Is 120mc good as a guide camera or do I need somethig else?

firstc8

I have so far used my 120mc-s with PHD for PEC only so locked on only the brightest stars. I am considering a camera upgrade and get a larger sensor, less noise and more sensitivity. I am mostly interested in DSO imaging, so will likely need a guider scope soon.

What ZWO camera is recommended for me moving forward? Will the ZWO guide scope fit on the same Celestron C8 dovetail bar with the mount clamp already taking a lot of space? I have seen some pictures people doing it. I am trying to do more with less weight if possible.

riklaunim

I use smaller finderguidescope (smaller than normal guidescope) and ASI120MM (mono version) and it works like nearly any other guider/planetary camera I used for guiding.

firstc8

What is your guide scope spec? If I can find one to fit my scope on the under side, the better.

Sam@ZWO

there is 1/4" screw under the dovetail bar of 60280 guide scope

so you can fix it in any other scopes

a mono camera is always better than color camera for guiding

so 174 will be the best, large format and high QE to let's you find any star visiable

riklaunim

firstC8 wrote:
What is your guide scope spec? If I can find one to fit my scope on the under side, the better.

50 mm aperture, 162 mm focal length

firstc8

Sam wrote:
there is 1/4" screw under the dovetail bar of 60280 guide scope

so you can fix it in any other scopes

a mono camera is always better than color camera for guiding

so 174 will be the best, large format and high QE to let's you find any star visiable

174 was on my list of main imaging cameras, not guide cam. Any cheaper ones to suggest? I also will consider an off axis guider. Any pros and cons?

firstc8

riklaunim wrote:
firstC8 wrote:What is your guide scope spec? If I can find one to fit my scope on the under side, the better.

50 mm aperture, 162 mm focal length

Will take a look at that spec. Would such small guider scope simply take the place of the stock C8 finderscope? If so it will be very appealing.

Like I asked Sam, is an off axis guider a bad idea? I know finding stars may be hard, but if the main imaging sensor is not very wide, the off axis has more area to find stars.

I am only going by what I have read, no practical experience yet.

riklaunim

Yes, it replaces a finder scope. It's best to mount it directly on top of a telescope to get uniform balance. OAG is harder to use (it must be in perfect focus to see stars), but in general it always provides correct and accurate data for guiding. I used OAG with SCT for some time, but then I switched to external finder-guidescope just to have easy access to guide stars.

firstc8

Sam wrote:
there is 1/4" screw under the dovetail bar of 60280 guide scope

so you can fix it in any other scopes

a mono camera is always better than color camera for guiding

so 174 will be the best, large format and high QE to let's you find any star visiable

Sam, have you tried to use your guide scope with 120mc and PHD for guiding? I called my vendor they said the reason my 120mc did not find stars was because I used my C8 which has too long focal length. Although I had F3.3 reducer so my FL wasn't that long.

firstc8

riklaunim wrote:
Yes, it replaces a finder scope. It's best to mount it directly on top of a telescope to get uniform balance. OAG is harder to use (it must be in perfect focus to see stars), but in general it always provides correct and accurate data for guiding. I used OAG with SCT for some time, but then I switched to external finder-guidescope just to have easy access to guide stars.

How difficult was it using OAG with your SCT and how sensitive the guide camera needs to be? It seems I have two things against me, the 120mc sensor is not very sensitive, and the long FL of the C8. I will be using F3.3 reducer most of time don't know if this will help.

riklaunim

Guider sensitivity isn't a primary issue as it's relatively easy to get a guide star visible with high gain even with older sensors that have much lower QE. OAG problem is that there may not be a guide star available for given frame. On 1-2 sec exposures I had such cases for some imaging.

With f/3.3 SCT reducer/corrector you have a very short reducer-camera distance so you would have to use one of those very thing OAGs (Newtonian backfocus compatible).

firstc8

Thanks, to ease myself into it, I will consider a guidescope.