First, bad news then the good: My new ASI2600MM Pro was delivered last month. As it sometimes happens with new things, not all is well. The camera's temperature sensor was not reporting. From reading forum posts, it appears that ZWO, like every other maker of advanced astronomy gear, has occasional blips in their quality control. A non-functional temperature sensor is not common, but it does happen.
I got in touch with OPT (the vendor) and they had ZWO contact me with the fix. The fix is so simple I wondered if it could possibly work: Shoot some compressed air around the sensor's flat cable, pop open the little clip holding it in place, shoot some more air in, jostle but do not disconnect the cable (that part was left very vague in the instructions), close the clip, and button the camera back up.
It worked!
FSQ-106EDX4 Imaging Optical TrainsCAVEAT: I have not taken delivery of the FSQ so none of the following has been verified in the field. A vendor post on CloudyNights suggests delivery may have to wait until February!
Now on to the main topic: how to get ready for imaging with the FSQ-106EDX4.
The imaging cameras will be an ASI2600MM Pro and a modded Canon T2i. I'll be using the FSQ in two modes: native f/5 and f/3.65 using the CR 0.73X focal reducer, and I would like to use the ASI with my existing EOS lenses. (I resisted the temptation to buy the 0.6X reducer, opting instead to save a thousand dollars and make the optical train a little more user friendly.)
I'll be imagining with two devices: a Ha-modded OSC Canon T2i and the ZWO 7x36mm EFW (M42 connections, optical thickness 20mm) with ASI2600MM (backfocus of 12.5mm after removing the tilt plate). The following configurations are based on what Takahashi has published about their adapters (see link below) and forum comments on CloudyNights.com.
FSQ106 Native Mode + ASI2600:
The FSQ focuser has a travel range of only about 30mm, so back focus should put the sensor near the center of this if possible. Sources suggest this is at a distance of 163mm (178mm minus half the travel range) beyond the end of the focuser. Already in the optical train are the 645 RD adapter (TKA36581, 10mm backfocus), CAA-250 (TKP86200, 38.5mm), Aux Ring S (TKA38205, 27.5mm), and Coupling TW (TKP36003, 34.2mm); their total is 110.2mm. This has stepped us down from M98 to M54 thread and we still need about 53mm. To get us down to M42, we use Blue Fireball's adapter with thickness 6.9mm. Now we add the EFW (20mm) and 2600's backfocus (12.5mm without the tilt plate) and we're at 110.2 + 6.9 + 20 + 12.5 = 149.6. We add a simple 12mm M42 spacer and get 161.2. You could use a 5, 10, or 15mm spacer, or even a thicker M54/M42 adapter. "Close" is good enough.
REVISED 8/11/2022 The diagram above is not longer correct. FSQ106 + CR 0.73X Focal Reducer + ASI 2600
Takahashi says the optimal distance from FR back to sensor is 72.2mm. The camera backfocus and filter add to 32.5mm, leaving 39.7mm for adapters that will take us down from M56 to M42. The M56 adapter in the diagram proved to be problematic so instead I'm using these adapters: Blue Fireball M56(f) -M48(m), M48(f)-M42(m), and M42(f)-M42(m), with respective lengths of 12.1, 16.5, and 10mm. This gives a total of 38.5mm, about 1.2mm short. I used the Hocus Focus plugin for NINA to see if this was close enough. The plugin suggested I need to add 3 focuser steps, which translates to a mere 0.011mm. In other words, the plugin agrees with the new setup. I will add another 1.2mm to the adapters and run the plugin again to see what it says.
It's not clear to what extent vignetting will be an issue, but my hope is that it will be largely correctable using flats.
Canon EOS lens + ASI2600
(Note: This has been tested and shown to work. See later post.) The backfocus target here (per the ZWO documentation) is to put 43.8mm between the lens and sensor (26.3 for their adapter and 17.5 for the camera with tilt plate attached). I want the EFW in this train, though, so I remove the tilt plate and use a thin Canon lens to M42 adapter (10mm). This puts it at 10 + 20 + 12.5 = 42.5. Thin spacer rings are used to bring this up to the required value.
Incidentally, this configuration is the reason the tilt plate is missing in all the other configurations.
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| Correction: Cam sides of scope and FR are M56 female |
FSQ-106 Native mode + Canon T2i
The FSQ-106 System Chart tells us we need only spacers provided with the telescope and the Wide T-mount for EOS.
FSQ-106 + CR 0.73X Focal Reducer + Canon T2i
The FSQ-106 System Chart tells us we need only spacers provided with the telescope, TKA35201 and the Wide T-mount for EOS.
LIST of PARTS NOT INCLUDED with FSQ-106EDX4
This lists the adapters and spacers needed to supplement the parts provided with the FSQ-106. They are listed along with their: backfocus, manufacturer, vendor/part #, and price. Very possibly you can find alternative products and vendors, but I'm very happy with Agena and OPT.
M54 (f) to M42 (m), 6.9mm, Blue Fireball, AgenaAstro/PAAR-BF-T-16, $25
M56(f) to M48(m), 12.1mm, Blue Fireball, AgenaAstro/ PAAR-BF-M-24, $43
EOS to M42 (m) adapter, 10mm, QHY, AgenaAstro/PAAR-QH-20072, $35
TKA35201, NA, Takahashi, OPT/TK-TKA35201, $82
Wide T-mount for EOS, NA, Takahashi, OPT/TK-TMW0004, $167
Thin M42 spacer rings, 0.1 to 1.0mm, Blue Fireball, AgenaAstro/PAAR-BF-S-SET7, $40
HELPFUL LINKS
https://www.takahashiamerica.com/
https://astronomyplus.com/wp-content/uploads/2019/08/Takahashi-Adapter-Specifications.pdf
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