3 replies to this topic

[Yomamma]

I've got a CEM120 on order and given the specs on the mount was wondering if the mount PPEC with tracking would give you similar results to using PHD2 guiding, possibly for shorter exposures like 60s - 90s?

 

I'll have a 12" SCT with a little over 2400mm focal length and wanted to try and shoot at the native f/ratio of f/8.  I know guiding at longer FL can be a challenge and was thinking this might work for shorter exposures.

 

Has any CEM120 owner tried this?

 

Thanks

[Spaceman 56]

I am not an expert but I have a CEM-120.

 

PPEC will correct for RA variations which are long term in nature. PHD2 will correct for DEC and RA variations which are short term in nature.

 

at 2400mm focal length I think you will need to guide. But if the PA was absolutely spot on, and  PPEC was enabled, I feel you could try 60 second exposures without guiding, and see what comes.

 

I actually shot some 900 second test shots, with my CEM-120 when I got it, and they actually looked ok, but that was shooting with a 530mm Takahashi, and the short focal length is forgiving. lately I shoot at 1500mm with an RC and guiding is necessary. 

 

hope this helps. 

[Yomamma]

I am not an expert but I have a CEM-120.

 

PPEC will correct for RA variations which are long term in nature. PHD2 will correct for DEC and RA variations which are short term in nature.

 

at 2400mm focal length I think you will need to guide. But if the PA was absolutely spot on, and  PPEC was enabled, I feel you could try 60 second exposures without guiding, and see what comes.

 

I actually shot some 900 second test shots, with my CEM-120 when I got it, and they actually looked ok, but that was shooting with a 530mm Takahashi, and the short focal length is forgiving. lately I shoot at 1500mm with an RC and guiding is necessary. 

 

hope this helps. 

I use a Polemaster for PA and I had a CEM40 that I made a Polemast adapter for and the 120 looks similar so I am sure I can make one for it.  I can usually get <1 min PA with the Polemaster that is why I figured it might work here.  One reason the 120 is so stable is that it is heavy, like the EQ6R Pro, and will probably hold it's PA pretty well.

[Hillbrad]

I have a Cem120 with a 16” SCT mounted on it. Its focal length is 3100mm and it guides nicely every night as long as it’s not too windy. I have not tried turning off phd2 and using the mounts PPEC… but I know my phd2 is usually working pretty hard with the RA guiding at that focal length. Is there any reason why you wouldn’t want to guide?

Brad