Thinking of upgrading my DSI II Pro Mono guiding chip- would a ZWO ASI120MM-S be good

[g__day]

Hi Folks,

I was considering upgrading my Meade DSI II Pro Mono guide camera as my primary imaging chip and wonder if the ZWO ASI 120MM-S camera might be a decent choice?

The Meade works well (with Maxim DL and Phd or PHD 2.5, but it won't work with TSX full (camera, mount, dome) edition - there are no ASCOM drivers for the DSI!

I currently use the Meade when I am guiding through a Giant Lumicon OAG on my C9.25 - when I can't find a guide star there I use a QHY 5II-L of a Williams Optics 98mm refractor piggy backed on a WO 110 FLT scope. The QHY is very sensitive - but sometimes its software is temperamental getting it to connect!

So a question or two about https://www.bintel.com.au/product/zwo-asi120mm-s-usb3-0-monochrome/

1. Is the ASI120MM-S a good mono imaging camera
2. Would it make a good choice for my gear?

Many thanks,

Matthew

[Merlin66]

I have both the ASI 174MM and the QHY5II.....
The QHY meets most of the guiding needs.
Do you have a problem with this ??

[peter_4059]

Hi Matt
I can't comment on suitability for your gear but I'm using the 120mm as a guide camera through a 50mm f5 borg and it works well and plays nicely with phd2

[g__day]

Hi Merlin,

I have two guide cameras at the moment - one on an OAG (and if it can't find a guide start) I use the QHY 5II-L on a 98mm WO. It's just sometimes the QHY doesn't connect or respond. A shut down and re-power the PC often fixes that - but its a pain to do. I think its related to in what order I start the guide software - it might think the camera is alyready engaged.

But the QHY when it works plays nice - its the Meade I am thinking of upgrading - something a bit more sensitive that always plays nice with software and has a ASCOM driver that TSX can see!

[g__day]

Done! Now here come the clouds! Must see if I can bring both ZWO cameras closer to the OAG!

[g__day]

I managed to get the gear all working last night (after several mistakes on my part).

One thing I am pondering if how small the stars should appear in the OAG? I tried to get the focus spot on - but the stars appear quite large. When you get a star say 10 - 12 pixels across PHD2 seems to reject it as a star at all. Has anyone ever seen this behaviour and do you know how to address it in case I can't get the star image to be smaller?

[Merlin66]

I work regularly with a C11 at f10 with an on axis guider - a reflective slit plate.
Generally the star images are reasonably small - I'm using the Lodestar at 2 x 2 binning, certainly OK for guiding.
At 2800mm fl, a 3 arcsec star image is 40 micron, with a 4 micron pixel camera, this is 10 pixel or so......
Can you set the camera to 2 x 2 binning???

[g__day]

When I set the guide camera from 1x1 to 2x2 binning the star actually became bigger! When I look at it on the PHD2 sceen its about 3-4mm in diameter - which may be too big for PHD2 to even recognise as a star.

So does this mean my OAG guiding cameras focus is still just way off or have I done something else wrong? Still wondering can you tell PHD that big stars are actually big stars whilst I try and figure out why they are so big!

[Merlin66]

Hmmm
I'd certainly try to re-adjust the OAG to get smaller star images.
Are the star images saturating - may be try a shorter exposure?

[g__day]

I don't think (total guess) they are saturating - it was only 1-2 second shots - though I tried 0.5 second shots - the star images still looked wayyyy to big!