since nothing needs to be disassembled anymore.

Only the RASA 8 has the image plane is so close to the Schmidt plate that the original front adjustment screws cannot be reached as soon as a camera is connected. To remedy this shortcoming, the FCCT can accommodate specially designed, 3D-printed thin filter drawers and, in addition, precisely align the chip plane within fractions of a millimeter by means of easily accessible adjustment screws positioned 120° apart at the side of the filter chamber. This makes working with the RASA 8 a pleasure, without having to fight for a perfect image position for a long time.

FCCT II with QHY 268M on RASA 8

For the FCCT, we offer three sizes of 3D-printed filter drawers that exclusively accommodate unmounted filters with diameters of 31 mm / 36 mm and 2" (unmounted diameter = 47.4 mm). Smaller filters than 31mm very often lead to vignetting in the image corners even with small chip sizes and force cropping of the image content – leading to correspondingly unhappy customers. For this reason we do not offer the smallest possible filter size of (unmounted) 1¼" filters for the RASA 8". The large angle of view of 14 degrees forces to choose filters as large as possible to avoid image deterioration at the corners as well as vignetting and reflections. A filter should at minimum be 20% larger in diameter than the chip diagonale

The design of the Baader FCCT is of revolutionary importance for the successful use of the RASA 8. The performance of this RASA 8 optics is praised everywhere in the highest tones - only the difficult (better impossible) adjustment of the stars in the chip corners was a nuisance from the beginning. Many users have to work on the move and often did settle for a somewhat blurred image corner in order not to lose precious exposure time.

Digital post-processing of such images then consumes much more time. Already in the test phase of the FCCT very good image results have been achieved by well-known astrophotographers: RASA 8": Extreme image results by Michael Jäger

Scope of supply:

• FCCT I or FCCT II with inserted dark slider and two 0.5mm spacer rings for focus finetuning
• extra long 2mm hexagon screwdriver as torque wrench (28cm long), as well as short 0.9mm, 1.3mm and 1.5mm hex keys
• Three M2 hexagon socket screws for camera adaption
• Filter-Extractor-Tool for inserting/extracting the filter drawer
• Storage bag for four filter holders (to be purchased separately)
• 1 Pair Cotton Cloves for mounting sensitive accessories (#2905050 , € 5.50 )

FCCT Alternatives and recommended accessories

Baader UFC-System (Universal-Filter-Changer) and Baader/Zeiss M68-System with Tilters

UFC-Tilter on the UFC-Base

For all RASA optics, especially for the RASA 11 and RASA 36 models, the UFC (Universal Filter Changer) always remains the first choice to take full advantage of the excellent contrast performance of this most modern of all Schmidt cameras together with CMOS-optimized Baader f/2 (Ultra) high-speed filters. The combination of UFC filter drawer and UFC filter has long enabled comfortable work on the two large RASA models.

Due to the short backfocus of the RASA 8, only the use of the UFC filter drawer was possible on the smallest Celestron astrograph for a long time. With the help of the UFC Telescope-Adapter S70a to RASA 8" – Optical height: 1.4 mm (#2459136 , € 85,- ) , cameras with 13mm backfocus and T-2 female thread - like the ATIK Horizon - could also be used on the RASA 8, together with all regular filters. To do this, the original Celestron coupling nut and adapter plate must be removed and the UFC adapter screwed directly onto the RASA 8 primary thread. Only the adjustment of the optics is complicated, because due to the design the UFC body overhangs the adjustment screws in the Schmidt plate plane. The only thing that this design lacks (only in the case of the RASA 8 optics) is easy access to the pull and push screws of the field alignment lenses in the RASA 8 Schmidt plate plane – hence the resulting development of the FCCT.

With the larger RASA 11 and 36 optics, more backfocus is available, so for this we recommend only using the UFC filter changer system, in conjunction with a  UFC-Tilter (0 - 1° image correction) – Optical height: ca. 10 mm (#2459146 , € 276,- ) (mechanical image-plane corrector), where these components in combination perform the same function as the FCCT for the RASA 8. However, the UFC filter changer does not require ultra-thin filter drawers, but makes the full range of standard filters usable. The UFC-tilter also makes it possible not to have to remove the camera when you need to correct the image position of the chip.

Another choice is the M68-Tilter (0 - 1° image correction) (#2458170 , € 255,- )  whenever the UFC is not required and a filter wheel is attached to the camera or no filters are needed when imaging for example with a DSLR or CMOS/CCD color camera.

CMOS-optimized Baader Filters

CMOS-optimized Baader f/2 (Ultra-) Highspeed-Filters

For all extremely fast astrographs with focal ratios around f/2, special filters are needed. For these telescopes we offer two families of CMOS optimized f/2 Highspeed and f/2 Ultra Highspeed filters. The filter choice has to be decided by the sky quality. Out of the abundance of light from cities, excellent results are obtained with f/2 Ultra-Highspeed filters. For only moderately brightened night skies, the 6.5nm f/2 Highspeed filters are a good and very affordable choice. With conventional filters, which are designed for the relaxed focal ratio of classical telescopes, a shift of the central wavelength (CWL) occurs when applied to fast astrographs. In extreme cases, the CWL of a nebula region may even be completely outside the half-width of a filter. Therefore, specially manufactured f/2 filters are indispensable for such optics.