First time zwo equipment user - Need help!

661Xmjpz

Need help focusing and to polar align. I am facing trailing stars issue in just 3s exposure on preview mode and never able to achieve focus. I setup the cabling etc, altitude is locked almost perfectly (as per asi air), tracking shows on in Asi Air and I start preview mode with 3s exposure to get focus adjustment, i get pictures with trail and no matter focus adjustment it is always trailing because stars are moving fast and not remaining in view. I take terrestrial photo and point at a far building and the focus is perfect and able to get a non blurred clear picture of the building too.

I switch to focus mode and it shows number at 10 for the star. No star remains in FOV for even a second and keeps moving every second and hence not able to get to use focus option in Asi air.

Appreciate if someone could help let know what I am missing? Below is my config (I don't own a guide scope)

Telescope: Explore scientific doublet refractor (600mm focal and 102mm aperture)

Mount: ZWO AM3n

Asiair : Asiair plus 256 GB

Tripod: ZWO TC40 tripod + PE200 pier extension

Camera: ASI 585mc pro (cooled)

661Xmjpz

661Xmjpz To be clear I am not trying to polar align, but prior to polar align I am trying to achieve focus.

Luxo

Ok… as I am guessing you don’t have an EAF, and use manual focus on your scope…

It’s possible you’re really way, way off focus. And may even need extension tubes.

Put an eyepiece in the scope and aim it at something really obvious like the moon. Focus with the eyepiece. Note that with most modern eyepieces the focal plane is about 5-7mm outside the end of the draw tube holding the eyepiece. That’s where your camera sensor needs to be. Use a ruler or tape to measure this with respect to the end of the scope OTA or the base of the focuser.

Connect the camera to ASIAir and set it to PREVIEW mode at BIN4, 1 second, so it updates fast.

With the scope still at the moon, remove the eyepiece and hold the camera in your hand at the back of the focuser. Moving the camera in and out you should be able to roughly find where the camera needs to be to get an image. If possible attach to the focuser, but if there isn’t enough travel, go find some extension tubes.

Alternatively use the ruler measurement and the geometry of the camera as per ZWO website to calculate the distance required to the faceplate of the camera. Attach the camera to the scope at this distance, making sure you still have a few mm of travel in/out.

NB my small refractor (a TS Photoline APO) I have to add 50mm of extension tubes for it to reach focus with an ASI533.

Once you know it’s close:

Aim the scope at a field with something bright - Jupiter, Sirius. In the main camera settings increase the gain to medium, say 100-150 (not critical)
Select PREVIEW mode and set this for BIN4 and a fast cycle time like 1 second. BIN4 means the frames will be small (in megabytes) hence it should update fast.
Adjust focus a little then stop and let AA update TWICE (2 frames) because there is a bit of a lag.

When you start to see de-focused stars you’re getting close, so use smaller focus changes.

If you don’t have one, buy or make a Bhatinov mask (not the tri-Bhatinov) this is essential for precise manual focus.
For perfect focus switch to BIN1 and zoom in on the display.

661Xmjpz

Luxo Thanks for responding

as I am guessing you don’t have an EAF, and use manual focus on your scope…

That's correct.

Put an eyepiece in the scope and aim it at something really obvious like the moon

With eyepiece the target is always great. Have been doing visual astronomy for long. Point noted on sensor being at the same point.

Connect the camera to ASIAir and set it to PREVIEW mode at BIN4, 1 second, so it updates fast.

What are the differences between the 4 bin modes?

Alternatively use the ruler measurement and the geometry of the camera as per ZWO website to calculate the distance required to the faceplate of the camera. Attach the camera to the scope at this distance, making sure you still have a few mm of travel in/out.

ZWO recommends 55mm backfocus, but that isn't working well for me in terms of focus.

For perfect focus switch to BIN1 and zoom in on the display.

Yeah, that's what I try to do.

Luxo

661Xmjpz
Binning ?

It reduces the image size, significantly, so a smaller file = faster to load.
For my ASI2600 DUO at Bin 1 the image file size is 52MB, and takes about 7 secs to transfer to the ASIAir app.
Bin2 means 2 x 2 pixels are merged as one, so the filesize is reduced by 4, and loads 4X faster.
Bin 4 means 4 x 4 pixels are merged as one, so the filesize is reduced by 16, and loads 16X faster.

Even at Bin4 there are still enough pixels - and resolution to see if the scope is approximately focussed.
For precise focus, switch to Bin1.