Guide camera exposure time scale not scrolling

franco

Might be a coincidence but today my phone updated to Android 13 and now I can't set exposure times less than 0.5 seconds for guiding. The exposure selection list appears to be fixed and doesn't scroll to show anything less than 0.5 seconds. The main camera setting in the preview window seems ok.

I'm using the B48 beta.

franco

Ok so this is something that has changed in the beta without me realising it. Maybe you wouldn't expect to use an exposure less than 0.5 seconds for guiding, but I often setup in the daylight and check the view though the guidescope.

PMTeam@ZWO

franco Thank you for your feedback. We will talk about this.

w7ay

franco I often setup in the daylight and check the view though the guidescope.

Franco, cut a piece of cardboard aperture that fits over the objective end of guide scope, and drill a small hole (start with 1mm hole) in the cardboard. The neat thing is that depth of field is very relaxed for such large f-number, and you may not need to disturb the focus settings.

A less kludgy way to to drill a small aperture in the "lens cap" of your guide scope. For convenience, I have actually replaced the lens cap of one of my guide scopes with one of these quick-connect plastic lens cap for camera lens. If you do that, you can drill a small hole through it as an aperture stop down.

If you don't mind having to refocus during the daytime, go to Amazon and find a neutral density (ND) filter that fits on your scope. My guide scope's Borg 55FL dew shield is threaded for a standard camera lens thread, and I have been able to use front filters and Bahtinov masks this way.

If your guide scope is threaded with a camera thread, you can even use step down rings (or a series of step down rings) to reduce the aperture and not have to drill anything. Reducing the star shape is also a good way to get better star shapes to guide on, as long as you can still collect enough light.

Chen

franco

@ASIAIR@ZWO#58182 FYI: The full EXP list will be back in the next update.

Thanks.

w7ay I've been working around the limitation by setting the guide camera as the main camera but thought your suggestion sounded like fun so I cut a circle of cardboard and made a pin hole in it. First thing I noticed was that I could see the fly screen on the door I was pointing the camera through when with the cardboard in place - took me a while to realise what it was, thought it might have been a wire fence. Anyway I moved to an unobstructed view.

Here is a picture from the guide camera without the pinhole taken at 1ms

And here with the hole at 0.5s

Shows up the motes amazingly well!

Unrelated but may also be something that's changed in the beta, my goto's aren't as accurate as before. This might be just a feeling because I've stopped doing auto-centring. I've also noticed that if I'm guiding and do a solve, align and goto, the guiding never recovers, I have to manually stop and restart it. Shouldn't the AIR stop guiding when slewing?

Cheers,

PMTeam@ZWO

FYI: The full EXP list will be back in the next update.

w7ay

franco Shows up the motes amazingly well!

Yes! For cleaning sensors, it helps to use an OTA with a large f-number (or add Barlows) :-) :-).

Notice that the resolution is also drastically reduced. Just use one of the web calculators to compute the Dawes Limit (or the Airy Disk size) when you reduce the aperture to a small pinhole, and you will see why.

Use a neutral density lens if you don't want these effects :-).

Shouldn't the AIR stop guiding when slewing?

Hah, this used to be a real problem with the RST-135 for me. The ASIAIR did not stop guiding when you slew (as you say, it should). So, when you slew, it causes the mount to lock up completely. I had to reboot the mount to make it work again. Unfortunately, it is dangerous to turn off power to a strain wave mount that has no power-fail braking.

I eventually found that I could make the mount not require a power reset by forcing guiding to stop, change the slew rate slider and press on the slew buttons, repeating a couple of times until the mount moves again.

But I have since learned to remember to stop guiding before I execute a slew or GOTO.

I had reported this (guiding not automatically stop -- or at least pause -- when the mount is being slewed) to ZWO about two years ago, but I don't think they bothered to fix the bug. I'm afraid that it will take one of their own mount customers ruin his or her instrument before ZWO pays attention to mount related problems. Just look at how long the numerous AVX bugs (plural) not been fixed. They have no financial interest to fix them. A lawsuit usually fixes financial problems :-).

Chen