Askar SQA 130, Sky Rover 130, and William Optic 131 Owners - Back focus Questions - Forums

Topic starter

4 hours ago

Hello, Im pulling my hair out over getting the SQA130 setup to image remote with an OAG system.

Currently I have a Wanderer Mini M54 rotator, a 9mm spacer to avoid OAG hitting the rotator, a ZWO OAG L, ZWO EFW 7×2, and an ASI 6200mm Pro.

This currently brings my backfocus to 79mm.

The acceptable BF range of the SQA 130, being a petzval, is 44mm to 76mm.

My first idea to reduce BF was to eliminate the built in CAA on the focuser.

Askar does not provide an adapter for that and it appears to be an 87mm x1 thread.

The goal for me would be to reduce this down to M68.

At this point someone pointed out another issue, If I successfully accomplish this, It is highly likely the Rotator motor would hit the focuser, so really I need a spacer between the CAA thread and my rotator.

Now this really messes up the whole concept of my configuration.

At this point I regret not spending time looking at other options, thinner OAG options, thinner EFW options, maybe even a different camera.

After all the effort and money spent, I will likely just need to use the guide scope and planetary camera that was sitting on my shelf this entire time.

I really did not want to have any differential flexure translate into my data but unfortunately It is probably un avoidable.

If anyone has successfully setup one of these scopes using a rotator, OAG, EFW, and camera, I would LOVE to hear how you did it.

For reference and comparative purposes here is my current configuration, maybe this will help anyone shopping this scope!

Current Train:

Wanderer Mini Rotator M54 - 10mm

M54 Spacer - 9mm

ZWO OAGL With M54 tilt plate - 22.5mm

ZWO EFW 7×2 - 20mm

ZWO 6200mm sensor to thread distance - 17.5mm

79mm total

In my research I have learned that there are other thinner options.

I have already blown through my budget and Im outside of any return windows so Im stuck with my setup for now, but maybe this can help you.

Pegasus indigo OAG is 14mm thick with adapters installed

The pegasus indigo Efw is 19mm

The wanderer Snowflake EFW is 16mm thick. But I do not know what the optimal OAG is for this FW, maybe wanderer will make one.

Also note, I think that due to the bigger diameter of the M68 wanderer rotator, you are less likely to hit the focuser. if you buy this, although it is 12mm thick

So with a Pegasus OAG and Wanderer Snowflake you can pull off a total of 33mm backfocus. You will likely need a spacer between the oag and rotor.

But the total train would be around 59.5mm of back focus. You could even add a spacer between the electronic rotor to not hit the focuser.

This keeps you way inside of the 76mm BF spec.

The mystery component is still the thread pitch under the Factory CAA and how long the adapter needs to be to no hit the corrector lens.

If anyone knows the answer to this, please share. I have a rough idea, but not hard evidence.

So for now I will limp by using a guide scope, but in the mean time I will see what comes about this thread and then shop for the appropriate accesories so I can go back to OAG.

Please share your experiences and input!

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Steven Zuhoski

3 hours ago

On a FLT120, had to get rid of the OAG to add the CAA (MoonLite focuser; FL=780mm; fully loaded weighs in at 30 lbs). Works fine with the external guide scope. Never really worried about differential flexure on the refractor or saw an issue with using the external guide scope (more worried about it on SCTs). Are you getting play or sagging on the SQA focuser where you might run into flexure? That might be where I would put my money.

I’m very interested in hearing more about your experience with the guide scope since I have been looking at upgrading my remote scope with the SQA 106 (and using the stock focuser with an EAA). I was thinking about moving the FLT120 out there, but I think it may be too much for the mount.

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Rick Krejci

2 hours ago

According to Wandererastro’s site, the Snowflake EFW bolts onto the camera as well as the OAG and there’s a 14mm version of the EFW, so that alone should get you the needed backfocus if you eventually want to use your OAG.

Also, the WA Mini should not interfere with the focus knob, especially if you’re not fully racked in, or scope’s rotator, so I don’t think you need that upgrade either. You’ll likely need to remove the scope’s rotator knob to thread the Mini on, and then replace it once in place. Replacing the scope’s rotator with a hard adapter will not change the position of focus of your imaging train or bring your rotator farther from the focuser knob.

In general, I would prefer the guide scope on a sturdy mount, particularly if you have a auto-rotator. With a relatively short focal length refractor there should be very little differential flexure. With a rotator and an OAG, you’d have to recalibrate every time you rotate, even in the middle of the night if you change targets. With a guidescope, it’s one and done.

So my recommendation is go with guidescope and the image train you have minus the OAG. I don’t consider that limping at all. Make sure the adjustments on the focuser are fairly tight to avoid tilt/flexure. If, for some reason, there is an issue, then consider replacing only the EFW with the WA Snowflake and add the OAG. But I don’t think you’ll have an issue with the guidescope solution and will appreciate the simplicity.

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