EQ mount for low latitudes like Singapore and Malaysia?

Nigel_Choy · Post by **Nigel_Choy** » Mon Feb 14, 2011 3:56 pm

I starting out astrohphotography. But before i start i need help buying an EQ mount. I dont seem to find any mount that reach latitudes like 3. Besides, Astro Physics (the mounts is overkill, To expensive) , and vixen?. I really like the Orion Atlas/EQ6 pro.

Do you think is possible for The atlas mount to reach latitudes of 3?

orly_andico · Post by **orly_andico** » Mon Feb 14, 2011 3:58 pm

kochu has an Atlas. so yes it can. like i mentioned in the CN thread, all the vixens can reach zero latitude, with the half-pier.

Nigel_Choy · Post by **Nigel_Choy** » Mon Feb 14, 2011 4:08 pm

I wrote on CN about the Vixen Sphinx mounts. They said its not good for Astrophotography. but its great for visual

orly_andico · Post by **orly_andico** » Mon Feb 14, 2011 4:29 pm

Yes but there are other Vixen mounts, namely the Great Polaris and GP D2. I'm using a Great Polaris that I bought really cheap on ebay.. I measured the PE at 21 arc-seconds total (+9/-12) which is pretty OK... there are Tak EM-200's with that level of PE.

Basically the GP and GP-D2 are great mounts for astrophotography so long as your payload requirements are not high -- e.g. for a GP, don't go above 4 kg and for the GP-D2 don't go above 5-6 kg.

timatworksg · Post by **timatworksg** » Mon Feb 14, 2011 7:15 pm

Sadly, most EQ mounts don't make themselves usefull for us and others who live near or on the equator! The Orion Atlas and Sirius mounts can be used but with some modifications. I have the Sirius EQ-G which has the mount head on in reverse within the cradle that pivots the altitude. The back end of these mounts have more space which allows the mount head to go down lower, in fact level to 0degrees.
Astrobargains (Joo Beng) has his Orion mounts modded this way. Some mounts allow you to remove a stopper and like what I had to do for Wee Ern on his GPD2, remove a stopper nut to allow the head to go down further!
Hard to figure which works as manufacturer's don't say much about the altitude span...so it's best to ask around here and get some feedback on how many of us have resolved this issue!
As Orly has mentioned, keep within the payload. It's all a balancing act. Less you have sticking out the more stable things will be. A long refractor, though way within payload limits, is more likely to vibrate (due to it's length) than a payload limit shorter one! Don't forget to not only take into account the scopes weight, but also any extensions, CCD cam/DSLR, guider scope, etc etc which bears down on the payload of the mount.

Post by **weixing** » Mon Feb 14, 2011 10:46 pm

Hi,
Vixen GP/GPD mount can reach 0 degree even if you don't use the half-pier, but you'll need to relocate the North-peg on the tripod to between the tripod legs and use small diameter counter-weight, like the original Vixen counter-weight.

For Astrophotography, Vixen GPD will be better than Vixen GP for the following reasons:
1) mount built is better (better tracking performance)
2) higher load capacity
3) the body is longer when install the illuminator, so can clear the tripod legs easier when you relocate the North-peg between the legs, and
4) Azimuth Adjustment Knob is bigger and easier to adjust (for drift alignment).

About loading consideration for Astrophotography, the thumb of rule is 70% of the maximum loading capacity of the mount. Also, if your scope or lens had a focal length longer than 1000mm, guiding is recommended for long exposure... For beginner, I'll recommend a scope or lens with focal length shorter than 800mm... unless you already had a scope.

Just my S$0.02.

Have a nice day.

orly_andico · Post by **orly_andico** » Tue Feb 15, 2011 12:58 am

hi weixing,

thanks for that info! i didn't know GP/GP-D2 would go to zero latitude even with no pier.

btw on my GP tripod hub, the north peg is not removable (it's not a bolt but part of the casting). how to relocate? cut it off and drill a hole for a bolt to replace it?

the reason i gave the loading numbers above is that in my personal experience (with a GP, which has a 15lb capacity), a 9lb load (Orion 100ED) is too much. I mean yes it is stable, but already subject to wind loading, Well the 100ED is long, that works against it too.

my best experience is with the 2kg ZS70 (maybe 2.5kg with DSLR). very stable, very short (336mm FL). i still need guiding though although probably this is partly due to my not-so-good polar alignment. that's already a drift alignment though.

orly_andico · Post by **orly_andico** » Tue Feb 15, 2011 2:38 am

based on this old thread...

http://www.singastro.org/viewtopic.php?t=4738

Atlas can go to zero latitude without need for a half pier. Doh!

rlow · Post by **rlow** » Tue Feb 15, 2011 8:02 am

Yes, my EQ6's original counterweights at max. position can move and clear between the tripod legs without the need of a half-pier. But just barely, with 1mm to spare. If you are using a long tube (like my 6" f/8 refractor) then the issue is that the star diagonal will hit the tripod legs, hence I built a half-pier for that.