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CG4 for astrophography

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6 replies to this topic

#1 jaimac

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Posted 13 August 2020 - 09:40 PM

I have a CG4 mount which is rated for 20 lbs. I am not sure if it is inclusive of counter weight which is 11 lbs. What is the maximum weight I can put on the mount to do astrophotography? I will probably take pictures without guiding. The mount seems to be tracking well for few mins with the current WO 72mm setup. 



#2 terry59

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Posted 13 August 2020 - 09:56 PM

I put about 10 lbs or so on mine. You can mod the hand controller for autoguiding


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#3 sunnyday

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Posted 13 August 2020 - 10:16 PM

I put 15 and more sometimes on mine, and the counterweight does not count for the maximum weight.


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#4 chummee

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Posted 13 August 2020 - 10:33 PM

The payload rating usually doesn't include the counter weights. But the rating is arbitrary and varies with manufacturers. Some manufacturers rate it for visual, some for photography. Celestron's payload rating is based on how much the saddle can handle. So, don't think of payload in absolute terms. There are other factors to consider as well, e.g. the strength of the tripod and the length of the scope. I have an eq32 and a cg4, which are identical, except that the eq32 has a weaker aluminum tripod. The eq32 can't handle my 150mm mak cass but my cg4 manages it pretty well.

I'd say trying things out is the best answer to your question.


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#5 John Carlini

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Posted 13 August 2020 - 11:32 PM

Most astrophotographers will say the general rule is to use about 50% of the recommended visual payload. So, a CG-4 rated at 20-lbs visual load should be able to handle a 10-lb load for astrophotography. However, this is just a guideline and not a hard fast rule. I use my CG-4 with a 12-13 lb load and do fairly well with astrophotography tracking. Proper balance and alignment really help. A heavy duty tripod or a pier also helps. Counterweights aren't included in the Celestron CG-4 20-lb weight limit.


Edited by John Carlini, 13 August 2020 - 11:33 PM.

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#6 Ed D

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Posted 14 August 2020 - 08:39 AM

For unguided deep space imaging your WO 72mm will be fine on the CG-4.  I have used an AT72ED and DSLR on my CG-4 and have had good results.  The key is to take your time and set your equipment up as precisely as possible.  I polar align using the drift method and adjust the motor speed as precisely as possible, both using a crosshair eyepiece.  I also balance the weight so there is a slight bit of load on the gears in RA - it doesn't have to be much.  This helps keep the tracking smooth and free of any jerky motions.

 

Solar Eclipse 1.jpg

Imaging solar eclipse 2017.  Eclipse observed on laptop screen, box used as sun shade.

 

This is a pic of my equipment.  Early on I found the 9V battery gave inconsistent motor speed - internal warming varying resistance and output power - and battery life was way too short.  I soldered a wire lead and snap cap to use with a six AA cell holder, seen velcroed to the tripod spreader.  The difference was night and day.  Another mod was to slip a small grommet over the motor speed control shaft to make it a larger diameter, giving me a better feel and more precision.  If I need to remove the motor cover I simply slip off the grommet.

 

The CG-4 is not a computer driven high tech mount, but it is certainly very capable provided you take the time to set it up as precise as possible.

 

Ed D


Edited by Ed D, 14 August 2020 - 08:47 AM.

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#7 zxx

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Posted 14 August 2020 - 12:26 PM

I use my ED80 with my CG-4 with the guide port mod, The mount will guide as well as the AVX  ( or better ) from what I have seen.

 

Capture eq3=cg4.PNG


Edited by zxx, 14 August 2020 - 12:27 PM.

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