First night out, focus issues

[RussellH]

So my scope has finally seen it’s first night-time sky, although the results haven’t been that great.

Recap on the setup. HEQ5 Pro mount, Skywatcher f5 150mm newt, asi120mm mini guide camera, svbony 50mm guide scope, Canon 450d dslr, raspberry pi3b+ running astroberry using Kstars/Ekos/Indi for control.

So first question, how the heck do you focus without autofocuser or visual observing? 3 hours of fiddling and I finally got the guide scope sort of focusing (stars visible, but furry) but the camera I ran out of time for tonight ght so had to give up. Taking 10 second exposures and tweaking the focus incrementally is very slow.

Secondly, focus distance. I had to pull the asi right to the back of the guide scope mount position, and pulled the focuser out all the way, to get it to focus. i have very little movement room left but hopefully tomorrow night I’ll finally get it properly focussed.

As for the Canon, I’m not sure how far I am off the focal plane, but it seems to be somewhere within about 5mm of bottoming out the focuser. At least I hope it’s around there, or I’m going to be short of back focus distance. Where I think I’m in the ballpark causes significant protrusion of the focus tube into the body of the scope though, which I think is why I am seeing the squashed side on the out of focus donuts I have been try to resolve in the image all night.

Ikm trying to attach some pictures to show where the focuser and guide camera seem to be required, but having some troubles with attachments. Will try in a separate post to follow this one.

Russell.

[RussellH]

Here are some images showing the placement of the guide camera, the available movement in the focuser around where I hope I can get the dslr to focus, and the amount of protrusion into the main tube at this location.

I was assured before I bought the scope that it had plenty of back focus to accomodate my camera focus requirements. Oddly enough though though, when I tried focusing with the supplied 2” eyepiece, I had to pull it out to the extreme of it’s length, and with the focuser all the way out. So it seems its from one extreme of the focuser travel to the other between visual and AP, unless I’m doing something wrong trying to get the camera in focus?

Russell.

[Startrek]

If your imaging with a DSLR , capture software called BYEOS was specifically designed for both Canon and Nikon DSLR’s
It has a frame and focus feature which is excellent, I can focus in 5 mins or so
The only requirement is that you need your laptop outside with you near the mount
2 years ago I use to stand next to my mount and DSLR with a remote shutter release and try and focus by taking heaps of short exposures and check one by one , it use to take me forever to focus , now it’s done in 5 mins
I think there’s a trial version of BYEOS, maybe give it a thought ?

[RussellH]

I don’t really have a windows laptop suitable for regular use, but If it works on windows vista I have an old one I could try to see if it’s a user error or not.

[doppler]

Hi Russell, firstly for visual the focuser will be right out and photography almost all the way in, this is normal.

The easiest way to focus is to find a bright star, turn on live view zoom to 10x which will get you pretty close to focus, then a couple of test shots to fine tune.

Not sure about the asi focus I have a similar guide scope and 120mc cam and that has plenty of adjustment to spare. The cams are very sensitive to focus distance but once done and locked in place you don't have to touch focus again.
Rick

[RussellH]

Right, well I’ll see if I can get a more realtime view to tonight and see how I go. Finding a brighter star might be the trick. My view was close to SCP, so only faint stars around. Problem was I still hand’t polar aligned so wasn’t up to trying GOTO yet.

I did get the guide scope doing some plate solving for polar alignment just before I had to quit for the night, so the focus was close enough for that at least. However the adjustment vector after the initial solve was off the screen so I was obviously a ways out of alignment. I used the Polar Align Pro app for the initial scope placement and did have some issue with it as the south indication kept jumping around between readings as if it was losing its true south offset. I read lots of rave reviews of the app before buying, so I’m not sure if I’m doing something wrong with it too, or there’s some sort of interference where I am.

[xelasnave]

Perhaps try focus first on Jupiter as bring it into focus will show the Moon's.
But don't be concerned that it takes a while...the other night I could not get focused and I was using a mask ...n the end I discarded the mask and enlarged the screen and focused that way...I think he seeing was not too good as opposed to anything else.
Good lck.
Alex

[RussellH]

Of course the catch 22 is to get focussed enough for polar alignment, so I can then find a bright start to focus on....

[RussellH]

So I’ve caved and ordered the ZWO EAF auto focuser. Attached is an image of my focuser. Any clue how ai take the knob off? Instructions say the coarse knob, but I see no screw there like the one on the right?

[Merlin66]

Russell,
On my DMK51 which I use as a electronic finder, I had to add a UV-IR filter to tighten up the furry star images.
The ASI 120 doesn't seem to have a UV-IR filter included....may be worth adding.

[RussellH]

Sorry the focuser is for my Canon 450D which is the main imager. The guide scope will remain manual focus.

[Merlin66]

Russell,
Yeah, understood.
I was commenting on your first post where you say:
"I finally got the guide scope sort of focusing (stars visible, but furry)"

[RussellH]

Oh right :) weathers been cloudy all
Week so I haven’t had a chance to check further if it’s just me or not.

[brian nordstrom]

;) That black plastic knob is only a protector for the fine focus underneath , just pull it off , it's for transporting in safety .

Brian.

[RussellH]

Oh really? LOL. Well it works perfectly as it is! Still doesn’t tell me what I’m supposed to remove when the auto focuser arrives. Do I take the fine focus end off instead of the coarse one? The hole in the coarse end doesn’t look like it has anything to unscrew.

[RussellH]

So I found these instructions https://starizona.com/store/Instructions/MicroTouch_Skywatcher.pdf fora different focuser. They are removing the fine focus side. So I guess that’s the one to remove. I’m sure all this is obvious to those who have done it before, but I’ve wrecked too many “obvious” things in the past that apparently weren’t, so I’d rather be sure before diving in blindfolded.

[Merlin66]

Russell,
Caution!!
The ZWO installation sheet definitely shows the motor fitted to the opposite side to the 10:1 knob.
https://astronomy-imaging-camera.com/manuals/EAF_Quick_Guide.pdf

[RussellH]

Yes, and I’ve since seen a 13 second video which shows the coarse side knob removed but not how they removed it. Also saw an old post from someone who said the knobs are screwed in but thread locked and they forced it to unscrew. Good in theory unless the design has changed and you’re trying to force something that shouldn’t be :(

[Merlin66]

Russell,
I had a look at the focuser on my ED80, similar to yours.
There's a small hole on the base plate of the focuser just inside the black "tube" at the knob.
If you gently rotate the knob you'll find a position where, when looking into the hole it goes from silver to black. This is exposing a small 2mm grub screw which holds the knob onto the shaft. You'll need a 2mm allen key.
I'll try to get a photo for clarity.
Ken

[RussellH]

Thanks Ken. I just got home and had a quick look and I think you’ve hit the nail on the head. I can see a dark spot through the hole when I rotate the knob. I’ll attack it when the EAF arrives but it looks exactly like what you’ve described, which is Monday hopefully.

And for Brian, I’ve attached a new photo - Look Ma! No travel protector! :eyepop:

Russell.

[brian nordstrom]

:shrug: Oh really ? ,, sort it out for yourself ! '

Brian.