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Mount Payload and EAA

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#1 Stargazer3236



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Posted 16 February 2019 - 12:01 PM

An interesting thought came to me when reading the forum about Ultrastar and ZWO ASI294MC cameras.


We take for granted that there is a payload limit on any kind of mount that we need to respect in order to do either EAA or AP. It seems that we are told to not exceed the 1/2 to 2/3 rule about payloads on our respective mounts so that we do not ruin our chances of capturing any DSO's in the camera sensors and not be affected by whether or not the mount can handle the weight to get a good image of the particular DSO in question. In AP, that would be a crucial step in avoiding the shake of a mount, with an overloaded mount and the camera trying to capture that DSO for minutes or hours.


In EAA, since we are taking many subs of 2, 4, 8 or 15 seconds, does the mount payload rules of 1/2 to 2/3 apply to the payload limit? Unless you are prone to doing EAA in very windy conditions, most of us avoid windy nights. Also unless you live in an earthquake ravaged area, you will not encounter any ground shaking akin to shaking your mount while EAA imaging. We all take the time to level our mounts (EQ), polar align and balance our scopes so we get nearly flawless images captured during EAA.


I say we don't need to be so cautious about payload limits with our mounts and OTA and accessories because we don't do AP imaging. My ZEQ25 mount has a payload limit of 27 lbs. However, I think I have exceeded the 1/2 rule on Payload because sometimes I overload my C8 OTA with my AT60ED piggybacked on the top of the OTA. with the arrangement of my C8, with a vixen dovetail on the bottom and a losmandy dovetail on the top to accommodate the AT60ED, plus the mounting rail and tube rings of the AT60 and the addition of a losmandy accessory so I can mount the AT60 onto the losmandy rail of the C8, I believe I am overloading my mount 1/2 payload rule and possibly exceeding the 2/3 rule.


My C8 weight is 12.5 lbs and with the added losmandy dovetail on top, I believe it is now closer to 14 lbs. My AT60ED rig, ADM tube rings and losmandy female adapter, that weighs another 4-5lbs, not including a reducer or visual back or camera. Add it all up and I think I am pushing 22 lbs, well over the 1/2 rule and a little bit over the 2/3 rule of payload weight and I still manage to get very good results with my EAA imaging and screen capture detail!


Sometimes, though, I just put on my AT60ED rig or the C8 onto the ZEQ25 mount. With the AT60ED, the total weight of scope, tube rings, ADM losmandy dovetail, reducer, visual back and camera comes out to 10 lbs or so, far below the 2/3 rule and just a bit under the 1/2 rule. The C8 on the other hand comes to around 16-17 lbs, with the OTA, reducer, visual back, filters, and camera so I am nearing the 2/3 rule.


Anyway, my point is that in EAA, we really do not have to limit ourselves to the payload limits of our mounts because we are not doing AP for many dozens of minutes or hours. We are starting and stopping are image exposures after a few measly seconds. And we are stacking those exposures to form our image.  And unless you are a glutton for punishment and like to do EAA captures in gusty winds or earthquake prone areas, then we have nothing to worry about weight wise. Just put a few vibration suppression pads under your tripod legs and all will be good.


#2 sg6



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Posted 16 February 2019 - 12:46 PM

When it comes to loading I would say immaterial of the use do not push it all the time, even any of the time. When you get in your car do you automatically add the weight, as say sand bags, of 4 other people and a few luggage cases to bring it up to the maximum loading the manufacturer says it can carry?


I may be foolishly presuming you do not, so why do it with a mount?

#3 OleCuss



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Posted 16 February 2019 - 09:09 PM

I'd say that a bunch of us doing OAP violate the "1/2 payload weight rating rule" frequently or constantly.  For that matter, a bunch of us use A-Z mounts which were not at all designed for AP of any sort.  We can do a lot of good stuff despite ignoring what is done in CAP (Conventional AP).


However, if you have a reasonable option of using a better mount, I'd highly recommend doing so.  When using marginal mounts it is not at all uncommon for folk to have at least a modest number of messed-up subs which are either not stacked or which degrade your image somewhat.  Precision is our friend.


Better may not be essential, but it generally makes the experience better and gives you more options.

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