I've been using a 162mm focal length guide scope on my 1000mm F5 newt so far and it has worked OK. I'm wondering whether switching to an OAG might help with my guiding. My thoughts are that my camera and filter wheel are probably putting a lot of load on my stock focusser (cheap chinese variety) and therefore having the guiding camera directly linked to them could be beneficial. Thoughts?
OAG versus guide scope
Well Written Engaging
I don't understand, wouldn't having another element on the optical train (between focuser and filter wheel) put even more stress and load on the focuser?
Well Written Engaging
Retired IT project managers perspective: if it ain't broke, don't fix it. Never touch a working system (.. if there are no striking reasons to do so).
Why bother if you don't have issues with your current guiding?
Have fun with your setup and clear skies
Wolfgang
Why bother if you don't have issues with your current guiding?
Have fun with your setup and clear skies
Wolfgang
I don't understand, wouldn't having another element on the optical train (between focuser and filter wheel) put even more stress and load on the focuser?
I thought that initially, however it will mean that my guide camera would be seeing the stars exactly as my camera is and as such would send corrections to the mount accordingly. It sounds counter-intuitive to add more weight to the focusser, but technically it may make sense. i.e. if the focussing tube is moving under the weight of the camera or any other elements of the optical train (mirrors etc.) have moved for whatever reason, then having the guiding camera at the end of the train near the camera sensor makes sense. I'll let you know once I've tested it.
Helpful Insightful Respectful Engaging Supportive
Why bother if you don't have issues with your current guiding?
I do have issues with my current guiding ... it's OK, but I throw away 25% of my subs.
Are you getting flexure with your guide scope?
I think I have the same guide scope as you do, which I use on my wide-field setup. One time out ot of curiosity I tested it on my SCT (1280mm when reduced), and I found that my guide scope would sag slightly over the course of the night, and my stars would drift despite PHD2 showing otherwise. This was because I simply could not secure the guide scope to my OTA as securely as was needed to prevent flexure. I therefore use an OAG instead, which is definitely more intended for the sort of SCT-type telescopes for the reasons you mentioned (focuser sag, etc.)
If you're not getting flexure, then I would follow the advice of the other comments and keep to the guide scope. If you are, the first step would be to strengthen the guide scope mounting to prevent flexure.
With OAGs as well, if you have a particularly small guide camera (mainly the ASI120MM), you may sometimes run into the issue of not being able to find a good enough guide star with a desirable exposure.
I think I have the same guide scope as you do, which I use on my wide-field setup. One time out ot of curiosity I tested it on my SCT (1280mm when reduced), and I found that my guide scope would sag slightly over the course of the night, and my stars would drift despite PHD2 showing otherwise. This was because I simply could not secure the guide scope to my OTA as securely as was needed to prevent flexure. I therefore use an OAG instead, which is definitely more intended for the sort of SCT-type telescopes for the reasons you mentioned (focuser sag, etc.)
If you're not getting flexure, then I would follow the advice of the other comments and keep to the guide scope. If you are, the first step would be to strengthen the guide scope mounting to prevent flexure.
With OAGs as well, if you have a particularly small guide camera (mainly the ASI120MM), you may sometimes run into the issue of not being able to find a good enough guide star with a desirable exposure.
Helpful Insightful Respectful Engaging Supportive
Andy Wray:Why bother if you don't have issues with your current guiding?
I do have issues with my current guiding ... it's OK, but I throw away 25% of my subs.
Sorry, I misunderstood your statement "it has worked OK". Throwing away 25% of your subs sounds severe and not OK.
Ratio of image scales between guiding and imaging setup is below 5 and should be ok. So in theory your guiding scope should be able to perfom the job. You may check whether the subs you have to throw a way are randomly distributed over your session or occur in bulks for certain orientations of your scope as I would expect when caused by flexure. In case of random distribution you may just push the limits of your overall setup.
In case you try the OAG make sure you check compatibility of your guide scope with the OAG before buying.
Good luck and clear skies
Wolfgang
Helpful Insightful Respectful
I‘m missing the fundamental question here: what exactly is wrong with the current setup? What effects do you observe that you think need your attention?
Are you dissatisfied with the overall guiding performance? Do you observe elongated stars over the whole field? etc. etc.
It is crucial to first identify the issue.
Björn
Are you dissatisfied with the overall guiding performance? Do you observe elongated stars over the whole field? etc. etc.
It is crucial to first identify the issue.
Björn
Well Written Insightful Respectful Concise Engaging
Retired IT project managers perspective: if it ain't broke, don't fix it. Never touch a working system (.. if there are no striking reasons to do so).
Why bother if you don't have issues with your current guiding?
Have fun with your setup and clear skies
Wolfgang
This. If your guiding is good continue as you were.
iOptron CEM60 - do people like it?
Hi all, I'm looking to upgrade my mount and I have my eye on the iOptron CEM60 with encoders. Coincidentally or not I've seen some outstanding pictures presented here using this mount. The heaviest scope I'm likely to use it for is an 8&q...
Discusses guide scope versus OAG for astrophotography, relevant to your auto-guiding question.
What do I do to upgrade my guiding performance?
Setup: 1000mm F/5 newtonian orion deluxe 50mm guidescope asi120mm-mini guide cam asi533mc pro ASIair Mini AVX mount My current guidescope gives a total guiding accuracy of around 1-2 arcseconds, which is okay, but enough for my liking; sometimes I ha...
Directly addresses guiding performance optimization with similar equipment setup.