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Driving a C.9.25 Evolution on wedge RA only

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#1 starspangled

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Posted 18 July 2021 - 08:31 PM

Does anyone know how to drive a 9.25"Evolution in RA only at Sidereal rate , so I can do a drift alignment ( I cannot see the pole ).  The Sky Safari Pro app and Sky Portal app in help scree  both refer to an `drive in RA only " option for drive speed type ,  but in both apps I only have an OFF Sidereal and Lunar rate option . To do a drift alignment I don't want the mount driving Dec. I have tried all the alignment options from both Android apps and hand paddle , and I cant get the within 1 degree of the pole .

 

On a side note I realise this mount is not going to be any good for imaging other than short focal length camera lenses , as I measure an orthogonality error of about 0.5 degree between the fork and the tube in its Vixen style dovetail mount , and that's when its unloaded by the scope being tilted over when on the wedge . So this error is going to vary depending on the position of the single fork in relation to gravity .



#2 Medic002

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Posted 18 July 2021 - 09:47 PM

have u tried the all star polar alignment in the celestron hand control? u can do polar alignment on any star after u do a 2 star alignment. u can connect a laptop to the mount through handcontrol if u want to use cpwi program on laptop instead of using handcontrol also. i have no view of ncp either and my asiair gives me problems most nights trying to use it's polar alignment so i started using cpwi and all star polar alignment to get polar aligned then use my asiair to capture subs. phd2 also has a drift polar alignment so u might want to take a look there also on any star.



#3 starspangled

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Posted 20 July 2021 - 06:17 PM

Thanks Medic . I'll have a look at CPWI.   I've tried all the wedge alignment routines on the hand paddle and apps but just can't get very good I guess because of the fork flexure and play in the motor/ encoders .



#4 Medic002

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Posted 20 July 2021 - 08:07 PM

it might have a lot to do with the wedge. the smaller wedges that are used with the evolution mounts are not very sturdy from what i understand u need the celestron hd wedge to get a good polar alignment for long exposures but a friend of mine uses a double fork mount and the hd wedge and gets great polar alignment. I think he says he can take 2 min subs without guiding but I am not sure on that. I think the cpwi polar alignment with work for u though just to get a polar alignment. I am not positive that u can do a drift alignment without being able to adjust for dec corrections on the phd2 program. You do have a wedge though so you should be able to do dec corrections. I have not tried phd2 myself but I see it mentioned alot from people using drift alignments so u might just want to investigate that a little. Anyway I hope the cpwi polar alignment works for you.  Here is a link for a good video on how he does the polar alignment. He has lot of good videos. You will want to use the sidereal option also for guiding with stars. The lunar is for guiding with the moon which moves slower than most stars.

 

https://www.youtube....h?v=diM2-oBYI3A


Edited by Medic002, 20 July 2021 - 08:29 PM.

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#5 starspangled

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Posted 26 July 2021 - 09:49 PM

Thanks ill check the video . I 'm not interested in PHD just yet . Just want to polar align so it tracks well in RA  for unguided 1 minute exposures with a piggy back 200mm lens .

 

Still haven't found any way to just drive the mount in RA old school.

 

I have the HD wedge , but the tube sags by about 0.3 degree depending on where the single fork is aligned in RA and it is out of parallel by about 0.5 degree anyway when it is in the Vixen bar dovetail mount . All a bit average really .

 

PS is there some time line for editing posts here ?   I went back to edit post #1 in this thread and there is no edit button other than the one I am typing here .


Edited by starspangled, 26 July 2021 - 09:51 PM.


#6 Clouzot

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Posted 28 July 2021 - 09:24 AM

A guess: try and align on a single star. That way you’re sure the mount model is kept to a minimum, and it won’t attempt to correct for polar misalignment by tracking on RA+Dec
I can’t remember if it’s even possible with the handset, but definitely so with CPWI
(I then drift align with PHD2)


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